Physical and Hydrologic Properties of Water-Bearing Deposits in Subsiding Areas In Central California By A. I. JOHNSON, R. P. MOSTON, and D. A. MORRIS MECHANICS OF AQUIFER SYSTEMS GEOLOGICAL SURVEY PROFESSIONAL PAPER 497-A Results oj laboratory tests on cores from deposits that in part are compacting, owing to artesian-head decline UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1968UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402FOREWORD The problem and the need for study The land surface is sinking in several areas of intensive ground-water withdrawal in California. (See fig. 1.) Subsidence of the land surface in the central part of the Santa Clara Valley, at the south end of San Francisco Bay, has been known since the early thirties; an area of about 250 square miles has been subsiding, and by 1963 maximum subsidence of 11 feet had occurred in San Jose. In the San Joaquin Valley also, subsidence has been recognized since the middle thirties. About 3,000 square miles, or 30 percent of the valley floor, is subsiding. Subsidence of many feet has been observed in three principal areas in the San Joaquin Valley. Between Los Banos and Kettleman City, on the central west side of the valley, an area of 1,200 square miles has subsided 2 feet or more, and by 1963 maximum subsidence was 23 feet a few miles west of Mendota. In the Tulare-Wasco area, on the southeast side of the valley, subsidence of more than 1 foot had affected at least 800 square miles by 1962, and maximum subsidence was 12 feet. In the Arvin-Maricopa area, at the south end of the. valley, subsidence h> occurred in about 450 square miles and was as much as 6 feet by 1962. The areas of subsidence in the San Joaquin Valley are in irrigated lands in part traversed by canals of large capacity and low gradient ; additional major trunkline aqueducts are planned or are under construction. Where the rate of subsidence is large—a few tenths of a foot to a foot per year—it poses serious problems in the construction and maintenance of these costly structures and also of local water-distribution systems, sewerage lines, and drainage and flood-control works. In addition, it has caused many well-casing failures as a result of compaction of the sediments and compression of the casings. Inter-Agency Committee planning By 1954, preliminary planning for the California Aqueduct and the San Luis project canal of the U.S. Bureau of Reclamation emphasized the critical need for information on the extent, rates, causes, and possible measures for control or alleviation of land subsidence. As a result, concerned Federal and State agencies formed the Inter-Agency Committee on Land Subsidence in the San Joaquin Valley in December 1954, to plan and coordinate subsidence investigations. The actively participating members of the Committee included the following: three Federal agencies—the Bureau of Reclamation and the Geological Survey in the Department of the Interior, and the Coast and Geodetic Survey of the Department of Commerce; two State agencies—the California Department of Water Resources and the Division of Highways, Department of Public Works; and two universities—the University of California at Davis and Stanford University. The first major action of the Committee was the preparation of a proposed program of investigation (Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, 1955). Cooperative program with the State of California As one result of the interagency planning, an intensive investigation of land subsidence in the San Joaquin Valley was begun by the Geological Survey in 1956, in financial cooperation with the California Department of Water Resources. The Geological Survey participation in the interagency committee work has been carried on in conjunction with this cooperative program. The objectives of the cooperative program on land subsidence in the San Joaquin Valley are as follows: 1. To obtain vertical control on the land surface adequate to define the extent, rate, and magnitude of subsidence. The vertical control program is a companion project of the U.S. inXV FOREWORD Coast and Geodetic Survey, which that agency has carried on since 1960 in financial cooperation with the California Department of Water Resources. 2. To determine causes of the subsidence, the relative magnitude attributable to the different causes, and also the depth range within which compaction causing subsidence is occurring. 3. To furnish criteria for estimating the rates and amounts of subsidence that might occur under assumed hydrologic change; to suggest methods for decreasing or alleviating subsidence; and to determine whether any part of the subsidence is reversible and, if so, to what extent. A progress report prepared in 1958 (Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, 1958) described the major subsidence areas in the San Joaquin Valley and reported on the methods of investigation and preliminary results. The report, prepared chiefly by the Geological Survey, resulted from the cooperative program of the Geological Survey and the field activities of the Bureau of Reclamation, Coast and Geodetic Survey, California De-i partment of Water Resources and Division of Highways, and the University of California at ]| Davis. The report identified two types of subsidence that occur in the San Joaquin Valley. Most of the subsidence in the three areas is being caused by compaction of artesian aquifer systems, owing to withdrawal of ground water from confined deposits and the resulting decline in artesian head. Locally, on the western and southern flanks of the valley, the second type of subsidence is caused by near-surface compaction of moisture-deficient alluvial-fan deposits above the water table, after initial wetting by percolating irrigation water. This second type of subsidence produces extensive settling and cracking of the land surface along ditches, and irregular undulating topography in irrigated areas underlain by the susceptible deposits. Nearsurface subsidence of 10 feet or more has been produced in wetted test plots and in irrigated fields. Near-surface subsidence may produce abrupt changes of several feet in the land-surface altitude in short distances. Hence, it creates serious problems in construction and maintenance of water-transport systems, highways, pipelines, electric transmission towers, and other engineering structures, and in farming. In the Los Banos-Kettleman City area, a dual-function canal to serve the San Luis project area of the Bureau of Reclamation and to transport water of the California Aqueduct south to Kettleman City is (1964) under construction. It has a design capacity of 13,100 cfs (cubic feet per second) at its head—at San Luis Dam west of Los Banos—which decreases to 7,000 cfs at Kettleman City. This dual-function canal will cross about 70 miles of subsiding ground in the Los Banos-Kettleman City area. All of this 70-mile reach is subsiding because of artesian-head decline, and at least 20 miles is subject to near-surface subsidence as well. In the reach susceptible to near-surface subsidence, the canal alinement is being prewetted for many months to precompact the deposits above the water table before the great canal is built. The California Aqueduct, which will transport water south from Kettleman City to Kern County and to the Los Angeles area, will be constructed through several tens of miles of subsiding land in the Arvin-Maricopa area. Here, .also, the subsidence due to artesian-head decline is the more extensive, but near-surface subsidence also is a serious problem. The total cost of precompaction of the reach susceptible to near-surface subsidence south of Kettleman City— about 55 miles—is estimated by the California Department of Water Resources to be $20 million.1 The subsidence in the Los Banos-Kettleman City and Tulare-Wasco areas due to artesian-head decline was described briefly by Poland and Davis (1956). The extent and character of subsidence of near-surface deposits in the Los Banos-Kettleman City area have been summarized by Lofgren (1960); the geology of the alluvial fans and the causes and mechanics of the near-surface subsidence have been described by Bull (1961, 1964). The extent and magnitude of subsidence in the Arvin-Maricopa area as of 1962 have been summarized by Lofgren 1 Lucas, C. V., and Lombard, F. J., 1964, Land subsidence along the California Aqueduct as related to environment: California Dept. Water Resources; prepared for Am. Soc. Civil Engineers Environmental Eng. Conf., Salt Lake City, Utah, 17 p.FOREWORD V (1963). The cooperative land-subsidence investigations are continuing, and major reports are in preparation on the Los Banos-Kettleman City, Tulare-Wasco, and Arvin-Maricopa areas. Geological Survey research on mechanics oj aquifer systems The areas of active and substantial land subsidence in the San Joaquin and Santa Clara Valleys offer an unexcelled opportunity to study compaction of sediments in response to change in effective stress. Not only are the aquifer systems compacting at a rate that is susceptible to field measurement, but, equally important, the forces causing this compaction can be determined quantitatively in much of the subsiding area. For this reason, the Geological Survey also began in 1956 a federally financed research project directed toward determining the principles controlling the deformation (compaction or expansion) of aquifer systems resulting from change in grain-to-grain load, caused chiefly by change in internal fluid pressure. One of the principal objectives of this research project is to appraise the changes that occur in the hydraulic characteristics of compactible aquifer systems, particularly the storage characteristics, as the systems compact under increased effective stress, especially under cyclic application of stress. In the San Joaquin Valley, the needs of the cooperative land-subsidence studies and of the Federal research on mechanics of aquifer deformation with respect to field and laboratory data are in large part common and the findings are mutually beneficial. In the Santa Clara Valley, the study of land subsidence and aquifer deformation is entirely a part of the Federal research program. The principal elements of the program to sup'ply the needs of both the Federal research and of the cooperative program in the San Joaquin Valley are summarized as follows: 1. Measure magnitude and rate of compaction (or expansion) occurring in the aquifer systems, by means of compaction-recorder installations. 2. Measure changes in hydrostatic head areally and also in or near compaction-recorder wells, for comparison with observed aquifer deformation. 3. Drill core holes into or through the compacting aquifer systems, obtain core and geophys- ical logs, and preserve selected core samples for laboratory tests and study. 4. Make laboratory tests of core samples to determine their physical and hydrologic proper- ties and consolidation and rebound characteristics. 5. Study the mineralogy and petrography of core samples with special reference to environ- ment of deposition, and determine the mineralogy of the fine-grained clay elements. 6. Utilize the laboratory-test results and the observed change in hydrostatic head to compute compaction of the aquifer system, on the basis of soil-mechanics theory. 7. Compare land subsidence, as observed from changes in elevation of bench marks determined by precise leveling, with the measured compaction of the aquifer system and with computed compaction. 8. Make aquifer tests to obtain coefficients of storage and transmissibility, and, where possible, make simultaneous measurements of aquifer-system compaction and (or) land subsidence. 9. Make laboratory tests simulating the field conditions in compacting aquifer systems, to study pore-pressure decay and compaction of clayey sediments consolidated under controlled conditions. 10. Where control is adequate, evaluate the geologic and hydrologic factors that jointly deter- mine the magnitude and rate of compaction of the aquifer system and, insofar as practicable, relate the areal variation in subsidence per unit of head decline to the controlling geologic parameters. 11. Assemble and review literature on land subsidence due to fluid withdrawal and on methods used in investigating such phenomena, and prepare a report on subsidence due to fluid withdrawal in areas throughout the world. As one of the primary elements of the field program, eight core holes ranging in depth from 760 to 2,200 feet were drilled. Four of these are in the Los Banos-Kettleman City area, two in the Tulare-Wasco area, and two in the Santa Clara Valley. These multiple-purpose core holes were drilled: (1) to obtain cores for making laboratory tests of physical and hydrologicVI FOREWORD properties and consolidation and rebound characteristics of selected core samples, (2) to obtain core samples for laboratory study of petrography and clay-mineral assemblages, (3) to obtain electric logs, caliper logs, and lithologic descriptions for study of the geology of the aquifer systems, and (4) to install compaction-measuring equipment. Core holes in the San Joaquin Valley, which were drilled as part of the Inter-Agency program, were financed chiefly by Geological Survey-State cooperative funds, but the Bureau of Reclamation helped to finance two holes in the Los Banos-Kettleman City area. The Bureau of Reclamation bore all drilling costs for the Oro Loma core hole at the Delta-Mendota Canal. The core holes in the Santa Clara Valley were financed wholly by Geological Survey funds. All eight core holes were drilled in areas of subsidence caused by artesian-head decline. None is in an area affected by near-surface subsidence. The present paper by A. I. Johnson, R. P. Moston, and D. A. Morris on the physical and hydrologic properties of water-bearing deposits in subsiding areas in the San Joaquin and Santa Clara Valleys is the first chapter of a series of major reports resulting from the Geological Survey’s research program on the mechanics of aquifer systems. It presents the results of the laboratory analyses for physical, hydrologic, and engineering properties of core samples from the compacting sediments, as recovered from the eight core holes. The laboratory analyses, being utilized directly in the interpretive reports of the Geological Survey on land subsidence and the compaction of aquifer systems, are chiefly the particle-size distribution, specific gravity and unit weight, porosity and void ratio, and consolidation and rebound tests. Tests of acid-soluble material and gypsum content were made in connection with study of the environment of deposition and diagenesis of these sediments. The tests of Atterberg limits and indices are not being utilized quantitatively in the current studies but were made at relatively small additional cost to provide supplementary data. The Atterberg limits and indices, together with the particle-size analyses, illustrate the effect of the percentage of clay-size particles in controlling engineering properties and furnish at least a qualitative index to the compressibility characteristics of the sediments. Furthermore, classification of samples in terms of the Unified Soil Classification System, used by the Bureau of Reclamation, the Corps of Engineers, and many other engineering organizations, requires determination or estimation of Atterberg limits. In the Unified Soil Classification System, the liquid limit is used to distinguish between clay of high compressibility and clay of low compressibility. The tests for permeability should be useful for other studies. For example, determination of the permeability of the fine-textured sediments is of use in drainage studies being made by the State in the San Joaquin Valley. Furthermore, the tests comparing permeability parallel and normal to the stratification give some data on the relative ease of movement of water in the two directions, and may be of use in studies of leakage between aquifers. Very little information of this type is available on unconsolidated alluvial deposits; most published comparative data have been on consolidated rocks in oil-reservoir studies. It should be noted, however, that the values for vertical permeability obtained in the variable-head permeameter under no load appear to be considerably higher than values computed from consolidation tests for samples of similar texture. Three probable reasons for the discrepancy are discussed on p. A26 and A27. In addition to the direct application to problems of subsidence and compaction of aquifer systems, the analytical results on the samples from the eight core holes serve a much broader geologic need, because they furnish a substantial body of data on the physical characteristics and hydrologic properties of thick sequences of unconsolidated to semiconsolidated sediments-— chiefly of alluvial origin but derived from contrasting source rocks. Basic data of this scope, for continental deposits spanning thicknesses of 1,000-2,000 feet, are rare. They should be useful in many types of studies—geologic, hydrologic, and engineering—in addition to the specific purposes of the investigations of land subsidence and the compaction of aquifer systems. Several major reports that are products of the Federal research program on mechanics of aquifer systems have been published or approved for publication, as follows:FOREWORD VII Meade, R. H., 1964, Removal of water and rearrangement of particles during the compaction of clayey sediments—review: U.S. Geol. Survey Prof. Paper 497-B, 23 p. ——— 1967, Petrology of sediments underlying areas of land subsidence in central California: U.S. Geol. Survey Prof. Paper 497-C, 83 p. Poland, J. F., and Davis, G. H., Land subsidence due to withdrawal of fluids: Reviews in Engineering Geology, v. 2, Geol. Soc, America (in press). Other major reports in progress are: Compaction of sediments underlying areas of land subsidence in central California (R. H. Meade); geology of compacting sediments in the Los Banos-Kettleman City subsidence area (R. E. Miller, J. H. Green, and G. H. Davis); and land subsidence and aquifer-system compaction in the Santa Clara Valley, Calif. (J. H. Green). A report on principles controlling the deformation of aquifer systems due to change in grain-to-grain load is planned as the concluding chapter of the series. J. F. Poland Research geologistCON TEN TS Foreword_______________________________ Abstract_______________________________ Introduction___________________________ Purpose and scope of report_______ Location and description of areas_ Los Banos-Kettleman City area Tulare-Wasco area_____________ Santa Clara Valley____________ Field sampling____________________ Composite logs of core holes______ Acknowledgments___________________ Methods of laboratory analysis_________ Particle-size distribution________ Permeability______________________ Dry unit weight___________________ Specific gravity of solids________ Porosity and void ratio___________ Moisture content__________________ Atterberg limits__________________ Liquid limit__________________ Plastic limit_________________ Shrinkage limit_______________ Shrinkage factors_________________ Shrinkage ratio_______________ Volumetric and linear shrinkage Atterberg indices_________________ Plasticity index______________ Flow index____________________ Toughness index_______________ Shrinkage index_______________ Page III A1 1 1 2 2 2 6 8 10 10 10 10 11 13 13 13 14 14 14 15 15 15 15 16 16 16 16 16 16 Methods of laboratory analysis—Continued Acid solubility__________________________ Gypsum content___________________________ Consolidation____________________________ Results of laboratory analyses________________ Particle-size distribution_______________ Sediment classification triangles____ Los Banos-Kettleman City area _ Tulare-Wasco area_______________ Santa Clara Valley______________ Statistical measures_________________ Permeability_____________________________ Specific gravity, unit weight, and porosity Moisture content_________________________ Atterberg limits and indices_____________ Liquid limit_________________________ Plastic limit________________________ Plasticity index_____________________ Shrinkage limit______________________ Volumetric shrinkage_________________ Toughness index______________________ Acid solubility__________________________ Gypsum content___________________________ Consolidation____________________________ Summary of laboratory analyses results by area Los Banos-Kettleman City area___________ Tulare-Wasco area_______________________ Santa Clara Valley__________ ___________ Tabulated statistical data___________________ References___________________________________ Page A16 16 17 18 18 18 20 21 21 21 24 27 30 31 32 32 32 34 35 36 37 37 37 40 40 41 43 45 70 ILLUSTRATIONS [Plates are in separate volume] Plate 1. Composite logs of core holes, Los Banos-Kettleman City area, Tulare-Wasco area, and Santa Clara Valley, central California. 2-9. Graphs of particle-size distribution curves for samples from core holes: 2. Core hole 12/12-16H1, Los Banos-Kettleman City area. 3. Core hole 14/13-1 ID 1, Los Banos-Kettleman City area. 4. Core hole 16/15-34N1, Los Banos-Kettleman City area. 5. Core hole 19/17—22J1, 2, Los Banos-Kettleman City area. 6. Core hole 23/25-16N1, Tulare-Wasco area. 7. Core hole 24/26-36A2, Tulare-Wasco area. 8. Core hole 6S/2W-24C7, Santa Clara Valley. 9. Core hole 7S/1E-16C6, Santa Clara Valley. 10. Mississippi Valley sediment classification triangle. 11. Graphs of consolidation test curves for selected samples from core holes. 12-14. Graphs of physical properties of samples from core holes: 12. Los Banos-Kettleman City area. 13. Tulare-Wasco area. 14. Santa Clara Valley. EC 263-524 0-67—2X CONTENTS Page Figure 1. Map showing principal areas of land subsidence in California due to ground-water withdrawal__________________ A2 2. Map showing land subsidence, 1957-59, and core-hole locations in Los Banos-Kettleman City area________ 3 3. Simplified geologic section through Los Banos-Kettleman City area____________:________________________ 4 4. Map showing land subsidence, 1948-54, and location of core holes in the Tulare-Wasco area____________________ 5 5. Simplified geologic section through Tulare-Wasco area________________________________________________________ 6 6. Map showing land subsidence in the Santa Clara Valley, Calif., 1934-60, and location of core holes___________ 7 7. Photograph of hydraulic press used for obtaining small cores from large cores of unconsolidated sediments. . 11 8. Photograph and diagrams of permeability apparatus___________________________________________________________ 12 9. Graph showing relation of porosity to dry unit weight for various specific gravities of solids______________ 14 10. Graph showing relation of void ratio to porosity____________________________________________________________ 15 11. Diagram of a one-dimensional consolidometer specimen container______________________________________________ 17 12. Graph showing void ratio-load curve, compression index, and preconsolidation load___________________________ 19 13. Diagrams showing sediment classification of samples from core holes in Los Banos-Kettleman City area__ 22 14. Diagrams showing sediment classification for samples from core holes in Tulare-Wasco area, and Santa Clara Valley_______________________________________________________________________________________________ 23 15. Graphs showing range in permeability of samples from core holes_______________________________________ 25 16. Diagrams showing relation between permeability and texture for samples from core holes in Los Banos- Kettleman City area__________________________________________________________________________________ 28 17. Diagrams showing relation between permeability and texture for samples from core holes in Tulare-Wasco area and Santa Clara Valley________________________________________________________________________________ 29 18. Graphs showing effect of clay content on liquid and plastic limits__________________________________________ 33 19. Unified soil-classification plasticity charts for core-hole samples_________________________________________ 34 20-24. Graph showing relation of— 20. Volumetric shrinkage to clay content for samples from core holes_______ ______________________ 36 21. Liquid limit and compression index for samples from core holes________________________________ 39 22. Dry unit weight, porosity, and void ratio to depth for principal sediment classes from core holes in Los Banos-Kettleman City area______________________________________________________________________ 42 23. Dry unit weight, porosity, and void ratio to depth for principal sediment classes from core holes in Tulare-Wasco area__________________________________________________________________________________ 44 24. Dry unit weight, porosity, and void ratio to depth for principal sediment classes from core holes in Santa Clara Valley_________________________________________________________________________________ 46 TABLES Table 1. Identification of core holes_________________________________________________________________________________________ A9 2. Classification of sediment samples from core holes______________________________________________________________ 20 3. Natural moisture content of sediments from core hole 6S/2W-24C7, Santa Clara County_________________ 30 4. Range in values of consistency__________________________________________________________________________________ 31 5. Physical and hydrologic properties of samples from core holes___________________________________________________ 47 6. Atterberg limits and indices of samples from core holes_________________________________________________________ 55 7. Acid solubility and gypsum content of samples from core holes___________________________________________________ 58 8. Visual classification, Atterberg limits, and specific gravities of samples tested for consolidation------------- 60 9. Consolidation-test summaries____________________________________________________________________________ — 64 10. Summary of selected physical and hydrologic properties for samples grouped by sediment class (Shepard system)________________________________________________________________________________________________________ 67MECHANICS OF AQUIFER SYSTEMS PHYSICAL AND HYDROLOGIC PROPERTIES OF WATER-BEARING DEPOSITS IN SUBSIDING AREAS IN CENTRAL CALIFORNIA By A. I. Johnson, R. P. Moston, and D. A. Morris ABSTRACT Land subsidence in extensive areas of the San Joaquin and Santa Clara Valleys, Calif., is causing serious problems in the construction and maintenance of costly engineering works such as large canals, water-distribution systems, and drainage and flood-control works. The subsidence in the Los Banos-Kettleman City area, the largest area of subsidence in the San Joaquin Valley, is critical with respect to canal construction, because the dual-function canal serving the San Luis project of the Bureau of Reclamation and transporting water for the California Aqueduct of the State is soon to be constructed through that area; the canal will cross about 70 miles of subsiding ground. The Tulare-Wasco area, the second largest area of land subsidence in the San Joaquin Valley, is traversed by the Friant-Kern Canal of the Central Valley Project, which supplies water to several irrigation districts in the subsiding area. Although subsidence has not seriously affected the transportation of surface water, continued or accelerated subsidence could create serious problems. Four core holes, ranging in depth from 1,000 to 2,200 feet, were drilled in 1957 and 1958 along the axis of the subsidence trough in the Los Banos-Kettleman City area in western Fresno County, at sites where subsidence rates ranged from 0.2 to 1 foot per year. These core holes were drilled about to the base of the water-bearing deposits. Two core holes, 760 and 2,200 feet in depth, were drilled in 1958 and 1959 in areas of major subsidence in southern Tulare County, where the rate of subsidence is as much as 0.7 foot per year. Two core holes were drilled in the Santa Clara Valley in 1960 along the axis of the subsidence trough, where subsidence rates were as great as 0.4 foot per year. These core holes were drilled to a depth of about 1,000 feet to span all the deposits tapped by water wells. All eight of these holes were cored through most of their depth to obtain samples for laboratory analysis of physical, hydrologic, and engineering properties. As part of the study of subsidence and of principles controlling the deformation (compaction or expansion) of aquifer systems due to change in artesian pressure, and hence in grain-to-grain load, selected samples from the core holes were tested in the Geological Survey’s Hydrologic Laboratory and the Bureau of Reclamation’s Earth Laboratory, both at Denver, Colo. “Undisturbed” samples from the core holes were analyzed for particle-size distribution, permeability, specific gravity, dry unit weight, porosity, Atterberg limits, consolidation, acid solubility, and gypsum content. The sediments recovered from the core holes in the Los Banos-Kettleman City area and the Santa Clara Valley were predominantly fine textured and primarily of the clayey-silt or silty-clay types by the Shepard classification system. The sediments recovered in the Tulare-Wasco area were predominantly medium-textured and primarily of the silty-sand or sand-silt-clay types by the Shepard system. Recovery of coarse materials (sands and gravels) was very poor, and these materials therefore are not adequately represented or described in this report. Laboratory data in tabular and graphic form are presented, laboratory analysis methods are described, and interrelationships of some of the physical and hydrologic properties are shown. Reference data required for future interpretive reports on subsidence research are furnished. INTRODUCTION PURPOSE AND SCOPE OF REPORT To provide information on the physical, hydrologic, and engineering properties of the sediments that are compacting in the Los Banos-Kettleman City area (fig. 1) four core holes were drilled along the axis of the subsidence trough, and samples were taken for laboratory testing. Selected cores from three of these holes were tested in the Geological Survey’s Hydrologic Laboratory and in the Bureau of Reclamation’s Earth Laboratory, both at Denver, Colo. Selected samples from the fourth core hole, 12/12-16H1, were tested only by the Bureau of Reclamation. In all, 305 core samples were analyzed by the Geological Survey and 64 core samples were analyzed by the Bureau of Reclamation. Results of these analyses were made available in 1962 (Johnson and Morris, 1962a). In the Tulare-Wasco area, two core holes were drilled in areas of maximum subsidence, and selected samples were taken for analysis in the Hydrologic Laboratory and in the Earth Laboratory. A total of 157 core samples were analyzed by the Geological Survey and 22 core samples were analyzed by the Bureau of Reclamation. In the Santa Clara Valley, two core holes were drilled along the axis of the subsidence trough, and selected samples were taken for analysis in the Hydrologic Laboratory and in the Earth Laboratory. In all, 87 core samples were analyzed by the Geological Survey and 21 core samples were analyzed by the Bureau of Reclamation. AlA2 MECHANICS OF AQUIFER SYSTEMS Figure 1.—Principal areas of land subsidence in California due to ground-water withdrawal. Compiled by R. E. Miller. This report describes the methods used in the laboratory and presents the results of the laboratory tests in tabular and graphic form. Certain of the results—specifically, the particle-size analyses, specific gravity and unit weight, porosity and void ratio, and the consolidation tests—are applicable directly to the studies of land subsidence and the compaction of the aquifer systems. In addition, the test results serve a broad geologic need by furnishing a substantial body of data on the physical characteristics and hydrologic properties of a thick sequence of unconsolidated to semiconsolidated sediments of alluvial and lacustrine origin. Basic data of this scope, for continental deposits spanning thicknesses of 1,000 to 2,000 feet, are rare and should be useful in many types of studies—geologic, hydrologic, and engineering—in addition to the specific purposes of the investigations of land subsidence and the compaction of aquifer systems. The laboratory analyses by the Geological Survey were made under the direction of A. I. Johnson, chief of the Hydrologic Laboratory, by D. A.Morris, Eugene Shuter, A. C. Doyle, C. R. Jones, I. M. Bloomgren, W. H. Lohman, R. P. Moston, W. E. Teasdale, A. H. Ludwig, N. N. Yabe, E. S. Chun, J. D. Orner, W. N. Lawless, R. E. Taylor, S. F. Versaw, R. A. Speirer, and W. N. Lockwood. Laboratory analyses by the Bureau of Reclamation were made under the direction of W. G. Holtz, chief of the Earth Laboratory Branch, and H. J. Gibbs, head of Special Investigations and Research Section. LOCATION AND DESCRIPTION OF AREAS LOS BANOS-KETTLEMAN CITY AREA The largest of the subsiding areas in the San Joaquin Valley is the Los Banos-Kettleman City area in Merced, Fresno, and Kings Counties (fig. 2). Subsidence of 2 feet or more has occurred throughout approximately 1,200 square miles of this area—the average subsidence has been in excess of 6 feet. Subsidence of 20 feet has occurred during approximately 30 years in small parts of the area west of Mendota. The water-bearing sediments have been described by Davis and Poland (1957, p. 420-430), by the Inter-Agency Committee on Land Subsidence in the San Joaquin Valley (1958, p. 116-138), and in detail by Miller and others (report on geology of compacting sediments, manuscript in preparation). These reports point out that the fresh-water-bearing sediments in the Los Banos-Kettleman City area are primarily unconsolidated to semiconsolidated continental deposits 1,000-3,500 feet thick. The sediments are of Pliocene, Pleistocene, and Recent age, underlain by semiconsolidated to consolidated brackish-water and marine deposits of Pliocene and greater age that contain saline water (fig. 3). The fresh-water-bearing deposits can be divided into three units: (1) An upper unit, consisting of clay, silt, and sand, which includes the post-Tulare alluvial deposits and the upper part of the Tulare Formation and extends from the land surface to depths ranging from 200 to 800 feet; (2) a middle unit of relatively impervious diatomaceous clay to clayey silt of lacustrine origin, the Corcoran Clay Member of the Tulare Formation, which, in most of the area, has a thickness of 20-120 feet; and (3) a lower unit of clay, silt, and sand, in part of lacustrine origin, which includes the lower part of the Tulare Formation and, locally, parts of the San Joaquin and Etchegoin Formations of Pliocene age. This lower unit is commonly 600-1,500 feet thick but locally is as much as 3,000 feet thick. The Corcoran Clay Member not only serves as a distinctive geologic marker bed but also as the principal confining bed of the artesian aquifers in the San Joaquin Valley. TULARE-WASCO AREA The Tulare-Wasco area is in the southeastern part of the San Joaquin Valley. It centers in Tulare County but extends southward into Kern County and westward into Kings County (fig. 4). Delano and Tulare are the largest cities within the Tulare-Wasco subsidence area, which is roughly bisected by U.S. HighwayPROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A3 Figure 2.—Land subsidence 1957-59 and core-hole locations in the Los Banos-Kettleman City area.A4 MECHANICS OF AQUIFER SYSTEMS Figure 3.—Simplified geologic section through core holes in the Los Banos-Kettleman City area. 99. The land is intensively developed agriculturally and much of it is irrigated by ground water. Approximately 500 square miles, or about one-third of the total, subsided more than 1 foot during the 6-year period from 1948 to 1954, owing to large declines in ground-water levels (Poland and Davis, 1956). The Tulare-Wasco area is the second largest of land subsidence in the San Joaquin Valley. It is traversed by the Friant-Kern Canal of the Central Valley Project which supplies water to several irrigation districts in the subsiding area. Although subsidence has not seriously affected the transportation of surface water, continued or accelerated subsidence could create serious problems. Lofgren and Klausing have described the pertinent geologic features of the water-bearing deposits in a separate report (Land subsidence in the Tulare-Wasco area, in preparation), and they have supplied the following brief description for this report. The unconsolidated deposits comprise the continental deposits from the Sierra Nevada. These deposits consist of poorly permeable to permeable lenticular beds of gravel, sand, silt, and clay that differ widely in extent and thickness and grade both laterally and vertically into one another. One persistent stratum, the Corcoran Clay Member of the Tulare Formation (Inter-Agency Committee, 1958), can be mapped in the western half of the Tulare-Wasco area west of U.S. Highway 99. Within the area where this stratum occurs, a threefold division of the continental deposits can be made as follows (fig. 5): (1) An upper unit, ranging in thickness from about 300 feet to 700 feet, which includes that part of the continental deposits from the Sierra Nevada overlying the Corcoran Clay Member; (2) the relatively impermeable Corcoran Clay Member, ranging in thickness from a feather edge to 100 feet, which not only serves as a distinctive geologic marker but also as the principal confining bed for the artesian aquifer underlying it; and (3) a lower unit which consists of that part of the continental deposits from the Sierra Nevada lying between the base of the Corcoran Clay Member and the underlying marine strata of upper Pliocene age. Ground water is pumped in considerable quantity for irrigation and other uses both from the semiconfined upper unit and from the confined aquifer system beneath the Corcoran Clay Member. The unconsolidated deposits penetrated by the core hole at Pixley (23/25-16N1) consist of 280 feet of continental deposits, 16 feet of the confining Corcoran Clay Member, and 464 feet of continental depositsPROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A5 119°30' 119°00' Figure 4.—Land subsidence 1948-54 and location of core holes in the Tulare-Wasco area. Prepared in cooperation with the California Department of Water Resources. Compiled by Ben E. Lofgren.A6 MECHANICS OF AQUIFER SYSTEMS Figure 5.—Simplified geologic section through core holes in the Tulare-Wasco area. Correlation by R. L. Klausing. lying below the Corcoran. These deposits are composed for the most part of yellowish-brown fine- to medium-textured sand, silt, and clay which were deposited chiefly in a subaerial environment. The core hole was drilled through the full depth of deposits tapped by most of the deeper water wells in the vicinity of Pixley. East of U.S. Highway 99, beyond the extent of the Corcoran Clay Member, the unconsolidated continental deposits range in thickness from about 200 feet to as much as 1,500 feet and are composed largely of lenticular beds of yellowish-brown fine- to coarse-tex-tured sand, silt, clay, and gravel which were laid down as alluvial-fan deposits. These deposits function chiefly as a semiconfined aquifer system and are the principal source of ground water in this area. Along the east side of the Tulare-Wasco area, consolidated and semiconsolidated marine rocks—upper Pliocene and Pliocene(?) marine strata and the Santa Margarita Formation of Diepenbrock (1933)—of Tertiary age underlie the unconsolidated continental deposits. The depth to the top of these marine rocks ranges from about 600 feet to 1,600 feet below the land surface; the rocks consist of alternating poorly permeable clay-stone, siltstone, and permeable sand. The sand beds are confined locally, and where they are penetrated by water wells, they function as confined aquifers. Although these rocks were deposited in a marine environment, the saline . connate water has subsequently been flushed out of the aquifers and replaced by fresh water. Downdip to the west, however, these aquifers still contain saline water. Marine rocks were penetrated by the core hole at Richgrove (24/26-36A2) from a depth of 744 feet below the land surface to 2,200 feet. This section of marine rocks is composed of 897 feet of blue-gray claystone and siltstone of upper Pliocene age, underlain successively by 259 feet of sediments of similar texture of Pliocene(?) age, and by 300 feet of well-sorted gray sand of Miocene age (Klausing and Lohman, 1964). The sand has been identified as the Santa Margarita Formation of Diepenbrock (1933, p. 13) and, in the vicinity of Richgrove, it is an important source of water. SANTA CLARA VALLEY The Santa Clara Valley extends about 100 miles southeastward from San Francisco. The valley is a large structural trough bounded on the southwest by the Santa Cruz Mountains and on the northeast by the Diablo Range. Subsidence occurs in the central reach of the valley in an area of intensive ground-water development which extends from Redwood City on the west, and Niles on the east, southeastward about 30 miles to Coyote (fig. 6). It is this central reach that will be referred to hereafter as the Santa Clara Valley. San Jose is the largest city within the subsiding area. Intensive agricultural development is rapidly changing to urban development; both have depended almost wholly on ground water to date (1965). The area of subsidence lies wholly within the area of valley fill and corresponds in general to the area of confined ground water; the line of 0.1-foot subsidence for the period 1934-54 encloses at least 230 square miles, according to Poland and Green (1962). Subsidence of the land surface from 1934 to 1960 is shown by lines of equal subsidence in figure 6. This map shows that the subsidence in and near San Jose and Sunnyvale during the 26-year period exceeded 5 feet. Core holes were drilled in the two areas of maximum subsidence. The general geology of the Santa Clara Valley has been described in some detail by Davis and Jennings (1954) and Davis (1955). The water-bearing sediments have been described by Clark (1924), Tolman and Poland (1940), and the California State Water Resources Board (1955). The generalized geology of the central part of the Santa Clara Valley is shown in figure 6 Pertinent geologic features of the water-bearing deposits are described in a separate report (J. H. Green and J. F. Poland, Land subsidence and aquifer-system compaction in the Santa Clara Valley, in preparation). The water-bearing deposits of the Santa Clara Valley from San Jose north to San Francisco Bay consist primarily of lenses and stringers of clay, silt, and sandy clay, and lesser amounts of sand and gravel. Near San Francisco Bay, fine-textured sediments predominate, but toward the south, west, and east—the sediment source areas—the subsurface sediments are more coarse textured. At the two core holes, and probably beneathPROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A7 122°15' 122°00' 121 °45' Fault Dashed where approximate; Dotted where concealed Line of equal subsidence Interval 1, 0.5, and 0.1 foot; dashed where poorly controlled. Compiled from leveling of U.S. Coast and Geodetic Survey 7S/1E-16C6 • Core hole and identification number Alluvium and bay deposits Santa Clara Formation Semiconsolidated deposits Consolidated rocks Undifferentiated igneous, meta-morphic, and consolidated sedimentary rocks Figure 6.—Land subsidence, 1934-60, and location of core holes in the Santa Clara Valley. Compiled by J. H. Green. 263-524 0-67—3A8 MECHANICS OF AQUIFER SYSTEMS much of the valley, the water-bearing deposits are more than 1,000 feet thick. The depth to their base is not known. These water-bearing deposits comprise the unconsolidated alluvial and bay deposits and the underlying Santa Clara Formation of Pliocene and Pleistocene age. The boundary between these two units has not been identified in well logs. However, where it is exposed on the flanks of the valley, the Santa Clara Formation consists of semiconsolidated poorly sorted conglomerate and sandstone, as well as siltstone and claystone, and has a low permeability. The bedrock ranges in age from Jurassic to Pliocene and consists principally of consolidated sedimentary rocks and minor areas of metamorphic and igneous rocks. FIELD SAMPLING The samples for which test results are presented in this report were obtained from eight core holes. (See figs. 2-6; table 1.) The core holes in the Los Banos-Kettleman City area were drilled in 1957 and 1958, the holes in the Tulare-Wasco area in 1958 and 1959, and the holes in the Santa Clara Valley in 1960. These core holes were drilled by a rotary-drilling rig operated by Bureau of Reclamation drilling crews experienced in the difficult technique of coring unconsolidated sediments. The rotary core barrels used were modified from commercial core barrels of the double-tube type, which have an outer rotating barrel and an inner stationary barrel. The inside diameter of the core barrel was nominally 3 inches, and the average diameter of core recovered was about 2/ inches. In most of the work, a core barrel capable of taking a core 10 feet long was used. A 20-foot core barrel was tried but did not give as good core recovery. Above the Corcoran Clay Member of the Tulare Formation in the Los Banos-Kettleman City area, a 10-foot interval was cored after each 30 feet of drilling. Below the top of the Corcoran Clay Member, coring was generally continuous to the bottom of the hole. Core recovery was excellent for unconsolidated to semiconsolidated alluvial deposits of sand, silt, and clay. For example, at core hole 14/13-llDl, the accumulated cored interval was 998 feet and the aggregate core footage brought to land surface was 696 feet, an average core recovery of 70 percent. Core hole 19/17—22J1, near Huron, was to be drilled to a depth of 2,200 feet, but the drill pipe became stuck at 1,930 feet. Because efforts to free the pipe were unsuccessful, it was shot off at 1,760 feet. An adjacent hole, 22J2, was drilled to 1,910 feet and cored below. Thus, at core-hole site 19/17-22Jl, 2, cores above 1,910 feet are from Jl and below 1,910 feet are from J2. The core hole location is designated 19/17— 22Jl, 2 in the rest of this paper. In the Pixley core hole (23/25-16N1) to a depth of 260 feet, a 10-foot interval was cored after each 30 feet of drilling. From 260 feet to 752 feet, coring was continuous. Through the sections cored, core recovery was 73 percent. In the Richgrove core hole (24/26-36A2), no cores were taken to a depth of 50 feet, and then coring was continuous to a depth of 1,965 feet. From 1,965 feet to the well bottom at 2,200 feet, a 10- to 20-foot interval was cored after each 30-40 feet of drilling. Core recovery was about 80 percent in the Richgrove core hole. At core hole 6S/2W-24C7 in the Santa Clara Valley, the accumulated cored interval was 796 feet and the aggregate core footage brought to land surface was 548 feet, an average core recovery of 69 percent. At core hole 7S/1E-16C6 the average core recovery was only 30 percent because recovery was very low in the coarse, loose water-bearing material. Hence, the core suite obtained does not contain a representative sampling of the coarser, most permeable layers. At each of the drilling sites, cores were laid out in sequence in 4-foot wooden core boxes and properly labeled for future reference. From each 10-foot interval cored, the following samples were collected: 1. Physical characteristic sample.—One quart-sized sample (about 6 in. long), taken from the most representative materials of the cored interval, was sealed in wax in a cardboard container to preserve the natural moisture content insofar as practicable and to prevent disturbance of the core. These samples were tested by the Hydrologic Laboratory of the Geological Survey. 2. Petrographic sample.—One or more samples, taken from the same materials and contiguous to the physical characteristic samples, were collected and sealed in wax in a 1-pint cardboard container and retained for petrographic examination. For paleontologic examination, samples also were taken of fossiliferous beds in the Richgrove, San Jose, and Sunnyvale core holes; they were not sealed in wax. 3. General purpose sample.—Two or more half-pint samples were collected for general reference, one representing the fine-textured materials and one representing the coarse-textured layers; they were retained in cardboard cartons but not sealed in wax. In addition, undisturbed samples of representative fine-grained deposits were collected for consolidation tests in the Earth Laboratory of the Bureau of Reclamation. Quart-sized samples were carefully selectedhr! Table 1.—Identification of core holes [Core-hole punch-card code gives location by latitude and longitude. The first 6 digits indicate latitude in degrees, minutes and seconds. The letter N designates north latitude. The next 7 digits indicate longitude in degrees, minutes and seconds. The final digit following the decimal point identifies the well or test hole number at this location] Area County Core hole Location Punch-card code Nearest town USGS Hydrologic Depth Laboratory sample (feet) numbers USBR Earth Laboratory sample numbers Los Banos-Kcttleman City., Fresno 12/12-16H1 14/13-11D1 16/15-34N1 365326N 1203914.1____ 364358N 1203149.1____ 362913N 1201958.1____ Oro Loma_____ Mendota______ Cantua Creek_ 1, 005 1, 500 2, 000 Tulare-Wasco_____ Santa Clara Valley ............. 19/17-22J1.2____ Tulare_______ 23/25-16N1______ 94/96-16 A 9 Santa Clara... 6S/2W-24C7~_ 11 ’ _____________ 7S/1E-16C6______ 361534N1200610.1,2. 355523N1191706.1___ 354807N1190631.1___ 372404N 1220204.1__ 371947N 1215206.1__ Huron_____ Pixley____ Richgrove. Sunnyvale. San Jose.. 2, 203 760 2, 200 1, 004 1, 002 None_________ 57CAL1-103___ 58CAL1-98____ 57CAL104-206.. 58CAL99-145___ 59CAL310-419.. 60CAL10-69____ 60CAL70-96____ 23L91-108. 23L80-90, 194-196. 23L197-198, 200-202, 204, 206-208, 210, 212, 214, 215, 217, 219, 221-223, 235. 23L181-193. 23L226-229, 232, 234. 23L236-254. 23L255-263, 265, 267, 269. 23L271-273, 275, 277, 279, 280, 282-284. > Driller’s depth was 2,000 feet and depths for samples given in this report are correlated to the 2,000-foot depth. The electric log was run to a depth of 2,007 feet. Subsequently the new drill pipe used for this hole was measured and was found to be 0.35 foot longer per 100 feet than the figure used during coring. > CO ERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIAA10 MECHANICS OF AQUIFER SYSTEMS and then sealed in wax in metal containers to keep them in an undisturbed condition. Results of the laboratory analyses are given in tables 5-10 at the end of this paper. Tests by the Hydrologic Laboratory of the Geological Survey are reported in tables 5-7, inclusive, and table 10. Tests made in the Earth Laboratory of the Bureau of Reclamation are reported in tables 8 and 9. COMPOSITE LOGS OF CORE HOLES An electric log was obtained for each core hole after coring was completed. Graphic logs and generalized lithologic descriptions were prepared from the geologists’ logs made at the drill site, supplemented by interpretation of the electric log in zones not cored or of poor recovery. These three elements have been combined to give a composite log for each core hole (pl.l). The depths of the samples tested, both by the Hydro-logic Laboratory and by the Earth Laboratory of the Bureau of Reclamation, also are plotted on the composite logs. The interpretation of electric logs is based on the principle that, in fresh-water-bearing deposits such as those penetrated in this area, high resistivity values are indicative of sand and low resistivity values are indicative of clay and silty clay. Intermediate values are indicative of clayey silt, silt, silty sand, and other sediments classified texturally between sand and clay. Resistivity is indicated by the right-hand curve of the electric log; it increases toward the right. Thus, the Corcoran Clay Member of the Tulare Formation is indicated by a curve segment of uniformly low resistivity (pi. 1 A). The electric logs of the core holes can be compared with the physical and hydrologic properties of the samples plotted according to depth in pis. 12-14. ACKNOWLEDGMENTS The core holes in the San Joaquin Valley were drilled as a part of the interagency program of land-subsidence studies. The following geologists from the three agencies cooperated in the collection and description of the core samples from these core holes: D. C. Blakely, W. B. Bull, W. A. Cochran, J. H. Green, R. L. Klausing, B. E. Lofgren, and R. H. Meade, Geological Survey; W. R. Cooke, R. J. Farina, and N. Prokopovich, Bureau of Reclamation; B. Aarons, R. Bartlett, C. Carlson, W. R. Hail, B. G. Hicks, F. Kreese, and W. D. Pederson, California Department of Water Resources. The two core holes in the Santa Clara Valley were drilled as a part of the Federal study of mechanics of aquifers. The Survey geologists who collected and described core samples in the Santa Clara Valley were W. B. Bull, R. L. Klausing, R. H. Meade, G. A. Miller, and F. S. Riley. Both core holes were drilled by the Bureau of Reclamation. Consolidation tests for core holes 12/12-16H1, 16/15-34N1, and 23/25-16N1 were financed by the Bureau of Reclamation, and tests for core holes 14/13— 11D1, 19/17-22J1, 2, 24/26-36A2, 6S/2W-24C7, and 7S/1E-16C6 by the Geological Survey. All analyses by the Hydrologic Laboratory were financed by the Geological Survey. H. J. Gibbs, Head of Special Investigations and Research Section, Bureau of Reclamation, Denver, Colo., provided assistance by his review of parts of this report. METHODS OF LABORATORY ANALYSIS In the Hydrologic Laboratory, cores 2 inches in diameter by 2 inches long were obtained by forcing thin-wall brass cylinders into the larger core—one in a direction at right angles to the bedding (vertical) and the other parallel to the bedding ('horizontal). These small cores were used for permeability tests and for determining unit weight and porosity. The hydraulic press designed for obtaining the cores is shown in figure 7. The rest of the large core was prepared and used for determination of specific gravity, particle-size distribution, and Atterberg limits and indices. Sample preparation for these analyses began with the air-drying of chunks of the large core. These chunks of material were then gently but thoroughly separated into individual particles in a mortar with a rubber-covered pestle. Care was taken to prevent crushing of the individual particles. Core samples were analyzed by the Hydrologic Laboratory using the standard methods described briefly in the following paragraphs. Core samples also were analyzed by the Earth Laboratory following standard procedures described by the U.S. Bureau of Reclamation (1960, p. 407-508). Additional information on the theory and methods of analysis is available in Meinzer (1923, 1949), Wenzel (1942), Taylor (1948), and the American Society for Testing Materials (1958). PARTICLE-SIZE DISTRIBUTION A particle-size analysis, also termed a “mechanical analysis,” is the determination of the distribution of particle sizes in a sample. Particle sizes smaller than 0.0625 mm were determined by the hydrometer method of sedimentation analysis, and sizes larger than 0.0625 mm were determined by wet-sieve analysis. The hydrometer method of sedimentation analysis consisted of (1) dispersing a representative part of the prepared sample with a deflocculating agent, sodiumPROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA All Figure 7.—Hydraulic press used for obtaining small cores from large cores of unconsolidated sediments. hexametaphosphate, in 1 liter of water and (2) measuring the density of the suspension at increasing intervals of time with a soil hydrometer. At given times, the size of the largest particles remaining in suspension at the level of the hydrometer was computed by use of Stokes’ law, and the weight of particles finer than that size was computed from the density of the suspension at the same level. After the hydrometer analysis, the sample was poured into a sieve which had openings of 0.0625 mm. The sample then was gently agitated and washed over the sieve. The material retained was carefully dried and placed in a set of standard 8-inch sieves which were shaken for a period of 15 minutes on a Ro-tap mechanical shaker. The fraction of the sample remaining on each sieve was weighed on a balance. From the hydrometer analysis and the sieve analysis, the percentage of the particles smaller than a given size was calculated and plotted as a cumulative distribution curve. The particle sizes, in millimeters, were plotted as abscissas on a logarithmic scale and the cumulative percentages of particles smaller than the size shown, by weight, as ordinates on an arithmetic scale. The percentage in each of several size ranges was then determined from this curve. The analyses were divided into the following groups according to their particle sizes: Diameter (mm) Gravel__________ Very coarse sand Coarse sand_____ Medium sand_____ Fine sand_______ Very fine sand__ Silt-size_______ >2. 0 1. 0 -2. 0 .5 -1.0 .25 - . 5 . 125 - . 25 . 0625- . 125 . 004 - . 0625 Clay-size_______________________ <0. 004 This classification system is used by the Water Resources Division, U.S. Geological Survey, and is identical to classifications proposed by Wentworth (1922) and the National Research Council (Lane, 1947), except that those authors proposed further subdivisions of gravel, silt, and clay. Subsequent references to sand, silt, and clay in this report will relate to sand-, silt-, and clay-size particles as specified in the foregoing table. PERMEABILITY Permeability is the capacity of rock or incoherent material to transmit water under pressure. It can be determined in the laboratory by observing the rate of percolation of water through a sample of known length and cross-sectional area, under a known difference in head. The basic law for flow of fluids through porous materials was established by Darcy who demonstrated experimentally that the rate of flow of water was proportional to the hydraulic gradient. Darcy’s law may be expressed as Q=kiA, where Q is the quantity of water discharged in a unit of time, A is the total cross-sectional area through which the water flows, i is the hydraulic gradient (the difference in head, h, divided by the length of flow, L), and k is the coefficient of permeability of the material for water, or so, which is defined as that particle diameter which is larger than 50 percent of the diameters and smaller than the other 50 percent. It is determined by reading, from the particle-size distribution curve, the particle diameter at the point where the particle-size distribution curve intersects the 50-percent line. The quartile deviation is a measure of spread of particle sizes. Quartiles are the particle-diameter values read at the intersection of the curve with the 25- (Qi), 50- (Qi), and 75- (Q3) percent lines. By convention, the third quartile (Q3) is always taken as the larger value, regardless of the manner of plotting. The geometrical quartile deviation, or the “sorting coefficient,” So, of Trask (1932, p. 70-72), is represented by the equation So=-jQ3/Qi. The log quartile deviation is the log of the geometrical quartile deviation, or sorting coefficient, So, and is represented by the equation Logio No = (log Q3—log Qi)/2. The log So can be expressed to the base 10 (Krumbein and Pettijohn, 1938, p. 232) and is so tabulated in this report. As noted by Krumbein and Pettijohn (1938, p. 232), the geometric quartile measures are ratios between quartiles and thus have an advantage over the arithmetic quartile measures in that they eliminate both the size factor and the unit of measurement. They do not, however, give a directly comparable value for the spread of the curve. The logarithmic measures do give a direct comparison because the logio So (the log quartile deviation) increases arithmetically. Thus, a sediment having logio So = 0.402 is twice as widely spread between Q\ and Q3 as one having logio So = 0.201. Many sedimentologists now use a scale in which 0=—log2 d, in which d is the diameter in millimeters. This scale has certain advantages over the logio scale for expressing quartile deviation and other statistical parameters (Krumbein and Pettijohn, 1938, p. 233-235). Therefore, statistical parameters have been listed in terms of the scale by Meade (1967).MECHANICS OF AQUIFER SYSTEMS A 22 TRIANGULAR PARTICLE-SIZE DIAGRAMS ARE SUBDIVIDED CORE HOLE 14/13-11D1 ACCORDING TO THE SYSTEM PROPOSED BY SHEPARD (1954) Sand 2-0.0625 Silt0:0625-0.004 Clay <0.004 o o CORE HOLE 16/15-34N1 CORE HOLE 19/17-22J1.2 Figure 13.—Sediment classification for samples from core holes in the Los Banos-Kettleman City area.PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A23 CORE HOLE 23/25-16N1 CORE HOLE 24/26-36A2 TULARE-WASCO AREA TRIANGULAR PARTICLE-SIZE DIAGRAMS ARE SUBDIVIDED ACCORDING TO THE SYSTEM PROPOSED BY SHEPARD (1954) Sand 2-0.0625 Silt 0.0625- 0.004 Clay <0.004 o o CORE HOLE 6S/2W-24C7 CORE HOLE 7S/1E-16C6 SANTA CLARA VALLEY Figure 14.—Sediment classification for samples from core holes in the Tulare-Wasco area and Santa Clam Valley. 263-524 0-67—5A24 MECHANICS OF AQUIFER SYSTEMS The statistical measures for samples from core holes in the Los Banos-Kettleman City area (table 5) are summarized as follows: 1. Median diameter ranges from 0.001 to 0.520 mm, those for samples of the Corcoran Clay Member being near the lower limit. 2. The sorting coefficient, So, ranges from 1.1 to 17.2. According to Krumbein and Pettijohn (1938, p. 232), an So value of less than 2.5 indicates a well-sorted sediment, of 3 a normally sorted sediment, and of 4.5 a poorly sorted sediment. 3. The log quartile deviation, logi0 So, ranges from 0.061 to 1.236, the maximum spread being about 20 times as great as the minimum. The statistical measures for samples from core holes in the Tulare-Wasco' area (table 5) are summarized as follows: 1. Median diameter ranges from about 0.01 to 0.3 mm for core hole 23/25-16Nl and from about 0.003 to 1.4 mm for core hole 24/26-36A2, those for samples of the Corcoran Clay Member being near the lower limit. 2. The sorting coefficient, So, ranges from 1.4 to 7.2 for core hole 23/25-16Nl, and from 1.2 to 14.1 for core hole 24/26-36A2. 3. The log quartile deviation (log10 So) for core hole 23/25-16N1 ranges from 0.132 to 0.948, the maximum spread being about 10 times as great as the minimum. For core hole 24/26-36A2, the range is 0.095 to 1.150, the maximum spread being about 12 times as great as the minimum. The statistical measures for samples from core holes in the Santa Clara Valley (table 5) are summarized as follows: 1. Median diameter ranges from about 0.001 to 0.2 mm, for core hole 6S/2W-24C7 and from about 0.004 to 1.5 mm for core hole 7S/1E-16C6. 2. The sorting coefficient, So, ranges from 1.3 to 7.5 for core hole 6S/2W-24C7 and ranges from 1.3 to 7.8 for core hole 7S/1E-16C6. 3. The log quartile deviation, log™ So, for core hole 6S/2W-24C7 ranges from 0.127 to 0.876, the maximum spread being about seven times as great as the minimum. For core hole 7S/1E-16C6, the range is 0.246 to 0.885, the maximum spread being about four times as great as the minimum. The above averages, however, represent only the fine-textured sediments and do not include the coarser sediments that were not recovered. PERMEABILITY The value of the coefficient of permeability depends in general on the degree of sorting and upon the arrangement and size of particles. It is usually low for clay and other fine-grained or tightly cemented materials and high for coarse clean gravel. In general, the permeability in a direction parallel to the bedding plane of the sediments (referred to as horizontal permeability in this report) is greater than the permeability perpendicular to the bedding plane (referred to as vertical permeability in this report). Most water-bearing materials of significance as sources of water have coefficients of permeability above 100 gpd per sq ft (gallons per day per square foot). The coefficients of vertical permeability for 205 samples from core holes in the Los Banos-Kettleman City area (table 5) ranged from 0.00007 to 370 gpd per sq ft. Samples from the Corcoran Clay Member were of consistently low permeability. Figure 15 shows that the greatest percentage of the samples tested had vertical permeabilities in the range of 0.0001 to 0.001 gpd per sq ft and the next greatest in the range of 0.001 to 0.01. The greatest percentage had horizontal permeabilities in the range of 0.001 to 0.01. Vertical and horizontal permeabilities were obtained on 62 paired samples, chiefly from core hole 16/15-34N1. The vertical permeabilities for these 62 paired samples ranged from 0.0002 to 260 gpd per ft, and the horizontal permeabilities ranged from 0.0002 to 330. For 54 of these samples, horizontal permeability did not exceed 10 times the vertical permeability, but for 8 samples horizontal permeability was in the range of 11 to 200 times as great as vertical permeability. Excluding the 8 samples having the high ratios, the average vertical permeability for the 54 paired samples was 9.3 gpd per sq ft, and their ratios of horizontal to vertical permeability averaged 2.7. The coefficients of vertical permeability for 138 samples from core holes in the Tulare-Wasco area (table 5) ranged from 0.0002 to 650 gpd per sq ft. Samples from the Corcoran Clay Member (hole 23/25-16N1, samples 58CAL106 and 107) were of consistently low permeability. The range for horizontal permeability for 79 samples was 0.0003 to 61 gpd per sq ft. The greatest percentage of samples tested had vertical permeabilities in the range of 0.01 to 0.1 gpd per sq ft (fig. 15) and the next greatest in the range of 0.001 to 0.01. Vertical and horizontal permeabilities were obtained on 76 paired samples from the Tulare-Wasco area. Horizontal permeability was greater (as much as 100 times greater) than vertical permeabilities in 47 samples, 17 of them from 23/25-16N1 and 30 from 24/26-36A2. Vertical permeability was greater (usually not more than two or three times greater) than horizontal permeability in 16 samples, 10 of them from 23/25-16N1 and 6 from 24/26-36A2. In 13 samples—6 from 23/25-16N1 and 7 from 24/26-36A2—vertical permeability equaled horizontal permeability. The averagePERCENTAGE OF SAMPLES IN PERMEABILITY RANGE PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A25 30 20 10 0 40 30 20 10 0 40 §0 20 10 0 Core hole 16/15-34N1 30 20 10 0 LOS BANOS-KETTLEMAN CITY AREA Vertical permeability 66 samples - - Core hole 14/13-11D1 40 30 20 ■ 10 ■ 0 ■ 30 20 10 0 Vertical permeability 92 samples Horizontal permeability 45 samples Core hole 24/26-36A2 TULARE-WASCO AREA PERMEABILITY, IN GALLONS PER DAY PER SQUARE FOOT Core hole 23/25-16N1 Core hole 6S/2W-24C7 TULARE-WASCO AREA SANTA CLARA VALLEY Figure 15—Range in permeability of samples from core holes.A26 MECHANICS OF AQUIFER SYSTEMS vertical permeability of the 76 paired samples was 0.5 gpd per sq ft, and the average horizontal permeability was 0.7 gpd per sq ft. The coefficients of vertical permeability for 47 samples from core holes in the Santa Clara Valley (table 5) ranged from 0.0001 to 0.03 gpd per sq ft. The range for horizontal permeability for 65 samples was 0.0002 to 190 gpd per sq ft. The greatest percentage of samples tested had horizontal permeabilities in the range of 0.001 to 0.01 gpd per sq ft and the next greatest in the range of 0.0001 to 0.001; the greatest percentage for vertical permeabilities was in the range 0.0001 to 0.001, and the next greatest was in the range of 0.001 to 0.01. Vertical and horizontal permeabilities were obtained on 47 paired Santa Clara Valley samples. Horizontal permeability was greater (as much as 200 times greater) than vertical permeability in 31 samples, 22 of them from 6S/2W-24C7 and 9 from 7S/1E-16C6. Vertical permeability was greater (usually not more than two or three times greater) than horizontal permeability in seven samples, three of them from 6S/2W-24C7 and four from 7S/1E-16C6. In nine samples—five from 6S/2W-24C7 and four from 7S/1E-16C6—vertical permeability equaled horizontal permeability. The average vertical permeability of the 47 paired samples was 0.003 gpd per sq ft and the average horizontal permeability was 0.02 gpd per sq ft. As noted before, the coarser, most permeable deposits were not recovered in the core barrel. Thus, the average permeability for all samples tested in each core hole does not represent the true average permeability of the sediments penetrated. It is estimated that coarse-tex-tured deposits having permeabilities at least as great as 2,000-3,000 gpd per sq ft were present in each of the core holes, but the samples were not cored or were lost during the coring. Figures 16 and 17 are diagrams showing the relation between vertical permeability and texture for samples from core holes in the San Joaquin and Santa Clara Valleys. Permeabilities have been grouped into eight ranges; a symbol representing the proper permeability range for each sample is plotted in the appropriate textural location on the triangle, which is subdivided according to the system proposed by Shepard (1954). Although the highest permeabilities occur in the coarse-textured and well-sorted samples, permeabilities within each textural classification vary considerably. Vertical permeability values are plotted according to depth for samples from all three areas in plates 12-14. In these figures vertical permeability values can be compared to other physical properties. The coefficients of vertical permeability for the clayey sediments of low permeability (P<0.01-0.001 gpd per sq ft) tested by the Hydrologic Laboratory in the vari- able-head permeameter under no load (table 5) in general appear to be in a considerably higher range than those in table 9 (ft per yrX0.0205 = gpd per sq ft) which were computed from the consolidation tests made by the Bureau of Reclamation for samples of similar texture. There are at least three reasons for this difference: 1. The permeability of a clayey sediment decreases markedly with decrease in void ratio (or porosity). The coefficients of permeability given in table 9 (in feet per year) are computed from time-consolidation data derived from test loads ranging from 100 to 1,600 psi (pounds per square inch) and thus represent conditions of substantially reduced void ratios from those of the samples tested in an unloaded condition in the variable-head permeameter. For sample 23L-207 (table 9), the computed coefficient of vertical permeability for the load range 100 to 200 psi is about 50 times as high as that for the load range 800 to 1,600 psi. For sample 23L-253 (table 9), the computed coefficient of permeability for the load range 400 to 800 psi is about four times as high as that for the load range 800 to 1,600 psi. For sample 23L-277, taken at a depth of 509 feet in core hole 7S/1E-16C6 (table 9), the computed coefficient of permeability for the load range 100 to 200 psi is about six times as high as for the load range 800 to 1,600 psi. The coefficients at unloaded conditions would be even higher. 2. For a clayey sediment, the water used for testing permeability in the variable-head permeameter, if not chemically compatible with the pore water, may affect the results substantially. In the water used in the Hydrologic Laboratory for the variable-head tests, calcium was the predominant cation (see analysis, p. A13); however, sodium is the predominant cation in the pore water of the sediments beneath the Corcoran Clay Member in the Los Banos-Kettleman City area. The use of water in which the calcium ion is predominant in testing cores of such sediments would tend to increase the value of the coefficient of permeability obtained in the variable-head tests. The consolidation tests, however, did not involve the passage of water through the sample, only the squeezing out of native pore water. 3. For a sample of very low permeability tested under no load in a variable-head permeameter, the disturbed condition of the sample at and near the container wall creates a boundary region which may produce a zone of appreciably higher permeability than that of the undisturbed samplePROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A27 matrix. Tests in a consolidometer, however, create lateral pressure against the container walls and thus tend to reduce the permeability of the disturbed boundary region to approximately that of the sample matrix. For these three reasons, the coefficients of permeability of the clayey sediments as derived from the unloaded variable-head permeameter tests (table 5) are not directly comparable to those computed from the time-consolidation data (table 9). Coefficients from the consolidation tests are considered more reliable for samples taken as deep as these, but, to be meaningful for field applications, the coefficients would have to be computed at the void ratio, or porosity, existing under the overburden (effective) stress conditions in the field. SPECIFIC GRAVITY, UNIT WEIGHT, AND POROSITY The specific gravity of a sediment is the average of the specific gravities of all the constituent mineral particles. The specific gravity of most clean sands is usually near 2.65, whereas that of clays ranges from 2.5 to 2.9. Organic matter in the sediment will lower its specific gravity. The dry unit weight of a sediment is dependent upon the shape, arrangement, and mineral composition of the constituent particles, the degree of sorting, the amount of compaction, and the amount of cementation. Dry unit weights of unconsolidated sediments commonly range from 1.2 to 1.8 g per cc (grams per cubic centimeter), or 75 to 112 lb per cu ft (pounds per cubic foot). Because porosity is calculated from the dry unit weight and specific gravity of the sediment, it is dependent upon the same factors. Most natural sands have porosities ranging from 25 to 50 percent, and soft clays from 30 to 60 percent. Compaction and cementation tend to reduce these values. The results of the tests for these three properties of the sediments described in this report are given in table 4. The specific gravity of samples from the Los Banos-Kettleman City area ranged from 2.62 to 2.79, core hole 14/13-1 lDl; from 2.43 to 2.76, core hole 16/15-34N1; and from 2.48 to 2.76, core hole 19/17— 22Jl, 2 (plate 12). The lowest specific gravities in this area were for a few samples taken between depths of approximately 1,700 and 1,950 feet in the central (16/15-34N1) and southern (19/17—22J1, 2) core holes and appear to be due to a high organic content. The specific gravity of solids of samples from the Tulare-Wasco area ranged from 2.65 to 2.75, core hole 23/25-16N1, and from 2.41 to 2.79, core hole 24/26-36A2 (pi. 13). The lowest specific gravity was for a sample from core hole 24/26-36A2 taken at a depth of 1,058 feet, which is a rhyolitic ash zone. The specific gravity of solids from the Santa Clara Valley ranged from 2.67 to 2.79, core hole 6S/2W-24C7, and from 2.68 to 2.80, core hole 7S/1E-16C6 (pi. 14). In general, specific gravity increases with depth below 300 feet in samples from oore hole 7S/1E-16C6. The dry unit weight for samples from the Los Banos-Kettleman City area ranged from 1.17 to 1.95 g per cc (73.0 to 121.7 lb per cu ft) for sediments from core hole 14/13—llDl; from 1.10 to 1.81 g per cc (68.6 to 112.9 lb per cu ft), core hole 16/15-34N1; and from 1.33 to 1.84 g per cc (83.0 to 114.8 lb per cu ft), core hole 19/17—22J1, 2 (pi. 12). The dry unit weight for samples from the Tulare-Wasco area ranged from 1.05 to 1.82 g per cc (65.5 to 113.6 lb per cu ft) for sediments from core hole 23/25-16Nl, and from 1.00 to 1.94 g per cc (62.4 to 121.1 lb per cu ft), core hole 24/26-36A2 (pi. 13). The dry unit weight for samples from the Santa Clara Valley ranged from 1.34 to 1.88 g per cc (83.7 to 117.4 lb per cu ft) for sediments from core hole 6S/2W-24C7 and from 1.55 to 1.91 g per cc (96.8 to 119.2 lb per cu ft), core hole 7S/1E-16C6 (pi. 14). The porosity for samples from the Los Banos-Kettleman City area ranged from 28.0 to 56.2 percent (void ratio 0.39 to 1.28) for the sediments from core hole 14/13—11 Dl; from 32.7 to 54.7 percent (void ratio 0.49 to 1.20), core hole 16/15—34N1; and from 32.8 to 50.0 (void ratio 0.49 to 1.00), core hole 19/17—22J1, 2 (pi. 12). For samples from the Tulare-Wasco area, the porosity ranged from 32.1 to 61.0 percent (void ratio 0.47 to 1.56) for the sediments from core hole 23/25-16Nl, and from 28.4 to 61.2 (void ratio 0.40 to 1.58), core hole 24/26-36A2 (pi. 13). In general, samples from the Corcoran Clay Member have high porosities and low dry unit weights. This characteristic undoubtedly is due in part to the diatom frustules so common in the Corcoran Clay Member. Samples from the upper Pliocene marine strata also had high porosities and low dry unit weights. For samples from Santa Clara Valley, the porosity ranged from 31.4 to 50.4 percent (void ratio 0.46 to 1.01) for the sediments from core hole 6S/2W-24C7, and from 30.5 to 43.0 (void ratio 0.44 to 0.75), core hole 7S/1E-16C6 (pi. 14). In general, the porosities decrease with depth below land surface, and dry unit weights increase with depth. Athy (1930) described just such a progressive compaction of sediments as the load of over-lying material increased with deposition. However, the graphs in plate 13 show that the porosity increases with depth in core hole 24/26-36A2, especially in the depth range from 600 to 1,600 feet. Thus, the usual relation of porosity and dry unit weight to depth is markedly anomalous in this core hole. Plate 13 also shows that the porosity and dry unit weight do not change appreciably with depth in core hole 23/25-16Nl, butA28 MECHANICS OF AQUIFER SYSTEMS o o TRIANGULAR PARTICLE-SIZE DIAGRAMS ARE SUBDIVIDED CORE HOLE 16/15-34N1 ACCORDING TO THE SYSTEM PROPOSED BY SHEPARD (1954) RANGE OF PERMEABILITY (vertical) In Meinzer units Q 100-1000 O 10-100 O 1-10 CORE HOLE 14/13-11D1 CORE HOLE 19/17-22J1.2 Figure 16.—Relation between permeability and texture for samples from core holes in the Los Banos-Kettleman City area.PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A29 CORE HOLE 23/25-16N1 TRIANGULAR PARTICLE-SIZE DIAGRAMS ARE SUBDIVIDED ACCORDING TO THE SYSTEM PROPOSED BY SHEPARD (1954) CORE HOLE 24/26-36A2 TULARE-WASCO AREA RANGE OF PERMEABILITY (vertical) In Meinzer units Q 100-1000 O 10-100 O !-10 CORE HOLE 6S/2W-24C7 SANTA CLARA VALLEY CORE HOLE 7S/1E-16C6 Figure 17.—Relation between permeability and texture for samples from core holes in the Tulare-Wasco area and the Santa Clara Valley.A30 MECHANICS OF AQUIFER SYSTEMS these properties also are relatively constant in the same depth interval of core hole 24/26-36A2. The anomalous porosity-depth relation for core hole 24/26-36A2 is being appraised statistically and analyzed in detail by R. H. Meade (Compaction of sediments underlying areas of land subsidence in central California, manuscript in preparation). The general trends discussed in the previous paragraphs are complicated by other factors which affect the unit weight and porosity of individual samples. These factors are (1) differences in particle sizes or in particle-size distribution, (2) differences in type of clay mineral, (3) exposure to atmosphere and preconsolidation, such as by desiccation, during their depositional history, (4) differences in intergranular structure as originally deposited, and (5) change in volume and structure of the core during and subsequent to the sampling operations. The first four factors are natural phenomena, whereas the last one, the change in volume and structure of the core during and subsequent to the sampling operation, is introduced by man in his disturbance of the natural state in order to procure the sample. The sediments cored in these holes ranged in depth from 70 to 2,100 feet below the land surface. The effective stress, or grain-to-grain load, of the overburden on these materials in place increased from about 50 to 1,000 psi in this depth range. While the core was being cut, additional load was placed on the material by the core barrel and drill pipe, especially near the outer edge of the core. As soon as the materials were encased in the core barrel, however, the effective stress of the overburden was removed and they expanded elastically. Thus, the change in volume (porosity and unit weight) from the natural to the laboratory condition is a function of several variables: 1. Compacting effect produced by displacement of the material by the cutting edge, by the insidewall friction, or by overdriving of the core barrel. 2. Expanding effect of removal of the effective stress of the overburden load at the time the core enters the barrel; the magnitude depends on the elasticity of the material and on the amount of the effective stress removed (increasing with depth). 3. Disturbing effects of mechanical rotation of core- barrel teeth and core catcher while cutting the core, removal of core from barrel, packing, shipping, unpacking, and processing. The net effect of this sampling process is believed to be an expansion of the sediments as tested in the laboratory; thus the values given in table 5 are slightly higher for porosity and lower for unit weight than exist in the natural state. On the basis of a study of the consolidation and rebound data, the laboratory-determined porosity of the fine-textured materials is estimated to be as much as 2-3 percent higher than the in-place field porosity (J. F. Poland, written com-mun., 1963). The effect of differences in particle size or particle-size distribution on porosity and unit weight is discussed on page A27. MOISTURE CONTENT The moisture contents of samples from core hole 6S/2W-24C7 in the Santa Clara Valley are listed in table 3. The wet weights of the samples were determined in the field immediately upon removal from the core barrel. The samples were dried at 110°C for 48 hours and reweighed, and the moisture contents then were calculated. Replicate tests provided some indication of the validity of the moisture-content data—the larger the difference between the two tests, the less reliable the values. Samples that had abnormally high differences between the replicate values are indicated so in table 3. Most of the variation in moisture content with depth seems to be related mainly to the changes in particle-size distribution. Core hole 6S/2W-24C7 was the only one for which moisture content was determined in the field. Moisture content was determined at the Hydrologic Laboratory in Denver for some of the core samples from the Los Banos-Kettleman City area, but the results are not reported here because analysis data indicated that appreciable moisture had been lost from some of the samples tested. Table 3—Natural moisture content of sediments from core hole 6S/2W-24-C7, Santa Clara County [Moisture determinations by B. H. Meade] Sample depth (feet below surface, as logged) Average moisture content (percent of dry weight) Different rep determ Percent of dry weight ,c between tlcate Inatlons Percent average moisture CQntent 42.0 22.8 0.3 1.3 50db 23.1 1.0 4.3 72 23.7 .5 2.1 91± 27.9 .3 1.1 100± 25.2 .4 1.6 113.3 30.8 .7 2.3 121.1± 30.1 1.4 4.7 127± 27.2 1.1 4.1 142.2± 1 27. 5 2.4 8.7 152 27.0 .2 .7 160.9± 26.2 .3 1.1 178.9± 23.5 .6 2.6 180.9± 27.0 1.1 4.1 192± 21.1 .4 1.9 210.6 24.9 .3 1.2 212.4 24.6 1.3 5.3 222.8 30.5 1.3 4.3 228.9 21.2 .2 .9 236.5 3 23.0 2.3 10.0 259 26.6 .1 .4 307.4 22.3 .2 .9 312.7 20.1 .1 .5 330.5 20.6 .0 .0 340.2 23.2 .6 2.6 See footnotes at end of table.PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A31 Table 3.—Natural moisture content of sediments from core hole 6SI2W-24C7j Santa Clara County—Continued Sample depth (feet below surface, as logged) Average moisture content (percent of dry weight) Differen rep detem Percent of dry weight ce between licate ilnatlons Percent average moisture content 348.4 24.9 1.1 4.4 408.3 22.2 .1 .5 419.5 16.9 .1 .6 443.9=fc 25.4 .2 .8 447.1± 23.3 .3 1.3 459.4± 22.2 .6 2.7 462.9± 1 20. 8 5.8 27.9 523.3± 29.8 1.1 3.7 526± 29.0 . 1 .3 544.9 21.0 .1 .4 555.2 17.3 1.1 6.4 563.7 21.7 .7 3.2 574.8 22.7 1.0 4.4 606.4 20.9 1.2 5.7 619.1 26.5 .1 .4 633.1 >34.8 5.5 15.8 646.2 >42.0 2.8 6.7 656 >37.6 2.9 7.7 664 >39.6 2.0 5.1 716 >25.1 1.5 6.0 721.8 17.8 .4 2.2 731.1 23.7 .3 1.3 742 23.7 .1 .4 756 >22.6 1.5 6.6 772.9 24.4 .5 2.0 789.4 >44.8 2.9 6.5 813± >40.2 3.2 8.0 825.4 37.9 1.7 4.5 835.8 3 26.3 .6 2.3 842.7 25.9 .4 1.5 854.6 22.0 .3 1.4 866.4 23.5 .0 .0 873.8 16.9 .2 1.2 882.1 19.3 1.0 5.2 901.3 21.4 .1 .5 911.3 27.2 1.3 4.8 924.6 30.7 .6 2.0 930.3 19.7 .4 2.0 937.6 >31.2 2.6 8.3 959.4 23.4 .1 .4 966.9 20.3 .3 1.5 977.5 23.6 .8 3.4 994 >24.6 6.8 27.6 > Must be used with caution because difference between values obtained for the 2 tests is unduly large. 3 Of the 2 samples from this depth, 1 contained many hard calcite concretions and the other contained only a few. Moisture content of latter, 24.2 percent, is probably more significant than the average value of 23.0 percent. 3 Although sample was a loose medium-grained sand, value is probably accurate because moisture content was measured as soon as the core was extracted from the barrel. ATTERBERG LIMITS AND INDICES The Atterberg limits and indices determined by the Hydrologic Laboratory for selected fine-textured sam- ples from seven core holes are presented in tables 4 and 6 (p. AS 5). Table 4 summarizes the range in values of consistency for each of the limits and indices for each core hole. Table 6 presents the values of the limits and indices for each sample tested. The Earth Laboratory of the U.S. Bureau of Reclamation determined the liquid limit, plastic limit, and plasticity index for 73 samples from six core holes, These data are presented in table 8 (p. A60). The rest of the discussion of Atterberg limits and indices concerns only the samples tested by the Hydrologic Laboratory. Predominantly fine textured samples to be tested by the Hydrologic Laboratory were selected by visual inspection. Becuase the Atterberg limits describe properties of the fine part of a sample, presenting Atterberg limit data for samples which are predominantly coarse textured could be misleading. When the influence which the limits of consistency have on the behavior of a sample is being judged, the percentage of the sample tested must be considered. Table 6 includes a column which shows the percent (by weight) of the total sample which passed a No. 40 sieve (0.42-mm openings) and was therefore the part of the sample tested for Atterberg limits. Most of these Atterberg limits and indices are not directly applicable to the study of subsidence and compaction of sediments under increased effective overburden load, but they do furnish a rough comparative measure of the way in which fine-grained sediments respond to a decrease in moisture content as they pass from the liquid to the solid state. Because the values of these indices are related to texture, composition, clay content, and type of clay minerals present, they may be of qualitative use in comparing the fine-textured clayey deposits in these three areas to each other and to fine-textured sediments in other areas for which Atterberg indices have been obtained but for which the clay content and the type of clay minerals present are not known. Table 4.—Range in values of consistency 14/13-11D1 16/15-34N1 19/17-22J.2 23/25-16N1 24/26-36A2 6S/2W-24C7 7S/1E-16C6 Liquid limit _ 25-82 30-76 26-65 22-63 22-107 26-68 24-50 Plastic limit _ 18-46 23-59 21-44 21-48 18-62 18-32 18-25 Shrinkage limit _ . _ _ 4-31 7-31 9-32 9-24 5-44 8-20 14-19 Plasticity index . _ 1-48 4-22 1-27 3-18 4-59 5-38 3-25 Flow index ____ 4-42 7-32 5-26 5-14 4-32 4-17 2-7 Toughness index 0. 2-3. 6 0. 2-2. 2 0. 1-2. 2 0. 2-2. 2 0. 5-3. 4 0. 9-3. 3 1. 5-5. 7 Shrinkage index 0-36 2-49 1-32 5-29 0-46 1-18 3-8 Shrinkage ratio 1. 4-2. 3 1. 4-2. 0 1. 4-2. 0 1. 6-2. 0 1. 2-2. 1 1. 7-2. 2 1. 8-2. 0 Volumetric shrinkage _ 4-168 12-122 13-101 5-75 7-166 14-103 11-56 Linear shrinkage _ _ 1-28 4-23 4-21 2-17 2-28 4-21 3-14 263-524 0-67—6A32 MECHANICS OF AQUIFER SYSTEMS LIQUID LIMIT Data correlating liquid limits determined by a single-point method with liquid limits determined by the standard multiple-point method were presented by Morris and Johnson (1959) and showed that a good correlation existed. However, only the multiple-point data are reported in table 6. The liquid limits for core-hole samples from the Los Banos-Kettleman City area range from 25 to 82 and, except for a few cores taken from the thick section of the Corcoran Clay Member in core hole 14/13-llDl, show general similarity between core holes (pi. 12). The Corcoran Clay Member in this core hole had liquid limits ranging from 67 to 82. The liquid limits for the core-hole samples from the Tulare-Wasco area range from 22 to 107 (pi. 13). The Corcoran Clay Member in core hole 23/25-16Nl had liquid limits of 56 and 63. Most samples from the upper Pliocene marine strata had even higher liquid limits. The liquid limits for the core-hole samples from the Santa Clara Valley range from 24 to 68 (pi. 14). Samples from core hole 6S/2W-24C7 had generally higher values. PLASTIC LIMIT In materials in contact with the atmosphere, the voids remain saturated down to the plastic limit, at which time air begins to enter the soil mass. The plastic limits ranged from 18 to 59 for all the fine-textured core-hole samples from the Los Banos-Kettleman City area, the highest plastic limits being for samples of the Corcoran Clay Member. The plastic limits ranged from 18 to 62 for all core-hole samples tested from the Tulare-Wasco area. The plastic limits ranged from 18 to 32 for the clayey core-hole samples tested from the Santa Clara Valley. The liquid and plastic limits (moisture content, in percent) for samples from all core holes are plotted against clay-size particles, in percent, in figure 18. As shown by the trend lines drawn in figure 18, both limits tend to increase with an increase in clay content, the liquid limit increasing at a greater rate than the plastic limit. The trend lines shown in figure 18 were plotted from equations derived by computer in the U.S. Geological Survey Computation Branch. The equations are of the form y=a-\-bx, in which y represents the moisture content (w), x represents the clay content (C), both in percent, and a and b are constants. In figure 18A the equation of the liquid-limit trend line is wi=28.1 + 0.53(7 and that of the plastic-limit trend line is w„= 26.8+0.17(7. In figure 18J5 the equation of the liquid-limit trend line is wL=\2>.5 + 1.3(7and that of the plastic-limit trend line is wp= 17.3 + 0.54(7. In figure 18(7 the equation of the liquid-limit trend line is wL= 14.0+ 0.72(7 and that of the plastic-limit trend line is wp= 14.7+0.22(7. The equations of all these trend lines are for samples having clay content based on the percentage of particles less than 0.004 mm in size. Figure 18Z7 shows trends which are composites of all the samples shown in figures 18A-(7. The equation of line 1, the liquid-limit trend line for clay sizes less than 0.002 mm, is ^=27.8 + 0.71(7. The equation of line 2, the liquid-limit trend line for clay sizes less than 0.004 mm, is wz,=25.8+0.60(7. The equation of line 3, the plastic-limit trend line for clay sizes less than 0.002 mm is wp=25.6 + 0.21(7. The equation of line 4, the plastic-limit trend line for clay sizes less than 0.004 mm is w„=24.5+0.19(7. Lines 1 and 3 are included to show the relation between liquid and plastic limits and percent of clay-size particles if 0.002 mm is chosen as the upper limit of the clay-size range. The value of the standard error for each trend line was obtained from the computer. The pairs of dashed lines which parallel each trend line designate two standard errors on either side of the trend line. The probability is 19 to 1 that, for a given value of clay content (in percent), the observed liquid limit or plastic limit will lie within the interval between the dashed lines. PLASTICITY INDEX The difference between the liquid and plastic limits, or the plasticity index, represents the range of moisture content within which a sediment mass will remain in the plastic state. Plastic clay normally has a plasticity index of 15 or greater, and clean sand an index close to 0. The fine-textured samples from the Los Banos-Kettleman City area had plasticity indices ranging from 1 to 48, and most sediments from core hole 14/13—11 Dl had a higher plastic range than those from the other two holes. The samples of the Corcoran Clay Member from core hole 14/13—11 Dl had a particularly high range of plasticity indices, from 31 to 40. The plasticity indices of core-hole samples from the Tulare-Wasco area ranged from 2 to 58. The two samples of the Corcoran Clay Member from core hole 23/25-16Nl had a plasticity index of 38 and 48, respectively. The fine-textured samples from the Santa Clara Valley had plasticity indices ranging from 3 to 38. The moisture content difference between the liquid-limit trend line and the plastic-limit trend line in each part of figure 18 represents the average plasticity index for different clay contents. Casagrande (1948, p. 919) devised a chart on which the liquid limit is plotted against the plasticity index and used it for rough classification of soils. Points representing different samples from the same stratum or fine-grained deposit plot as a straight line that is roughly parallel to an “A” line, an empirical boundaryMOISTURE CONTENT, IN PERCENT OF DRY WEIGHT PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A33 A. LOS BANOS-KETTLEMAN CITY AREA C. SANTA CLARA VALLEY B. TULARE-WASCO. AREA 1 1 <^11 ^ S' / - ‘ > w r 1 gggs i 1 1 0 20 40 60 80 CLAY-SIZE PARTICLES, IN PERCENT D. Figure 18.—Effect of clay content on liquid limit and plastic limit.A34 MECHANICS OF AQUIFER SYSTEMS between typically inorganic clays above and plastic organic soils below the line. The higher a sample plots on this chart at a given liquid limit, the greater its toughness and dry strength and the lower its permeability and rate of volume change. Figure 19 shows plasticity charts of the Casagrande type on w'hich the data for all samples tested by the Hydrologic Laboratory have been plotted. The sediment-classification names used in figure 22 are different from the Shepard classification names used earlier in this report. As shown by figure 19A, most of the Atterberg limits of the sediments from all core holes in the Los Banos-Kettleman City area fall in a rather narrow band beneath the “A” line, in the region typical for either organic or inorganic silt and silt-clay or micaceous and diatom aceous fine sandy and silty soils, elastic silt, and organic clay. A few samples are above the “A” line and are classified as inorganic clay of medium and high plasticity. Atterberg limits of nearly all the fine-textured samples from core hole 14/13-1 lDl fall near the “A” line of the chart, the samples of the Corcoran Clay Member being the highest in plasticity (upper right of the chart). Atterberg limits of most of the fine-textured sediments from both core holes in the Tulare-Wasco area fall in a rather narrow band near the “A” line (fig. 19B) in the region typical for organic or inorganic silt and silt-clay of low plasticity, inorganic clay of low to medium plasticity, and organic clay of medium to high plasticity. All samples having liquid limits greater than 50 are from core hole 24/26-36A2, except two samples of the Corcoran Clay Member from core hole 23/25-16N1. Samples of the Corcoran Clay Member have a MH .classification (fig. 19A) in the Unified Soil Classification system, and samples from the upper Pliocene marine strata are classified predominantly as OH and OL. The continental deposits from the Sierra Nevada are predominantly of CL and ML classification. Atterberg limits of most of the fine-textured sediments tested from both core holes in the Santa Clara Valley fall in a rather narrow band above the “A” line (fig. 19 G), in the region typical for inorganic clay having low to medium plasticity, gravelly clay, sandy clay, silty clay, lean clay, and inorganic clay having high plasticity. All samples that fall on the right side of the line through a liquid limit of 50 are from core hole 6S/2W-24C7. 70 60 50 40 30 20 10 7 4 0 —i----------1-------1-------1-------r Comparing soils at equal liquid limit: toughness and dry strength increase with increasing plasticit; / index (CH) Inorganic clays of high plasticity, fat clays • —i r 14/13-11D1 + 19/17—22J1.2 ® Corcoran Clay Member of Tulare Formation (CL) Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays (0L) Organic silts and silt clays of low plasticity (OH) Organic clays of medium m to high plasticity Vo* A’ +* "5I* - -+ (MH) Micaceous and diatoma-® ceous fine sandy and silty soils, elastic silts °“(ML)Inorganic silts and very fine sands, rock flour, silty or clayey fine sands with slight plasticity LOS BANOS-KETTLEMAN CITY AREA Figure 19.—Unified soil classification plasticity for core-hole samples. (ASTM, 1958, p. 188-189.) SHRINKAGE LIMIT The shrinkage limit represents the. minimum moisture content needed to fill the pores when the soil is at the minimum volume that it will attain by drying. The shrinkage index represents the range of moisture content in which a sediment mass remains in a semisolid state of consistency. Shrinkage limits for the fine-textured samples from the Los Banos-Kettleman City area ranged from 4 to 32 percent and shrinkage indices ranged from 0 to 49 (table 6). Shrinkage limits for the fine-textured samples from the two core holes in the Tulare-Wasco area ranged fromPROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A35 5 to 44 percent, and shrinkage indices ranged from 0 to 46 (table 6). The samples from core hole 23/25-16N1 have, in general, higher shrinkage indices than samples from corresponding depths in core hole 24/26-36A2. Shrinkage limits for the fine-textured samples from the Santa Clara Valley ranged from 8 to 20 percent, and shrinkage indices ranged from 1 to 18 (table 6). Samples from two zones in core hole 6S/2W-24C7 had high shrinkage indices. These zones are at 140-223 feet, where the shrinkage indices range from 10 to 15, and at 715-959 feet, where the shrinkage indices range from 9 to 18. VOLUMETRIC SHRINKAGE The volumetric shrinkage, or the total volumetric change possible as the moisture content decreases from the liquid limit to the shrinkage limit, compared to depth below land surface, is illustrated for the Los Banos-Kettleman City area in plate 12, and values of volumetric and linear shrinkage are provided in table 6. Plate 12 shows that the volumetric-shrinkage values for the sediments from core holes 16/15-34N1 and 19/17— 22J1, 2 were similar but values for core hole 14/13-1 ID 1 were generally higher. However, a general decrease in volumetric shrinkage values may be noted southward from core hole 14/13-llDl to 19/17—22J1, 2. The volumetric shrinkage ranged from 4 to 168 percent. The volumetric-shrinkage values are generally high for samples from the Corcoran Clay Member in the Tulare-Wasco area, and are especially high for some samples from the upper Pliocene marine strata. The volumetric shrinkage is compared to depth below land surface in plate 13, and values of volumetric, as well as linear, shrinkage are provided in table 6. Plate 13 shows that the volumetric shrinkage for sediments from core hole 23/25-16N1 is generally higher and exhibits greater variation than the volumetric shrinkage for comparable depths from core hole 24/26-36A2. Volumetric shrinkage for fine-textured samples from core hole 23/25-16N1 ranges from 5 to 75 and averages 34. Volumetric shrinkage for samples above 750 feet in core hole 24/26-36A2 ranges from 7 to 87 and averages 28; below 750 feet, however, it ranges from 22 to 166 and averages 86. Thus, the average volumetric shrinkage for samples from the upper Pliocene marine strata is about three times as great as for the overlying continental sediments. The volumetric shrinkage is compared to depth below land surface for the fine-textured samples from the Santa Clara Valley in plate 14, and values of volumetric and linear shrinkage are provided in table 6. Plate 14 shows that the volumetric shrinkage of sediments from core hole 6S/2W-24C7 is generally higher and exhibits greater variation than the volumetric shrinkage of sediments from core hole 7S/1E-16C6. Volumetric shrinkage of fine-grained samples from above 700 feet in core hole 6S/2W-24C7 ranges from 14 to 76 and averages 43; below 700 feet it ranges from 50 to 103 and averages 88. Volumetric shrinkage of samples from core hole 7S/1E-16C6 ranges from 11 to 56 and averages 32. Johnson and Morris (1962b) showed that the volumetric shrinkage in a sediment mass is proportional to the percentage of clay-size particles in that sediment, a 10-percent increase in clay content causing an approximate increase of 20-30 percent in volumetric shrinkage. Figure 20 shows the relation between volumetric shrinkage and the percentage of clay-size particles. Equations of the form y—a+bx were calculated in the Geological Survey Computation Branch for the relationships between values for volumetric shrinkage and for clay content (both <0.004 and <0.002 mm). In these equations, y represents volumetric shrinkage (+,), x represents clay content ((7), both in percent, and a and b constants. The computer also calculated the standard error for each relation. Figure 20A shows the relation between volumetric shrinkage and the percentage of clay-size particles (both <0.004 and <0.002 mm) for the tested corehole samples from the Los Banos-Kettleman City area. The two trend lines are plotted from the equations furnished by the computer. The pairs of dashed lines parallel to the trend lines designate two standard errors (as calculated by the computer) on either side of the trend lines. The probability is 19 to 1 that, for a given clay content in percent, the observed volumetric shrinkage will lie within the interval designated by the dashed parallel lines. Figure 20B shows these relations for the tested core-hole samples from the Tulare-Wasco area, and figure 20(7 shows these relations for the tested core-hole samples from the Santa Clara Valley. Figure 20D is a composite showing the relations calculated by the computer for all the samples included in figures 20 A-C. For samples from the Los Banos-Kettleman City area (fig. 20A) the equation for the trend line using clay sizes less than 0.002 mm is +,=4.4+1.9(7, and the equation using clay sizes less than 0.004 mm is Vs=0.15+1.5(7. For samples from the Tulare-Wasco area (fig. 201?) the equation for the trend line using clay sizes less than 0.002 mm is +,= —3.5+2.5(7, and the equation using clay sizes less than 0.004 mm is +,= —15.2+2.4(7. For samples from the Santa Clara Valley (fig. 20(7) the equation for the trend line using clay sizes less than 0.002 mm is +,= —15.2 + 2.1(7, and the equations using clay sizes less than 0.004 mm is +,=—9.8+1.5(7. For all samples Tested (fig. 20D), the equation for the trend line using clay sizes less than 0.002 mm is +,=3.5+ 1.9(7, and the equation using clay sizes less than 0.004 mm is +,=0.12 + 1.5(7.A36 MECHANICS OF AQUIFER SYSTEMS o < * z CE X 0 20 40 60 80 100 B. TULARE-WASCO AREA 0 20 40 60 80 100 •CLAY-SIZE PARTICLES, IN PERCENT C. SANTA CLARA VALLEY D. COMPOSITE OF ALL SAMPLES TESTED Figure 20— Relation of volumetric shrinkage to clay content for samples from core holes. TOUGHNESS INDEX The toughness index is considered an expression of the relative toughness or shearing strength at the plastic limit. It generally falls between 1 and 3 for most clays. A sediment is friable at the plastic limit if this index is less than 1. Plate 12 and table 6 show that samples from core holes 16/15-34N1 and 19/17-22J1, 2 in the Los Banos-Kettleman City area had a toughness index ranging from 0.1 to 2.2, the samples from 16/15-34N1 generally having a toughness index less than 1 and samples from 19/17-22Jl, 2 generally having a toughness index greater than 1. The toughness index of samples from core hole 14/13-1 lDl was somewhat higher—ranging from 0.2 to 3.6 and generally greater than 1. The Corcoran Clay Member from core hole 14/13-llDl had a toughness index close to 3. Plate 13 and table 6 show that samples from core hole 23/25-16Nl in the Tulare-Wasco area had aPROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A37 toughness index ranging from 0.2 to 2.2 and the samples from core hole 24/26-36A2 had a toughness index ranging from 0.5 to 3.4. The toughness index of samples from core hole 24/26-36A2 was generally higher in samples taken below 750 feet. The Corcoran Clay Member from core hole 23/26-16N1 had a toughness index averaging 1.6. Plate 14 and table 6 show that the samples from core hole 6S/2W-24C7 in Santa Clara Valley had a toughness index ranging from 0.9 to 3.3 and the samples from core hole 7S/1E-16C6 had a toughness index ranging from 1.5 to 5.7. The toughness index for samples from core hole 7S/1E-16C6 was generally higher than the toughness index for samples from core hole 6S/2W-24C7. ACID SOLUBILITY Calcite and, to a lesser extent, dolomite, and possibly magnesite, are the carbonates usually occurring in significant quantities in the soils of arid regions. A high carbonate content at sonte depth in the subsurface sediments may be indicative of an old buried soil horizon. The percentage of material dissolved out of a sample by cold dilute hydrochloric acid is reported as acid solubility in table 7. For reasons discussed on p. Al6, the percentage of acid-soluble material is only an approximate measure of the calcium carbonate content of the samples tested. Test results for selected samples from the three core holes in the Los Banos-Kettleman City area (table 7; pi. 12) indicate that acid solubility ranged from about 1 to 16 percent, averaging 5 percent for 60 samples from core hole 14/13—1 lDl, 7 percent for 59 samples from core hole 16/15-34N1, and 8 percent for 21 samples from core hole 19/17-22Jl, 2. No consistent trend for acid solubility and depth was apparent; core hole 16/15-34N1 showed a general decrease with depth, and core hole 14/13-llDl showed markedly lower values from 700 to 1,350 feet. In core hole 14/13-1 lDl, the highest acid solubility (nearly 15 percent) was found at a depth of 1,397 feet, in a hard, brittle clay logged from 1,348 to 1,455 feet in depth. Test results for selected samples from the two core holes in the Tulare-Wasco area (table 7; pi. 13) indicate that acid solubility ranged from 0.4 to 20.8 percent, averaging 6 percent for 16 samples from core hole 23/25-16N1 and 5 percent for 95 samples from core hole 24/26-36A2. No consistent trend for acid solubility and depth was apparent, but three zones of high acid solubility were found in core hole 24/26-36A2, at depths of approximately 400, 750, and 1,750 feet. Test results for selected samples from the two core holes in the Santa Clara Valley (table 7; pi. 14) indicate that acid solubility ranged from 6.5 to 19.1 percent, averaging 10 percent, for 30 samples from core hole 6S/2W-24C7 and ranged from 11.0 to 18.4 percent, averaging 14 percent, for 10 samples from core hole 7S/1E-16C6. No consistent trend of acid solubility with depth was apparent, but generally higher acid solubilities were found in 7S/1E-16C6 than in 6S/2W-24C7. GYPSUM CONTENT Gypsum (CaS04-2H20) is often found in the soil materials of arid regions. It occurs either in the soil zone, owing to precipitation of calcium and sulfate during salinization, or at any depth, owing to the composition of the sedimentary deposits. Reitemeier (1946) showed that precise determination of gypsum content is difficult because several factors other than the solution of gypsum in water may influence the amounts of calcium and sulfate extracted from gypsiferous soil materials. Those factors are (1) the solution of calcium and sulfate from sources other than gypsum and (2) exchange reactions in which soluble calcium replaces other cations, such as sodium and magnesium. In earlier studies related to near-surface subsidence in the Los Banos-Kettleman City area, gypsum was found in samples from shallow core holes (Bull, 1964, p. 61). In areas of active or potential near-surface subsidence, gypsum content in two core holes 300 feet deep ranged from 0.1 to 4.8 percent in 85 samples (Inter-Agency Committee, 1958, pis. 18, 23). Data in table 7 indicate that no gypsum was found in selected samples tested from core holes 14/13-llDl and 16/15— 34N1. Only three of the samples tested from core hole 19/17—22J1, 2 had a small amount «1 percent) of gypsum. These samples, taken at depths of approximately 1,805, 1,874, and 1,957 feet, had gypsum contents of 12.7, 4.0, and 7.6 tons per acre-foot of soil, respectively. No gypsum was found in samples tested from core hole 23/25-16N1 in the Tulare-Wasco area (table 7). Only 11 of the samples tested from core hole 24/26-36A2 contained any gypsum, and all except 3 of these had less than 1 percent gypsum (20 tons per acre-foot is considered equal to 1 percent gypsum). These samples were from depths of 698 to 1,892 feet and had gypsum contents ranging from 0.3 to 24.4 tons per acre-foot of soil. No gypsum was found in samples tested from either core hole 6S/2W-24C7 or 7S/1E-16C6 in the Santa Clara Valley (table 7). CONSOLIDATION As one phase of the research on subsidence and compaction of aquifer systems, laboratory consolidation tests were made on representative cores from eightA38 MECHANICS OF AQUIFER SYSTEMS core holes. These consolidation tests were made in the Earth Laboratory of the U.S. Bureau of Reclamation at Denver, Colo. The visual classification, including the group symbol Of the Unified Soil Classification (fig. 19; see also ASTM, 1958, p. 188-189), and Atter-berg limits (also determined by the Bureau of Reclamation) for the samples tested for consolidation are listed in table 8. The consolidation-tests results are summarized in table 9. The results of these consolidation tests are being utilized in interpretive reports of the Geological Survey to compute compaction in the confined aquifer system in response to the known decline in artesian head. The method has been described by Miller (1961); it is a refinement of a technique outlined by Gibbs (1959, p. 4-5) based upon Terzaghi’s theory (1943) of consolidation and the use of one-dimensional consolidation tests. Consolidation-test curves for samples tested by the Bureau of Reclamation, composited for each of the eight core holes, are shown in plate 11. Plate 11A-D shows, in general, that in the Los Banos-Kettleman City area the Corcoran Clay Member has a greater unit consolidation potential than any of the other sediments. The compaction of the Corcoran Clay Member, however, has contributed very little to the total subsidence to date (Miller, 1961, p. B57) because, where the Corcoran is thick, water moves out very slowly owing to the Corcoran’s low vertical permeability. Where the Corcoran is thin and more permeable, it forms only a small percentage of the water-bearing section. Consolidation curves for the Corcoran Clay Member are generally steep in the load range 200-1,000 psi and indicate that the clay is normally loaded and has not been precompressed. Therefore the clay has only partly completed its potential consolidation at the present time and at the present artesian pressure. Initial void ratios of samples tested from core hole 12/12-16H1 ranged from 0.55 to 1.51, and void ratios of the seven samples tested at 1,000 psi ranged from approximately 0.33 to 0.66 (pi. 11A). Initial void ratios of samples tested from core hole 14/13-1 lDl ranged from 0.58 to 1.19, and void ratios at 1,000 psi ranged from 0.38 to 0.67. Initial void ratios of samples tested from core hole 16/15-34N1 ranged from 0.52 to 1.09, and void ratios at 1,000 psi ranged from 0.37 to 0.67. Initial void rttios of samples tested from core hole 19/17—22J1, 2 ranged from 0.53 to 0.96, and void ratios at 1,000 psi ranged from 0.37 to 0.58. Several zones of high compressibility were indicated by the consolidation tests. Core holes 16/15-34N1 and 19/17—22J1, 2 in the southern part of the Los Banos-Kettleman City area have considerable thicknesses of highly compressible silty clay beds. The Corcoran Clay Member is thinner and less representative in these holes than in core holes 12/12-16H1 and 14/13-llDl in the northern part of the area, where it is highly compressible. The consolidation tests (pis. 11E, F) indicate that in the Tulare-Wasco area, the Corcoran Clay Member, which is the principal confining layer throughout much of the valley, is the only highly compressible clay in the continental deposits penetrated by the two core holes. The Corcoran is only 16 feet thick in core hole 23/25-16N1 and is nonexistent in core hole 24/26-36A2. A large thickness of firm upper Pliocene marine claystone was penetrated in core hole 24/26-36A2 between depths of 744 and 1,641 feet; in general, these sediments have a greater unit consolidation potential than any of the other sediments tested from the two core holes in the Tulare-Wasco area. The consolidation tests of the claystone indicate preconsolidation to approximately 700-800 psi and, for the respective depths of about 900-1,500 feet, suggest normal loading of the sediments (pi. IIP). Initial void ratios of the samples from core hole 23/25-16N1 ranged from 0.52 to 1.10 and void ratios at 1,000 psi ranged from approximately 0.30 to 0.60. Samples tested from core hole 24/26-36A2 had initial void ratios ranging from 0.46 to 1.47, and void ratios at 1,000 psi ranged from approximately 0.30 to 1.25. The consolidation tests of cores from the Santa Clara Valley indicate only moderately compressible silty clay in contrast to the highly compressible Corcoran Clay Member found in the Los Banos-Kettleman City area. Core-hole samples exhibit more uniform compression indices and initial void ratios than the samples from the other two areas (table 8; pi. 11 <9, H). None of the Santa Clara Valley samples produced such steep void-ratio versus log-load curves as did samples of the Corcoran Clay Member from the San Joaquin Valley. Initial void ratios of the samples from core hole 6S/2W-24C7 ranged from 0.55 to 0.82 and void ratios at 1,000 psi ranged from 0.33 to 0.50. The samples tested from core hole 7S/1E-16C6 had initial void ratios ranging from 0.52 to 0.69 and void ratios at 1,000 psi ranging from 0.28 to 0.48. Terzaghi and Peck (1948, p. 66) stated that values for the compression index, Cc, of ordinary clays of medium or low sensitivity can be estimated roughly from the liquid limit, wL, by use of the following equation: ^=0.009(^-10). Thus, for such clays, values of Cc can be estimated by making no tests other than liquid-limit tests. Terzaghi and Peck also, however, concluded that the equationPROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A39 furnishes merely a lower limiting value for the compression of an extra-sensitive clay—the actual compression may be several times greater. For comparison, the values of the compression index, Cc, obtained by the Bureau of Reclamation from the above equation and from consolidation tests are given in table 9. Many of the estimates computed from the liquid limit are close to the values obtained from consolidation tests but a few differ greatly. Figure 21 shows the relation of liquid limit to the compression index, Cc, for samples from six core holes. Both the liquid limit and the compression index were determined experimentally by the Bureau of Reclamation. A solid line in each of the four parts of the figure provides a graphical representation of the Terzaghi and Peck equation. Thus, the values of liquid limit and compression index, determined experimentally for the core hole samples, can be compared with values derived from the equation. In part D of figure 21, the regression lines determined by computer for the actual data for samples from the San Joaquin and Santa Clara Valleys are compared with the regression line for the data from Terzaghi and Peck (1948, p. 66). The equation for the regression line for samples from San Joaquin Valley is Cc=0.015 (wL — 20), and for samples from the Santa Clara Valley is C,c=0.0033(Wi+30), both of which compare with the equation of Cc=0.009(wL— 10) for data from Terzaghi and Peck. The pairs of dashed or dotted lines parallel to the trend lines in figure 21D designate the zone in which the probability is 19 to 1 that, for a given value of liquid limit, the observed compression index will lie. The closer plot to their trend line of data for samples from Z o <0 CO A. LOS BANOS-KETTLEMAN CITY AREA 20 40 60 80 B. TULARE-WASCO AREA 120 LIQUID LIMIT D. COMPARISON OF TERZAGHI AND PECK EQUATION WITH EQUATIONS CALCULATED BY COMPUTER FOR ALL SAMPLES SHOWN IN A, B, AND C Figure 21.—Relation between liquid limit and compression index for samples from core holes.A40 MECHANICS OF AQUIFER SYSTEMS core holes in the Santa Clara Valley indicate better correlation than do the plot of data for samples from the San Joaquin Valley. The dashed lines for the San Joaquin Valley are so far apart, owing to the wide scatter of the plotted points, that the computed equation for the data for samples from that area is not particularly significant and should be used for approximate comparative purposes only. The permeability for each sample tested for consolidation by the Bureau of Reclamation is presented in table 9. The permeability was calculated from consolidation data or was determined while the sample was under load in the consolidation apparatus and after consolidation was complete. Permeability values are presented for various load ranges, the value given representing permeability at maximum load. The units of permeability are expressed in feet per year (ft per yrX0.0205 = gpd per sq ft). The Unified Soil Classification group symbol is also listed in table 9 for each sample tested for consolidation by the Bureau of Reclamation (ASTM, 1958, p. 188-189). SUMMARY OF LABORATORY ANALYSES RESULTS BY AREA Results of the tests on physical and hydrologic properties of the various core-hole samples have thus far been discussed by type of test so that the physical characteristics of the deposits in the three areas could be compared. In this section the results of the laboratory analyses are summarized briefly by individual subsidence area. It must be emphasized again that the laboratory samples described in this report represent, primarily, the fine-textured materials from the core holes; the coarse sediments (loose sand and gravel) were not recovered in the coring operation. Therefore any ranges and averages cited are not representative of the sediments as a whole. However, because compaction due to artesian-head decline occurs chiefly in the fine-textured deposits, their physical and hydrologic properties are the most pertinent to the study of land subsidence and compaction of aquifer systems. The data being utilized directly in the interpretive reports of the Geological Survey are the results of the particle-size analyses and of the tests for the specific gravity, unit weight, porosity and void ratio, and consolidation. The tests for acid solubility and gypsum content were made to facilitate study of the environment of deposition and diagenesis of the sediments. Atterberg limits and indices, in conjunction with the particle-size analyses, illustrate the effect of the percentage of clay-size particles on engineering properties and furnish a qualitative index to the compressibility characteristics of the sediments. The tests for permeability should prove useful to other related studies. The analytical results on these samples furnish a substantial body of data on the physical and hydrologic properties of thick sequences of unconsolidated to semiconsolidated sediments. LOS BANOS-KETTLEMAN CITY AREA The results of the tests for the most pertinent properties of samples analyzed from three core holes—14/ 13-llDl, 16/15-34N1, and 19/17-22J1, 2—have been plotted on plate 12 in conjunction with the electric (self-potential and resistivity) logs for each core hole. Permeability, clay content, dry unit weight, specific gravity, porosity and void ratio, Atterberg limits, volumetric shrinkage, toughness index, acid solubility, and gypsum content are shown. Plate 12 thus serves as a graphic summary of most of the analyses made at the U.S. Geological Survey Hydrologic Laboratory on samples from these three core holes. The number of analyses made by the Bureau of Reclamation Earth Laboratory for core hole 12/12-16Hl was so small that the data were not plotted. However, the sample depths, the electric log, graphic log, and lithologic description for this core hole are presented in plate 1A for comparison with the other three core holes and for use with tables 8 and 9. The data for the three core holes for which samples were tested by the Hydrologic Laboratory are so arranged in plate 12 that the northernmost hole is located at the top of the figure and the southernmost hole is at the bottom. The total subsidence from 1932 to 1956 was 8 feet at core hole 12/12-16Hl, 13 feet at 14/13—11 Dl, 7 feet at 16/15-34N1, and 12 feet at 19/17-22J1, 2. Certain broad trends are evident from a study of plate 12 or the tables. The sediments cored were predominantly fine textured and primarily of clayey-silt or silty-clay types in the Shepard classification. According to the Unified Soil Classification plasticity chart, the sediments from all three core holes are Jas-sified as inorganic silt and silt-clay or micaceous and diatomaceous silt and clay. The samples had median diameters ranging from 0.001 to 0.520 mm, samples from the Corcoran Clay Member of the Tulare Formation being near the lower limit. The sorting coefficient ranged from 1.1 to 17.2 and averaged about 3, and the log quartile deviation ranged from about 0.061 to 1.236. The permeability of samples from these core holes ranged from 0.00007 to 370 gpd per sq ft. The greatest percentage of samples had permeabilities ranging from 0.0001 to 0.001 gpd per sq ft. The ratio of horizontal to vertical permeability averaged 2.7. The Corcoran Clay Member had consistently low permeability.PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A41 The specific gravity ranged from 2.43 to 2.79 and averaged 2.69. Samples that were taken between depths of approximately 1,750 and 1,950 feet in core holes 16/15-34N1 and 19/17-22Jl,2 had the lowest values. The dry unit weight ranged from 1.10 to 1.95 g per cc (68.6 to 121.7 lb per cu ft), and the porosity from approximately 28 to 56 percent. The void ratio ranged from 0.38 to 1.25. Samples of the Corcoran Clay Member had the highest porosities and the lowest dry unit weights. The liquid limits ranged from 25 to 82 and showed similarity between holes, except for a few cores taken from the thick section of the Corcoran Clay Member in core hole 14/13-1 lDl for which the liquid limit ranged from 67 to 82. The plastic limit ranged from 18 to 59, and the shrinkage limit from 4 to 32. The plasticity indices ranged from 1 to 48, sediments from core hole 14/13-1 lDl having a higher plastic range. Shrinkage indices ranged from 0 to 49. Volumetric shrinkage was similar for samples from all core holes although a general decrease was noted from north to south. Samples from core holes 14/13-llDl and 19/17— 22Jl, 2 had a toughness index ranging from 0.1 to 3.6 and usually greater than 1. For samples from hole 16/15-34N1 the index was lower, ranging from 0.2 to 2.1, and usually less than 1. The Corcoran Clay Member had a toughness index close to 3. The acid solubility ranged from 1 to 16 percent and averaged 5, 7, and 8 percent for samples from core holes 14/13-llDl, 16/15-34N1, and 19/17-22Jl, 2, respectively. The gypsum content was 0 in selected samples tested from core holes 14/13-1 lDl and 16/15-34N1 and less than 1 percent in samples taken at three depths between 1,800 and 1,960 feet in core hole 19/17-22Jl, 2. Consolidation-test curves show, in general, that the Corcoran Clay Member has a greater unit consolidation potential than any of the other sediments. Because of its low vertical permeability, however, the compaction of the Corcoran Clay Member has contributed very little to the total subsidence to date (Miller, 1961, p. B57). The particle size and particle-size distribution have a dominant influence on several of the physical and hydro-logic properties of unconsolidated sediments. Although more refined statistical measures. could be utilized, a rough comparison of the effect of particle size and particle-size distribution can be achieved by grouping the samples by sediment class and deriving average values for the properties of particular interest. Accordingly, in table 10, the samples from the three core holes analyzed by the Hydrologic Laboratory have been grouped by sediment class (Shepard classification) and the range in, and average values for, the most pertinent properties have been listed. The sediment classes have been arranged, in general, from coarse to fine texture. For some of the sediment classes included, such as clayey sand, sandy silt, and silt, and for some of the properties listed for other classes, the number of tests is too small to compute a meaningful average. The data show that, in general, as the sediment class becomes finer, the permeability decreases and the liquid limit increases, but there does not seem to be any other consistent relation between other properties and the sediment class. Another factor important in interpreting or applying the results of these tests is the effect, if any, of depth on the averages. For example, porosity and dry unit weight are affected by thickness of overburden. Therefore, for the three most prevalent sediment classes, sand-silt-clay, clayey silt, and silty clay, porosity and dry unit weight have been plotted against depth by sediment class (fig. 22). The decrease in porosity (increase in dry unit weight) is most noticeable for core hole 14/13—11 Dl and least for core hole 19/17—22J1, 2. The relation of porosity to effective overburden load for sediments in all three areas is being appraised statistically by R. H. Meade (report on compaction of sediments, manuscript in review). TULARE-WASCO AREA The results of the tests for the most pertinent properties of samples analyzed for core holes 23/25-16Nl and 24/26-36A2 have been plotted on plate 13 in conjunction with the electric (self-potential and resistivity) logs for each core hole. Permeability, clay content, specific gravity, dry unit weight, porosity and void ratio, Atterberg limits, volumetric shrinkage, toughness index, acid solubility, and gypsum content are shown. Plate 13 thus serves as a graphic summary of most of the analyses made at the Hydrologic Laboratory on samples from the Tulare-Wasco area. The electric logs shown in plate 13 were made immediately after the core holes were drilled. The Corcoran Clay Member of the Tulare Formation and the upper Pliocene claystone are indicated by uniformly low resistivity. The sediments recovered were predominantly medium textured and primarily of silty-sand or sand-silt-clay types according to the Shepard classification system. According to the Unified Soil Classification plasticity chart, the sediments from both core holes are classified as organic or inorganic silt and silt-clay of low plasticity, inorganic clay of low to medium plasticity, and organic clay of medium to high plasticity. The samples had median diameters ranging from about 0.01 to 0.3 mm for core hole 23/25-16N1 and from about 0.003 to 1.4 for core hole 24/26-36A2,A42 MECHANICS OF AQUIFER SYSTEMS Core hole Core hole Core hole 14/13-11D1 16/15-34N1 19/17-22J1.2 o o oo o _L 8 csj oo o DRY UNIT WEIGHT, IN POUNDS PER CUBIC FOOT Core hole Core hole Core hole 14/13—11D1 16/15-34N1 19/17-22J1.2 'J; to 00 O to 00 o rr to 00 o O O O—* 000»-i O O O*—* VOID RATIO Fiodee 22.—Relation of dry unit weight, porosity, and void ratio to depth for principal sediment classes from core holes in Los Banos-Kettleman City area.PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A43 samples from the Corcoran Clay Member of the Tulare Formation being near the lower limit. The sorting coefficient ranged from 1.36 to 9.59 for core hole 23/25-16N1 and from 1.24 to 14.14 for core hole 24/26-36A2. The log quartile deviation ranged from about 0.095 to 1.150. Vertical permeability for the 138 samples tested from these core holes ranged from 0.0002 to 650 gpd per sq ft; horizontal permeability for the 79 samples tested ranged from 0.0003 to 61. About 30 percent of the samples had permeabilities between 0.01 and 0.1 gpd per sq ft. For the 76 samples tested for both, the ratio of horizontal to vertical permeability averaged 1.4. The Corcoran Clay Member had consistently low permeability. The specific gravity of solids ranged from 2.41 to 2.79, and averaged 2.70. The lowest values were for samples taken between depths of approximately 1,050 and 1,800 feet in core hole 24/26-36A.2. The dry unit weight ranged from 1.00 to 1.94 g per cc (62.4 to 121.1 lb per cu ft) and the porosity from approximately 28 to 61 percent. The void ratio ranged from 0.40 to 1.58. Samples of the Corcoran Clay Member and the upper Pliocene marine strata had the highest porosities and the lowest dry unit weights. The average porosity for core hole 24/26-36A2 increased gradually with depth down to 1,900 feet—from about 35 to 50 percent. The liquid limits ranged from 22 to 107; for cores taken from the thin section of the Corcoran Clay Member in core hole 23/25-16Nl the liquid limit ranged from 56 to 63 and for the thick section of upper Pliocene claystone in core hole 24/26-36A2 it ranged from 62 to 106. The plastic limit ranged from 18 to 62, and the shrinkage limit from 5 to 44. The plasticity indices ranged from 3 to 59, sediments in core hole 24/26-36A2 having a higher plastic range. Shrinkage indices ranged from 0 to 46, the higher indices being for the claystone of core hole 24/26-36A2. Volumetric shrinkage was highest for samples from the upper Pliocene marine strata, intermediate for the continental deposits in core hole 23/25-16Nl, and lowest for the continental deposits in core hole 24/26-36A2. Samples from the core holes had a toughness index ranging from 0.2 to 3.4, and usually 1 or greater. The Corcoran Clay Member and the upper Pliocene claystone had a toughness index generally greater than 2. The acid-soluble material ranged from about 1 to 21 percent and averaged 6 percent for core hole 23/25-16N1 and 5.2 percent for core hole 24/26-36A2. The gypsum content was 0 in selected samples from core hole 23/25-16Nl and only 1 percent or slightly greater in selected samples taken between 1,700 and 1,900 feet in core hole 24/26-36A2. The consolidation-test curves and the compression-index values show, in general, that the claystone of the upper Pliocene marine strata has a greater unit consolidation potential than any of the continental sediments. The unit consolidation potential for the Corcoran Clay Member is only about half as great as for the upper Pliocene marine strata, but it is much higher than that for the other continental deposits. In table 10, the samples from the two core holes in the Tulare-Wasco area analyzed by the Hydrologic Laboratory have been grouped by sediment class (Shepard classification) and the range in, and average values for, the most pertinent properties have been listed. The sediment classes have been arranged, in general, from coarse to fine texture. For some of the sediment classes included—such as sandy clay, silty clay, and silt—and for some of the properties listed for other classes, the number of tests is too small to compute a meaningful average. The data show that, in general, the permeability decreases as the sediment class becomes finer. The liquid limit increases as the sediment class becomes finer, but there does not seem to be any other consistent relation between other properties and the sediment class. For the three most prevalent sediment classes, sand-silt-clay, sandy silt, and silty sand, porosity and dry unit weight have been plotted against depth by sediment class (fig. 23). Normally, porosity is considered to decrease with depth and dry unit weight to increase. These plots show that the porosity increases with depth in core hole 24/26-36A2 in the depth range from 750 to 1,600 feet—-even more clearly defined in the porosity plot for all samples in plate 13. Thus, the relation of porosity (and dry unit weight) to depth is markedly anomalous in 24/26-36A2. In core hole 23/25-16Nl the porosity and dry unit weight do not change appreciably with depth, as shown in the porosity-depth plot for all samples in plate 13. SANTA CLARA VALLEY The results of the tests for the most pertinent properties of samples analyzed for the two Santa Clara Valley core holes—6S/2W-24C7 and 7S/1E-16C6— have been plotted on plate 14 in conjunction with the electric (self-potential and resistivity) logs for each core hole. Permeability, clay content, dry unit weight, specific gravity, porosity and void ratio, Atterberg limits, volumetric shrinkage, toughness index, acid solubility, and gypsum content also are shown. Plate 14 thus serves as a graphic summary of most of the analyses made at the Hydrologic Laboratory on samples from the Santa Clara Valley.DEPTH, IN FEET. BELOW LAND SURFACE A44 MECHANICS OF AQUIFER SYSTEMS . I . I . I ■ I » I , I i I i I i o o o o o o o oo o c\i oo o cnj <£> 00 O «J- <£> d d d~ -< *■* y/ *3- «3 00 O IO d OOHH- DRY UrT WEIGHT, IN POUNDS PER CUBIC FOOT VOID RATIO Figure 23.—Rei >,tion of dry unit weight, porosity, and void ratio to depth for principal sediment classes from core holes in Tulare-Wasco area.PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A45 The data for the two core holes are so arranged in plate 14 that the northern hole is located at the top of the figure and the southern hole is at the bottom. The total subsidence from 1934 to 1960 at each corehole site was about 5 feet (fig. 6). The graphic logs and generalized lithologic descriptions (pis. 1G, H) were prepared by J. H. Green from the geologist’s logs made at the wells, supplemented by interpretation of the electric logs, especially in zones of poor core recovery. The electric logs were made immediately after the core holes were drilled. Certain broad trends are evident from a study of plate 14 or the tables. The sediments recovered were predominantly fine textured and primarily of sand-silt-clay, clayey-silt, or silty-clay types, according to the Shepard classification system. According to the Unified Soil Classification plasticity chart (fig. 19), the sediments from both core boles are classified as predominately inorganic clay of low to medium plasticity, sandy clay, silty clay, lean clay, inorganic clay of high plasticity, and fat clay; one sample is organic clay of medium to high plasticity. The samples had median diameters ranging from about 0.001 to 0.2 mm for core hole 6S/2W-24C7 and from about 0.004 to 1.5 mm for core hole 7S/1E-16C6. The sorting coefficient ranged from 1.3 to 7.5 for samples from core hole 6S/2W-24C7 and from 1.3 to 7.7 for samples from core hole 7S/1E-16C6. The log quartile deviation ranged from about 0.127 to 0.876 for samples from core hole 6S/2W-24C7 and from 0.107 to 0.885 for samples from core hole 7S/1E-16C6. Vertical permeability for 47 samples from these core holes ranged from 0.0001 to 0.03 gpd per sq ft, horizontal permeability for 65 samples ranged from 0.0002 to 190. The range of permeability for the greatest percentage of samples was from 0.01 to 0.0001 gpd per sq ft. For the 47 samples tested for both, the average horizontal permeability was seven times greater than the average vertical permeability. The specific gravity of solids ranged from 2.67 to 2.80 and averaged 2.73. The dry unit weight ranged from 1.34 to 1.91 g per cc (83.7 to 119.2 lb per cu ft) and the porosity from approximately 30 to 50 percent. The void ratio ranged from 0.43 to 1.01. The liquid limits ranged from 24 to 68. The plastic limit ranged from 18 to 32, and the shrinkage limit from 8 to 20. The plasticity indices ranged from 3 to 38, sediments taken below 700 feet in core hole 6S/2W-24C7 having a higher plastic range. Shrinkage indices ranged from 1 to 18, the higher indices being for samples taken in the zones from 140 to 223 feet and 715 to 959 feet in core hole 6S/2W-24C7. Volumetric shrinkage ranged from 11 to 103 percent, the highest values being for samples taken below 700 feet in core hole 6S/2W-24C7. Samples from the core holes had a toughness index ranging from 0.9 to 5.7 and was usually 1 or greater. The acid solubility ranged from about 7 to 19 percent and averaged 10.4 percent for samples from core hole 6S/2W-24C7 and 14.2 percent for samples from core hole 7S/1E-16C6. The gypsum content was 0 in both core holes for all samples analyzed for this property. Consolidation-test curves show, in general, that the fine-textured sediments in the Santa Clara Valley have considerable consolidation potential. In table 9, the samples from the two Santa Clara Valley core holes analyzed by the Hydrologic Laboratory have been grouped by sediment class (Shepard classification), and the range in, and average values for, the most pertinent properties have been listed. The sediment classes have been arranged, in general, from coarse to fine texture. For some of the sediment classes included, such as sand, silty sand, and sandy silt, and for some of the properties listed for other classes, the number of tests is too small to compute a meaningful average. If only one sample falls within a certain sediment class, that class is omitted from table 10. The data show that, in general, the permeability decreases as the sediment class becomes finer. The liquid limit tends to increase as the sediment class becomes finer. There does not seem to be any other consistent relation between the other properties and sediment class. For the three most prevalent sediment classes, sand-silt-clay, clayey silt, and silty clay, porosity and dry unit weight have been plotted against depth by sediment class (fig. 24). No significant trend can be noticed in these plots. TABULATED STATISTICAL DATA Statistical data from the U.S. Geological Survey Hydrologic Laboratory and U.S. Bureau of Reclamation Earth Laboratory are tabulated in tables 5-10 following. Unless indicated otherwise analyses were made in the Hydrologic Laboratory.A46 MECHANICS OF AQUIFER SYSTEMS Core hole 6S/2W-24C7 Core hole 7S/1E-16C6 -1-l-L DRY UNIT WEIGHT, IN POUNDS PER CUBIC FOOT 1 .1 1 1 11.//_______I__I_LI *3" up 00 O to (£> OOO up o o ci —< —o ei ci— —J i VOID RATIO Figure 24.—Relation of dry unit weight, porosity, and void ratio to depth for principal sediment classes from core holes in Santa Clara valley.Hydrologic laboratory sample 57CAL1.. 2__ 3.. 4.. 5a. 5b. 6.. 7__ 8.. 9.. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46 47. 48. 49. 50. 51. 52. 53. 54. 55. 56 57. 58. 59. 60 61 62 63. 64 65 66. 67. Table 5.—Physical and hydrologic properties of samples from core holes Particle analysis, percentage of— Median Geometrical quartile Log quartile deviation Specific gravity Dry unit Sample depth diameter, deviation Sediment class Total Void (feet) Gravel Sand Silt Clay <0.001 mm Clay <0.002 mm D50 (mm) (sorting coefficient), So (log sorting coefficient), logio So (Shepard system) of solids G per cc Lb per cu ft porosity (percent) ratio Core hole 14/13-1 ID 1 ' Sp/y. P - 77.0- 77.5 24.8 49. 5 25.7 18 0.024 4. 04 0. 606 110. 5- 111.0 10.7 37.3 52.0 44 .0034 (J) (i) 153.0- 153.5 87.1 3.7 9.2 9 .19 1.46 . 164 Sand 2.67 1.37 85.5 48.7 .95 191.5- 192.0 29.0 46.8 24.2 20 . 028 3. 92 . 593 232.5- 233.0 21.6 30.4 48.0 39 .0045 (*) (i) 2. 68 232.5- 233.0 61.6 18.9 19.5 16 .092 3.16 . 500 2 64 277.1- 277.6 1.3 89.0 1.9 7.8 7 .25 1.59 .201 Sand 2.68 1.52 94.8 43.3 .76 314.0- 314.5 22.3 51.0 26.7 22 .019 4.12 .615 Sand-silt-clay 2.70 1.46 91.1 45.9 .85 353.0- 353.5 47.0 34.3 18.7 16 .060 3.37 . 528 2. 66 1 54 398.0- 398.5 .6 33.4 66.0 56 .0010 (>) to Silty clay 2. 62 1. 51 94.2 42.4 .74 432.0- 432.5 7.0 31.2 61.8 50 .0020 0) 0) 2 64 471.5- 472.0 47.3 40.0 12.7 11 .059 2.00 . 301 510.3- 510.8 .6 8.9 19.5 71.0 61 (>) (o CD Silty clay 2.64 1.39 86! 7 47.3 .90 552. '5- 553.0 22.0 33.0 45.0 36 .0062 (i) (!) 594.0- 594. 5 8.8 19.7 71.5 59 .0012 (0 (1) 631.0- 631.5 19.2 36.3 44.5 34 .0057 5.68 . 754 2 67 646.0- 647.1 1.0 47.5 51.5 40 .0036 (1) (l) 2. 72 652. 3- 652.8 23.3 40.1 36.6 26 . 0096 5.20 716 662.1- 662.6 .8 56.2 43.0 30 . 0058 3.26 . 513 674.0- 674.5 1.0 61.5 37.5 25 .0068 2. 61 . 417 2. 63 682.5- 683.0 26.8 45.2 28.0 20 . 013 5.06 . 704 697.0- 697.5 .6 68.4 31.0 20 . 0082 2.51 . 400 707.0- 707.5 80.2 16.1 3.7 3 .26 1.68 .225 2. 67 713.0- 713.5 .2 76.8 23.0 14 .010 2.00 .301 Silt 2. 68 721.5- 722.0 4.0 86.0 10.0 7 .012 1.48 . 170 2. 74 731.0- 731.5 1.6 59.4 39.0 26 . 0067 2.99 . 476 743.0- 743.5 6.0 70.0 24.0 17 .013 2.57 . 410 2 72 757.0- 757.5 50.2 38.1 11.7 8 .062 3.06 .486 2 73 764.9- 765.4 77.4 13.9 8.7 7 .34 2.42 .384 2. 71 773.0- 773.5 38.2 48.0 13.8 11 .050 2.22 .346 784.5- 785.0 16.2 61.8 22.0 14 .020 2.94 . 468 791.0- 791.5 26.0 44.2 29.8 26 .026 5.89 . 770 802.0- 802.5 35.4 43.0 21.6 16 . 040 3.56 . 551 2 75 812.0- 812.5 80.2 11.8 8.0 8 .25 2.36 .373 2. 67 813 - 821 .3 91.7 1.0 7.0 7 .21 1.27 .104 do 2.69 1.47 91.7 45.4 .83 826.0- 826.5 1.0 44.0 55.0 38 . 0033 2. 72 .435 2 74 831.5- 832.0 12.2 61.3 26.5 20 .020 3. 46 . 539 2 74 843.5- 844.0 69.0 20.0 11.0 9 .12 1. 91 .281 853.0- 853.5 83.2 10.6 6.2 5 . 12 1.31 . 117 2.74 1 49 860.0- 860.5 2.4 70.4 27.2 21 . 145 3. 01 .479 867.0- 867.5 54.2 27.8 18.0 16 . 010 0) 0) 871.0- 871.5 70.0 19.8 10.2 9 .099 1.73 .238 2 71 877.0- 877.5 4.5 49. 5 46.0 34 .0050 4. 24 . 627 2 77 887.5- 888.0 .8 49.7 49. 5 37 . 0041 3.16 . 500 901.0- 901.5 8.6 61.2 30.2 19 .011 2.97 .473 1. 57 98.0 43.1 .76 911.5- 912.0 48.4 34.6 17.0 16 .056 3.52 .547 2.71 917. 2- 917.7 80.0 13.0 7.0 7 .22 1.58 .199 2. 68 932.0- 932.5 8.0 47.3 44. 7 37 . 0064 (i) (i) 936.5- 937.0 12.6 65.4 22.0 14 .016 2. 60 . 415 951.0- 951.5 4.6 54.4 41.0 33 .0082 5.10 .708 do 2.74 1.87 116! 7 3l! 8 .47 957.5- 958.0 39.4 47.4 13.2 11 .044 2.34 .369 968.5- 969.0 6.0 68.8 25.2 20 .016 2.86 .456 984.0- 984.5 2.2 23.1 74.7 58 .0015 (i) (l) 987.6- 988.0 27.2 43.0 29.8 26 .026 6. 57 .818 1,000. 5-1,001. 0 4.2 54.8 41.0 32 .0068 4. 42 .645 Clayey silt 2.75 1.72 107.3 37.5 .60 1,005.1-1,005. 6 2.8 65.2 32.0 22 .0090 2. 79 .446 do.. 2. 73 1. 65 103.0 39.8 .66 1,010.8-1,021.3 11.4 65.8 22.8 16 .024 2. 83 .452 do 2. 79 1.69 105.5 39.4 .65 1,033. 8-1 034.2 52.0 32.0 16.0 13 .070 4.39 . 642 2 72 1.039. 5-1 040.0 1.8 52.2 46.0 36 .0048 (l) (0 1,051. 5-1,052. 0 12.4 67.6 20.0 15 .025 2. 51 .400 do 2.78 1.64 102.3 41.0 !70 1,063. 5-1,064. 0 35.6 40.4 24. 0 20 .026 6.14 . 788 1,070.8-1,071. 3 19.5 54.5 26.0 21 .020 3. 67 . 565 1,075. 0-1,075. 5 55.6 27.2 17.2 14 .079 3.02 .480 Silty sand 2. 75 1. 77 110.4 35! 6 ! 55 1,088. 5-1 089.0 81.6 9.4 9.0 8 .18 1.67 .223 2. 73 1. 62 101 1 1.092. 0-1.092. 5 35.4 49.6 15.0 12 . 042 3.16 . 500 1,104. 5-1 105.1 38.0 44.0 18.0 15 .037 1.15 .061 do 2.68 1.69 105.5 36! 9 ! 59 1,113. 5-1,114.0 ! 91.2 1. G 7.2 7 .23 1.23 . 090 2 70 1,123. 5-1 124.0 84.2 7.8 8.0 7 .16 1.38 . 140 do. 2. 74 1.57 98.0 42.7 .75 Coefficient of permeability (gp per sq ft at 60°F) Vertical Hori- zontal 0.01 360 .2 2 4 270 .6 2 .0007 .00007 .7 .0002 .0001 ’\'005" "‘."004" ”’668 " ”’.’662” 0.03 10 .002 .2 4 2 ”.’6666’ .0001 .0006 .007 33 .0005 22 .0007 .001 3 .001 .01 .1 .0001 .004 42 .04 .0006 174 50 See footnotes at end of table. PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A47Table 5.—Physical and hydrologic 'properties of samples from core holes—Continued Hydrologic laboratory sample 57CAL68.. 69. 70. 71. 72. 73 _ 74. 75.. 76. 77. 78. 79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92.. 93.. 94.. 95.. 96.. 97.. 98.. 99.. 100. 101. 102. 103. 58CAL1. 2.. 3.. 4.. 5.. 6.. 7.. 8.. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. Particle analysis, percentage of— Median Geometrical quartile Log quartile Sample depth (feet) Gravel Sand Silt Clay <0.004 mm Clay <0 002 mm diameter, Dw (mm) deviation (sorting coefficient), So deviation (log sorting coefficient), logio So Sediment class (Shepard system) Specific gravity Dry unit weight Total Void Coefficient of permeability (gpd per sq ft at 60°F) porosity (percent) ratio solids G per cc Lb per cu ft Vertical Hori- zontal Core hole 1413-11D1—Continued Z. K C /hr4* 1,133.0-1,133. 5 5.4 62.8 31.8 24 0.010 3.16 1,160 -1,166 2.1 83.4 6.5 8.0 7 .25 1.50 1,174. 0-1,174. 5 4.8 83.6 4.1 7.5 7 .52 1.68 1,207. 5-1,208.0 28.9 58.0 6.1 7.0 6 .52 3.26 1,219. O-l, 219. 5 4.4 76.1 9.7 9.8 9 .25 1.81 1,221.2-1,221.7 6.7 72.4 6.7 14.2 12 .35 2. 43 1,232. 0-1,232.5 11.6 75.3 8.9 4.2 3 .37 2. 03 1,242. (>-1,242.5 14.6 67.4 18.0 13 .021 2.37 1,252+-1,252. 5 73.8 17.2 9.0 7 .12 1.77 1,257. 0-1,257.5 .1 76.3 12.6 11.0 11 .16 1.85 1,269. 5-1,270. 0 53.6 22.2 24.2 24 .082 6.38 1,271.0-1,271.5 71.4 12.1 16.5 14 .185 2.83 1,284. 0-1,284.5 86.4 5.6 8.0 7 .017 1.41 1,293. 0-1,293.5 53.6 25.6 20.8 18 .082 4.68 1,300. 0-1,300.5 62.2 16.8 21.0 18 .12 4. 37 1,312.0-1,312.5 25.4 49.6 25.0 20 .022 4. 25 1,319.4-1,319.9 62.8 20.2 17.0 16 .18 4. 26 1,330. 8-1,331.3 65.0 15.8 19.2 17 . 12 3.82 1,339. 5-1,340.0 18.2 60.6 21.2 16 .022 2.97 1,348. 0-1,348.5 9.0 79.7 4.3 7.0 7 .47 1.88 1,357. 0-1,357.5 9.0 48.0 43.0 32 .0058 4.03 1,362. 5-1,363.0 29.0 48.0 23.0 19 .030 3. 67 1,373.4-1,373.9 51.0 28.0 21.0 17 .065 4.70 1,385.0-1,385.5 21.4 53.9 24.7 16 .016 3. 28 1,397. 0-1,397. 5 12.8 25.2 62.0 47 .0023 (i) 1,406. 0-1,406. 5 60.2 20.3 19.5 16 . 11 4.83 1,415. 0-1,415.5 58.4 26.1 15.5 14 .090 3.13 1,423. 7-1,424.2 62.4 22.6 15.0 13 .086 2. 55 1,432. 5-1,433.0 3.8 61.4 34.8 27 .0090 3. 61 1,446. 0-1,446.5 .4 54.4 45.2 35 .0048 0) 1,454. 5-1,455.0 27.4 48.1 24.5 19 .020 4.15 1,465. 0-1,465.5 3.8 33.0 63.2 47 .0023 (■) 1,474. 0-1,474.5 69.4 20.4 10.2 9 .12 1.85 1,481.0-1,481.5 1.7 51.5 31.6 15.2 10 .074 4. 56 1,487. 0-1,487. 5 82.8 8.7 8.5 7 .22 1.49 1,494. 5-1,495. 0 55.4 30.9 13.7 11 .089 3.52 2.77 1. 65 103.0 40.3 0. 68 .176 Sand 2. 77 1.61 100.5 41.9 .72 38 .225 do 2.71 1.60 99.8 41.0 .70 40 .513 do 2. 73 1. 56 97.3 42.9 .75 39 .258 do 2. 75 1.57 98.0 42.9 .75 1 .386 do 2. 70 1.50 93.6 44.4 .80 2 .308 do 2.69 1.50 93.6 44.2 .79 45 2. 69 1. 56 97.3 42.0 .72 .248 Silty sand 2. 72 1.60 99.8 41.2 .70 2 .267 Sand 2. 71 1.40 87.4 48.3 .93 10 .805 Sand-silt-clay. 2. 70 1.84 114.8 31.9 .47 .0002 .452 Clayey sand 2.69 1.70 106.1 36.8 .58 .9 .149 Sand 2.72 1.63 101.7 40.1 .67 27 .670 Sand-silt-clay 2.71 1. 78 111.1 34.3 .52 .0004 .640 Clayey sand 2.72 1.93 120.4 29.0 .41 .0001 .628 Sand-silt-clay 2. 74 1.79 111.7 34.7 .53 .008 .629 Silty sand 2.72 1.94 121.1 28.7 .40 .004 .582 Clayey sand 2.71 1.95 121.7 28.0 .39 .004 .473 Clayey silt 2. 71 1.70 106.1 37.3 .60 .01 .274 Sand - 2.74 1.39 86.7 49.3 .97 13 .605 Clayey silt 2. 73 1.78 111.1 35.0 .54 2 73 . 672 2.70 1.46 91.1 45.9 .85 516 2. 69 1. 56 97.3 42.0 .72 (l) 2.69 1.72 107.3 36.1 .56 .684 Silty sand 2. 72 1.81 112.9 33.5 .50 .006 .496 do 2. 70 1.48 92.4 45.2 .83 .07 . 407 2. 74 1. 63 101.7 40.5 .68 2. 69 1. 53 95. 5 43.3 .76 (l) 2.72 1.69 105.5 38.1 .62 2.70 1. 63 101.7 39. 6 . 66 (l) 2.76 1. 63 101.7 40.9 .69 .267 Silty sand 2. 73 1.54 96.1 43.6 .77 4 .659 do 2. 73 1.63 101.7 40.3 .67 1 .173 Sand 2. 74 1. 51 94.2 44.9 .82 8 .547 Silty sand 2.72 1.42 88.6 47.8 .92 18 250.0- 298.2- 332.4-371. 7- 418.5- 454.3- 496.4- 507.4- 509.5-525.9- 532.4-552.8- 563.7- 570.7- 580.5- 591.7- 601.7-622.3-636. 4- 643.2- 652.6- 666.0- 673.6-683. 7- 696.0- 701.8-713. 4- 721.3- Core hole 16/15-34N1 250.5 2.3 64.5 20.7 12.5 11 0.12 2.47 0.393 298.7 .3 22.8 49.6 27.3 22 .017 4.36 .639 332.9 26.6 37.7 35.7 28 .010 7.26 .861 372.1 72.4 13.7 13.9 12 .14 2. 44 .387 419.1 15.2 48.9 35.9 22 .0085 4. 01 .603 454.8 18.6 33.4 48.0 42 .0050 w (>) 496.9 71.8 14.9 13.3 12 .15 2.16 .334 507.9 1.1 9.5 51.1 38.3 29 .0075 3.96 .598 510.0 4.6 67.7 27.7 20 .0096 2.58 .412 526.3 2.0 58.0 40.0 27 .0057 2.58 .412 532.9 38.2 31.8 30.0 24 .028 7. 66 .884 553.2 19.4 48.7 31.9 23 .016 4. 42 .645 564.2 16.2 47.8 36 0 25 .0092 4. 36 .639 571.2 8. a 47.0 45.0 35 .0054 4.85 .686 581.0 91.0 6.3 2.7 2 .20 1.35 .130 592.2 96.8 2.8 .4 .26 1.24 .093 602.2 93.8 5.2 1.0 1 .30 1.46 .164 622.8 84.6 10.5 4.9 4 .18 1.61 .207 636.9 25.8 50.2 24.0 16 .021 3.86 .587 643.7 29.6 48.5 21.9 18 .028 3.35 .525 653.1 40.0 33.8 26.2 21 .037 6. 42 .808 666.5 4.0 48.5 47.5 36 .0044 3.13 .496 674.1 3.8 24.4 71.8 57 .0015 o) (■) 684.2 20.4 56.6 23.0 19 .030 3.11 .493 697.1 2.4 34.0 63.6 50 .0020 (•) 702.4 11.6 60.4 28.0 22 .015 3. 37 .528 713.9 4.4 51.1 44.5 26 .0050 2. 65 .423 721.8 46.8 35.2 18.0 17 .056 3.30 .519 Silty sand__________ Sand-silt-clay------ ____do.............. Clayey sand......... Clayey silt........... Silty clay__________ Silty sand__________ Clayey silt_________ ____do.............. ____do............... Sand-silt-clay...... Clayey silt--------- ____do.............. ____do______________ Sand................ ____do______________ ____do______________ ____do.............. Sand-silt-clay...... ____do................ ____do______________ Clayey silt_________ Silty clay.......... Sand-silt-clay______ Silty clay__________ Clayey silt_________ ____do______________ Silty sand__________ 2.69 2.68 2.68 2.66 2. 66 2. 66 2. 70 2.68 2.71 2. 65 2. 68 1.59 1.40 1.52 1. 51 1.42 1.50 1.48 1.53 1.40 1.38 99.2 87.4 94.8 94.2 88.6 93.6 92.4 95.5 87.4 86.1 40.9 47.8 43.3 43.2 46.6 43.6 45.2 42.9 48.4 47.9 .69 .92 .76 .76 .87 .77 .83 .75 .94 .92 0.8 .04 .1 1 .003 .0003 3 .002 .006 .002 .0003 .004 .004 .03 2. 65 .004 .004 2.63 1.42 88.6 46.2 .86 .002 .003 2.68 1.23 76.8 54.1 1.18 .002 .0004 2.70 1.49 93.0 45.0 .82 13 52 2. 70 1.47 91.7 45.8 .85 260 270 2.69 1.58 98.6 41.5 .71 53 55 2. 70 1. 47 91.7 45.6 .84 12 45 2 68 1 34 83. 6 50. 6 1.03 2.69 1.48 92.4 45.0 .82 .01 .05 2.68 1.72 107.3 36.0 .56 .01 2.68 1.51 94.2 43.9 .78 .0005 .002 2.64 1.48 92.4 44.2 1.79 .002 .0002 2.67 1.41 88.0 47.4 .90 .06 .1 2. 66 1.45 90.5 45.5 .83 .001 .004 2.69 1.40 87.4 48.0 .92 .02 .02 2. 65 1. 56 97.3 41.2 .70 .0002 .0007 2.67 1. 55 96.7 42.2 .73 .6 A48 MECHANICS OF AQUIFER SYSTEMS29 732.6- 732.6 22.4 53.6 24.0 23 .021 3.22 . 508 2. 67 1 59 .03 30 745.3- 745.9 10.0 28.2 61.8 54 0) (») 2. 63 1. 56 97 3 40 7 31 753.8- 754.3 8.4 61.1 30 5 23 . 12 3.23 . 509 99.2 40.9 .004 32 762.4- 762.9 18.6 34.9 46.5 36 .0050 5.83 .766 2.64 33 773.3- 773.8 35.4 40.4 24.2 19 . 033 4. 62 . 665 2 66 34 785.0- 785.5 .5 82.6 9.5 7.4 7 . 18 1.53 . 185 2. 69 1. 52 94.8 43 5 35 795.0- 795.5 9.6 30.6 59.8 50 . 0021 0) (i) 36 806.1- 806.6 7.2 35.8 57.0 44 .0029 w 0) do 2.64 1.52 94.8 42.6 .74 .0001 .02 37 810.5- 811.0 33.4 48.6 18.0 16 .042 2. 73 .436 2. 68 1 57 38 822.1- 822.6 20.4 27.4 52.2 44 .0032 0) (i) 2 73 1.38 86.1 49.7 39 827.8- 828.2 26.2 31.8 42.0 34 .0082 0) (i) 2. 65 40 837.7- 838.2 4.6 43.2 52.2 39 .0036 3. 54 549 2 72 41 852.2- 852.7 49.8 28.0 22.2 18 .062 4.85 686 .01 42 860.1- 860.6 26.0 46.5 27.5 22 .016 4.62 .665 2.70 1.49 93.0 44.8 43 866.7- 867.3 53.4 21.6 25.0 24 .070 5. 45 .736 do 2. 66 1. 66 103.6 37.8 .61 !oi .05 44_ _ 876.6- 877.1 79.0 12.0 9.0 8 . 190 1.75 .243 2. 68 1 56 48 45 891.6- 892.1 18.6 34.4 47.0 38 .0054 0) 0) 2. 62 1.44 89. 9 45 1 46 901.2- 901.7 6.4 38.6 55.0 42 .0031 0) (l) 2.63 1.56 97.3 40.7 . 69 47 910.6- 911.1 .4 73.5 15.1 11.0 11 .14 1.87 .272 2. 68 1. 55 96.7 42 4 19 48 922.6- 923.1 12.4 38.2 49.4 38 .0042 0) (l) 2. 65 1.54 96.1 41.9 49 931.2- 931.7 24.2 44.3 31. 5 25 .010 ' 5.48 . 739 2 67 50 940.6- 941.1 12.0 44.0 44.0 36 .0064 w 0) Silty clay _. 2. 65 1. 57 98.0 40.8 .69 . 0004 . 004 51 946.3- 946.8 .8 33.3 65.9 49 .0021 (*) w do 2.63 1.57 98.0 40.5 .68 .002 . 005 52 963.7- 964.2 28.2 49.7 22.1 17 . 028 3. 50 . 544 2. 68 1 54 .005 53 971.5- 972.0 2.5 64.2 33.3 24 .0086 2.94 .468 2. 65 1. 50 93. 6 43. 4 77 54 980.6- 981.1 21.0 70.2 8.8 6 .038 1.73 .238 2. 75 1. 59 99.2 55 998.4- 998.9 .1 95.5 3.9 .5 .48 1.49 .173 2.70 1. 52 94.8 43. 7 56 1,012.2-1,012.7 . 1 87.9 9.0 3.0 3 .21 1.62 .210 2. 70 1. 54 96.1 43.0 57.. 1,037.2-1, 037. 7 5.0 44.1 50.9 36 .0038 w (■) Silty clay 2. 76 1.54 96.1 44.2 .79 .003 .005 58 1,042. 8-1,043.3 8.0 38.0 54.0 42 .0032 0) 0) 2. 67 1.53 95. 5 42. 7 59 1,154. 0-1,154.5 24.2 53.8 22.0 14 .020 3.49 .543 2. 72 1.70 106.1 60 1,181.2-1,181.7 20.2 20.8 59.0 52 .0016 (l) 0) 2. 74 61 1,189. 5-1,190. 0 11.4 57.3 31.3 26 .018 4. 85 .686 2. 71 1.63 101 7 .001 62 1,202. 5-1,263. 0 22.0 23.3 54.7 45 .0028 0) 0) 2.71 1.49 93.0 45.0 . 82 .002 63 1,225. 0-1,225.5 12.6 74.4 13.0 10 .023 2.11 .324 2.73 1. 55 96. 7 43. 4 .004 64 1,238.1-1,238. 6 3.8 58.4 37.8 25 .0068 2. 78 .444 2.75 1.66 103. 6 39. 6 . 66 65 1,240. 5-1,241.0 30.2 58. 8 11.0 8 .044 1.97 .294 2. 74 1. 59 99.2 66 1.254. 9-1.255.4 4.4 81.4 14.2 11 .015 1.79 .253 Silt 2. 73 1.38 86.1 49. 5 . 98 67 1,280.2-1.280 7 3.0 69.7 27.3 18 .014 2. 95 .470 2. 75 1. 55 96. 7 43. 6 68 1,325. 5-1,326.0 8.6 43.4 48.0 34 .0044 3.33 .522 2. 70 1.48 92. 4 45 2 69 1,331.9-1,332.4 . 1 78.1 15.7 6.1 6 . 10 1.36 . 134 2. 71 1 58 26 70 1,351.4-1,351.9 25.4 56.9 17.7 16 .030 2. 43 .386 Sandy silt 2.73 1.44 89.9 47.3 .90 .001 71 1,363. 6-1,364.1 75.4 21.9 2.7 2 . 10 1.60 .204 2. 70 1. 50 93. 6 44 6 72 1,371. 5-1.372.0 43.8 51.9 4.3 3 .056 1.73 .238 Sandy silt... 2.70 1.65 103.0 39.9 .66 . 5 .3 73 1,391.7-1.392.2 39.4 46.1 14.5 8 .038 3. 54 .549 2. 70 1.51 94.2 40 6 74 1.401.8-1,402.3 71.0 19.6 9.4 8 .14 2.17 .336 2. 68 1.71 106. 7 36.2 . 57 3 75 1,413. 8-1,414.3 .6 48.3 25.7 25.4 24 . 062 7.37 . 867 .002 76 1,421.5-1,422.0 51.2 32.2 16.6 13 .066 3.16 .500 2. 72 1. 73 108 0 36 3 77 1,432.6-1,432.5 15.4 37.8 46.8 36 .0049 5.05 .703 2.70 1 63 101 7 .001 .002 78 1, 458.9-1, 459.4 34.5 65.5 42 .0026 2.04 .310 2.70 1.69 105.5 37.4 .60 79 1, 476.6-1, 476. 5 7.6 54.4 38.0 29 .0088 4.40 .643 2.69 1.65 103.0 38.7 63 80 1, 482.7-1, 483.2 3.6 67.9 28.5 21 .012 3.11 .493 2.74 1.44 89.9 47 5 81 1, 495.9-1, 496. 4 45.4 35.1 19.5 17 .052 3. 67 .565 2. 69 1 81 82 1, 506.7-1, 507.2 48.2 35.7 16.1 13 .059 2.96 .471 2.72 1.66 103.6 .08 83 1, 507.2-1, 507.7 30.8 32.7 36.5 30 .014 9. 74 .989 2.71 1.71 106.7 37 1 84. 1, 526.0-1, 526. 5 12.8 55.5 31.7 24 .010 3. 54 .549 2.69 85 1, 550. 6-1, 551.0 90.4 6.0 3.6 3 .24 1.48 . 170 2.71 1 52 94 8 160 86 1, 558.1-1, 558.6 4.2 39.3 56.5 38 .0031 2.72 .435 2.70 1.59 99.2 41.1 .70 .002 87 1, 566.6-1, 566. 5 51.8 29.2 19.0 18 .066 3. 46 .539 2.67 1.71 106.7 35.8 . 56 88 1, 589.3-1, 589.8 .2 69.5 30.3 23 .0050 1.75 .243 2. 66 1.66 103.6 37. 6 60 89-. 1, 631.2-1,631.7 5.4 41.6 53.0 32 .0037 2.85 .455 2.69 1.52 94.8 43. 5 77 90 1, 676.6-1, 677.1 21.0 42.0 37.0 30 .016 6.88 .838 2.70 1 66 .007 91 1, 714.1-1, 714. 5 29.6 37.7 32.7 27 .020 7.46 .873 2.43 1.10 68.6 54 7 92 1, 752.0-1, 752. 5 31.8 18.3 49.9 43 .0042 (i) (i) 2.69 1.79 111.7 33 5 93 1,792.7-1, 793.2 50.0 30.7 19.3 15 .062 ^ 3.63 .560 Silty sand 2.70 1.71 106.7 36.9 .59 .001 .007 94 1,837. 6-1,838.1 46.8 39.8 13.4 10 .059 2.21 .344 2.72 1. 60 99.8 41.2 70 95 1, 871.3-1,871.8 .6 71.8 27.6 18 .0096 2.30 .362 2.71 .004 96 1,916.9-1,917.4 1.4 60.3 38.3 28 .0070 2.87 .458 2.71 1.38 86.1 49.1 !97 97 1,953.0-1,953. 5 27.2 27.8 45.0 38 .0069 (i) (!) 2.50 1 46 91 1 98 1,990.0-1,990. 5 52.6 16.0 31.4 27 .088 17.2 1.236 Clayey sand 2.68 1.67 104.2 37.7 .61 .001 Core hole 19/17-22J1, 2__________ 57CAL104 105. 106. 107. 108. 109. 110. 111. 112. 89.6-160 - 233.8-270 - 310.0- 350.3- 399.4- 430.9- 476.0- 90.0 172 234.4 279 310.5 350.8 399.9 431.4 476.4 5.7 35.6 58.7 45 32.0 38.8 29.2 24 41.8 41.2 17.0 14 8.4 27.6 64.0 50 44.2 31.3 24.5 21 7.6 40.4 52.0 40 0.2 84.6 8.0 7.2 6 14.0 40.7 45.3 40 1.0 42,0 57.0 38 0.0026 .020 .047 .0020 .050 .0036 .24 .0059 .0032 (0 a 61 3.00 0) 5.68 (0 1. 0) 1.39 2.57 (■> Silty clay 2.67 1.64 102.3 38.6 0.63 0.820 Sand-silt-clay 2.74 1.84 114.8 32.8 .49 .477 Silty sand 2.69 1.71 106.7 36.4 .57 Silty clay. 2. 67 1.50 93.6 44.4 .80 .754 Sand-silt-clay _ 2.71 1.76 109.8 35.1 .54 « Silty clay 2.66 1.50 93.6 43.8 .78 .143 Sand. . . 2.68 1.63 101.7 39.2 .64 (>) Silty clay 2.63 1.48 92.4 43.7 .78 .410 do 2.67 1.43 89.2 46.4 .87 .0003 See footnotes at end of table. PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A49Table 5.—Physical and hydrologic properties of samples from core holes—-Continued Hydrologic laboratory sample Sample depth (feet) Par Gravel tide ana Sand lysis, per Silt centage Clay <0.004 mm Clay <0.002 mm Median diameter. Dm (mm) Geometrical quartile deviation (sorting coefficient), So Log quartile deviation (log sorting coefficient), logio So Sediment class (Shepard system) Specific gravity of solids Dry unit weight Total porosity (percent) Void ratio Coefficient of permeability (gpd per sq ft at 60*F) G per cc Lb per cu ft Vertical Hori- zontal Core hole 19/17-22Jl,2—Continued .510 ft- 51ft.fi 71.2 16.8 12,0 12 0.13 1.88 ft. 274 Silty sand 2.72 1.53 95.5 43.8 0.78 13 010 3.59 .555 2. 69 1.59 99.2 40.9 .69 593 3- 593.8 47.0 43! 0 10.0 8 .058 1.86 .270 Silty sand 2.70 1.52 94.8 43.7 .78 16 55 4 34 6 10.0 8 .072 2. 54 .405 do 2. 70 1.56 97.3 42.2 .73 .5 117 676! 0- 676.4 91.6 2.4 6.0 5 .020 1.41 .149 Sand.._ 2. 67 1.46 91.1 45.3 .83 120 712.8- 713.2 86.2 7.3 6.5 6 .15 1.24 .093 do.. 2. 67 1.45 90.5 46.3 .86 60 100 75.4 15.6 9.0 8 .10 1. 48 .170 . -_.do 2.72 1.46 91.1 46.3 .86 7 11.4 58. 6 30.0 22 .013 3.19 .504 Clayey silt 2.69 1.42 88.6 47.2 .89 .002 26.8 44. 2 29.0 25 .023 5.61 .749 Sand-silt-clay 2.68 1.57 98.0 41.4 .71 90.4 2.6 7.0 6 .32 1.35 .130 Sand 2. 66 1.52 94.8 42.9 .75 11 330 12.0 61.2 26.8 20 .016 3.21 .507 Clayey silt 2. 66 1.52 94.8 42.9 .75 .0004 13 5 9 .030 1.78 .250 2. 66 3. 6 60.9 35.5 20 .0064 2.40 .380 do 2.68 1. 56 97.3 41.8 .72 52 9 27.5 20 .018 4. 02 .601 2. 67 1.51 94.2 43.4 .77 .005 45 4 33.0 26 .012 5. 27 .722 2. 66 1.64 102.3 38.3 .62 14.8 68. 2 17.0 12 .021 2.29 .360 Clayey silt 2.67 1. 58 98.6 40.8 .69 .001 869 7- 870 2 40.8 46.2 13.0 10 .045 2.50 .398 Sandy silt 2. 70 1. 65 103.0 38.9 .64 .05 870.0- 870. 5 27.2 48.8 24.0 18 .022 4.14 .617 Sand-silt-clay 2. 66 1.50 93.6 43.6 .77 .001 888.6- 889.1 905.3- 905.7 3 6 31 9 64. 5 50 .0020 (l) (l) 2. 64 1.33 83.0 49.6 .98 30.2 28.8 41.0 30 .0086 7.74 .889 Sand-silt-clay 2. 67 1.67 104.2 37.5 .60 .05 24.8 54 2 21.0 15 .024 3. 33 .522 2. 64 1.58 98.6 40.2 .67 .1 4.0 56.5 39.5 20 .0056 2.10 .322 Clayey silt 2. 61 1.50 93.6 42.5 .74 8 8 37 7 53. 5 38 .0034 3. 57 .553 2. 65 1.45 90.5 45.3 .83 60 4 23 5 15.5 12 .12 3.87 .588 2.69 1.43 89.2 46.8 .88 .01 11.0 39.0 50.0 33 .0039 2.93 .467 Silty clay 2. 66 1.50 93.6 43.5 .77 .002 8 2 58 8 33.0 23 .0082 2.96 .471 2. 65 1.49 93.0 43.8 .78 47.4 43. 6 9.0 6 .060 2.24 .350 2.68 1.50 93.6 44.0 .79 .02 51.6 31.1 17.3 14 .072 5.39 .732 2.70 1.68 104.8 37.8 .61 .0003 6.4 46 9 46.7 32 .0045 3.28 .516 2. 66 1.56 97.3 41.4 .71 .0007 47.8 32.2 20.0 14 .058 1.31 .117 Sand-silt-clay 2. 65 1.62 101.1 38.9 .64 .07 86 4 5.0 4 . 18 1.48 .170 2. 70 1.35 84.2 50.0 1.00 230 12 4 35.0 24 .0082 3.63 .560 2. 65 1.57 98.0 40.8 .69 12.0 44 0 44.0 30 .0052 3.42 .534 2. 66 1.44 89.9 45.9 .85 .002 6.4 44.4 30 .0048 2. 94 .468 2.67 1.47 91.7 44.9 .82 19. 4 45A 35.5 29 .0099 5.62 .750 2. 66 1.58 98.6 40.6 .68 9 0 53.8 35 .0035 2. 62 .418 2. 66 1.48 92.4 44.4 .80 22.5 62 9 14. 6 14 .028 2.35 .371 2. 66 1.55 96.7 41.7 .72 15.6 14. 0 10 .026 2.19 .340 2. 67 1.67 104.2 37.5 .60 .1 10.8 18.2 71.0 57 .0016 0) « Silty clay 2.60 1.49 93.0 42.7 .75 .0001 1,198. 5-l! 199.2 40.0 37.8 22.2 16 .037 5.09 .707 Sand-silt-clay 2.68 1.72 107.3 35.8 .56 .0006 13. 2 16. 0 9 .016 2.27 .356 2.66 1.41 88.0 47.0 .89 40. 2 17. 0 11 .035 4.03 .605 2.68 1.65 103.0 37.3 .50 46.2 37.6 16.2 13 .054 2.67 .427 Silty sand 2.69 1.63 101.7 39.6 .66 2 .3 2.5 9 0 .29 2.24 .350 2.69 7 7.4 47.5 36 .0043 (!) (i) 2.65 1.59 99.2 40.6 .67 31 .0054 5.34 .728 2.67 1.57 98.0 41.2 .70 5. 4 44. 0 30 .0050 3.16 .500 2.65 1.46 91.1 44.9 .82 32.2 36.0 28 .014 8.29 .919 2.66 1.55 96.7 41.7 .72 15.0 50 5 34.5 26 .0090 4.12 .615 2.66 1.61 100.5 39.5 .65 38.6 35.4 26.0 16 .028 5.70 .756 2.68 1.67 104.2 37.7 .61 .0008 8.8 49.5 36 .0041 3.81 .581 2.67 1.62 101.1 39.3 .65 9.2 29.0 22 .010 3.05 .484 2.68 1.65 103.0 38.4 .62 10.0 41.0 49.0 34 .0042 3. 54 .549 2.68 1.64 102.3 38.8 .63 21.6 50.9 27.5 19 .014 3.85 .585 2.66 1.59 99.2 40.2 .67 l| 427.9-1! 428. 4 17.6 45.9 36.5 27 .0092 4. 73 .675 Clayey silt 2.69 1.70 106.1 36.8 .58 .0002 31.2 22.0 17 .024 4.18 .621 2.69 1.61 100.5 40.1 .67 21.6 30. ft 21 .010 3.88 .589 2.67 1.53 95.5 42.7 .75 17.6 32.0 22 .0094 3.80 .580 2. 70 1.71 106.7 36.7 .58 5 6 13 012 2.14 .330 2.66 .01 27.2 31.0 22 .014 5.3/ .730 2.67 1.68 104.8 37.1 .59 15.0 58.8 26.2 19 .014 3.42 .534 2.69 1.61 100.5 40.1 .67 .0006 39.2 40.5 20.3 16 .039 4.08 .611 2.67 1.76 109.8 34.1 .52 .1 14.0 41.0 30 .0064 4.31 .634 2.63 1.63 101.7 38.0 .61 17.0 14 .048 2.67 .427 2. 70 1.66 103.6 38.5 .63 67.2 22 3 10.5 9 . 11 1.88 .274 2. 70 1.78 111.1 34.1 .52 2 1,475.9-1! 575.4 32.8 46.2 21.0 19 .026 3.74 .573 San'd-silt-clay_ 2.70 1.72 107.3 36.3 .57 .0009 .09 22 ft 22.0 16 .020 3.32 .521 2.67 1.73 108.0 35.2 .52 14 . 030 2.93 .467 2.67 1.59 99.2 40.4 .68 29.2 28.0 20 .016 4.87 .688 2.67 1.60 99.8 40.1 .67 .005 182 l! 642! 0-1! 642.5 34.8 41.9 23.3 18 .030 4.57 .660 do 2.66 1.77 110.4 33.5 .50 A50 MECHANICS OF AQUIFER SYSTEMS183 1,650.2-1,650. 7 1.668.5- 1,668.9 1.677.8- 1,678.3 1.698.5- 1,699.0 1.718.8- 1,719.2 1.727.5- 1,728.0 1,748.0+ 1.779.3- 1,779.8 1,800.1-1,800.6 1.804.5- 1,805.0 1.831.1- 1,831.6 1.841.4- 1,842.0 1,867. 5-1.868.0 1.873.1- 1,873.6 1,899. 3-1,899.8 1,912. 5+ 1,937.0+ 1, 956. 3-1,956. 7 1,976.0+ 1,993.0-1,993. 5 2,019. 5-2,020.0 2,019.3 -2,049. 7 2,064. 0-2,064. 5 2, 091.2-2. 092. 6 189 196. 58CAL99... 100.. 101.. 102.. 103.. 104- 105- -*•106-107 _ 108. 109. 110. Jft: 113. Lil6. vay. 31.3 70. 3- 118.3- 155.1-193. 5- 235.3- 268.3- 287.2- 294.6- 304.7- 316.4- 320.3- 335.8- 343.0- 352.8- 362.5- 370.3- 418.0- 427.1- 442.4- 419. 120. 121. 122. 123. 124. 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135. 136. 137. 138. 139. 140. 141. 142. 143. 144. 145. 450.5- 465.0-475.3- 482.0- 496.0- 508.8- 511.0- 523.0- 534.0- 545.5- 560.6- 581.5- 594.0- 600.5- 616.0-621. 7-630. 7- 644.0- 654.1-660.0- 673.1-682. 7- 694.0- 705.1- 723.8- 730.5-748.0- 31.9 70.4 118.8 155.6 194.0 235.8 268.8 287.7 295.2 305.1 316.9 320.8 336.4 343.5 353.3 363.0 370.8 418.5 427.7 442.9 451.0 465.5 475.8 482.5 496.5 509.3 511.5 523.5 534.5 546.0 561.1 582.1 595.0 601.0 616.4 622.2 631.2 644.5 654.6 660.5 673.6 683.2 694.5 705.6 724.3 731.0 748.5 18.0 30.0 52.0 39 .0036 (*) o) Silty clay 15.6 55.4 29.0 20 .013 3.37 .528 Clayey silt 8.0 51.5 40.5 30 .0068 4.14 .617 do 44.0 35.0 21.0 17 .046 4.33 .636 Sand-silt-clay 9.0 51.0 40.0 29 .0064 3.83 .583 Clayey silt 16.6 52.4 31.0 23 .013 3.95 .597 do. 9.2 47.8 43.0 27 .0052 2.84 .453 do 7.0 59.0 34.0 25 .0096 3. 74 .573 do 30.2 30.8 39.0 36 .013 (>) 0) Sand-silt-clay 38.0 49.2 12.8 4 .037 3.42 .534 Sandy silt 4.6 68.2 27.2 13 .0076 1.94 .288 Clayey silt 15.8 46.2 38.0 28 .0090 4.68 .670 . ..do 46.8 42.2 11.0 4 .050 4.36 .639 Silty sand 35.2 48.1 16.7 14 .050 2.41 3.82 Sandy silt 5.2 49.8 45.0 32 .0050 3.57 .553 Clayey silt 15.8 43.2 41.0 31 .0072 4. 96 .695 do 31.2 29.8 39.0 30 .0090 10.0 1.000 Sand-silt-clay 47.0 23.0 30.0 27 .049 11.2 1.049 do 35.4 20.1 44.5 37 .0072 (>) 0) Sandy clay 12.2 18.8 69.0 51 .0019 « « Silty clay 16.2 46.6 37.2 25 .0066 3. 31 .520 Clayey silt... .. 15.6 63.7 20.7 8 .013 2.81 .449 do 10.2 28.8 61.0 50 .0020 (>) 0) Silty clay 14.2 25.3 60.5 37 .0029 2. 30 .362 do Core hole 23/25-16N1 7“ /f 46.6 32.0 21.4 20 0. 049 6.27 0. 797 Sand-silt-clay 22.2 58.7 20.0 14 .025 3. 01 .478 -do 45.8 35.2 19.0 11 .049 5. 86 .768 Silty sand 51.6 35.3 13.1 12 .065 2.19 .341 do 53.6 30.2 16.2 14 .075 4.60 .662 44.7 32.0 23.3 18 .053 4. 66 .668 Sand-silt-clay 39.4 34.1 26.5 16 .0295 7. 07 .849 2.2 71.9 25.9 20 .014 2.57 .410 Clayey silt .2 64.1 35.7 27 .0088 3.35 .525 do 92.4 6.6 1.0 1 .227 1.36 .132 Sand. 22.8 57.1 20.1 17 .030 2.71 .434 Sand-silt-clay 42.6 34.2 23.2 19 .041 5.45 .737 do 32.2 35.0 32.8 26 .0163 9. 59 .982 do 9.2 54.6 36.2 26 .0071 3.42 .534 Clayey silt -. 24.0 48.0 28.0 24 .0227 4.89 .690 Sand-silt-clay 46.8 35.4 17.8 114 .055 3.92 .593 Silty sand 18.2 59.9 21.9 8 .0216 2.85 .455 Clayey silt 18.2 47.8 34.0 26 .0125 4.95 .695 do 11.8 54.5 33.7 29 .0107 0) « do 9.8 44.4 45.8 34 .0050 0) (■> Silty clay 2.8 67.4 29.8 22 .0098 2.70 .431 Clayey silt 11.6 66.4 22.0 17 .0214 2.50 .398 do 35.0 46.3 18.7 13 .0355 4.39 .643 Sandy silt 8.6 37.8 53.6 38 .0035 (*) « Silty clay 31.4 31.6 27.0 22 .0275 5.27 .722 Sand-silt-clay 33.2 47.6 19.2 16 .0335 3.39 .531 Sandy silt 17.4 43.9 38.7 31 .0094 5.82 .764 Clayey silt 37.4 33.2 29.4 24 .030 7.22 .858 Sand-silt-clay 45.8 44.5 9.7 6 .057 1.98 .296 Silty sand 6.4 50.6 43.0 30 .0055 3. 21 .507 Clayey silt... 17.0 65.3 17.7 12 .0272 2. 46 .392 . . do 87.4 8.1 4.5 4 .300 1.98 .297 Sand 21.2 43.3 35.5 25 .0096 4.81 .682 Sand-silt-clay 22.4 58.6 19.0 14 .0228 2.88 .459 Sandy silt. 25.0 41.0 34.0 26 .012 5.97 .776 Sand-silt-clay 44.8 45.0 10.2 8 .054 2.25 .352 Sandy silt 58.8 29.2 12.0 10 .079 2.16 .334 Silty sand 53.0 33.4 13.6 11 .068 2. 72 .434 do 28.6 49.4 22.0 IS .0253 3. 77 .576 Sand-silt-clay 55.2 33.8 11.0 10 .072 2.08 .318 Silty sand 34.0 44.2 21.8 18 .029 4.10 .612 Sand-silt-clay 14.6 72.3 13.1 8 .027 2.09 .321 Sandy silt 55.8 28.5 15.7 14 .081 3.25 .512 Silty sand 39.2 51.7 9.1 6 .0445 2.12 .327 Sandy silt 17.6 59.8 22.6 16 .0163 2.87 .458 Clayey silt 6.8 68.5 24.7 16 .0107 2. 30 .362 do 38.0 32.3 29.7 26 .030 8.88 .948 Sand-silt-clay 2.65 1.60 99.8 39.6 .66 2.65 1.53 95.5 42.3 .73 2.66 1.64 102.3 38.3 .62 2.70 1.65 103.0 38.9 .64 2.67 1.67 104.2 37.5 .60 2.64 1.68 104.8 36.4 .57 2.63 1.64 102.3 37.6 .60 2.67 1.59 99.2 40.4 .68 2.52 1.41 88.0 44.0 .79 2.69 2.73 1.54 96.1 43.6 .77 2. 66 1.43 89.2 46.2 .86 2.48 2.69 1.64 102.3 39.0 .64 2.71 1.52 94.8 43.9 .78 2. 67 1.60 99.8 40.1 .67 2. 50 1.37 85.5 45.2 .83 2.69 1.54 96.1 42.8 .75 2. 76 1.59 99.2 42.0 .72 2.71 1.60 99.8 41.2 .70 2. 72 1.68 104.8 38.2 .62 2. 73 1.60 99.8 41.0 .70 2. 71 2.68 1.49 93.0 44.4 .80 .001 .006 .03 .0004 .002 .002 2. 67 0.4 2. 67 .8 2.72 1.68 104.8 38.2 0.62 .06 0.02 2.69 1.66 103.6 383 .62 .02 . 2 2.66 1.79 111.7 32.7 .48 .0005 .0008 2. 67 1.69 105.5 36.7 .58 .05 .0^ 2.68 1.32 82.4 50.7 1.02 .0004 .0005 2.69 1.05 65.5 61.0 1.56 .0004 .0004 2.68 1.66 103.6 38.1 1.61 38 2.72 1.57 98.0 42.3 .74 .01 .02 2.68 1.64 102.3 38.8 .63 .09 2.71 1.59 99.2 41.3 .71 .01 .01 2.71 1.64 102.3 39.5 .65 .01 .004 2. 72 1.62 101.1 40.4 .68 .01 .02 2.68 1.82 113.6 32.1 .46 .002 .02 2. 74 1.59 99.2 42.0 .73 .004 .1 2.70 1.55 96.7 42.6 .75 .06 2.69 1.58 98.6 41.3 .70 .0002 .0006 2.71 1.41 88.0 48.0 .93 .001 .0006 2.73 1.50 93.6 45.1 .83 .0005 .0006 2. 75 1.34 83.6 51.3 1.04 .002 .007 2.72 1.79 111.7 34.2 .51 .6 .09 2.69 1.52 94.8 43.5 .78 .005 2.68 1.69 105.5 36.9 .58 .2 2.70 1.66 103.6 38.5 .63 .01 .02 2.70 1.64 102.3 39.3 .65 .001 .004 2.72 1.53 95.5 43.8 .79 .002 .004 2.68 1.65 103.0 38.4 .63 .4 .2 2.69 1.53 95.5 43.1 .76 .0003 .002 2. 66 1.52 94.8 42.9 .76 .02 .02 2. 72 1. 55 96.7 43.0 .76 61 2. 74 1.57 98.0 42.7 .75 .001 .001 2.66 1.54 96.1 42.1 .73 .008 .03 2. 65 1. 48 92.4 44.2 .80 .0009 2. 75 1.52 94.8 44.7 .81 .04 2.68 1.70 106.1 36.6 .57 .05 .02 2. 66 1.60 99.8 39.8 .66 2 .005 2.68 1.67 104.2 37.7 .60 .05 .02 2.73 1.71 106.7 37.4 .59 .03 2. 70 1.69 105.5 37.4 .59 .007 2.69 1.56 97.3 42.0 .73 .005 .005 2.69 1.63 101.7 39.4 .65 .09 .05 2.67 1. 56 97.3 41.6 .72 . 1 .1 2.67 1.48 92.4 44.6 .81 .002 .003 2.71 1. 50 93.6 44.6 .81 .001 .008 2.66 1. 61 100.5 39.5 .65 .0002 See footnotes at end of table. PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A51Table 5.—Physical and hydrologic properties of samples from core holes—Continued Particle analysis, percentage of— Median Hydrologic laboratory sample Sample depth (feet) Gravel Sand Silt Clay <0.004 Clay <0.002 diameter, D50 (mm) mm mm Geometrical quartile deviation (sorting coefficient), So Log quartile deviation (log sorting coefficient), logio So Core hole 24/26-36A2 59CAL310 54.3- 54.8 6.2 59.3 19.5 15.0 13 0.255 2.63 0.420 311 63.4- 63.9 16.5 56.9 14.9 11.7 11 .355 4. 96 .695 312 84.6- 85.1 5.9 54.2 26.4 13.5 11 . 107 4. 45 .648 313 93.0- 93.5 1.8 49.5 31.6 17.1 13 .070 5.69 .755 314 102.6- 103.1 8.6 55.6 20.1 15.7 15 .170 5.84 .767 315 117.6- 118.1 7.3 51.4 21.8 19.5 16 .133 7. 76 .890 316 124. 2- 124.6 2.5 44.5 32.2 20.8 18 .053 4.66 .668 317 133.0- 133.5 1.8 43.8 37.0 17.4 13 .052 3.42 .535 318 142.6- 143.1 3.8 43.5 27.7 25.0 22 .0495 9.49 .977 319 148.0- 148.5 1.1 27.7 19.3 51.9 49 .0024 w p) 320 156.3- 156.8 .2 39.9 28.0 31.9 26 .036 8.85 .947 321 173.0- 173.5 1.6 26.0 50.4 22.0 16 .0245 3.59 .554 322 176.3- 176.8 3.6 57.3 24.3 14.8 10 .12 4. 48 .652 323 187.0- 187.5 28.5 61.9 4.3 5.3 5 1.09 2.28 .358 324 203. 5- 204.0 5.0 46.5 22.0 26.5 23 .076 14.14 1.150 325 210.0- 210.5 .9 37.9 44.7 16.5 12 .035 3.76 .576 326 220.5- 221.0 5.8 41.3 33.9 19.0 15 .0522 6.90 .839 327 231.6- 232.0 3.5 38.8 34.9 22.8 16 .040 5.79 .763 328 240. 2- 240.7 8.0 48.8 26.1 17.1 13 .103 6.13 .788 329 251.5- 251.9 33.9 57.9 2.6 5.6 5 1.30 2.13 .328 330 260. 2- 260.7 2.1 53.3 34.9 9.7 8 .078 2.41 .382 331 273. 5- 274.0 8.9 61.4 14.7 15.0 13 .295 5.15 .712 332 284. 5- 284.9 .2 59.7 28.1 12.0 10 .091 2.68 .428 333 289.8- 290.3 28.8 53. 7 17. 5 12 .028 334 300.5- 301.0 1.6 68.7 12.2 17.5 15 .170 3.79 .579 335 315.3- 315.8 1.3 56.3 28.6 13.8 12 .088 3.23 .509 336 318. 0- 318.5 1.0 61.0 29.4 8.6 7 . 103 2.73 .437 337 328. 5- 329.0 2.3 55.9 29.0 12.8 12 .099 4.13 .616 338 338.0- 338. 5 .4 47.8 35.5 16.3 13 .056 3. 74 .573 339 356. 8- 357.3 1.8 45. 6 39.0 13.6 12 .056 3.10 .492 340 358. 7- 359.2 3.3 63.6 21.9 11.2 8 .170 3. 79 . 578 341 370.0- 370.5 2.9 47.2 27.1 22.8 16 .0625 7.92 .899 342 374.3- 374.8 2.7 56.0 25.3 16.0 13 . 109 4.36 .640 343 389.1 389. 6 . 1 35.8 54.4 9.7 8 .037 2.33 .368 344 399. 0 399.5 3.4 45.2 32.4 19.0 14 .057 6.10 .785 345 403. 0- 403. 5 .4 49.8 27.3 22.5 17 .0625 6. 48 .812 346 414.9- 415.4 2.4 70.9 15.5 11.2 9 .23 3.40 .532 347 423. 0- 423.5 4.5 65.9 18.6 11.0 8 .21 3. 71 .569 348 433. 3- 433. 7 1.3 49.2 36.0 13.5 8 .064 3.17 . 501 349 443. 0- 443. 5 .7 39.3 39.9 20.1 14 .0305 5. 65 .752 350 458.5- 459.0 3.7 55.9 28.9 11.5 8 . 103 4. 26 .630 351 467.3- 467.8 2.0 49.6 34.1 14.3 10 .071 5.02 .701 352 474. 7- 475. 3 2.2 38.9 34.5 24.4 IS .038 6.26 .797 353 488.0- 488.5 .5 44.8 41.7 13.0 7 .051 2. 78 .443 354 494. 0- 494.5 .5 42.6 37.3 19.6 14 .0415 4.93 . 693 355 507.0- 507.5 .7 36.3 42.5 20.5 17 .0405 3. 79 .579 356 516. 3- 516.8 1.0 38.0 30.2 30.8 22 .0177 9.81 .992 357 531.0- 531.5 .4 46.6 46.1 16.9 12 .057 3.31 .520 358 533.1- 533.6 7.9 65.9 16.9 9.3 6 .240 3. 58 .554 359 544.0- 544.5 5.3 57.8 20.0 16.9 14 .139 4.95 .694 360 552.6- 553.1 5.0 73.3 10.9 10.8 10 .23 3.00 .477 361 565.1- 565.6 2.8 46.3 36.7 14.2 9 .060 2.89 .461 362 574.6- 575.1 2.0 30.4 47.3 20.3 15 .0225 4. 56 .659 363 582.6- 583.1 5.7 23.8 48.3 22.2 15 .0193 4.10 .612 364 595.1- 595.6 1.2 42.7 40.0 16.1 12 .046 4.28 .631 365 607.5- 608.0 .1 24.6 64.5 10.8 7 .038 2.25 .353 366 613.8- 614.3 .4 33.1 48.2 18.3 13 .0405 2.81 .449 367 623.0- 623.5 1.3 28.8 40.4 29.5 23 .019 5.68 .754 368 631.2- 631.7 .5 34.8 31.6 33.1 25 .0162 9.28 .968 369 648. 2- 648.7 .3 21.3 38.2 40.2 32 .007 5.66 .753 370 658.8- 659.3 .7 43.1 36.3 19.9 16 .046 4.32 .636 371 668.3- 668.8 1.2 56.1 25.7 17.0 14 .093 4.93 .693 372 678. 5- 679.0 4.1 55.6 29.3 11.0 8 .100 3.63 .560 373 686. 5- 686.9 .3 29.1 34.9 35.7 28 .0141 7. 55 .878 374.... 697. 5- 698. 0 58. 2 33.8 8. 0 6 375 709.0- 709.5 .8 61.7 28.0 9.5 7 .098 3.23 .509 376 719.4- 720.0 .2 41.1 47.0 11.7 8 .0395 3.10 .491 377 726.1- 726.6 .7 56.2 32.8 10.3 8 .084 3. 24 .511 377 735.4- 735.9 1.5 63.6 23.8 11.1 8 .178 4.35 .638 379 744. 0- 744.5 39.0 43.5 17.5 14 .033 4.14 617 Sediment class (Shepard system) 7~Ia/sLu Silty sand__________ ____do_______________ ____do.............. ____do_______________ ____do_______________ _____do.............. Sand-silt-clay...... Silty sand__________ Sand-silt-clay...... Sandy clay__________ Sand-silt-clay______ ____do_______________ Silty sand__________ Gravelly sand_______ Sand-silt-clay______ Sandy silt__________ Silty sand__________ Sand-silt-clay______ Silty sand__________ Gravelly sand_______ Silty sand__________ Clayey sand_________ Silty sand__________ Sandy silt.......... Clayey sand......... Silty sand__________ ____do_______________ ____do_______________ ____do_______________ .---do_______________ ____do_______________ Sand-silt-clay______ Silty sand__________ Sandy silt__________ Silty sand__________ Sand-silt-clay______ Silty sand__________ ____do_______________ ____do_______________ Sand-silt-clay______ Silty sand__________ ____do_______________ Sand-silt-clay______ Silty sand__________ ____do_______________ Sand-silt-clay______ ____do_______________ Silty sand__________ ____do_______________ ____do_______________ Sand________________ Silty sand__________ Sand-silt-clay______ ____do_______________ Silty sand__________ Sandy silt__________ ____do_______________ Sand-silt-clay______ ____do_______________ ____do_______________ Silty sand__________ ____do_______________ ____do_______________ Sand-silt-clay______ Silty sand__________ ____do_______________ Sandy silt......... Silty sand__________ ____do_______________ Sandy silt__________ Specific gravity of solids Dry unit weight G per Lb per cc cu ft Total porosity (percent) Void ratio Coefficient of permeability (gpd per sq ft at 60*F) Vertical Hori- zontal / 2.68 1. 79 111.7 33.2 0. 49 2.68 1.84 114. 8 31.3 .44 2.70 1.84 114.8 31.9 .46 2.70 1.78 111.1 34.1 .51 2.69 1.71 106.7 36.4 .57 .2 2 2. 70 1.83 114.2 32.2 .46 .5 2.71 1.78 111.1 34.3 .51 .02 .08 2.73 1.73 108.0 36.6 .58 .2 2.71 1.67 104.2 38.4 .61 .005 .1 2. 71 1.67 104.2 38.4 .61 .0002 .0003 2. 72 1.88 117.3 30.9 .43 .04 2. 70 1.61 100.5 40.4 .67 .04 2. 72 1.76 109.8 35.3 .54 2 2 2. 70 1.74 108.6 35.6 .55 2 20 2.71 1.66 103.6 38.7 .63 .06 3 2. 71 1.67 104.2 38.4 .61 .5 2. 70 1.82 113.6 32.6 .48 .02 J2 2. 70 1.78 111.1 34.1 .51 .001 2.71 1.85 115.4 31.7 .45 2.68 1.61 100.5 39.9 .66 5 2. 70 1.32 82.4 51.1 1.01 2 1 2. 72 1.77 110.4 34.9 .53 .1 . 1 2. 70 1.70 106.1 37.0 .59 .07 2. 73 1.63 101.7 40.3 .68 .2 2. 71 1.82 113.6 32.8 .49 2.71 1.67 104.2 38.4 .61 .01 .02 2.71 1.79 111.7 33.9 .50 . 1 2. 74 1.81 112. 9 33.9 .50 .06 2.76 1.77 110.4 35.9 .55 .003 .006 2. 72 1.86 116.1 31. 6 .45 2. 74 1.86 116.1 32.1 .51 .2 2.71 1.88 117.3 30.6 .43 .007 2. 75 1.90 118. 6 30.9 .43 .01 .5 2. 78 1.58 98.6 43.2 .75 .09 2. 76 1.88 117.3 31.9 .45 .003 .002 2. 76 1.75 109.2 36.6 . 57 .002 2. 73 1.77 110.4 35.2 . 54 .8 2 2. 73 1.77 110.4 35.2 .54 .1 2. 74 1.76 109.8 35.8 .55 . 1 . 1 2. 72 1.80 112.3 33.8 . 50 2. 74 1.81 112. 9 33.9 .50 .5 2. 74 1.66 103.6 39.4 .65 .02 .01 2.68 1.79 111.7 33.2 .48 .008 .04 2. 76 1.74 108.6 37.0 .59 .002 2.74 1.73 108.0 36.9 .59 .05 .03 2. 75 1.74 108.6 36.7 .58 .004 2. 75 1.77 110.4 35.6 .55 .001 2. 77 1.73 108.0 37.5 .61 .01 .04 2. 74 1.69 105.5 38.3 .63 3 2. 72 1.80 112.3 33.8 .50 2. 75 1.73 108.0 36.9 .59 3 3 2. 74 1.64 102.3 40.4 .67 .06 2. 76 1.68 104.8 39.1 .64 .01 2. 69 1.65 103.0 38.7 .63 .001 .03 2.71 1.94 121.1 28.4 .39 .001 2. 71 1.79 111.7 33.9 .50 .001 .03 2.71 1.70 106.1 37.3 .59 .006 2. 66 1.44 89.9 45.9 .85 2. 66 1.54 96.1 42.1 .73 .001 .002 2.67 1.56 97.3 41.6 .71 2.69 1.74 108.6 35.3 .54 .004 2. 70 1.72 107.3 36.3 .55 .005 .009 2.73 1.75 109.2 35.9 .55 .1 .1 2. 66 1.35 84. 2 49.2 .96 2. 72 1.56 97.3 42.6 .75 2 2 2. 74 1.81 112.9 33.9 .50 .08 2. 73 1.61 100.5 41.0 .69 .002 2.74 1.73 108.0 36.9 .57 .3 .2 2. 71 1.70 106.1 37.3 .59 .05 5 2.66 1.49 93.0 44.0 .79 A52 MECHANICS OF AQUIFER SYSTEMS380 756.9- 757.4 23.8 34.8 41.4 32 .0073 6.48 381 763.0- 763.5 33.8 18.4 47.8 40 .0052 382 — 775.6- 776.1 .3 39.9 35.5 24.3 18 .030 5. 51 383 777.7- 778.2 5.4 33.7 42.9 18.0 12 .039 3.55 384 791.7- 792.2 18.4 26.5 55.1 46 .0027 c) 385 - 843.3- 843.8 4.4 69.3 26.3 17 .0109 2.27 386 852.0- 852.5 10.2 75.6 14.2 10 .023 2.11 387 861.0- 861.5 .4 65.5 14.4 19.7 18 .127 3.96 388 866.3- 866.8 25.2 64.3 10.5 4 .0285 2.28 389 — 916.4- 916.9 6.0 67.6 26.4 18 .0101 2.45 390 1,036.3-1,036.8 15.8 36.6 47.6 38 .0045 (>) 391 .. 1,058.0-1,058.5 34.0 61.4 4.6 3 .0385 2.23 392 1,099.1-1,099.6 26.0 61.9 6.6 5.5 4 .62 2.70 393 1,116.8-1,117.8 .3 44.9 27.0 27.8 22 .040 7.72 394 —. 1,155.4-1,155.9 .7 28.0 39.3 32.0 24 .0148 6.53 395 1,184.3-1,184.7 1.6 52.0 29.0 17.4 15 .076 4.06 396 1,240.5-1,241.0 23.8 38.2 38.0 29 .0106 6. 21 397 1,363.0-1,363.5 24.4 51.3 24.3 22 .0182 3. 59 398 1,369.5-1,370.0 .3 66.4 15.3 18.0 16 .140 3.58 399 1,421.2-1,421.7 .2 60.7 15.1 24.0 20 .226 10.20 400 1,431.0-1,431.5 60.6 16.6 22.8 19 . 155 9.91 401 1,446.9-1,447.4 23.4 46.6 30.0 25 .0153 5.13 402 1^ 492.0-1! 492. 5 .3 73.2 10.9 15.6 14 .157 2.23 403 1,526.6-1,527.1 23.6 45.9 30.5 25 .0138 5.16 404 1,688. 0-1,688.5 30.4 36.1 33.5 29 .0098 9. 20 405 1,720.4-1.720.9 61.8 30.8 7.4 4 . 110 2. 51 406 1,751.7-1,752.2 8.0 53.7 26.0 12.3 7 .0920 2. 60 407 1,785. 0-1,785.5 .2 60.5 34.6 4.7 3 .117 2.69 408 1,802. 5-1,803.0 .5 65.1 23.6 10.8 10 .097 2. 48 409 1,814. 0-1,814.5 6.6 76.6 12.2 4.6 3 . 178 2.84 410 1,826.5-1,827.0 31.6 40.5 27.9 8 .0142 5.02 411 1,892.2-1,892.7 41.4 36.6 22.0 17 .038 4.96 412 1,911. 5-1,.912.0 65.2 20.8 14.0 12 .083 1. 782 413 1,943.2-1,943. 7 91.6 8. 4 (3) . 14 1.245 414 lj 955. 5-b 956.0 1.6 95.9 2. 5 (s) .55 1.605 415 1,964.1-1,964.6 5.5 89.8 4.7 .74 1.691 416 2,010.0-2,010. 5 2.4 93.9 3.7 (?) .81 1. 455 417 2,051.0-2,051.5 7.2 88.3 4.5 (3) .30 2. 35 418 2,102. 0-2,102. 5 37.5 58.4 4. 1 (s) 1.35 2.96 419 2,174. 0-2,174. 5 .2 90.4 9.4 (s) .255 1.608 (') (?) « .812 2.66 1.35 84.2 49.2 .96 2.003 2.66 1.34 83.6 49.6 .98 .742 2.77 1.56 97.3 43.7 .78 .61 .550 2.79 1.56 97.3 44.1 .79 .07 2.76 1.29 80.5 53.3 1.12 .356 2.76 1.41 88.0 48.9 .92 .003 .324 Silt 2. 74 1.48 92.4 46.0 .86 .006 .598 2.75 1.74 108.6 36.7 .58 .0007 .358 2.75 1.39 86.7 49.5 .98 .05 .390 Clayey silt _ 2.75 1.46 91.1 46.9 .88 .0006 .02 2.77 1.38 86.1 50.2 1.00 .004 .348 Sandy silt... 2.41 1.07 66.8 55.6 1.24 .04 10 .431 2.70 1.59 99.2 41.1 .70 .888 Sand-silt-clay 2.72 1.29 80.5 52.6 1.10 .04 .7 .815 .. ..do 2.72 1.26 78.6 53.7 1.14 .001 .04 .608 Silty sand 2. 74 1.31 81.7 52.2 1.08 .09 2 .793 Sand-silt-clay 2.60 1.06 66.1 59.2 1.46 .0005 .001 .555 do 2.64 1.25 78.0 52.7 1.06 .0005 .001 .554 Clayey sand 2.70 1.43 89.2 47.0 .89 .003 .01 .009 2.65 1.25 78.0 52.8 1.10 .01 .996 do 2.65 1.29 80.5 51.3 1.04 .01 2 .710 Sand-silt-clay 2. 58 1.00 62.4 61.2 1.50 .004 .006 .348 2.70 1.58 98.6 41.5 .71 .4 .712 Sand-silt-clay 2.66 1.13 70.5 57.5 1.35 .001 .004 .964 do 2.75 1. 37 85. 5 50.2 1.00 .002 .6 .400 Silty sand 2.75 1. 47 91.7 46. 5 0.85 1 6 .414 do 2.76 1.40 87.4 49.3 .97 6 6 .431 do 2. 73 1. 50 93.6 45.1 .83 4 3 .395 do 2. 71 1.41 88.0 48.0 .91 5 .454 2. 69 1. 65 103.0 38.7 .63 4 .701 2. 62 1.26 78. 6 51.9 1.06 5 .696 do 2.72 1.17 73.0 57.0 1.31 2.0009 .251 2.74 1.71 106.7 37.6 . 60 .002 . 095 2.69 1.54 96.1 42.8 .74 2 .206 2.67 1.60 99.8 40.1 .67 650 .228 do 2. 66 1.63 101.7 38.7 .63 15 .163 do 2. 65 1.62 101.1 38.9 .64 18 3 .371 do 2. 66 1.67 104.2 37.2 .58 60 . 471 2. 67 1.70 106.1 36.3 . 55 60 .206 2.68 1.64 102.3 38.8 .63 90 Core hole 6S/2W-24C7 60CAL10 36. 5- 37.0 1.0 34.5 45.5 19.0 16 11 50± 1.8 15.7 46.4 36.1 29 12 71.4- 71.9 19.6 49.3 31.1 26 13 90.4- 90.8 6.8 37.7 55.5 44 14 100.4- 100.9 3.0 51.2 45.8 32 15 112.4- 112.9 2.2 26.0 71.8 52 16_ . 120.3- 120.8 .4 41.5 58.1 38 17 131.0- 131.5 10.6 67.1 22.3 17 18 140.8- 141.4 2.8 15.4 34.6 47.2 39 19 _ 151.0- 151.5 5.0 38.4 56.6 42 20 160.0- 160.5 1.4 38.1 60.5 44 178.0- 178.5 14.2 45.5 40.3 32 *22 191.3- 191.8 1.3 18.4 37.8 42.5 34 23 210.1- 210.6 24.4 57.9 17.7 14 24 222.3- 222.8 1.2 46.8 52.0 36 25 228.4- 228.9 1.1 31.5 47.4 20.0 14 26 236.0- 236.5 2.7 27.2 46.7 23.4 17 27 253.4- 253.8 1.0 25.9 56.0 17.1 14 28 307.0- 307.4 4.6 57.7 37.7 30 29 312.8- 313.3 11.4 51.7 36.9 29 30 330.0- 330.5 14.0 46.5 39.5 29 31 344. 4- 344.8 21.2 52.3 26.5 21 32 361.3- 361.8 3.0 17.8 41.7 37.5 27 34 419.6- 420.1 39.6 39.4 21.0 18 35 431.5- 342.0 .6 29.2 42.0 28.2 24 36 436. 7- 437.2 1.7 31.3 39.2 27.8 23 37 446.0- 446.5 25.2 36.2 38.6 27 39. 463.0- 463.5 — 39.2 36.1 24.7 21 40 522.5- 522.9 .1 23.8 41.1 35.0 27 41 545.0- 545.5 42 554.7- 555. 2 .7 36.7 38.4 24.2 21 43 563.2- 563.7 15.6 45.8 38.6 31 44 574.3- 574.8 7.0 56.0 37.0 28 45 605.3- 605.8 1.3 29.0 36.7 33.0 28 46 633.8- 634.3 36.6 37.1 26.3 22 47 656.5- 656.9 .1 26.6 32.6 40.7 33 48 665.5- 665.9 1.5 24.0 47.0 27.5 22 036 3.46 0.539 Sandy silt 2.70 1.61 100.5 40.4 .68 Oil 2.72 1.61 100. 5 40.8 .69 0123 4.94 .694 £/do 2.75 1.67 104.3 39.3 .65 0029 2. 73 1. 51 94.3 44.7 .81 .005 3.23 .509 Clayey silt 2.75 1.48 92.4 46.2 .86 .0018 2.71 1.44 89.9 46.9 .88 0031 2.72 1.44 89.9 47.1 .89 .014 2.53 .403 Clayey silt 2.67 1.55 96.8 41.9 .72 .005 2.74 1.63 101.8 40.5 .68 .003 2.74 1.43 89.3 47.8 .92 .0027 2.74 1.55 96.8 43.4 .77 .0073 2.73 1.61 100.5 41.0 .69 .0070 2.69 1.70 106.1 36.8 .58 .029 2.75 .439 £andy silt 2.72 1.61 100.5 40.8 .69 .0037 2.68 1.52 94.9 43.3 .76 .027 3. 70 .568 Sandy silt 2. 72 1.67 104.3 38.6 .63 .022 4.07 .609 Sand-silt-clay 2.75 1.70 106.1 38.2 .62 .028 2.93 .467 S^ndy silt 2.71 1.74 108.6 35.8 .56 .0075 2.72 1.71 106.8 37.1 .59 .0075 4.30 .634 4rl_.do 2.69 1.67 104.3 37.9 .61 .007 4.24 .627 ^\f-.do 2. 74 1.71 106.8 37.6 .60 .017 3.78 .577 Sand-silt-clay 2. 72 1.67 104.3 38.6 .63 .0084 4.53 .056 -.do 2.72 1.71 106.8 37.1 .59 .007 2.72 1.73 108.0 36.4 .57 .035 4.28 .631 Sand-silt-clay 2.73 1.84 114.9 32.6 .48 .0205 5.66 .753 do 2. 74 1.70 106.1 38.0 .61 .022 6.19 .792 2.71 1.74 108.6 35.8 .56 .0071 6.06 .782 v do 2.75 1.54 96.1 44.0 .79 .0152 3.08 .439 UDlayey silt 2.75 1.67 104.3 39.3 .65 .038 4.88 .688 Sand-silt-clay 2. 72 1.73 108.0 36.4 .57 .011 5.86 .768 -----do 2.73 1.74 108.6 36.3 .57 .0089 3.73 .572 tClayey silt 2.73 1.68 104.9 38.5 .63 .038 4.66 .668 Sand-silt-clay 2. 74 1.79 111.7 34.7 .53 .008 5.16 .713 ■^Clayey silt 2.71 1.63 101.8 39.9 .66 .0081 4.06 .609 do 2.71 1.58 98.6 41.7 .71 .020 7.51 .876 Sand-silt-clay 2.71 1.74 108.6 35.8 .56 .028 5.80 .763 do 2.75 1.77 110.5 35.6 .55 .0082 2.72 1.82 113.6 33.1 .49 .023 4.56 .659 do 2.72 1.76 109.9 35.3 .54 0.001 0. 001 .0005 .0008 .0004 .0007 .002 .002 .004 .002 .0006 .0007 .01 .1 .004 .001 .004 .005 .009 .0002 .0004 .008 .009 .009 .02 .006 .3 .0001 .003 .002 .002 .008 .005 .03 .001 .005 .003 .0007 .007 .0003 .001 .001 .002 .002 .0004 .08 .0004 .03 .0003 .001 . 001 See footnotes at end of table. PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A53Table 5.—Physical and hydrologic properties of samples from core holes—Continued Particle analysis, percentage of— Median Geometrical quartile Log quartile Specific Dry unit weight Coefficient of permeability (gpd per sa ft at 60°F) Hydrologic laboratory Sample depth (feet) diameter, deviation deviation Sediment class gravity Total Void Clay Clay (sorting (log sorting (Shepard system) of porosity (percent) ratio sample Gravel Sand Silt <0.004 mm <0.002 mm (mm) coefficient), So coefficient), logio So solids G per cc Lb per cu ft Vertical Hori- zontal Core hole 6S/2W-24C7—Continued 60CAL49 715.5- 716.1 11.4 35.5 53.1 41 .0033 / ,■ 2.70 1.68 104.9 37.8 .61 .0007 .0005 50 735.3- 735.8 31.4 40.8 27.8 25 .028 6.07 .783 2.71 1.82 113.6 32.8 .49 51 _ . 744.9- 745.4 6.0 36.5 57.5 43 .0027 2.72 1.50 93.6 44.9 .81 .0005 .001 52 756.4- 756.9 7.2 28.7 64.1 52 .0018 2.70 1.56 97.4 42.2 .73 63 773.0- 773.5 5.0 62.5 32.5 20 .0078 2.51 .400 2.70 1.57 98.0 41.9 .72 54 789.5- 790.0 5.2 43.6 51.6 38 .0037 3.44 .537 2.74 1.60 99.9 41.6 .71 .0002 .006 55 796.5- 797.0 53.6 36.3 10.1 8 .068 1.91 .281 ✓Silty sand 2.75 1.62 101.1 41.1 .70 57 824. 2- 824.7 1.2 62.0 36.8 26 .0082 3.42 .534 2.74 1.74 108.6 36.5 .57 58. 835.3- 835.8 88.0 7.7 4.3 4 . 165 1.34 . 127 2.74 1. 51 94.3 44.9 .81 59 842.2- 842.7 .2 51.5 48.3 33 . 0043 3.02 .480 2. 77 1. 60 99.9 42.2 .73 . 0008 60 854.1- 854.6 2.6 27.9 69.5 52 .0019 2.73 1.67 104.3 38.8 .63 61 S65r«- 866.A. 1.0 27.2 71.8 53 .0018 - 2.79 1.67 104.3 40.1 .67 .0002 .0008 63 882 8- 883.3 17.8 48.8 33.4 28 .016 5.92 .772 —do 2.72 1.85 115. 5 32.0 . 46 .47 65 ... 910.0- 910.5 4.0 mS 61.8 45 .0025 j>nty ciay ...... 2. 73 l! 57 98.0 42.5 .74 66 67 . b- 936. 6- wZ4. 1 937.1 9.2 20. 0 22.7 77. 0 68.1 -62 61 . 0013 rClay. 2.70 1. 52 1.34 94. 9 83.7 43. 7 50.4 .78 1.02 . 004 . 007 68—. 958.3- 958.8 21.8 36.4 41.8 33 . 008 7.14 .854 2.71 1. 65 103.0 39.1 . 64 .0008 .006 69 967.0- 967. 5 11.2 45.1 43.7 37 .007 2.69 1. 68 104.9 37.5 .60 Core hole 7S/1E-16C6 60CAL70 196.3- 196.8 0.1 24. 6 27.8 47. 5 42 0. 0052 2. 72 1.64 102.4 39.7 0. 66 0.00007 0. 0007 71 206.4- 206.9 24.6 54.9 20.5 16 .024 3.22 0.508 2. 70 1. 59 99.3 41.1 .70 .01 >72 232.5- 233.0 5.4 52.0 42.6 31 .0056 3. 61 .558 2.80 1.62 101.1 42.1 .73 .0006 .0006 *73 258.0- 258. 5 3.3 14.8 46.6 35.3 30 .013 (rr:..dO 2. 79 1. 65 103.0 40.9 . 69 . 0002 -74. 275. 4- 275.8 . 1 18.0 55.9 26.0 21 .016 3. 55 .550 !tr__do 2.75 1. 60 99.9 41.8 .72 .007 .004 75.. . 301.6- 301. 5 1.5 22.1 47.0 29.4 25 .020 5.29 .723 2.72 1.74 108. 6 36.0 . 56 .002 .002 76 323.8- 324.3 1.4 90. 5 8.1 (3) .257 1.28 .107 2.72 1. 69 105. 5 37.9 . 61 .6 334.1- 334. 4 1.2 51. 6 47.2 34 .0045 2. 68 1. 59 99.3 40.7 . 69 . 0002 78 354.5- 355.0 .1 45.6 38.9 15.4 12 .054 2.47 .393 , Silty sand 2.71 1. 73 108.0 36.2 .57 .03 .07 401. 3- 401 8 .2 47.1 52.7 40 . 0035 "Silty clay. 2.72 1. 55 96.8 43.0 .75 . 0003 . 001 80 430.1- 430.6 .2 27.3 43.1 29.4 24 .018 5.51 .741 2.72 1.75 109.3 35.7 .56 .0001 .0008 81... 440.6- 441.1 .3 75.2 16.8 7.7 6 . 134 1.76 .246 2.77 1.65 103.0 40.4 .68 .4 82. 509. 5- 510.0 5.8 28.6 35.9 29.7 25 .024 7.68 .885 2.72 1.77 110.5 34.9 .54 .0005 .0002 83 530.7- 531.2 1.2 30.4 41.2 27.2 24 .025 5.98 .777 2.76 1.83 114.2 33.7 .51 . 0001 . 0003 84 554.3- 554.8 . 6 40.4 38.0 21.0 16 .037 4. 52 .655 2.74 1.86 116.1 32.1 .47 . 004 .003 85... 569.7- 570.2 .2 33. 5 44.9 21.4 18 .031 2.52 .547 2. 75 1.88 117.4 31.6 .46 .002 86 598.8- 599. 3 4.4 42.1 35.0 18.5 16 .050 3.91 .592 2. 76 1.86 116.1 32.6 .48 .004 .001 87 696. 3- 696.8 2.4 21.1 46.4 30.1 25 .014 4. 74 .676 2.75 1.77 110.5 35.6 .55 .005 .005 88 704.8- 705.2 6.2 58. 5 21.8 13. 5 11 .162 3.85 .585 2. 75 1.91 119.2 30.5 .44 . 02 89 724. 4- 724.9 . 5 20. 5 41.9 37.1 33 .013 2.72 1.81 113.0 33. 5 . 50 . 0002 . 002 90.. 750.1- 750. 5 45.6 49.0 5.4 (3) 1.500 3.53 .548 2.79 1.67 104.3 40.1 .67 19 91 790.6- 791.1 .7 27.2 46.0 26.1 19 .023 4. 47 .650 2. 76 1. 74 108.6 37.0 .59 .0003 .0007 .'.92 811. 6- 812.2 15.8 66.9 17.3 13 .024 2.41 .382 2.76 1.63 101.8 40.9 .69 . 01 93 -. 832.4- 832.9 21.0 54.8 24.2 19 .019 3.50 .544 2. 79 1. 78 111.1 36.2 .57 .0005 .0006 94 845.2- 845.8 20.8 60.2 19.0 16 .025 2.88 .459 2. 76 1.77 110.5 35.9 .56 . 005 95 908.2- 908.7 18.0 54.7 27.3 22 .016 3.87 .588 2.76 1.80 112.4 34.8 .53 . 0002 . 0003 '96 937.4- 937.9 .1 15.8 49.8 34.3 28 .012 4.83 .684 7 do. 2. 77 1.64 102.4 40.8 .69 .0001 .002 1 Nondeterminable. Repacked sample. 3 Not measured. A54 MECHANICS OF AQUIFER SYSTEMSPROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A55 Table 6.—Atterberg limits and indices of samples from core holes Hydrologie Percent Volumetric Linear Laboratory Depth (feet) passing Liquid Plastic Shrinkage Plasticity Flow Toughness Shrinkage Shrinkage sample No. 40 sieve limit limit limit index index index index ratio shrinkage shrinkage Core hole 14/13-11D1 57CAL1 77. 0- 77. 5 100 28 27 19 1 6 0.2 8 1.7 15 4 2 110.5- 111.0 99 56 26 (0 30 16 1.9 0 0 0 0 4 191.5- 192.0 100 33 24 15 9 8 1.1 9 1.8 32 8 5a 232.5- 233.0 100 44 29 12 15 6 2.5 17 2.0 64 15 7 314.0- 314.5 100 34 24 18 10 8 1.3 6 1.7 27 8 9 398.0- 398.5 100 64 40 13 24 19 1.3 27 1.9 97 20 10 432.0- 432.5 100 59 36 12 23 28 .8 24 1.9 89 19 12... 510.3- 510.8 97 65 40 8 25 11 2.3 32 2.0 114 22 14 594.0- 594.5 100 82 39 9 43 22 2.0 30 1.9 139 25 16 646.6- 647.1 100 78 38 17 40 17 2.4 21 1.8 110 22 18 662.1- 662.6 100 80 44 24 36 11 3.3 20 1.6 90 19 19 674.0- 674.5 100 78 46 28 32 9 3.6 18 1.4 70 16 21 697.0- 697.5 100 67 36 28 31 11 2.8 8 1.5 58 14 23 713.0- 713.5 100 52 33 31 19 9 2.1 2 1.4 29 8 25 731.0- 731.5 100 58 34 15 24 26 .9 19 1.8 77 17 26 743.0- 743.5 100 46 28 21 18 19 .9 7 1.6 40 11 27 757.0- 757.5 98 30 0 27 « 11 0 0 1.5 4 1 28 764.9- 765.4 65 38 30 26 8 6 1.3 4 1.6 19 5 31 791.0- 791.5 100 40 30 20 10 10 1.0 10 1.7 34 9 32 802.0- 802.5 100 34 26 24 8 13 .6 2 1.7 17 5 35 826.0- 826.5 100 65 43 20 22 14 1.6 23 1.7 77 17 36 831.5- 832.0 100 31 26 19 5 25 .2 7 1.7 20 6 39 860.0- 860.5 100 42 31 23 11 10 1.1 8 1.6 30 8 43 887. 5- 888.0 100 76 29 13 47 42 1.1 16 1.9 120 23 44 901.0- 901.5 100 40 30 23 10 15 .7 7 1.6 27 8 47 932.0- 932.5 99 47 23 10 24 9 2.7 13 2.0 74 17 48 936.5- 937.0 100 33 29 20 4 16 .2 9 1.7 22 6 49 951.0- 951.5 100 34 27 13 7 6 1.2 14 1.9 40 11 51 968.5- 969.0 100 41 33 17 8 12 .7 16 1.8 43 11 52 984.0- 984.5 100 59 29 10 30 15 2.0 19 2.0 98 20 54 1,000. 5-1,001.0 100 40 24 12 16 8 2.0 12 1.9 53 14 55.... 1,005.1-1,005.6 100 50 29 11 21 14 1.5 18 2.0 78 17 56 1,020. 8-1,021. 3 100 36 31 17 5 7 .7 14 1.8 34 9 38 1,039. 5-1,040. 0 100 47 34 12 13 10 1.3 22 1.9 67 16 59 1,051. 5-1,052. 0 100 33 24 17 9 10 .9 7 1.8 29 8 61 1,070. 8-1,071. 3 100 30 21 16 9 11 .8 5 1.8 25 7 65 1,104. 6-1,105.1 88 25 22 15 3 15 .2 7 1.8 18 5 68 1,133. 0-1,133. 5 100 36 24 16 12 10 1.2 8 1.8 36 10 75 1,242. 0-1,242.5 100 51 36 25 15 26 .6 11 1.5 39 11 83 1,312. 0-1,312. 5 98 26 18 18 8 4 2.0 0 1.8 14 4 86 1,339. 5-1,340.0 100 36 26 23 10 6 1.7 3 1.6 21 6 88 1,357.0-1,357. 5 100 46 23 10 23 14 1.6 13 2.0 72 17 89 1,362. 5-1,363. 0 100 32 21 18 11 16 .7 3 1.7 24 7 91 1,385. 0-1,385.5 100 54 36 13 18 12 1.5 23 1.8 74 17 92 1,397. 0-1,397. 5 98 61 41 5 20 17 1.2 36 2.1 118 23 96 1,432. 5-1,433.0 100 77 38 4 39 14 2.8 34 2.3 168 28 97 1,446. 0-1,446.5 100 56 28 5 28 15 1.9 23 2.2 112 22 98 1,454.5-1,455.0 100 44 33 16 11 9 1.2 17 1.7 48 13 99 1,465. 0-1,465.5- 100 58 34 8 24 11 2.2 26 2.1 105 21 Core hole 16/15-34N1 58CAL2 298.2- 298.7 98 38 30 13 8 11 0.7 17 1.9 48 13 3 332.4- 332.9 98 40 26 12 14 14 1.0 14 1.9 53 14 5 418.5- 419.0 100 44 30 13 14 11 1.3 17 1.9 59 15 6 454.3- 454.8 99 54 37 8 17 23 .7 29 2.0 92 20 9 509.5- 510.0 100 46 35 15 11 18 .6 20 1.8 56 14 11 532. 4- 532.9 97 42 34 12 8 9 .9 22 1.9 57 14 12 552.8- 553.2 100 45 32 11 13 8 1.6 21 1.9 65 16 13— 563.7- 564.2 100 56 46 12 10 13 .8 34 1.9 84 18 14 570. 7- 571.2 100 70 58 9 12 18 .7 49 2.0 122 23 19 636.4- 636.9 99 61 52 20 9 14 .6 32 1.6 66 16 20 643.2- 643.7 99 31 25 22 6 19 .3 3 1.6 14 4 21 652.6- 653.1 96 32 26 12 6 12 .5 14 1.8 36 10 22 666.0- 666.5 100 55 43 15 12 15 .8 28 1.8 72 17 24 683. 7- 684.2 100 36 30 19 6 16 .4 11 1.7 29 8 25 696. 6- 697.1 100 59 42 12 17 8 2.1 30 1.8 85 18 26 701.8- 702.4 100 42 32 17 10 18 .6 15 1.7 43 11 27 713.4- 713.9 99 61 40 7 21 16 1.3 33 2.0 108 22 29 732.0- 732.6 100 39 28 18 11 12 .9 10 1.7 36 10 31 753.8- 754.3 100 41 30 14 11 17 .6 16 1.8 49 13 32 762.4- 762.9 100 46 33 7 13 14 .9 26 2.0 78 17 33 773.3- 773.8 100 30 26 19 4 10 .4 7 1.7 19 5 36 806.1- 806.6 100 55 40 12 15 15 1.0 28 1.8 77 17 38 822.1- 822.6 98 60 49 10 11 12 .9 39 1.9 95 20 39 827.8- 828.2 100 47 33 13 14 20 .7 20 1.8 61 15 40 837. 7- 838.2 100 58 43 14 15 17 .9 29 1.8 79 18 42 860.1- 860.6 100 31 24 22 7 13 .5 2 1.6 14 4 43 866. 7- 867.3 100 30 23 18 7 7 1.0 5 1.7 20 6 45 891.6- 892.1 100 53 41 11 12 15 .8 30 1.9 80 18 48 922.6- 923.1 100 46 35 13 11 14 .8 22 1.8 59 15 49 931. 2- 931.7 100 35 28 15 7 12 .6 13 1.8 36 10 50 940.6- 941.1 100 46 36' 9 10 8 1.2 27 2.0 74 17 51 946.3- 946.8 100 63 43 7 20 22 .9 36 2.0 112 22 52.. 963.7- 964.2 100 37 28 16 9 14 .6 12 1.8 38 10 53 971.5- 972.0 100 57 46 16 11 20 .6 30 1.7 70 16 54.. 980.6- 981.1 100 35 0 27 o 14 0 <*) 1.5 12 3 58 1,042.8-1 043.3 100 51 45 14 6 13 .5 31 1.8 67 16 61 1,189.5-1,190.0 100 47 34 16 13 24 .5 18 1.8 56 14 63 1,225.0-1 225.5 100 38 34 25 4 14 .3 9 1.6 21 6 64 1,238.1-1,238.6 100 47 36 17 11 16 .7 19 1.7 51 13 66 1,254.9-1 255.4 100 41 36 30 5 7 .7 6 1.4 15 4 See footnotes at end of table.A56 MECHANICS OF AQUIFER SYSTEMS Table 6.'—■Atterberg limits and indices of samples from core holes—Continued Hydrologie Percent Laboratory Depth (feet) passing Liquid Plastic Shrinkage Plasticity Flow Toughness Shrinkage Shrinkage Volumetric Linear sample No. 40 sieve limit limit limit index index index index ratio shrinkage shrinkage Core hole 16/15-34N1—Continued 58CAL67 1, 280. 2-1,280. 7 100 48 41 24 7 21 0.3 17 1.6 38 10 70 1,351.4-1,351.9 100 42 36 31 6 32 .2 5 1.4 15 4 77 1,432. 0-1,432.5 97 48 42 20 6 12 .5 22 1.7 48 13 79 1,476.0-1,476.5 100 50 34 13 16 14 1.1 21 1.9 70 16 83 1,507. 2-1,507. 7 98 56 38 10 18 19 .9 28 2.0 92 19 86 1,558.1-1,558.6 100 37 27 14 10 10 1.0 13 17. 39 11 89 1,631.2-1,631.7 100 50 32 23 18 14 1.3 9 1.6 43 11 90 1,676.6-1,677.1 100 44 31 18 13 8 1.6 13 1.7 44 12 91 1,714.1-1,714.5 99 76 59 29 17 12 1.4 30 1.4 66 16 96 1,916.9-1,917.4 100 66 44 17 22 32 .7 27 1.7 83 18 Core hole 19/17-22J1, 2 57CAL104 89.6- 90.0 100 48 28 12 20 15 1.3 16 2.0 72 17 107 271. 2- 271.7 99 55 31 16 24 11 2.2 15 1.9 74 17 108 310.0- 310.5 98 26 21 17 5 8 .6 4 1.8 16 5 109 350.3- 350.8 100 49 30 16 19 10 1.9 14 1.8 59 15 111 430.9- 431.4 99 46 25 9 21 20 1.0 16 2.0 74 17 112 476.0- 476.4 100 58 33 14 25 16 1.6 19 1.9 84 18 114 553.9- 554.4 100 40 26 18 14 14 1.0 8 1.8 40 11 120 732.0- 732.5 100 43 29 20 14 13 1.1 9 1.7 39 11 121 745.7- 746.2 99 46 33 17 13 14 .9 16 1.7 49 13 123 778.8- 779.3 100 60 44 27 16 14 1.1 17 1.6 53 14 124 789.1- 789.6 100 35 32 26 3 13 .2 6 1.6 14 4 125 799.6- 800.0 100 48 35 17 13 8 1.6 18 1.8 56 14 128 860. 7- 861.2 100 35 30 22 5 9 .6 8 1.7 22 6 131... 886. 6- 889.1 100 65 44 12 21 26 .8 32 1.9 101 21 134 945.4- 945.9 100 48 37 13 11 8 1.4 24 1.8 63 15 135 948.0- 948.5 100 52 35 12 17 15 1.1 23 1.9 76 17 137 971.5- 971.9 100 54 37 18 17 15 1.1 19 1.8 65 16 138 982.8- 983.2 100 50 35 21 15 13 1.2 14 1.7 49 13 139 993. 4- 993.9 100 31 30 23 1 7 .1 7 1.6 13 4 141 1, 028. 0-1 028.5 100 55 38 17 17 10 1.7 21 1.8 68 16 144 1,093.8-1 094.3 100 47 36 22 11 9 1.2 14 1.7 43 11 145 1,104.3-1 104.7 100 57 39 20 18 11 1.6 19 1.7 63 15 146 1,119.6-1 120.1 100 47 35 17 12 12 1.0 18 1.8 54 14 148 1,143.3-1 143.8 100 59 42 14 17 13 1.3 28 1.9 86 19 153 1, 209.1-1 209.6 100 41 34 26 7 12 .6 8 1.6 24 7 161 1,321.0-1 321.5 100 50 32 14 18 10 1.8 18 1.8 65 16 167 1,427.9-1 428.4 100 45 30 12 15 10 1.5 18 1.9 63 15 171 1,484.1-1 484.6 100 42 31 19 11 9 1.2 12 1.6 37 10 178 1,574.9-1 575.4 100 34 26 21 8 5 1.6 5 1.7 22 6 181 1,615.0-1 615.5 100 39 31 20 8 7 1.1 11 1.7 32 9 187 1,718.8-1 719.2 99 52 31 9 21 14 1.5 22 1.9 82 18 200 1,956.3-1 956.7 99 48 27 21 21 10 2.1 6 1.7 46 12 201 1,976.0 100 61 36 21 25 14 1.8 15 1.7 68 16 202 1,993.0-1 993.5 99 60 33 32 27 12 2.2 1 1.4 39 11 205 2,064.0-2 064.5 100 56 31 11 25 4 6.2 20 2.0 90 19 Core hole 23/25-16N1 58CAL100 70.3- 70.4 100 35 29 21 6 9 0.7 8 1.6 22 6 102 155.1- 155.6 98 22 (*> 16 0 5 0 0 1.9 11 3 103 193. 5- 194.0 91 25 (•) 18 o 5 0 0 1.8 13 4 105 268.3- 268.8 91 27 21 16 6 8 .8 5 1.9 21 6 106 287.2- 287.7 100 56 38 24 18 9 2.0 14 1.6 51 13 107 294.6- 295.2 100 63 48 19 15 12 1.2 29 1.7 75 17 109 316. 4- 316.9 98 34 25 15 9 14 .6 10 1.8 34 9 112 343.0- 343.5 99 38 29 12 9 5 1.8 17 1.9 49 13 113 352.8- 353.3 100 35 27 13 8 6 1.3 14 1.9 42 11 114 362.5- 363.0 92 23 c) 15 0 8 0 0 1.9 15 4 115 370.3- 370.8 96 31 28 19 3 14 .2 9 1.8 22 6 117 427.1- 427.7 100 40 28 9 12 10 1.2 19 2.0 62 15 120 465.0- 465.5 100 45 36 18 9 9 1.0 18 1.7 46 12 122 482. 0- 482.5 100 45 37 12 8 11 .7 25 1.9 63 15 124 508.8- 509.3 96 29 17 0 8 0 0 1.8 22 6 127— 534.0- 534. 5 23 (3) (3) (2) (2) 1. 6 (*) 129 560.6- 561.1 100 31 (») 18 0 14 0 0 1.7 22 6 131 594.5- 595.0 100 39 26 15 13 6 2.2 n 1.8 43 11 133.. 616. 0- 616.4 92 36 26 14 10 10 1.0 12 1.9 42 11 135 630.7- 631.2 98 26 « 23 0 13 0 0 1.6 5 1 137 654.1- 654.6 97 31 0 17 0 9 0 0 1.8 25 7 138 660.0- 660.5 99 22 (3) (2) 1.6 140 682.7- 683.2 100 34 0 19 0 II 0 0 1.7 26 7 141 694.0- 694.5 98 24 0 20 0 14 0 0 1.7 7 2 143 723.8- 724.3 100 36 22 11 14 10 1.4 11 2.0 50 13 145 748.0- 748.5 96 40 26 12 14 14 1.0 14 2.0 56 14 Core hole 24/26-36A2 59CAI 313... 93.0- 93.5 80 22 18 16 4 6 0.7 2 1.9 11 3 316 124.2- 124.6 88 28 19 14 9 8 1.1 5 1.9 27 8 317 133.0- 133.5 88 25 19 17 6 8 .8 2 1.8 14 4 318 143.8- 144.6 79 29 19 13 10 9 1.1 6 2.0 32 9 319 148.0- 148.5 88 59 25 13 34 14 2.4 12 1.9 87 19 320 156.3- 156.8 92 31 19 14 12 10 1.2 5 2.0 34 9 321 173.0- 173.5 90 35 23 20 12 11 1.1 3 1.8 27 8 325 210.0- 210.5 92 34 25 18 9 9 1.0 7 1.8 29 8 326 220.5- 221.0 76 32 23 19 9 10 .9 4 1.8 23 7 327... 231.6- 232.0 85 33 23 17 10 9 1.1 6 1.8 29 8 333 289.8- 290.3 98 36 27 22 9 10 .9 5 1.7 24 7 335 315.3- 315.8 90 29 22 21 7 8 .9 1 1.7 14 4 See footnotes at end of table.PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A57 Table 6.—Atterberg limits and indices of samples from core holes—Continued Hydrologie Percent Volumetric Linear Laboratory Depth (feet) passing Liquid Plastic Shrinkage Plasticity Flow Toughness Shrinkage Shrinkage sample No. 40 sieve limit limit limit index index index index ratio shrinkage shrinkage Core hole 24/26-36A2—Continued 59CAI 338 338.0- 338.5 95 31 22 19 9 7 1.3 3 1.8 22 6 339 356.8- 357.3 89 30 24 21 6 8 .8 3 1.7 15 4 341 370.0- 370.5 80 35 26 17 9 8 1.1 9 1.8 32 9 343 389.1- 389.6 98 31 24 23 7 4 1.8 1 1.6 13 4 344 399.0- 399.5 82 36 26 22 10 12 .8 4 1.7 24 7 345 403.0- 403.5 90 33 24 21 9 9 1.0 3 1.7 20 6 348 433.3- 433.7 90 28 21 20 7 7 1.0 1 1.7 14 4 349 443.0- 443.5 90 33 23 21 10 9 1.1 2 1.7 20 6 352 474.7- 475.3 88 34 23 17 11 10 1.1 6 1.8 31 9 353 488.0- 488.5 93 31 24 20 7 14 .5 4 1.7 19 5 354 494.0- 494.5 88 32 24 19 8 10 .8 5 1.8 23 7 355 507.0- 507.5 94 38 24 18 14 12 1.2 6 1.8 36 10 356 516.3- 516.8 86 38 23 18 15 7 2.1 5 1.8 36 10 357 531.0- 531.5 89 33 22 22 11 13 .8 0 1.7 19 5 361 565.1- 565.6 92 30 25 22 5 9 .6 3 1.7 14 4 362 574. 6- 575.1 84 35 23 20 12 11 1.1 3 1.8 27 8 363 582.6- 583.1 91 41 27 20 14 11 1.3 7 1.8 38 10 364 595.1- 595.6 90 30 22 20 8 6 1.3 2 1.8 18 5 365 607.5- 608.0 99 32 23 22 9 9 1.0 1 1.7 17 5 366 613.8- 614.3 96 31 21 21 10 8 1.2 0 1.7 17 5 367 623.0- 623.5 97 55 36 17 19 9 2.1 19 1.8 68 16 368 631.2- 631.7 86 48 36 25 12 11 1.1 11 1.6 37 10 369 648.2- 648.7 94 52 31 16 21 11 1.9 15 1.9 68 16 370 658.8- 659.3 88 33 24 23 9 9 1.0 1 1.7 17 5 373 683.1- 683.5 92 57 36 21 21 18 1.2 15 1.7 61 15 376 719.4- 720.0 96 44 32 30 12 11 1.1 2 1.5 21 6 377 726.1- 726.6 90 24 20 20 4 8 .5 0 1.7 7 2 379 744.0- 744.5 99 46 34 27 12 7 1.7 7 1.6 30 8 380 756.9- 757.4 100 107 48 15 59 24 2.5 33 1.8 166 28 381 763.0- 763.5 92 89 55 19 34 28 1.2 36 1.7 119 23 382 775.6- 776.1 94 37 25 23 12 7 1.7 2 1.7 24 7 383 777.7- 778.2 88 45 33 30 12 7 1.7 3 1.5 22 6 384 791. 7- 792.2 96 90 43 16 47 32 1.5 27 1.8 133 25 385 843.3- 843.8 100 72 40 24 32 24 1.3 16 1.6 77 17 386 852.0- 852.5 100 51 35 28 16 26 .6 7 1.5 34 9 388 866.3- 866.8 100 49 30 21 19 10 1.9 9 1.7 48 13 389 916. 4- 916.9 100 74 41 24 33 18 1.8 17 1.6 80 18 390 1,036.3-1 036.8 100 84 44 18 40 20 2.0 26 1.7 112 22 393 1,116.8-1 117.3 93 62 39 18 23 9 2.6 21 1.7 75 17 394 1,155.4-1 155.9 93 73 46 31 27 13 2.1 15 1.5 63 15 396 1,240.5-1 241.0 100 92 61 44 31 12 2.6 17 1.2 58 15 397 1,363. 0-1 363.5 100 70 47 37 23 10 2.3 10 1.3 43 11 401 1,446.9-1 447.4 100 89 62 39 27 9 3.0 23 1.3 65 16 403 1,526. 6-1 527.1 100 84 57 28 27 8 3.4 29 1.5 84 18 404 1,688.0-1 688.5 100 93 58 20 35 28 1.3 38 1.7 124 24 410 1,826.5-1 827.0 100 81 50 9 31 15 2.1 41 2.0 144 26 411 1,892-2-1 892.7 100 81 51 5 30 14 2.1 46 2.1 160 27 Core hole 6S/2W-24C7 60CAL12 71.4- 71.9 100 30 20 15 10 11 0.9 5 1.9 28 8 13 90.4- 90.8 100 47 25 18 22 11 2.0 7 1.8 52 13 16 120.3- 120.8 100 47 27 19 20 11 1.8 8 1.8 50 13 18... 140.8- 141.4 96 42 22 12 20 8 2.5 10 2.0 60 15 20 160.0- 160.5 100 50 26 14 24 16 1.5 12 1.9 68 16 22 191.3- 191.8 97 38 18 8 20 12 1.7 10 2.2 66 16 24 222.3- 222.8 100 55 29 15 26 15 1.7 14 1.9 76 17 27 253.4- 253.8 98 26 21 18 5 5 1.0 3 1.8 14 4 28 307.0- 307.4 100 40 23 14 17 11 1.5 9 1.9 49 13 30 330.0- 330.5 100 42 24 16 18 14 1.3 8 1.8 47 12 31 344.3- 344.8 100 34 21 18 13 4 3.3 3 1.8 29 8 32 361.3- 361.8 95 38 25 19 13 9 1.4 6 1.8 34 9 33 408.4- 408.9 99 42 22 16 20 11 1.8 6 1.9 49 13 36 436.7- 437.2 96 34 21 18 13 14 .9 3 1.8 29 8 38 458.3- 458.8 100 32 21 18 11 11 1.0 3 1.8 25 7 40 522. 5- 522.9 95 33 20 16 13 8 1.6 4 1.8 31 9 43 563.2- 563.7 98 49 24 18 25 8 3.1 6 1.8 56 14 45 605.3- 605.8 96 40 18 16 22 14 1.6 2 1.9 46 12 46 633.8- 634.3 100 33 19 18 14 13 1.1 1 1.8 27 8 48 665. 5- 665.9 98 35 21 20 14 15 .9 1 1.7 26 7 49 715.5- 716.1 99 61 27 14 34 16 2.1 13 1.9 89 19 51 744.9- 745.4 100 68 30 14 38 15 2.5 16 1.9 103 21 52 756.4- 756.9 100 63 28 12 35 17 2.1 16 2.0 102 21 54... 789.5- 790.0 99 67 31 14 36 12 3.0 17 1.9 101 21 56 812.0- 812.5 100 48 24 13 24 16 1.5 11 2.0 70 16 59 842.2- 842.7 100 46 27 18 19 12 1.6 9 1.8 50 13 61 865.9- 866.4 100 58 30 14 28 16 1.8 16 2.0 88 19 64... 900.2- 900.7 100 60 28 14 32 14 2.3 14 2.0 92 19 66 923.0- 924.1 100 64 32 14 32 15 2.1 18 2.0 100 21 68 958.3- 958.8 10C 58 32 14 26 12 2.2 18 1.9 84 19 Core hole 7S/1E-16C6 72 232.5- 233.0 100 41 24 16 17 3 5.7 8 1.9 48 75... 301.0- 301.5 98 31 19 14 12 4 3.0 5 1.9 32 78 354.5- 355.0 99 24 21 18 3 2 1.5 3 1.8 11 80 430.1- 430.6 98 32 19 14 13 3 4.3 5 1.9 34 82.... 509.5- 510.0 91 33 19 14 14 6 2.3 5 2.0 38 84 554.3- 554.8 95 25 18 14 7 2 3.5 4 1.9 21 87 696.3- 696.8 95 33 20 16 13 3 4.3 4 1.9 32 91 790.6- 791.1 98 32 20 16 12 3 4.0 4 1.8 29 93 832.4- 832.9 99 29 22 18 7 2 3.5 4 1.8 20 96 937.4- 937.9 99 50 25 19 25 7 3.6 6 1.8 56 1 Insufficient sample. 2 Nondeterminable. 8 Nonplastic. 4 Negative value.A58 MECHANICS OF AQUIFER SYSTEMS Table 7.—Acid solubility and gypsum content of samples from core holes Table 7.—Acid solubility and gypsum content of samples from core holes—Continued Hydrologic Laboratory sample Sample depth (feet) Acid solubility (percent) Gypsum content (meg per 100 g soil) (Tons per acre-foot) Core hole 14/13-11D1 57CAL1 77.0- 77.5 5.6 2 110.5- 111.0 8.4 0 0 4 191.5- 192.0 6.4 0 0 6 277.1- 277.6 4.8 0 0 8 - 353.0- 353.5 5.6 0 0 9 398.0- 389.5 10.0 10 432.0- 432.5 10.8 0 0 11 471.5- 472.0 6.4 12 510.3- 510.8 10.4 6 0 14 594.0- 594.5 8.0 16 646.6- 647.1 6.8 6 0 18 662.1- 662.6 7.2 0 0 20 682.5- 683.0 3.6 0 0 21 697.0- 697.5 8.8 22 707.0- 707.5 .8 6 0 24 721.5- 722.0 4.0 0 0 26 743.0- 743.5 5.2 0 0 28. 764.9- 765.4 1.2 0 0 30 784.5- 785.0 3.2 0 0 31 791. 0- 791. 5 2.8 32 802.0- 802.5 4.8 6 6 34. 813.0- 821.0 2.0 0 0 36 831.5- 832.0 4.0 0 0 38 853.0- 853.5 2.0 0 0 40 867.0- 867.5 4.0 0 0 42 877.0- 877.5 4.0 0 0 43 887.5- 888.0 6.0 44 901.0- 901.5 4.4 0 0 46 917.2- 917.7 .8 0 0 48 936.5- 937.0 4.0 0 0 50 957.5- 958.0 1.6 0 0 52 984.0- 984.5 3.6 0 0 53 987. 6- 988.0 3.6 54 1,000. 5-1,001.0 2.0 0 0 56 1,020.8-1,021. 3 4.0 0 0 58 1,039. 5-1,040.0 7.2 9 0 60 1,063. 5-1, 064.0 5.2 0 0 62 1,075.0-1,075.5 4.4 0 0 64 1,092.0-1,092.5 3.6 0 0 66 - 1,113. 5-1,114.0 2.4 0 0 68 1,133.0-1,133.5 5.2 0 0 70 1,174.0-1,174,5 1.2 0 0 72 1,219.0-1,219.5 4.0 0 0 74 1,232.0-1,232.5 3.2 0 0 76 1,252 -i—1,252. 5 4.4 0 0 78 1,269. 5-1,270.0 6.4 0 0 80 1,284.0-1,284.5 2.8 0 0 81 1,293. 0-1,293.5 4. 0 82 1,300—L300.5 3.2 0 0 84 1,319.4-1,319.9 3.2 0 0 86 1,339.5-1,340.0 5.2 88 l,357.0-i; 357.5 4.4 0 0 90 1,373.4-1.373.9 7.6 0 0 92 1,397.0-1,397.5 14.8 0 0 94 1,415.0-1,415.5 6.0 0 0 96 1,432. 5-1,433.0 8.8 0 0 98 1,454. 5-1,455.0 6.8 0 0 100 1,474.0-1,474.5 5.2 0 0 102... 1,487.0-1,487.5 6.0 0 0 103 1,494.5-1,495.0 5.2 Core hole 16/15-34N1 58CAL2 298.2- 298.7 8.2 0 0 4 371.7- 372.1 5.2 0 0 5 418.5- 419.0 12.2 6 454.3- 554.8 8.8 0 0 8 507.4- 507.9 9.2 0 0 10 525.9- 526.3 13.6 0 0 12 552.8- 553.2 8.0 0 0 14 570.7- 571.2 8.8 16 591.7- 592.2 2.0 0 0 17. 601.7- 602.2 4.0 18 622.3- 622.8 4.0 0 0 20 643.2- 643.7 7.6 0 0 22 666.0- 666.5 9.2 0 0 24 683.7- 684 2 8.8 0 0 25 696.6- 697 1 11.6 26 701.8- 70: 4 9.6 0 0 28 721.3- 721 8 6.8 0 0 30 745.3- 745.9 9.2 0 0 32 762.4- 762.9 8.4 0 0 34 785.0- 785.5 3.2 0 0 35 795.0- 795. 5 11.0 36 806.1- 806.6 9.2 0 0 38 822.1- 822.6 9.2 0 0 40 837.7- 838.2 8.8 0 0 42 860.1- 860.6 5.6 0 0 44 876.6- 877.1 3.6 0 0 45 891. 6- 892.1 11. 6 46 901.2- 901.7 9.6 0 0 Hydrologic Sample depth Acid Gypsum content Laboratory sample (feet) solubility (percent) (meg per 100 g soU) (Tons per acre-foot) Core hole 16/15-34N1—Continued 58CAL48 922.6- 923.1 8.4 0 0 50 940.6- 941.1 9.6 0 0 52 963.7- 964.2 4.8 0 0 54 980.6- 981.1 6.4 0 0 56 1,012.2-1,012.7 1.8 0 0 58 1,042.8-1,043.3 6.0 0 0 59 1,154.0-1,154 5 1 2 60 1,181.2-1,181.7 9.6 0 0 62 1,202.5-1,203.0 7.0 0 0 64 1,238.1-1,238.6 6.0 0 0 66 1,254.9-1,255.4 6.0 0 0 67 1,280.2-1,280.7 3 4 68 i; 325.5-l| 326.0 6.8 0 0 70 1,351.4-1,351.9 4.8 0 0 72 1,371.5-1,372.0 5.2 0 0 73 1,391.7-1,392.2 3.0 74 I! 401.8-1,'402.3 2.8 0 0 76 1,421.0-1,422.0 4.8 0 0 78 1,458.9-1,459.4 1.6 0 0 80 1,482.7-1.483.2 6.8 0 0 82 1,506.7-1,507.2 1.4 0 0 84 1,526.0-1,526.5 4.0 0 0 86 1,558.1-1,558.6 3.2 0 0 88 1,589.3-1,589.8 5.4 0 0 90 1,676.5-1,677.1 6.0 0 0 91 1,714.1-1,714. 5 4.4 92 1,752.0-1,752.5 8.0 0 0 94 1,837.6-1,838.1 5.4 0 0 96 1,916.9-1,917.4 6.8 0 0 97 - 1,953.0-1,953.5 6.0 98 1,990.0-1,990.5 4.0 0 0 Core hole 19/17-22J1. 2 57CAL104 89.6- 90.0 160 - 172 5.6 0 0 105 - 16.0 106 233.8- 234.4 0 0 107 271.2- 271.7 310.0- 310.5 10.8 108 0 0 110 399.4- 399.9 4.0 0 0 112 476.0- 476.4 8.4 0 0 114 553.9- 554.4 0 0 115 593.3- 593.8 631.2- 631.7 5.6 116 0 0 117 676.0- 676.4 712.8- 713.2 5.6 118 0 0 120 732.0- 732. 5 0 0 122 767.1- 767.6 0 0 124 789.1- 789.6 0 0 125 799.6- 800.0 810.0- 810.5 8.8 126 0 0 128 860.7- 861. 2 0 0 130 870.0- 870.5 0 0 131 888.6- 889.1 905.3- 905.7 10.4 132 0 0 134 945.4- 945.9 0 0 136 958.0- 958.5 0 0 138 982.8- 983. 2 0 0 139 993.4- 993.9 1.003.1- 1,003.6 1.032.0- 1,032.5 1.093.8- 1,094.3 1,119.6-1,120.1 1.143.3- 1,143.8 1.159.8- 1,160.3 1,198.5-1,199.2 1.216.0- l, 216.5 1.247.4- 1,247.9 1,283.3-1,283.8 1.291.0- 1,291.5 1.305.0- 1,306.4 1.346.5- 1,347.0 1.376.2- 1,376.8 1.392.0- 1,392.5 1, 416.8-1,417.4 1, 432.7-1,433.2 1.480.0- 1,480. 5 1.498.2- 1,498. 7 1.526.5- 1, 526.9 1, 543.7-1, 544. 2 1, 574.0-l, 575.4 1, 590.2-1, 590.7 1, 605.0-1, 605. 5 1.642.0- 1, 642.5 1, 668. 5-1, 668.9 1, 698.5-1, 699.0 1.727.5- 1. 728.0 1.779.3- 1,779.8 1, 804.5-1,805.0 1.841.4- 1,842. 0 1.873.1- 1,873.6 6.8 140 0 0 142 0 0 144 8.0 0 0 146 0 0 148 0 0 150 0 0 152 6.4 0 0 154 0 0 156 0 0 158 0 0 159 8.0 160 0 0 162 0 0 164 0 0 165. . 9.2 166 0 6 168 0 0 170 0 0 172 11.2 0 0 174 0 0 176 0 0 178 0 0 179 7.2 180 0 0 182 0 0 184 0 0 186 4.8 0 0 188 0 0 190 12.0 0 0 192 7.4 12.7 194 0 0 196 2.3 4.0PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A59 Table 7.—Acid solubility and gypsum content of samples from core holes—Continued Table 7.—Acid solubility and gypsum content of samples from core holes—Continued Hydrologic Sample depth Acid Gypsum content Laboratory sample (feet) solubility (percent) (meg per 100 g soil) (Tons per acre-foot) Hydrologic Sample depth Acid Gypsum content Laboratory sample (feet) solubility (percent) (meg per 100 g soil) (Tons per acre-foot) Core hole 19/17-22J1.2—Continued Core hole 24/26-36A2—Continued 57CAL197 1.899.3- 1,899.8 1,912.5+ 1.956.3- 1,956. 7 1,993.0-1,993. 5 2, 049.3-2,049. 7 2,092.2-2,092.6 8.4 198 0 4.4 0 0 0 0 7.6 0 0 0 200 202 204 8.8 206 9.6 Core hole 23/2&-16N1 58CAL102 155.1- 155.6 1.7 0 0 106 287.2- 287.7 7.1 0 0 109 316.4- 316.9 8.8 0 0 110 320.3- 320.8 0 o 113 352.8- 353.3 7.6 0 0 116 418.0- 418.5 7.0 0 0 120 465.0- 465.5 4.7 0 0 123 496.0- 496.5 3.7 0 0 125 511.0- 511.5 7.6 0 0 128 545.5- 546.0 3.5 0 0 131 594.5- 595.0 2.9 0 0 133 616.0- 616.4 5.0 0 0 135 630.7- 631.2 6.2 0 0 137 654.1- 654.6 6.1 0 0 139 673.1- 673.6 7.0 0 0 141 694.0- 694.5 6.2 0 0 144 730.5- 731.0 11.1 0 0 Core hole 24/26-36A2 59CAL310 54.3- 54.8 1.7 0 0 311 63. 4- 63.9 2.0 312 84.6- 85.1 2.9 313 93.0- 93.5 2.8 314.... 102.6- 103.1 1.5 0 0 315 117.6- 118.1 2.4 316 124.2- 124.6 2.9 317 133.0- 133.5 3.2 318 143.8- 144.6 3.7 0 0 319 148.0- 148.5 6.0 320 156.3- 156.8 1.7 321 173.0- 173.5 4.4 322 176.3- 176.8 3.8 0 0 323 187.0- 187.5 2.4 324 203.5- 204.0 4.1 325 210.0- 210.5 5.2 326 220.5- 221.0 4.5 0 0 327 231. 6- 232.0 4.4 328 240.2- 240.7 1.8 329 251.5- 251.9 1.5 330 260.2- 260.7 7.3 0 0 331 263.5- 274.0 2.8 332.... 284.5- 284.9 7.1 333 289.8- 290.3 4.8 334.... 300.5- 301.0 7.8 0 0 335.... 313.3- 315.8 4.4 336 318.0- 318.5 8.8 337 328.5- 329.0 6.4 338.... 338.0- 338.5 7.6 0 0 339 356.8- 357.3 10.0 340.... 358.7- 359.2 10.2 341 370.0- 370.5 7.2 342 374.3- 374.8 4.9 0 0 343.... 389.1- 389.6 4.8 344 399.1- 399.5 12.8 345.... 403.0- 403.5 5.2 346.... 414.9- 415.4 7.0 0 0 347.... 423.0- 423.5 2.8 348.... 433.3- 433.7 9.0 349.... 443.0- 443.5 4.0 350 458.5- 459.0 3.4 0 0 351 467.3- 467.8 .8 352.... 474.7- 475.3 4.7 353 488.0- 488.5 4.4 354 494.0- 494.5 3.7 0 0 355 507.0- 507.5 6.0 356.... 516.3- 516.8 7.6 * 357 531.0- 531.5 3.6 358 533.1- 533.6 2.9 0 0 359 544.0- 544.5 3.2 360.... 552.6- 553.1 3. 5 361.... 565.1- 565.5 4.0 362 574.6- 575.1 5.1 0 0 363.... 582.6- 583.1 6.4 364 595.1- 595.6 2.9 365 607.5- 608.0 8.8 366... 613.8- 614.3 5.0 0 0 367 623.0- 623.5 9.2 59CAL368 631.2- 631.7 6.2 369 648.2- 648.7 6.8 370 658.8- 659.3 6.1 0 0 371 668.3- 668.8 4.0 372 678.5- 679.0 7.0 0 0 373 683.1- 683.5 8.0 374 697.5- 698.0 6.2 2.8 4.8 375 709.0- 709.5 4.8 376 719.4- 720.0 12.1 0 0 377... 726.1- 726.6 3.2 378 735.4- 735.9 11.1 0 6 379 744. (+ 744. 5 8.8 380 756.9- 757.4 6.4 382 775.6- 776.1 20.8 0 0 384 791.7- 792.2 7.9 386 — 852.0- 852.5 7.3 0 0 388 866.3- 866.8 11.4 389 916.4- 916.9 3.2 0 0 390 1, 036.3-1,036.8 7.8 0 0 392 1, 099.1-1, 099. 6 1.8 4.2 7.2 394 1,155.4-1,155.9 1.5 .2 .3 396 1, 240. 5-1, 241.0 3.4 0 0 398 1,369. 5-1,370.0 4.3 399 I! 421.2-1,421.7 1.0 4.7 8.1 400 1,431.0-1,431.5 1.2 402 1, 492.0-i; 492. 5 4.0 5.1 8.8 403 1, 526. 6-1, 527.1 0 0 404 i; 688.0-i; 688.5 2.0 0 0 405 1, 720.4-1, 720.9 8.1 14.2 24.4 406 1,751.7-1, 752.2 12.5 8.6 14.8 407 1,785.0-1,785.5 6.1 14.1 24.3 408 1,802. 5-1, 803. 0 7.5 9.3 16.0 410 1,826.5-1,827.0 5.6 10.3 17.7 411 1,892.2-1, 892. 7 12.0 20.6 412 1,911.5-1' 912.0 2.2 0 0 414 1,955. 5-1,956.0 .8 0 0 416 2,010. 0-2, 010. 5 .4 418 2,102.0-2; 102. 5 .4 0 0 419 2,174. 0-2,174. 5 1.0 Core hole 6S/2W-24C7 60CAL10 36.5- 37.0 10.1 0 0 12 71.4- 71.9 10.4 13 90.4- 90.8 7.2 0 0 16 120.3- 120.8 7.8 0 0 18 _ 140.8- 141.4 9.7 0 0 21 178. 0- 178.5 12.5 22 191.3- 191.8 10.0 0 0 24 222.3- 222.8 7.5 27 253.4- 253.8 10.5 0 0 28 307.0- 307.4 7.9 0 0 31 344.3- 344.8 13.0 0 0 32 361.3- 361.8 11.8 33 408.4- 408.9 12.4 0 0 36 436. 7- 437.2 11.4 38 458.3- 458.8 11.6 0 0 40 522.5- 522.9 12.1 0 0 41 545.0- 545.5 10.9 43 563.2- 563.7 9.0 45 605.3- 605.8 9.3 0 0 46 633. 8- 634.3 19.1 48 665.5- 665.9 7.5 0 0 49 715.5- 716.1 11.2 0 0 51 744.9- 745. 4 11.0 54 789. 5- 790.0 8.7 56 812.0- 812.5 8.9 0 0 59 842.2- 842.7 10.8 61 865.0- 866.4 11.9 0 0 64 900.2- 900.7 10.2 66 923.6- 924.1 6.5 0 0 68 958.3- 958.8 12.0 0 0 Core hole 7S/1E-16C6 70 196.3- 196.8 15.6 0 0 74 275.4- 275.8 11.4 0 0 78 354.5- 355.0 11.0 0 0 80 430.1- 430.6 12.7 0 0 84 554.3- 554.8 12.9 0 0 86 598. 8- 599.3 13.5 0 0 87 696.3- 696.8 17.7 0 0 90 750.1- 750.5 12.2 0 0 93 832. 4- 832.9 18.4 0 0 96 937. 4- 937.9 16.1 0 0Table 8.—Visual classification, Atterberg limits, and specific gravities of samples tested for consolidation IData from Earth Laboratory, U.S. Bureau of Reclamation, Denver, Colo.] Gradation (estimated) Atterberg limits Earth Laboratory sample Depth (feet) Maximum size (U.S. Standard sieve No.) Gravel >4.76 mm (percent) Sand, 4.7&-0.074 mm (percent) Silt and clay <0.074 mm (percent) Color (wet) Soil classification and description Unified Soil Classification symbol Liquid limit (percent) Plastic limit (percent) Plas- ticity index Specific gravity of solids Core hole 12/12-16H1 23L91 84.3- 84.6 30 0 10 90 Brown ... 92 159.4- 159.8 100 0 10 90 do_ 93 230.8- 231.2 50 0 10 90 Tan to brown. 94 324.5- 324.9 100 0 20 80 Gray 95 374.0- 374.5 200 0 0 100 do 96 425.0- 425.3 100 0 10 90 do 97 471.2- 471.5 100 0 5 95 do 98 516.5- 516.9 50 0 75 25 Gray to black- 579.0- 579.3 100 0 35 65 Tan 625.0- 625.4 200 0 0 100 Gray 675.9- 676.2 50 0 45 55 do 722.0- 722.3 100 0 5 95 do 103 - 773.0- 773.4 50 0 60 40 Brown to gray. 821.4- 821.8 50 0 55 45 Gray 877.4- 877.8 30 0 65 35 Brown 926.8- 927.2 50 0 20 80 Gray 972.0- 972.4 30 0 75 25 do 108 998.6- 999.0 50 0 40 60 Brown 315.0- 315.3 50 0 80 20 Brown 194 397.0- 397.3 100 0 10 90 do 554.0- 554.4 50 0 10 90 Tan-gray 642.0- 642.3 100 0 0 100 Gray 644.8- 645.2 50 0 10 90 do 699.0- 699.4 100 0 10 90 do 746.0- 746.4 50 0 45 55 do 832.3-832.7 0 60 40 Light gray 832.3- 832.7 50 0 20 80 Gray 983.6- 984.0 100 0 5 95 Brown.. 86 1, 076. O-l. 076. 4 50 0 60 40 do 87 — 1,249.0-1,249.4 16 0 8 15 do Clay, containing some fine sand; medium plasticity; slight dilatancy; medium dry strength; no reaction to HC1; trace of gypsum. Clay, containing some fine sand; medium to high plasticity; slow dilatancy; medium reaction to HC1. Clay, lean; low plasticity; slight dilatancy; low dry strength; slight reaction to HC1. Clay, containing fine sand; low plasticity; medium dilatancy; ome micaceous material present; no reaction to HC1. Clay, fat; high plasticity; no dilatancy; no reaction to HC1-------- Clay, fat, containing fine sand lenses; high plasticity; no dilatancy; no reaction to HC1; moist, and firm. Clay, fat; high plasticity; no dilatancy; lensed with fine sand._ Sand, fine, no plasticity; fast dilatancy; strong organic odor present; soft and loosely cemented. Clay, silty containing fine sand; medium plasticity; slight dilatancy. Clay, fat; high plasticity; no dilatancy; firm; numerous planes containing some silt. Clay, silty containing fine sand, medium plasticity, slow dilatancy; clay on outer surface; sand in center, angular. Clay, fat; high plasticity; no dilatancy, blocky structure; fractures contain silt. Sand, fine containing silt; no plasticity; fast dilatancy; lensed with clay and silt; medium cementation; no reaction to HC1. Sand, fine containing silt; no plasticity; fast dilatancy; organic odor present; no reaction to HC1. Sand, fine, uniform; no plasticity; fast dilatancy; free water present; no reaction to HC1. Clay, silty; medium plasticity; slow dilatancy; no reaction to HC1; top of sample contained sand of No. 30 size; rest of sample was silt and clay lensed. Sand, fine: no plasticity; fast dilatancy; slight binder____________ Clay containing fine sand; medium plasticity, slow dilatancy; sample lensed with clay and fine sand. CL 31 14 17 2.80 CL-CH 50 19 31 2.74 CL 33 11 22 2.73 CL 29 19 10 2.68 CH 54 23 31 2.73 CH 76 27 49 2.67 CH 58 20 38 2.68 SM (») 2.70 CL 32 14 18 2.69 CH 59 19 40 2.79 CL 45 14 31 2.72 CH 70 20 50 2.69 SM 0) 2.77 SM 0) 2.74 SM (!) 2.71 CL 47 32 15 2.72 SM (i) 2.70 CL 37 20 17 2.68 Core hole 14/13-1 ID 1 Sand, fine, angular, poorly graded, loosely cemented, wet________ Clay, silty; medium plasticity; slight dilatancy; medium reaction to HC1. Clay containing some fine sand; medium to high plasticity; slow to no dilatancy; structure slightly blocky. Clay; high plasticity; no dilatancy; no reaction to HC1 (sample not tested because of fractured condition). Clay containing some fine sand; medium plasticity; slow dilatancy; some slickensides; sample was not suitable for testing because of many fractures and poor condition. Clay, lean; medium plasticity; no to slow dilatancy, low dry strength. Clay containing very fine sand and silt; medium to high plasticity; no to slow dilatancy. Sand, fine, angular, containing clay; slight plasticity; slight dilatancy; micaceous material present; breaks down on wetting and working; not tested because of wax and poor condition of top half. Clay containing some fine sand; medium plasticity; medium dilatancy; slight micaceous material; no reaction to HC1. Clay containing some fine sand; medium to high plasticity; no to slow dilatancy. Sand, silty; slight plasticity; fast dilatancy; micaceous; slight cementation. Sand, coarse to fine; skip graded; wet; micaceous; not suitable for testing because of drilling mud penetration. SP CL CL CH CL CL CL SC CL CL SM SP A60 MECHANICS OF AQUIFER SYSTEMS88 1,350. 5-1,350.8 1G 0 85 15 do Sand, coarse to fine; uniform graded; angular to rounded; free H20. Clay, lean; medium plasticity; slow dilatancy; blocky structure; granular feeling and appearance which breaks down on wetting; very hard and brittle. SP 89 1,395.0-1,395.3 100 0 0 100 do CL 90 1,450. 0-1,450.3 50 0 45 55 do Clay containing fine sand, medium plasticity slight dilatancy, sample blocky and fractured. CL Core hole 16/15-34N1 23L197 299.1- 299.5 418.1- 418.5 538.9- 539.2 563.3- 563.7 571.2- 571.6 636.9- 637.3 713.1- 713.4 859.7- 860.1 901.7- 902.1 972.0- 972.4 198 200 235 201 202 204 206 207 208 210 1.153.6- 1,154.0 1.237.7- 1,238.1 1,332.4-1,332.8 1.391.3- 1,391.7 1.511.3- 1,511.7 1.631.7- 1,632.1 1.792.3- 1,792.7 1.871.8- 1,872.2 1,952.6-1,953.0 212 214 215 217 219 221 222 223 100 100 100 0 0 0 0 0 0 100 100 100 Tan. Clay, silty; medium to high plasticity; no dilatancy; moist CH CL CH CH 52 44 56 21 18 21 31 26 35 2.7 2. 71 2.73 2.77 200 0 0 100 CH 83 29 54 2.74 200 0 0 100 CH 80 25 55 2.75 100 0 0 100 Tan CH 61 24 37 2.74 30 0 60 40 Gray Sand containing silt and clay; low plasticity; medium dilatancy. SC 31 18 13 2.68 100 0 0 100 Brown... ... Clay containing silt; high plasticity; no dilatancy; sample CH 72 24 48 2.75 fractured. 50 0 5 100 do CH 69 22 47 2. 74 50 0 20 80 Gray . . Clay, silty, containing fine sand; medium plasticity; no di- CL 36 19 17 2.71 latancy. 200 0 0 100 CII 67 27 40 2.76 30 0 75 25 do SM 0) (i) 2.71 30 0 50 50 do Sand, fine, containing clay and silt; low plasticity; fast di- SM 32 22 10 2.70 latancy. 50 0 20 80 CH 95 24 71 2.69 100 0 0 100 CH 58 23 35 2.71 30 0 15 85 CH 55 22 33 2.71 100 0 0 100 Gray CH 77 26 51 2.72 200 0 0 100 do . . ..do CH 107 48 59 2.55 Core hole 19/17-22J1, 2 23L181 311.5- 311.9 100 0 5 95 Brown Clay, silty; low to medium plasticity; slight to slow dilatancy; no reaction to HC1; soft, wet natural condition. 182 554.4- 554.8 50 0 10 90 do Clay, silty; somewhat more silt than 23L181; low to medium plasticity; medium to fast dilatancy; high reaction to HC1; low cementation in sample; higher moisture at outside edge of sample possibly due to drilling fluid. 183 734.6- 734.9 100 0 5 95 Dark gray Clay, silty; low to medium plasticity; slight dilatancy; no reaction to HC1; firm blocky structure; slight amount of mica and organic material present. 184 904.9- 905.3 100 0 10 90 Tan Clay containing some silt; medium plasticity; medium dilatancy moist; slight reaction to IIC1; sample has slickensides present. 185 1,093.4-1,093.8 50 0 20 80 Brown Silt containing trace of fine sand; low plasticity; medium to fast dilatancy; slight reaction to HC1. 186 1,251.0-1,251.4 50 0 15 85 Tan Silt, somewhat clayey; medium plasticity; medium dilatancy; slight reaction to HC1. 187 1,345.2-1,345.6 8 0 40 60 do Silt containing fine sand; low plasticity; medium to fast dilatancy; slightly micaceous; breaks down on wetting and working; high reaction to HC1. 188 1,524.3-1,524. 7 30 0 60 40 Brown Sand, silty, fine to medium; low plasticity; medium to fast dilatancy; not suitable for testing because drilling mud and wax penetrated sample. 189 1, 601.2-1, 601.5 50 0 60 40 do Sand, silty, fine, nonplastic; fast dilatancy; micaceous and firm; slight reaction to HC1. 190 1,749.6-1,750.0 100 0 0 100 do Clay, silty; medium plasticity; medium dilatancy; slight reaction to HC1. 191 1,955.9-1,956.3 100 0 10 90 Gray . Clay, lean, dense; medium plasticity; slow dilatancy; no reaction to HC1. 192 2,021. 0 100 0 10 90 do Clay, lean, dense; medium plasticity; slow to no dilatancy; lensed with fine sand; no reaction to HC1. 193 2,092.9 + 100 0 10 90 do Clay, lean, very dense; medium plasticity; medium to fast dilatancy; mottled carbonate concressions; micaceous; breaks down on working; brittle and hard. See footnotes at end of table. CL CL CL CL ML ML ML SM SM CL CL CL CL PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A61Table 8.—Visual classification, Atterberg limits, and specific gravities of samples tested for consolidation—Continued Gradation (estimated) Atterberg limits Earth Laboratory sample Depth (feet) Maximum size (U.S. Standard sieve No.) Gravel >4.76 mm (percent) Sand, 4.76-0.074 mm (percent) Silt and clay <0.074 mm (percent) Color (wet) Soil classification and description Unified Soil Classification symbol Liquid limit (percent) Plastic limit (percent) Plas- ticity index Specific gravity of solids Core hole 23/25-16N1 23L226 261.7 - 261.9 16 0 55 45 Brown Sand containing clay, medium to fine; medium plasticity; no dilatancy; sample not homogeneous, well cemented. SC 23 17 6 2.73 227 283.5 - 283.9 50 0 10 90 Gray. Clay containing some fine sand; medium to high plasticity; no dilatancy. CL-CH 51 27 24 2.79 228 292.0 - 292.4 50 0 20 80 Gray-brown. - Clay containing fine sand; medium plasticity; no dilatancy CL 44 28' 16 2. 75 229 450.1 - 450. 5 100 0 5 95 Brown Clay, silty; medium plasticity; no dilatancy CL 42 22 20 2. 80 232 630.3 - 630.7 4 0 55 45 do Sand, silty (some clay); low plasticity; medium to fast dilatancy. SM 26 w (■) 2. 73 234 723.5 - 723.8 50 0 40 60 do Silt sandy (some clay); low plasticity; medium to fast dilatancy. ML 36 30 6 2.74 Core hole 24/26-36A2 23L23G. 237. 238. 239. 240. 241. 242. 243. 244. 245. 246. 247. 248. 249. 250. 251. 252. 253. 254. 123.1 - 123.4 8 0 15 85 Brown Clay, silty, containing medium to fine sand; low dilatancy; CL 29 17 12 2.71 medium plasticity. 157 1 - 157 4 8 0 80 20 SC 30 16 14 2.71 315.0 - 315.3 8 0 60 40 -.do Sand, medium to fine, containing some clay, very firm, brittle, SC well cemented; not tested because of fractures and drilling mud. 443.0- 443.2 8 0 70 30 Tan... Sand containing clay, medium to fine; low plasticity; no sc 30 18 12 2. 76 dilatancy; micaceous. 516.0- 516.3 50 0 20 80 Brown Clay, silty, containing fine sand; no dilatancy; medium plas- CL 43 23 20 2. 75 ticity; moist, firm, micaceous. 607.2- 607.5 4 0 20 80 Tan Silt containing fine sand; slow dilatancy; slight plasticity; some ML 33 23 10 2. 73 sand in concretions. 725.6- 725.9 50 0 15 85 Gray Clay, silty; some fine sand; medium plasticity; no dilatancy; CL 49 27 22 2. 73 micaceous. 843. 0- 843. 3 200 0 0 100 CH 99 36 63 2.71 916.1- 916. 4 100 o 5 95 CH 70 21 49 2.69 CH 1,115.7-1,116.1 50 0 20 80 Gray Clay, fat; fine-to medium-sand pockets; high plasticity; no dila- CH 67 25 42 2. 70 tancy; firm; micaceous. 1,155.1-1,155.4 100 0 5 95 do -. Clay, fat; high plasticity; no dilatancy; small amount of sand CH 70 33 37 2.68 in pockets; micaceous. 1,241.0-1,241.3 100 0 5 95 do Clay, fat; lensed with silt; high plasticity; no dilatancy; firm-. CH-MH 94 41 53 2.66 1,362. 7-1,363. 0 100 0 5 95 do Clay, fat; high plasticity; no dilatancy; contains some silt CH-MH 73 35 38 2.66 lenses. 1,447. 4-1,447.8 50 0 10 90 do Clay, fat; high plasticity; no dilatancy; lensed with silt and CH-MH 80 39 41 2.62 fine sand. 1,526. 2-1, 526. 6 100 0 10 90 do Clay, fat; high plasticity; no dilatancy; firm; silt pockets in CH 78 34 44 2. 63 sample lensed with some fine sand and silt; micaceous. 1,687. 0-1,687. 3 200 0 0 100 do . Clay, fat; high plasticity; no dilatancy; firm; moist (claystone). CH 75 34 41 2.71 1,826.2-1,826.5 200 0 0 100 do CH 85 36 49 2.77 1,892.7-1,893.1 200 0 o 100 CH slickensides throughout sample. Core hole 6S/2W-24C7 23L255 140.5- 140.8 100 0 0 100 Gray Clay, fat; no dilatancy; high plasticity; firm; moist; medium dry strength; slight reaction to HC1. CH 52 18 34 2.73 256 191.0- 191.3 16 0 5 95 do Clay, lean; no dilatancy; medium plasticity; some sand; high reaction to HC1. CL 35 15 20 2.71 257 307.5- 307.8 200 0 0 100 Brown Clay, lean; no dilatancy; medium plasticity; medium dry strength; high reaction to HC1. CL 40 19 21 2.72 258 253.1- 253.4 100 0 20 80 Gray Clay, silty, containing fine sand; medium dry strength; no dilatancy; medium plasticity; sheet micaceous material present; high reaction to HC1. CL 31 18 13 2.64 259 260 344.0- 344.3 458.0- 458.3 50 0 20 80 do Clay, silty, containing fine sand; medium dry strength; no dilatancy; medium plasticity; medium reaction to HC1. CL 37 17 20 2.72 261 436.4- 436.7 100 0 10 90 Gray... . Clay, silty, some fine sand; no dilatancy; medium plasticity; high reaction ti HC1; alternate for 23L260. CL 40 20 20 2.72 A62 MECHANICS OF AQUIFER SYSTEMS262 522.0- 522.4 200 0 0 100 Brown Clay, silty; medium dry strength; slow dilatancy; medium plasticity; white concretions and streaks; high reaction to HC1. Clay containing silt; medium plasticity; no dilatancy; firm; moist; white streaks; high reaction to HC1. CL 36 16 20 2.71 263 605.0- 605.3 100 0 5 95 Gray CL 45 18 27 2.73 265 715.1- 715.5 100 0 0 100 do Clay, fat; no dilatancy; high plasticity; high dry strength; firm; moist, white concretions; moderate reactions to HC1. CH 56 18 38 2.74 267 865.0- 865.3 200 0 0 100 Dark gray Clay, fat; no dilatancy; high plasticity; high dry strength; firm; moist; streaked with white layers; high reaction to HC1. Clay, fat; no dilatancy; high plasticity; high dry strength; streaked with carbonaceous modules; high reaction to HC1. CH 57 21 36 2.76 269 958.0- 958.3 100 0 Tr 100 Gray CH 59 22 37 2.76 Core hole 7S/1E-16C6 23L271 233.0- 233.6 100 0 0 100 Brown Clay containing silt; no dilatancy; medium plasticity; medium dry strength; no reaction to HC1. CL 42 20 22 2.75 272 300.6- 301.0 100 0 0 100 do Silt with clay binder; slight dilatancy; medium plasticity; medium dry strength; no reaction to HC1. ML-CL 37 15 22 2.68 273 353.4- 353.9 3/8 0 40 60 Gray Sand, medium to coarse, containing clay; not homogeneous; well cemented. SC 35 16 19 2.68 275 429.8- 430.1 16 0 10 90 Brown Clay, lean, containing some fine sand; medium dry strength; medium plasticity; no dilatancy; no reaction to HC1. CL 40 17 23 2.78 277 509.2- 509.5 200 0 0 100 do Clay, silty; no dilatancy; medium plasticity; medium dry strength; carbonaceous concretions which react highly to HC1. CL 42 17 25 2.76 279 554.0- 554.3 200 0 0 100 do Clay, lean; no dilatancy; medium plasticity; medium dry strength; carbonaceous concretions which react highly to HC1. CL 31 20 11 2.72 280 696.0- 696.3 200 0 0 100 do Clay, silty; slight dilatancy; medium plasticity; firm; moist; moderate reaction to HC1. CL 37 18 19 2.75 282 790.2- 790.6 8 0 30 70 do Clay, silty, mixed with fine sand and some coarse sand; slight dilatancy; medium plasticity; moderate reaction to HC1. CL-SM 28 17 11 2.74 283 832.0- 832.4 200 0 0 100 do Clay, silty; no dilatancy; medium plasticity; moderate reaction to HC1. CL 32 19 13 2.75 284 936.5- 936.9 50 0 10 90 do Clay, silty, containing some fine sand; medium plasticity; no dilatancy; slight reaction to HC1. CL 48 17 31 2.72 1 Nonplastic. 2 Top half of sample. * Bottom half of sample. PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A63A64 MECHANICS OF AQUIFER SYSTEMS Table 9.—Consolidation test summaries [Data from Earth Laboratory, U.S. Bureau of Reclamation, Denver, Colo.] Compression index, Ce Time-consolidation data Earth laboratory sample Depth (feet) From consoli- From Atter- Load range Coefficient of consolidation, Cv Coefficient of permeability Unified soil classification symbol dation curve berg test (psi) Sq in. per sec Sq ft per yr Calculated (ft per yr) From test (ft per yr) Core hole 12/12-16H1 23L91 _ 84.3- 84.6 0.12 0.19 100- 200 3.3X10-4 72.5 8.5X10-3 CL 200- 400 1.5X10-4 31.8 2.0X10-5 92. . 159.4- 159.8 i .22 .36 100- 200 9.2X10"5 20.1 2.8X10-5 CL-CH 200- 400 5.1X10-5 11.2 1.3X10-5 93 230.8- 231.2 .21 .21 200- 400 1.7X10-4 37.2 4.0X10-5 CL 94 . 324.5- 324.9 .11 .17 CL 95 374.0- 374.5 .32 .39 200- 400 1.5X10-5 3.3 2.9X10-4 CH 400- 800 1.0X10-5 2.2 1.5X10-4 96. 425.0- 425.3 1.13 .59 200- 400 4.2X10-6 0.92 3.2X10-4 CH 400- 800 3.2X10-6 .70 1.2X10-4 97 471.2- 471.5 .90 .43 200- 400 1.3X10-4 28.5 8.0X10-5 CH 400- 800 1.3X10-4 28.5 3.6X10-5 98 . 516.5- 516.9 .41 5.7 SM 99. 579.0- 579.3 .23 .20 200- 400 5. 6X10-4 122.0 7.2X10-5 CL 400- 800 3.8X10-4 83.2 4.4X10-3 800-1, 600 2. 5X10-4 54.8 1.5X10-3 2.6X10-4 100- 625.0- 625.4 .34 .44 400- '800 1.7X10-5 3.7 CH 800-1, 600 8.0X10-6 1.8 6.0X10-5 101. 675.9- 676.2 .27 .32 400- 800 1. lXlO-3 232.1 1.2X10-2 CL 800-1,600 400- 800 6.9X10-4 151.1 4.8X10-» 102 722.0- 722.3 .34 .54 2.7X10-5 5.9 3.3X10-4 CH 800-1,600 800-1,600 6.0X10-6 1.3 5.0X10-5 3. 5X10-4 103 773.0- 773.4 i .33 4.3X10-5 9.4 SM 104 821.4- 821.8 i .20 14.2 SM 105 877. 4- 877.8 i .18 33.9 SM 106 926.8- 927.2 .68 .34 400- 800 1.6X10-4 35.0 3.7X10-3 1.2X10-3 CL 800-1,600 8.5X10-5 18.6 107 972.0- 972.4 .33 38.4 SM 108 998.6- 999.0 i .30 .24 1.4 CL Core hole 14/13-1 ID 1 23L80 315.0- 315.3 (*) 25.3 SP 194. 397.0- 397.3 0.36 200- 400 1.8X10-4 39.4 4.0X10-3 CL 400- 800 5.1X10-5 11.2 8.1X10-4 800-1, 600 1.2X10-5 2.6 9.0X10-5 81 554.0- 554. 4 .22 200- 400 6.8X10-5 15.0 9.5X10-4 CL 400- 800 2.2X10-5 4.9 2.2X10-4 800-1, 600 4.1X10-5 9.0 1.8X10-4 83. 699.0- 699.4 .97 400- 800 5.8X10-5 12.8 2.1X10-3 CL 800-1,600 3.2X10-5 7.1 5.0X10-4 84 746.0- 746. 4 .30 200- 400 1.7X10-4 37.4 2.6X10-3 400- 800 1.2X10-4 26.9 1.5X10-3 800-1, 600 6.6X10-5 14.5 5. 5X10-4 196 832.2- 832.7 .36 200- 400 2.0X10-4 43.8 3.6X10-3 CL 400- 800 6.7X10-5 14.7 9.4X10-4 800-1,600 4.5X10-5 9.9 3.7X10-4 85... 983. 6- 984. 0 i 0.35 200- 400 1.2X10-5 2.6 2.1X10-4 CL 400- 800 1.0X10-5 2.2 1.1X10-4 800-1,600 1.2X10-5 2.6 1.2X10-4 86 1,076.0-1,076.4 (3) 1.7 SM 88. 1,350. 5-1,350.8 (3) 19.3 SP 89 l' 395.0-1' 395.3 « 200- 400 1.0X10-4 21.8 1.2X10-3 CL 400- 800 1.7X10-5 3.6 1. 5X10-4 800-1,600 1.1X10-5 2.4 8.0X10-5 90 1,450.0-1,450.3 i.29 800-1,600 3.9X10-5 8.4 2.4X10-4 CL Core hole 16/15-34N1 23L197 299.1- 299.5 0.34 0.38 198 418.1- 418.5 .32 .31 200 - - - 538.9- 539.2 1.30 .42 201 571.2- 571.6 (»<) .65 202 636.9- 637.3 .70 .63 204 713.1- 713.4 .31 .46 206 859.7- 860.1 (?) .19 207 901.7- 902.1 .29 .55 208 972.0- 972.4 .42 .53 210 1,163.6-1,154.0 1.21 .23 212 1,237.7-1,238.1 200- 400 3.4X10-4 74.9 1.1X10-2 CH 100- 200 1.7X10-3 361.4 6.3X10-2 CL 200- 400 5.0X10-4 109. 5 1.3X10-2 400- 800 1.4X10-4 30.7 2.1X10-3 200- 400 3.4X10-4 74. 5 6.3X10-3 CH 400- 800 1.3X10-4 28.5 2.1X10-3 CII 400- 800 1.8X10-5 3.9 4. oxio-4 CII 800-1,600 200- 400 8.1X10-8 1.8 1.3X10-4 3.3X10-4 72.3 3.6X10-3 CH 400- 800 7.0X10-5 15.3 8.9X10-4 800-1,600 800-1,600 100- 200 5.0X10-5 11.0 4.1X10-4 5. 6X10-4 122.6 4.6X10-3 SC 1.4X10-4 30.7 3.0X10-3 CH 200- 400 3.1X10-5 6.6 4.9X10-4 400- 800 1. 6X10-5 3. 5 2.0X10-4 800-1,600 200- 400 7. 5X10-6 1. 6 6.1X10-5 2.3X10-4 50.4 3.1X10-3 CII 400- 800 2.2X10-5 4.8 3. 6X10-4 800-1, 600 6. 5X10-6 6.2X10-4 3.2X10-4 1.4 7.0X10-5 400- 800 135.8 5.1X10-3 2.2X10-3 CL 800-1,600 70.6 400- '800 3.7X10-5 8.1 2.7X10-4 CH See footnotes at end of table.PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A65 Table 9.—Consolidation test summaries—Continued Compression index, Ce Time-consolidation data Earth laboratory sample Depth (feet) From consoli- From Atter- Load range Coefficient of consolidation, Cv Coefficient of permeability Unified soil classification symbol dation curve berg test (psi) Sq in. per sec Sq ft per yr Calculated (ft per yr) From test (ft per yr) Core hole 16/15-34N1—Continued 800-1,600 1.0X10-5 2.2 8.3X10-5 23L214 1,332.4-1,332.8 1.391.3- 1,391,7 1.511.3- 1,511.7 1, 631. 7-1, 632.1 1.792.3- 1,792.7 1,871.8-1,872.2 1,952.6-1,953.0 563.3- 563.7 (?) « > .21 350 SM 215 0.20 .099 SM 217 .77 800-1,600 4.7X10-5 10.3 3.3X10-4 CH 219. .44 800-1,600 3.0X10-4 65.7 2.0X10-3 CH 221 m (*) ‘.12 .41 800-1,600 1.3X10-4 28.5 7.4X10-4 CH 222 . .60 800-1,600 800-1,600 200- 400 7.6X10-5 16.6 5. 5X10-4 CH 223 .87 3.3X10-4 72.3 1.0X10-3 CH 235 .47 1.0X10-* 21.9 2.0X10-3 CH 400- 800 2.6X10-5 5.7 4.3X10-4 800-1,600 6.0X10“8 1.3 6.1X10-5 Core hole 19/17-22J1, 2 23L181 311.5- 311.9 0.35 50- 100 1.4X10-4 30.9 7.2X10-3 CL 100- 200 7.1X10-5 15.6 2.6X10-3 200- 400 5.3X10-5 11.5 1.3XltH 400- 800 1.7X10-5 3.6 2.8X10-4 182 554.4- 554.8 .36 800-1,600 5.1X10-4 111.7 4.7X10-3 CL 183 734.6- 734.9 .49 400- 800 2.4X10-4 52.6 4.4X10-3 CL 800-1,600 1.0X10-4 21.9 1.1X10-3 184 904.9- 905.3 .47 200- 400 1.2X10-4 26.3 2.0X10-3 CL 400- 800 3.4X10-5 7.4 4.8X10-4 800-1,600 1.2X10-5 2.6 1.3X10-4 185 1,093.4-1,093.8 .36 800-1,600 2.8X10-4 61.3 2.6X10-3 ML 186 i; 251.0-i; 251.4 .28 400- 800 5.3X10-5 11.6 5.9X10-4 ML 800-1,600 2.0X10-5 4.4 1.5X10-4 187 1,345.2-1,345.6 .28 800-1,600 1.2X10-4 26.3 8.9X10-4 ML 189 l' 601. 2-1, 601. 5 (3) (3) SM 190 1,749.6-1 i 750.0 (3) (3) 800-1,600 1.3X10-4 28.5 6.9X10-4 CL 191 li955.9-1,956.3 (3) (») 800-1,600 1.6X10-4 35.0 8.3X10-4 CL 192 2|021.0(—) » .24 800-1,600 4.7X10*5 10.4 2.9X10-4 CL 193 2,092.9(F) 1.09 CL Core hole 23/25-16N1 23L226. 227. 228 229. 232. 234. 261.7- 261.9 0.17 0.12 200- 400 1.4X10-3 311.0 2.4X10-2 400- 800 7.4X10-4 162.1 6.5X10-3 283.5- 283.9 .62 .37 200- 400 4.5X10-5 9.9 9.0X10-4 400- 800 1.9X10“‘ 4.2 4.8X10-4 292.0- 292.4 .53 .30 200- 400 8.8X10-4 192.7 3.2X10-2 400- 800 4.7X10-4 102.9 1.1X10-2 450.1- 450.5 .40 .29 300- 600 2.2X10-5 4.8 5.8X10-4 600-1,200 1.3X10-5 2.9 1.6X10-4 630.3- 630.7 .25 (2) 0.25 723.5- 723.8 .35 .24 .05 SM CL-CH CL CL SM ML Core hole 24/26-36A2 23L236.. 123.1- 123.4 .17 237.. 157.1- 157.4 .18 239 443.0- 443.2 .18 240 516.0- 516.3 .29 241 . - 607.2- 607.5 .21 242 725.6- 725.9 .35 243 843.0- 843.3 0.76 .80 244 916.1- 916.4 .63 .54 246 1,115.7-1,116.1 1.18 .51 247 1,155.1-1,155. 4 0.86 0.54 248 1,241.0-1,241.3 1.53 .76 249 1,362.3-1,362.7 .97 .57 250 1, 447.4-1, 447.8 1.24 .63 251... . ..... 1.526.2- 1, 526.6 1, 687.0-1,687.3 1.826.2- 1,826. 5 .61 252 . .59 253 .68 0.15 CL 400- 800 2.6X10-4 55.9 3.5X10-3 sc 400- 800 5.5X10-4 120.7 7.7X10-3 sc 400- 800 1.1X10-4 24.5 1.6X10-3 CL 800-1,600 5.5X10-4 120.7 4. 2X10-3 ML 800-1,600 3.3X10-4 71.2 3.5X10-3 CL 800-1,600 3.0X10-5 6.6 4.8X10-4 CH 800-1,600 2.2X10-5 4.8 2.9X10-4 CH 800-1,600 2.9X10-5 6.4 6.1X10-4 CH 800-1, 600 5.7X10-5 12.5 9. 6X10-4 CH 800-1, 600 3.3X19-5 7.2 7.9X10-4 CH-MH 800-1,600 2.6X10-5 5.6 4.1X10-4 CH-MH 800-1,600 2.1X10-5 4.5 4.1X10-4 CH-MH 800-1,600 6.7X19-5 1.5 8. 4X10-5 CH 800-1, 600 8.3X19-5 18.1 6.1X10-5 CH 400- 800 7.0X10-5 15.4 4.3X10-4 CH 800-1, 600 1.1X10-6 2.5 i.oxio-4 CH See footnotes at end of table.A66 MECHANICS OF AQUIFEB SYSTEMS Table 9.—Consolidation lest summaries—Continued Laboratory sample number Depth (teet) Compression index, Ce Time-consolidation data From consoli- dation curve From Atter- berg test Load range (psi) Coefficient of consolidation, C* * Coefficient of permeability Sq in. per sec Sq ft per yr Calculated (ft per yr) From test (ft per yr) Unified Soil Classification symbol Core hole 6S/2W-24C7 23L255 140.5- 140.8 0.29 0.38 25- 50 6.0X10-5 13.14 6.4X10-* 50- 100 4.0X10-5 8.76 3. 5X10-« 100- 200 2. 5X10-6 5. 48 1.2X10-* 200- 400 2.0X10-5 4.38 5.4X10"4 400- 800 1.3X10-5 2.85 1.9X10"4 256 191.0- 191.3 .21 .22 100- 200 5.8X10"4 129.21 1.8X10-2 200- 400 3.5X10-4 76.65 6.7X10-* 400- 800 2.9X10'4 63.51 3.4X10-* 257 307.5- 307.8 .24 .27 50- 100 1.6X10-4 35.04 7.5X10-5 100- 200 1.0X10-4 21.90 3.0X10-« 200- 400 6.6X10-5 14. 45 1.4X10-* 400- 800 5.7X10-5 12.48 6.5X10"4 258 253.1- 253.4 .30 .19 200- 400 3.0X10-5 662. 48 8.0X10-2 400- 800 2.1X10-* 455.52 2.9X10-2 259 344.0- 344.3 .24 .25 200- 400 3.5X10-4 76.65 7.6X10-5 400- 800 2.4X10"4 52.56 3.1X10-* 261 436.4- 436.7 .26 .27 100- 200 2. 4X1C-5 525.60 7.2X10-2 200- 400 1.2X10-» 262.80 2.2X10-2 400- 800 9.0X10"4 197.10 1.3X10-2 262 522.0- 522.4 .20 .24 200- 400 2.8X10"4 61.32 4.6X10-* 400- 800 1.3X10-4 28. 47 1.3X10-* 800-1.600 8.1X10-5 17.74 4.3X10"4 263 605.0- 605.3 .28 .31 100- 200 1.2X10-4 26.28 2.8X10-* 200- 400 5.4X10-5 11.83 9.7X10"4 400- 800 3.2X10-5 7.01 4.0 XIO-4 800-1,600 1.6X10-5 3.50 1.2X10"4 265 715.1- 715.5 .32 .42 200- 400 8.6X10-5 18.8 1.5X10-5 400- 800 2.9X19-6 6.4 4.4X10-4 800-1,600 1.3X10-5 2.8 1.0X10-4 267 . 865.0- 865.3 .33 .43 400- 800 3. 5X10-5 7.58 4.7X10"4 800-1,600 2.5X10-6 5. 54 2.2X10-4 269 958.0- 958.3 1 .28 .44 400- 800 1.1 xio-4 24.09 1.1X10-* 800-1,600 2.6X10-5 5.69 2.0X10-4 CH CL CL CL CL CL CL CL CH CH CH Core hole 7S/1E-16C6 23L271 233.0- 233.6 0.26 0.29 272 300.6- 301.0 .21 .24 273 353.4- 353.9 .16 .22 275 429.8- 430.1 .30 .27 277 509.2- 509.5 .19 .29 279 554.0- 554.3 .20 .19 280 696.0- 696.3 .22 .24 282 790.2- 790.6 .15 .16 283 832.0- 832.4 .23 .19 284 936.5- 936.9 .13 .35 200- 400 2.8X10"4 61.32 6.8X10-3 CL 400- 800 1.4X10"4 30.66 1.8X10-3 25- 50 9.0X10-5 19.71 8.7X10-» ML-CL 50- 100 7.5X10-5 16.43 3.7X10-* 100- 200 7.1X10-5 15.55 2.3X10-* 200- 400 4.6X10-5 10.07 9.1 XIO-4 400- 800 4.0X10-6 8.76 4.8 XIO-4 200- 400 3. 4X10-5 744.6 5.7X10-2 SC 400- 800 2.1X10-* 459.9 1.8X10-2 25- 50 2.4X10-5 5.26 2.3X10-5 CL 50- 100 3.1X10-5 6.79 1.9X10-» 100- 200 2.9X10-5 6.35 1.1X10-* 200- 400 2.3X10-5 5.04 4.5 XIO"4 400- 800 2.6X10-5 5.69 2.2X10"4 50- 100 1.1 XIO"4 24.09 5.4XUH CL 100- 200 5.9X10-5 12.92 1.5X10-* 200- 400 7.8X10-5 17.08 1.3X10-* 400- 800 3.7X10-5 8.10 3.1 XIO-4 800-1 600 4.8X10-5 10. 51 2. 5XIO"4 800-1 600 7.8 XIO-4 170.82 5.1X10-5 GL 200- 400 6. 4X10"4 140.16 8.1X10-3 CL 400- 800 2.7X10-4 59.13 2.6X10-3 800-1, 600 1.5X10-4 32.85 i.oxio-3 200- 400 2.9X10-4 63. 51 4.0X10-» CL-SM 400- 800 3.2X10-4 70.08 2.8X10-» 800-1 600 2.1 XIO"4 45.99 9.6X10-4 400- 800 5.2X10-4 115.88 7.3 XIO"4 CL 800-1 600 2.8X10-4 61.32 1.7X10-* 800-1 600 3. 7X10-5 8.10 1.2X10-* CL * Cc was roughly evaluated for comparison purpose although it was realized that the curve does not give a straight line. J Nonplastic. 1 Ct was not measurable because of pronounced curvature and insufficient straight-line portion. * Sample 23L235 tested for sample 23L20. 1 C, value is doubtful because of the firmness of the specimen, and pressures are not high enough to exceed overburden pressures for a sufficient portion of the curve.PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A67 Table 10.—Summary of selected physical and hydrologic properties for samples grouped by sediment class (Shepard system) Range Property Samples Average Low High CORE HOLE 14/13-11D1 Sand Permeability: Vertical gpd per sq ft.. 20 0.2 360 58 Dry unit weight- gperco.. Specific gravity Porosity percent.. Acid solubility do 20 20 20 12 1 1.37 2. 67 35.4 .8 1.75 2. 77 49.3 6.0 1.53 2. 71 43.6 2.6 38 Clayey sand Permeability: Vertical gpd per sq ft.. 4 0.0001 4 1 Dry unit weight... g per cc.. Specific gravity 4 4 4 1 1.64 2.64 28.0 3.2 1.95 2. 72 37.9 3.2 1.81 2.69 32.7 3.2 Acid solubility .do Sand-silt-clay Permeability: Vertical... Horizontal gpd per sq ft.. 11 1 0.0001 .2 2 0.2 0.3 .2 Dry unit weight g per cc.. 15 16 1.17 2. 65 1.86 2.76 1.56 2.70 Porosity Acid solubility ..percent.. ...do 15 11 10 30.9 2.8 26 55.8 7.6 54 42.2 5.2 37 Clayey silt Permeability: Vertical gpd per sq ft.. 5 0.0006 0.01 0.003 Dry unit weight g per cc.. 26 1.18 1.87 l. 6i Specific gravity 26 2.63 2. 79 2.73 Porosity percent.. 26 31.8 55.1 41.1 Acid solubility do 15 2.0 8.8 5.2 Liquid limit 24 30 80 48 Silty sand Permeability: Vertical gpd per sq. ft.. 16 0.0005 22 3 Horizontal gpd per sq. ft.. 1 10 10 10 Dry unit weight g per cc.. 17 1.42 1.94 1.62 Specific gravity 17 2.66 2.75 2.72 Porosity percent.. 17 28.7 47.8 40.6 Acid solubility do 9 3.2 6.4 4.9 Liciuid limit 1 30 Sandy silt Permeability: Vertical gpd per sq. ft.. 4 0.0006 0.2 0.7 Horizontal gpd per sq. ft.. 1 2 2 2 Dry unit weight g per cc.. 4 1.57 1.69 1.63 Specific gravity 4 2.68 2.75 2.72 Porosity percent.. 4 36.9 42.9 40.1 Acid solubility do 2 1.6 3.6 2.6 1 25 Silt Permeability: Vertical. gpd per sq. ft.. Horizontal gpd per sq. ft.. 1 0.002 0.002 0.002 Dry unit weight g per cc.. Specific gravity 2 2 2 1 1.31 2.68 50.4 4.0 1.33 2.74 52.2 4.0 1.32 2.71 51.3 4.0 Acid solubility t..do. . Liquid limit Silty clay Permeability: Vertical gpd per sq. ft.. 6 0.0001 0.01 0.003 Horizontal gpd per sq. ft.. 2 .002 .03 .02 Dry unit weight ..g per cc.. 12 1.25 1.72 1.49 Specific gravity 12 2.62 2.76 2.68 Porosity — ..percent.. 12 36.1 52.8 44.3 Acid solubility 9 3.6 14.8 8.8 Liquid limit 11 56 82 65 Table 10.—Summary of selected physical and hydrologic properties for samples grouped by sediment class (Shepard system)—Continued Range Property Samples Average Low High CORE HOLE 16/15-34N1 Sand Permeability: Vertical gpd per sq ft.. Horizontal gpd per sq ft.. Dry unit weight g per cc.. 11 8 11 11 11 6 10 26 1.47 2.62 41.5 1.8 374 315 1.58 2.71 45.8 4.0 96 110 1; 52 2.69 44.6 3.1 Porosity percent.. Clayey sand Permeability: Vertical.. gpd per sq ft,. 2 0.001 1 0.5 Dry unit weight .*g per cc.. 2 2 2 2 1.51 2.66 37.7 4.0 1.67 2.68 42.4 5.2 1.59 2.67 40.1 4.6 Sand-silt-clay Permeability: ‘do Liquid limit.'. 22 0.0003 0.1 0.01 12 .0003 .1 .03 21 1.10 1.75 1.54 23 2.43 2.74 2.67 21 34.8 54.7 42.3 5 1.2 9.2 6.3 18 28 76 42 Silty clay Permeability: Vertical .gpd per sq ft 20 0.0001 0.006 0.0002 Horizontal gpd per sq ft.. 12 .0001 .02 .004 Dry unit weight g per cc._ 21 1.44 1.73 1.55 Specific gravity 21 2.62 2.76 2.67 Porosity percent.. 21 35.6 45.5 41.8 Acid solubility .do 17 1.6 11.6 8.1 Liquid limit... 13 37 63 51 CORE HOLE 16/15-34N1 Silty sand Permeability: Vertical gpd per sq ft.. Horizontal gpd per sq ft.. Dry unit weight. _g per cc.. Specific gravity. _ . 10 5 11 11 11 5 0.0008 .004 1.48 2.67 32.7 1.4 5 19 1.81 2.72 45.2 6.8 2 2 1.65 2.70 39.0 4.2 Acid solubility. ....do Sandy silt Permeability: Vertical gpd per sq. ft„ 6 0.001 0.07 0.01 Horizontal gpd per sq. ft 3 .03 .3 .2 Dry unit weight g per cc_. 6 1.44 1.78 1.60 Specific gravity 6 2.68 1.75 2.72 Porosity percent.. 6 39.9 47.3 42.3 Acid solubility do 4 3.0 6.4 4.9 Liquid limit 2 35 42 38 Clayey silt Permeability: Vertical.............gpd per sq. ft_. Horizontal...........gpd per sq. ft_. Dry unit weight________________g per cc_. Specific gravity......................... Porosity.......................percent.. Acid solubility...................do_____ Liquid limit_____________________________ 19 0.0002 0.2 0.02 12 .0002 .2 .004 21 1.23 1.73 1.50 21 2.63 2.75 2.69 21 35.9 54.1 44.13 12 3.4 13.6 8.3 16 38 70 50A68 MECHANICS OF AQUIFER SYSTEMS Table 10.—Summary of selected physical and hydrologic properties for samples grouped by sediment class (Shepard system)—Continued Range Property Samples Average Low High CORE HOLE 19/17-22J1, 2 Sand Permeability: Vertical gpd per sq ft.. Horizontal gpd per sq ft.. Dry unit weight g per cc__ 7 2 6 7 6 2 11 100 1. 35 2. 66 39.2 4.0 230 330 1.63 2. 70 50.0 5.6 99 215 1.50 2. 67 44.2 4.8 Porosity" I percent. _ Silty sand Permeability: Vertical gpd per sq ft 8 1 0.0003 16 4 e uer cc_ 8 1.43 1.78 1.60 9 2. 48 2. 72 2. 68 percent.. 8 34.1 46.8 40.7 __ .do 2 5.6 6.8 5.2 1 31 Clayey silt Permeability: Vertical gpd per sq ft.. gpd per sq ft . 10 0.0002 0.01 0.003 Dry unit weight 31 1.41 1.71 1.57 Specific gravity 33 2. 61 2. 73 2. 67 Porosity percent.. 31 36.4 47.2 41.2 Acid solubility 5 8.0 12.0 9.0 Liquid limit 15 35 60 46 CORE HOLE 23/25-16N1 Sand Permeability: Vertical gpd per sq ft.. Horizontal gpd per sq ft— 2 1 2 2 2 38 130 84 61 1. 61 2.70 40.6 Dry unit weight S Per cc._ Specific gravity Porosity percent.. 1.55 2.68 38.1 1.66 2. 72 43.0 Sandy silt Permeability: gpd per sq ft.. 4 0.03 0.01 0.06 ---gpd per sq ft.. 6 1.55 1. 67 1. 63 7 2.63 2.70 2.68 6 37.3 41.7 39.1 Sand-silt-clay Permeability: Vertical gpd per sq ft.. 12 0.0006 7 0.6 Horizontal.. —gpd per sq ft— 1 .09 0.09 .09 Dry unit weight 26 1.37 1.84 1. 62 Specific gravity 26 2.50 2.76 2. 67 Porosity 26 32.8 46.3 39.3 Acid solubility 5 4.8 16.0 9.1 Liquid limit 5 26 61 42 Silty clay Permeability: Vertical gpd per sq ft.. 7 0.0001 0.002 0. 001 Horizontal .. gpd per sq ft . 2 .0005 .001 .008 Dry unit weight 18 1.33 1.64 1.52 Specific gravity 19 2.60 2.71 2. 66 Porosity 18 38.6 49.6 43.0 Acid solubility 7 5.6 10.8 9.3 Liquid limit 12 28 65 53 Table 10.—Summary of selected physical and hydrologic properties for samples grouped by sediment class (Shepard system)—Continued Range Property Samples Average Low High CORE HOLE 23/25-16N1—Continued Silty sand Permeability: Vertical 9 0. 002 2 0.4 Horizontal 7 .005 .2 .07 Dry unit weight 8 1.60 1.82 1.68 Specific gravity 9 2. 66 2.73 2.69 Porosity 8 32.1 39.8 37.5 Acid solubility 3 1.7 6.2 4.7 Liquid limit 6 22 26 24 Sandy silt Permeability: Vertical gpd per sq ft.. Horizontal gpd per sq ft. Dry unit weight g per cc.. Specific gravity 6 5 6 6 6 0.005 .005 1.52 2. 66 34.2 0.6 .1 1.79 2. 75 44.7 0.1 .05 1.61 2.70 40.5 2 29 34 32 Clayey silt Permeability: Vertical gpd per sq ft.. 13 0.0002 0.06 0.008 Horizontal. gpd per sq ft.. 12 .0004 .1 .01 Dry unit weight g per cc.. 13 1.05 1.64 1.48 Specific gravity 13 2. 66 2.75 2.70 Porosity 13 39.3 61.0 45.2 Acid solubility 6 3.5 11.1 6.8 Liquid limit 8 31 63 42 CORE HOLE 24/26-36A2 Sand (including grayei) Permeability: 10 2 650 95 2 3 3 3 12 1.54 1.74 1.65 12 2.65 2.74 2.68 12 35.6 42.8 38.7 * .do... 8 0.4 3.5 1.5 Clayey sand Permeability: Vertical gpd per sq ft. Horizontal gpd per sq ft— Dry unit weight g per cc._ Specific gravity 6 3 7 7 7 6 0.0007 .01 1.25 2.65 32.8 1.0 0.4 2 1.82 2.75 52.8 7.8 0.09 .7 1.55 2.70 52.4 3.5 Sand-silt-clay Permeability: Vertical.. ... gpd per sq ft 14 0.0002 0.4 0.06 Horizontal do 8 .0008 .03 .01 Dry unit weight —g percc-. 13 1.48 1.79 1.63 Specific gravity 15 2.65 2.74 2.69 Porosity percent.. 13 32.7 44.2 39.6 Acid solubility... do 7 2.9 8.8 5.9 Liquid limit 8 27 40 35 Silty clay Permeability: Vertical -gpd per sq ft_. 2 1 2 2 2 0.0005 0.001 0.0008 .0006 1.47 2.70 45.8 Dry unit weight g percc.. Specific gravity 1.41 2.69 43.5 1.52 2.71 48.0 1 45.4 PROPERTIES OF WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A69 Table 10.—Summary of selected physical and hydrologic properties for samples grouped by sediment class (Shepard system)—Continued Range Property Samples Average Low High CORE HOLE 24/26-36 A2—Continued Table 10.—Summary of selected physical and hydrologic properties for samples grouped by sediment class (Shepard system)—Continued Range Property Samples Average Low High CORE HOLE 6S/2W-24C7—Continued Silty sand Permeability: Vertical gpd persq ft.. 38 0.001 6 0.7 Horizontal do — 21 .002 6 1 Dry unit weight __g per cc . 45 1.31 1.94 1.72 Specific gravity 45 2.68 2.77 2.73 Porosity.. percent.. 45 28.4 52.2 36.9 Acid solubility do 44 .8 12.8 5.3 Liquid limit 15 22 36 30 Sandy silt Permeability: Vertical.. gpd per sq ft.. 8 0.001 0.5 0.1 Horizontal do 3 .03 10 3 Dry unit weight g per cc._ 10 1.07 1.79 1.55 Specific gravity 10 2.41 2.79 2.70 Porosity percent.. 10 33.9 55.6 42.7 Acid solubility do— 8 4.8 12.1 7.6 Liquid limit 9 31 49 39 Sand-silt-clay Silty clay Permeability: Vertical gpd per sq ft.. 1 Horizontal gpd persq ft._ Dry unit weight g per cc.. 2 2 2 2 2 1.29 2. 76 50.2 7.8 84 1.38 2.77 53.3 7.9 90 Acid solubility \.do Sand-silt-clay Permeability: 10 0.0004 0.009 0,003 .04 1.73 2.73 36.5 12.0 38 14 .0003 16 1. 54 1.84 2.75 44.0 19.1 58 16 2.71 16 32.6 8 7.5 8 33 Silty clay Permeability: Vertical..... Horizontal.. Dry unit weight. Specific gravity. Porosity......... Acid solubility.. Liquid limit_____ gpd per sq ft., gpd per sq ft._ ------g per cc_. . percent.. —do______ 24 0.0005 5 0.2 Permeability: Vertical gpd per sq ft. 9 0.0002 0.004 14 .001 3 .3 Horizontal gpd per sq ft. 10 .0005 .006 29 1.00 1.88 1.52 Dry unit weight g per cc.. 17 1.34 1.70 29 2.58 2.77 2.70 Specific gravity 17 2.68 2.79 29 30.6 61.2 43.8 Porosity 17 36.8 50.4 24 1.5 20.8 5.7 Acid solubility do— 10 7.2 11.9 28 28 107 54 Liquid limit 12 38 68 Clayey silt CORE HOLE 7S/1E-16C6 0.001 .002 1. 56 2.72 42.8 9.5 54 Permeability: Vertical 2 0.0006 0.003 0.002 1 .02 Dry unit weight g per cc.. 2 1.41 1.46 1.44 Specific gravity 2 2.75 2.76 2.76 Porosity 2 46.9 48.9 47.9 Acid solubilitv dn 1 3.2 Liquid limit.. 2 72 74 73 CORE HOLE 6S/2W-24C7 Sandy silt Permeability: 2 0.005 0.01 0.008 .009 .1 .05 1.66 Dry unit weight 4 1.61 1.74 Specific gravity 4 2.70 2.72 2.71 Porosity Acid solubilitv 4 2 35.8 10.1 40.8 10.5 38.9 10.3 Liquid limit... 1 26 Clayey silt Permeability: Vertical gpd per sq ft. 8 0.0001 0.008 0.002 Horizontal gpd per sq ft.. 11 .0002 .009 .002 Dry unit weight 20 1.55 1.88 1.67 Specific gravity 20 2.67 2.77 2.72 Porosity 20 31.4 46.2 38.8 Acid solubility 9 7.9 12.5 10.5 Liquid limit 8 30 49 41 Sandy clay Permeability: Vertical 0 0002 Horizontal. 1 . 0003 Dry unit weight 2 1.34 1.67 1.51 Specific gravity 2 2. 66 2.71 2.69 Porosity 2 38.4 49.6 44.0 Acid solubilitv 1 6.0 Liquid limit 2 59 89 74 Sand (including gravel) Permeability: Vertical gpd per sq ft.. Horizontal gpd per sq ft . Dry unit weight g per cc._ Specific gravity 3 3 3 3 1 0.4 1.65 2.72 37.9 190 1.69 2.79 40.4 60 1.67 2.76 39.5 12.2 Silty sand Permeability: Vertical gpd per sq ft. 2 3 0.004 .001 0.03 .07 1.91 2.76 36.2 13.5 0.02 3 1.73 . UJ 1.83 2.74 33.1 12.3 3 2.71 Porosity percent.. 3 2 30.5 11.0 1 Sand-silt-clay Permeability: Vertical gpd per sq ft.. 10 0.0001 0.005 0.001 Horizontal gpd per sq ft-- 12 .0002 .01 .002 Dry unit weight g per cc.. 12 1.59 1.88 1.76 Specific gravity 12 2.70 2. 79 2.74 Porosity— 12 31.6 41.1 35.6 Acid solubility-. . do 5 12.7 18.4 15.5 Liquid limit. 7 25 33 31 Clayey silt Permeability: Vertical gpd per sq ft. 4 0.0001 0.007 0.002 Horizontal gpd per sq ft.. 7 .0002 .01 .002 Dry unit weight 7 1.59 1.80 1.65 Specific gravity 7 2.68 2.80 2.76 Porosity ..percent.. 7 34.8 42.1 40.3 Acid solubility 2 11.4 16.1 13.8 Liquid limits 2 41 50 46A70 MECHANICS OF AQUIFER SYSTEMS REFERENCES American Geological Institute, 1960, Glossary of geology and related sciences: 2d ed., Washington, 397 p. American Society for Testing Materials, 1958, Procedures for testing soils: Philadelphia, 540 p. Athy, L. F., 1930, Density, porosity, and compaction of sedimentary rocks: Am. Assoc. Petroleum Geologists Bull., v. 14, pt. 1, no. 1, p. 1-24. Atterberg, A., 1911, fiber die physikalische bodenuntersuchung, und tJber die plastizitat der tone: Internat. Mitt. Boden-kunde, v. 1, p. 10-43. Bull, W. B., 1961, Causes and mechanics of near-surface subsidence in western Fresno County, California, in Short papers in the geologic and hydrologic sciences: U.S. Geol. Survey Prof. Paper 424-B, p. B187-B189. ------- 1964, Alluvial fans and near-surface subsidence, western Fresno County, California: U.S. Geol. Survey Prof. Paper 437-A, p. A1-A71. California State Water Resources Board, 1955, Santa Clara Valley investigation: Sacramento, Bull. 7, 154 p. Casagrande, Arthur, 1932, Research on the Atterberg limits of soils: Public Roads, v. 13, no. 8, p. 121-136. ------- 1948, Classification and identification of soils: Am. Soc. Civil Engineers Trans., v. 113, p. 901-930. Clark, W. O., 1924, Ground water in Santa Clara Valley, California: U.S. Geol. Survey Water-Supply Paper 519, 209 p. Davis, F. F., 1955, Mines and mineral resources of San Mateo County, California: California Jour. Mines and Geology, v. 51, no. 4, p. 401-458. Davis, F. F., and Jennings, C. W., 1954, Mines and mineral resources of Santa Clara County, California: California Jour. Mines, Geology, v. 50, no. 2, p. 321-430. Davis, G. H., and Poland, J. F., 1957, Ground-water conditions in the Mendota-Huron area, Fresno and Kings Counties, California: U.S. Geol. Survey Water-Supply Paper 1360-G, p. 409-588. Diepenbrock, Alex, 1933, Mount Poso oil field: California Oil Fields, v. 19, no. 2, p. 12-29. Gibbs, H. J., 1953, Estimating foundation settlements by onedimensional consolidation tests: Denver, Colo., U.S. Bur. Reclamation Eng. Mon. 13, 24 p. ------- 1959, A laboratory testing study of land subsidence: Pan-Am. Conf. Soil Mech., Found. Eng., 1st, Mexico City, 1959, Proc., p. 3-36. Goldschmidt, V. M., 1926, Undersokelser over lersedi mentor-Beretning om Nordiske Jordbrugs forskeres Kongress i Osla: Copenhagen, Nordisk Jordsbrugsforskning, v. 4, no. 7, p. 434—445. Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, 1955, Proposed program for investigating land subsidence in the San Joaquin Valley, California: Sacramento, Calif., 60 p. ------- 1958, Progress report on land-subsidence investigations in the San Joaquin Valley, California, through 1957: Sacramento, Calif., 160 p., 45 pis., 5 tables. Johnson, A. I., and Morris, D. A., 1962a, Physical and hydrologic properties of water-bearing deposits from core holes in the Los Banos-Kettleman City area, California: U.S. Geol. Survey open-file report, 182 p. ------- 1962b, Relation of volumetric shrinkage to clay content of sediments from the San Joaquin Valley, California, in Short papers in geology, hydrology, and topography: U.S. Geol. Survey Prof. Paper 450-B, p. B43-B44. Klausing, R. L., and Lohman, K. E., 1964, Upper Pliocene marine strata on the east side of the San Joaquin Valley, California in Short papers in geology and hydrology: U.S. Geol. Survey Prof. Paper 475-D, p. D14-D17. Krumbein, W. C., and Pettijohn, F. J., 1938, Manual of sedimentary petrography: New York, Appleton-Century-Crofts, Inc. 549 p. Lane, E. W., Chairman, 1947, Report of the Subcommittee on Sediment Terminology: Am. Geophys. Union Trans., v. 28, p. 936-938. Lofgren, B. E., 1960, Near-surface land subsidence in western San Joaquin Valley, California: Jour. Geophys. Research, v. 65, no. 3, p. 1053-1062. ------- 1963, Land subsidence in the Arvin-Maricopa area, San Joaquin Valley, California, in Short papers in geology and hydrology: U.S. Geol. Survey Prof. Paper 475-B, p. B171-B175. Meade, R. H., 1964, Removal of water and rearrangement of particles during the compaction of clayey sediments— review: U.S. Geol. Survey Prof. Paper 497-B, 23 p. ------- 1967, Petrology of sediments underlying areas of land subsidence in central California: U.S. Geol. Survey (Prof. Paper 497-C, 83 p.). Meinzer, O. E., 1923, The occurrence of ground water in the United States, with a discussion of principles: U.S. Geol. Survey Water-Supply Paper 489, 321 p. -------ed., 1949, Hydrology, in Physics of the Earth: New York, Dover Pubs., Inc., 712 p. Miller, R. E., 1961, Compaction of an aquifer system computed from consolidation tests and decline in artesian head in Short papers in the geologic and hydrologic sciences: U.S. Geol. Survey Prof. Paper 424-B, p. B54-58. Morris, D. A., and Johnson, A. I., 1959, Correlation of Atterberg limits with geology of deep cores from subsidence areas in California: Am. Soc. Testing Materials Spec. Tech. Pub. 254, p. 183-187. Poland, J. F., and Davis, G. H., 1956, Subsidence of the land surface in the Tulare-Wasco (Delano) and Los Banos-Kettleman City areas, San Joaquin Valley, California: Am. Geophys. Union Trans., v. 37, no. 3, p. 287-296. Poland, J. F., and Green, J. H., 1962, Subsidence in the Santa Clara Valley, California—A progress report: U.S. Geol. Survey Water-Supply Paper 1619-C, 16 p. Reitemeier, R. F., 1946, Effect of moisture content on the dissolved and exchangeable ions of soils of arid regions: Soil Sci., v. 61, p. 195-214. Shepard, F. P., 1954, Nomenclature based on sand-silt-clay ratios: Jour. Sed. Petrology, v. 24, no. 3, p. 151-158. Taylor, D. W., 1948, Fundamentals of soil mechanics: New York, John Wiley & Sons, Inc., 700 p. Terzaghi, Karl, 1926, Simplified soil tests for subgrades and their physical significance: Public Roads, v. 7, p. 153-162. ------- 1943, Theoretical soil mechanics: New York, John Wiley & Sons, Inc., 510 p. Terzaghi, Karl, and Peck, R. B., 1948, Soil mechanics in engineering practice: New York, John Wiley & Sons, Inc., 566 p. Tolman, C. F., and Poland, J. F., 1940, Ground-water, saltwater infiltration, and ground-surface recession in Santa Clara Valley, Santa Clara County, California: Am. Geophys. Union Trans., pt. 1, p. 23-35.PROPERTIES OP WATER-BEARING DEPOSITS IN CENTRAL CALIFORNIA A71 Trask, P. D., 1932, Origin and environment of source sediments of petroleum: Houston, Gulf Publishing Co., 323 p. Twenhofel, W. H., and Tyler, S. A., 1941, Methods of study of sediments: New York, McGraw-Hill Book Co., Inc., 183 p. U.S. Bureau of Reclamation, 1960, Earth manual: Denver, 751 p. Wentworth, C. K., 1922, A scale of grade and class terms for clastic sediments: Jour. Geology, v. 30, p. 377-392. Wenzel, L. K., 1942, Methods for determining permeability of water-bearing materials: U.S. Geol. Survey Water-Supply Paper 887, 192 p. U.S. GOVERNMENT PRINTING OFFICE : 1967 0-263-526UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY PROFESSIONAL PAPER 497-A PLATE 1 SAMPLE U.S. Bur. of Reclamation 23L-91 23L-100 — _23L-108_ SPONTANEOUS POTENTIAL — Millivolts + 50 25 RESISTIVITY Ohms m2/m 15 30 —l I I i j L | 1 4 lAj i GRAPHIC LOG FEET --0 — GENERALIZED LITHOLOGIC DESCRIPTION (From core descriptions, drilling performance, and electric logs) 0-320 Silt, clay, and some sand, yellowish-brown 200 ------ 400 800 1000 A. CORE HOLE 12/12- 320-352 Sand, blue 352-379 Clay, plastic, dark-greenish-gray 379-465 Clay, plastic to brittle, massive, dark-greenish-gray (Corcoran Clay Member of the Tulare Formation) =-~-E 465-513 Clay, silty, greenish-gray X-XiliirrH 513-558 Sand, silty, micaceous, greenish-gray 558-568 Clay, silty, plastic to loose, greenish-gray 568-603 Clay and sand, micaceous, gray-green 603-690 Clay, silty, micaceous, grayish-green — 7 ,7 690-714 Sand, loose, massive, blue-green gray v.v.v.v.v.v /■ 714-733 Clay, silty, grayish-green, some sand 733-752 Clay, silty, plastic to firm, massive, grayish-green - 752-776 Silt, sandy, greenish-gray .Q 776-828 Sand and gravel, micaceous, greenish-gray ■TFZE 828-860 Silt, sandy and clayey, massive, greenish-gray o — O 860-931 Sand, fine to coarse, greenish-gray; gravel and silt Q — — streaks. o Conglomerate, hard, greenish-gray, below 905 feet 931-1000 Sand, poorly sorted, micaceous, greenish-black HI. LOS BANOS -KETTLEMAN CITY AREA B. CORE HOLE 14/13-11D1, LOS BANOS-KETTLEMAN CITY AREA SAMPLE U.S. Bur. of Reclamation U.S. Geol. Survey — 58CAL1 23L-197 - - 23L-198 — - 23L-200 -23L-235 -23L-201 - 58CAL10 23L-202 - 7 58CAL20 23L-204 — 7 58CAL30 23L-206 — — 58CAL40 23L-207 - 23L-208 — — 58CAL50 23L-210 — — 58CAL60 23L-212 — - 23L-214 — — 58CAL70 23L-215 — 23L-217 — : 58CAL80 23L-219 — 58CAL90 23L-221 —- 23L-222 — 23L-223 —- - 58CAL98 SPONTANEOUS POTENTIAL — Millivolts + Ohms m*/m 100 50 0 15 30 RESISTIVITY GRAPHIC LOG FEET - 200 -v.'.v.vat:— GENERALIZED LITHOLOGIC DESCRIPTION (From core descriptions, drilling performance, and electric logs) 200-415 Sand, fine to very coarse; interbedded clay and silt; yellowish-brown 400 415-565 Clay, silty, micaceous, noncalcareous, pale-to dark-yellowish-brown;some interbedded sand and silt 565-575 Clay, slightly silty, medium-bluish-gray to dark-greenish-gray (Corcoran Clay Member of the Tulare Formation) 600 575-637 Sand, fine to coarse, well-sorted, greenish-gray to dark-gray ■ /637-700 Clay, silty, olive-brown to yellowish-brown; some very fine to very coarse sand / 700-750 Sand, silty to medium-coarse; some interbedded clay and silt; moderate-yellowish-brown 750-772 Clay, silty; some mica; yellowish-brown to olive-brown 800 =r= - 772-795 Sand, fine to coarse, moderate-yellowish-brown -777 795-842 Clay, firm; some silty to sandy; yellowish-brown 842-895 Sand, fine to medium, yellowish-brown; some clay and silt •77.7 \ 895-907 Clay, firm, dark-yellowish-brown 77: \ 907-940 Sand, silty to very coarse, subangular, dusky- _ \ yellow to olive-brown 1000 ; ® *;•; 940-980 Clay, plastic to firm, micaceous, yellowish-brown to dark-bluish-gray J______________L 980-1130 Sand, fine to coarse; gravelly near top; grains angular to subangular; light-gray to grayish yellow-green; some thin hard interbedded clay and silt 1200 1130-1200 Siltstone, sandstone, calcite cemented; some in-—terbedded sand, silt, and clay; greenish-gray to brownish-black 1200-1375 Silt, clayey to sandy; thin sand and clay inter-ri-TZl bedded; greenish-gray to dark-gray 1400 _ _ . 1375-1465 Sand, silty to gravelly; some silt and clay; firm to hard, interbedded ; greenish-gray to dark-gray -77- 1465-1549 Clay, firm to very firm; some fine to medium interbedded micaceous sand; dark-greenish-gray 1600 1549-1720 Clay, firm to hard; some sand and silt; interbedded, micaceous; greenish-gray to dark-gray 1800 ----_ 1720-2000 Clay and some claystone, friable to firm, dark-greenish-gray L2000~ C. CORE HOLE 16/15-34N1. LOS BANOS-KETTLEMAN CITY AREA D. CORE HOLE 19/17 —22J1. 2, LOS BANOS-KETTLEMAN CITY AREA SAMPLE U.S. Bur. of Reclamation — 58CAL99 23L-226 23L-227 _ 23L-228 23L-229 23L-232 23L-234 U.S. Geol. Survey =- 58CAL110 — 58CAL120 —• 58CAL130 — 58CAL140 58CAL145 SPONTANEOUS POTENTIAL Millivolts RESISTIVITY 16-in. normal Ohms m 2/m 20 40 FEET — 0- GRAPHIC LOG GENERALIZED LITHOLOGIC DESCRIPTION (From core descriptions and electric logs) 7 200 400 600 750- 30-80 Silt, sandy, loose to plastic, micaceous, yellowish-brown 80-115 Sand, silty, loose to plastic, fine to coarse, yellowish-brown 115-138 Silt, sandy, loose to plastic, gravelly, calcareous, micaceous, yellowish-brown 138-258 Sand, silty, loose to plastic, fine to coarse, micaceous, yellowish-brown 258-280 Sand, silty, clayey, fine; some coarse; calcareous near bottom; micaceous, yellowish-brown 280-296 Clay, plastic, silty, micaceous, pale brown to bluish-gray, diatoms (Corcoran Clay Member of the Tulare Formation) 296-330 Sand, silty, loose to plastic, fine to coarse, micaceous, pale-olive to yellowish-brown 330-360 Clay, sandy, silty, plastic, micaceous, calcareous streaks, yellowish-brown; thin sand interbeds 360-420 Sand, silty, fine to coarse, gravelly, micaceous, yellowish-brown; thin clay interbeds 420-520 Sand, silty, clayey, fine to coarse, some gravel, calcareous streaks, micaceous, yellowish-brown; clay, silt interbeds 520-560 Clay, sandy, silty, plastic, gravelly, micaceous, yellowish-brown; calcareous streaks; carbonaceous material; thin sand interbeds 560-620 Sand, silty, loose to friable, fine to coarse, gravelly yellowish-brown; some biotite; clay interbeds 620-660 Silt, sandy, loose to plastic, micaceous, yellowish-brown; some carbonaceous material; calcareous nodules; thin sand and clay interbeds 660-680 Sand, silty, clayey, loose, fine to coarse, brown to olive; carbonaceous material 680-710 Clay, plastic, massive, micaceous, yellowish-brown; calcareous nodules 710-752 Sand, loose, friable, massive, fine to coarse, micaceous Prepared by B. E. Lofgren and R. L. Klausing E. CORE HOLE 23/25-16N1. TULARE-WASCO AREA F. CORE HOLE 24/26-36A2, TULARE-WASCO AREA G. CORE HOLE 6S/2W-24C7, SANTA CLARA VALLEY H. CORE HOLE 7S/1E-16C6. SANTA CLARA VALLEY COMPOSITE LOGS OF CORE HOLES IN THE LOS BANOS-KETTLEMAN CITY AREA TULARE-WASCO AREA, AND SANTA CLARA VALLEY, CENTRAL CALIFORNIA 263-524 0-67 (In pocket)UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY PROFESSIONAL PAPER -4?9-A PLATE 2 PARTICLE-SIZE DIAMETER, IN MILLIMETERS CLAY <0.004 SILT 0.004-0.0625 SAND GRAVEL Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 21.0 70.0 5.4 1.6 1.8 0.2 47.5 40.5 5.8 4.0 2.0 0.2 38.5 52.5 6.6 1.8 0.6 21.0 46.0 29.0 3.6 0.4 PARTICLE-SIZE DIAMETER, IN MILLIMETERS SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0.004 0 004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 52.9 44.9 1.8 0.4 30.5 32.7 8.8 15.4 12.6 23.0 65.4 3.6 6.2 1.8 9.4 24.0 44.0 22.2 0.4 PARTICLE-SIZE DIAMETER, IN MILLIMETERS SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0.004 0.004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 20.4 50.0 25.2 4.2 0.2 52.5 46.5 0.6 0.2 0.2 32.6 27.0 16.0 21.6 2.2 0.6 52.7 43.5 2.2 1.2 0.2 0.2 1 PARTICLE-SIZE DIAMETER, IN MILLIMETERS CLAY <0.004 SILT 0.004-0.0625 SAND GRAVEL Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 5.8 33.6 7.8 28.2 6.0 14.4 14.5 64.3 42.4 28.4 11.8 17.4 17.6 30.8 33.2 3.4 0.6 4.8 26.8 0.4 5.6 2.2 PARTICLE-SIZE DIAMETER, IN MILLIMETERS CLAY <0.004 SILT 0.004-0.0625 SAND GRAVEL Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 5.6 13.0 13.0 35.8 8.6 25.6 37.8 25.2 28.8 0.4 6.0 0.2 GRAPHS OF PARTICLE-SIZE DISTRIBUTION CURVES FOR SAMPLES FROM CORE HOLE 12/12-16H1 IN THE LOS BANOS-KETTLEMAN CITY AREA, CENTRAL CALIFORNIA 263-524 0-67 (In pocket)GRAPHS OF PARTICLE-SIZE DISTRIBUTION CURVES FOR SAMPLES FROM CORE HOLE 14/13-11D1 IN THE LOS BANOS-KETTLEMAN CITY AREA, CENTRAL CALIFORNIA ro CO Cn FO 0 01 *8 PERCENT OF PARTICLES OF INDICATED SIZE I 1 1 : i 1 : i | : l CLAY <0.004 yr pco o o oo o t. ,—. r-o lO o> ui O' SILT 0.004-0.0625 £ £» g § Very fine 0.0625- 0.125 isss Fine 0.125- 0.25 Medium 0.25-0.5 SAND ° Coarse 0.5-1 Very coarse 1-2 Eitf oo£ Medium 8-16 GRAVEL — «-» <71 O Very coarse 32-64 PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE 0.001 0.002 0.003 0.004 0.005 0.006 0.008 0.010 0.020 0.030 0.040 0.050 0.0625 0.125 0.250 0.5 1.0 2.0 4.0 16.0 32.0 64.0 PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE 0.001 0.002 0.003 0.004 0.005 0.006 0.008 0.010 0.020 0.030 0.040 0.050 3 0.0625 33 cS £ 0.125 2.0 16.0 32.0 64.0 PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE _ •— rsj co ^ tn ^4 oo vo o Oc30t=>0<=>0<=>e=500 0.001 ------------------ PERCENT OF PARTICLES OF INDICATED SIZE 33 33 O oo rvj m o 3» 33 0.001 0.002 0.003 0.004 0.005 0.006 0.008 0.010 0.020 0.030 0.040 0.050 0.0625 0.125 0.250 0.5 1.0 2.0 4.0 16.0 32.0 PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE SSggggsggg \ |, 1 _l 4 1 \ i _i 1 i- IX _s \\ \ \ 4U ; \ \ \ \ \ \ \ \ \ r \ \\ \ \ \ —V™ \ \ \ Ns _ -V N 4'" A Sample 57CAL76 57CAL77 57CAL78 57CAL79 i ■ i ■ ■ i !! i II - Depth, in feet 1252+-1252.5 1257 0-1257 5 1269.5-1270.0 1271.0-1271.5 PERCENT OF PARTICLES OF INDICATED SIZE 0.001 0.002 0.003 0.004 0.005 0.006 64.0 64.0 64.0 PERCENT OF PARTICLES OF INDICATED SIZE I 1 1 : i 1 III Ol OO H bbob CLAY <0.004 boboo SILT 0.004-0.0625 Very fine 0.0625- 0.125 SSSS Fine 0.125- 0.25 sS§£ Medium 0.25-0.5 SAND £g Coarse 0.5-1 Very coarse 1-2 g iff oo re Medium 8-16 GRAVEL Coarse 16-32 Very coarse 32-64 PERCENT OF PARTICLES Of indicated SIZE I 1 : i 1 : i | : i 1 jsgjjj 1 CLAY <0.004 o' b SILT 0.004-0.0625 PP?o Very fine 0.0625- 0.125 SAND O O is> is> L K> Fine 0.125- 0.25 Medium 0.25-0.5 | 0.4 0.2 Coarse 0.5-1 Very coarse 1-2 £ GRAVEL ooj? Medium 8-16 Coarse 16-32 Very coarse 32-64 percentage of particles finer by weight than indicated size PERCENT OF PARTICLES OF INDICATED SIZE I 1 1 : i 1 : i | : i 1 CLAY <0.004 SgSg SILT 0.004-0 0625 gCyiS Very fine 0.0625- 0.125 SAND Fine 0.125- 0.25 sc Medium 0.25-0.5 cs Coarse 0.5-1 S Very coarse 1-2 as! GRAVEL tn Medium 8-16 Coarse 16-32 Very coarse 32-64 PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES 01 INDICATED SIZE : i i i i i i i i i ro o wu-c CLAY <0.004 45.2 68.4 16.1 76.8 SILT 0.004-0.0625 o tr> a o> Very fine 0.0625- 0.125 SAND g § Fine 0.125- 0.25 8.0 54.8 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 ril GRAVEL oo re oo ? ^ i Coarse 1 16-32 Very coarse 32-64 PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE g PERCENT OF PARTICLES OF INDICATED SIZE ' 1 1 1 1 1 1 1 1 : i CLAY <0.004 SILT 0.004-0.0625 Very fine 0.0625- 0.125 Fine 0.125- 0.25 ISJ >— — oo o o oi L b Medium 0.25-0.5 SAND Coarse 0.5-1 Very coarse 1-2 Si Medium 8-16 GRAVEL Coarse 16-32 Very coarse 32-64 PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE UNITED STATES DEPARTMENT OF THE INTERIOR PROFESSIONAL PAPER 479-A GEOLOGICAL SURVEY PLATE 3UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY o S h- Q PARTICLE-SIZE DIAMETER. IN MILLIMETERS CLAY <0 004 SILT 0 004-0.0625 SAND GRAVEL Very fine 0 0625 0.125 Fine 0.125- 0.25 Medium 025-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 12.5 20.7 17.2 24.6 16.1 4.6 2.0 2.3 27.3 49.6 12.0 7.1 2.8 0.8 0.1 0.3 35.7 37.7 88 11.0 5.8 0.8 0.2 - 13.9 13.7 19.4 18.4 294 5.0 0.2 go LU _I LU c_? H- GO g° Q_ LU o 5 PARTICLE-SIZE DIAMETER. IN MILLIMETERS SAND GRAVEL CLAY SILT Vem Fine Medium Coarse Very Very Fine Medium Coarse Very <0 004 0 004-0 0625 fine 0.125- 025-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 35.9 48.9 9.8 4.5 0.9 48.0 33.4 13.2 3.6 1.6 0.2 13.3 14.9 14.4 39.0 16.4 1.8 0.2 38.3 51.1 4.4 2.7 0.8 0.8 0.8 0.4 0.7 o 5 PARTICLE-SIZE DIAMETER. IN MILLIMETERS CLAY <0.004 SILT 0 004-00625 SAND GRAVEL Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 27.7 67.7 4.0 0.4 0.2 40.0 58.0 1.2 0.2 0.2 0.4 30.0 31.8 11.8 14.4 10.2 1.6 0.2 31.9 48.7 10.4 7.4 1.6 oo LU CJ I— GO 2 2 O O CLAY <0.004 26.2 47.5 71.8 230 PARTICLE-SIZE DIAMETER. IN MILLIMETERS PARTICLE-SIZE DIAMETER. IN MILLIMETERS SAND GRAVEL GO SAND GRAVEL SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very 1 LU CJ> rvj CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very 0.004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse <0.004 0.004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 r?" fu 0.0625- 0.25 1-2 2-4 32-64 0.125 iSS 0.125 33.8 12.6 15.8 9.8 1.4 0.4 . o Z Z 63.6 34.0 0.8 0.8 0.8 48.5 1.8 1.6 0.6 U u_ 28.0 60.4 7.8 2.6 1.0 0.2 24.4 1.4 1.2 0.8 0.4 2j <~J 44.5 51.1 2.0 1.6 0.6 0.2 56.6 17.6 2.4 0.4 - 18.0 35.2 22.0 19.0 5.4 0.4 8 8 8 <=> o <=> PARTICLE-SIZE DIAMETER, IN MILLIMETERS CLAY <0.004 SILT 0.004-0.0625 SAND GRAVE Very fine 0.0625- 0.125 Fine 0.125-0.25 , Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Mediur 8-16 Coarse 16-32 Very coarse 32-64 24.0 53.6 12.4 8.0 1.8 0.2 61.8 28.2 4.4 3.8 1.8 30.5 61.1 5.6 2.2 0.6 - 46.5 34.9 7.8 7.4 3.4 GO LU C_3 in GO or 0.125 19.5 35.1 15.8 144 14.8 0.2 0.2 z E 3.6 6.0 8.0 34.8 38.0 9.4 0.2 16.1 35.7 184 25.2 4.4. 0.2 O Ll_ 56.5 39.3 3.0 0.6 0.6 36.5 32.7 10.2 15.0 5.0 0.5 0.1 LU 19.0 29.2 22.4 17.0 9.4 3.0 31.7 55.5 5.8 3.8 2.6 0.6 30.3 69.5 0.2 cvi po "I in id 99 8 8 8 88 1 PARTICLE-SIZE DIAMETER, IN MILLIMETERS SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0 004 0 004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 53.0 41.6 3.2 2.2 37.0 42.0 12.4 7.4 1.2 32.7 37.7 14.0 9.7 5.9 49.9 18.3 11.2 13.2 5.0 2.2 0.2 e_i rvj H— GO go PARTICLE-SIZE DIAMETER. IN MILLIMETERS CLAY 0004 SILT 0 004 0 0625 SAND GRAVEL Very fine 0 0625 0125 Fine 0125- 025 Medium 0 25 0 5 Coarse 05 1 Very coarse 1 2 Very fine 2 4 Fine 4 8 Medium 8-16 Coarse 16-32 Very coarse 32-64 448 49.0 4.0 1.6 0.4 0.2 35.6 57.4 5.2 1.2 0.2 0.4 568 390 18 1.2 1.2 405 46 5 5.4 60 16 CVI cn VT LO LO CO CD 8 8 8 88 8 S S S 8 PARTICLE-SIZE DIAMETER. IN MILLIMETERS CLAY <0.004 SILT 0 004-0.0625 SAND GRAVEL Very fine 0 0625-0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 28.3 48.0 7.0 11.0 5.7 36.0 62.0 1.6 0.2 0.2 27.3 35.2 14.6 15.8 6.2 0.6 0.2 0.1 58.4 37.0 2.4 1.4 0.8 o S PARTICLE-SIZE DIAMETER. IN MILLIMETERS SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0 004 0 004-0 0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 00625 0.25 1-2 2-4 32-64 0.125 42.5 55.5 1.4 0.4 0.2 25.5 34.7 16.8 18.0 4.0 0.8 0.2 61.9 33.7 1.6 2.0 0.8 3.5 11.7 63.0 19.2 1.8 0.8 GRAPHS OF PARTICLE-SIZE DISTRIBUTION CURVES FOR SAMPLES FROM CORE HOLE 16/15-34N1 IN THE PROFESSIONAL PAPER 497-A PLATE 4 — CVI m L/-> CO OO O CD O O Q CVI UO cp CD CD CD CD CD CD O —■ Cvl PO vy LTD UD CVI IXD CD CD 5 CD CD CD CD O C=> CD CD CD CD — CVI LCD CD CD CD CD CD CD PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER. IN MILLIMETERS SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0 004 0.004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 36.0 47.8 10.4 4.2 1.6 45.0 47.0 5.4 0.6 2.0 2.7 6.3 13.2 50.6 26.4 0.8 - 0.4 2.8 2.4 36.4 52.8 4.8 0.4 CLAY <0 004 SILT 0 004 00625 SAND GRAVEL Very fine 0 0625 0125 Fine 0 125 0.25 Medium 0 25-0 5 Coarse 0.5 1 Very coarse 1-2 Very fine 2-4 Fine 4 8 Medium 8-16 Coarse 16 32 Very coarse I 32 64 1.0 5.2 3.6 20.8 596 9.8 4.9 10.5 16.2 39.4 24.8 4.0 0.2 24.0 50.2 144 7.4 3.8 0.2 21.9 485 18.6 8.0 2.6 0.2 0.2 r? Ovj po 5 in id oo cd cd cd o o cvj lt> o s ssSssSs sssiSs 2 s — CVJ CO -3- LTD UD OO CD 8 8 8 1 88 8 S 8 CVI LO CD CD PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS CLAY <0.004 SILT 0.004-0.0625 SAND GRAVEL Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 24.2 40.4 17.6 14.4 3.4 7.4 9.5 11.6 46.5 24.5 0.0 0.0 0.1 0.4 59.8 306 5.8 3.2 0.6 57.0 35.8 4.6 2.0 0.4 0.2 t=g SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very ■" 0 004 0 004 0 0625 fine 0.125 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 00625 0.25 1-2 2-4 32-64 0.125 18.0 48.6 21.0 104 2.0 52.2 27.4 7.0 7.6 4.0 1.8 42.0 31.8 10.4 11.2 46 52.2 43.2 2.6 1.4 0.6 PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0.004 0 004-0 0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 33.3 64.2 1.9 0.2 0.2 0.2 8.8 70.2 19.0 1.6 0.2 0.2 0.5 3.9 2.6 13.0 37.7 39.8 2.4 0.1 3.0 9.0 11.8 36.7 27.4 11.0 1.0 0.1 SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very -'0 004 0 004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 00625- 0.25 1-2 2-4 32-64 0.125 50.9 44.1 2.4 1.2 1.4 54.0 38.0 4.0 2.2 1.8 22.0 53.8 13.0 8.2 2.2 0.6 0.2 59.0 20.8 5.4 8.6 6.2 PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS CLAY <0 004 SILT 0 004-0 0625 SAND GRAVEL Very fine 00625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 14.5 46.1 18.4 19.6 1.4 9.4 19.6 16.0 324 22.2 0.4 25.4 25.7 16.3 12.3 9.7 7.4 2.6 0.5 0.1 16.6 32.2 23.4 16.2 11.2 0.2 0.2 SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very -"0 004 0 004 0 0625 fine 0.125- 025-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 00625 0.25 1-2 2-4 32-64 0125 46.8 37.8 3.2 4.2 6.0 2.0 65.5 34.5 38.0 544 7.0 0.6 28.5 67.9 3.2 0.4 PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS, CLAY <0 004 SILT 0 004-0.0625 SAND GRAVEL Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 19.3 30.7 25.0 19.4 5.6 13.4 39.8 39.4 7.4 27.6 71.8 0.4 0.2 38.3 60.3 1.2 0.2 CLAY <0 004 SILT 0 004 0 0625 SAND GRAVEL Very ' fine 0 0625 0125 Fine 0125- 0.25 Medium 025-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 45.0 27.8 31.4 16.0 10.8 6.6 15.8 9.8 0.6 12.4 13.2 10.6 LOS BANOS-KETTLEMAN CITY AREA, CENTRAL CALIFORNIA 263-524 0-67 (In pocket)UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY PROFESSIONAL PAPER 497-A PLATE 5 s iiliiHI sills £ 1 0 0 o o o ddo o 6 c>oc>c>o <=> <=> d — csi -■* oo id cm m lt> us go 8 8 8 88 8 PARTICLE-SIZE DIAMETER. IN MILLIMETERS CLAY 0 004 SILT 0 004 0 0625 SAND GRAVEL CD O Fine 0.125 025 Medium 025-05 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 $8 7 35.6 3.0 1.7 1.0 29.2 388 100 13.4 8.4 0.2 170 41.2 23.2 14.2 4.3 0.1 64 0 27.6 3.8 3.0 1.2 0.4 PARTICLE-SIZE DIAMETER. IN MILLIMETERS SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very i 0 004 0 004-0 0625 fine 0125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 24.5 31.3 14.6 17.6 11.6 0.4 52.0 404 4.2 2.2 1.2 7.2 8.0 6.6 31.6 46.2 0.1 0.1 0.2 - 45.3 40.7 5.8 4.8 3.2 0.2 PARTICLE-SIZE DIAMETER, IN MILLIMETERS SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0004 0004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 57.0 42.0 0.2 0.2 0.4 0.2 12.0 16.8 17.8 46.6 6.6 0.2 31.0 55.4 7.8 3.8 1.8 0.2 10.0 43.0 29.6 15.8 1.4 0.2 PARTICLE-SIZE DIAMETER, IN MILLIMETERS SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0.004 0.004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 10.0 34.6 25.6 26.2 3.4 0.2 6.0 2.4 16.1 46.3 29.0 0.1 0.1 6.5 7.3 17.8 62.8 5.4 0.2 - 9.0 15.6 41.6 33.2 0.4 0.2 PARTICLE-SIZE DIAMETER. IN MILLIMETERS CLAY <0.004 SILT 0 004-0 0625 SAND GRAVEL Very fine 0 0625 0.125 Fine 0125 0.25 Medium 025 05 Coarse 05 1 Very coarse 12 Very fine 2-4 Fine 4 8 Medium 8 16 Coarse 16 32 Very coarse 32 64 30.0 58.6 6.4 3.0 2.0 29.0 44.2 18.4 6.0 0.8 16 7.0 2.6 2.4 15.6 57.5 142 0.7 26.8 61.2 7.0 3.6 1.4 —; ro^ioiogoo o ooocvi ir> O O O O Q ® © © — P-J ro irt lO cnj 10 © ©©©©©©© © © © O © — PM U"> O CD CD CD CD <=> CD CD doo CD O CD CD CD CD CD CD CD CD —i P~i 06 id §§ CD CD CD 3 PARTICLE-SIZE DIAMETER. IN MILLIMETERS PARTICLE-SIZE DIAMETER. IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER. IN MILLIMTERS SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0.004 0 004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 17.0 68.2 10.0 4.0 0.8 13.0 46.2 22.2 16.4 2.0 0.2 24.0 48.8 12.8 10.2 4.0 0.2 64.5 31.9 1.6 1.2 0.8 SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0.004 0.004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 41.0 28.8 9.6 11.8 8.6 0.2 21.0 54.2 18.4 5.6 0.8 39.5 56.5 1.6 1.6 0.8 53.5 37.7 4.0 3.2 1.6 SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0.004 0.004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 15.5 23.5 10.5 23.9 21.4 4.0 0.6 0.2 0.4 50.0 39.0 4.0 5.0 1.8 0.2 33.0 58.8 5.0 2.4 0.6 0.2 9.0 43.6 32.8 13.4 1.0 0.2 SAND GRAVEL CLAY SILT Very Fine Medium Coars Very Very Fine Medium Coarse Very <0.004 0 004-0.0625 fine 0.125- 0 25-0.5 0.5- coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 17.3 31.1 15.4 21.8 14.2 0.2 46.7 46.9 3.2 2.4 0.6 0.2 20.0 32.2 20.8 20.0 7.0 5.0 8.6 16.2 46.6 23.4 0.2 8 CD CD CD O OO © © © CD CD CD CD PARTICLE-SIZE DIAMETER. IN MILLIMETERS PARTICLE-SIZE DIAMETER. IN MILLIMETERS PARTICLE-SIZE DIAMETER. IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER. IN MILLIMETERS SAND GRAVEL oo SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very C_0 r^j CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very 0 004 0 004 0 0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse ^ 0.004 0.004-0 0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625 0.25 1-2 2-4 32-64 © S o o § § § o sp o 3 ® o 8 -- c-j ln o o ; p cp cp o o 8 8 8 8 = PARTICLE-SIZE DIAMETER. IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER. IN MILLIMETERS CLAY <0 004 SILT 0 004-0 0625 SAND GRAVEL Very fine 00625 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 * Medium 8-16 Coarse 16-32 Very coarse 32-64 29.0 618 4.8 3.2 1.2 49.0 41 0 4.0 3.2 2.0 0.8 27.5 50.9 8.4 10.0 3.2 36 5 45.9 8.0 7.2 2.4 0 CLAY <0.004 SILT 0.004-0.0625 SAND GRAVEL Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 31.0 41.8 10.0 12.0 5.2 26.2 58.8 9.6 4.0 1.2 0.2 20.3 39.5 15.4 16.0 8.8 41.0 45.0 6.4 6.0 1.6 CLAY <.0004 SILT 0 004-0.0625 SAND GRAVEL Very fine 0 0625-0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 22.0 46.8 12.8 12.8 5.6 30.0 48.4 7.2 8.8 5.6 32.0 50.4 8.4 6.4 2.8 21.0 73.4 2.4 2.0 1.2 SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0.004 0.004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 17.0 41.4 23.6 15.6 2.4 10.5 22.3 22.8 36.0 8.4 21.0 46.2 12.6 14.0 6.0 0.2 22.0 56.0 12.0 7.6 2.4 CLAY <0.004 SILT 0 004-0 0625 SAND GRAVEL Very fine 00625- 0.125 Fine 0.125- 0.25 Medium 025-05 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4 8 Medium 8-16 Coarse 16-32 Very coarse 32-64 20.0 56.0 10.0 9.2 4.8 28.0 42.8 12.0 134 3.8 23.3 41.9 14.8 15.6 4.4 52.0 30.0 5.6 7.6 4.8 CNt ro in u 8 8 8 81 PARTICLE-SIZE DIAMETER. IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER. IN MILLIMETERS SAND GRAVEL SAND GRAVEL C/O SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very _J LU O ^ CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very CJ> f-'J CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very 0 004 0 004 0 0625 fine 0125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse <0.004 0.004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse <0.004 0 004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 00625 0.25 1-2 2-4 32-64 0.0625- 0.25 1-2 2-4 32-64 0.0625- 0.25 1-2 2-4 32-64 0 125 o O 0.125 0.125 o cj> 55.4 6.0 6.4 3.2 0.8 . o 52.4 7.2 3.2 6.8 2.6 V— Q 18.0 13.7 6.3 1.8 LU LU 07 n 210 35.0 19.2 22.0 2.8 LU 34.0 59.0 3.6 1.8 1.6 £ ^ 38.0 46.2 7.4 6.6 1.8 400 51.0 4.2 3.0 1.6 0.2 39.0 30.8 10.2 12.6 7.4 - - 11.0 42.2 10.8 16.4 19.6 SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0.004 0 004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 16.7 48.1 28.4 4.8 2.0 45.0 49.8 2.8 1.6 0.8 41.0 43.2 7.8 6.2 1.6 0.2 39.0 29.8 6.9 13.1 11.2 CLAY <0.004 SILT 0.004-0.0625 SAND GRAVEL Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25 0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 30.0 23.0 16.4 22.8 7.6 0.2 44.5 20.1 9.2 16.6 9.6 69.0 18.8 4.0 6.0 2.0 0.2 37.2 46.6 5.4 74 34 8 § I Si 1 i 8 8 i si I S 1 Sill PARTICLE-SIZE DIAMETER. IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS SAND GRAVEL CO SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very 1 LU CJ> r>j CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <-0 004 0.004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse <0.004 0 004-0 0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 00625- 0.25 1-2 2-4 32-64 Q_ LU 0.0625- 0.25 1-2 2-4 32-64 0.125 S3 0.125 20.7 63.7 9.2 44 2.0 Z Z 58.8 39.0 0.8 1.0 0.4 61.0 28.8 4.6 4.0 1.5 0.1 O u. 23.0 65.8 9.0 1.8 0.4 60.5 25.3 4.2 6.0 3.6 0.4 UJ ° 23.5 70.3 5.6 0.4 0.2 49.8 48.0 1.2 0.8 0.2 SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0.004 0.004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 21.4 57.0 15.0 5.4 1.2 36.8 45.0 11.8 5.4 1.0 26.0 42.2 15.6 12.6 3.6 13.4 31.2 18.0 27.8 9.2 0.4 SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0 004 0 004-0 0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0,25 1-2 2-4 32-64 0.125 30.0 65.6 2.4 1.6 0.4 53.5 17.7 7.6 13.0 8.2 29.5 68.5 1.6 0.4 44.5 34.5 4.0 8.4 7.8 0.8 GRAPHS OF PARTICLE-SIZE DISTRIBUTION CURVES FOR SAMPLES FROM CORE HOLE 19/17-22J1, 2 IN THE LOS BANOS-KETTLEMAN CITY AREA, CENTRAL CALIFORNIA 263-524 0-67 (In pocket)PERCENT OF PARTICLES Of indicated size PERCENT OF PARTICLES OF INDICATED SIZE o PS > Z H K W > PS w I U1 o o > 50 H > o > 50 I—I Cl r H CO I—I N W O hH CO 50 I—i 00 CJ H hH o z ci d 50 < CO n H 2 H 50 > Cl > l-H c 50 hH > C 50 CO £ 10 t-< H CO 50 O S n o 50 H K O r M o CO ■g n x- o> PERCENT OF PARTICLES OF INDICATED SIZE AO.U 22.6 14.5 34.0 CLAY <0.004 SILT 0 004-0.0625 60 CT> bo cr> Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 SAND Coarse 0.5-1 no no no bo Very coarse 1-2 0.4 00S Medium 8-16 GRAVEL Coarse 16-32 Very coarse 32-64 PERCENT OF PARTICLES OF INDICATED SIZE ! CLAY <0.004 Is SILT 0 0)4-0.0625 ££ Very fine 0.0625- 0.125 SAND Fine 0.125- 0.25 9.6 4.2 Medium 0.25-0.5 g- Coarse 0.5-1 ss Very coarse 1-2 GRAVEL Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE ! 1 1 : 1 1 : 1 1 : 1 1 CLAY <0.004 2 C/5 1 j Very fine 0.0625- 0.125 SAND 22.8 22.2 8.2 22.0 Fine 0.125- 0.25 ssss Medium 0.25-0.5 Coarse 0.5-1 90 Very coarse 1-2 fvj < GRAVEL OO n Medium 8-16 Coarse 16-32 Very coarse 32-64 0.001 0.002 0.003 0.004 0.005 0.006 0.008 0.010 0.020 0.030 0.040 0.050 0.0625 0.125 0.250 0.5 1.0 2.0 4.0 8.0 16.0 32.0 64.0 PERCENT OF PARTICLES OF INDICATED SIZE ill III CLAY <0.004 — 5“ SsSS SILT 0.004-0.0625 ho ho bo bo Very fine 0.0625- 0.125 I 10.4 2.0 , 22.0 1 13.0 Fine 0.125- 0.25 Medium 0.25-0.5 SAND 4.0 2.0 Coarse 0.5-1 £ Very coarse 1-2 hS-f 00 n Medium 8-16 GRAVEL Coarse 16-32 Very coarse 32-64 PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE 0.001 0002 0003 0.004 0.005 0006 0.008 0.010 0.020 0.030 0.040 0.050 5 0.0625 g 0.125 2.0 4.0 16.0 32.0 640 PERCENT OF PARTICLES PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE OF INDICATED SIZE c->«=>e=>C3C3000t=3C50 PERCENT OF PARTICLES OF INDICATED SIZE 0.001 0.002 0.003 0.004 0.005 0.006 4.0 16.0 32.0 64.0 64.0 PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE 00 to S PERCENT OF PARTICLES OF INDICATED SIZE -V A \ Sin ah in 00 00 00 OO SS2S 1 -X X = £> PERCENT OF PARTICLES OF INDICATED SIZE I 1 1 1 1 1 1 I : 1 1 CLAY <0.004 to uj in oj SILT 0.004-0.0625 Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 SAND £££ £ Coarse 0.5-1 £ Very coarse 1-2 2sf 00 j? Medium 8-16 GRAVEL Coarse 16-32 Very coarse 32-64 PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE SKSSSSSSS PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE \ \ OO OO OO OO CO OOOO 3» 3> 3> 3 in in in in ™ in ui in in 3 • \ X~ X -"x X X \ -"V III 1 1 1 1 1 1 CLAY <0.004 ££££ SILT 0.004-0 0625 tu OO X JO Very fine 0.0625- 0.125 •— 10 in no bo A* bo bo Fine 0.125- 0.25 MOUN Medium 0.25-0.5 SAND * Coarse 0.5-1 \ 0.2 Very coarse 1-2 no ST J*" An =’ 00 n, Medium 8-16 GRAVEL Coarse 16-32 Very coarse 32-64 III ill in cn 10 cr> to in Lo ho io-bk) A c-> 1? SILT 0 004-0 0625 — 00 ~ !S M A ID t. Very fine 0.0625- 0.125 SAND - 0 to OO boo Abo Fine 0.125- 0.25 no in 10 Medium 0.25-0.5 £££ Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 GRAVEL Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE V V 5 ~ = b X X X i 1 1 : 1 1 : 1 I : 1 1 ^ b> l CLAY <0.004 en ct! 23 SILT 0 004-0.0625 Very fine 0.0625- 0.125 ££££ Fine 0.125- 0.25 0.4 1.4 2.4 1.4 Medium 0.25-0.5 SAND Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 £3 Medium 8-16 GRAVEL Coarse 16-32 Very coarse 32-64 PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE N ° 5^ n UNITED STATES DEPARTMENT OF THE INTERIOR PROFESSIONAL PAPER 497-A GEOLOGICAL SURVEY PLATE 6GRAPHS OF PARTICLE-SIZE DISTRIBUTION CURVES FOR SAMPLES FROM CORE HOLE 6S/2W-24C7 IN THE SANTA CLARA VALLEY, CENTRAL CALIFORNIA PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE III ill CLAY <0.004 Fo to Ln ;—i SILT 0 004-0 0625 --OPO O FsJ o bo Very fine 0.0625- 0.125 SAND cn Fine 0.125- 0.25 13.2 0.2 Medium 0.25-0.5 o Fo Coarse 0.5-1 Very coarse 1-2 GRAVEL oo3 Medium 8-16 TS Very coarse 32-64 PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE : i | : i I : i | : i 1 A o o 2» o -< SILT 0.004-0 0625 14.6 11.0 21.2 5.4 Very fine ! 0.0625-0.125 Fine 0.125- 0.25 2.4 2.0 1.0 1.4 Medium 0.25-0.5 SAND 0.2 0.4 0.4 Coarse 0.5-1 <3 O <3 Fo Very coarse 1-2 10 10 £ ^ 0.4 oo re Medium 8-16 GRAVEL Coarse 16-32 Very coarse 32-64 PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE *—■ co -&>» <_n -g oo ® o PERCENT OF PARTICLES OF INDICATED SIZE III ill --i oo — CLAY <0.004 S’ S O SILT 0.004-0.0625 co — <3 <3 it* It* Very fine 0.0625- 0.125 SAND 1.2 3.2 2.0 2.6 Fine 0.125- 0.25 OO OO & Medium 0.25-0.5 <3 o bo Fo Coarse 0.5-1 <3 Very coarse 1-2 ins GRAVEL oog Medium 8-16 Coarse 16-32 Very coarse 32-64 PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE Fo oo In io Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 SAND 20 20 90 Coarse 0.5-1 0.6 0.4 Very coarse 1-2 0.5 0.8 0.2 1.0 s Medium 8-16 GRAVEL Coarse 16-32 Very coarse 32-64 PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENTAGE OF PARTICLES FINER BY WEI'.'HT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE : 1 1 : i 1 ill CLAY <0.004 o! S o’ re SILT 0.004-0.0625 ££ £ Very fine 0.0625- 0.125 SAND Fine 0.125- 0.25 ZSSZ Medium 0.25-0.5 FSSC Coarse 0.5-1 £ S Very coarse 1-2 S 5 Very fine 2-4 GRAVEL S ooj? g Medium 8-16 Coarse 16-32 Very coarse 32-64 PERCENTAGE OF PARTICLES FINER BY WEIGHT THAN INDICATED SIZE PERCENT OF PARTICLES OF INDICATED SIZE J3.J 26.5 37.5 - 41.1 > CLAY <0.004 oo^— Soi §S2 ! ^ cn & 6 Very fine 0.0625- 0.125 --j oo o o <3 <3 o o o > UNITED STATES DEPARTMENT OF THE INTERIOR PROFESSIONAL PAPER 497- GEOLOGICAL SURVEY PLATE 8UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY PROFESSIONAL PAPER 497-A PLATE 9 PARTICLE-SIZE DIAMETER, IN MILLIMETERS CLAY <0.004 SILT 0.004-0.0625 SAND GRAVEL Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 47.5 27.8 9.2 12.0 2.8 0.4 0.2 0.1 20.5 54.9 23.8 0.4 0.4 42.6 52.0 3.4 1.6 0.2 0.2 - - 35.3 46.6 5.3 6.0 2.5 0.4 0.6 0.6 0.6 2.1 PARTICLE-SIZE DIAMETER, IN MILLIMETERS CLAY <0.004 SILT 0.004-0.0625 SAND GRAVEL Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 26.0 55.9 10.0 5.0 2.2 0.6 0.2 0.1 29.4 47.0 11.5 8.2 1.6 0.6 0.2 0.5 0.5 0.5 81 4.9 31.4 48.1 5.5 0.6 0.7 0.7 47.2 51.6 1.0 0.0 0.2 PARTICLE-SIZE DIAMETER, IN MILLIMETERS CLAY <0.004 SILT 0.004-0.0625 SAND GRAVEL Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 15.4 38.9 26.0 18.4 1.0 0.2 0.0 0.1 52.7 47.1 0.2 29.4 43.1 11.9 11.2 3.2 0.8 0.2 0.2 7.7 16.8 21.0 38.4 13.8 1.8 0.2 0.2 0.1 PARTICLE-SIZE DIAMETER, IN MILLIMETERS SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0.004 0.004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 29.7 35.9 11.6 10.8 3.8 1.3 1.1 1.4 3.3 1.1 27.2 41.2 11.6 11.1 5.3 1.6 0.8 0.4 0.2 0.6 21.0 38.0 13.0 16.7 7.7 2.0 1.0 0.6 21.4 44.9 15.5 13.8 3.4 0.6 0.2 0.2 PARTICLE-SIZE DIAMETER, IN MILLIMETERS PARTICLE-SIZE DIAMETER, IN MILLIMETERS CLAY <0.004 SILT 0.004-0.0625 SAND GRAVEL Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 18.5 35.0 14.0 17.8 7.0 2.0 1.3 1.6 2.1 0.7 30.1 46.4 8.8 7.4 3.3 1.2 0.4 1.4 1.0 13.5 21.8 9.3 16.7 20.1 8.1 4.3 4.4 1.8 37.1 41.9 9.2 6.5 2.2 1.8 0.8 0.5 SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0.004 0.004-0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 5.4 1.7 5.5 13.8 16.6 11.4 11.9 16.0 13.4 4.3 26.1 46.0 15.7 8.3 2.4 0.4 0.4 0.4 0.3 17.3 66.9 12.6 3.0 0.2 24.2 54.8 14.8 5.2 0.6 0.2 0.2 PARTICLE-SIZE DIAMETER, IN MILLIMETERS CLAY <0.004 SILT 0 004 0.0625 SAND GRAVEL Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 025-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 19.0 60.2 14.2 6.0 0.4 0.2 27.3 54.7 10.8 5.6 1.2 0.4 34.3 49.8 7.0 5.6 2.4 0.6 0.2 0.1 PARTICLE-SIZE DIAMETER, IN MILLIMETERS SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very ,'0 004 0 004-0 0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 34.0 56.0 4.8 3.4 1.4 0.2 0.2 30.2 42.4 13.1 10.2 2.4 0.6 0.8 0.3 27.5 26.1 9.5 13.7 5.3 1.0 1.5 3.6 7.8 4.0 - 33.0 42.4 9.8 9.0 3.8 1.2 0.8 PARTICLE-SIZE DIAMETER, IN MILLIMETERS CLAY <0.004 SILT 0.004-0.0625 SAND GRAVEL Very fine 0.0625- 0.125 Fine 0.125- 0.25 Medium 0.25-0.5 Coarse 0.5-1 Very coarse 1-2 Very fine 2-4 Fine 4-8 Medium 8-16 Coarse 16-32 Very coarse 32-64 38.0 41.6 8.8 6.5 2.8 1.0 0.6 0.3 0.4 26.5 59.3 5.8 5.4 2.2 0.6 0.2 33.8 55.8 6.4 2.2 1.0 0.6 0.2 - - 23.3 46.6 12.4 8.9 3.5 0.7 1.4 1.6 1.6 PARTICLE-SIZE DIAMETER, IN MILLIMETERS SAND GRAVEL CLAY SILT Very Fine Medium Coarse Very Very Fine Medium Coarse Very <0.004 0.004 0.0625 fine 0.125- 0.25-0.5 0.5-1 coarse fine 4-8 8-16 16-32 coarse 0.0625- 0.25 1-2 2-4 32-64 0.125 24.0 58.4 12.6 4.4 0.4 0.2 36.0 52.4 5.6 3.4 1.8 0.6 0.2 GRAPHS OF PARTICLE-SIZE DISTRIBUTION CURVES FOR SAMPLES FROM CORE HOLE 7S/1E-16C6 IN THE SANTA CLARA VALLEY, CENTRAL CALIFORNIA 263-524 0-67 (In pocket)UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY PROFESSIONAL PAPER 497-A PLATE 10 INTERIOR —GEOLOGICAL SURVEY. WASHINGTON. 0. C . —1967 —W66212 MISSISSIPPI VALLEY SEDIMENT CLASSIFICATION TRIANGLE (CASAGRANDE, 1948)VOID RATIO (e) VOID RATIO (e) UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY LOAD, IN POUNDS PER SQUARE INCH 0.1 1 10 100 1000 10,000 LOAD, IN POUNDS PER SQUARE INCH PROFESSIONAL PAPER 497-A PLATE 11 0.1 10 100 LOAD, IN POUNDS PER SQUARE INCH 1000 10,000 A. CORE HOLE 12/12-16H1, LOS BANOS-KETTLEMAN CITY AREA B. CORE HOLE 14/13-11D1. LOS BANOS-KETTLEMAN CITY AREA C. CORE HOLE 16/15-34N1, LOS BANOS-KETTLEMAN CITY AREA LOAD, IN POUNDS PER SQUARE INCH 0.1 10 100 LOAD, IN POUNDS PER SQUARE INCH 1000 10,000 D. CORE HOLE 19/17-22J1. 2, LOS BANOS-KETTLEMAN CITY AREA E. CORE HOLE 23/25-16N1, TULARE-WASCO AREA F. CORE HOLE 24/26-36A2. TULARE-WASCO AREA LOAD, IN POUNDS PER SQUARE INCH LOAD, IN POUNDS PER SQUARE INCH G. CORE HOLE 6S/2W-24C7, SANTA CLARA VALLEY H. CORE HOLE 7S/1E-16C6. SANTA CLARA VALLEY GRAPHS OF CONSOLIDATION TEST CURVES FOR SELECTED SAMPLES FROM CORE HOLES IN THE LOS BANOS-KETTLEMAN CITY AREA TULARE-WASCO AREA, AND SANTA CLARA VALLEY, CENTRAL CALIFORNIA 263-524 0-67 (In pocket)CORE HOLE 1 9/17-22J 1,2 CORE HOLE 16/15-34N1 CORE HOLE 14/1 3— 11 D1 DEPTH, IN FEET BELOW LAND SURFACE DEPTH, IN FEET BELOW LAND SURFACE DEPTH, IN FEET BELOW LAND SURFACE UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY PROFESSIONAL PAPER 497-A PLATE 12 SPONTANEOUS RESISITIVITY POTENTIAL1 ELECTRIC COEFFIEIENT OF PERMEABILITY, IN LOG GALLONS PER DAY PER SQUARE FOOT (vertical) CLAY-SIZE PARTICLES (<0.004 mm), IN PERCENT SPECIFIC GRAVITY GRAMS PER CUBIC CENTIMETER POUNDS PER CUBIC FOOT DRY UNIT WEIGHT POROSITY, IN PERCENT ■st CD 00 O d d o>h VOID RATIO POROSITY AND VOID RATIO ATTERBERG LIMITS ^ •-< CM MILLEQUIVALENTS PER 100 GRAMS OF SOIL TONS PER ACRE-FOOT VOLUMETRIC SHRINKAGE, IN PERCENT OF DRY VOLUME TOUGHNESS INDEX ACID SOLUBILITY, IN PERCENT GYPSUM CONTENT GRAPHS OF PHYSICAL PROPERTIES OF SAMPLES FROM CORE HOLES IN THE LOS BANOS-KETTLEMAN CITY AREA, CENTRAL CALIFORNIA 263-524 0-67 (In pocket) DEPTH, IN FEET BELOW LAND SURFACE DEPTH, IN FEET BELOW LAND SURFACE DEPTH, IN FEET BELOW LAND SURFACEUNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY PROFESSIONAL PAPER 497-A PLATE 13 z 10 7 m CM 00 CM LjJ _J 0 1 bJ or O U o z 3 POTENTIAL I I I I___________________________________________________________________I______________I____________I ELECTRIC LOG COEFFICIENT OF PERMEABILITY, IN GALLONS PER DAY PER SQUARE FOOT (vertical) CLAY-SIZE PARTICLES (<0.004 mm), IN PERCENT SPECIFIC GRAVITY GRAMS PER CUBIC CENTIMETER ,___I___|___I___i___I___1___L o o o o oo ° c\j IM- POUNDS PER CUBIC FOOT DRY UNIT WEIGHT POROSITY, IN PERCENT I III III *3- CD OO O C\l CD O O O *-i ,-J r-i —i VOID RATIO POROSITY AND VOID RATIO z_ Plastic limit Liquid limit - I i -Shrinkage limit -Plasticity index -Shrinkage limit - Plastic limit Liquid limit Plasticity index i—i CM CO I i I i I MILLIEQUIVALENTS PER 100 GRAMS OF SOIL J___i___Lj____I i I J_ s ATTERBERG IMITS VOLUMETRIC SHRINKAGE, IN PERCENT OF DRY VOLUME TOUGHNESS INDEX ACID SOLUBILITY, IN PERCENT TONS PER ACRE-FOOT GYPSUM CONTENT GRAPHS OF PHYSICAL PROPERTIES OF SAMPLES FROM CORE HOLES IN TIE TULARE-WASCO AREA, CENTRAL CALIFORNIA 263-524 0-67 (In pocket) DEPTH, IN FEET BELOW LAND SURFACEUNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY tD O CD 7 W (/) P' 111 _l 0 1 LU cc o O POTENTIAL ELECTRIC COEFFICIENT OF PERMEABILITY, IN LOG GALLONS PER DAY PER SQUARE FOOT (vertical) CLAY-SIZE PARTICLES (<0.004 mm), IN PERCENT SPECIFIC GRAVITY GRAMS PER CUBIC CENTIMETER POROSITY, IN PERCENT o o o O CN 'S’ <3; CD CO O *3- CD O o O —i f-i POUNDS PER CUBIC FOOT VOID RATIO DRY UNIT WEIGHT POROSITY AND VOID RATIO ATTERBERG LIMITS VOLUMETRIC SHRINKAGE, IN PERCENT OF DRY VOLUME TOUGHNESS INDEX PROFESSIONAL PAPER 497-A PLATE 14 ACID SOLUBILITY, IN PERCENT o 100 200 300 400 500 600 700 800 900 1000 |“H »—I CSJ MILLEQUIVALENTS PER 100 GRAMS OF SOIL TONS PER ACRE-FOOT GYPSUM CONTENT GRAPHS OF PHYSICAL PROPERTIES OF SAMPLES FROM CORE HOLES IN THE SANTA CLARA VALLEY, CENTRAL CALIFORNIA 263-524 0-67 (In pocket) DEPTH, IN FEET BELOW LAND SURFACE/-cotqc/e: (peys />& „ h Yf7‘£ \ Removal of Water and * Rearrangement of Particles f I During the Compaction of \ Clayey Sediments—Review ________________________ GEOLOGICAL SURVEY PROFESSIONAL PAPER 497-B» ( 1 1 *Removal of Water and Rearrangement of Particles During the Compaction of Clayey Sediments—Review By ROBERT H. MEADE MECHANICS OF AQUIFER SYSTEMS GEOLOGICAL SURVEY PROFESSIONAL Review of the pertinent literature on the factors influencing the water content and clay-particle fabric of clayey sediments under increasing overburden pressures UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402CONTENTS Page Glossary_______________________________________________ iv Abstract___________________________________________________ B1 Introduction________________________________________________ 1 Purpose of study_______________________________________ 2 Acknowledgments________________________________________ 2 Forces related to clay-mineral surfaces_____________________ 2 Forces between clay-mineral particles and water___ 2 Hydration of clays_________________________________ 2 Properties of adsorbed water_______________________ 2 Forces between adjacent clay-mineral particles____ 3 Repulsion between particles: double-layer forces. 3 Explanation in terms of osmosis_______________ 3 Attraction between particles_______________________ 4 Van der Waals forces and their relation to double-layer repulsion______________________ 4 Edge-to-face attraction_______________________ 5 Factors influencing the removal of water during the early stages of compaction______________________________________ 5 Particle size__________________________________________ 5 Clay minerals__________________________________________ 5 Interstitial electrolyte solutions_____________________ 7 NaCl-montmorillonite-water mixtures________________ 7 NaCl-illite-water mixtures________________________ 9 Other electrolyte-montmorillonite-water mixtures______________________________________________ 9 Page Factors influencing the removal of water, etc.—Con. Interstital electrolyte solutions—Continued MgCla (or CaClj)-illite-water mixtures_________ BIO Exchangeable cations________________________________ 11 Removal of water during the later stages of compaction. 12 Fabric of clays and its changes under pressure___________ 13 Factors, other than pressure, that influence the arrangement of clay particles_____________________ 14 Electrolyte concentration_______________________ 14 Cations and anions______________________________ 15 Acidity_________________________________________ 15 Organic matter__________________________________ 15 Physical conditions of deposition_______________ 16 Fabric of uncompacted natural clays_________________ 16 Influence of pressure on the fabric of clays________ 17 Fabric of clays compressed in the laboratory_ 17 Unconfined compression______________________ 17 Compression of laterally confined clays__ 17 Influence of electrolyte concentration under pressure__________________________________ 18 Fabric of naturally compacted clayey sediments. 18 Summary__________________________________________________ 20 References_______________________________________________ 21 ILLUSTRATIONS Page Figure 1. Explanation, in terms of osmosis, of difference in swelling of clay aggregates in electrolyte solutions of low and high concentrations______________________________________________________________________________________________ B4 2. Forces between basal (001) surfaces of adjacent clay-mineral particles, as a function of interparticle distance___ 4 3. Influence of particle size on void ratio of fine-grained sediments_________________________________________________ 6 4. Influence of clay minerals on relation between void ratio and compacting pressure__________________________________ 6 5. Clay particles and their envelopes of adsorbed water______________________________________________________________ 7 6. Influence of NaCl concentration on relation between void ratio and pressure in montmorillonite_____________________ 8 7. Relations between NaCl concentration, interparticle spacing, and pressure in montmorillonite_______________________ 8 8. Influence of NaCl concentration and particle size on relation between void ratio and pressure in Fithian illite___ 9 9. Experimental and theoretical relations between interparticle spacing and pressure in mixture of montmorillonite and 2X10-4 N CaCl2 solution______________________________________________________________________________________ 10 10. Influence of MgCla concentration on relation between void ratio and pressure in <2.0-micron fractions of illite_ 10 11. Influence of exchangeable cations on relation between void ratio and pressure in montmorillonite__________________ 11 12. Influence of exchangeable cations on relation between void ratio and pressure in kaolinite________________________ 12 13. Pressure-temperature curves for dehydration reactions of montmorillonite minerals saturated with sodium, calcium, and magnesium___________________________________________________________________________________________ 13 14. Idealized arrangements of clay-mineral particles in sediments_____________________________________________________ 13 15. Horizontal preferred orientation of montmorillonite in unconsolidated clayey sediments from three core holes in San Joaquin Valley, Calif_____________________________________________________________________________________ 19 inf GLOSSARY Compaction. “* * * decrease in volume of sediments, as a result of compressive stress, usually resulting from continued deposition above them” (American Geological Institute, 1957, p. 58). This process is called « consolidation in the soil-mechanics literature. Consolidation. “* * * any or all processes whereby loose, soft, or liquid earth materials become firm and coherent” (American Geological Institute, 1957, p. 62). This includes cementation as well as compaction. Fabric. “* * * the physical constitution of a * * * [sediment] as expressed by the spatial arrangement of the solid particles and associated voids. Since * * * fabric is concerned with spatial arrangement it is described in terms of the orientation and distribution patterns of the primary particles, compound particles, and < voids” (Brewer and Sleeman, 1960, p. 173). Turbostratic. A type of fabric in which clay-mineral particles are in aggregates within which the orientation is preferred and between which the orientation is random (Aylmore and Quirk, 1960, p. 1046; adapted from Biscoe and Warren, 1942, p. 370). Void ratio. Ratio (e) of the volume of pore space to the volume of solid particles in a sediment (American Society of Civil Engineers, 1958, p. 40). Its relation to percent porosity (n) is expressed in the following formula: ^ e n 1 —n In all the studies discussed in this review, the void ratio is a volumetric index of the water content. IV * i ♦ 4MECHANICS OF AQUIFER SYSTEMS REMOVAL OF WATER AND REARRANGEMENT OF PARTICLES DURING THE COMPACTION OF CLAYEY SEDIMENTS—REVIEW By Robert H. Meade ABSTRACT Among the factors that influence the amount of water held in clayey sediments under overburden pressures between 0 and about 50 kg per cm2 are particle size, clay minerals, exchangeable cations, and interstitial-electrolyte concentration. The amount of water held in clayey sediments varies inversely with particle size through a wide range of pressures and chemical conditions. The influence of different clay minerals on water content is related mainly to their particle size. The influences of exchangeable cations and electrolyte concentration also vary with particle size: in fine-grained clays (montmorillonite, for , example), water content varies inversely with the valence of exchangeable cations and the concentration of monovalent electrolyte; in coarse-grained clays (kaolinite, for example), water content varies directly with the cation valence and the electrolyte concentration. Under overburden pressures greater than about 50 kg per cm2, the major influences on the water content of clayey sediments seem to be particle size, clay minerals, and temperature. As temperature increases, less pressure is needed to compact the clay. Variations in exchangeable cations and in electrolyte concentration do not seem to influence the water content under higher pressures, but they do affect the clay-particle fabric. Although preferred and turbostratic orientations of clay-mineral particles can be produced by compressing clays in the laboratory, there is little evidence to show that they are formed readily during natural compaction. Experimental evidence suggests that preferred orientation of particles, normal to overburden pressures, would be most likely to form in sediments that have large clay-mineral particles, low concentration and low acidity of interstitial electrolyte, and low valence of exchangeable cations. The formation of a preferred orientation also seems to be favored by the presence of organic material and the existence of a partly oriented fabric at the onset of compaction. The formation of a turbostratic fabric (particles oriented in domains which are oriented at random with respect to other domains) instead of generally preferred orientation might be favored by high electrolyte concentration and high cation valence. Among the factors whose influence on water removal and particle rearrangement might be significant, but about which little is known, are the anions and organic matter in the interstitial solutions. Also, very little is known of the relative effect of each of the several factors when their influences are combined under complex natural conditions. INTRODUCTION The advances in clay technology and soil mechanics within recent years—especially in the decade 1953-62— make possible a new look at the compaction of finegrained sediments. Instead of considering compaction as a simple relation between pore volume and overburden pressure, one can now take into account the influence of other physical and chemical factors. This review outlines a current set of questions that geologists and hydrologists can ask while investigating the compaction of clayey sediments. This is a summary of the pertinent knowledge as of 1962 of the water in clays, the removal of water under pressure, and the spatial arrangement of clay-mineral particles in sediments. Most of the information is taken from publications in fields other than geology—soil science, soil mechanics, ceramics, and physical and colloidal chemistry. Except for the theoretical discussion of forces in the first section, this review is concerned mainly with reported evidence and is only secondarily concerned with speculations and conclusions. Papers that contain little or no evidence to support their conclusions are not reviewed. Furthermore, the experimental evidence on clay behavior that has little direct counterpart in nature—the work on the influence of lithium and of cesium electrolytes, for example—is not treated fully. Finally, I have tried to point out the conspicuous gaps in the present body of knowledge. In this review I assume that the reader is already generally familiar with the structure and composition of the common clay minerals and with their more distinctive properties, such as minute size, large surface area, platy habit, and ion-adsorption and ion-exchange capacity. For a review of these subjects, see the recent and concise summary by Grim (1962, p. 7-51) or the earlier standard works by Grim (1953) and by Jas-mund (1955). I also assume that the reader is already familiar with the general pattern of the reduction of pore volume of clays under increasing overburden loads, B1B2 MECHANICS OF AQUIFER SYSTEMS which was treated in the classic paper by Hedberg (1936) and which was reviewed more recently by Engelhardt (1960, p. 35-50),by Lomtadze (1955, 1956) and by Weller (1959, p. 274-294). PURPOSE OF STUDY The U.S. Geological Survey is making an investigation directed toward determining the principles controlling the compaction of aquifer systems resulting from change in grain-to-grain load (effective stress) induced by major decrease of internal fluid pressure. This project is under the direction of J. F. Poland, research geologist. As one phase of the overall investigation, I am studying the physical and mineral characteristics of the water-bearing sediments that are compacting, the conditions under which the sediments were deposited, and the processes involved in their compaction. As background for the specific studies of these compacting sediments, this paper presents a review of what is currently known on the removal of water and the rearrangement of particles during the compaction of clayey sediments. ACKNOWLEDGMENTS I want to thank the following people for stimulating discussions and for reviewing early drafts of the manuscript : It. E. Compton, W. E. Dickinson, Kurt Servos, and G. A. Thompson, of Stanford University; J. K. Mitchell of the University of California; Wolf von Engelhardt, of the University of Tubingen; W. B. Bull, B. E. Lofgren, E. E. Miller, H. W. Olsen, J. F. Poland, Julius Schlocker, and H. A. Tourtelot, of the U.S. Geological Survey. H. van Olphen of Shell Development Co., and Prof, von Engelhardt supplied copies of manuscripts that were in press during the preparation of this review. The papers by Ts. M. Eaitburd were translated from the Eussian by Alice A. Parcel, of the U.S. Geological Survey. FORCES RELATED TO CLAY-MINERAL SURFACES Because of the large surface areas of clay minerals, the response of water-saturated clayey sediments to compacting pressures must be thought of in terms of the forces associated with clay-mineral surfaces. In very fine grained clays, such as montmorillonites, in which the surface areas may be as great as 800 m2 per g (square meters per gram), the forces related to the clay-particle surface are more pertinent to the understanding of compaction than are the gravitational forces associated with the particle mass. This section of the review is an introductory and largely theoretical discussion of the surface forces. The role of these forces in compaction processes is one of the main subjects of the subsequent sections of the review. FORCES BETWEEN CLAY-MINERAL PARTICLES AND WATER HYDRATION OF CLAYS The affinity between water and clay is well known. Dry clay will adsorb water vapor from the atmosphere. It will soak up large quantities of liquid water, if available, and swell to many times its dry volume. The cause of this attraction seems to be the negative charge on the surfaces of clay-mineral particles that arises from imperfections and substitutions within the mineral structure. The charge attracts water in at least two ways: directly, by attracting the protons of the polar water molecules; and indirectly, by attracting cations, which in turn attract water molecules. The hydration properties of the cations are significant, as the intensity and extent of the clay-water attraction are different for different adsorbed cations. Several series of experiments have shown fairly conclusively that the water closest to the surfaces of montmorillonite or vermiculite particles is adsorbed or desorbed in molecular-layer units (Barshad, 1949; Collis-George, 1955; Foster and others, 1955, p. 299-300; Mooney and others, 1952; Norrish, 1954; Eowland and others, 1956; Walker, 1956). That is, if one allows a limited amount of water or water vapor to equilibrate with an originally dry clay, the water will first cover all accessible clay surfaces in a layer one molecule thick (about 2.5 A1). A second molecular layer will be adsorbed only after all accessible surfaces have been covered with the first layer. The pattern is reversed during drying or compaction: the layer closest to the clay-mineral surface is desorbed only after the complete removal of the next closest layer. Although the formation or removal of the third, fourth, and subsequent water layers varies with the type of clay mineral and adsorbed cation, the stepwise pattern of hydration and dehydration generally holds true for a distance from the particle surfaces equivalent to several layers of water. PROPERTIES OF ADSORBED WATER The water adsorbed on the surfaces of clay minerals has properties that differ from those of ordinary liquid water because it exists in a force field. Although this difference has been known for many years (see Terzaghi, 1925, p. 746), and although hundreds of experiments have been run to define quantitatively such properties as the density and viscosity of adsorbed water, very little more can be stated with certainty. Measurements of the characteristics of adsorbed water necessarily must be made on clay-water mixtures, and the presumed influence of the solid clay particles on the measure- 1A=angstrom unit=10-® cm.REMOVAL OF WATER AND REARRANGEMENT OF PARTICLES DURING COMPACTION B3 ments is subtracted from the whole to leave what is presumed to be the effect of adsorbed water. Interpretation of the experimental data therefore must rest on theoretical or conjectural assumptions whose validity is uncertain. The significant experimental work on adsorbed water was reviewed thoroughly by Low (1961) and Martin (1962). Significantly, these two authors— both of whom are highly qualified to review the subject—reached different conclusions about the structural arrangement of water on clay-mineral surfaces. Low favored the idea that adsorbed water has a high degree of structural order and rigidity, making it more resistant than ordinary water to normal and shear stresses. Martin, on the other hand, favored a twodimensional-fluid model in which the water is essentially fluid (perhaps more so than ordinary water) in directions parallel to the mineral surface and is essentially solid in the direction normal to the mineral surface; such an arrangement would make the water more resistant to normal stress but perhaps less resistant to shear stress than is ordinary water. FORCES BETWEEN ADJACENT CLAY-MINERAL PARTICLES Another way of considering the behavior of clay-water mixtures is in terms of the forces that operate between adjacent clay particles. Interparticle forces have received increasing attention and study by soil scientists and engineers since 1948, when Verwey and Overbeek published a theoretical treatment of the forces that operate between particles in colloidal suspensions (see also Overbeek, 1952). Their theoretical concepts were introduced to soil mechanics by Jimenez Salas and Serratosa (1953), Bolt (1956), and Lambe (1958a, p. L-12; 1958b, p. 8-11) and have been useful in understanding the differences in behavior that seem to arise from variations in the chemical and physical components of soils. Because Verwey and Overbeek’s theory was devised for dilute colloidal suspensions, its application to compacted sediments is limited. No theory has yet been devised that accounts for all the phenomena observed during compaction, and the available theory provides models that are useful as long as one keeps in mind their limitations. The following discussion is taken from the papers cited above, plus Michaels (1958) and Parry (1960, p. 3.1-3.26). See also the critical discussion by Leonards (1962, p. 85-107). REPULSION BETWEEN PARTICLES: DOUBLE-LAYER FORCES The attraction between clay particles and adsorbed exchangeable ions in a clay-water mixture is opposed by the tendency of the ions to diffuse and distribute themselves evenly in water. The result is a diffuse cluster of ions about a clay particle. This system can be considered a diffuse electric double layer: one layer is formed by the negative charge on the surface of the particle, and the other layer is formed by the concentration of exchangeable cations near the particle surface. The entire double layer—comprising the clay particle, exchangeable ions, and water—is an electric field, and the water in the field is attracted by an induced electrical force. The particles in a clayey sediment repel each other because the outer parts of the double layers associated with the particles have the same net electrical charge (usually positive). The range and effectiveness of the forces of repulsion between particles are controlled by the thickness of the double layers, which probably ranges between 50 and 300 A in most natural clayey materials and which varies systematically with certain factors. For example, the thickness of the double layer can be decreased by increasing the concentration of electrolytes in the water that occupies the pore space between clay particles. Increasing the concentration of electrolytes in the pore water inhibits the tendency of the adsorbed ions to diffuse and allows them to be held more closely to the surfaces of the clay particles. This added proximity, in turn, decreases the thickness of the double layer and shortens the distances over which the repulsive forces between particles are effective. Less pressure is then needed to compact the clay. The thickness of the double layer can be decreased in other ways: by replacing the adsorbed cations with cations of higher valence, or by increasing pressure. EXPLANATION IN TERMS OF OSMOSIS A convenient, but oversimplified, way to imagine the interaction of double layers is in terms of osmotic pressure. Because a clay particle in water attracts and holds cations, it serves the same function as the semi-permeable membrane in the classic osmosis experiment. The concentration of ions on the surfaces of clay particles relative to the concentration of ions in the bulk of the clay-water system determines the magnitude and direction of the osmotic pressure. When an aggregate of clay particles having ions attached is wet by water in which the concentration of electrolytes is low, the osmotic pressure is great and forces water between the clay particles, and the aggregate swells (fig. 1 A). If the concentration of electrolytes is high (fig. IB)—the difference between the cation concentration at the clay-mineral surfaces and that in the bulk solution is less— the osmotic pressure therefore is less, and the clay has less tendency to swell. The osmotic or swelling pressure is the force that must be overcome to compact the clay.B4 MECHANICS OF AQUIFER SYSTEMS A + B + + + + + + + + + + + + + + + + + Strong osmotic pressure + + + + + + + + + + + + + + + + Weak —=*- + + + •<— osmotic + + + + pressure + + + + + + + + + + Low electrolyte concentration + + + + High electrolyte concentration Figure 1.—Explanation, In terms of osmosis, of difference in swelling of clay aggregates in electrolyte solutions of (A) low and (B) high concentrations. Clay-mineral plates, viewed edgewise, represented by dark rectangles; cations and anions, represented by + and —, respectively. Double-layer repulsion and the osmotic analogy, however, explain only part of the behavior of clay particles in water because they ignore the attractive forces that are effective when particles approach one another closely, ATTRACTION BETWEEN PARTICLES VAN DER WAALS FORCES AND THEIR RELATION TO DOUBLE-LAYER REPULSION Attractive van der Waals forces become significantly effective as the distance between clay-mineral particles is reduced to 10 or 20 A. The intensity of these forces is an inverse function of a high power (fifth to sixth power, probably, in most fine clays) of the interparticle distance. That is, the attractions are very strong at the particle surface and decrease rapidly in intensity away from the surface, as illustrated schematically by the dotted curve in figure 2A. Repulsive double-layer forces, represented by the dashed curve in figure 2A, are less intense at the particle surface, but their decrease with increasing distance between particles is less rapid. The resultant of the two types of forces (solid curve, fig. 2A) is net repulsion when particles are some distance apart and net attraction when they are very close together—on the order of 5 to 10 A. DISTANCE BETWEEN PARTICLES Figure 2.—Forces between basal (001) surfaces of adjacent clay-mineral particles, as a function of interparticle distance. Modified after Overbeek (1952, p. 272). A, Combination of repulsive double-layer and attractive van der Waals forces; B, effects of low, intermediate, and high concentration of electrolyte on net force between particles.REMOVAL OF WATER AND REARRANGEMENT OF PARTICLES DURING COMPACTION B5 The electrolyte concentration, as discussed above, influences the thickness of the double layer. If the electrolyte concentration is great enough, it may suppress the repulsive forces to a distance that lies within the distance range of net attraction and thus cause the clay particles to attract one another. This is shown schematically in figure 2B and is a currently favored explanation for the influence of electrolyte concentration on the flocculation of clay particles. EDGE-TO-FACE ATTRACTION The above conceptual framework for the interaction between double-layer and van der Waals forces, intellectually satisfying as it is, unfortunately cannot account for all the forces observed in clay-water-electrolyte mixtures, mainly because it assumes that all particles are arranged so that their basal surfaces are parallel and because it ignores the forces associated with the nonbasal edges of the particles. The existence of positive charges on the edges of clay-mineral particles is strongly supported by several lines of evidence (most of them enumerated by Lambe, 1958a, p. 8), the most convincing of which is the edge-to-face arrangement of particles seen in electron micrographs of clayey sediments (Rosenqvist, 1962, pi. 5). The positively charged edges apparently are attracted to the negatively charged basal surfaces. FACTORS INFLUENCING THE REMOVAL OF WATER DURING THE EARLY STAGES OF COMPACTION “The water content which exists within a clay mass at any given time represents a balance between the urge of the clay minerals to suck in water and the tendency of applied loads to squeeze out water” (Lambe and Whitman, 1959, p. 39). Among the significant factors that influence the tendency of clay to retain water under small overburden loads—0 to about 50 kg per cm2 (kilograms per square centimeter)—are the size and spatial arrangement of the particles, the clay-mineral constituents and their adsorbed cations, and the type and concentration of the interstitial electrolyte solutions. These factors are singled out here, not necessarily because they are the most significant influences, but because the literature contains enough material about them to make discussion profitable. The influence of other factors that may be significant—organic material, for instance—is almost completely unknown. The influence of particle arrangement on water retention when the clay is under pressure is treated in more detail in the later sections of this review. The present knowledge of the influence of the several factors, except for particle size, is based mainly on laboratory experiments. As nearly all these experiments 725-260—64---2 have been performed on selected size fractions of monomineralic clays in contact with distilled water or simple electrolytes, their results cannot be used to quantitatively predict the compaction of complex natural clay-water-electrolyte mixtures. In most experiments, furthermore, a single factor has been so isolated for study that one cannot tell whether the factor might be significant or inconsequential when it operates in concert with other factors in nature. The experiments, however, do indicate what the effects of some of the factors might be, and they provide questions that might be asked in any study of the early stages of natural compaction. PARTICLE SIZE The water content and compaction rate of finegrained sediments are inverse functions of particle size. Figure 3A shows the decrease in void ratio (a measure of water content in saturated sediments) with increasing particle size in unconsolidated sea-bottom and lake sediments. Part of the variation in the void ratio of these groups is related to their different depths of burial, which are listed below. Feet below sediment-water interface I. Lake Mead_____________________________________0 II. Lake Maracaibo_________________________________0-18 III. Reservoirs in United States____________________0-10(?) IV. Atlantic Ocean_________________________________0-9 V. Pacific and Arctic Oceans_______________________0-7(?) Most of the sediments in group III were dried at least once between the time they were deposited and the time they were sampled; the sediments in the other groups were never dewatered in their natural state. Figure 32?, which Skempton (1953, p. 55) derived from many different sediments in the United States and in Great Britain, shows that the relation between void ratio and particle size persists and that the fine sediments are compacted more rapidly than the coarser sediments under moderate overburden loads. The influence of particle size is also well demonstrated in the different void ratios and compaction rates of the different size fractions of illite shown in figure 8. CLAY MINERALS The difference in the void ratios of the three principal clay minerals under a wide range of pressures is shown in figure 4. Because the void ratio of these clays is a measure of their water content, the figure shows that under any given pressure in the range from 1 to 10,000 kg per cm2, montmorillonite retains more water than illite, and illite, in turn, retains more water than kaolin-ite. The differences in water content are related principally to differences in particle size or, more precisely,B6 MECHANICS OF AQUIFER SYSTEMS EFFECTIVE OVERBURDEN PRESSURE, IN KILOGRAMS PER SQUARE CENTIMETER Figure 3.—Influence of particle size on void ratio of fine-grained sediments. A, Unconsolidated sediments. I, Lake Mead (Sherman, 1953, p. 399) ; II, Lake Maracaibo (Sarmiento and Kirby, 1962, p. 719),; III, Reservoirs in Wyoming and other States (Hembree and others, 1952, p. 39) ; IV, Atlantic Ocean deep-sea deposits (Richards, 1962, p. 16) ; V, Pacific and Arctic Oceans, shallow and deep-sea deposits (data from Shumway, 1960, p. 454-463, and Moore, 1962, table 1). B, Generalized relation between size, void ratio, and effective overburden pressure. After Skempton (1953, p. 55). to differences in specific surface (surface area per unit mass). The following data, from Bower and Goertzen (1959), Diamond and Kinter (1958), and Kinter and Diamond (1960), show the range of the specific surface of pure clay minerals: Specific surface (to2 per g) Montmorillonite___________________________ 600-800 Illite____________________________________ 65-100 Kaolinite_________________________________ 5-30 The effect of specific surface on water sorption is shown schematically by Lambe’s conception of typical sodium-saturated clay-mineral particles isolated in electrolyte-free water (fig. 5): a fairly large particle of kaolinite and a much smaller particle of montmorillonite, each adsorbing a water envelope of the same thickness. The montmorillonite particle thus adsorbs much more water relative to its mass than does the kaolinite particle. V PRESSURE, IN KILOGRAMS PER SQUARE CENTIMETER Figure 4.—Influence of clay minerals on relation between void ratio and compacting pressure. Note different void-ratio and pressure scales in A. A, At low pressure, saturated with 10-3 N NaCl. After Mitchell (1960, figs. M—3, M-7). B, At moderate to high pressure, saturated with distilled water. After Chilingar and Knight (1960, p. 104) ; modified by conversion of moisture contents to void ratios (assuming specific gravities: illite, 2.75 g per cm3; montmorillonite and kaolinite, 2.6 g per cm3) and by conversion of psi to kg per cm2. C, At moderate to high pressure, saturated with water (ionic composition not reported). After Kriukov and Komarova (1954) ; modified by conversion of moisture contents as in B.REMOVAL OF WATER AND REARRANGEMENT OF PARTICLES DURING COMPACTION B7 B Figure 5.—Clay particles and their envelopes of adsorbed water. After Lambe (1961, p. 559). A, Typical montmorillonite particle, 1,000 by 10 A; B, typical kaolinite particle, 10,000 by 1,000 A. Differences in chemical composition within the major mineral types may have a secondary influence on the water contents of clay minerals under pressure. Foster (1958, 1955) found a negative correlation between free swelling and the substitution of iron and magnesium for aluminum in the octahedral positions of 12 different montmorillonite samples. The exchange positions of each montmorillonite sample were saturated with sodium to standardize the effects of adsorbed ions. The swelling correlated much better with octahedral substitution than with either tetrahedral substitution ' or cation-exchange capacity. The differences do not seem to be due to charge deficiencies brought about by the substitution, because magnesium and trivalent iron caused about the same reduction in swelling volume. Rather the deficiencies seem to be due to changes in internal energy and bonding relations related to the differences in polarizing power between iron and magnesium on the one hand and aluminum or the other. Although^Foster measured only the free swelling of the clays and not their behavior under increasing pressure, the different degrees of swelling should reflect at least qualitatively the degrees of resistance that the clays might offer to compaction. INTERSTITIAL ELECTROLYTE SOLUTIONS The interstitial electrolyte solutions seem to affect the response of clayey sediments to overburden loads in the range between 0 and about 10 kg per cms. The effect is a complex function of the type and concentration of electrolyte and of the size of the clay particles. In recent years, attempts have been made to rationalize these complexities in terms of the diffuse double-layer theory, and the theory seems to correspond fairly closely to the experimental observations made on mixtures of NaCl solutions and montmorillonite. Attempts at using the theory to predict the compaction and swelling behavior of other clay-water-electrolyte mixtures, however, have been only partly successful or entirely unsuccessful. NaCl-MONTMORILLONITE-WATER MIXTURES Because it provides an experimental verification of the diffuse double-layer theory, the NaCl-montmoril-lonite system probably has been given more attention than other electrolyte-clay mixtures. Experiments by Mitchell (1960), for example, showed some of the effects that the theory predicts (fig. 6): the greater interparticle distances (larger void ratios) at a given pressure are associated with the smaller electrolyte concentrations, and the presence of nonclay particles dilutes but does not otherwise influence the response of montmorillonite to pressure (note in fig. 6B that the void-ratio scale is different from that in fig. 6A). Although the agreement between the theoretical and experimental results of Mitchell’s study of unfractionated montmorillonite is not particularly close, other experiments on very fine grained montmorillonite (<0.2 micron) showed rather close agreement. (See fig. 7A; see also Bolt, 1956, p. 91, and Warkentin and Schofield, 1960, 1962.) The agreement between observed and theoretical results suggests that NaCI-montmorillonite systems satisfy the assumptions made in applying the double-layer theory to the compaction of clays. Some of these assumptions are worth examining because they do not seem to be satisfied by other electrolyte-clay systems. In addition to the validity of the Gouy-Chapman diffuse double-layer theory and the van’t Hoff osmotic equation, which are used to compute the thickness of the double layer for a given pressure (see Bolt, 1956, p. 89-90), one must assume a model of the clay-water system in which the basal planes of all particles are parallel to one another and normal to the compacting stress and in which the distance between particles is uniform for any given pressure and electrolyte concentration. Differences in particle orientation probably account for the different degrees of agreement between observed and theoretical compaction behavior in the first and subsequent compressions of montmorillonite reported by Warkentin and others (1957) (fig. 7A). During the first compression (open circles, fig. 7A), the observed interparticle spacings were greater than those predicted from theory (dashed line), probably because the orientation of montmorillonite flakes was not parallel. The compression, however, apparently improved the orientation, and the subsequent decompressions and recompressions yielded values very close to those predicted from theory. Had Mitchell (1960) repeated his loading and unloading several times, perhaps his measured values would have eventually coincided with his theoretical curves (fig. 6). That sodium montmorillonites satisfy the assumption of uniform interparticle distance for a given electrolyteB8 MECHANICS OF AQUIFER SYSTEMS PRESSURE, IN KILOGRAMS PER SQUARE CENTIMETER Figure 6.—Influence of NaCl concentration on relation between void ratio and pressure in montmorillonite. After Mitchell (1900, figs. M-7, M-8). Solid lines represent experimental results; dashed lines represent theoretical curves. A, Montmorillonite alone; B, montmorillonite plus silt (50 percent each by weight). B r40 NORMALITY OF NaCl 1 0.1 0.03 0.01 x 0 -30 £ Q- < -20 2 < 01 -10 9 o > -0 Figure 7.—Relations between NaCl concentration, interparticle spacing, and pressure in montmorillonite. A, Experimental and theoretical relations between interparticle spacing and pressure in a mixture of < 0.2-micron fraction of montmorillonite and 10-4 N NaCl. After Warkentin and others (1957, p. 496). Open circles indicate first compression ; solid circles, first decompression. Plusses indicate second compression, second decompression, and third compression. Dashed line is theoretical curve. Bt Measured relations between normality of NaCl solution and interparticle spacing in dilute suspensions of <0.1-micron fractions of montmorillonite. Data indicated by open circles from Foster and others (1955, p. 302), by plusses from Norrish (1954, p. 124) ; farthest right measurement by Norrish reported by Quirk (1960, p. 2.2). concentration was suggested by the experiments of Fos-ter and others (1955) and of Norrish (1954; also described by Norrish and Quirk, 1954), which are shown in figure 7B. Both these experiments showed an inverse linear relation between interparticle distance (measured by X-ray diffraction) and the square root of NaCl concentration at water contents greater than 50 percent by weight (void ratio about 2.6) and at electrolyte concentrations less than 0.3 N. At lesser water contents or at greater electrolyte concentrations, the interparticle distance diminishes rather abruptly to 20A or less, which corresponds in thickness to one, two, or three molecular layers of water. At water contents greater than 50 percent, the diffuse double layer apparently has the opportunity to form fully; at lesser water contents, the double layer does not seem to form, and the double-layer theory no longer accounts for the thickness of the water layers adsorbed on the particle surfaces. Graphs showing interparticle distance plotted against water content in sodium montmorillonites, not reproduced here, are similar to figure 'IB. (See also Foster and others, 1955, p. 300; Hight and others, 1962, p. 506-509;REMOVAL OF WATER AND REARRANGEMENT OF PARTICLES DURING COMPACTION B9 and either Norrish, 1954, p. 126, or Norrish and Quirk, 1954, p. 257.) NaCl-ILLITE-WATER MIXTURES The influence of NaCl concentration on the compaction behavior of illite varies with particle size. This was shown in the results of experiments on the type illite from Fithian, 111. by Bolt (1956, p. 92) and by Mitchell (1960) (fig. 8). In very fine grained illite (<0.2 micron, fig. 8A), as in the NaCl-montmorillonite system, the greater void ratio at a given pressure is associated with the more dilute electrolyte. Illite particles of this size are apparently so small that their behavior is controlled mostly by surface forces that can be predicted qualitatively (but not quantitatively—note the difference between the theoretical and measured curves) from double-layer theory. The opposite relation is found in the coarser illite (<1.0 micron, fig. 8B) : the greater void ratios are associated with the more concentrated electrolyte. This effect is even more pronounced in the coarsest illite (fig. 8(7). The coarser illite particles are apparently large enough to be affected somewhat by gravitational forces related to their mass, and their platy shapes make them susceptible to rearrangement under pressure. Only a part of their compaction takes place by decreasing the thicknesses of their double layers; the rest of it comes about through mechanical rearrangement. More pressure is required to rearrange the coarser particles that are in equilibrium with a more concentrated electrolyte because at higher concentrations of electrolytes the particles are more likely to flocculate. Once flocculated, Figure 8.—Influence of NaCl concentration and particle size on relation between void ratio and pressure in Fithian illite. Solid lines represent experimental results ; dashed lines represent theoretical curves. A, <0.2-micron fraction. After Bolt (1956, p. 92 ; also reported by Bolt and Miller, 1955, p. 287). B, <1.0-micron fraction. After Mitchell (1960, fi£. M-5). C, Unfractionated. After Mitchell (1960, fig. M—3). they are not as free to rearrange as they would be if they had been subject only to the repulsive interaction of double layers; therefore, they offer more resistance to compaction. One compression experiment on a < 2-micron fraction of kaolinite mixed with 1 N and 10‘3 N solutions of NaCl (Mitchell, 1960, fig. M-4) showed the same relation between void ratio and NaCl concentration as i that observed in the coarser grained illites. OTHER ELECTROLYTE-MONTMORIIiLONITE-WATER MIXTURES Clays mixed with other electrolytes do not always respond to compacting pressures in the same way as do clays mixed with NaCl. Montmorillonites that are mixed with electrolyte solutions containing calcirapf magnesium, or aluminum, and whose exchange positions are saturated with these cations^will not swell to interparticle distances greater than 9 A, .regardless of the dilution of the interstitial Electrolyte (Norrish, 1954; also reported by Norrish and Quirk, 1954). Apparently, some minimum-energy situation (perhaps an appropriate balance of repulsive double-layer and attractive van der Waals forces) exists at this spacing, beyond which the montmorillonite crystal will not expand freely. Likewise, montmorillonites saturated with potassium do not seem to expand readily beyond 5 or 6 A with decreasing KC1 concentration (Foster and others, 1955, p. 302-803; Norrish, 1954, p. 124). This implies that the water in these clays occupies two different types of pore space: interlamellar spaces, whose thickness does not exceed 9 A, within the clay aggregates; and “external” pore spaces between the clay aggregates. The existence of two distinctly different sizes of pore space in calcium montmorillonite is supported by the nitrogen-sorption measurements reported by Aylmore and Quirk (1962, p. 109-112). The compaction behavior of these clays, therefore, cannot be completely understood on the basis of doublelayer theory because one of the main assumptions— uniform interparticle distance at a given electrolyte concentration—is not satisfied. An example was provided by the experiment of Blackmore and Miller (1961), the results of which are shown in figure 9. They compressed a mixture of montmorillonite and 2 X 10~4 N CaCl2 solution under selected pressures and allowed it to reswell after release of pressure. The initial compressions followed fairly closely the pattern predicted from double-layer theory (dashed line). The reswelling, however, did not follow the theoretical pattern, thus suggesting that the montmorillonite flakes were compressed into aggregates that remained intact after the pressure was released. X-ray measurements supported the idea that these ag- 725-260—64- 3BIO MECHANICS OF AQUIFER SYSTEMS Figure 9.—Experimental and theoretical relations between interparticle spacing and pressure in mixture of mont-morillonite and 2 X10-4 N CaCl2 solution. After Blackmore and Miller (1961, p. 170). Theoretical curve indicated by dashed line. gregates were “domains”—packets of several parallel unit montmorillonite sheets—within which the inter-lamellar distance remained a constant 8.8 A, regardless of the total water content of the clay. MgCl2 (OR CaCl2) -IULITE-WATER MIXTURES Mixtures of <2.0-micron fractions of Fithian illite and solutions of MgCl2 and CaCl2 were studied by Olson and Mitronovas (1962). The results of their compression studies of illite mixed with different solutions of MgCl2 are shown in figure 10: these results apply also to CaCl2 solutions, as the effects of calcium seem to be very similar to those of magnesium. The experimnts showed the greatest resistance to compression at MgCl2 concentration near 10-2 N. The other four curves in figure 10A show a decrease in void ratio with decreasing concentration. The effects of different electrolyte concentrations seem to disappear at the maximum pressure of about 30 kg per cm2. The rebound curves for all concentrations are essentially identical. The observed decrease in void ratio with decreasing J electrolyte concentration is contrary to the predictions ji of double-layer theory (compare fig. 10A, B). This !, reversal corresponds to the behavior of coarse-grained illite in NaCl solutions (fig. 8B, O) and can be explained in terms of the same model of particle rearrangement and flocculation. Olson and Mitronovas (1962, p. 193-194) did not believe that the influence of electrolyte content on the void ratios of these illites was especially significant: they found that they could produce the same degree of variation in void ratio by varying other factors such as particle arrangement and initial water content. All these observations on the influence of electrolytes and electrolyte concentration were made on simple systems—mixtures of monomineralic clays with solutions of a single electrolyte, mixtures in which the cation of the electrolyte was the same as the cation adsorbed on the clay-mineral surfaces. In them one can find only suggestions of what might be the influence of multiple-electrolyte solutions on multimineralic clays or of what one might expect in mixtures in which one cation predominates in the pore solution and another cation predominates in the assemblage adsorbed on the particle surfaces. PRESSURE, IN KILOGRAMS PER SQUARE CENTIMETER Figure 10.—Influence of MgCla concentration on relation between void ratio and pressure in <2.0-mlcron fractions of lUlte. After Olson and Mitronovas (1962, p. 195, 197). A, Experimental; B, predicted from double-layer theory.REMOVAL OF WATER AND REARRANGEMENT OF PARTICLES DURING COMPACTION Bll EXCHANGEABLE CATIONS Another approach to understanding the chemical influences on clay compaction is to compare the behavior of clays whose exchange positions are saturated with different ions. Most of the experimental work done so far has tested the effects of different inorganic cations. Very little is known of the influence of adsorbed anions on the relation between water and pressure in clays. Likewise, except for a few compression experiments on clays mixed with organic liquids (mostly alcohols— see Jimenez Salas and Serratosa, 1953, p. 196-198; Waidelich, 1958), very little is known of the effects of organic ions and molecules. Because of its large exchange capacity, montmoril-lonite has been used in most of the studies of the influence of different cations. Results of three studies of some of the common cations are shown in figure 11. Montmorillonite saturated with sodium has a consistently larger void ratio at a given pressure than does montmorillonite saturated with aluminum, potassium, or calcium (or, presumably, magnesium, whose influence seems to be about the same as that of calcium). This difference is apparently related to the ability of sodium montmorillonite crystals to swell freely (fig. IB), and to the limited ability of the other montmorillonites to swell to interparticle distances greater than 9A. The difference in the void ratios at low pressures between Bolt’s experiments (fig. 11A) and the other two experiments (fig. HR, C) is related to differences in experimental conditions—Bolt began using a greater initial water content and used a finer grained montmorillonite. Thomas and Moody (1962, p. 154) also measured the water contents of montmorillonite saturated with sodium, calcium, and aluminum at pressures of 0.33 and 15 kg per cm2: their results, which are too brief to be included in the figure, are similar to those shown in figure 11C. Although Samuels’ work (fig. 11(7) suggested that differences in void ratio arising from differences in the exchangeable cations'are insignificant at pressures greater than 10 kg per cm2, Bolt’s results (fig. llA, representing Very- fine grained montmorillonite) suggested that these differences may be significant at somewhat greater pressures. The inference from Bolt’s results is supported by a study of montmorillonite-rich sediments in the San Joaquin Valley of California (Meade, 1963), which suggests that the influence of different exchangeable cations may be significant in natural sediments at pressures as great as 50 kg per cm2. Other experiments by Samuels showed that the influence of exchangeable cations on the void ratio of kaolin-ite are different from their influence on the void ratio of montmorillonite. Results of his experiments on fractionated kaolinite (80 percent finer than 1 micron, 98 percent finer than 2 microns) are given in figure 12. Comparison with figure 11 shows two differences: the influence of different cations on the void ratio of kaolinite is much less than their influence on the void ratio of montmorillonite, and the general relation between void ratio and cation valence is reversed. Because clays flocculate more readily in solutions that contain cations having PRESSURE, IN KILOGRAMS PER SQUARE CENTIMETER Figure 11.—Influence of exchangeable cations on relation between void ratio and pressure in montmorillonite. A, <0.2/14 fraction mixed with 10-3 molar chloride solutions of indicated cations. After Bolt (1956, p. 91). B, < 1.1/4 fraction mixed with hydroxide solutions (concentrations unspecified) of indicated cations. After Jimgnez Salas and Serratosa (1953, p. 194). O, Presumably unfractionated and mixed with distilled water. After Samuels (1950; cited and described by Grim, 1962, p. 255-256).B12 MECHANICS OF AQUIFER SYSTEMS PRESSURE, IN KILOGRAMS PER SQUARE CENTIMETER Figure 12.—Influence of exchangeable cations on relation between void ratio and pressure in kaolinite. After Samuels (1950 ; data also reported by Grim, 1962, p. 257). high valences, perhaps this reversal in kaolinite represents the effects of particle flocculation that were invoked above to explain the relation between void ratio and electrolyte concentration in coarse-grained illite. REMOVAL OF WATER DURING THE LATER STAGES OF COMPACTION Compared to the removal of water during the early stages of compaction, which has been studied intensively in recent years by soil scientists and foundation engineers, the removal of water during the later stages of compaction has received little specific attention. Some general observations can be made, however, mainly on the basis of experiments conducted by von Engel-hardt and Gaida (1963) and by Van Olphen (1963). Of the factors that seem to influence the amount of water held in clayey sediments under low pressures, the j clay-mineral composition and particle size also seem to be effective at higher pressures. Apparently, the amount of surface area available for water sorption is a major governing factor over the entire range of pressures to which natural clayey sediments are subjected. Electrolyte concentration and exchangeable cations, on the other hand, do not seem to influence the relation between water content and pressures greater than about j 30-50 kg per cm2. Experiments by von Engelhardt and Gaida (1963, p. 924-925) showed essentially no difference in the equilibrium void ratios, at any given pressure in the range from 30 to 3,100 kg per cm2, either of montmorillonite mixed with NaCl solutions, CaCl2 solutions, and distilled water, or of mixtures of montmoril- lonite and NaCl solutions varying in concentration between 4.6 N and pure water. The only effect noticed was an increase in the rate of compaction—that is, the rate of water expulsion—with increasing NaCl concen- i.e. tration. Apparently the physicochemical influences of the different cation types and electrolyte concentrations do not affect the amount of water held by a clay unless the amount exceeds a certain minimum necessary to form diffuse double layers around the particles. This minimum amount seems to be aboutAlLpercent, by weight in - \ very fine-grained (<0.1 micron) sodium montmorillonite; it should be somewhat less in coarser grained and more silty clays. When overburden loads have re- i duced the amount of water in a clayey sediment below this minimum, the forces that must be overcome to compact the sediment further are more conveniently thought of as forces of hydration—the attractions between the clay surfaces and water or between cations and water—rather than as forces of repulsion or attraction between particles. The energies involved in the later stages of water expulsion have been estimated from measurements of the temperatures and negative water-vapor pressures required to remove the last few molecular layers of water from clays. From published data on the desorption of montmorillonites in response to decreasing water-vapor pressure, Van Olphen (1963, p. 182) estimated that the work required to remove the second and last layers of adsorbed water from calcium-saturated montmorillonite surfaces is equivalent to compacting pressures on the order of 2400 and 5200 kg per cm2, respectively. These estimates are only approximate, but they indicate the enormity of the pressures required to squeeze the last increments of water from clayey sediments. Furthermore, these estimates are minimum values because they assume a parallel orientation of montmorillonite particles normal to the compacting stress—that is, they assume that the full load is borne by the water and that no load is borne by the solid particles. In nature, however, the particles probably will not lie in completely parallel positions but will touch one another at points of contact through which some of the load may be supported. Adsorbed water can be removed from clay surfaces at temperatures that are fairly low in contrast to the large pressures required. Figure 13 shows pressure-temperature curves for the loss of the last layer of adsorbed water from montmorillonite surfaces at low water-vapor pressures as determined by Crowley and Roy (1959). Although the temperatures necessary to dehydrate the montmorillonites vary with the composition of the coordinated mineral lattice and with the exchangeable cations, they change only slightly with in-REMOVAL OF WATER AND REARRANGEMENT OF PARTICLES DURING COMPACTION B13 Figure 13.—Pressure-temperature curves for dehydration reactions of montmorillonite minerals saturated with sodium, calcium, and magnesium. After Crowley and Roy (1959, p. 19). Mont-morillonite represented by solid lines ; saponite by dashed lines. creasing water-vapor pressure. If one considers the range of temperatures and pressures to which most natural sediments are subjected, temperature might be as significant a factor as pressure in removing the last increments of water from clays. The combined influences of pressure arid/ temperature were assessed by Van Olphen (1963, p. 183-186*) in experiments on the removal of the last cwe"molecular layers of water from a vermiculite clay. From the desorption of the vermiculite with decreasing water-vapor pressure at 25°C, he estimated (and his estimates were partly verified by X-ray measurements made during compression of the vermiculite to 2,000 kg per cm2) that the work involved in removing the second and last layers of water was equivalent to compacting pressures of 1,200 and 5,000 kg per cm2, respectively. From a desorption experiment at a higher temperature, 50° C, he estimated the same two compacting pressures at 640 and 4,300 kg per cm2. That is, an increase in temperature caused a noticeable decrease in the amount of pressure energy required to dehydrate the clay. The removal of water during the late stages of the compaction of clayey sediments needs much more study—not only in terms of pressure and temperature, but also taking into account and assessing the significance of such factors as particle sizes, clay-mineral composition, and salinity. FABRIC OF CLAYS AND ITS CHANGES UNDER PRESSURE The discussion of the fabric of clayey sediments is in three steps. First discussed are some of the factors other than pressure that influence the arrangement of clay-mineral particles. Then follows a summary of the available information on the fabric of uncompacted natural sediments and, finally, a summary of experi- Figure 14.—Idealized arrangements of clay-mineral particles in sediments. A, Flocculated, edge to face, in salt-free water. Lambe (1958a, p. 11). B, Flocculated, face to face, in salt solution. After Lambe (1958a, p. 11). C, Flocculated, e ge face. After Tan (1958, p. 87 ; 1939, p. 92). D, Preferentially oriented. E, Turbostratic.B14 MECHANICS OF AQUIFER SYSTEMS mental and field observations on the influence of pressure on fabric. Some of the more probable arrangements of platy clay-mineral particles in sediments are illustrated in figure 14. Schofield and Samson (1954, p. 142-143) and Lambe (1958a, p. 11) inferred the two types of flocculation shown in figure 14.4, 5 from considerations of interparticle forces. In concentrated electrolyte solutions, the net force between particles may be attraction, resulting in a flocculated arrangement as shown in figure 14.5. In electrolyte-deficient water, the principal attractive forces may be between the negatively charged basal surfaces and the positively charged particle edges, resulting in an edge-to-face arrangement as shown in figure 14.4. A three-dimensional model of edge-to-face arrangement as visualized by Tan (1958, p. 87; 1959, p. 92) is shown in figure 145. Preferred orientation of clay particles is represented in figure 145. “Turbostratic” arrangement (name suggested by Ayl-more and Quirk, 1960) is illustrated in figure 14E. It consists of domains—also called “tactoids,” “packets,” or “clusters”—of clay sheets within which the preferred orientation is nearly perfect and between which the orientation may be entirely random. The sequence A-B-D in figure 14 represents qualitatively a progression from random orientation to preferred orientation of particles. FACTORS, OTHER THAN PRESSURE, THAT INFLUENCE THE ARRANGEMENT OF CLAY PARTICLES Which of the factors that constitute a sedimentary environment might influence the arrangement of particles in a clayey sediment ? On the basis of work published through 1962, the following chemical factors seem to be significant: electrolyte concentration, types of associated cations and anions, acidity or alkalinity, and associated organic matter. Mechanical factors of particle deposition also seem to be significant, but they have received less attention than have the chemical influences. The available information on the relation between these factors and clay fabric is limited. Most of it is based on experiments in which the influence of individual factors has been isolated for detailed scrutiny; the combined influence of all factors in complex natural sediments is yet to be evaluated. Furthermore, most of these experiments recorded the influence of various factors at atmospheric pressure and only provided indirect suggestions of the influence that the factors might have in sediments under overburden loads. And, finally, the arrangements of particles in most of these experiments was inferred indirectly from observations of sedimentation volume and from the tendencies of the clays to aggregate or disperse in different chemical solutions. In very few of these experiments has the fabric been measumd^directly by X-ray, optical, or other means. V ELECTROLYTE CONCENTRATION Electrolyte concentration seems to have different effects on the fabrics of different clay minerals. It in-') fluences illite and kaolinite in one way, montmorillonite in another. Eosenqvist (1955, p. 53-62) experimented with the sedimentation of 10-percent suspensions of illite in NaCl solutions ranging in concentration between 0.002 and 0.5 N and found that the equilibrium volume of settled-out sediment increased with increasing concentration of NaCl. Similar results were obtained by Hsi and Clifton (1962, p. 272) in their experiments with 1- to 2-percent suspensions of kaolinite and metahalloy-site that had flocculated in solutions of NaCl, CaCl2, FeCl2, and A1C13 ranging in concentration from 0.0003 to 0.02 N. If one assumes that the volume of the sediment reflects the degree of disorder of the particle arrangement (random orientation of the particles with regard to each other), these results suggest that the tendency toward random orientation of illite and kaolinite particles is a direct function of the electrolyte concentration. The arrangement of particles flocculated by the more concentrated electrolytes is presumed to be as shown in figure 145. In montmorillonite, on the other hand, the relation between sedimentation volume and electrolyte concentration seems to be either inverse or nonexistent, depending on the cation involved. Hofmann and Haus-dorf (1945) experimented with 0.4- to 4.0-percent suspensions of montmorillonite in NaCl and KC1 solutions ranging in concentration from 0.004 to 2.0 N and found that the equilibrium volume of the sediment that settled out decreased with increasing electrolyte concentration. In CaCl2 and MgCl2 solutions, the sedimentation volume and interparticle distance (9-10 A) remained essentially constant at all concentrations between 0.004 N and 2.0 N. These observations are similar to those cited in the discussion of the influence of different electrolytes on the removal of water from montmorillonites under low pressures (figs. 6, 7, 9) and are perhaps best explained in the same terms—conformity or lack of conformity with the predictions of the double-layer theory. The spatial arrangement of montmorillonite particles in dilute NaCl solutions—if it is in fact a function of the double-layer repulsion between particles—should be similar to the arrangement illustrated in figure 145. That is, the particles are probably dispersed in the solution in an array that approaches parallel orientation, the interparticle distance varying with electrolyte concentration as shown in figure 75. Because the sedimentation volume and interparticle distance of mont-r REMOVAL OF WATER AND REARRANGEMENT OF PARTICLES DURING COMPACTION morillonite do not vary with the concentration of CaCl2 and MgCl2, the arrangement of particles in these solutions probably is not a salt-flocculated arrangement but something similar to the collection of parallel aggregates illustrated in figure 14E. These interpretations of the influence of electrolyte concentration on clay fabric are based on several assumptions—different assumptions, moreover, for mont-morillonite and for the other clay minerals—and should be regarded as tentative. The spatial arrangement of clay minerals in different solutions needs to be studied by some means more direct than inference from the sedimentation volume. CATIONS AND ANIONS In the experiments of Hsi and Clifton (1962) on the flocculation of kaolinite and halloysite in solutions of NaCl, CaCl2, and A1C13, the volumes of the settled-out suspensions in the different electrolytes increased in the order Na+1, Ca+2, AT3. This increase suggests that the higher valence cations are associated with a more random particle arrangement; the lower valence cations, with a greater degree of preferred orientation. The suggestion is supported by Samuels’ observations on kaolinite under pressure (fig. 12) but is contradicted by the observed influence of cations on the void ratio of montmorillonite under pressure (fig. 11). Apparently, as is suggested by the experiments on electrolyte concentration, the different cations have a different influence on the different clay minerals. Properties of the cation other than the valence also seem to influence the settling volume, as shown by experiments of Rosenqvist (1955, p. 59; 1959, p. 40) on illites sedimented in 0.75 N concentrations of NaCl and KC1. He reported that the volume of the sediment that settled in the KC1 solution was about 30 percent greater than the volume that settled in the NaCl solution. Experiments with illites that settled in 0.75 N solutions of LiCl (smaller settling volume than in NaCl) and CsCl (greater settling volume than in KC1) indicate further that valence is not the only cation property that influences the arrangement of particles. Lambe (1958a, p. 7,9) suggested, on the basis of doublelayer considerations, that this influence on the settling volume is an inverse effect of the size of the hydrated ion, which seems to decrease in the order Li > Na > K > Cs. That is, the smaller hydrated ions allow the illite particles to approach one another more closely, to flocculate more readily, and to orient more randomly. The influence of different anions on the arrangement of clay particles is essentially unknown. Hsi and Clifton (1962) studied the influence of NaCl, Na2S04, and Na2C03 on the flocculation of kaolinite and halloysite, and Longenecker (1960, p. 188) measured the B15 settling volumes of a montmorillonite-rich clay in different concentrations of NaCl and Na2S04. Except for the observation that the montmorillonite-rich clay has a larger equilibrim sedimentation volume in Na2S04 solutions than in NaCl solutions of equivalent normality, little more can be said than that the anions are likely to influencethe fabric. IGd ACIDITY Schofield and Samson (1953, 1954) found an apparent relation between acidity and flocculation in 10-percent suspensions of kaolinite. Purified sodium kaolinite flocculated spontaneously in distilled water but deflocculated on addition of small amounts of NaOH. Measurements of the adsorption and desorption of chloride ions by the kaolinite led Schofield and Samson to conclude (1) that the flocculation resulted from attractions between positively charged particle edges and negatively charged particle faces (fig. 14A), and (2) that the positive edge charges (and hence the tendency to flocculate) were strongest under acid conditions, diminished with increasing pH, and eventually became negative. Sisler (1960, p. 192) measured the sedimenation volume of samples of mud from the bottom of Lake Mead after he allowed them to settle in HC1 or NaOH solutions adjusted to a series of pH values between 2 and 12. Judging from Rolfe’s (1957) analyses of sediments from the same part of Lake Mead (Boulder Basin), the mineral constituents of the mud are probably quartz, illite, and kaolinite, plus minor amounts of montmorillonite and feldspar. The largest sedimentation vol-v ume—1 percent greater than the volume at pH 7.2 f (approximately the natural pH)—was observed at pH i. 2. The smallest volume—22 percent less than at pH 7.2—was observed at pH 10. These results suggest that the tendency for clays to assume an open flocculated arrangement is substantially less at strongly alkaline pH than at neutral or strongly acid pH. ORGANIC MATTER Organic matter probably influences the arrangement of clay particles in sediments. Studies by Bloomfield (1956), Lawson and Keilen (1951), and Sbderblom (1960), among others, indicated that kaolinite or illite can be flocculated or deflocculated by solutions of some of the organic materials that are likely to be associated with sediments—aqueous extracts from tree leaves, bark, wood pulp, or peat—but these studies contain no direct indications of the arrangement of particles. Ingram (1953) observed a direct correlation between the presence of organic material and the preferred orientation of clay-mineral particles in 50 clayey rocks from Colorado, Iowa, and Wisconsin. The rocks ranged in age from Ordovician to Eocene. IngramB16 MECHANICS OF AQUIFER SYSTEMS made his observations from thin sections of the rocks. He noted (p. 873-875) that organic stain was associated with clays that showed preferred orientation and that it was absent from clays in which the orientation was random. In one rock sample, this relation was expressed in alternate organic and nonorganic clayey layers. Organic matter also seemed to influence the fabric of the clay minerals when the rocks were disaggregated, suspended, and then sedimented from suspensions by adding NaCl. Clay minerals from rocks that contained organic material settled out of suspension in a pronounced parallel arrangement, whereas the arrangement of sedimented particles from the nonorganic rocks was mostly random. PHYSICAL CONDITIONS OF DEPOSITION Void ratio After first centri- After drying and Exchangeable cation fuging recentrifuging Sodium or potassium_____________ ~40 ~40 Calcium or magnesium____________ 18-25 6-8 These results suggested that drying irreversibly increases the size of the domains into which calcium and magnesium montmorillonites are aggregated—an effect similar to the irreversible compression of calcium montmorillonites that was observed by Blackmore and Miller (1961) and is represented in figure 9. The wet volume (and presumably the fabric) of sodium and potassium montmorillonites, en the other hand, does not seem to be influenced significantly by intermediate drying. FABRIC OF UNCOMPACTED NATURAL CLAYS In addition to being influenced by chemical factors, the fabric of a clayey sediment must also be affected by physical and mechanical factors involved in deposition : rate of deposition, state of agitation or quiescence of the water in which the sediment is deposited, particle-size distribution and concentration of the sediment being deposited, and drying of the sediment between deposition and burial. The concentration of the sediment in the depositing medium, for example, seems to influence the degree to which the particles assume whatever equilibrium fabric is favored by the existing chemical conditions. Rait-burd (1960, p. 110) reported that, whereas kaolinite particles settled out of 2- to 5-percent suspensions to form a preferentially-oriented fabric (measured by X-ray diffraction), no predominant orientation of particles was observed in kaolinite that had settled out of a 50-percent (by weight?) suspension. In the experiments of Olson and Mitronovas (1962, p. 192), a calcium illite sedimented from a very dilute suspension maintained a larger void ratio under pressures in the range from 0 to 10 kg per cm2 than did one sedimented from a 34-percent (by weight) suspension. This result suggests that the illite sedimented from the more dilute suspension assumed a more open flocculated arrangement, which influenced its response to pressure. Results of experiments by Isaac Barshad (oral communication, 1963) suggested that drying may have irreversible effects on the fabric of some montmorillonites. In his experiments, well-dispersed montmorillonites were first saturated with sodium, potassium, calcium, or magnesium and sedimented by centrifuging. The montmorillonites then were dried, dispersed again mechanically, and sedimented once more by centrifuging under the same conditions as before. The amounts of water retained by the sedimented clays are expressed volumetrically in the following void ratios: Most of the specific information on the fabric of recently deposited and unconsolidated clays comes from the electron micrographs of illitic clays from Scandinavia made by Rosenqvist (1958, p. 441; 1959, p. 39; 1962, pi. 5). In the marine clays that he examined, Rosenqvist (1959, p. 38) found an openwork arrangement of particles dominated by contacts between corners and planes, corresponding “to an astonishing degree” with the arrangement as visualized by Tan (fig. 14(7). Rosenqvist reported further (1962, p. 25) that, in about a hundred stereoscopic electron micrographs of unconsolidated and unweathered marine clays from Scandinavia, he had “* * * never observed anything resembling a domain structure.” In fresh-water clays, on the other hand, he has found a greater degree of parallel orientation between clay particles—in arrangements approaching that shown in figure 14Z>. Rosenqvist related the difference between the fabrics of marine and fresh-water clays to the flocculating effect of the electrolytes in sea water. In fresh water, the illite particles apparently did not aggregate readily but settled individually out of suspension into more efficiently packed arrangements. Rosenqvist’s observations on the different fabrics of marine and fresh-water clays are partly corroborated by observations made in other parts of the world in sediments buried under a few tens of feet of overburden. At these depths, presumably, the fabric reflects its original state more than it reflects the influence of pressure. Raitburd (1960, p. 113, 115) reported completely random orientation—measured by X-ray diffraction—of illite and kaolinite particles in a Quaternary marine clay from the northeastern part of the Black Sea. Mitchell (1956), from his thin-section study of 14 marine and nonmarine clays from North America, reported generally better formed preferred orientation in the nonmarine clays. Wu (1958), on theREMOVAL OF WATER AND REARRANGEMENT OF PARTICLES DURING COMPACTION B17 other hand, found different degrees of random and preferred orientation in glacial-lake clays from the southern Great Lakes area that could not be related to different types or concentrations of ions in the interstitial waters. An indirect indication of the conditions under which clays might be flocculated at fairly low salinities is given by evidence from studies of the sediments transported by the Colorado River and deposited in Lake Mead. Sherman (1953, p. 396-400) compared the settling velocities of fine-grained lake sediments in the lake water with those of the same sediments in solutions of a dispersing agent and found that many of the particles in nature were aggregated into floccules. Howard (1960, p. 104) found the same type of floccules suspended in the waters of the Colorado River at Grand Canyon, 145 river miles upstream from Lake Mead. Sherman also compared the pore volumes of natural lake sediments with those of sediments that had been dispersed artificially. The natural sediments having median diameters of about 1 micron had an average void ratio of about 6 (curve I, fig. 3A); sediment of the same size that had been dispersed with a chemical agent and allowed to settle out of suspension had a void ratio of about 2. Although these observations give no indication of the degree of orientation, they suggest that the arrangement of fine particles transported by the Colorado River and deposited on the bottom of Lake Mead might be less preferred than are the orientations observed in Scandinavian lakes by Rosenqvist. The clay minerals in Lake Mead and presumably in the river sediment are illite, montmorillonite, and kaolinite, in proportions that vary from one part of the lake to another (Rolfe, 1957). The pH of slurries of the lake sediment ranges from 7.0 to 7.6 (Rolfe, 1957, p. 380). The principal ions dissolved in the lake and river water are Na+1, Ca+2, SO>, and HCO3'1, and the total salinity usually ranges between about 300 and 1200 parts per million (Howard, 1960, p. 108). Expressed as normality, this concentration range is about 0.005 to 0.02 N, which was the range of concentrations of the sodium and calcium salts that was sufficient to flocculate kaolinite minerals in some, but not in all, of the experiments of Hsi and Clifton (1962). In addition to most of the fabrics observed in clayey sediments, clayey soils exhibit some peculiar particle arrangements of their own. Oriented coatings on silt and sand grains, oriented films on the walls of cracks or pores, and domainlike aggregates seem to be formed in soils by elutriation, repetitive drying, and leaching processes. For details of these processes and fabrics, see Brewer (1956), Minashina (1959), and Rosenqvist (1962, p. 23-25). INFLUENCE OF PRESSURE ON THE FABRIC OF CLAYS The removal of water under the influence of pressure implies that the solid particles in a clayey sediment must move closer together into a more efficiently packed arrangement. At least two special arrangements—preferred orientation and turbostratic orientation (fig. 14Z>, E)—may be formed during compaction. These two fabrics, and particularly the preferred orientation, have received most of the emphasis in compaction studies. One should keep in mind, however, that other responses to pressure such as the bending and crumpling of clay particles are also possible. FABRIC OF CLAYS COMPRESSED IN THE LABORATORY Laboratory experiments on the rearrangement of particles in water-saturated clays under uniaxial pressure can be divided into two groups: those in which the sides of the clay are not confined but are allowed to spread freely, and those in which the sides of the clay are rigidly confined. Neither condition is an exact replication of the distribution of pressures during natural compaction, but the laterally confined experiments probably represent nature more closely. UNCONFINED COMPRESSION Preferred orientation is produced readily during unconfined compression. Aggregates of Georgia kaolinite were subjected to uniaxial compressions of 0.22 and 0.55 kg per cm2 by Buessem and Nagy (1954). X-ray powder photographs showed that the orientation of kaolinite flakes in the uncompressed aggregates was random and that compression increased the orientation of the flakes normal to the direction of applied load. Williamson (1947) produced preferred orientation by repeatedly dropping a ball of illite-kaolinite clay onto a glass plate from a height of about 1 foot; he produced the sqme orientation by squeezing a similar ball of clay between parallel glass plates in a hand press. Raitburd (1958, p. 791) compressed a cylinder of kaolinite paste between glass plates to one-third its original thickness and produced a clearly detectable (by X-ray diffraction) preferred orientation. Popov (1944) observed preferred orientation in fluid montmorillonite pastes (water, 40-70 percent by weight) that he produced by squeezing the pastes between glass slides. The combination of compression and lateral flow apparently favors the formation of preferred orientation. COMPRESSION OF LATERALLY CONFINED CLAYS Some clays form preferred orientation under low pressure when they are laterally confined. Mitchell (1956) mixed an illite-quartz powder with sea water, placed it in a rigid-walled cylinder, and subjected it to a uniaxial load of 4 kg per cm2. A thin section of the compressed clay showed that the illite particles, initiallyB18 MECHANICS OF AQUIFER SYSTEMS in random orientation, were in preferred orientation in the plane normal to the compressive stress. He also studied the effects of uniaxial pressures of 2 kg per cm2 in a group of 14 marine and nonmarine clays from North America. In the marine clays, in which the predominant clay mineral was illite, the compression caused an increase in the degree of preferred orientation over large areas as well as within small domainlike aggregates (generally less than 0.5 mm in diameter) . In the nonmarine clays, most of which contained substantial proportions of montmorillonite, the results of the compression were not consistent; the degree of preferred orientation was increased in some samples and decreased in others. Domains also seem to form in some clays under low to moderate pressures. From measurements of the sharpness of X-ray reflections from compressed calcium montmorillonite, Blackmore and Miller (1961, p. 171) inferred that the number of montmorillonite unit 10-A thick sheets per domain increased progressively with pressure, ranging from about 5 unit sheets at 0.5 kg per cm2 to nearly 8 unit sheets at 90 kg per cm2. The process seemed to be irreversible; that is, the sheets in the domains did not seem to dissociate when the pressure was released. Preferred orientation seems to form readily under great pressures applied in laboratory experiments. Engelhardt and Gaida (1963, p. 925-926) observed an increase in the degree of preferred orientation of montmorillonite and kaolinite particles with increasing pressures between 80 and 800 kg per cm2. Olson (1962, p. 34, 37) produced an extreme degree of preferred orientation by cyclically compressing and decompressing calcium illite 15 times at pressures between 4.4 and 4,500 kg per cm2. Eaitburd (1960, p. 111-113) made a series of uniaxial compression experiments on pastes of different clay minerals—presumably kaolinite and montmorillonite. He did not state the range of pressures used in these experiments, but one can infer from other experiments described in his paper that the pressures may have been as great as 5,000 or 10,000 kg per cm2. When thin pastes (1.5 mm) were compressed, a homogeneous orientation formed normal to the compressive stress. When thicker pastes (2 cm) were compressed, orientation formed in two directions: one normal to the compression, and the other along slip planes at about 45° to the direction of compressive /stress. The particle orientation in all these high-pressure experiments was measured by X-ray diffraction. Evidence of bending and crumpling of fine-grained clay particles under pressure is scarce. Tan (1959, p. 93) stated that montmorillonite particles maybe broken under heavy local stress concentrations, but he did not cite evidence or give an idea of the magnitude of pressures he had in mind. Norton and Johnson (1944) said that kaolinite particles averaging 0.32 micron in diameter and 0.04 micron in thickness were distorted by pressures as low as 40 kg per cm2; but again no direct evidence was cited. INFLUENCE OF ELECTROLYTE CONCENTRATION UNDER PRESSURE Von Engelhardt and Gaida (1963, p. 926) used X-ray diffraction to measure the bulk degree of preferred orientation of montmorillonite compressed under 800 kg per cm2 in three solutions of NaCl ranging in concentration from 0.16 to 1.1 N. They found an inverse relation between the concentration of NaCl and the degree of preferred orientation at right angles to the compacting pressure. They found also that, whereas the void ratio remained constant at about 0.5 in all three samples, the permeability (as measured by the rate of compaction) increased with increasing NaCl concentration. These observations can be explained by a greater degree of preferred particle arrangement (fig. 14Z>) at smaller concentrations and by a more turbostratic arrangement (fig. 14E) at larger concentrations. Figures 14Z> and 14E are drawn with approximately equal void ratios and show the effect of fabric on permeability— water moves more readily through large pore spaces. In addition to providing tho most satisfactory model to explain the above observations, a turbostratic fabric seems reasonable in a mixture of montmorillonite and 1.1 N NaCl when one recollects studies that were discussed earlier in this review. The experiments illustrated in figure 7B indicated that, at NaCl concentrations greater than about 0.3 N, montmorillonites do not expand readily to interparticle spacings greater than 9 A. Montmorillonites mixed with calcium electrolytes do not expand readily beyond interparticle spacings of 9 A at any concentration. Figure 9 and other observations suggest that particles of calcium-saturated montmorillonite under load are compressed irreversibly into domains. Perhaps montmorillonite in contact with concentrated NaCl solutions behaves in the same way. FABRIC OF NATURALLY COMPACTED CLAYEY SEDIMENTS Only a few detailed studies have been made of the orientation of clay-mineral particles in shales, and, with the exception of one study, there is little evidence to support the formation of oriented fabrics—either preferred or turbostratic—during natural compaction. In a recent study of a 2,000-foot-thick section of unconsolidated nonmarine sediments (Meade, 1961b), X-ray diffraction measurements showed no progressive increase of the degree of orientation of montmorilloniteREMOVAL OF WATER AND REARRANGEMENT OF PARTICLES DURING COMPACTION B19 particles parallel to the bedding with increasing depth (fig. 15). The only significant preferred orientation was found in a fresh-water-lake deposit, which suggests that the fabric might not have been produced by compacting pressures but by the slow settling of individual clay particles in the still waters of the lake. In the rest of the sediments, mainly alluvial-fan and flood-plain deposits, no preferred orientation seems to have formed either during deposition or as a result of compaction. If one considers that von Engelhardt and Gaida (1963) were able in the laboratory to produce an increase in the degree of preferred orientation of pure montmorillonite with increasing pressures between 80 and 800 kg per cm2, the lack of preferred orientation in the alluvial sediments represented in figure 15 may be due to one or more of the following reasons: 1. Perhaps not enough pressure has been exerted on the natural sediments to cause any discernible preferred orientation in the montmorillonite; the maximum effective load to which these sediments have been subjected is 60 to 70 kg per cm2. 2i Perhaps the presence of silt and sand particles in-V jyibits the formation of preferred orientation in the natural sediment. 3. Perhaps the montmorillonites have been compressed into domains (which are not detectible by the X-ray method) rather than into a homogeneous parallel fabric. MONTMORILLONITE ORIENTATION RATIO 1 2 3 _I____I____I Ui W//0//A O bUO- • cc (f) § 1000J < -J £ o X \— Q_ LkJ Q 500 1000- 1500 1 2 _i____i____i 500- 1000- 1500- 1 2 3 _i____i----1 Figure 15.—Horizontal preferred orientation of montmoriilon-ite in unconsolidated clayey sediments from three core holes In San Joaquin Valley, Calif. Montmorillonite orientation ratio computed from X-ray-diffraction peak heights (explained by Meade, 1961a) : the larger the ratio, the greater the degree of preferred orientation parallel to the bedding. Ratio near 1.0 signifies random orientation. Lacustrine desposits cross-hatched. The formation of domains is a likely possibility for two reasons: (1) The principal exchangeable cation is calcium, and (2) domainlike aggregates that were deposited as such (shale fragments and other aggregates) are available for nucleation of further material. Kaarsberg (1959) found, in flat-lying shales buried under 2,700 feet or more of overburden in several parts of the United States and Canada, that the preferred orientation of illite increased with the depth of burial. Illite is the predominant clay mineral in all the natural sediments he studied. Many of them contain chlorite; only a few have even minor amounts of montmorillonite. He used X-ray diffraction and sound velocities to measure preferred orientation, and he used dry bulk density as a measure of compaction. A sample of his measurements is tabulated below. Using a method described elsewhere (Meade, 1961a), I computed the “orientation ratio” from X-ray diffraction measurements that Kaarsberg had plotted in a graph on page 469 of his report. The larger the ratio, the greater the degree of preferred orientation of illite particles parallel to the bedding. Other X-ray diffraction measurements plus sound velocities support Kaarsberg’s conclusion (p. 470-471) “* * * that the degree of preferred orientation of the basal planes of the illite particles parallel to the bedding increases with compaction.” Results of Kaarsberg’s study (1959) [Orlentaton ratio computed by Meade] Present ■k depth below Bulk density Orientation Type of sample surface (ft) (g per cm*) ratio Recent clay 0 1. 9 1. 5 Cretaceous shale . . _ 4,340 2. 4 2. 8 Do . . 5, 136 2. 5 2. 2 Do . - 6,776 2. 6 3. 2 Do 9,120 2. 7 5. 0 Slate.. _ - 2. 9 32. 0 In many older shales, however, increasing degree of preferred orientation with increasing depth of burial has not been observed. White (1961, p. 564), for example, stated that the fissility (which is presumably a reflection of fabric) of Paleozoic shales in Illinois does not vary systematically with the depth of burial. In the same group of Paleozoic shales, Grim and others (1957) noted a relation between preferred orientation of clay minerals and particle size; preferred orientation was better formed in fine-grained shales (in which most of the particles were smaller than 2 microns) than in coaser grained shales that contained appreciable amounts of nonclay mineral grains. The influence of natural compaction on the fabric of clayey sediments apparently needs to be evaluated in conjunction with other likely influential factors.B20 MECHANICS OF AQUIFER SYSTEMS SUMMARY The removal of water and the rearrangement of particles in clayey sediments under pressure are complex functions of particle size, clay minerals and associated ions, interstitial electrolyte concentration, acidity, temperature, and the' arrangement of particles at the onset of compaction. Other factors such as associated organic material may influence the compaction processes, but very little is known about them. Particle size is perhaps the most significant factor— not only in its consistently inverse relation to pore volume under a wide range of pressures, but also in the sense that it influences the nature and degree of the influence that the other factors have on the progress of compaction. In very fine grained clays, which have large areas of particle surface available to interact with interstitial water and dissolved ions, the influence of electrolytes and exchangeable ions can he expressed in terms of the forces of repulsion or attraction related to the particle surfaces. In coarser grained clays, on the other hand, the surface forces become less significant, and one must give more consideration to the rearrangement of particles in response to gravitational forces associated with the particle mass. The different influences of cation type and electrolyte concentration under low overburden pressures seem to be as follows: 1. In fine-grained clays (montmorillonites and fine- grained illite) : (a) In sodium solutions less concentrated than about 0.3 N, the water content at equilibrium (and perhaps the degree of preferred orientation of the particles?) increases with decreasing concentration. (b) In sodium solutions more concentrated than about 0.3 N or in potassium, calcium, magnesium, or aluminum electrolyte solutions, the variation of water content with electrolyte concentration is less apparent because of the tendency of the clays to aggregate irreversibly into oriented domains in which the interparticle distance does not exceed 9 A. This tendency is reinforced by overburden pressure during compaction. 2. In coarse-grained clays (kaolinite and coarse- grained illite), the water content at equilibrium and the randomness of particle orientation increase with increasing electrolyte concentration or with increasing cation valence. This relationship apparently results because the coarse clays flocculate more readily in the more concentrated solutions or in higher valence cation solutions to form openwork structures that resist the compacting effects of small overburden pressures. These observations, however, were made on singlecation, single-electrolyte, single-mineral systems and have only suggested what might be observed in more complex systems. The response of clayey sediments to compacting pressures greater than about 50 kg per cm2 seems to be influenced mainly by the particle size, clay minerals (whose influence is related mainly to their size), and temperature. Under these pressures the cation type and electrolyte concentration may influence the clay fabric, but they do not seem to influence the total amount of interstitial water held in the sediments. The main effect of increasing temperature is to reduce the amount of pressure necessary to remove the interstitial water. Although preferred and turbostratic orientations can be produced by compressing clays in the laboratory, there is little evidence to show that these fabrics are formed readily and generally during natural compaction. Mainly on the basis of experimental evidence, the following factors might seem to encourage the formation of preferred orientation under overburden loads: 1. Existence of a partly oriented fabric at the onset of compaction. If preferred orientation is already incipient in the sediment, it would seem more likely to form to a greater degree during compaction than if the particles were in some other kind of arrangement. 2. Increasing size of clay-mineral particles. Kaolinite and illite seem to be oriented more readily under pressure than is montmorillonite. 3. Decreasing concentration of interstitial electrolyte. This decrease should reduce the tendency of the coarser clays to flocculate and the tendency of the finer clays to aggregate into domains. 4. Decreasing cation valence also should reduce the tendency of the clays to flocculate or to form domains. 5. Decreasing acidity. 6. Presence of organic material. The formation under pressure of a turbostratic fabric instead of a general degree of preferred orientation might be favored by increasing electrolyte concentration and increasing cation valence. The influence of all these factors on compaction processes needs further study. Especially needed are studies of the combined influences of the factors and their relative significance under a wide variety of natural conditions.REMOVAL OF WATER AND REARRANGEMENT OF PARTICLES DURING COMPACTION B21 REFERENCES American Geological Institute, 1957, Glossary of geology and related sciences: Natl. Acad. Sci.-Natl. Research Council Pub. 501, 325 p. American Society of Civil Engineers, 1958, Glossary of terms and definitions in soil mechanics: Soil Mech. and Found. Div. Jour., Am. Soc. Civil Engineers Proc., v. 84, SM4, Paper 1826, 43 p. 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Conf. on Clays and Clay Minerals Proc., p. 343-349. ------1962, Swelling pressure of Na-montmorillonite in Nad solutions: Jour. Soil Sci. [Great Britain], v. 13, p. 98-105. Weller, J. M., 1959, Compaction of sediments: Am. Assoc. Petroleum Geologists Bull., v. 43, p. 273-310. White, W. A., 1961, Colloid phenomena in sedimentation of argillaceous rocks: Jour. Sed. Petrology, v. 31, p. 560-570. Williamson, W. O., 1947, The fabric, water-distribution, drying-shrinkage, and porosity of some shaped discs of clay: Am. Jour. Sci., v. 245, p. 645-662. Wu, T. H., 1958, Geotechnical properties of glacial lake clays: Soil Mech. and Found. Div. Jour., Am. Soc. Civil Engineers Proc., v. 84, SM3, Paper 1732, 34 p.1 11 f r i'*wr Q t 7-T PG V.447-C 7 DAY Land Subsidence in Central California GEOLOGICAL SURVEY PROFESSIONAL PAPER 497-CPetrology of Sediments Underlying Areas of Land Subsidence in Central California By ROBERT H. MEADE MECHANICS OF AQUIFER SYSTEMS GEOLOGICAL SURVEY PROFESSIONAL PAPER 497-C IVith emphasis on the petrologic characteristics that influence the compaction behavior of the sediments: particle size, clay minerals, and associated ions UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1967UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price 65 cents (paper cover)CONTENTS Abstract________________________________________________ Introduction____________________________________________ ► Purposes of report_________________________________ Collection of samples______________________________ Acknowledgments____________________________________ Sediments in the Los Banos-Kettleman City area__________ Sources of sediments_______________________________ Source criteria________________________________ Andesitic sands________________________________ r Types of deposits__________________________________ Criteria for distinguishing principal types of deposits____________________________________ Large-scale criteria______________________ Textural evidence of processes of deposition in fine-grained sediments_______________ Alluvial-fan deposits__________________________ Flood-plain deposits___________________________ Lacustrine deposits____________________________ Deltaic deposits_______________________________ Particle sizes_____________________________________ Particle-size distributions of recovered sediments__________________________________________ Spatial distribution of particle sizes_________ Relations between particle-size measures and their bearing on the depositional history of sediments___________________________________ Review of previous work___________________ Relations of average particle size to sorting and skewness_______________ CM diagrams__________________________ Interrelations of particle-size measures in cored sediments_________________________ Flood-plain sediments________________ Alluvial-fan sediments_______________ Clay minerals and associated ions__________________ Clay minerals and their assemblages____________ Sources of clay minerals_______________________ Sources of montmorillonite________________ Sources of other clay minerals____________ Total clay-mineral content of sediments________ t Ions associated with clay minerals_____________ Exchangeable cations in modern stream sediments_______________________________ Exchangeable cations in subsurface sediments_____________________________________ Sediments in the Tulare-Wasco area______________________ Source of sediments________________________________ , Types of deposits__________________________________ Marine deposits________________________________ Alluvial-fan deposits__________________________ Lacustrine and flood-plain deposits____________ Particle sizes_____________________________________ Particle sizes of nonmarine sediments__________ Particle sizes of marine sediments_____________ Page Sediments in the Tulare-Wasco area—Continued Partic'e sizes—Continued Spatial distribution of particle sizes------------- C31 Interrelations of particle-size measures------------ 32 Alluvial-fan sediments_________________________ 33 Shallow-marine sediments------------------------ 33 Clay minerals and associated ions------------------------ 34 Clay minerals and their assemblages----------------- 34 Sources of clay minerals____________________________ 34 Total clay-mineral content of sediments------------- 35 Ions associated with clay minerals__________________ 35 Distribution of exchangeable cations______- 35 Sulfate in the marine siltstones________________ 37 Sediments in the Santa Clara Valley_____________________- 38 Source of sediments______________________________________ 38 Types of deposits________________________________________ 38 Modern alluvial sediments and soils----------------- 39 Older alluvial sediments and soils.----------------- 40 Absence of estuarine deposits----------------------- 40 Rates of deposition_________________________________ 41 Particle sizes___________________________________________ 41 Spatial distribution of particle sizes-------------- 42 Interrelations of particle-size measures------------ 43 Clay minerals and associated ions________________________ 43 Clay-mineral assemblage_____________________________ 43 Total clay-mineral content of sediments------- 44 Exchangeable cations________________________________ 44 Clay minerals in the Arvin-Maricopa area______________________ 45 Summary of results of petrologic study________________________ 46 Determination and description of particle sizes--------------- 48 Sampling and particle-size analysis______________________ 48 Description of particle sizes____________________________ 49 SkqJQD^, or Bowley’s measure of skewness----------------- 50 Tables of particle-size-distribution data and derived measures______________________________________________ 50 Analytical procedures and tabulated results of clay- mineral study______________________________________________ 65 Clay-mineral separation__________________________________ 65 X-ray diffraction________________________________________ 66 Identification of clay minerals__________________________ 67 Montmorillonite and vermiculite_____________________ 67 Mixed-layer montmorillonite-illite__________________ 68 Illite______________________________________________ 68 Low-grade illite-montmorillonite mixture____________ 69 Chlorite____________________________________________ 69 Kaolinite-type mineral______________________________ 69 Minor chloritic minerals____________________________ 71 Relative proportions of mineral species__________________ 71 Exchangeable-cation and soluble-anion analyses_____ 71 Measurement of pH________________________________________ 72 Tables of data on clay minerals and chemical analyses_______________________________________________ 72 References____________________________________________________ 78 Index_______________________________________________________ 81 Page Cl 1 2 2 3 3 5 5 5 5 6 6 6 8 9 9 9 9 9 12 13 14 14 14 16 17 17 18 18 18 18 22 22 22 23 23 24 24 24 24 27 27 27 29 29 inIV CONTENTS ILLUSTRATIONS Page Figure 1. Map showing principal areas of land subsidence_____________________________________________ Cl 2. Map of Los Banos-Kettleman City area showing location of core holes______________________ 4 3. Diagrams of principal sources and types of deposits represented by sediments cored in the Los Banos-Kettleman City area_________________________________________________________ 6 4. Diagrammatic cross sections of clay aggregates showing progressive stages of development from undisturbed clay layers____________________________________________________________ 8 5. Diagrams of sand-silt-clay percentages of sediments from Mcndota, Cantua Creek, and Huron cores______________________________________________________________________________ 10 6. Graphs showing measures of average size, sorting, and skewness in sediments from Mcndota, Cantua Creek, and Huron cores___________________________________________________ 11 7. Diagrams showing variations in particle size with depth, Los Banos-Kettleman City area 13 8. Graphs showing relation of median diameter to sorting and skewness in shallow marine sediments________________________________________________________________________________ 14 9. Diagram of CM patterns____________________________________________________________________ 15 10. Diagrammatic particle-size-distribution curves (probability scale) of sediments deposited by tractive currents and turbidity currents______________________________________________ 15 11. Diagram showing CM patterns of modem surficial alluvial-fan deposits, Los Banos- Kettleman City area______________________________________________________________________ 16 12. Graphs of median diameter against coarsest percentile, sorting, and skewness in flood- plain and alluvial-fan sediments, Los Banos-Kettleman City area_________________________ 16 13. Diagrams of clay minerals in cored sediments, Los Banos-Kettleman City area-------------- 19 14. Map showing location of sampling sites for clay minerals in Recent surface alluvial sedi- ments, Los Banos-Kettleman City area_____________________________________________________ 20 15. Diagrams of cations adsorbed by clay minerals in principal streams and cores, Los Banos- Kettleman City area______________________________________________________________________ 25 16. Map of Tulare-Wasco area showing locations of core holes_________________________________ 26 17. Diagrams of source and principal types of deposits represented by sediments cored in the Tulare-Wasco area________________________________________________________________________ 27 18. Photomicrographs of soil textures in alluvial sediment from depth of 232 feet in Richgrove core_____________________________________________________________________________________ 27 19. Diagrams of sand-silt-clay percentages of sediments cored in the Tulare-Wasco area------- 30 20. Graphs showing measures of average size, sorting, and skewness in nonmarine sediments cored in the Tulare-Wasco area___________________________________________________________ 31 21. Graphs showing measures of average size, sorting, and skewness in marine sediments from the Richgrove core_______________________________________________________________________ 31 22. Diagrams showing variations in particle size with depth, Tulare-Wasco area--------------- 32 23. Graphs of median diameter against coarsest percentile, sorting, and skewness in alluvial- fan and shallow-marine sediments, Tulare-Wasco area-------------------------------------- 33 24. Diagrams of clay minerals in cored sediments, Tulare-Wasco area-------------------------- 34 25. Diagrams of cations adsorbed by clay minerals in cored sediments, Tulare-Wasco area------ 35 26. Graphs showing relation of the proportion of adsorbed sodium to salt concentration and pH in sediments below 760 feet in the Richgrove core------------------------------------ 36 27. Graphs showing soluble salts, soluble anions, and pH of fine-grained sediments from the Richgrove core__________________________________________________________________________ 37 28. Map of Santa Clara Valley showing location of core holes--------------------------------- 39 29. Diagram of sand-silt-clay percentages of sediments cored in the Santa Clara Valley------- 42 30. Graphs showing measures of average size, sorting, and skewness in sediments cored in the Santa Clara Valley______________________,_______________________________________________ 42 31. Diagrams showing variations in particle size with depth, Santa Clara Valley______________ 43 32. Graphs of median diameter against coarsest percentile, sorting, and skewness in alluvial sediments, Santa Clara Valley___________________________________________________________ 43 33. Diagrams of clay minerals in cored sediments, Santa Clara Valley_________________________ 44 34. Map showing location of core holes and sampling sites for clay minerals in Recent surface alluvial and bay-bottom sediments, Santa Clara Valley___________________________________ 45 35. Diagrams of cations adsorbed by clay minerals in cored sediments, Santa Clara Valley_ 46 36. Map of Arvin-Maricopa area showing location of Lakcview test hole_________________________ 47 37. Diagram of clay minerals in cored sediments from Lakcview test hole______________________ 48 38. Graph showing relation between Skq^/QD^ and login Sk_____________________________________ 51 39. X-ray diffraction patterns of oriented aggregates of expanding clay minerals______________ 67 40. X-ray diffraction patterns of oriented aggregates of chlorite and kaolinite-type minerals— 70CONTENTS V TABLES Page Tabm 1. Core holes and details of coring__________________________________________________________ C3 2. Criteria for distinguishing alluvial-fan, flood-plain, lacustrine, and deltaic deposits, Los Banos-Kettleman City area________________________________________________________________ 7 3. Criteria for distinguishing conditions under which fine-grained sediments were deposited, Los Banos-Kettleman City area____________________________________________________________ 7 4. Evidence for conditions of deposition represented by sediments in Richgrove core, Tulare- Wasco area______________________________________________________________________________ 28 5. Particle-size data for sediments from Mendota, Cantua Creek, and Huron cores, Los Banos-Kettleman City area______________________________________..._._________________ 51 6. Particle-size data for selected fine-grained sediments from cores and streams, Los Banos- Kettleman City area_____________________________________________________________________ 58 7. Particle-size data for selected well-sorted sands from Mendota, Cantua Creek, and Huron cores, Los Banos-Kettleman City area____________________________________________________ 58 8. Particle-size data for cored sediments, Tulare-Wasco area________________________________ 60 9. Particle-size data for cored sediments, Santa Clara Valley__________________ 63 10. Proportions of clay minerals in two clay-size fractions of sediments from Los Banos-Kettle- man City area___________________________________________________________________________ 66 11. Clay minerals and associated ions in fine-grained sediments from cores in Los Banos- Kettleman City area_____________________________________________________________________ 73 12. Clay minerals and associated ions in surface and near-surface alluvial sediments, Los Banos-Kettleman City area_______________________________________________________________ 74 13. Clay minerals and associated ions in fine-grained sediments from cores in Tulare-Wasco area____________________________________________________________________________________ 75 14. Clay minerals and associated ions in fine-grained sediments from cores in Santa Clara Valley__________________________________________________________________________________ 76 15. Clay minerals and associated ions in fine-grained surficial sediments from Santa Clara Valley and southern San Francisco Bay--------------------------------------------------- 77 16. Partial chemical analyses of water from selected wells within about 3 miles of Sunnyvale core hole_______________________________________________________________________________ 77 17. Partial chemical analyses of water from wells within 200 yards of San Jose core hole__ 78 18. Clay minerals in fine-grained sediments from Lakeview test hole, Arvin-Maricopa area_ 781 i iMECHANICS OF AQUIFER SYSTEMS PETROLOGY OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA By Robert H. Meade ABSTRACT A diversity of particle sizes and a uniformity of clay-mineral assemblages has been shown by a study of the petrologic characteristics that influence compaction—particle sizes, clay minerals, and associated ions—in fresh-water-bearing sediments underlying areas of land subsidence related to ground-water withdrawal in central California. The sediments underlying the Los Banos-Kettleman City area of the western San Joaquin Valley are alluvial-fan, flood-plain, lacustrine, and deltaic deposits; the sources of the sediments were the Sierra Nevada and Diablo Range. They are diverse and heterogeneous in texture, often poorly sorted, and their geometric-mean particle size is probably between 30/i and 60/j. Montmorillonite is the principal clay mineral, accounting for 70 percent of the clay-mineral assemblage and 10 percent of the sediments as a whole. Calcium is the predominant exchangeable cation. The sediments underlying the Tulare-Wasco area of the southeastern San Joaquin Valley are mainly alluvial-fan and shallow-marine deposits, plus subsidiary flood-plain and lacustrine deposits; all are derived from the Sierra Nevada. The nonmarine sediments are mostly poorly sorted and heterogeneous, having a mean particle size of 40/i-80/l. The shallow-marine sediments are more uniform, consisting of siltstone (mean particle size 5/l-1 Og) and fairly well sorted sands (mean particle size 250/i-500/i). Montmorillonite (plus some vermiculite) is the principal clay mineral, comprising about 10 percent of the nonmarine sediments and 20 percent of the marine siltstones. Calcium is the dominant exchangeable cation in the nonmarine sediments. The exchangeable-cation assemblage in the marine siltstones is more diverse, consisting of variable proportions of calcium, sodium, magnesium, and hydrogen. The uppermost 1,000 feet of sediments underlying the Santa Clara Valley is alluvial, with perhaps a few minor interbedded lacustrine deposits; the sources of the sediments were the adjoining Santa Cruz and Diablo Ranges. Coarser sands and gravels (mean size on the order of 500^-1,000/1) are found below the courses of the main streams of the valley. Finer silts and clays (mean size on the order of 5/i-10/i) underlie the parts of the valley away from the main streams. Montmorillonite is again the dominant clay mineral, comprising between 5 and 25 percent of the sediments, depending on the general fineness of their particle size. Calcium is the dominant exchangeable cation. In the sediments underlying the Arvin-Maricopa area at the southern end of the San Joaquin Valley, the clay-mineral assemblage is also dominated by montmorillonite. INTRODUCTION The petrologic characteristics of sediments determine their responses to changes in overburden load. Detailed knowledge of these characteristics—especially particle size, clay-mineral and exchangeaJble-cation composition, and the constituents dissolved in interstitial waters—and how they vary in any group of sediments is therefore necessary for a fuller understanding of the compaction of the sediments. The sediments whose compaction accounts for the subsidence of the land surface in four areas of the San Joaquin and Santa Clara Valleys of California (fig. 1) are the subject of this report. The compaction and 20 0 20 100 MILES Figure 1.—Principal areas of land subsidence in central California. Heavy lines enclose areas of larger scale maps in figures 2, 16, 28, and 36. ClC2 MECHANICS OF AQUIFER SYSTEMS land subsidence in these areas are dearly related to the depletion of artesian pressure (increase of grain-to-grain load) in the sediments, which is a result of confined ground water being pumped from the sediments faster than it is being replenished. Because the rates of compaction and subsidence are rapid and can be measured, these areas were selected as field laboratories for a program of study of the mechanics of aquifer systems. Because the compaction represents an acceleration of the natural processes that would have taken place with the further accumulation of overlying sediments, these are also opportune areas for general studies of the compaction of sediments. A fuller discussion of the problems of land subsidence and aquifer compaction and the ways in which the problems have been approached in this program are given by J. F. Poland in his foreword to the first chapter of this series (Johnson and others, 1967). PURPOSES OF REPORT This report is one of a series, all chapters of Professional Paper 497, on the mechanics of aquifer systems in California and elsewhere. It is also the second of three chapters by the same author that treat the petrologic aspects of compaction. The first of these three chapters, B (Meade, 1964), is a comprehensive review of previous work on the factors that influence pore volume and fabric of clayey sediments under increasing overburden loads. The second of the chapters—this report—is mainly descriptive and is intended to serve a dual purpose. Its first concern is the variation and distribution of some of the petrologic factors that the review of previous work shows to be significant influences on compaction. It is also meant to be a contribution to the general petrology of the post-Miocene fresh-water-bearing sediments of the San Joaquin and Santa Clara Valleys of California. The results are presented in a form that can be coin pared readily with the results of similar analyses of sediments in other areas—whether the comparison be for petrologic or engineering purposes. The third chapter (R. II. Meade, Compaction of sediments underlying areas of land subsidence in central California, in preparation as Prof. Paper 497-D) relates, by statistical analysis, the variations in overburden load and petrologic factors to variations in the pore volume and fabric of the sediments. Although it may inconvenience the reader, the division of the petrologic study into three chapters limits the bulk and, hopefully, enhances the readability of the separate reports. Descriptions of the sources and inferred modes of deposition begin the discussions in this report of the sediments of each of the areas. These descriptions are mainly meant to provide a general background and a spatial framework for the discussions of specific petrologic characteristics that follow them. The sections of this report that deal with particle size are an extension of the presentation and discussion of particle-size data given by Johnson, Moston, and Morris 1967). Although the two discussions are based on the same sets of size analyses, they overlap only slightly. Whereas Johnson and his associates presented the results of the analyses with no interpretation, the discussions in my report are aimed toward (1) describing the variations in particle size and arriving at meaningful estimates of average size, (2) describing the spatial variations in particle size, (3) describing the relations of particle size to source areas and types of deposits, and (4) finding consistent relations between the particle-size measures themselves. These efforts involve a moderate use of statistical techniques. The sections of the report that concern the clay minerals and associated ions are aimed toward (1) estimating the total amount of clay-mineral material as well as the relative amounts of the different clay-mineral species in the sediments, (2) describing the exchangeable cations and soluble salts associated with the day minerals, and (3) making some tentative judgments of the origins of the different clay minerals. COIXECTIOH OF SAXPXES The samples on which this study is based came mostly from eight core holes, four in the Los Banos Kettleman City area and two each in the Tulare-Wasco area and Santa Clara Valley, and from one test hole in the Arvin-Maricopa area. All the coring was done by drilling crews of the TLS. Bureau of Reclamation. Details of the coring are given in table 1. Locations of the holes are shown in figures 2, 16, 28, and 36. The sediments were sampled with a rotary-driven core barrel 3 inches in diameter. Cores were logged by visual examination at the drilling sites, and selected samples were sealed in wax for later study. Samples from seven of the holes—all but the Oro Loma core in the Los Banos Kettleman City area and the few sediments that were cored in the Lakeview test hole in the Arvin-Maricopa area—were analyzed for physical and hydrologic properties by the Hydrologic Laboratory of the ILS. Geological Survey in Denver. Samples from all the holes were studied petrographically. In addition to the core-hole samples, surficial samples from the Los Banos-Kettleman City area and the Santa Clara Valley were included in the study of day minerals. These samples were collected by W. B. Bull, T. J. Conomos. and me. #PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C3 Table 1.—Core holes and details of coring . Nearest town Location of care bole {township/ range-section: Mount Diablo base line and meridian) Depth of core hole (fleet below land surface) Cored intervals (fleet below land surface) Core recovery (percent total cored intervals) Las Bum uCStim Oro Loma 12S/12E 16 1,005 3O-I0, 70^5,110-120,150-160,180-190, 230-240, 270-281, 320-329, 360-1,005, 73 14S/13E -11 1,500 30-40, 70m 110-120,150-160,190-200,230-240, 270-280,310-320,3S0-360,390-400, 430-440, 470-480, 510-520, 550-560, .590-600, 630-1,497. 70 Camttua Creek 16S/15E-31 2,000 1 250-260,290-300,330-310, 370-380,410-420,490-460, -490-1,050,1,150-1,600,1,630-4,640,1J670-1,660, 1,710-1,720, 1,750-4,760, 1,790-1,800, 1,830^1,840,1,870^1,880, 1,910-1,920, 1,950-4,960, 1,990-2,000. 57 Huron 1SS/17E -22 2,20J 30-40, 80^0, 120-130,160-170,210-220,230-240, 270-280,310-320,350-360, 390-400, 430-440, 470-480, 510-520, 550-560, 5904500, 630-640, 670-680, 710-2,110. 38 Tatars-Wasco Pudey 2SS/25K -IS 24S/26E -36 760 30-40, 70-80,110-120,150- 73 2,200 160,190-200,210-240, 260-752 504,900,1,908-4,965, 81 2,000-2,012, 2,040-2,061, 2,090-2,110, 2,140-2,180. Santa On Valley Sunnyvale-. San Jose _ «&/ JW-M 7B0 IE 1« L«M 1,002 30-265, 300-365, 400-467, 512-581,600-675,710485 30-40, 70-80, 107-140, ISO-165, 185-290,300-356, 401—455, 500-618,094-850, »00-®56l 69 30 Ini, llrt. Laberiev. 11N/21W-3 > 1,500 315-319, 392-404, 530-543, 660-666*, 085-096, 810-816, 1,146-1,155, 1,455-1,460. 57 11 Depth finmeteeffrac fag. Aftereileetri-elop wasrun, tlie'drfllpope (newly aetpuned) was measured and found to he 035 Ft longer per 100 ft Ufaaira figured during coring. - San Bernardino base line and meridian. ACKNOWLEDGMENTS I'll is report describes the results of a large number of laboratory analyses and programs, many of which were carried out by members of the UJS. Geological Survey other than me. The Hydrologic Laboratory of the Survey in Denver made the particle-size analyses. David Handwerker wrote a machine program to compute statistics from the particle-size analyses. J. C. Hathaway, H. C. Starkey, and G. W. Chloe determined the clay minerals in a group of 25 samples from the Lars Banos-Kettleman City area. T. J. Conomas determined the clay minerals in sediments from San Fran- cisco Bay. Claude Huffman, A. J. Bartel, II. II. Lapp, and I. C. Frost determined the soluble anions associated with the clays. H. C. Starkey and T. Manzanares determined the exchangeable cations. EL E. Lohman, Ellen J. Moore, Patsy B. Smith, and D. W. Taylor identified some of the fossil remains. Meyer Rubin provided a radiocarbon date. I. E. Klein, of the U.S. Bureau of Reclamation, lent me a large collection of core-hole samples that were taken for his use, and he determined the source areas of the sediments in the Oro Iema core. The San Jose Water Works and the California Department of Water Resources provided chemical analyses of ground water in the Santa Clara Valley. In the determination of clay minerals, I was assisted in the laboratory by J. O. Berkland, W. R. Cotton, F. P. Mangier, and, most extensively and ably, by J. B. Corliss. L K. Lustig reviewed sections of the manuscript. The counsel and guidance of J. F. Poland and Julius Schlocker, as well as the observations, findings, discussions, and criticisms of my colleagues on the project—W. B. Bull, J. II. Green, A. I. Johnson, B. E. Lofgren, R. E. Miller, and R. P. Most on—contributed heavily to the substance and form of the report. SEDIMENTS IN THE LOS BANOS-KETTLEMAN CITY AREA Tn the Los Banos-Kettleman City area, the sediments whose compaction accounts for the observed land subsidence are almost ent irely nonmarine—mostly alluvial. They came from the Diablo Range that forms the southwestern border of the area and from the Sierra Nevada that lies across the San Joaquin Valley to the northeast. The sediments occur chiefly within the Tulare Formation or the alluvium that lies above the Tulare, locally, however, in the southern part of the area, deep water wells tap sediments within the Etchegoin and San Joaquin Formations. The age of these sediments is not closely defined; but the lowermost are no older than middle Pliocene, and the uppermost were deposited in modem times. This study is based chi samples taken from four core holes that were drilled into these sediments, about to the base of the Tulare Formation. Locations of the core holes, all of which are in western Fresno County, are shown in figure 2. The geology of the sediments that are undergoing artificially induced compaction is described in detail by Miller, Green, and Davis, in preparation as Professional Paper 437—E. Other reports by Bull (1964a, b),C4 MECHANICS OF AQUIFER SYSTEMS 120°30' laO'OO' Figure 2.—Los Banos-Kettleman City area showing location of core holes.PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C5 describe the lithology and depositional history of the alluvial deposits of Quaternary age in the Los Banos-Kettleman City area. SOURCES OF SEDIMENTS The Tulare Formation and younger alluvium represented by the cores in the Los Banos-Kettleman City area were derived from two mountainous terranes: the Diablo Range on the west side of the San Joaquin Valley and the Sierra Nevada on the east side (fig. 2). The streams that flow from the Diablo Range into this part of the valley drain mostly areas of folded, but otherwise unmetamorphosed, Cretaceous and Cenozoic sedimentary rocks; some streams also drain areas underlain by the partly metamorphosed sediments and ultramafic rocks of the middle-to-late Mesozoic Franciscan Formation. In the central Sierra Nevada, the rocks underlying the principal drainage basins are markedly different from the rocks in the Diablo Range. Sierra Nevada rocks are mainly granitic but include lesser amounts of metamorphic rocks and Cenozoic sediments. Deposits derived from the two sides of the valley, therefore, are easily distinguished from each other on the basis of their minerals and lithic fragments. SOURCE CRITERIA The sources of the Tulare Formation and younger sediments in the four cores were determined by examining silts, sands, and what gravels were available under the binocular microscope. This examination was supplemented by petrographic-microscope examination of a few thin sections of well-sorted sands. The clays were assumed to have come from the same sources as intercalated silts, sands, and gravels. The typical sands from the Sierra Nevada are light-colored and micaceous and contain more than 25 percent feldspar—enough for them to be called “arkosic” by Gilbert’s definition (Williams and others, 1955, p. 292-295). The amount of mica ranges from 2 to 5 percent and is nearly all biotite in fresh-looking flakes or books. The biotite grains are usually the same size as the principal nonmica grains or larger. The sands also contain 1-2 percent of green hornblende in prismatic grains. Sands from the Diablo Range are darker—some consisting of more than 30 percent dark grains—and generally contain more lithic fragments. The characteristic dark constituents are subrounded rock fragments: partly altered andesite, greenish serpentinite in rounded and often oblate grains, and brick-red chert in suban-gular to subrounded grains. Mica is present in amounts of 2 percent or less, usually in weathered-looking flakes that are the same size as the principal nonmica grains or smaller. The principal sources of the core-hole sediments, as determined by the above criteria, are shown in figure 3. Small admixtures—for example, a few grains of chert and serpentine mixed with sediments mainly from the Sierra Nevada—are not shown. Such mixtures are typical of flood-plain and lacustrine deposits. The sources of the sediments below 1,600 feet in the Cantua Creek core could not be determined with certainty because only 25 percent of this interval of sediment was cored and only 15 percent of the interval was recovered. ANDESITIC SANDS Andesitic detritus is a common constituent of the sands from the Diablo Range. It is especially abundant in the sands that lie between 1,500 and 1,000 feet below the surface in the Mendota core and between 1,000 and 500 feet in the Oro Loma core. It is probably derived from older Pliocene andesitic sandstones of the Etche-goin and San Joaquin Formations that crop out on the east flank of the Range. These Pliocene sandstones have been described by Lerbekmo (1957, 1961). They consist largely—in some places almost entirely—of fresh andesitic debris: intermediate plagioclase, 40-70 percent andesitic rock fragments, and 10-30 percent ferromagnesian minerals. A characteristic feature is their striking blue color, which is caused by grain coatings of authigenic montmoril-lonite derived from the solution of volcanic detritus within the sandstones. The andesitic sands in the Tulare Formation and younger sediments as examined in the cores differ significantly from the Pliocene sandstones, and the differences indicate that the sands probably came in part from older rocks. Andesitic detritus in the younger sands is always mixed with other Diablo Range material—most conspicuously chert and serpentine—and andesite rock fragments generally comprise less than 25 percent. These andesite fragments are generally somewhat altered. Within the Mendota core, the alteration seems to increase with a decrease in the age of the sediments, suggesting that perhaps the andesitic material was reworked more than once. The grain coatings are only sporadically developed and are not so intensely blue as those in the sandstones of the Pliocene Etche-goin and San Joaquin Formations exposed on Anticline Ridge. TYPES OF DEPOSITS Three main types of deposits, all waterlaid, have been recognized in the Tulare Formation and younger sediments of the area: these are alluvial-fan, flood-plain, and lacustrine deposits. As figure 3 suggests, the twoC6 MECHANICS OF AQUIFER SYSTEMS ORO LOMA CORE MENDOTA CORE CANTUA CREEK CORE HURON CORE SOURCE TYPE OF DEPOSIT DR ^SN AF FP DR + SN ^DR LA DR FP 500 1000 EXPLANATION SOURCE SOURCE TYPE OF DEPOSIT DR AF FP DR + SN LA SN FP SN + DR DR AF LAP) TYPE OF DEPOSIT DR, Diablo Range AF, Alluvial fan SN. Sierra Nevada FP, Flood plain LA. Lacustrine 500 DR + SN 1000 1500 SOURCE DR DR SN Mostly DR(?) Mostly SN(?) TYPE OF DEPOSIT AF LA AF FP ^LA(?) FP LAP) 500 1000 1500 2000 SOURCE DR DR SN TYPE OF DEPOSIT AF LA AF Deltaic O 500 2 £T 3 (0 O z < 1000 £ o 1500 X I- Q_ 111 O 2000 2200 Figure 3.—Principal sources and types of deposits represented by sediments cored in the Los Banos-Kettleman City area. Sources of Oro Loma core identified by I. E. Klein. Types of deposits identified mainly by R. E. Miller. alluvial types are far more abundant than lacustrine deposits. A subsidiary type, the deltaic deposits, was identified near the bottom of the Huron core. These deposits were recognized and delineated mainly by R. E. Miller, from whom much of this section of the report has been taken. Only selective descriptions of the deposits and their modes of deposition are given here; they are intended to emphasize the conditions that influenced the response of the sediments to compaction. Fuller description of the deposits and their spatial distributions are given in the report by Miller, Green, and Davis, in preparation as Professional Paper 437-E. CRITERIA FOR DISTINGUISHING PRINCIPAL TYPES OF DEPOSITS LARGE-SCALE CRITERIA Table 2 gives the large-scale criteria, developed mainly by R. E. Miller, that were used to distinguish the types of deposits. These criteria reflect the different sets of conditions—mainly hydraulic and chemical— that constitute the different depositional “environments.” They are listed in decreasing order of the use that was made of them in separating the different depositional types. See the geologic cross sections and isopach maps of Miller, in preparation as Professional Paper 437E, for evidence on the distribution and shape of the several types of deposits. Alluvial-fan deposits were the easiest to distinguish from the other types, primarily on the basis of the color of the sediments, substantiated by their wedge shape in three dimensions. The characteristic yellow brown is a result of the long period of oxidation between deposition and burial below the water table. The “oxidized” color is retained even after burial to 1,500 feet or more below the water table. The distinction between flood-plain and lacustrine deposits is less certain, for it has to be made on the basis of organic remains and the nature and distribution of the sediments within the deposit. The distinction between the two types becomes tenuous in the case of non-fossiliferous and generally fine-grained sediments that were deposited in large depressions or abandoned channels on a flood plain. Such sediments were called flood-plain deposits unless correlation of electric logs showed them to be extensive, continuous, and consistently fine grained. TEXTURAL EVIDENCE OF PROCESSES OF DEPOSITION IN FINE-GRAINED SEDIMENTS Further evidence of the depositional history of the fine-grained sediments—clays and clayey silts—camePETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C7 Table 2.—Criteria for distinguishing alluvial-fan, flood-plain, lacustrine, and deltaic deposits, Ia>s Banos-Kettleman City area [Color code from Rock Color Chart (Goddard and others, 1948)] Criterion Alluvial-fan deposits Flood-plain deposits I>acustrine deposits Deltaic deposits Color of sediment . — Yellowish brown (lOY/f): lesser amounts of grayish brown (5YR) and olive brown (510-Color due to staining of grains by iron oxide. Greenish grays and grayish greens (5G, 5GY, 10G), dark gray (N), bluish gray (5B), bine green (5BG). Authi-genic iron sulfides often present. Same as alluvial-fan deposits. Same as flood-plain deposits. Same as flood-plain deposits. Nature and distribution of sediment within the large-scale deposit. Heterogeneous and variable; lenses, tongues, and beds of clay, silt, sand, and gravel grade into one another or change abruptly both vertically and laterally. Sands may be crossbeddcd. Uniform; may be homogeneous for thicknesses of tens of feet. Generally fine grained. Heterogeneous but generally coarse grained. Sands commonly cross bedded. Source of constituted grains From one side of the San Joaquin Valley only. From both sides of the San Joaquin Valley. From both sides of the San Joaquin Valley. From both sides of the San Joaquin Valley but chiefly from Sierra Nevada. Three-dimensional shape of deposit in large scale (horizontal dimensions in miles or tens of miles). Wedge shaped, with thickest part toward mountains from which materials came. Lenticular. Layered or lenticular, but widespread and fairly uniform in thickness. Lenticular. Organic material Plant material in small fragments disseminated through sediment; in trace amounts or a few percent at most. Plant material in fragments both large and small; larger pieces often intact eno-.igh for structures to be discerned. Plant material in fragments, often large and structurally intact. Also fresh-water organisms such as diatoms and mollusks. Plant material in fragments, often large and structurally intact, in peatlike accumulations. High proportion of finely disseminated organic material in sdme days. Fragments of fresh- and brackish-water mollusks; fish remains. from observations or measurements made on short core samples, 2-5 cm thick. Diagnostic textural features are listed in table 3 in decreasing order of their usefulness. In small samples one cannot make the three-way distinction illustrated in table 2, but must confine oneself to two categories: sediments deposited by moving streams and those deposited in standing water. Because of the lack of definitive criteria in small samples, neither distinction could be made in hand specimens of coarser grained sediments. The most distinctive textural feature of the finegrained sediments deposited by moving streams in the Los Banos-Kettleman City area is a chaotic fabric. In some hand specimens the clay-size particles seem to be concentrated in sand-sized aggregates which are usually rounded to subrounded and are platy, oblate, or spherical in shape. The aggregates, when present, are in a matrix of sand-silt-clay, in concentrations ranging from a few percent to nearly half the sediment. In thin sections the aggregates appear to consist mainly of well oriented clay-mineral particles. The orientation of the aggregates with regard to each other, however, is generally random. Table 3.—Criteria for distinguishing conditions under which fine-grained sediments were deposited, Los Banos-Kettleman City area Criterion Deposited by moving water Deposited in standing water Fabric: Discernible in hand specimen Discernible in thin section Clay-particle orientation ratios measured by X-ray method. 1 Porosity_____________________________ Organic material_____________________ Coarsest particle in sediment as measured by C, the 1st percentile of the size distribution. Often chaotic: Clays in chunks or rounded sand-sized aggregates in matrix of poorly sorted sand-silLelay. May be bedded: Marked differences in particle size between adjoining laminae. Clay laminae may have graded contact with underlying laminae and abrupt contact with overlying laminae. Chaotic: Small aggregates'of well-oriented clay in random orientation with regard to other aggregates. A little mass extinction in matrix. 1.5 or less________________________________ Relatively less *___________________________ Plant material in traces, or a few percent at most, disseminated in small fragments. Generally larger than 100p__________________ Uniform or distinctly and finely laminated; only small differences in particle size between adjoining laminae. Regular preferred orientation of platy particles parallel to bedding. Mass extinction well developed over large areas. 1. 5 or more. Relatively greater. * As much as 10 percent. Original vegetal structures may be intact. Often associated with authigcnic sulfide minerals. Generally smaller than 250#i. 1 Method explained in earlier paper (Meade, 1961). Orientation ratios near t.O 2 No numbers assigned: porosity variable with depth and particle size, denote random orientation: ratios larger than l.Osignify preferred orientation of clay particles parallel to bedding.C8 MECHANICS OF AQUIFER SYSTEMS The aggregates probably originated in two ways: as fragments of shale that were carried out of the mountains and rounded en route and from disruption of previously deposited thin layers of clay. Evidence of the latter process is found preserved in all degrees of disruption, from the undisturbed clay layers to the chaotic array of clay aggregates (fig. 4). Apparently, after a clay layer has dried to the point where it cracks into pieces, the pieces may be picked up and incorporated into the sediment load of subsequent water flows. The pieces are then broken, rounded, and deposited in a random array together with the other constituents of the sediment load. Clay Sand, silt, and clay Figure 4.—Cross sections of clay aggregates showing progressive stages of development from undisturbed clay layers. In contrast, the fabric of clays and silts that seem to have been deposited in standing water is often uniform. Clay particles are oriented parallel to the bedding or nearly so. Standing-water deposits are often finely bedded, are more consistently fine grained, and are often better sorted. The porosity of standing-water sediments seems to be greater than that of moving-stream sediments of the same particle size. This impression is supported by the observations summarized by Gaither (1953, p. 184), to the effect that sands deposited in standing water generally have greater porosities than those deposited subaerially. Perhaps this difference also exists in silts and clays. Other factors, however, may be at least partly responsible for the greater porosities of the standing-water sediments. The lacustrine Corcoran Clay Member of the Tulare Formation contains diatom skeletons whose openwork structure seems to contribute to the porosity of the enclosing sediments. Another coincidental factor is the greater proportion of sodium adsorbed by the clays in the lower parts of the cored intervals (fig. 15), included in which are most of the standing-water sediments other than the Corcoran Clay Member. A greater proportion of adsorbed sodium, relative to other cations, may contribute to the greater porosity of these clays (Meade, 1964, fig. 11). Higher porosity, therefore, is not a definitive criterion in these cores for distinguishing the two types of deposits. Ho single criterion given in table 3 is enough to identify the conditions of deposition: the proper combination of fabric and porosity is fairly convincing, but three criteria are generally necessary for unequivocal identification. Most of the fine-grained alluvial-fan deposits in the Los Banos-Kettleman City area fall unequivocally into the moving-stream category, although a few oxidized sediments within large wedges of alluvial-fan deposits fell into the standing-water category. Lacustrine deposits should fall certainly into the standing-water category. Silts and clays deposited on flood plains can fall into either category. In small segments of cores, one cannot tell whether a non-fossiliferous highly porous greenish- to bluish-gray uniformly and finely bedded clay is a lacustrine or flood-plain sediment—this must be determined on the basis of the large-scale geometry of the deposit. alluvial-fan deposits The alluvial fans that occupied this part of the San Joaquin Valley in the past are thought of as similar to the fans that line the west side of the valley today (described in detail by Bull, 1964a, b). The alluvial-fan deposits found in the core holes have been derived, as are the modem fan deposits in the area, entirely from the Diablo Range. They were deposited by water-flows—streams and sheet flows; very few, if any, mudflows seem to have moved as far out into the valley as the locations of the core holes. The sediments are unsaturated for substantial depths below the surfaces of the modern fans. Throughout most of the area, the water table lies more than a hundred feet below the land surface and as much as several hundred feet below the surface along the mountain front. The principal streams flow only during the rainy winter months and are usually dry for more than half the year. After leaving the mountain front and flowing into the main San Joaquin Valley, they are never in complete hydraulic continuity with the water table (Rantz and Richardson, 1961; Richardson and Rantz, 1961, p. 19, 24, 26, 29). Water from the principal streams percolates into the underlying sediments and moves to the water table mainly by unsaturated flow. The smaller streams are ephemeral; that is, they flow only for short periods after rainstorms and are never in hydraulic continuity with the water table. They supply very little influent seepage to the ground-water body. Most of the sediments, consequently, remain unsaturated and subject to oxidation between the time they are deposited and the time they are buried below the water table.PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C9 FLOOD-PLAIN DEPOSITS The flood plains that occupied this part of the San Joaquin Valley in the past are thought of as those of perennial streams. Sands and gravels were deposited in or near the principal stream channels; silts and clays were deposited on the adjoining plains when the streams overflowed their banks. The water table beneath the flood plains was probably close to the land surface: the state of preservation of some of the plant remains and the presence of authigenic sulfides suggest that the flood-plain sediments were not subjected to continued aeration and oxidation. At different times each side of the valley was the principal contributor of the flood-plain sediments found in the core holes. LACUSTRINE DEPOSITS Lakes occasionally covered large portions of this part of the valley in late Pliocene and Pleistocene time. Sediment wTas carried into the lakes by streams coming from both the Diablo Range and the Sierra Nevada, was moved about by currents within the lakes, and wTas deposited by slow settling in relatively still water. The most conspicuous of the lacustrine deposits is the Corcoran Clay Member of the Tulare Formation which lies at depths ranging from 200 to 900 feet below the present land surface in nearly half the San Joaquin Valley. It has been described and discussed by Frink andKues (1954), and Davis and others (1959, p. 76-81). Potassium-argon dating has shown that volcanic ash immediately overlying the Corcoran is about middle Pleistocene in age (Janda, R. J., in Bull, 1964b, p. A5). It is fine grained and ranges in thickness from 0 to 120 feet. Diatom remains are abundant—as much as 75 percent of some sediments—in its middle and lower parts. Substantial thicknesses of the Corcoran Clay Member, 85 and 75 feet, respectively, were cored in the Oro Loma and Mendota holes. Other sediments designated lacustrine, in the lower parts of the Mendota and Cantua Creek cores, are indicated in figure 3 as of questionable lacustrine origin. R. E. Miller identified these deposits as lacustrine (?) on the basis of their color, fine-grained texture, large-scale extent, and dimensions. However, the petrographic characteristics of the cored samples of these deposits— especially the degree of regularity of their fabric—do not show clear evidence of their having been formed in lakes. DELTAIC DEPOSITS The lowermost 400 feet of sediment penetrated by the Huron core hole is interpreted by R. E. Miller as a deltaic deposit, on the basis of correlation with typical delta deposits to the east. These sediments are similar to the flood-plain deposits, except that they contain generally more organic remains. Reed, grass, and wood remains constitute 15-20 percent of some of the finegrained sediments. Other sediments, in which plant remains are not so apparent are colored dark gray (A2-N3, Goddard and others, 1948) by finely divided organic material. Also found in these deposits (at 2,054 ft) were fragments of the brackish-water gastropod assemblage: Littorina, Amnicola. and Fluminicola. PARTICLE SIZES The study of particle size in the Los Banos-Kettleman City area is based on 305 samples from 3 core holes: Mendota, Cantua Creek, and Huron (locations shown in fig. 2). No particle-size analyses were available for samples from the Oro Loma core. The mean grain size in the 305 samples probably lies in the range of fine to medium silt, or between 10/x and 20/x (microns). Allowing for the fact that the coarsest sediments were not sampled adequately (see the discussion of “Sampling and particle-size analysis” p. C48), I estimate that the mean particle size of the sediments in the cored interval is in the coarse-silt range, or between 80/x and 60/u. This estimate is based on a comparison of the electrical-resistivity logs of the core holes and the particle-size data on the recovered material. Details of the 305 size analyses are given in table 5. Percentiles were read from cumulative curves provided by the Hydrologic Laboratory. Measures of sorting and skewness, computed from the percentiles, are defined on pages C49-C50. PARTICLE-SIZE DISTRIBUTIONS OF RECOVERED SEDIMENTS The particle-size distributions of the cored sediments will be illustrated in two main ways: on triangular plots of the proportions of sand, silt, and clay; and as grouped information about the average sizes, sorting, and skewness of the samples. The triangular diagram is one of many ways in which size data may be summarized, and it is well suited to give an overall impression of the range and distribution of particle sizes. The reference diagram in figure 5A shows the nomenclatural system of Shepard (1954). The samples are segregated by depositional type in figures 5R-5A; source areas are indicated by open circles (Sierra Nevada), dark circles (Diablo Range), and crosses (mixed Sierra and Diablo Range). Triangular diagrams of the sediments grouped by core holes are given by Johnson, Moston, and Morris (1967). Looking at figures 5R-5A as a whole, one can see the variety and heterogeneity of the particle sizes. There is little or no concentration of samples in any category.CIO MECHANICS OF AQUIFER SYSTEMS A EXPLANATION MICRONS Gravel >2000 Sand 62-2000 Silt 4-62 Clay <4 SOURCE •. Diablo Range o. Sierra Nevada +, Mixed CLAY SAND AND 25 50 75 SILT GRAVEL B CLAY SAND AND 25 50 75 SILT GRAVEL C CLAY CLAY D E Figure 5.—Sand-siltclay percentages of sediments from Mendota, Cantna Creek, and Huron cores, Los Banos-Kettleman City area. Based on data from tbe Hydrologic Laboratory of the Geological Survey. A, Nomenclature after Shepard (1954). B, Flood-plain sediments. C, Alluvial-fan sediments. D, Lacustrine—including lacustrine ( ?)—sediments. B, Deltaic sediments (from Huron core only).PETROLOGY, SEDIMENTS UNDERLYING AREAS OP LAND SUBSIDENCE, CENTRAL CALIFORNIA Cll Even though nearly two-thirds of the samples fall into the silty clay, clayey silt, and sand-silt-clay fields, and more samples fall into the clayey-si It field than into any other, the coarser sediment, categories in the diagram are also well represented. All but 11 of the samples contain 5 percent or more clay. The amount of gravel included in “sand and gravel” in figure 5 (B and O) is not large. Only 24 samples contained gravel (particles larger than 2,000^1 in diameter), and of these, only 12 contained 1 percent or more. Only four, all flood-plain sediments from the Mendota core, had as much as 5 percent gravel. The particle-size characteristics of the several types of deposits or of the sediments from the two source areas, as shown in the triangular diagrams, are rather similar. Heterogeneity is characteristic of all. Perhaps the only readily visible difference is between the two sources of flood-plain sediments, as shown in figure 5B: sediments from the Sierra Nevada seem to be better sorted (points closer to the sand-silt and silt-clay joins) than those from the Diablo Range. The relations of sizes and sorting to sources and deposit! on a 1 types is treated further in the section “Relations between particle-size measures and their bearing on the depositional history of sediments”; see especially figure 12. Another way of generalizing particle-size data is by summarizing the measures of central tendency—the mean, median, and mode—of the particle-size distributions. Only the median and modal diameters, which are more easily determined than mean diameters, are given here. The distribution of the median diameters (Md) of the 305 samples is shown graphically in the top row of figure 6. The median “is that diameter which is larger than 50 percent [by weight] of the diameters in the distribution, and smaller than the other 50 percent” (Krumbein and Pettijohn, 1938, p. 229). Most of the median diameters fall in the range from 2/i to 250/l More medians fall into the 8/»-16fi intervals, the fine silt category, than into any other interval. This does not necessarily mean that 8/1I6/1 is the most abundant median-particle range in the sediments of the area. It may reflect selective sampling: that is, perhaps more of the visually estimated “average” samples (p. C48) had median diameters in this size interval than in any other. A secondary maximum in the 125/*-250/i interval suggests that, had the gravels and coarse sands in the section been recovered more completely, the distribution of Md values might have had two principal maxima, one in the fine-silt interval and the other in the sand-sized range. Where the distribution of median diameters gives a better impression of the “average” particle size, the distribution of modal diameters tells more about the MENDOTA CANTUA CORE CREEK CORE ALL SAMPLES 1305) HURON CORE 30 LjII* Jfc. 0.5 4 62 1000 1 4 62 1000 1 4 62 1000 MEDIAN DIAMETER. IN MICRONS 30 Q- 0 2 30 30 SAMPLES <280) WHOSE MODES COULD BE DETERMINED Ua. W Liu, 2 4 62 1000 1 4 62 1000 1 4 62 1000 MEDIAN DIAMETER. IN MICRONS UJL. UH U*L 2 4 62 1000 1 4 62 1000 1 4 62 1000 MODAL DIAMETER. IN MICRONS SAMPLES 12611 WHOSE OUARTILES COULD BE DETERMINED Ul W 1*l. 2 4 62 1000 2 4 62 1000 2 4 62 1000 MEDIAN DIAMETER. IN MICRONS k k. Ll 02 024 024 QUARTILE DEVIATION (QD.) Lju. L*l LL -0.2 -0.4 0 0.4 0.8 0.2 0 0.4 -0.2 0 0.4 QUARTILE SKEWNESS Figitke 6.—Measures of average size, sorting, and skewness in sediments from Mendota, Cantua Creek, and Huron cores, Los Banos Kettleman City area. Measures of sorting (QD*) and skewness (Skio/QI)<>) defined on page C49. relative abundance of grain sizes. The modal size interval of a sediment (National Research Council’s size intervals in this study, see table, p. C49) is the one that contains more material by weight than any other. The distribut ion of 280 modal sizes is shown in the third row of figure 5. The modal sizes of the other 25 samples could not be determined because too much of each sample was finer than l.Oji, and the distributions of sizesC12 MECHANICS OP AQUIFER SYSTEMS smaller than 1.0/u. were not determined. Fine sand (125ju.-250fi) is the most abundant material in 70 samples, in spite of the fact that sediments whose median diameters fell into this category were poorly recovered. The abundance of fine sand is probably related to the relative ease with which this material, compared to particles of other sizes, is picked up and transported by running water (see fig. 8 and the accompanying discussion). Neither of these two measures of central tendency provides a perfect means of summarizing data on complex particle-size distribution. Ideally, in a normal frequency distribution, the median and mode coincide, but very few of the sediments considered in this report consist of particles whose sizes are distributed normally. The second row of figure 6 consists of histograms of the median diameters of the same 280 samples whose modal sizes are illustrated in the third row. One can readily see from these histograms that conclusions drawn about sediments from a single one of these measures are likely to be incomplete. SPATIAL DISTRIBUTION OP PARTICLE SIZES The differences between the parameters of particle-size distribution in the three cores are shown in the bottom three rows of figure 6. The sediments from the Huron core are generally finer grained, less well sorted, and less skewed than the sediments from the Mendota core. Furthermore, the parameters of particle-size distribution seem to be more uniform (less dispersion, as shown by the histograms) in the Huron core. The particle-size properties of sediments from the Cantua Creek core are intermediate between those of sediments from the other two cores. Although this suggests a progressive change in a southeasterly direction toward finer grained, more poorly sorted, less skewed, and more uniform sediments, more comprehensive regional analysis of the sediments of the area, using electric logs and data from other core holes (Miller and others, in preparation as Prof. Paper 437-E), does not show such a progressive trend. The differences between the cored sediments are local rather than regional features. Figure 7 shows the patterns of change in particle size with depth in the three cores. The resistivities of the sediments (from electric logs), as well as their median diameters, indicate particle size. The higher resistivities in these sediments are associated with the coarser sizes. Using the same symbols as in figure 5, sources are indicated by open circles (Sierra Nevada), dark circles (Diablo Range), and crosses (mixed). Types of deposits are indicated in the right column of each composite log. For composite logs that contain other information, namely the spontaneous potentials and gen- eralized lithologies of the sediments, see the report by Johnson, Moston, and Morris (1967). The Mendota core shows the most regular changes in particle size with depth. Consider the sediments from the bottom of the core to the top—the order in which they were deposited. Progressively coarser sediment (1,500-1,200 ft) was deposited as the environment changed from a lake( ?) to an alluvial fan and then to a flood plain. The flood-plain deposits became progressively finer (1,200-1,000 ft), and then coarser again as the source shifted from the Diablo Range to the Sierra (1,000 to about 750 ft). Above them was deposited the uniformly fine grained and lacustrine Corcoran Clay Member of the Tulare Formation (700-625 ft). Although too few median diameters were measured in sediments above the Corcoran in the Mendota core, the resistivities suggest that the sediments coarsen progressively between the top of the Corcoran and the present land surface. In the Cantua Creek core the variations in particle size are not so regular. Although the resistivity log suggests that the lacustrine (?) and flood-plain deposits penetrated in the lowest 300 feet of the hole are uniformly fine grained, the few median diameters measured in this part of the core do not suggest uniformity. Even more scattered is the distribution of the median diameters of the flood-plain deposits from the Sierra (1,700-980 ft) and of the alluvial-fan sediments from the Diablo Range (980 ft to the surface). The resistivity log suggests a coarsening of the flood-plain deposits (1,100-1,000 ft) just before the change to alluvial-fan deposition. Too few median-diameter measurements are available to support this observation, however; the interval between 1,150 and 1,050 was not sampled because of an interruption in the coring schedule to correct an excessive drift of the hole away from the vertical. Within the alluvial-fan deposits, at about 600 feet below the surface, lies 60 feet of well-sorted sand that was deposited here (perhaps as a beach) while the Corcoran Clay Member was being deposited elsewhere in the valley. Although the Cantua Creek core contains some short segments within which the particle size is fairly uniform, the general characteristic of the particle sizes in this core is diversity. Changes are not progressive but are mainly abrupt and local. The changes in the particle sizes of sediments in the Huron core are also mainly abrupt and local. As indicated in the histograms in figure 6, however, the median sizes in the Huron core are not scattered so widely as those in the other two cores. The pattern of median-diameter distribution in the deltaic sediment at the bottom of the core suggests a gradual coarsening as the source changed from the Sierra to the Diablo RangePETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C13 MENDOTA CANTUA CREEK HURON CORE CORE CORE MEDIAN DIAMETER, MEDIAN DIAMETER, MEDIAN DIAMETER, IN MICRONS IN MICRONS IN MICRONS 1 8 62 500 1 8 62 500 1 8 62 500 LLl O < Li- CC D (/) Q Z < £ o —I LU CD Ll) LlJ z I f— Q_ LU Q Figure 7.—Variations in particle size with depth, Los Banos-Kettleman City area. Resistivity log is left column of each composite; range, from left to right, is (>-30 ohms m2/m. (2,100-1,800 ft), but no such increase in grain size is indicated by the resistivity log of the same sediments. And although the resistivity log suggests a gradual coarsening of the alluvial-fan sediments between 1,800 and 800 feet, the distribution of median diameters shows no such change. Both the resistivities and the median diameters suggest a progressive decrease in grain size from the lacustrine sands near 700 feet through the alluvial-fan sediments to the present land surface. In summarizing the particle sizes of the sediments of the Los Banos-Kettleman City area, one may say that their outstanding feature is diversity. This is an important factor in the compaction of the sediments. Had the sediments been consistently coarse grained, their response to increasing effective overburden loads would have been less than has occurred—coarse-grained sedi- ments are compacted less per unit load increment than fine-grained sediments. Had they been consistently fine grained, their low permeabilities would have slowed the compaction to rates much less than those observed. The heterogeneous interlayering of compressible finegrained sediments and permeable coarse-grained sediments constitutes an aquifer system that responds efficiently to changes in overburden load by compacting rapidly and substantially. RELATIONS BETWEEN PARTICLE-SIZE MEASURES AND THEIR BEARING ON THE DEPOSITIONAL HISTORY OF SEDIMENTS Some sedimentologists have found that graphing particle-size measures against each other—especially average size against other measures—has helped them in understanding the hydraulic processes involved inC14 MECHANICS OF AQUIFER SYSTEMS the transport and deposition of clastic sediments. The work of some of these sedimentologists is reviewed in this section of the report. Then follow graphs of median diameter against measures of sorting, skewness, and the coarsest percentile for the sediments of the Los Banos Kettlcman City area. For those interested only in the direct description of the particle-size characteristics of the sediments, this section of the report is largely a digression that can be passed over quickly. REVIEW OF PREVIOUS WORK RELATIONB OF AVERAGE PARTICLE SIZE TO SORTING AND SKEWNESS In many waterlaid sediments, the deviation (sorting) and skewness of particle-size distributions seem to vary in systematic and consistent ways with the average diameter. Inman (1919) pointed out these variations in a summary of studies of shallow-water marine sands and silts (fig. 8) and presented convincing evidence and arguments that they reflected the hydrodynamic relations that exist between running water and sediment particles. 16 62 250 1000 A C? O < > < => O Figure 8.—Relation of median diameter to (1) sorting and (2?) skewness in shallow marine sediments. Modified after Inman (1949, p. 52) ; chief modification is addition of skewness data from Buzzards Bay (Hough, 1940, p. 28-26). Other data sources: Cape Cod Bay (Hough, 1942, p. 21), Barataria Bay (Krumbein and Aberdeen, 1937, p. 8-9), Red Sea (Shnkri and Higazy, 1944, p. 62-63). So and Sk are sorting and skewness coefficients of Trask (1930, p. 594), based on qoartiles. Sorting reflects the relative ease with which particles of different sizes are picked up and transported by water. The best sorted sediments are those whose median diameters fall into the category of fine sand (125^-250/i). Inman states (1949, p. 61) that fine sands are hydrodynamieally unique from all other sizes in that: (1) they are moved by weaker currents than grains smaller or larger than themselves; (2) once moved they do not have as great a tendency to go into suspension as do smaller grains; and (3) they are more readily carried into suspension than larger material. Because materials both coarser and finer than fine sand are more difficult to move and since very fine material is readily carried into suspension, bottom sediment in the process of transportation tends to become progressively better sorted as its median diameter nears 0.18 mm [180/i]. Sediments with median diameters either larger or smaller than 0.18 mm tend to be more poorly sorted; the tendency toward poor sorting being more pronounced for fine sediments. This may he accounted for by the fact that the flnid does not as readily differentiate between the smaller diameters. Skewness seems to reflect the different means by which water transports particles of different sizes. In sands and finer materials, as suggested by figure 8Z?, the sediments with the least skewed particle-size distributions (log IOSk ~0) seem to be the sands and fine silts (Md 125^-1000/1 or finer than 16/i). The most skewed distributions are found in intermediate mixtures of sand and finer materials (Md 30/»-60/i). Such relations between particle size and skewness might be due to the fact that sand in most streams of moderate size (and presumably in currents in shallow seas) is transported as bed load— rolled and bounced along the bottom—and that materials finer than sand are usually carried in suspension. 'Fho less skewed sediments may have been transported by one means only, either as bed load or in suspension. The more skewed intermediate sediments may represent mixtures of material transported by both means and, for some reason, deposited together. Since Inman published these curves and his interpretations of them, many more studies of the size distributions of sediments have confirmed the existence of the relations of average diameter to sorting and skewness. For example, see the papers by Folk and Ward (1957), Fuchtbauer and Reineck (1963, p. 298), Griffiths (1951), Inman and Chamberlain (1955), Shumway (1960, p. 665), and Walger (1961). CM DIAGRAMS Another graphical method of portraying the particle-size distributions of sediments has been proposed by Passega (1957,1960,1964). He focuses attention on the coarser half of a sediment by graphing the median diameter against the first (coarsest) percentile, which hePETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C15 calls “C.” The first percentile is used as a measure of the competence of the depositing medium, and the median diameter represents the average grain size of the material deposited. By using parameters based only on the coarser half of a sediment, one considers the part of the sediment that reflects most sensitively the carrying and sorting capacities of the transporting and depositing media. An example of Passega’s graph, which he calls a “CM diagram” is shown in figure 9. He has suggested that aqueous sediments might fall into characteristic patterns according to the way in which they were transported or deposited. The solid-line sinuous pattern labeled NOPQRS is characteristic of sediments carried by rivers and other tractive currents. The pattern enclosed by the dashed line seems to be characteristic of the deposits of turbidity currents; sediments deposited slowly in still water fall in or near the circular pattern. The pattern NOPQRS, derived empirically from modem riverbed sediments in the United States and from Tertiary sediments in the United States and Italy, implies that sediments associated with tractive currents fall into a family of curves (fig. 10A) that shows the effect of hydrodynamic sorting. In fine-grained tractive sediments (RS segment of the pattern), some fine sand will always be present (if available to the stream) regardless of how fine the rest of the sediment might be. Sediments that fall into the QR segment (Md in the range 100/i to 200/i) are the best sorted; they fall closest to the C=Md line in figure 9, and their curves in figure 10A have the steepest slope. As the stream increases in competence it is able to transport coarser particles (PQ segment) ; but the bulk of the sediment tends to consist of particles of the optimum hydrodynamic size—125/t-500/x. Provided that the appropriate particle sizes are available, these three segments—RS, QR, and PQ, Figure 9.—CM patterns. After Passega (I960, p. 1734). Figure 10.—Particle-size-distribution curves (probability scale) of sediments deposited by (A) tractive currents and (B) turbidity currents, implied by I'assega’s CM patterns. should be characteristic of all tractive sediments. They reflect the same hydrodynamic circumstances as those Inman used to explain the relations between median size and sorting (fig. 8A). The OP and NO segments are not characteristic of all tractive sediments but are said by Passega to represent special conditions. “In the OP part, the proportion of rolled grains increases, mid the ON segment corresponds almost uniquely to a deposit of rolled grains” (Passega, 1960, p. 1735). These two segments did not appear in the sediments transported by the Mississippi, Enoree, and Niobrara Rivers or in the other tractive sediments described by Passega in 1957 (p. 1951, 1961-1963). Apparently, these segments of the pattern represent winnowed or reworked sands and gravels or sediments with restricted sources. Passega also suggested that points representing the Vleposits of turbidity currents might fall into a characteristic pattern parallel to the C=Md line (enclosed by dashed lines in fig. 9). The distance of the pattern from the C—Md line is said to be a direct fund ion of the density of the current. This implies that the cumulative curves representing the coarser halves of samples of sediments deposited by turbidity currents of similar density are parallel to one another (fig. 10Z?)—that is, as long as the current density remains constant, the sorting of the coarser half remains constant regardless of the size of C or Md. As represented in a CM dia-MECHANICS OP AQUIFER SYSTEMS C16 Figure 11.—CM patterns of modern surficial alluvial-fan deposits, Los Banos-Kettleman City area. After Bull (1962, p. 214). Tractive pattern enclosed by solid line; mudflow deposits inside dashed line. gram, sediments with poorer sorting are associated with currents of greater density (Passega, 1957, p. 1967). CM patterns prepared by Bull (1962) from analyses of sediments deposited in 1957-58 on alluvial fans in the Los Banos-Kettleman City area add support to Passega’s ideas. Bull found (fig. 11) that samples of stream-channel and braided-stream deposits fell into the PQB segment of a tractive pattern. Mudflow deposits fell into a pattern nearly parallel to the C=Md line—as one might have predicted from Passega’s observations on what he supposed were turbidity-current deposits. The distance of the mudflow pattern from the C=Md line supports Passega’s proposed relation between current density and sediment sorting. INTERRELATIONS OF PARTICLE-SIZE MEASURES IN CORED SEDIMENTS Figure 12 shows graphs of median diameter against the coarsest percentile (C), sorting, and skewness for the flood-plain and alluvial-fan deposits of the Los Banos-Kettleman City area. Not included in the graphs are samples of sediments that are cemented or that contain interlaminations or other inhomogeneous mixtures of different-sized particles. Lacustrine sediments are not included because the identification of some of the deposits as lacustrine is questionable. Deltaic sediments are not included because too few samples of homogeneous material are available to show significant variations in the particle-size measures. Quartile deviation (QD *) is used to represent sorting. Two measures of skewness are used—Bowley’s measure (Skqt/QDt, used so far in this report) and a measure of absolute skewness, Skq*. The relation of Skq$ to the log io Sk measure is shown in the two calibrated FLOOD ALLUVIAL PLAIN FAN MEDIAN DIAMETER, IN MICRONS EXPLANATION SOURCE o • + Sierra Nevada Diablo Range Mixed Figure 12.—Median diameter against coarsest percentile, sorting, and skewness in flood-plain and alluvial-fan sediments, Los Banos-Kettleman City area.PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C17 ordinates of figure 8B; note that positive values of Skq^ correspond to negative values of log i0 Sk. These measures are defined in more detail on pages C49-C50. FLOOD-PLAIN SEDIMENTS The CM pattern for the flood-plain sediments of the Los Banos-Kettleman City area (upper row, left col., fig. 12) at first glance seems to be a scatter of points roughly parallel to the C—Md line. Judging from the CM pattern, the sorting is slightly poorer in the finer sediments (points generally farther from the C=Md line), but the degree and variability of the sorting of the coarser halves of the sediment do not change markedly with median diameter. A closer look at the pattern shows most of the scatter to be related to the samples of sediments from the Sierra Nevada (open circles). The distribution points representing flood-plain sediments from the Diablo Range (dark circles) — except for the two samples having C values slightly greater than 1,000/t and Md values slightly less than 62/t—could be interpreted as the PQRS segments of a tractive pattern. These observations suggest some kind of source-related control on the regularity of the relations between median diameter and sorting: perhaps a more uniform mode of transportation from the west side of the valley, or some differences in the disintegration and weathering of the different rock types represented on the two sides of the valley. The relation of median diameter to quartile deviation in the flood-plain sediments is shown in the second row, left column, figure 12. Here also, the sediments derived from the Sierra Nevada show the greater scatter, but not as much so as in the CM pattern. The sediments fall generally into two groups, one of fairly well sorted sands and another of less well sorted finer sediments. No consistent variations with size or source area can be seen in the graphs of median diameter against skewness (third and fourth rows, left col., fig. 12). The lack of clear relations between the particle-size measures probably reflects the diversity of the sediments that have been included in the category of flood-plain deposits. The category is a broad one, including sediments laid down in the channels of perennial streams as well as on the overflow lands associated with the valley drainage system under more humid conditions than exist today. This means that pond and small-lake deposits have been lumped with the deposits of more active fluvial systems. ALLUVIAL-FAN SEDIMENTS The alluvial-fan deposits, which came from a single source area and were deposited under a more uniform set of conditions than the flood-plain sediments, show more consistent relations between the particle-size measures. The CM pattern of the alluvial-fan sediments (upper row, right col., fig. 12) seems to correspond to the RS segment of a tractive pattern. The sorting of the coarser half of the sediments varies directly with the median diameter; or, expressing the relation another way, regardless of the average particle size (in the Md range from 1/t to 250/i), some fine to medium sand is always present. A PQ segment is probably part of the complete CM pattern of the alluvial-fan deposits, but no particle-size analyses of the appropriate sediments were made. The coarsest sediments were not available for analysis (p. C48). From visual inspection of the coarse alluvial-fan sediments that were recovered but not analyzed, I have the impression that their C values can be as coarse as 16,000/i, whereas their median diameters lie fairly consistently in the fine- to medium-sand range, 125/u, to 500/i. Had the coarser samples been analyzed, a PQ segment probably would have appeared in the pattern. This supposition is reinforced by Bull’s CM patterns of coarser grained alluvial-fan sediments (fig. 11). The relation between median diameter and quartile deviation in the alluvial-fan sediments (second row, right col., fig. 12) is similar to that in the flood-plain sediments, except that the sorting of the finer grained alluvial-fan sediments seems to be poorer. The mean quartile deviation of sediments with medians finer than 62/i is about 2.0 in the alluvial-fan deposits, compared with 1.5-1.7 in the flood-plain deposits. Whereas the sorting of the coarser half of the sediments seems to change progressively with Md, the quartile deviation shows no consistent variation in the Md range from 4/i to 62/i. The CM pattern and graph of Md versus QD6 for the alluvial-fan sediments may be partly misleading. Many (but certainly not all) of the fine-grained alluvial-fan sediments contain clay and silt that were apparently transported and deposited in sand-sized aggregates (fig. 4). Many of these aggregates must have been broken up during size analysis and were recorded as smaller particles than they were when deposited (Bull, 1964c). This would affect the measurement of Md and QD# but not the measurement of C. That is, some of the sediments probably were better sorted and had coarser medians when deposited than is indicated in the graphs, but they still should fall into the RS segment of a CM pattern. Skewness seems to vary fairly consistently with Md in the alluvial-fan sediments of the Los Banos-Kettleman City area. The patterns of both relative and absolute skewness (bottom two rows, right col., fig. 12) showC18 MECHANICS OF AQUIFER SYSTEMS a progressive increase in skewness between Md values of Ifi and 62/u Combining the impressions from both measures of skewness, the alluvial-fan sediments are least skewed when their median diameters fall into the coarse-clay to fine-silt or fine- to medium-sand categories (2/i-8/i or 125/»-500/t). Mixtures of sand and finer materials (medians near 62/t) have the most skewed distributions. This is similar in general to the relations between median size and skewness summarized in figure H/i. CLAY MINERALS AND ASSOCIATED IONS CLAY MINERALS AXI) THEIR ASSMHBLAGBS The principal clay mineral in the Los Banos-Kettle-man City area is montmorillonite. Subsidiary clay minerals present are illite and chlorite, and lesser amounts of a kaolinite-type mineral, mixed layer mont-morillonite-illite, and a low-grade illite-montmoril-lonite mixture. The distribution of clay minerals in the four principal cores is shown in figure 13. The clay minerals in Recent sediments carried or deposited by the streams that flow into the area from the Diablo Range are shown in figure 14. The detailed results of the clay-mineral analyses of 101 samples—85 from the deep core holes and 16 from streams and alluvial-fan deposits to a depth of 70 feet— are given in tables 11 and 12. Assuming that the 85 samples are representative, the average clay-mineral composition of the sediments of Pliocene to Recent age, of the Los Banos-Kettleman City area is approxi- mately— ('lajf mUmermlt Permit Montmorillonite_________________________________ 70 Chlorite_________________________________________10 IUite__________________________________________ 10 Kaolinite-type mineral__________________________ 5 Mixed-layer montmorillonite-illite and low- grade illite-montmorillonite__________________ 5 The identification criteria for these clay minerals and the means of estimating their relative proportions are given on pages C67-C71. Two principal assemblages of clay minerals are found in the sediments of the area. Most of the stream and subsurface sediments contain an assemblage consisting, in decreasing order of abundance, of montmorillonite, type-B chlorite, illite, kaolinite-type mineral, and low-grade illite-montmorillonite (figs. 13,14). This assemblage seems to be derived mainly from the sedimentary and volcanic rocks (Cretaceous through Pliocene in age) that crop out along both sides of the San Joaquin Valley and from the weathered granitic and metamor-phie rocks that crop out in the Sierra Nevada and its foothills. The second assemblage—illite, mixed-layer montmorillonite-illite, type-A chlorite, and subsidiary montmorillonite—is found only in Little Panoche Creek and its alluvial fan. I suspect that this assemblage is derived mainly from the slightly metamorphosed and locally sheared gray wackes and shales of the late Mesozoic Franciscan Formation. It resembles closely the assemblage of clay minerals found in weathered rocks of the Franciscan Formation in the San Francisco area (Schlocker, Julius, oral commun., 1962). The proportion of the Little Panoche drainage basin underlain by the Franciscan Formation—41 percent—is more than twice the proportion underlying the drainage basins of the other principal streams in western Fresno County (Davis, 1961, p. B-7). Another 34 percent of the Little Panoche drainage basin is underlain by continental deposits derived mainly from the Franciscan Formation (W. B. Bull, written commun., 1964). The change in clay-mineral assemblages at some depth between 230 and 375 feet in the Oro Loma core (fig. 13) marks the extension of the Little Panoche Creek fan to this point in the valley. The predominance of montmorillonite in the first assemblage, and in the assemblages in the sediments that lie beneath the other areas of land subsidence in central California, is an important factor in the compaction behavior of the sediments. Experimental studies, summarized in the earlier paper in this series (Meade, 1964, fig. 4), have shown that montmoril lonitic clays are more compressible than illitic or kaolinitic clays. The presence of montmorillonites in these sediments probably contributes to the intensity of their response to changes in effective overburden load. SOCRCBS OK CLAY MDiRRAIS SOURCES OF ■ORTMORILLOXTTE Comparison of figures 3 and 13 shows that the clay-mineral assemblages derived from both rides of the valley are virtually identical. Montmorillonite predominates in both. The soils and sedimentary rocks of the Diablo Range source area must, contain a large proportion of montmorillonite, judging from the clay-mineral assemblages being carried by most of the streams entering the Los Banos-Kettlcman City area from the southwest (fig. 14). Some of this montmorillonite may be forming in the soils, and some of it may represent the alteration of volcanic material within the sedimentary rocks Yul can ism was widespread and frequent in central California during Mesozoic and Tertiary times (Jenkins, 1948; Lerbekmo, 1961; Taliaferro, 1943, p. 150); vol-DEPTH, IN FEET BELOW LAND SURFACE PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA 0 5 10 1 ____I______i ORO LOMA CORE CLAY MINERALS (ESTIMATED PARTS PER TEN) 0 5 10 O 5 10 ii____ii______■ i______ii_____i MENDOTA CORE CANTUA CREEK CORE 0 5 10 II_____i_______j HURON CORE Low-grade illtte-montmorillonite Chlorite l» Kaolinite-type mineral Chlorite and kaolinite-type mineral (undifferentiated) Fiema IX—day minerals in cored sediments, Eos Banos-Kettleman City1 area. Trace amounts, ptm in table 11. not Qhustrated. Wbere two analyses were made less than 10 feet apart in cores, they were combined and illustrated as a single analysis. Twenty-fire of illustrated analyses for Mendota and Huron cores were made by J. C. Hathaway. II- C. Starkey, and & W. Chine C19C20 MECHANICS OF AQUIFER SYSTEMS 120°30' 120°00' Figure 14.—Sampling sites for clay minerals in Recent surface alluvial sediments, Los Banos-Kettleman City area. Samples 3, 4, 7, and 11 collected by W. B. Bull. canic minerals and rock fragments are significant constituents of many of the sediments deposited then. Much of the montmorillonite in the valley sediments from the Diablo Range may well have been derived from material that was deposited in and with older sedi- ments as volcanic debris, altered to montmorillonite, and then eroded and redeposited as montmorillonite in the valley. However, no clay-mineral analyses of soils and rocks of the Diablo Range source area are available to substantiate this supposition.PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C21 A little montmorillonite has formed in the sediments from the Diablo Range since they were deposited. Some of the sand grains, especially those in the lowest 500 feet of the Mendota core, are coated with a material that colors them pale blue. Similar material has been identified in Pliocene sandstones from central California as montmorillonite that is derived from alteration of the volcanic detritus of andesitic composition that comprises large proportions—in some places nearly all—of these sandstones (Lerbekmo, 1957, 1961). In the sediments of the Tulare Formation and younger alluvium from the Diablo Range, however, the volcanic detritus is always mixed with such nonvolcanic constituents as serpentine and reddish chert, suggesting that these sediments are mixtures of reworked older volcanic sands and other materials. Because the coatings cover nonvolcanic as well as andesitic grains in the cored sediments, the coatings must have formed since the sediments were deposited. Although montmorillonite has been formed within the sediments, no progressive increase in montmorillonite (relative to the other clay minerals) with depth of burial is evident (fig. 13). Perhaps the transformation of volcanic material to montmorillonite is not restricted to the sediments buried in the valley but is going on in the sediments and soils of the Diablo Range source areas at a similar or even greater rate. The source of the montmorillonite in the sediments from the Sierra Nevada is uncertain. According to R. J. Janda (written commun., 1964, 1965), the principal clay mineral in the soils and alluvium of the upper San Joaquin River basin is kaolinite; subsidiary minerals are halloysite, vermiculite, montmorillonite, and illite. In many of these soils and sediments, montmorillonite is totally absent. Assuming that this represents the assemblage of clay minerals that the weathering of the granitic rocks in the Sierra Nevada has produced since Pliocene time, why do the Sierra-derived sediments of the valley contain an assemblage of clay minerals that is dominated by montmorillonite? One possible source of the montmorillonite is the belt of metamorphic rocks in the western foothills of the Sierra Nevada. Perhaps montmorillonite has formed in the soils developed on these rocks and has been contributed to the streams that drain the Sierra in amounts sufficient to dilute the kaolinite-dominated assemblage contributed by the granitic terrane of the Sierra proper. Another possible source of the montmorillonite is the Coast Ranges. The Sierra-derived sediments were designated as such on the basis of the assemblages of sand- and pebble-sized constituents. I assumed that the clay constituents of the same sediments also came from the Sierra. This may not necessarily be so. In the Los Banos-Kettleman City area, the cored sediments whose source is designated as Sierran were deposited on flood plains, in lakes, or in deltas. It is entirely possible that any, or all, of these deposits contain clay from the Diablo Range, even though none or very few of the sand and gravel constituents of these sediments came from the west. In the Tulare-Wasco area the fact that the shallow-marine sediments contain proportionately more montmorillonite than the alluvial-fan sediments (figs. 17, 24) may be indicative. That is, the marine deposits may have received clay that originated in the Coast Ranges and was moved in suspension to the east side of the shallow sea that occupied the southern part of the San Joaquin Valley at the time. The predominant clay mineral in the alluvial-fan deposits of the Tulare-Wasco area, however, is also montmorillonite. And, because these alluvial-fan sediments must have been derived exclusively from the Sierra, all the montmorillonite cannot have come from the Coast Ranges. One must consider also that the montmorillonite in the Sierra-derived deposits may have formed by the alteration or transformation of other minerals soon after they were deposited in the valley. At least two possible sources, kaolinite and biotite, are worth considering. Montmorillonite may have been formed from the kaolinite, either in soils that developed on the alluvial fans or as a diagenetic transformation in the high-pH environment of the valley sediments (see the pH measurements listed on p. C72 and in tables 11-13). The cored sediments, however, contain no evidence of such changes in the form of increasing proportions of montmorillonite and decreasing kaolinite with increasing depth of burial. The mechanism of such a transformation, involving a change from a two-layer structure to a three-layer structure, would seem to require energies that are not generally available in soils or in sediments buried under a few tens of feet of overburden. The degree of crystallinity of the kaolinite, on the other hand, is poor, and perhaps the transformation to montmorillonite could take place at low energy levels. The montmorillonite may have been formed from biotite in the sequence: biotite—»vermiculite—»mont-morillonite. Vermiculite is a common product of the weathering of biotite in California soils (Barshad, 1948). And montmorillonite could easily be formed from vermiculite with little change in the structure of the basic mineral lattice—the two minerals are so similar that distinction between them is often difficult. Biotite, in sand-sized flakes and books is a common constituent (2-5 percent) of the Sierra-derived sediments— probably more biotite than kaolinite, in terms of total sediment, is contributed by the Sierra to the valley. Al-C22 MECHANICS OP AQUIFER SYSTEMS teration of some of the biotite (especially in the alluvial-fan sediments of the Tulare-Wasco area) from greenish black to golden yellow indicates that it has lost some of its identity as biotite. Vermiculite has been identified in the clay-mineral fractions of some of the sediments of the Pixley core from the Tulare-Wasco area, and it may be present in sediments in some of the other cores as well (but impossible to distinguish in the presence of the much greater proportions of montmorillonite). But no progressive alteration of biotite or change from vermiculite to montmorillonite has been observed with increasing depth of burial. The question of the origin of the large proportions of montmorillonite in the valley sediments from the Sierra Nevada—in both the Los Banos-KettJeman City and the Tulare-Wasco areas—remains unanswered. One cannot choose the best hypothesis or combination of hypotheses on the basis of the evidence that is now available. SOURCES OF OTHER CUT XXHERALS Mixed-layer montmorillonite-illite seems to be derived entirely from the Diablo Range, probably from rocks of the late Mesozoic Franciscan Formation. It is a significant constituent of sediments in modem Little Panoche Creek, in the upper third of the Oro Loma core, and in the coarse lens of sediment at depths between 1,000 and 1,200 feet in the Mendota core. Illite and chlorite are ubiquitous, but variations in their crystallinity are helpful in delineating their sources Well-crystallized illite and type-A chlorite occur in conjunction with mixed-layer montmorillonite-illite, and seem to be derived from the Franciscan Formation. Type-B chlorite and less well crystallized illite seem to be derived mainly from Cretaceous and Tertiary sediments of the Diablo Range and Sierra Nevada foothills The kaolinite-type mineral or minerals could have come from many sources. Three possible sources of aluminum-rich kaolinite are weathered silicic intrusive rocks of the Sierra Nevada, hydrothermal alteration zones associated with quicksilver deposits in the Diablo Range (Eckel and Myers, 1946; Tates and Hilpert, 1945), and “anauxitic" Eocene sediments along the west side of the northern San Joaquin Valley (Allen, 1941; Briggs, 1953, p. 39-41). Serpentine minerals have kaolinite-type structures, and they may be present in the samples; serpentine bodies crop out in the drainage basins of all the major creeks that flow from the Diablo Range into tbe Los Banos-Kettleman City area. An intriguing possibility is that some of the kaolinite-type material is derived from the weathering of chlorites. Nelson and Roy (1954,1958) have shown that the polymorph of chlorite stable at low temperatures might have a kaolinite structure, and a mineral with a chloritic composition and kaolinite structure has been found in a low-temperature environment by Sigvaldason and White (1961, p. D-117, D-119). Considering that much of the chloritic material in the Tulare Formation and younger sediments of the valley represents chlorite from older sediments that has been through two or more periods of degradational weathering, the sequence, of minerals represented as A, B, and G in figure 40 may represent a gradation from well crystallized 14—A chlorite to poorly crystallized 7-A chlorite. TOTAL CLAV-HINERAL CONTENT OF SEDIMENTS The total amount of clay-mineral material in the cored sediments of the Los Banos-Kettleman City area is about 15 percent, and the total amount of montmorillonite is about 10 percent. This estimate was derived by a combination of visual examination and particle-size analysis. The visual examination was made with a petrographic microscope and an nil-immersion lens and consisted of point counts (100 points each) of specimens of 20 fine-grained sediments that had been stained with a mixture of malachite green and nitrobenzene. Malachite green stains clay minerals selectively without staining nonclay minerals (Mielenz and King, 1951, p. 1217). The point counts yielded a rough estimate of the proportion of clay-mineral material in each of the 20 sediments. Particle-size analyses were also made for these 20 sediments—the core-hole sediments in table 6. The particle-size analyses were compared with the point counts to determine the percentile (particle diameter) that corresponded to the proportion of clay minerals estimated visually: say, for example, the visually estimated proportion of clay minerals was 40 percent, then the particle diameter that was coarser than 40 percent of the sediment was taken from the size-distribution curve. For the 20 sediments, the geometric mean of these particle diameters was 3.0/» (8.4<£) and their standard deviation was about 1.5/i (0.7). The weight percent finer than 3.0/1, therefore, was taken as the proportion of clay-mineral material in a sediment. The next step consisted of determining the percents finer than 3.0/i in the 305 sediments whose particle sizes were discussed in the previous section (listed in table 5). The mean of these was 20 percent. This estimate was adjusted to 15 percent to allow for the coarser sediments that were not recovered during the coring operations. IONS ASSOCIATED WITH CLAY MINKRAIjS The principal ions adsorbed by the clays and in waters associated with the clays are calcium, magne-PETROLOGY, SEDIMENTS UNDERLYING AREAS OP LAND SUBSIDENCE, CENTRAL CALIFORNIA C23 sium, sodium, bicarbonate, sulfate and chloride. These are listed in tables 11 and 12; the procedures used in their determination are described on pages C71-C72. Figure 15 represents the cations adsorbed by the days in sediments from the four principal streams and the four core holes. The percentages illustrated were adjusted by subtracting the equivalent of the total anions from the total calcium ions; this involves the assumptions (not necessarily true) that all the soluble salts in these sediments are calcium salts and that none of the anions are adsorbed by the clays. The accuracy of figure 15 is subject to the doubts and limitations discussed below, but the general picture is valid. The adjusted sums of exchangeable cations in these samples, with one exception, are greater than the determined cation-exchange capacities. Several hypotheses to explain this disparity are listed below, but one cannot choose between them on the strength of the available evidence. 1. The adjustment is only a partial correction because the solubility of the principal salts in these sediments, calcite and gypsum, is greater in Nil 4( ;I solution (in which the adsorbed cations were determined) than in hot water (in which the soluble anions were determined). 2. The cation-exchange capacities, as determined, may be lower than the actual capacities because some of the ammonium ion that was added to displace the naturally held exchange cations may have been fixed so strongly on the clays that it was not removed by the alcohol-distillation procedure used in the analysis (Richards, 1954, p. 20). 3. The disparity may be related to differences in pH between the natural environment and the laboratory. The natural clays exist in an alkaline environment (pH>7), but their exchange capacities were determined at neutrality (pH=7). Kelley (1957, p. 473) says that cations are adsorbed from chemically alkaline solutions in greater quantities than from neutral solutions; and, as the pH of a clay-water suspension is lowered in the laboratory, the excess cations adsorbed at higher pH tend to hydrolize off the clays. Supporting evidence for this hypothesis is given by Pratt (1961) and in the titration curves summarized by Grim (1953, p. 130). The single exception to the apparent excess of exchangeable cations over exchange capacity is the sediment from 1,801 feet in the Huron core. The sample contained pyrite (about 1 percent) and bituminous-appearing organic material (several percent). The pH of the hot-water leachate was 6.7, and the only anion determined in significant quantity was sulfate. Some of the exchange positions may have been occupied by hydrogen, which was not determined. EXCHANGEABLE CATIONS IN KODEBN STREAM SEDIMENTS Calcium is by far the most abundant of the cations adsorbed by clays in the streams, although it is not the most abundant cation in solution in the stream waters. The cation composition of water samples from Little Panoche and Panoche Creeks and of sediments that were in approximate contact with these waters at the time they were sampled are given below. The cations conform to the generally recognized sequence of preferential adsorption at low electrolyte concentrations, Ca>Mg>Na (Carroll, 1959, p. 749). Ca Mg Na K Total dissolved solids (ppm) Cation exchange (percent of total cation equivalents) capacity of day- mineral assemblage (meq/lOOg sample finer than 3p) LHU I'avocke Crtxt In solution 35 24 39 2 432 Adsorbed by clays in creek bed 71 29 0 0 68 PmnocMe Creek In solution 1 32 29 38 1 1, 310 Adsorbed by clays in creek bank 84 16 0 0 116 ■ More details of this analysis given by Davis (1961. p. 27, sample collected Mar. 17, 1958). KltCHAWfiBAlILK CAIIOV8 Uf SUBSURFACE 8KDTH KHT8 Several features of the distribution of cations in subsurface sediments are apparent in figure 15: a preponderance of calcium, a downward increase in adsorbed sodium, and, in all but the Oro Loma core, a downward decrease in adsorbed magnesium. The increase in adsorbed sodium is probably related to the downward increase in the sodium content of the ground water in the sediments, as is shown by the following data summarized from Davis mid Poland (1957, p. 450-462). Depth interval Total dissolved solids (ppm) Sodium (percent of total cation equivalents) Surface to about 250 ft 3,000 1,500 800 35 250 ft to top of Corcoran Clay Member 55 Bottom of Corcoran Clay Member to base of fresh water 75 NaCl-water zone (below bottoms of core holes) 14,000? Very high Although the percent sodium in the deeper fresh water averages about 75, the percent of adsorbed sodiumC24 MECHANICS OF AQUIFER SYSTEMS never seems to exceed 35. The downward decrease in adsorbed magnesium is also related to a change in the cation composition of the ground water. Analyses given by Davis and Poland (1957, p. 454-455) show an average percent magnesium of 23 in the water above the Corcoran Clay Member and 6 in the water below the Corcoran. SEDIMENTS IN THE TULARE-WASCO AREA The sediments whose compaction accounts for the land subsidence observed in the Tulare-Wasco area include both marine and nonmarine deposits. They were derived from the Sierra Nevada, which borders the area on the east. The oldest of these sediments are probably upper Miocene; the youngest are Recent. The marine sediments have been assigned to the Santa Margarita Formation as used by Diepenbrock (1933) and an overlying upper Pliocene marine unit. Most of the land subsidence observed to date has been due to compaction of the nonmarine sediments (B. E. Lofgren, oral commun., 1962). These sediments were studied in two cores. Locations of the core holes, both in southwestern Tulare County, are shown in figure 16. Other details of the coring are given in table 1. Note that the average core recovery was better in these sediments than it was in the sediments of the Los Banos-Kettleman City area or the Santa Clara Valley. Two other reports bear on the depositional history of the sediments of the Tulare-Wasco area. Klausing and Lohman (1964) describe the upper Pliocene marine unit, as cored in the Richgrove hole. B. E. Lofgren and R. L. Klausing, in a report on land subsidence in the Tulare-Wasco area, Calif, (in preparation as Prof. Paper 437-B), describe briefly the geologic units and structure. SOURCE OF SEDIMENTS The sediments represented by the Pixley and Rich-grove cores have come chiefly, if not entirely, from the Sierra Nevada and its foothills. Lacustrine sediments in the Pixley core and marine sediments in the Rich-grove core may have received contributions from the non-Sierran drainage basins, but their sand and pebble constituents show little or no evidence of it. The silts, sands, and gravels are all arkosic, consisting mainly of quartz, feldspar, and fragments of granitic rock. The principal accessory constituents, which usually amount to 5-15 percent of the sediments, are biotite and green hornblende. These minerals reflect the assemblage of minerals in the granitic rocks of the Sierra Nevada. Minor constituents of the sediments are dark fragments of metamorphic rocks, mainly quartzite and slate plus a little serpentine, which probably were derived from the metamorphic terrane in the foothills of the Sierra. A little volcanic detritus was also deposited with the sediments. Glassy basalt, in pebbles and granules, was found in some of the coarser sands at depths between 1,840 and 1,750 feet in the Richgrove area. Rhyolitic glass (index of refraction between 1.50 and 1.51), in silt-sized particles, was found at a depth of 1,058 feet— partly mixed with other detritus and partly concentrated (more than 90 percent glass) in a bedded deposit. I. E. Klein reported finding a thin layer of pumice at a depth of 540 feet in the Pixley core (B. E. Lofgren, written commun., 1964). Except for these minor occurrences, no other direct evidence of volcanic activity was found in the sediments. TYPES OF DEPOSITS The main distinction to be made in the sediments cored in the Tulare-Wasco area is between marine and nonmarine deposits. The evidence for the existence of both types of deposit is quite clear. The exact point of the transition from marine to nonmarine conditions is somewhat less so. The most detailed petrologic study was done on the Richgrove core because it contained both types of deposits. The Pixley core contains only nonmarine sediments. The distribution of deposits in the cores is shown in figure 17. The pertinent evidence gleaned from the Richgrove core and the conclusions reached from it are given in table 4. Inferences about the origins of the nonmarine deposits are based on the criteria used in the Los Banos-Kettleman City area. MARINE DEPOSITS The marine deposits in the Richgrove core can be divided conveniently into two units—a well-sorted sand (below 1,900 ft) and a fine-grained siltstone (1,700 to about 760 ft)—with 200 feet of transitional sediment between them. The well-sorted sand has been correlated by subsurface mapping with the Santa Margarita Formation as used by Diepenbrock (1933) of Miocene age (Klausing and Lohman, 1964, p. D-14). On the basis of a study of diatom assemblages by Lohman, the siltstone unit has been assigned to the upper Pliocene and may be the equivalent of part of the San Joaquin Formation exposed on the west side of the San Joaquin Valley, and the siltstone-sand transitional sediments have been assigned tentatively to the Pliocene (?). The marine sediments probably were deposited in shallow water under mildly reducing conditions. The depth of water is suggested by the remains of shallow-water mollusks and Foraminifera that were found in the siltstone-sand transitional sediments. It is also suggested by some of the textural characteristics of thePETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C25 0 50 100 1 _______l____________i EXCHANGEABLE CATIONS (ADJUSTED PERCENT EQUIVALENTS) 0 50 100 0 50 100 1 ____i______i i______i______i 0 50 100 1 _________i__________i STREAM SAMPLES LITTLE PANOCHE CREEK PANOCHE CREEK CANTUA CREEK LOS GATOS CREEK CORE-HOLE SAMPLES ORO LOMA MENDOTA CANTUA CREEK HURON 0 -i 500 1000 CO x H 0. 1500 J 500 - 1 1000 - 1500 EXPLANATION Egg Calcium □ Magnesium Sodium 2000 - 500 - ■mim 1000 1500 - WBfSSSSI 2000 Eggsr Figcke 15.—Cations adsorbed by clay minerals in principal streams and cores, Los Banos-Kettleman City area. Determined by H. C. Starkey. sediments. The good sorting of most of the sands in the 2,200- to 1,700-foot and 1,050- to 760-foot intervals, and the small-scale separation of sand and finer material in the siltstones in the 1,570- to 1,050-foot interval (described under “Other features” in table 4) suggest that a gentle winnowing process operated periodically during the deposition of these sediments. Reducing conditions are suggested by the good preservation of plant remains and by the ubiquitous presence of iron sulfides. The upper boundary of the marine siltstone unit is not so abrupt as indicated in table 4 or in figure 124.2C26 MECHANICS OF AQUIFER SYSTEMS Figure 16.—Tulare-Wasco area showing locations of core holes. of the paper by Klausing and Lohman (1964). Although the resistivity log (shown in fig. 22) shows an abrupt transition at a depth of 744 feet, visual examination of the sediments suggests a more gradual transi- tion. In the 785- to 744-foot interval, interbedding of poorly sorted clayey silt with t he massive si It.stones suggests a gradual and fluctuating departure of the sea rather than a sudden and abrupt withdrawal.PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C27 PIXLEY CORE SOURCE TYPE OF DEPOSIT Sierra - Nevada AF AF EXPLANATION TYPE OF DEPOSIT AF, Alluvial fan FP. Flood plain LA, Lacustrine RICHGROVE CORE SOURCE Sierra Nevada TYPE OF DEPOSIT AF 500 FP 1000 LlI o < u. cr D CO O z < _J £ o Shallow marine 1500 ? X I-Ql id O 2000 Figure 17.—iSource and principal types of deposits represented by sediments cored in the Tulare-Wasco area. ALLUVIAL-FAN DEPOSITS Most of the nonmarine sediments in the two cores were deposited on alluvial fans. The uppermost 620 feet of the Richgrove core and most of the Pixley core consist of alluvial-fan deposits, whose characteristics are given in table 2. The modern Tulare-Wasco area, like the Los Banos-Kettleman City area, is an area of alluvial-fan deposition. The alluvial-fan deposits in the Tulare-Wasco area differ from those in the Los Banos-Kettleman City area in two ways. First, they are coarser grained, reflecting the generally larger size of material supplied by the Sierra Nevada source area. They contain few fine clays such as are common in the alluvial-fan sediments in the Los Banos-Kettleman City area. And they do not contain clay aggregates of the type illustrated in figure 4. The second main difference is the evidence of more extensive soil-forming processes in the Tulare-Wasco area. Biotite has been intensely weathered: originally black flakes and books have gone partly or completely to fragile golden-yellow flakes. Soil textures (fig. 18)— mainly cavities lined with carbonaceous material, opaline material, or clay in oriented films (like those described and named “cutans” by Brewer, 1964, p. 205-233)—suggest that organic and mineral material had been moved about within the sediments since they were Figure 18.—Photomicrographs of soil textures in alluvial sediment from depth of 232 feet in Richgrove core, Tulare-Wasco area. Long dimension of each photograph is about 1,000/4. Uppert Cavities (Cv) lined with clay. Layered clay (Cy) shows preferred orientation, presumably resulting from successive depositions on walls of cavity. Lower, Cavities (Cv) lined with clay and carbonaceous matter (black). Grain (Gr) also surrounded by clay. deposited. The development of these features suggests that the alluvial-fan sediments in the Tulare-Wasco area have accumulated more slowly than those across the San Joaquin Valley in the Los Banos-Kettleman City area. LACUSTRINE ANI> FLOOD-PLAIN DEPOSITS The lacustrine layer indicated in the Pixley core in figure 17 is the Corcoran Clay Member of the Tulare Formation, identified on the basis of its fine grain size and bluish-gray color and by subsurface correlation across the valley. The flood-plain deposits that lie below the alluvial-fan sediments in both cores were identified on the basis of criteria in table 4 and by their similarity to flood-plain deposits in the Los Banos-Kettleman City area. They may include some minor lacustrine deposits. PARTICLE SIZES The study of particle sizes in the Tulare-Wasco area is based largely on 157 samples from the two core holes. 232-511 O—66—'—2Table 4.—Evidence for conditions of deposition represented by sediments in Richgrovc core, Tulare-Wasco area Depth below land surface (feet) Lithologic unit Particle-size characteristics Other features Organic remains Chemical indicators Inferred type of deposit Depth below land surface (feet) 500 — Sand, silt, and clay in beds 1-10 ft thick. Sand, silt, and clay mixed in varying proportions; poorly sorted. Some of silts and clays contain cavities, tubular or irregularly oblate, which are lined with carbonaceous material, opaline material, or clay. Sediments loose to friable. Minerals, especially biotite, weathered. No preferred orientation of clay-mineral particles (mean orientation ratio 1.1). Carbonaceous material in cavity linings or amorphous accumulations. Iron oxides, disseminated. Calcite in hard nodules or soft irregular accumulations; rarely cementing layers a few centimeters thick. Yellow brown. Alluvial fan (on basis of oxidized color, poor sorting of particle sizes, and cavities) — 500 Preferred orientation of clay-mineral particles (one sample with orientation ratio of 1.5). Iron sulfides associated with woody material. Calcite as above. Greenish to bluish gray. Flood plain — Transitional Siltstone, massive (virtually no visible bedding on small scale),hard (breaks with conchoidal or blocky fracture). Sand, loose. Preferred orientation of clay-mineral particles (mean orientation ratio 1.6). Woody material, in isolated well-preserved fragments as much as a few centimeters long, or disseminated in small flecks. Siltstone, fine to clayey, with a few sand grains; well sorted. Iron sulfides associated with woody material. Greenish to bluish gray. Presumably shallow marine 1000 — Sand, medium to fine, well-sorted. (on basis of lithologic similarity to underlying sediments) — 1000 Most of siltstone finely laminated: siltstone layers a few centimeters thick alternate with layers or discontinuous lenses, a few millimeters thick, of fine sand. Many sands contain oblate and rounded clasts of claystone as much as 2 centimeters across. Siltstone, hard; and loose sand. Preferred orientation of clay-mineral particles (mean orientation ratio 1.5). 1500 — Siltstone1 in beds 20-100 ft thick, intercalated with sand 2-15 ft thick. Siltstone, fine to clayey, with a few sand grains; well sorted. Sand, coarse to clayey, poorly sorted. Marine diatoms. Woody material as above. Iron sulfides disseminated in small grains or concentrated near organic material; occasionally replace diatoms; partly or completely oxidized to gypsum and iron oxide. Gypsum in especially high concentrations in some siltstones below 1200 ft. Greenish to bluish gray. — 1500 Siltstone, massive, hard. Sand, loose. Preferred orientation of clay-mineral particles (mean orientation ratio 1.7). Shallow marine Woody material as above. (mainly on basis of fossils) Siltstone1 and sand in beds 2-20 ft thick. Siltstone, fine to clayey, with a few sand grains; well-sorted. Sand, coarse to medium, well-sorted. Shallow-marine mollusks, Foraminifera, fish scales, crab(?) remains. Woody material as above. - 2000 — Sand, massive. Sand, coarse to medium, well-sorted. Sand, loose. Woody material in isolated fragments as much as a few centimeters long. Shell fragments. Iron sulfides associated with woody material, partly oxidized to gypsum and iron oxide. — 2000 1 Clays tone as logged from core inspection at drilling site and as listed by Klausing and Lohman (1964, fig. 124.2); particle-size analyses indicate siltstone. C28 MECHANICS OF AQUIFER SYSTEMSPETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C29 The number of samples analyzed from and the estimated mean particle size of the three principal lithologic units are summarized in the following table. The mean sizes Lithologic unit Depth interval Number Estimated mean particle size (microns) sampled (feet) of samples Recovered sediments Section as a whole Nonmarine and transitional 30- 785 121 20- 40 40- 80 Marine siltstone and interbedded sands 785-1, 900 28 16- 30 8- 16 Santa Margarita Formation as used by Diepenbrock (1933)- 1, 900-2, 200 8 250-500 250-500 of the sediments as a whole were estimated by comparing the mean sizes of the recovered sediments with the electrical-resistivity logs of the core holes. The difference between the mean size of the nonmarine sediments that were recovered and the size of the sediment particles in the nonmarine section as a whole is due to selective recovery, especially in the Pixley core. The difference in the marine siltstones and interbedded sands is due to selective sampling of the recovered core. Because the material was so uniform, the marine deposits were not sampled at close intervals. (See fig. 22 and table 8.) Selected percentiles, averages, and measures of sorting and skewness for each sample are given in table 8. The percentiles were interpolated by a digital computer from particle-size data provided by the Hydrologic Laboratory. The digital computer also determined the modal particle size and calculated the measures of sorting and skewness, which are defined on pages C49 and C50. Particle-size-distribution curves for some individual samples are presented by Johnson, Moston, and Morris (1967). In order that the size characteristics of the nonmarine and marine deposits might be considered clearly and separately, the particle-size analyses of the transitional sediments (depths between 785 and 744 ft in the Rich-grove core) have been left out of the discussions that concern figures 19-21, and 23. The transitional sediments are included, however, in fig. 22. PARTICLE SIZES OF NONMARINE SEDIMENTS Except for two samples from the lacustrine Corcoran Clay Member in the Pixley core, all the samples of nonmarine sediments represent alluvial deposits. The triangular plots of the proportions of sand, silt, and clay (fig. 19B, C) show that the nonmarine sediments are not so diverse in particle size as those cored in the Los Banos-Kettleman City area (compare with fig. 5). The bulk of the points in figure 195 and C fall into the silty-sand and sand-silt-clay categories. The clay content ranges between 10 and 35 percent in most samples. Sixty-eight of the samples of nonmarine sediments (all from the Richgrove core) contain some gravel, but only 14 of these contain 5 percent or more of material coarser than 2,000/*. In general, then, the nonmarine sediments of the Tulare-Wasco area seem to be heterogeneous mixtures of sand, silt, and, to a lesser extent, clay. This impression is supported by the measures of average size, sorting, and skewness (fig. 20). Most of the median and modal diameters fall into a fairly narrow range of sizes, as compared to the wider general range in the Los Banos-Kettleman City area (fig. 6). The most abundant size range, judging from the concentration of modal diameters, is 31/i to 62/*. As in the Los Banos-Kettleman City area, the degree of sorting ranges mostly from fair to poor, and the skewness of the particle-size distributions reflects a disproportionately large amount of fine-grained material. The sediments in the Pixley area probably are not so fine grained on the whole as one might infer from the distribution of median diameters in the recovered sediments. Although the core recovery at Pixley was good (table 1), part of the section—200 of the uppermost 260 feet—was not cored. According to the electric logs of the core hole (fig. 22), many of the coarsest sediments in the section are in the uppermost 260 feet. Most of these, therefore, were not sampled. The nonmarine sediments in the Richgrove core, on the other hand, were cored and sampled on a fairly representative basis. Although they do seem to 'be slightly coarser on the whole than sediments in the Pixley area, they are perhaps more representative than the sediments recovered at Pixley. PARTICLE SIZES OF MARINE SEDIMENTS In the unit of interbedded marine siltstone and sand that lies between depths of 785 and 1,900 feet in the Richgrove hole, the siltstones are in beds 20-100 feet thick, and the sands are mostly in layers 2-15 feet thick. The segregation into twTo types of sediments is not so well shown in figure 195 as it is in figure 21. The average diameters (median and mode) in this depth interval fall into two groups, one representing the siltstones and the other representing the sands. Because of selective sampling of the recovered core, however, the sands are overrepresented with regard to the siltstones. The highly skewed sediments—those with S/cq^/QD# values larger than 0.4—represent bulk analyses of siltstones that contain thin laminae (a few millimeters thick) of fine sand.C30 MECHANICS OF AQUIFER SYSTEMS A EXPLANATION MICRONS Gravel >2000 Sand 62-2000 Silt 4-62 Clay <4 CLAY SAND AND 25 50 75 SILT GRAVEL B CLAY GRAVEL CLAY SAND AND 25 50 75 SILT GRAVEL D CLAY GRAVEL „ E Figure 19.—Sand-silt-elay percentages of sediments cored in the Tulare-Wasco area. Based on data from the Hydrologic Laboratory of the U.S. Geological Survey, Denver, Colo. A, Nomenclature after Shepard (1954). B, Alluvial-fan sediments. C, Flood-plain sediments, plus two lacustrine sediments (indicated by arrows). D, Marine siltstones and interbedded sands. E, Santa Margarita Formation as used by Diepenbrock (1933).NUMBER OF SAMPLES PETROLOGY, SEDIMENTS UNDERLYING AREAS OP LAND SUBSIDENCE, CENTRAL CALIFORNIA C31 PIXLEY RICHGROVE CORE CORE ALL SAMPLES (121) 30 0 4 62 1000 4 62 1000 MEDIAN DIAMETER, IN MICRONS SAMPLES 193) WHOSE MODES COULD BE DETERMINED .Lfc_ 4 62 1000 4 62 1000 MEDIAN DIAMETER, IN MICRONS LlLL 4 62 1000 4 62 1000 MODAL DIAMETER, IN MICRONS SAMPLES (117) WHOSE OUARTILES COULD BE DETERMINED 30 30 Ljl, 4 62 1000 4 62 1000 MEDIAN DIAMETER, IN MICRONS U*. lA 30 0 +-r--0.4 QUARTILE DEVIATION (QD^) La 0 0.4 /S% \ ( 0.4 -0.4 QUARTILE SKEWNESS Figure 20.—Measures of average size, sorting, and skewness in nonmnrine sediments cored in the Tulare-Wasco area. MARINE SILTSTONES AND SANDS SANTA MARGARITA FORMATION ALL SAM PLES (36) 10 4 62 1000 62 1000 MEDIAN DIAMETER, IN MICRONS SAMPLES (32) WHOSE MODES COULD BE DETERMINED MEDIAN DIAMETER, IN MICRONS 0- 5 < to o: QJ CO 2 O MODAL DIAMETER, IN MICRONS SAMPLES (35) WHOSE OUARTILES COULD BE DETERMINED QUARTILE SKEWNESS Figure 21.—Measures of average size, sorting, and skewness in marine sediments from the Richgrove core, Tulare-Wasco area. The Santa Margarita Formation as used by Diepen-brock (1933), sampled at depths between 1,900 and 2,200 feet, is mainly a well-sorted sand. The eight samples whose characteristics are plotted in figures 19E and 21 seem to be representative of the cored intervals. SPATIAL DISTRIBUTION OF PARTICLE SIZES Figure 22 shows the variation in particle size with depth in the two cores and serves as a spatial summaryC32 MECHANICS OF AQUIFER SYSTEMS PIXLEY RICHGROVE CORE CORE MEDIAN DIAMETER, IN MICRONS MEDIAN DIAMETER, IN MICRONS 1 8 62 500 1 8 62 500 4000 UJ o < ti- er D cn Q Z < _l £ o _J LU CD Z I H 0- L±J D Figure 22.—Variations in particle size with depth, Tulare-Wasco area. Resistivity log is left column of each composite; range, from left to right, is 0—40 ohms m2/m. of some of the foregoing descriptions of size. As in figure 7, median diameter and resistivity indicate particle size. The types of deposits are also included. The preponderance of silt in the section between 1,900 and 744 feet in the Richgrove core is better shown in the resistivity log than in the distribution of median diameters; selective sampling for size analysis of this section gave excessive emphasis to the interlayered sands. Based on the trend of median diameters, the nonmarine sediments of the Richgrove core seem to coarsen progressively between about 750 feet and the land surface, but no clear systematic variation appears in the Pixley core. INTERRELATIONS OF PARTICLE-SIZE MEASURES Figure 23 shows graphs of median diameter against the coarsest percentile (C), sorting, and skewness for the alluvial-fan and shallow-marine deposits of the Tulare-Wasco area. Not included in the graphs are samples that are cemented or that contain interlaminations, or whose conspicuous soil textures indicate that material has been moved around since the sediment wasPETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C33 ALLUVIAL SHALLOW FAN MARINE 2 8 31 125 500 2000 2 8 31 125 500 2000 UJ O' I! > UJ > 0-6 —1 1—1—1—1—1—1—1—1— —I—1—1 1 1 1 1 1 1 • Q Q* v 0.4 • - • • -e- LlJ ^ - $2. 0.2 3 <*> 0 - • ••••> • • •• • • • • • • • • • -• • uj -0.2 * (/) -0.4 • 1 1 1 1 1 1 1 1 1 • • • 1 1 1 1 1—1—1—1—1— MEDIAN DIAMETER, IN MICRONS Figure 23.—Median diameter against coarsest percentile, sorting, and skewness in alluvial-fan and shallow-marine sediments, Tulare-Wasco area. deposited. Flood-plain and lacustrine deposits are not included because too few samples of homogeneous material are available. The measures of sorting (QD and skewness (Skq^/QD^, and Skq*) are defined on page C49. The reasons for attempting to graph these measures against median diameter were reviewed on page C13-C16. ALLUVIAL-FAN SEDIMENTS The relations between the particle-size measures in the alluvial-fan sediments of the Tulare-Wasco area (left col., fig. 23) seem to be fairly random. They are of little use in deciphering the depositional history of the sediments, unless one accepts the assumption that a lack of clearly visible relations signifies a lack of discrimination between particle sizes on the part of the transporting and depositing medium. The only suggestion of discrimination is in the CM pattern (upper row, left col., fig. 23), a wide band of points roughly parallel to the C=Md line. This pattern is similar to the pattern for recent mudflow deposits given by Bull (fig. 11). The CM pattern in the upper left corner of figure 23, however, actually consists of two patterns, one from each core of alluvial-fan sediments taken in the Tulare-Wasco area. All the samples from the Pixley core have C values less than 2,000/*; all but two samples of alluvial-fan sediments from the Richgrove core have C values greater than 1,000/*. As the principal linear trends of points in the two constituent CM patterns lie at angles of 20°-30° to the overall trend suggested in figure 23, the overall pattern is probably not significant. SHALLOW-MARINE SEDIMENTS Particle-size measures for 20 shallow-marine sediments from the Richgrove core are graphed in the right column of figure 23. All the marine sediments that have median diameters of 250/x or more are from the well-sorted sand unit (Santa Margarita Formation as used by Diepenbrock, 1933); most of the finer marine sediments are from the units of interbedded siltstone and sand. Although the samples are from two different stratigraphic units and are too few to define the relations with much certainty, there seem to be several regular relations between the particle-size measures. If the CM pattern actually is as enclosed by the dashed line (upper right cor., fig. 23), it is, of all the sediments treated in this report, the closest replica of Passega’s ideal tractive pattern (compare with fig. 9). It implies a high degree of discrimination, on the part of the transporting and depositing medium, between particles of different sizes. The distinction between well-sorted sands and less well sorted finer sediments (second row, right col., fig. 23) is approximately the same as in the alluvial sediments of the Los Banos-Kettleman City area and the Santa Clara Valley. The relation between median diameterC34 MECHANICS OF AQUIFER SYSTEMS and skewness—especially the absolute skewness (lower right cor., fig. 23)—may be sinusoidal, as suggested by the dashed lines in the figure. This suggestion is supported by the pattern of decreasing skewness with decreasing size in the fine-grained alluvial-fan sediments of the Los Banos-Kettleman City area (fig. 12) and by a similar sinusoidal pattern observed in river sediments by Folk and Ward (1957, p. 19). CLAY MINERALS AND ASSOCIATED IONS CLAY MINERALS AND THEIR ASSEMBLAGES As in the Los Banos-Kettleman City area, the principal clay mineral in the upper Cenozoic sediments of the Tulare-Wasco area is montmorillonite. Subsidiary clay minerals are illite, a kaolinite-type mineral, and vermiculite. Also present in minor amounts are chlorite and a low-grade illite-montmorillonite mixture. The j distribution of clay minerals in the two cores from this area is shown in figure 24. The criteria for the identification of the clay minerals and the method of estimating their relative proportions are given on pages C67-C71. Detailed results of the clay-mineral analyses of 26 samples are given in table 13. Assuming that these samples are representative, the average clay-mineral composition of the upper Cenozoic sediments of the area is approximately as follows: Clay minerals In nonmarine In marine sediments 1 siltstones Nearest 5 percent Montmorillonite - 60 80 Illite. .. 20 5 Kaolinite-type mineral 10 5 Vermiculite _ 10 0 Chlorite 0 5 Mixed-layer illite-montmorillonite - Trace Trace 1 Includes all sediments at depths of less than 760 ft, figure 22. The boundary between marine and nonmarine sediments in the Richgrove core is actually transitional between 785 and 744 ft. Two, and perhaps three, clay-mineral assemblages are present in the upper Cenozoic sediments of the area. The differences between the assemblages are not so much in the minerals themselves as in the relative proportions of the same group of clay minerals. The assemblage in the fine-grained siltstone layers of the marine deposits, as given above, consists of a large proportion of montmorillonite and minor amounts of illite, a kaolinite-type mineral, and chlorite. In the nonmarine sediments a slightly different assemblage was found in each of the two cores. Montmorillonite is the principal mineral in both assemblages, amounting to 50-70 percent. In the Pixley core the subsidiary minerals are, in decreasing order of abundance: a kaolinite-type mineral, vermiculite, and illite. The subsidiary minerals in the upper CLAY MINERALS (ESTIMATED PARTS PER TEN) 0 5 10 0 5 10 1 _____________1-------------1 PIXLEY CORE Illite Kaolinite-type mineral Chlorite and kaolinite-type mineral (undifferentiated) RICHGROVE CORE Figure 24.—Clay minerals in cored sediments, Tulare-Wasco area. Trace amounts not illustrated. Vermiculite in Pixley core included with montmorillonite. 760 feet of the Richgrove core, listed in the same order, are illite and a kaolinite-type mineral; vermiculite was not detected. SOURCES OF CLAY MINERALS The problem of the origin of montmorillonite in sediments from the Sierra Nevada was treated in the section, “Sources of montmorillonite” (p. C21-C22) and needs no further discussion here. The kaolinite-type mineral in the sediments of the Tulare-Wasco area may well be true kaolinite or a member of the kaolinite group, derived from the weathering of granitic rocks in the Sierra Nevada. R. J. Janda (written commun., 1964, 1965) reports that kaolinitePETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C35 and halloysite are predominant clay-mineral constituents of the soils and alluvium in the upper San Joaquin basin in the Sierra. Illite and vermiculite are probably derived from bio-tite, which is a conspicuous constituent (averaging about 5 percent) of the coarser sediments. The illite probably represents finely divided biotite. The vermiculite probably represents biotite that has been altered chemically during weathering. (See Barshad, 1948.) TOTAL CLAY-MINERAL CONTENT OF SEDIMENTS The total clay-mineral content of the sediments underlying the Tulare-Wasco area is estimated to be as follows: Percent— Lithologic unit Clay minerals Montmorillonite and vermiculite Nonmarine sediments _ 15 10 Marine siltstones and sands 25 20 Santa Margarita Formation as used by Diepenbrock (1933) <2 <2 These estimates were made on the same basis as the estimate of the clay-mineral and montmorillonite content of the sediments of the Los Banos-Kettleman City area: by averaging the percents finer than 3/t determined in the cored sediments (taken from the cumulative curves drawn in the Hydrologic Laboratory) and adjusting the average to allow for the effects of selective core recovery. IONS ASSOCIATED WITH CLAY MINERALS The principal ions adsorbed by the clays of the Tulare-Wasco area are calcium, magnesium, sodium, and hydrogen. The principal anions associated with the fine-grained sediments are sulfate and bicarbonate plus a little chloride. Results of the analyses for these ions are given in table 13. EXCHANGEABLE CATIONS (ADJUSTED PERCENT EQUIVALENTS) 0 50 100 0 50 100 |______I_______I I-------1------1 PIXLEY CORE on 500 O < Li_ cr D (f) O z < £ o 0- UJ o EXPLANATION Calcium □ Magnesium Hydrogen Sodium RICHGROVE CORE 500 iX66?X>66m 1000 - 1500 •••••••••I 2000 Figure 25.—Cations adsorbed by clay minerals in cored sediments, Tulare-Wasco area. Determined by H. C. Starkey. DISTRIBUTION OF EXCHANGEABLE CATIONS The exchangeable cations adsorbed by the clay minerals in the Pixley and Richgrove cores are represented in figure 25. As before, the illustrated percentages were adjusted by subtracting the equivalent of total anions from the total calcium ions—or, where insufficient calcium was available, from the total calcium and magnesium ions. As in the clays of the Los Banos-Kettleman City area, the adjusted sum of the exchangeable cations in most of the sediments exceeds the determined cation-exchange capacity. In seven of the samples from the Richgrove core, however, including four of those that are shown to contain exchangeable hydrogen, the adjusted sum of the cations is less than the determined exchange capacity (table 13). This difference may be due to one or more of the following causes. 1. The sum of the cations may have been overadjusted for the soluble anions; that is, some of the soluble anions (mainly sulfate) may not have been combined with calcium, but may have been in solution or adsorbed by the clay minerals. The work of Chao and others (1962) suggests that the sulfate adsorbed by clays is easily removed by leaching with water. 2. Some of the exchange sites may have been occupied by aluminum, which was not determined in the analyses. Aluminum may constitute a consider-C36 MECHANICS OF AQUIFER SYSTEMS able part of the exchangeable cations in acid sediments (Wiklander, 1955, p. 110). 3. The disparity may be related to differences in pH between the natural environment and the laboratory. The cation-exchange capacities were determined at neutrality, whereas four of these sediments registered significantly acid pH values (fig. 27). Evidence collected by Pratt (1961) suggests that the cation-exchange capacity at low pH may be less than the exchange capacity of the same material at neutral pH. The exchangeable-cation assemblage in the alluvial sediments at depths of less than 760 feet is dominated by calcium. Magnesium is subsidiary; exchangeable sodium is present in about half the samples. The clays in this depth interval are probably in near equilibrium with waters being pumped from the coarser grained sediments in the same interval—waters in the 120- to 770-foot interval in the Pixley area and in the 180- to 680-foot interval in the Richgrove area, as tabulated below. Area Depth interval (feet) Total dissolved solids (ppm) Sodium (percent of total cation equivalents) Pixley _ 120- 770 200 70 Richgrove 180- 680 300 50 500-1, 600 300 85 1, 400-2, 200 400 90 These data were summarized from analyses (Hilton and others, 1960, p. 465, 475-479, 491) of water from wells whose perforated depths were known: 5 wells in the same township as the Pixley core hole and 16 wells within 5 miles of the Richgrove core hole. The assemblage of exchangeable cations in the marine siltstones, as sampled at depths between 760 and 1,900 feet in the Richgrove core, is marked by a downward increase in sodium and a corresponding decrease in calcium. This may be related to any or all of the following factors. 1. The proportion of sodium relative to the other cations, in the water being pumped from these sediments, increases downward—see the table in the previous paragraph. The water, however, is being produced mainly from the sands, whereas the exchangeable cations were measured in the clayey siltstones, and the two types of sediments may not be in chemical equilibrium. Lack of equilibrium is suggested by the large concentrations of salts in the clays as compared to low concentrations of solids in the water being pumped from the sands and by the preponderance of sulfate over bicarbonate in the clays as compared to the reverse relation in the waters in the sands (discussed in more detail under “Sulfate in the marine siltstones”). 2. The concentration of salts in the clays increases downward (fig. 27). The ratio of monovalent to divalent cations adsorbed by clay minerals is a direct function of the concentration of ions in the sediment-water mixture (Wiklander, 1955, p. 128). The data plotted in figure 26A suggest a definite relation between salt concentration and the proportion of adsorbed sodium. 3. The pH also is lower at lower depths (fig. 27). Work by Pratt and others (1962) shows that the ratio of adsorbed sodium to adsorbed calcium may vary directly with acidity—that is, inversely with pH. The data plotted in figure 26B suggest a defi- ADSORBED Figure 26.—Relation of the proportion of adsorbed sodium to salt concentration (A) and pH (B) in sediments below 760 feet in the Richgrove core, Tulare-Wasco area. Adsorbed cations determined by H. C. Starkey, who also determined the pH in 10 : 1 water-sediment mixtures. Total dissolved solids (dissolved from 10 g sediment in 500 ml hot water) measured by Claude Huffman and A. J. Bartel.PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C37 nite relation between pH and the proportion of adsorbed sodium. On the basis of the evidence presented, I suspect that the variations in the proportions of adsorbed sodium are related in a complex way to both the acidity and the concentration of soluble salts. SULFATE IN THE MARINE SILTSTONES The soluble-anion analyses (table 13) show substantial amounts of sulfate in the marine siltstones. Visual examination of these sediments shows that they contain gypsum in irregular accumulations, often associated with organic material or partly oxidized iron sulfides. TOTAL DISSOLVED SOLIDS, IN PARTS PER MILLION SOLUBLE ANIONS, IN PERCENT EQUIVALENTS pH 0 200 o -h---------l 500 - CJ < Li. CE 3 . The reasons for graphing these measures against median diameter are reviewed on pages C13-C16. The graphs of median diameter against sorting and skewness for the alluvial sediments of the Santa Clara Valley (fig. 32) show about the same relations as the corresponding graphs for the alluvial-fan sediments of the Los Banos-Kettleman City area (fig. 12) : the best sorting in sediments having median diameters between 125/z and 500/z, poorer sorting in the finer sediments; the greatest skewness in sediments having median diameters between 16^ and 62/x, and progressively less skewness in finer and coarser sediments. The CM pattern (top graph, fig. 32), however, does not. give much insight into the processes of deposition. Many of the sediments contain isolated granules or pebbles, seemingly distributed at random, whose presence produces a wide scattering of C values. How these peb- 0.5 2 8 31 125 500 2000 5 Ld * C/5 LlI 0Q 3 W cn 7 CD | < > Ld * (/) MEDIAN DIAMETER, IN MICRONS Figure 32.—Median diameter against coarsest percentile, sorting, and skewness in alluvial sediments, Santa Clara Valley. bles and granules came to be deposited with otherwise fine sediments is not clear. CLAY MINERALS AND ASSOCIATED IONS CLAY-MINERAL ASSEMBLAGE The principal clay mineral in the upper 1,000 feet of sediments of the Santa Clara Valley, as in the areas of land subsidence in the San Joaquin Valley, is mont-C44 MECHANICS OF AQUIFER SYSTEMS morillonite. Other constituents of the clay-mineral assemblage are chlorite (type B) and illite, plus trace amounts of low-grade illite-montmorillonite. The distribution of the clay minerals in the fine-grained sediments in the Sunnyvale and San Jose cores is represented in figure 33. Clay minerals in the near-surface sediments are shown in figure 34. Details are given in tables 14 and 15. Identification criteria and the method of estimating relative proportions of clay minerals are also given on pages C67-C71. Assuming that the 20 core-hole samples are representative, the average clay-mineral composition of these sediments is— Clay minerals Percent Montmorillonite__________________________________ 70 Chlorite_________________________________________ 20 Illite_________________________________________ 5-10 Low-grade illite-montmorillonite_______________Trace The 12-A chloritic mineral, although present in the surface sediments, was not detected in the core-hole sediments. CLAY MINERALS (ESTIMATED PARTS PER TEN) EXPLANATION Montmorillonite □ Illite Chlorite Figure 33.—Clay minerals in cored sediments, Santa Clara Valley. Trace amounts not illustrated. Determined with the assistance of J. B. Corliss. The abundant montmorillonite must be derived largely from the weathering of the rocks of the Franciscan and Knoxville Formations, especially the shales, graywackes, and greenstones that are abundant in this rock assemblage. The chlorite and illite, likewise, are probably derived from fine-grained constituents of these sediments. The difference between this assemblage and the better crystallized assemblage of clay minerals, also from the Franciscan Formation, in Little Panoche Creek and the upper part of the Oro Loma core in the Los Banos-Kettleman City area (figs. 13, 14) may be related to different degrees of metamorphism in the source terranes. TOTAL CLAY-MINERAL CONTENT OF SEDIMENTS The estimates of the total clay-mineral content were made on the same basis as for the sediments of the Los Banos-Kettleman City and Tulare-Wasco areas. Clay minerals probably make up 30-35 percent of the section of fine sediments penetrated by the Sunnyvale core hole. Montmorillonite, therefore, probably makes up 20-25 percent of the section. In the coarser sediments penetrated by the San Jose core hole, the amount of clay-mineral material is substantially less—on the order of 10 or 15 percent. In other parts of the Santa Clara Valley the amount of clay-mineral material in the alluvial sediments probably ranges between 10 and 35 percent. EXCHANGEABLE CATION'S The principal ions associated with the sediments in the Sunnyvale and San Jose cores are calcium, magnesium, bicarbonate, and a little sodium. Details are given in table 14. The cations adsorbed by the clays in the cored sediments are represented in figure 35. The adjusted sum of the cations exceeds the cation-exchange capacity substantially (by a factor of 2 or more) in 7 of the 20 samples. Calcite was visible in these seven samples, and the difference between the adjusted sum and the determined capacity probably reflects the greater solubility of calcite in cold NH4C1 solution (in which the cations were determined) than in hot water (in which the anions were determined). Calcium, nevertheless, is the principal exchangeable cation. In the sediments in which the adjusted sum of cations is close to the cation-exchange capacity, calcium accounts for two-thirds to three-quarters of the exchangeable-cation equi valents. Magnesium completes the exchangeable-cation assemblage in all but the four samples near the bottom of the Sunnyvale core that contain exchangeable sodium. The water from neighboring wells that is being pumped from the coarse-grained sediments in the samePETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C45 122° 15' 122°00' 121 °45' Figure 34.—Location of core holes and sampling sites for clay minerals in Recent surface alluvial and bay-bottom sediments, Santa Clara Valley. Minerals in samples 1-11 determined with assistance of J. B. Corliss, T. J. Conomos, and J. O. Berkland. Samples 12-19 collected and analyzed by T. J. Conomos. depth interval as the core, and which is perhaps in near chemical equilibrium with the fine-grained sediments, has approximately the following chemical characteristics : Total dissolved solids________________ppm—400 Na (percent of total cation equivalents)_ 25 Ca/Mg ratio (of equivalents)_____________1. 5-2. 0 These data are summarized from the more complete analyses listed in tables 16 and 17. Because the wells in the Sunnyvale area produce ground water from large depth intervals, rather than from selected smaller deptli intervals, one cannot tell whether the increase in ex- changeable sodium in the sediments near the bottom of the Sunnyvale core hole is related to a downward increase in the dissolved sodium or to a downward increase in the total disssolved solids in the ground water. CLAY MINERALS IN THE ARVIN-MARICOPA AREA The treatment that the sediments of the Arvin-Mari-copa area are given in this report is very brief, for it is based on only eight samples from a test hole drilled near Lakeview in Kern County (location shown in fig. 36). The main purpose of this hole was not to obtain core, and only a few samples were taken (table 1). TheC46 MECHANICS OF AQUIFER SYSTEMS EXCHANGEABLE CATIONS (ADJUSTED PERCENT EQUIVALENTS) 50 100 ___I SUNNYVALE CORE 0 i LLl O < Li_ CC D (f) Q Z ~i mmsm. ~i 500 a. UJ o 1000 -> iXXMM' K>653g556SSr j 50 100 SAN JOSE CORE :,.■■■■■■-y-^66<5r SSSSaaKSgT 500 - 1000 EXPLANATION Calcium □ Magnesium Sodium Figure 35.—Cations adsorbed by clay minerals in cored sediment, Santa Clara Valley. Determined by H. C. Starkey and Toribio Manzanares, Jr. geology of the area and of the drilled deposits are summarized by Wood and Dale (1964). The land subsidence in the area is described by Lofgren (1963). Only the clay minerals are described here. Montmorillonite is the principal clay mineral in the fresh-water-bearing sediments of the Arvin-Maricopa area. Subsidiary clay minerals are illite, chlorite, and a kaolinite-type mineral. Olay minerals in the sediments cored in the Lakeview test hole are represented in figure 37. Details are given in table 18. Assuming that these eight samples are representative, the average day-mineral composition of the water-bearing sedi- ments is— Clay minerals I'crcent Montmorillonite________________________________ 7o Illite_________________________________________ 10 Chlorite ______________________________________ 10 Kaolinite-type mineral__________________________ 5 The sediments that were pierced by the Lake view test hole, and presumably the included clay minerals, seem to have been derived from a metamorphic and silicic- igneous terrane. The nearest and most likely such ter-rane is in the San Emigdio Mountains, to the south of the Arvin-Maricopa area. However, as only 37 feet of core (from 65 ft of cored interval, see table 1) was recovered from the test hole, the source can be identified on a tentative basis only. The main constituents of the gravels and the lithic grains in the sands recovered from this hole are fragments of metamorphic (schistose rocks, marble, hornfels, quartzite, serpentine) and megascopi-cally crystalline silicic igneous rocks (mainly diorite). The sands are light colored. Biotite and hornblende grains are present but only amount to a percent or so of the sands. Because so little core was taken from the Lakeview hole, no estimate was made of the total clay-mineral material in the sediments. Neither were the exchangeable cations determined. SUMMARY OF RESULTS OF PETROLOGIC STUDY The fresh-water-bearing sediments, mostly Pliocene to Recent in age, that lie beneath the three major areas of land subsidence in the San Joaquin and Santa Clara Valleys of California consist of detritus from the Sierra Nevada and the Coast Ranges. They are mostly alluvial, having been deposited on alluvial fans or on the flood plains of perennial streams. The sediments also include shallow-marine, lacustrine, and deltaic deposits, but these are less abundant than the alluvial deposits. Because the particle sizes are so diverse, they are not easily summarized in a few sentences. Numerical averages, although they give some general impression of the sizes of the particles, are of limited significance. The geometric-mean particle size of all the sediments is probably in the coarse-silt range, 30/* to 60/*. The most abundant sediment type, according to the Shepard classification, is clayey silt; other abundant types are sand-silt-clay and silty sand. The alluvial sediments, as well as being the most abundant sediment types, are also the most diverse in their size characteristics. They range from gravels to silty clays. The alluvial sediments in the Los Banos-Kettleman City area have a mean particle size between 30/i and 60/i and a modal size between 125/* and 250/*. Those in the Tulare-Wasco area have a mean size between 40/* and 80/* and a modal size between 30/* and 60/*. Note that although the Los Banos-Ivettle-man City sediments have a finer mean size than the Tulare-Wasco sediments, their modal size is coarser. The mean sizes of the alluvial sediments in the Santa Clara Valley range from rather coarse (500/* to 1,000/*) beneath the major streams to rather fine (5/* to 10/*) away from the axis of the valley. The general degree of sorting of all the alluvial sediments is fair to poorPETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C47 R. 23 W. R. 24 W. R. 25 W. R. 26 W. R. 27 W. R. 28 E. R. 29 E. R. 30 E. R. 31 E. Buttonwillow Bakersfield [£ Arvin I LAKEVIEW iTEST HOLE 11N/21W-3B1 Maricopa Mettlei Grapevinev Figure 36.—Arvin-Maricopa area showing location of Lakeview test hole. (average QD* near 2.0). Skewness measures indicate a disproportionately large admixture of finer particles. The interrelations of the particle-size measures (median diameter versus sorting, skewness, and the coarsest percentile) provide some insights into depositional processes, but they do not provide a unique means of interpreting the histories of alluvial sediments. Montmorillonite is the predominant clay mineral in nearly all the sediments, regardless of their source ter-ranes or their environments of deposition. It comprises 60-80 percent of the clay-mineral assemblages and 5-25 percent of the different sections of sediments whose compaction accounts for the observed land subsidence. The uniform preponderance of montmorillonite in clay-mineral assemblages derived from diverse source terranes (Sierra Nevada, Coast Ranges, and, in the Arvin-Maricopa area, the Transverse Ranges) and deposited in diverse environments (marine as well as nonmarine) implies some sort of pervasive influence on the clay-mineral assemblages. The identity and nature of this influence, however, await further study. Calcium is the principal exchangeable cation adsorbed by the clay minerals. Other adsorbed cations are magnesium, sodium, and hydrogen. The proportion of adsorbed sodium increases with increasing depth, probably reflecting a corresponding downward increase in the sodium content of the associated interstitial waters. In some of the marine siltstones of the Tulare-Wasco area, calcium is replaced in the exchange positions by the other cations, under the influence of locally acid conditions accompanying high concentrations of sulfate. Four petrologic characteristics are probably the most important to the understanding of the compaction behavior of these sediments: (1) the general fineness of the particle sizes, (2) the diverse juxtaposition of coarser and finer deposits, (3) the large proportion of montmorillonite, and (4) the downward increase in the proportion of adsorbed sodium relative to adsorbed calcium. As shown by studies reviewed in an earlier report in this series (Meade, 1964, fig. 3), finer sediments are more porous under a given load and more compressible under a given change in load than coarser sediments. The interbedding of coarser layers with the finer deposits provides permeable avenues of escape for the water squeezed from the finer deposits. Laboratory studiesDEPTH, IN FEET BELOW LAND SURFACE C48 MECHANICS OF AQUIFER SYSTEMS CLAY MINERALS (ESTIMATED PARTS PER TEN) 0 5 10 EXPLANATION Montmorillonite □ lllite Chlorite Kaolinite-type mineral Chlorite and kaolinite-type mineral Figure 37.—Clay minerals in cored sediments from Lake-view test hole, Arvin-Mari-copa area. Trace amounts not illustrated. Determined with the assistance of F. P. Naugler and J. B. Corliss. by several workers, summarized earlier (Meade, 1964, fig. 4), show that clays rich in montmorillonite are more porous and more compressible under a given load or change in load than clays that consist mainly of the other clay minerals. And, finally, other laboratory studies (Meade, 1964, fig. 11) show that montmorillonite which has adsorbed sodium as its exchangeable cation is more porous under a given load than montmorillonite whose exchange positions are saturated with calcium. The next report in this series (Meade, R. H., Compaction of sediments underlying areas of land subsidence in central California, in preparation for publication as Prof. Paper 497-D) considers in more detail the relations of the petrologic characteristics to the observed compaction of the sediments. DETERMINATION AND DESCRIPTION OF PARTICLE SIZES SAMPLING AND PARTICLE-SIZE ANALYSIS Samples for particle-size analysis were taken, where-ever possible, from each 10 feet of cored interval. A consistent attempt was made to take “average” samples—that is, the sample from each 10-foot interval that seemed to be the most representative of material in the interval. Sampling, as a result, was not random, but was biased toward the visually estimated “average” sediment. The sampling was also biased toward the finer sediments in the sections. The coring apparatus was unable to recover much of the loose gravel and well-sorted coarser sands, whereas it recovered easily the more cohesive clays, silts, fine sands, and poorly sorted sands. Not all the coarser material was lost, however—some well-sorted coarse sand and even a little loose gravel was recovered—and not all the unrecovered material was coarse grained. Some of the lost material was fine sediment that was not recovered because of occasional lapses in the efficiency of the coring procedure. The two sources of sample bias—selectivity in coring and selectivity in sampling of the recovered core materials—limit the statistical use that can be made of the data on particle-size distribution. For example, one can estimate the mean particle size of the sediments as a whole only within widely spaced limits. On the other hand, the particle-size data can be used in a descriptive way and can be helpful in understanding the history and properties of the sediments—as long as one keeps in mind that the samples were not taken at random and that sampling of the coarsest and very finest sediments was especially inadequate. Particle-size analyses of the samples were made in the Hydrologic Laboratory of the Geological Survey by standard wet sieve and hydrometer methods. ThePETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C49 procedures and results are given in the report by A. I. Johnson, R. P. Moston, and D. A. Morris (1967). DESCRIPTION OF PARTICLE SIZES Because most of the sediments treated in this report are fairly fine, the particle sizes are expressed in microns (ft). The size-grade intervals used to express median and modal diameters in figures 6-12, 20-23, and 30-32 are those suggested by the National Research Council (Lane and others, 1947, p. 937), as given in the following table. Grade 1 M 0 Coarse gravel. _ _ 32, 000 -5 Medium gravel. 16, 000 -4 Fine gravel 8, 000 -3 Very fine gravel. _ _ _ 4, 000 -2 Very coarse sand.. ... 2, 000 -1 Coarse sand _ 1, 000 0 Medium sand 500 1 Fine sand 250 2 Very fine sand.. 125 3 Coarse silt- _ _ _ 62 4 Medium silt .. 31 5 Fine silt-- _____ 16 6 Very fine silt ____ _ _____ 8 7 Coarse clay _ __ 4 8 Medium clay__ _ 2 9 Fine clay 1 10 .5 11 i Lane, E. W., chm., and others, 1947, p. 937. The phi-notation system for particle sizes was used to compute some of the measures of sorting and skewness. Phi (<£), as defined by its originator Krumbein (1934), is the negative logarithm to the base 2 of the grain diameter: 4>=-log2A, where N is th.e grain diameter in millimeters. The advantages of this system are that it converts a geometric grade scale to an arithmetic one and “permits the application of common statistical procedures to the data” (Krumbein, 1936a, p. 35). The system and its advantages are discussed further by Krumbein (1934, 1936a, b). Phi values are included in the table above. Note that one whole 4> interval corresponds to one grade in the National Research Council classification. Selected percentiles, mean sizes, and measures of sorting and skewness, derived graphically from the cumulative curves or interpolated from particle-size data by a digital computer are given in tables 5-9. (Cumulative curves of some of the samples are given by Johnson and others, 1967.) Inman (1952, p. 125) suggests the inclusion of the following percentiles in a description of grain-size distributions: 5th, 16th, 50th (the median diameter, Md), 84th, and 95th. These are given in the tables, along with the 1st percentile (C, used in an interpretive method devised by Passega, 1957) and the 25th and 75th percentiles (the 1st and 3d quartiles, used in well-known measures of sorting and skewness devised by Trask, 1930, and Krumbein, 1936b). Percentiles are given in microns and phi units. The following measures, computed from the percentiles, are also tabulated for the benefit of those interested in specific numerical data. Me^tsure Symbol Formula Reference Md 50th percentile, taken directly from the distribution curve and expressed either in n, mm, or 0. H(018+0S4) ^(025+07#) H(084—01«) ^(075—025) M+-Md+ QM+—Md+ QM^—Md* QD* PuPis/Aft* M+ QM+ and a* are recommended over quartile measures by Inman (1952, p. 126), among others, because they describe more of the sample—two-thirds instead of half—and because they are analogous to the moments of the normal frequency distribution generally used in statistics. Unfortunately, the sediments described in this report were so fine that the 84th percentile, necessary to the computation of and a*, was not determined in many samples. The finest grain size determined in the hydrometer analyses was 1.0/*. In many of the sediments, especially those from the Los Banos-Kettleman City area and the Santa Clara Valley, the 84th percentile was below 1.0/*. Because the third quartile (75th percentile) was 1.0/* or larger in many more of the sediments and could be used to compute sorting and skewness measures, quartile measures were used. Although a digital computer and a program were available to compute the actual moments of the size dis-C50 MECHANICS OF AQUIFER SYSTEMS tributions, rather than such graphical analogues of the moments as o> and QD$, the moments were not computed. Because the finer parts of the size distributions were not determined in detail, the graphical measures based on measured percentiles are probably as accurate a portrayal of sorting and skewness as moments calculated from size distributions whose finer parts have to be assumed. SKQ0/QD0, OR BOWLEY’S MEASURE OF SKEWNESS Because Bowley’s measure of skewness, Skq^/QD has not been applied to sediments before, as far as I know, an expanded discussion is given here to relate it to the measures of skewness that are already established in the literature of sedimentology. In spite of the fact that the particle-size distributions of most sediments do not follow the normal or lognormal probability law (Pettijohn, 1957, p. 40-42), the distribution parameters derived from probability theory are valuable for describing particle-size distributions and for comparing one distribution with another. This is particularly true of skewness measures. They “are used mainly in descriptive statistics; in experimental work, if a distribution is found to be skew, it is better to seek a transformation of the variable which will yield a nearly symmetrical distribution and carry out the necessary calculations in terms of the new variable” (Davies, 1957, p. 37). Because their use is mainly descriptive, measures of skewness can be designed to show different characteristics of frequency distributions. Some skewness measures, for instance, show the absolute difference between two measures of central tendency; other relative measures show more clearly the asymmetry of the distribution. Bowley’s measure of skewness is a measure of asymmetry. Waugh (1952, p. 203) gives the formula for Bowley’s measure of skewness: @3+#i — 2 median Substituting phi notation and dividing numerator and denominator by 2, we have Dj (075+025) — Md# 3^(075 — <£25! which is QM^>—Md(t,> Skq0 QD * Q D,' Rather than introduce a new symbol, I prefer to express it as a fraction of two well-known symbols introduced by Krumbein (1936b, p. 102-103, 107-110). All the possible values of SkqJQD^ fall between —1.0 and -)*1.0. Skqt/QDj, gives a clearer impression than Skq# of the asymmetry of a particle-size distribution. Skq* is the difference between the quartile mean (QM#) and the median diameter (.Md*). In using Skq*, one can assign equal skewness values to a slightly asymmetrical poorly sorted sediment and a strongly asymmetrical well-sorted sediment. Dividing Skq# by QD+ makes it a simple measure of asymmetry and less dependent on the spread of the distribution. The relation of Skq^/QD^, to another established measure of skewness, Sk (Trask, 1930, p. 594), is shown in figure 38. Positive values of SkqJQD* are associated with negative values of the logarithm to the base 10 of Sk. The numerical relation between the two measures varies with changes in the value of QD. In a sediment for which QD^,—1.67, SkqJQD QDt a4> Skq$ Skq* Sk (per- cent) Mendota core—Continued 57 CAL 26.. 57 CAL 27.. 57 CAL 28.. 57 CAL 29.. 57 CAL 30.. 57 CAL 31.. 57 CAL 32.. 57 CAL 33.. 57 CAL 34.. 57 CAL 35.. 57 CAL 36.. 57 CAL 37.. 57 CAL 38.. 57 CAL 39.. 57 CAL 40.. 57 CAL 41.. 57 CAL 42.. 57 CAL 43.. 57 CAL 44.. 57 CAL 45.. 57 CAL 46.. 57 CAL 47.. 57 CAL 48.. 57 CAL 49. _ 57 CAL 50.. 57 CAL 51.. 57 CAL 52.. 57 CAL 53.. 57 CAL 54.. 57 CAL 55.. 57 CAL 56.. 57 CAL 57.. 57 CAL 58.. 57 CAL 59.. 57 CAL 60.. 57 CAL 61.. 57 CAL 62.. 57 CAL 63.. 57 CAL 64.. 57 CAL 65-. 57 CAL 66.. 57 CAL 67.. 57 CAL 68.. 57 CAL 69. 57 CAL 70. 57 CAL 71. 743 757 765 773 785 791 802 812 813 826 832 844 853 860 867 871 877 888 901 912 917 932 937 951 958 1, 001 1, 005 1, 021 1, 034 1, 040 1, 051 1, 064 1, 071 1, 075 1, 089 1, 092 1,105 1,114 1,124 1,133 1,160 1,174 1,207 180 2.5 430 1.2 1,200 -0. 26 110 3.2 110 3.2 210 2.3 200 2.3 1, 500 -0.58 1,100 -0.13 65 3.9 200 2.3 230 2.1 350 1.5 76 3.7 350 1.5 640 0.64 120 3.1 54 4.2 200 2.3 450 1.2 500 1.0 330 1.6 160 2.6 210 2.3 25C 2. C 17C 2.e 150 2.7 390 1.4 240 2.1 140 2.8 200 2.3 750 0. 41 170 2.6 140 2.8 400 1.3 310 1.7 400 1.3 480 1.1 1,100 -0.13 1,200 -0.26 440 1.2 450 1.2 110 3.2 3,800 -1.9 7, 500 __O Q 25, 500 -4.7 71 340 750 93 90 130 140 1, 000 510 23 110 180 250 55 260 300 63 22 90 320 350 80 100 58 180 70 27 280 60 39 89 500 29 84 300 180 300 360 730 750 360 340 66 870 1,900 16,000 40 4.6 200 2.3 550 0.86 80 3.6 62 4.0 82 91 3.5 630 0.67 330 1.6 13 53 4.2 150 2.7 170 2.6 37 4.8 180 2.5 180 2.5 29 12 38 4.7 200 2.3 280 1.8 40 50 4.3 35 120 3.1 39 4.7 7.3 150 27 25 52 4.3 350 1.5 17 55 4.2 230 2.1 81 3.6 200 2.3 280 1.8 370 1.4 270 1.9 290 1.8 250 2.0 33 440 1.2 950 .07 6,700 -2.7 29 5.1 140 2.8 490 1.0 73 3.8 45 4.5 63 4.0 75 3.7 480 1.1 280 1.8 8.8 6.8 42 4.6 140 2.8 150 2.7 29 5.2 140 2.8 150 2.7 18 5.8 9.0 6.8 25 5.3 150 2.7 250 2.0 27 33 4.9 25 5.3 89 3.5 31 5.0 4.0 84 3.6 19 5.7 20 5.6 40 4.6 260 1.9 12 44 4.5 170 2.6 47 4.4 160 2.6 250 2.0 150 2.7 120 3.1 270 1.9 220 2.2 23 5.4 350 1.5 750 .41 2,600 -1.4 13 6.3 62 4.0 320 1.6 51 4.3 20 5.6 26 5.3 40 4.6 250 2.0 210 2.3 3.3 8.2 20 5.6 110 3.2 110 3.2 14 6.2 77 3.7 98 3.4 5.0 7.6 4.1 7.9 11 6.5 56 4.2 210 2.3 6.4 7.3 16 6.0 8.2 6.9 44 4.5 16 6.0 1.5 9.4 25 5.3 6.8 7.2 8.9 6.8 23 5.4 71 3.8 4.9 7.7 25 5.3 26 5.3 20 5.6 79 3.7 ISO 2.5 42 4.6 37 4.8 230 2.1 160 2.6 10 6.6 250 2.0 520 .94 520 .94 4.3 1.8 6.9 6.5 2.2 1.4 0. 27 0.15 0. 21 0.74 7.9 9.1 15 6.5 4.8 4.4 2.5 1.6 .32 .27 .44 .55 6.1 7.3 86 25 3.1 2.3 2.2 1.3 .65 .51 .64 .41 3.5 5.3 15 5.8 5.5 4.9 1.9 1.1 .66 .55 .63 .42 6.1 7.4 5.2 1.9 6.5 6.0 2.5 1.6 .35 .25 .39 .58 7.6 9.0 1.8 6.6 2.6 .50 1.28 .15 9.1 6.0 1.9 6.2 5.6 2.8 1.8 .58 .51 .92 .28 7.4 9.0 85 45 2.6 2.3 1.9 1.2 .30 .25 .31 .65 3.6 4.5 170 150 2.2 2.2 .6 .4 -.14 -.14 -.05 1.08 2.6 2.7 1. 2 8.3 1. 4 .01 .02 .97 9.7 3.5 1.1 7.0 6.4 2.8 1.8 .50 .40 .72 .37 8.2 9.8 37 14 4.4 3.8 1.7 1.0 .74 .65 .62 .43 4.8 6.2 87 59 1.7 3.3 3.1 .8 .4 .18 -.13 -.05 1.08 3.5 4.1 3.2 1.1 7.3 6.7 2.5 1.6 .45 .36 .56 .46 8.3 9.8 10 2.2 5.6 4.7 3.2 1.9 .61 .55 1.04 .24 6.6 8.8 50 22 4.0 3.5 1.5 .8 .42 .23 .18 .78 4.3 5.5 1. 0 7.9 2.1 .12 .24 .72 10.0 0.9 8.5 1.7 .32 .53 .48 10.1 2.9 1.6 7.0 6.9 2.3 1.6 .21 .23 .36 .60 8.4 9.3 13 2.5 5.5 4.5 3.2 1.8 .42 . 19 .34 .62 6.3 8.6 100 39 3.3 2.7 1.4 .7 .71 .62 .41 .57 3.3 4.7 4.9 2.3 6.5 6.3 2.2 1.4 .26 .23 .32 .63 7.7 8.8 1. 0 7.6 2.3 .31 .71 .37 10.0 16 6.7 5.1 4.7 2.1 1.2 .30 .18 .22 .74 6.0 7.2 3.9 1.0 7.3 6.5 2.6 1.5 .51 .36 .53 .47 8.0 10.0 1.8 6.3 2.8 .37 1.02 0.24 9.1 1. 0 7.8 2.1 .30 .64 .41 10.0 2. 5 7.1 1. 5 .22 .33 .63 8.6 5.0 1.9 6.7 6.1 2.4 1.5 .51 .47 .70 .38 7.6 9.0 14 4.0 4.7 4.0 3.2 2.1 .28 .11 .23 .72 6.2 8.0 7.1 2.2 6.5 5.8 2.3 1.3 .51 .38 .50 .50 7.1 8.8 4.5 0.9 6.1 5.2 4.0 2.6 .21 -.03 -.09 1.13 7.8 10.1 3.6 1.0 6.8 6.3 3.2 1.9 .37 .33 .62 .42 8.1 10.0 17 3.0 5.3 4.3 3.0 1.6 .56 .37 .60 .44 5.9 8.4 90 51 3.1 2.7 1.2 0.7 .48 .36 .26 .69 3.5 4.3 15 4.8 4.6 4.4 3.1 1.7 .00 -.10 -.17 1.28 6. J 7.7 9.4 2.4 5.3 4.9 3.4 1.8 .16 .07 .13 .82 6.7 8.7 180 130 2.4 2.2 0.6 .3 .42 .21 .06 .92 2.5 2.9 110 65 3.0 2.7 1.0 .5 .34 .08 .04 .95 3.2 3.9 2.3 7.1 1.7 .28 .46 .53 8.8 150 78 2.4 2.1 1.2 .6 .34 .20 .12 .84 2.7 3.7 270 140 1.5 1.1 1.4 .7 .37 .28 .21 .75 240 120 1.3 .2 .3 2.9 1.7 27 -.35 -.60 2.31 2.1 3.1 21 10 8 13 19 28 19 8 7 48 24 10 6 24 17 10 41 44 26 16 7 41 19 37 12 23 68 28 36 27 20 15 41 18 22 24 16 9 14 17 7 7 28 8 7 7PETROLOGY, SEDIMENTS UNDERLYING AREAS Of LAND SUBSIDENCE, CENTRAL CALIFORNIA C53 Table 5.—Particle-size data for sediments from Mendota, Cantua Creek, and Huron cores, Los Banos-Kettleman City area—Continued Sample Depth below land surface (feet) Percentiles ^ microns ) Means Deviations Skewness Finer than 3 microns (percent) 1 (C) 5 16 25 50 (Md) 75 84 95 M* QM» QD* a* Skq* Skq4, Sk Mendota core—Continued 57 CAL 72 1,219 6,600 1,400 460 360 250 no 24 3.2 2.3 2.1 0.9 0. 59 0.38 0.32 0.63 9 -2.7 1.1 1.5 2.0 3.2 5.4 57 CAL 73 1,221 4,100 2,200 1,100 770 350 130 7.4 3.5 1.7 3.6 1.3 .54 . 12 . 15 .82 13 -2.0 -.13 .38 1.5 2.9 7.1 57 CAL 74 1,232 6,300 2,900 1,400 770 370 190 100 5.1 1.4 1.4 1.9 1.0 -.01 -.04 -.04 1. 07 4 -2.7 -.49 .38 1.4 2.4 3.3 57 CAL 75 1,242 150 100 58 40 20 7.2 3.1 6.2 5.9 2.1 1.2 .27 . 19 . 24 . 72 16 2.7 4.1 4.6 5.6 7.1 8.3 57 CAL 76 1,252 400 300 210 170 130 56 18 4. 0 3.4 1.8 .8 .61 .52 .42 . 56 8 1.3 2.3 2.6 2.9 4.2 5.8 57 CAL 77 1,257 860 600 350 250 160 73 16 3.7 2.9 2.2 .9 . 49 .28 .25 .71 11 .22 1.5 2.0 2.6 3.8 6.0 57 CAL 78 1,270 1,100 600 310 220 82 5.4 4.9 2.7 . 46 1. 24 . 18 24 -.13 2.2 3.6 7.5 57 CAL 79.. _ 1,271 440 350 270 240 180 30 3.6 5.0 3.6 3.1 1.5 .81 .73 1.09 .22 15 1.2 1.9 2.1 2.5 5.1 8.1 57 CAL 80 1,284 410 310 240 210 170 130 85 2.8 2.6 .7 .3 .33 .09 .03 .95 8 1.3 2.1 2.3 2.6 2.9 3.6 57 CAL 81 1,293 410 320 220 180 81 8. 3 1.0 6.1 4.7 3.9 2.2 .63 .48 1.06 . 23 20 1.3 2.2 2.5 3.6 6.9 10.0 57 CAL 82 1,300 400 320 240 210 120 11 1.3 5.8 4.4 3.8 2.1 .73 .62 1.32 . 16 20 1.3 2.1 2.3 3.1 6.5 9.6 57 CAL 83 1,312 460 310 170 65 22 3.7 1.0 6.3 6.0 3.7 2.1 .20 . 24 . 50 . 50 23 1.1 2.6 3.9 5.5 8. 1 10.0 57 CAL 84 . 1,320 440 340 270 240 170 14 2.5 5.3 4.1 3.4 2.0 .80 .76 1.55 .12 16 1.2 1.9 2.1 2.6 6.2 8.6 57 CAL 85 1,331 430 280 230 190 130 13 1.2 5.9 4.3 3.8 1.9 .78 .72 1.39 .15 18 1.2 2.1 2.4 2.9 6.3 9.7 57 CAL 86.. 1,340 220 120 67 48 22 5. 5 2.0 6.4 5.9 2. 5 1.6 .36 . 28 .43 . 55 19 2.2 3.9 4.4 5.5 7.5 9.0 57 CAL 87 1,348 8, 800 4,300 1,000 780 480 220 130 1.5 1.3 1.5 .9 .28 .23 .21 .75 7 -3.1 0.0 0. 36 1.1 2.2 2.9 57 CAL 88.. 1,357 180 96 33 20 5.8 1. 2 7.7 2.0 . 12 . 24 .71 39 2.5 5.6 7.4 9.7 57 CAL 89 1,363 250 150 95 70 30 5.2 5.7 1.9 .35 .65 .40 21 2.0 3.8 5.1 7.6 57 CAL 90 1,374 360 260 190 160 64 6.9 1.4 5.9 4.9 3.5 2.3 .56 .41 .94 .27 19 1.5 2.4 2.6 4.0 7.2 9.5 57 CAL 91 1,385 360 230 100 45 16 4. 2 1.9 6. 2 6.2 2.9 1. 7 .07 . 12 . 21 .74 21 1.5 3.3 4.5 6.0 7.9 9.0 57 CAL 92 1,397 450 290 29 8.7 2.3 56 1.2 8.8 57 CAL 93 1,406 420 330 250 210 110 9.0 2.1 5.4 4. 5 3.4 2.3 .66 .59 1.34 . 16 18 i.3 2.0 2.3 3.2 6.8 8.9 57 CAL 94.. 1,415 530 380 260 200 91 21 4.6 4.8 3.9 2.9 1.6 .48 .30 .48 .51 15 0.92 1.9 2.3 3.5 5.6 7.8 57 CAL 95 1,424 390 240 160 130 85 20 5.0 5.1 4.3 2.5 1.3 .63 .54 .73 .36 14 1.4 2.6 2.9 3.6 5.6 7.6 57 CAL 96.. 1,433 94 55 30 22 9.0 1. 7 7.4 1.8 .30 .55 .46 31 3.4 5.5 6.8 9.2 57 CAL 97... 1. 446 50 33 18 12 4. 8 40 4.3 7.7 57 CAL 98.. .. 1,455 350 220 120 73 20 4.2 1.4 6.3 5.8 3.2 2.1 .20 . 10 .20 .77 22 1.5 3.1 3.8 5.6 7.9 9.5 57 CAL 99.. 1,465 280 35 11 6.8 2.3 56 1.8 8.8 57 CAL 100 1,474 410 250 180 160 120 48 26 3.9 3. 5 1.4 .9 . 58 .52 .45 .53 10 1.3 * 2.5 2.6 3.1 4.4 5.3 57 CAL 101 1,481 2,500 800 410 270 74 13 4.3 4.6 4.1 3.3 2.2 .25 . 15 .32 .64 13 -1.3 1.3 1.9 3.8 6.3 7.9 57 CAL 102 1,487 580 420 340 300 220 130 39 3.1 2.3 1.6 .6 .60 .27 . 16 .81 8 0. 79 1.6 1.7 2.2 2.9 4.7 57 CAL 103 1,495 430 280 210 180 87 14 5.9 4.8 4.3 2.6 1.8 .51 .43 .79 .33 12 1. 2 2.3 2.5 3.5 6.2 7.4 Cantua Creek core 58 CAL 1 250 3,800 950 340 250 120 41 11 4.0 3.3 2. 5 1.3 0.39 0.18 0. 24 0. 71 12 -1.9 1.6 2.0 3.1 4.6 6.5 58 CAL 2 298 520 220 92 57 17 3.0 6.3 2.1 . 17 .37 .59 25 0. 94 4.1 5.9 8.4 58 CAL 3 333 500 290 140 70 10 1. 5 6.6 2.8 -.01 -.03 1.05 32 1.0 3.8 6.6 9.4 58 CAL 4 372 740 510 370 310 140 52 8. 7 4. 1 3.0 2.7 1.3 .48 . 11 . 14 .82 13 0. 43 1.4 1.7 2.8 4.3 6.8 58 CAL 5 419 240 130 61 37 8. 5 2.3 1. 4 6.8 6.8 2.7 2.0 -.04 -.06 -. 12 1. 18 31 2.1 4.0 4.8 6.9 8.8 9.5 58 CAL 6... 455 330 130 71 42 5. 0 46 1.6 7.6 58 CAL 7 497 700 370 260 230 150 49 14 4.0 3.2 2.1 1.1 .62 .44 .49 .50 13 0. 51 1.9 2.1 2.7 4.4 6.2 58 CAL 8 508 2,200 170 38 22 7.5 1. 5 7.4 1.9 .20 .38 .59 34 -1.1 5. 5 7.1 9.4 58 CAL 9 510 110 60 32 22 9.7 3.3 6.9 1.4 . 13 . 18 .77 24 3.2 5.5 6.7 8.2 58 CAL 10 526 100 38 16 11 5.7 1.8 7.8 1.3 .28 .36 .61 34 3.3 6.5 7.5 9.1 58 CAL 11 533 580 360 210 140 28 2.3 5.8 3.0 .22 .64 .41 27 0. 79 2.8 5.2 8.8 58 CAL 12 553 300 170 78 47 16 2. 3 1. 3 6.6 6.6 3.0 2.2 . 22 . 28 .61 .42 28 1.7 3.7 4.4 6.0 8.8 9.6 C54 MECHANICS OF AQUIFER SYSTEMS Table 5.—Particle-size data for sediments from Mendota, Cantua Creek, and Huron cores, Los Banos-Kettleman City area—Continued Sample Depth below land surface (feet) Percentiles ^ microns ) Means Deviations Skewness Finer than 3 microns 1 (C) 5 16 25 50 (Md) 75 84 95 M* QMt QDt a* Skq+ QD* Skqj, Sk (per- cent) Cantua Creek core—Continued 58 CAL 13 564 310 140 63 38 9.3 2.0 1.0 7.0 6.8 3.0 2.1 0.08 0.04 0.09 0.88 31 1.7 4.0 4.7 6.7 9.0 10.0 58 CAL 14 571 350 83 38 23 5.5 1.0 7.7 2.3 .08 .19 .76 40 1.5 5.4 7.5 10.0 58 CAL 15 581 480 360 280 260 200 140 97 27 2.6 2.4 .8 .4 .37 .16 .07 .91 3 1.1 1.8 1.9 2.3 2.8 3.4 58 CAL 16 592 800 510 370 330 270 210 190 120 1.9 1.9 .5 .3 .04 .09 .03 .95 0 0.32 1.4 1.6 1.9 2.3 2.4 58 CAL 17 602 780 590 450 390 300 230 180 46 1.8 1.7 .7 .4 .11 .00 .00 1.00 1 .36 1.2 1.4 1.7 2.1 2.5 58 CAL 18 623 790 460 310 260 180 99 65 4.3 2.8 2.6 1.1 .7 .30 .24 .17 .79 4 .34 1.7 1.9 2.5 3.3 3.9 58 CAL 19 637 400 220 97 63 21 4.4 2.0 6.2 5.9 2.8 1.9 .21 .18 .34 . 63 21 1.3 3.4 4.0 5.6 7.8 9.0 58 CAL 20 643 370 200 100 73 29 6.5 1. 2 6.5 5. 5 3.2 1.7 .44 .24 .41 .56 20 1.4 3.3 3.8 5.1 7.3 9.7 58 CAL 21 653 630 360 200 140 37 3.4 1.0 6.1 5.5 3.8 2.7 .36 .28 .76 .35 24 .67 2.3 2.8 4.8 8.2 10.0 58 CAL 22 666 200 52 13 8.8 4.4 0.9 8.5 1.6 .39 .64 .41 42 2.3 6.8 7.8 10.1 58 CAL 23 674 290 41 8.1 4.7 1.5 65 1.8 9.4 58 CAL 24 684 170 110 70 56 30 5.7 1.0 6.9 5.8 3.1 1.6 .60 .45 .75 .35 21 2.6 3.8 4.2 5.1 7.5 10.0 58 CAL 25 697 160 38 12 7. 0 2.0 58 2.6 9.0 58 CAL 26 702 260 100 49 34 15 3. 0 6.6 1.7 .33 .57 . 45 25 1.9 4.9 6.1 8.4 58 CAL 27 714 200 58 23 14 5. 0 2. 0 1. 4 7. 5 7. 6 2. 0 1. 4 -. 09 -. 06 -. 08 1.12 37 2.3 5.4 6.2 7.6 9.0 9.5 58 CAL 28 722 430 260 170 120 55 12 1.0 6.3 4.7 3.7 1.7 .56 .33 .54 .48 17 1.2 2.6 3.1 4.2 6.4 10.0 58 CAL 29 732 320 180 86 55 21 5.3 5.9 1.7 . 18 .30 .66 24 1.6 4.2 5.6 7.6 58 CAL 30 746 310 130 30 11 1.2 58 1.7 9.7 58 CAL 31 . 754 190 86 37 25 12 2. 4 1. 0 7.4 7. 0 2.6 1.7 .38 .37 .63 .42 27 2.4 4.8 5.3 6.4 8.7 10. 0 58 CAL 32 763 320 200 81 34 5.1 1. 0 7. 4 2.5 -. 08 -.20 1.31 42 1.6 4.9 7.6 10.0 58 CAL 33. . 774 340 220 130 95 33 4.3 1. 0 6. 5 5.6 3.5 2.2 .44 .32 .71 .38 21 1.6 2.9 3.4 4.9 7.9 10.0 58 CAL 34... .. 785 450 360 290 250 180 100 57 3. 0 2.7 1.2 .7 .42 .29 . 19 .77 7 1.2 1.8 2.0 2.5 3.3 4.1 58 CAL 35 795 210 110 28 13 2.1 55 2.3 8.9 58 CAL 36 806 190 83 22 10 2.9 51 2.4 8.4 58 CAL 37 . 811 290 190 110 78 41 10 2.2 6. 0 5.2 2.8 1. 5 .49 .37 . 55 . 46 17 1.8 3.2 3.7 4.6 6.6 8.8 58 CAL 38 ... 822 600 260 98 43 3.2 49 0.74 8.3 58 CAL 39 828 350 240 120 70 8. 2 39 1.5 6.9 58 CAL 40 838 150 59 21 11 3.6 0.9 8.3 1.8 . 11 . 19 .76 46 2.7 6.5 8.1 10.1 58 CAL 41 852 420 340 220 160 64 6.6 1. 2 5.9 4.9 3.8 2. 3 . 52 . 42 .97 .26 21 1.3 2.2 2.6 4.0 7.2 9.7 58 CAL 42 860 330 200 100 64 16 2.9 6.2 2.2 . 10 .23 .72 25 1.6 4.0 6.0 8.4 58 CAL 43 867 340 220 150 120 70 4. 2 5.5 2. 4 .68 1.64 . 10 24 1.6 3.1 3.8 7.9 58 CAL 44 877 450 390 310 270 190 88 32 3.3 2.7 1.6 .8 .57 .37 .30 .66 9 1.2 1.7 1.9 2.4 3.5 5.0 58 CAL 45 892 340 200 81 40 5. 4 44 1.6 7.5 58 CAL 46 901 220 82 25 13 3. 0 50 2.2 8.4 58 CAL 47 911 430 280 220 200 130 57 30 3.6 3.2 1. 4 . 9 .47 .31 .28 .67 11 1.2 2.2 2.3 2.9 4.1 5.1 58 CAL 48 923 250 120 46 22 4.1 45 2.0 7.9 58 CAL 49 931 370 240 100 60 15 2.0 6. 5 2.5 . 19 .45 .53 29 1.4 4.1 6.1 9.0 58 CAL 50 941 150 97 50 30 6.3 41 2.7 7.3 58 CAL 51 947 60 21 9. 1 5.9 2.1 59 4.1 8.9 58 CAL 52 964 320 180 100 71 28 5.7 1. 7 6.3 5.6 2.9 1.8 .37 .26 .47 .52 20 1.6 3.3 3.8 5.2 7.5 9.2 58 CAL 53 972 96 47 26 19 8. 7 2. 2 1.0 7.6 7.3 2.3 1.6 .33 .28 .43 .55 29 3.4 5.3 5.7 6.8 8.8 10.0 58 CAL 54 981 160 97 68 57 38 18 11 1.4 5.2 5.0 1.3 .8 .36 .29 .24 .71 8 2.6 3.9 4.1 4.7 5.8 6.5 58 CAL 55 999 1,300 880 700 620 440 280 210 81 1.4 1.3 .9 .6 .23 . 14 .08 .90 0 -0.38 0. 51 0. 69 1.2 1.8 2.3 58 CAL 56 1,012 1,100 710 440 340 210 130 91 18 2.3 2.2 1.1 .7 .06 .00 .00 1.00 3 -0.13 1.2 1.6 2.3 2.9 3.5 58 CAL 57 1,037 280 61 26 15 3.8 1.2 7.9 1.8 -.09 -.16 1.25 45 1.8 6.1 8.0 9.7 PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C55 Table 5.—Particle-size data for sediments from Mendota, Cantua Creek, and Huron cores, Los Banos-Kettleman City area—Continued Sample Depth below land Percentiles ( microns^ Means Deviations Skewness Finer than 3 microns surface (feet) 1 (C) 5 16 25 50 (Md) 75 84 95 M+ QM QD, a* Skq« QD, Shg* Sk (per- cent) Cantua Creek core—Continued 58 CAL 58 1,043 320 97 31 16 3.2 49 1.6 8.3 58 CAL 59 1,154 410 200 96 62 20 5.1 2.4 6.0 5.8 2.7 1.8 0.15 0.09 0.17 0. 79 19 1.3 3.4 4.0 5.6 7.6 8.7 58 CAL 60 1,181 430 270 110 34 1.6 56 1.2 9.3 58 CAL 61 1,190 140 87 52 39 17 1.7 6.9 2.3 .47 1.06 .23 29 2.8 4.7 5.9 9.2 58 CAL 62 . 1,203 400 270 110 44 2.8 51 1.3 8.5 58 CAL 63 1,225 190 98 54 41 23 9.1 4.4 6.0 5.7 1.8 1.1 .32 .23 .25 .71 13 2.4 4.2 4.6 5.4 6.8 7.8 58 CAL 64 1,238 210 48 22 16 6.7 2.0 1.0 7.7 7.5 2.2 1. 5 .23 . 17 .25 .71 32 2.2 5.5 6.0 7.2 9.0 10.0 58 CAL 65 1,241 220 130 83 68 44 17 8.8 5.2 4.9 1.6 1.0 .43 .37 .37 .60 10 2.2 3.6 3.9 4.5 5.9 6.8 58 CAL 66 1,255 180 61 34 26 15 8.0 4.9 6.3 6.1 1. 4 .8 . 15 .07 . 06 .92 12 2.5 4.9 5.3 6.1 7.0 7.7 58 CAL 67 1,280 100 52 37 31 15 3.4 1.6 7.0 6. 6 2.3 1. 6 .42 .34 .54 .47 23 3.3 4.8 5.0 6.1 8.2 9.3 58 CAL 68 1,326 290 140 26 15 4.4 1.3 7.8 1.8 -.01 -.01 1.01 43 1.8 6.1 7.8 9.6 58 CAL 69 1,332 350 220 150 130 99 70 49 1.0 3.5 3.4 .8 .4 .25 .11 .05 .93 6 1.5 2.7 2.9 3.3 3.8 4.4 58 CAL 70 1,352 350 160 84 63 30 10 1.8 6.3 5.3 2.8 1.3 . 46 . 19 . 25 . 70 17 1.5 3.6 4.0 5.1 6.6 9.1 58 CAL 71 1,364 280 220 180 160 110 63 46 18 3.5 3.3 1.0 .7 .28 .19 .13 .83 2 1.8 2.5 2.6 3.2 4.0 4.4 58 CAL 72 1,372 480 260 130 95 56 31 21 5.3 4.3 4.2 1.3 .8 .07 .05 .04 .94 4 1.1 2.9 3.4 4.2 5.0 5.6 58 CAL 73 1,392 260 200 150 110 38 8.7 4.5 1.3 5.3 5.0 2.5 1.8 .22 .16 .29 .66 11 1.9 2.7 3.2 4.7 6.8 7.8 58 CAL 74 1,402 450 370 290 240 140 51 23 3.6 3.2 1.8 1.1 .42 .30 .33 . 62 9 1.1 1.8 2.1 2.8 4.3 5.4 58 CAL 75 1,414 1,600 800 330 190 61 3.5 5.3 2.9 .43 1.24 .18 24 -.68 2.4 4.0 8.2 58 CAL 76 1,422 450 340 200 140 65 14 3.6 5. 2 4.5 2.9 1.7 .44 .34 .56 .46 15 1.1 2.3 2.8 3.9 6.2 8.1 58 CAL 77 1,432 570 330 57 23 4.9 .9 7. 8 2.3 .05 . 11 . 86 42 .81 5.4 7.7 10.1 58 CAL 78 1,459 23 13 7.4 5.4 2.6 1.3 8.6 1.0 -.03 -.03 1.05 56 5.4 7.5 8.6 9.6 58 CAL 79 1,476 120 75 42 29 8.6 1.5 7.2 2.1 .18 . 38 . 57 32 3.1 5.1 6.9 9.4 58 CAL 80.. 1,483 100 58 38 29 12 3.0 1.0 7.3 6.7 2.6 1. 6 .37 .22 .36 .60 25 3.3 4.7 5.1 6.4 8.4 10.0 58 CAL 81- 1,496 480 380 240 160 51 12 1.5 5.7 4.5 3.7 1.9 .39 .12 .22 .74 18 1.1 2.1 2.6 4.3 6.4 9.4 58 CAL 82 1,507 360 250 180 140 59 16 3.8 5.3 4.4 2.8 1. 6 .42 .21 .32 .64 15 1.5 2.5 2.8 4.1 6.0 8.0 58 CAL 83 1,507 460 260 150 100 14 1.0 6.6 3.3 . 14 .48 . 51 34 1.1 3.3 6.2 10.0 58 CAL 84 1, 526 390 180 48 30 10 2.3 6.9 1. 8 . 15 .27 . 69 28 1.4 5.1 6.6 8.8 58 CAL 85 1,551 870 610 420 350 240 160 120 21 2.2 2.1 .9 .6 . 10 .02 .01 .97 3 .20 1.3 1.5 2.1 2.6 3.1 58 CAL 86 1,558 130 55 19 9. 7 3.1 1.3 8.1 1. 4 -. 13 -. 19 1.31 49 2.9 6.7 8.3 9.6 58 CAL 87 1,566 690 400 210 150 66 13 4.5 1.8 .33 . 58 .45 18 .54 2.7 3.9 6.3 58 CAL 88 1,590 55 30 13 8.0 5.0 2.6 7.8 .8 . 17 . 14 .83 26 4.2 7.0 7.6 8.6 58 CAL 89 1,631 160 68 22 11 3.7 1.3 8.0 1.5 -.02 -. 03 1. 04 43 2.6 6.5 8.1 9.6 58 CAL 90 1,677 260 160 81 52 15 1.1 7.0 2.8 .36 . 99 .25 34 1.9 4.3 6.1 9.8 58 CAL 91 1,714 400 270 120 77 20 1.4 6.6 2.9 .33 .95 .27 30 1.3 3.7 5.6 9.5 ■ 58 CAL 92 1,752 640 310 160 98 4.1 47 0.64 7.9 38 CAL 93 1,793 380 260 160 120 62 9.5 2.3 5.7 4.9 3.1 1.8 .55 .48 .88 .30 17 1.4 2.6 3.1 4.0 6.7 8.8 58 CAL 94.. _ 1,838 180 140 100 88 59 18 6.5 5.3 4. 7 2.0 1.1 .61 .50 . 57 . 46 12 2.5 3.3 3.5 4.1 5.8 7.3 58 CAL 95 1,872 58 40 24 18 9.5 3.4 1.5 7.4 7.0 2.0 1.2 .33 .23 .28 .68 23 4.1 5.4 5.8 6.7 8.2 9.4 58 CAL 96 1,917 76 36 20 14 6.9 1.6 7.7 1.6 .35 .54 .47 34 3.7 6.2 7.2 9.3 58 CAL 97 1,953 240 190 130 75 6.8 42 2.1 7.2 58 CAL 98 1,990 1,700 1,300 740 460 86 1.6 5.2 4. 1 .41 1.66 . 10 30 -.77 1.1 3.5 9.3 Huron core 57 CAL 104 90 220 66 13 8.1 2.6 53 57 CAL 105 160 2.3 430 310 170 100 8.6 20 2.4 6.0 2.7 0.14 0.37 0.60 27 1.2 3.3 5.6 8.7 C56 MECHANICS OF AQUIFER SYSTEMS Table 5.—Particle-size data for sediments from Mendota, Cantua Creek, and Huron cores, Los Banos-Kettleman City area—Continued Sample Depth below land surface (feet) Percentiles (miCr0nS) Means Deviations Skewness Finer than 3 1 (C) 5 16 25 50 (Md) 75 84 95 M+ QD, a* Skit QDt Skqt Sic (per- cent) Huron core—Continued 57 CAL 106 234 380 240 130 97 47 11 3.5 5.5 4.9 2.6 1.6 0.44 0.34 0.53 0.48 15 1.4 2.9 3.4 4.4 6.5 8.2 57 CAL 107 271 380 120 15 6.8 2.0 58 1.4 9.0 57 CAL 108 310 450 350 210 140 50 4.4 5.3 2.5 .41 1.01 .25 23 1.2 2.8 4.3 7.8 57 CAL 109 351 260 89 26 14 3.6 46 1.9 8.1 57 CAL 110 400 450 390 320 290 240 150 83 2.6 2.3 1.0 .5 .57 .42 .20 .76 7 1.2 1.6 1.8 2.1 2.7 3.6 57 CAL 111 431 390 190 51 26 5.9 43 1.4 7.4 57 CAL 112 476 55 16 8.8 6.5 3.2 1.0 8.6 1.3 .24 .33 .63 48 4.2 7.3 8.3 10.0 57 CAL 113 510 380 280 190 170 130 48 10 4.5 3.5 2.1 .9 .75 .58 .53 .48 12 1.4 2.4 2.6 2.9 4.4 6.6 57 CAL 114 553 320 140 50 30 10 2.4 6.9 1.8 .13 .24 .72 27 1.6 5.1 6.6 8.7 57 CAL 115 594 350 180 130 100 58 29 13 4.6 4.2 1.7 .9 .30 . 11 . 10 .86 9 1.5 2.9 3.3 4.1 5.1 6.3 57 CAL 116 631 350 230 170 140 72 21 10 4.6 4.2 2.0 1.4 .39 .29 .40 .57 9 1.5 2.6 2.8 3.8 5.6 6.6 57 CAL 117 676 440 350 290 260 200 130 100 1.5 2.6 2.4 .8 .5 .30 .24 .12 .84 6 1.2 1.8 1.9 2.3 2.9 3.3 57 CAL 118 713 360 250 190 170 150 110 75 3.1 2.9 .7 .3 .49 .42 .13 .83 6 1.5 2.4 2.6 2.7 3.2 3.7 57 CAL 119 727 240 200 160 140 100 64 34 3.8 3.4 1.1 .6 .39 .14 .08 .90 9 2.1 2.6 2.8 3.3 4.0 4.9 57 CAL 120.... 732 280 120 41 27 13 2.7 6.9 1.7 .36 .60 .43 26 1.8 5.2 6.3 8.5 57 CAL 121... 746 470 180 91 66 23 2.1 6.4 2.5 .39 .97 .26 27 1.1 3.9 5.4 8.9 57 CAL 122. 767 880 650 480 420 320 230 170 1.8 1.7 .7 .4 .23 .09 .04 .94 7 0.18 1.1 1.3 1.6 2.1 2.6 57 CAL 123 779 250 120 50 35 15 3.3 1.3 7.0 6.6 2.6 1.7 .34 .28 .48 .51 24 2.0 4.3 4.8 6.1 8.2 9.6 57 CAL 124 789 320 83 56 46 30 15 6.1 5.8 5.2 1.6 .8 .44 .23 .19 .77 12 1.6 4.2 4.4 5.1 6.1 7.4 57 CAL 125... 800 160 37 22 15 6.5 2.6 1.6 7.4 7.3 1.9 1.3 .07 .04 .05 .92 28 2.6 5.5 6.1 7.3 8.6 9.3 57 CAL 126 . 810 260 160 79 49 18 3.1 1.3 6.6 6.3 3.0 2.0 .28 .27 .54 .47 24 1.9 3.7 4.4 6.8 8.3 9.6 57 CAL 127. 831 260 160 81 51 12 1.8 6.7 2.4 .13 .32 .64 30 1.9 4.3 6.4 9.1 57 CAL 128... 861 220 120 59 42 21 7.9 3.4 6.1 5.8 2.1 1.2 .28 .16 .20 .75 15 2.2 4.1 4.6 5.6 7.0 8.2 57 CAL 129.. 870 330 210 140 100 45 16 6.9 5.0 4.6 2.2 1.3 .25 .13 .17 .79 11 1.6 2.8 3.3 4.5 6.0 7.2 57 CAL 130 870 410 240 120 71 21 4.3 1.6 6.2 5.8 3.1 2.0 .19 .13 .27 .69 22 1.3 3.1 3.8 5.6 7.9 9.3 57 CAL 131 889 210 33 11 6.7 2.0 59 2.3 9.0 57 CAL 132 906 450 320 160 90 8.5 1.5 1.0 6.3 6.4 3.7 3.0 -.16 -. 16 -.46 1.87 37 1.1 2.6 3.5 6.9 9.4 10.0 57 CAL 133. 937 230 140 81 61 23 5.7 2.2 6.2 5.7 2.6 1.7 .30 .18 .30 .66 18 2.1 3.6 4.0 5.4 7.5 8.8 57 CAL 134 946 210 48 15 11 5.5 2.5 1.7 7.6 7.6 1.6 1.1 .08 .06 .06 .91 31 2.3 6.1 6.5 7.5 8.6 9.2 57 CAL 135 948 290 120 28 14 3.4 1.1 8.0 1.8 -.11 -.21 1.33 47 1.8 6.2 8.2 9.8 57 CAL 136 958 1,200 510 320 250 120 17 4.2 4.8 3.9 3.1 1.9 .55 .45 .88 .30 14 -0.26 1.6 2.0 3.1 5.9 7.9 57 CAL 137 972 300 150 27 12 3.9 1.4 7.9 1.5 -.05 -.07 1.10 43 1.7 6.4 8.0 9.5 57 CAL 138 983 280 98 35 21 8.1 2.4 7.1 1.6 .12 .18 .77 28 1.8 5.6 6.9 8.7 57 CAL 139 994 310 180 120 100 60 20 10 1.2 4.8 4.5 1.8 1.2 .44 .36 .42 .56 7 1.7 3.1 3.3 4.1 5.6 6.6 s 57 CAL 140 1,003 450 340 240 180 72 12 3.0 5.2 4.4 3.2 2.0 .45 .32 .62 .42 16 1.2 2.1 2.5 3.8 6.4 8.4 57 CAL 141 1.028 220 84 25 14 4.6 1.3 7.9 1.7 .06 .11 .86 40 2.2 6.2 7.8 9.6 57 CAL 142 1,032 380 280 180 130 58 7.6 2.5 5.6 5.0 3.1 2.0 .47 .43 .88 .29 17 1.4 2.5 2.9 4.1 7.0 8.6 57 CAL 143 1,042 460 360 270 240 180 110 76 4.0 2.8 2.6 .9 .6 .36 .27 .15 .81 5 1.1 1.9 2.1 2.5 3.2 3.7 57 CAL 144 1,094 270 120 49 29 82 2.1 7.0 1.9 .04 .07 .91 20 1.9 5.1 6.9 8.9 57 CAL 145 1,105 140 38 17 5. 2 1. 4 7.7 1.8 . 05 . 09 .88 38 1.7 5.9 7.6 9.5 57 CAL 146 1.120 240 85 21 13 4.8 1. 4 7.9 1.6 . 11 .17 .79 38 2.1 6.3 7.7 9.5 57 CAL 147 1.132 280 90 41 9. 9 1.3 7.1 2.5 .18 . 44 .54 33 1.3 4.6 6.7 9.6 57 CAL 148 1.144 150 16 9. 6 3. 5 1. 4 8. 1 1. 4 -.05 -.07 1.10 46 1.7 6.7 8.2 9.5 57 CAL 149 1,145 320 160 81 57 28 11 4.8 5.7 5.3 2.0 1.2 .25 .13 . 16 .80 14 1.6 3.6 4.1 5.2 6.5 7.7 57 CAL 150 1.160 170 100 62 48 26 10 4.9 5.8 5.5 1.8 1.1 .31 .21 .24 .71 2.6 4.0 4.4 5.3 6.6 7.7 PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C57 Table 5.—Particle-size data for sediments from Mendota, Cantua Creek, and Huron cores, Los Banos-Kettleman City area—Continued Sample Depth below land surface (feet) Percentiles ^ microns 0 ) Means Deviations Skewness Finer than 3 microns 1 (C) 5 16 25 50 (Md) 75 84 95 M* QM* QD* a* Skq* QD* Skq* Sk (per- cent) Huron core—Continued 57 CAL 151 1,180 470 220 17 5.3 1.6 66 1.1 9.3 57 CAL 152 1,199 440 340 200 140 37 5.4 1.9 5.7 5.2 3.4 2.3 0.27 0.18 0. 42 0.55 20 1.2 2.3 2.8 4.8 7.5 9.0 57 CAL 153 1,209 250 140 50 33 15 6.5 4.0 1.1 6.1 6.1 1.8 1.2 .04 .03 .03 .95 13 2.0 4.3 4.9 6.1 7.3 8.0 57 CAL 154 1,216 640 310 170 120 36 7.4 3.5 5.4 5.1 2.8 2.0 .20 .13 .27 .69 14 0.64 2.6 3.1 4.8 7.1 8.2 57 CAL 155 1,232 270 170 130 100 54 14 3.7 5.5 4.7 2.6 1.4 .51 .37 .53 .48 14 1.9 2.9 3.3 4.2 6.2 8.1 57 CAL 156 1,248 4, 900 1,100 600 510 290 100 30 2.9 2.1 2.2 1.2 .51 .30 .35 .61 9 -2.3 0.7 1.0 1.8 3.3 5.1 1,263 270 110 20 12 4.3 42 1.9 7.9 57 CAL 158 1,284 340 200 92 40 5.4 1. 4 7.1 2.4 -.19 -.47 1.92 38 1.6 4.6 7.5 9.5 57 CAL 159 1,291 200 71 22 14 5.1 1.4 7.8 1.7 .12 .20 .75 38 2.3 6.2 7.6 9.5 57 CAL 160 1,306 450 290 160 110 14 1.6 6.2 3.1 .02 .07 .90 33 1.2 3.2 6.2 9.3 57 CAL 161 1,321 340 150 58 30 9.0 1.8 7.1 2.0 .14 .29 .67 31 1.6 5.1 6.8 9.1 57 CAL 162 1,347 420 280 170 120 28 3.7 2.0 5.8 5.6 3.2 2.5 .19 .16 .41 .57 22 1.3 2.6 3.1 5.2 8.1 9.0 57 CAL 163 1,357 370 130 28 16 4.1 1.0 8.0 2.0 .02 .04 .95 44 1.4 6.0 7.9 10.0 57 CAL 164 1,376 260 120 39 26 10 2.8 6.9 1.6 .14 .23 .73 26 1.9 5.3 6.6 8.5 57 CAL 165 1,392 450 150 32 15 4.2 1.2 7.9 1.8 -.01 -.02 1.02 43 1.2 6.1 7.9 9.7 57 CAL 166. 1,417 310 210 100 49 14 3.3 1.5 6.3 6.3 3.0 1.9 .06 .07 .13 .82 24 1.7 3.3 4.4 6.2 8.2 9.4 57 CAL 167 1,428 330 180 70 38 9.2 1.7 7.0 2.2 .09 .20 .76 32 1.6 4.7 6.8 9.2 57 CAL 168 1,433 380 270 140 87 23 5.1 1.8 6.0 5.6 3.1 2.0 .17 .06 .13 .84 19 1.4 2.8 3.5 5.4 7.6 9.1 57 CAL 169 1,454 390 260 110 43 10 2.8 1.0 6.6 6.5 3.4 2.0 -.02 -.07 -.13 1.20 26 1.4 3.2 4.5 6.6 8.5 10.0 57 CAL 170 1,480 350 190 68 36 9.4 2.5 6.7 1.9 -.01 -.01 1.02 27 1.5 4.8 6.7 8.6 57 CAL 171 1,484 260 73 30 23 12 5.1 2.6 6.8 6.5 1.8 1.1 .25 .14 .15 .81 17 1.9 5.1 5.4 6.4 7.6 8.6 57 CAL 172.. 1,498 370 260 130 75 14 2.6 1.0 6.5 6.2 3.5 2.4 .08 .00 .00 .99 27 1.4 2.9 3.7 6.2 8.6 10.0 57 CAL 173 1,518 320 130 60 41 14 3.6 1.3 6.8 6.4 2.8 1.8 .24 .11 .20 .75 23 1.6 4.1 4.6 6.2 8.1 9.6 57 CAL 174 1,528 410 300 180 120 39 7.1 1.9 5.8 5.1 3.3 2.0 .33 .21 .42 .56 18 1.3 2.5 3.1 4.7 7.1 9.0 57 CAL 175 1,539 270 160 50 26 6.4 1.4 7.4 2.1 .04 .08 .89 36 1.9 5.3 7.3 9.5 57 CAL 176 1,544 340 200 130 100 48 14 3.1 5.6 4.7 2.7 1.4 .46 .25 .36 .61 16 1.6 2.9 3.3 4.4 6.2 8.3 57 CAL 177 1,551 410 300 210 170 110 44 20 3.9 3.5 1.7 1.0 .45 .36 .35 .62 10 1.3 2.3 2.6 3.2 4.5 5.6 57 CAL 178 1,575 380 270 150 97 27 6.9 5.3 1.9 .03 .06 .92 20 1.4 3.4 5.2 7.2 57 CAL 179 . 1,590 330 190 85 55 20 5.1 1.9 6.3 5.9 2.7 1.7 .24 .15 .26 .70 19 1.6 3.6 4.2 5.6 7.6 9.0 57 CAL 180 1,605 370 240 110 59 30 7.0 2.5 5.9 5.6 2.7 1.5 .31 .36 .56 .46 17 1.4 3.2 4.1 5.1 7.2 8.6 57 CAL 181 1,615 340 220 130 77 16 3.2 1.3 6.3 6.0 3.3 2.3 .09 .01 .02 .96 24 1.6 2.9 3.7 6.0 8.3 9.6 57 CAL 182 1,642 370 240 140 97 30 4.8 1.2 6.3 5.5 3.4 2.2 .35 .22 .47 .52 21 1.4 2.8 3.4 5.1 7.7 9.7 57 CAL 183 1,650 380 250 86 19 3.6 39 1.4 8.1 57 CAL 184 1,669 350 200 61 33 13 2.9 1.3 6.8 6.7 2.8 1.8 .19 .23 .40 .57 25 1.5 4.0 4.9 6.3 8.4 9.6 57 CAL 185 1,678 220 86 38 24 6. 8 1.3 7.5 2.1 . 13 .28 .67 36 2.2 5.4 7.2 9.6 57 CAL 186 1.699 320 210 150 120 47 6.4 1.6 6. 0 5.2 3.3 2.1 .49 .36 .76 .35 19 1.6 2.7 3.1 4.4 7.3 9.3 57 CAL 187 1,719 350 120 35 22 6. 4 1. 4 7.5 2. 0 . 10 .20 .75 35 1.5 5.5 7.3 9.5 57 CAL 188 1,728 300 180 66 39 13 2. 5 6.7 2. 0 .20 .39 . 58 27 1.7 4.7 6.3 8.6 57 CAL 189 1,748 300 130 27 15 5.2 1.8 1. 0 7.6 7.6 2.4 1.5 . 00 . 00 . 00 1. 00 37 1.7 5.2 6.1 7.6 9.1 10.0 57 CAL 190 1,780 290 88 40 2. 0 7.1 1.9 . 18 .34 .62 30 1.8 5.2 6.7 9.0 57 CAL 191 1,800 410 290 150 88 13 37 1.3 6.3 57 CAL 192 1.805 400 270 150 100 37 8.9 5.0 2.3 5.2 5.1 2.4 1.7 . 18 .17 .30 .65 8 1.3 2.7 3.3 4.8 6.8 7.6 57 CAL 193 1,831 230 54 18 13 7.5 3.6 2.3 7.3 7.2 1.5 .9 .15 . 14 . 13 .83 21 2.1 5.8 6.3 7.1 8.1 8.8 57 CAL 194 1.842 280 170 61 34 8. 9 1. 5 7.1 2.2 . 14 .32 .64 34 1.8 4.9 6.8 9.4 57 CAL 195 .. 1,868 410 360 270 200 51 10 5.7 2.3 4.7 4.5 2.8 2.2 .14 .09 . 19 .77 7 1.3 1.9 2.3 4.3 6.6 7.5 57 CAL 196 . 1,873 290 150 85 71 50 12 3.4 5.9 5.1 2.3 1.3 .67 .61 .78 .34 15 1.8 3.6 3.8 4.3 6.4 8.2 C58 MECHANICS OF AQUIFER SYSTEMS Table 5.—Particle-size data for sediments from Mendota, Cantua Creek, and Huron cores, Los Banos-Kettleman City area—Continued Sample Depth below land surface (feet) Percentiles ^ 'microns\ * ) Means Deviations Skewness Finer than 3 microns (percent) 1 (C) 5 16 25 50 (Md) 75 84 95 M+ QM> QD* ■Sit?* QD* Sit?* Sk Huron core—Continued 57 CAL 197 1,900 230 65 22 14 5.0 1.2 7.9 1.8 0.16 0.29 0.67 39 2.1 6.2 7.6 9.7 57 CAL 198 1,913 300 160 61 32 7.2 1.3 7.3 2.3 .07 .16 0.80 37 1.74 5.0 7.1 9.6 57 CAL 199 1,937 420 310 200 120 9.1 1.2 6.4 3.3 -.12 -.40 1.74 35 1.3 3.1 6.8 9.7 57 CAL 200 1,957 420 280 190 150 49 1.2 6.2 3.5 .54 1.87 0.07 29 1.3 2.7 4.4 9.7 57 CAL 201 1,976 390 290 190 130 7. 3 41 1.4 7.1 57 CAL 202 1,993 340 170 19 1. 9 62 1.6 9.0 57 CAL 203 2, 020 370 220 65 23 6.6 2.0 7.2 1.8 -.02 -.04 1.06 31 1.4 5.4 7.2 9.0 57 CAL 204 2, 050 320 150 61 37 13 4.7 3.3 1.6 6.1 6.2 2.1 1.5 -0.06 -.02 -.03 1.03 14 1.6 4.0 4.8 6.3 7.7 8.2 2,064 140 29 10 2. 0 1.6 9.0 57 CAL 206 2, 092 410 220 37 7.7 2.9 1.4 8.2 1.2 -.15 -.18 1.28 51 1.3 7.0 8.4 9.5 Table 6.—Particle-size data for selected fine-grained sediments from cores and streams, Los Banos-Kettleman City area [Particle-size analyses made by the Hydrologic Laboratory of the U.S. Geological Survey, Denver, Colo.] Sample Depth below land surface (feet) Percentiles (microns) 1 5 16 25 50 75 84 Sand 062*) (per- cent) Silt (4*-62*) (per- cent) Clay («*) (per- cent) Table 6.—Particle-size data for selected fine-grained sediments from cores and streams, Los Banos-Kettleman City area—Con . Depth Percentiles (microns) Sand Silt Clay below 062*) (4/i-62p) «4*) Sample land (per- (per- (per- surface 1 5 16 25 50 75 84 cent) cent) cent) (feet) Oro Lima core 59 CAL 279 154 220 120 51 27 3.8 13.2 36.5 50.3 59 CAL 280. 472 60 30 14 10 5.7 2.4 1.3 .8 61.2 38.0 59 CAL 281 724 110 48 36 19 3.0 1.6 45.6 52.8 59 CAL 282. 823 120 47 25 14 3.0 2.2 43.4 54.4 Mendota core 59 CAL 283. 75 100 74 53 45 14 9.2 51.5 39.3 59 CAL 285. 746 60 43 32 25 11 2.8 1.6 .8 68.2 31.0 59 CAL 286. 981 55 34 16 6.6 1.1 .4 31.6 68.0 59 CAL 287. 1,443 60 32 16 9.8 2.7 — .... .4 43.3 56.3 Cantua Creek core 59 CAL 288. 418 80 50 31 17 1.9 2.0 41.0 57.0 59 CAL 289. 572 58 43 20 8.2 1.3 .4 33.2 66.4 59 CAL 290. 902 120 80 47 21 1.5 10.0 26.0 64.0 59 CAL 291. 1,238 40 20 7.1 3.7 1.0 .0 24.0 76.0 59 CAL 292. 1,632 43 23 11 7.1 3.3 1.5 .0 43.0 57.0 59 CAL 293. 1,952 60 40 15 5.9 1.3 — — .8 28.8 70.4 Huron core 59 CAL 294-59 CAL 295-59 CAL 296-59 CAL 297-59 CAL 298-69 CAL 299- 313 735 905 1,387 1,801 2,093 27 59 100 55 110 100 12 48 60 43 72 55 6.3 42 22 25 50 27 4.6 36 11 15 43 15 2.2 18 2.6 2.9 12 4.2 1.3 1.5 1.9 .... 0.0 .4 4.8 .0 8.5 3.2 29.6 67.7 37.4 46.3 53.5 48.3 70.4 31.9 57.8 53.7 38.0 48.5 Bed sediment, Little Panoche Creek 59 CAL 278- 0 240 160 120 110 63 19 6.7 50.4 37.8 11.8 Bank sediment, Panoche Creek 59 CAL 277- 0 180 120 90 72 31 4.1 1.2 30.2 44.8 25.0 Table 7.—Particle-size data for selected well-sorted sands from Mendota, Cantua Creek, and Huron cores, Los Banos-Kettleman City area Depth below land surface I_______ (feet) 1 (C) [Sieve analyses made by R. H. Meade] ( microns \ Skewness K * ) j 5 16 25 50 (Md) 75 84 95 »r9 QD, I Sit?* QD* Skq9 Mendota core 370 240 180 160 140 110 88 47 0. 5 0. 3 0. 54 0. 26 1. 4 2. 5 2. 6 2. 8 3. 2 3. 5 . 85 350 250 190 170 160 80 25 1. 5 . 5 . 84 1. 5 2. 4 2. 6 2. 6 3. 6 5. 3 .43 . 16 440 290 220 200 150 100 67 . 9 . 5 1. 2 2. 2 2. 3 2. 7 3. 3 3. 9 0. 07 . 46 . 08PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C59 Table 7.—Particle-size data for selected well-sorted sands from Mendota, Cantua Creek, and Huron cores, Los Banos-Kettleman City area—Continued Depth below land surface (feet) Percentiles ( microns \ \ * ) Deviation Skewness 1 (C) 5 16 25 50 (Md) 75 84 95 QDt a SkQd> QD+ Skq4, Mendota core—Continued 880 430 330 260 230 170 1. 2 1. 9 2. 1 2. 6 1, 077 700 320 240 210 150 0. 51 2. 1 2. 3 2. 7 1, 127 1, 200 750 410 310 210 -0. 26 1. 3 1. 7 2. 3 1, 251 2, 100 1, 200 870 720 430 -1. 1 0. 2 0. 47 1. 2 1, 347 590 390 300 280 210 0. 76 1. 7 1. 8 2. 3 120 3. 1 80 3. 6 0. 8 0. 5 0. 27 0. 06 0. 03 97 3. 4 60 4. 1 1. 0 . 6 . 32 . 12 . 07 160 2. 6 120 3. 1 73 . 9 . 5 09 19 09 260 1. 9 190 2. 4 50 1. 3 . 7 09 03 02 150 2. 7 110 3. 2 . 7 . 5 . 29 . 09 . 04 Cantua Creek core 581 1, 700 1, 000 500 410 300 220 180 100 0. 7 0. 4 -0. 01 -0. 02 -0. 01 -0. 77 1. 0 1. 3 1. 7 2. 2 2. 5 590 690 400 260 220 160 100 87 54 . 8 . 6 . 11 . 19 . 11 0. 54 1. 9 2. 2 2. 6 3. 3 3. 5 633 620 220 170 150 110 76 65 38 . 7 . 5 . 10 . 10 . 05 0. 69 2. 6 2. 7 3. 2 3. 7 3. 9 774 420 310 220 190 150 94 68 . 8 . 5 . 34 . 32 . 16 1. 3 2. 2 2. 4 2. 7 3. 4 3. 9 824 520 230 170 150 130 85 57 . 8 . 4 . 51 . 47 . 19 0. 94 2. 6 2. 7 2. 9 3. 6 4. 1 997 1, 100 760 490 440 330 250 210 110 . 6 . 4 . 02 02 01 -0. 13 1. 0 1. 2 1. 6 2. 0 2. 3 1,034 1, 100 580 340 300 250 200 170 74 . 5 . 3 . 03 . 10 . 03 -0. 13 1. 6 1. 7 2. 0 2. 3 2. 6 1,228 1, 400 830 480 370 190 110 98 60 1. 1 . 9 18 11 10 -0. 49 1. 1 1. 4 2. 4 3. 2 3. 4 1,363 500 310 230 210 170 140 120 55 . 5 . 3 . 06 07 02 1. 0 2. 1 2. 3 2. 6 2.8 3. 1 1,420 2, 100 980 530 400 210 130 110 53 1. 1 . 8 18 15 12 -1. 07 0. 9 1. 3 2. 3 2. 9 3. 2 1,550 1, 100 780 490 420 310 240 200 110 . 6 . 4 03 10 04 -0. 13 1. 0 1. 3 1. 7 2. 1 2. 3 1,950 890 510 340 290 270 230 190 97 . 4 . 2 . 21 . 37 . 06 0. 17 1. 6 1. 8 1. 9 2. 1 2. 4 Huron core 632 370 230 180 160 no 56 35 1. 2 0. 8 0. 40 0. 29 0. 22 1. 4 2. 5 2. 6 3. 2 4. 2 4. 8 721 260 160 120 110 85 62 47 . 4 . 25 . 07 . 03 1. 9 3. 1 3. 2 3. 6 4. 0 4. 4 960 1, 300 860 460 280 140 no 92 55 1. 2 . 7 48 49 33 -0. 38 1. 1 1. 8 2. 8 3. 2 3. 4 232-511C60 MECHANICS OF AQUIFER SYSTEMS Table 8.—Particle-size data for cored sedimentst Tulare-Wasco area [Particle-size analyses made by Hydrologic Laboratory of the U.S. Geological Survey, Denver, Colo.] Depth below land „ ./microns \ Mode Deviations Skewness Sample V * / microns \ V ♦ / Skqt QD, surface (feet) 1 (C) 2 5 16 25 50 (.Md) 75 84 95 QD. a* Skqt Pixl ey core 31 1 700 1 500 950 440 280 43 6.5 2.7 0.01 0.01 -0.8 -0.6 0.1 1.2 1.9 4.5 7.3 58 CAL 100 70 360 280 170 80 54 20 6.1 2.5 34 6. 1 2.5 1.6 0. 21 . 11 .17 1.5 1.8 2.5 3.6 4.2 5.6 7.4 8.6 4.9 58 CAL 101 119 1,800 1,600 1,200 530 280 49 8.2 3.1 36 4.6 3.7 2.5 .08 .02 .04 -0.9 -0.7 -0.3 0.9 1.8 4.3 6.9 8.3 4.8 58 CAL 102 155 610 470 280 160 130 65 23 9.9 52 4.6 2.0 1.2 .34 .20 .25 0.7 1.1 1.8 2.6 3.0 4.0 5.4 6.7 4.3 58 CAL 103 194 1,400 1,000 630 300 210 74 20 4.6 42 4.7 3.0 1.7 .33 .12 .20 -0.5 0.0 0.7 1.7 2.3 3.8 5.7 7.8 4.6 58 CAL 104 236 1 000 700 400 170 110 37 5.1 1.6 38 5.9 3.4 2.2 .35 .28 .62 0.0 0.5 1.3 2.6 3.2 4.8 7.6 9.3 4.7 58 CAL 105 269 1,300 920 630 300 180 30 3.7 2.0 35 5.4 3.6 2.8 .08 .08 .23 -0.4 0.1 0.7 1.7 2.5 5.1 8.1 9.0 4.8 58 CAL 106 287 125 68 48 30 24 13 3.6 1.2 28 7.4 2.3 1.4 .49 .37 .51 3.0 3.9 4.4 5.0 5.4 6.2 8.1 9.7 5.2 295 18 8.4 1. 7 1.7 .37 .63 4.5 4.7 5.0 5.6 5.8 6.9 9.2 58 CAL 108 305 790 650 490 360 310 220 150 130 36 230 2.2 .8 .5 .09 .08 .04 0.3 0.6 1.0 1.5 1.7 2.2 2.7 3.0 4.8 2.1 58 CAL 109 317 610 400 210 83 57 27 7.5 1.3 36 6.6 3.0 1.5 .46 .26 .38 0.7 1.3 2.3 3.6 4.1 5.2 7.1 9.6 4.8 58 CAL 110 321 500 430 350 240 160 40 5.0 1.2 38 5.9 3.8 2.5 .32 .21 . 51 1.0 1.2 1.5 2.1 2.7 4.6 7.6 9.7 4.7 336 340 16 1. 6 3.3 . 02 .05 -0.7 -0.4 0.3 1.5 2.8 6.0 9.3 343 290 140 37 22 6.9 1.9 1.0 7.4 2.6 1.7 . 09 . 05 . 08 1.3 1.8 2.8 4.8 5.5 7.2 9.0 10.0 353 59 21 2.3 35 2.3 .37 . 85 1.5 1.9 2.5 3.5 4.1 5.6 8.7 4.8 58 CAL 114 363 1 400 950 600 260 160 53 10 3.1 42 5.1 3.2 2.0 .28 . 19 . 39 -0.4 0.1 0.7 1.9 2.6 4.2 6.6 8.3 4.6 58 CAL 115 371 700 580 310 71 47 21 5.5 1.1 32 6.9 3.0 1.5 .42 . 25 .39 0.5 0.8 1.7 3.8 4.4 5.6 7.5 9.9 4.9 418 74 42 13 1.7 2.3 . 24 . 57 0.8 1.4 2.1 3.8 4.6 6.3 9.2 427 31 2.4 2.7 3.2 4.4 5.0 6.5 5.0 443 0.4 0.8 2.0 4.9 5.8 7.6 451 79 49 27 20 9.9 2.8 1.1 24 7.5 2.3 1.4 .37 .28 . 41 3.0 3.7 4.4 5.2 5.6 6.7 8.5 9.8 5.4 58 CAL 120 465 300 200 110 51 38 20 6.0 1.7 32 6.7 2.5 1.3 . 46 .32 .43 1.7 2.3 3.1 4.3 4.7 5.6 7.4 9.2 5.0 58 CAL 121 476 380 280 190 120 83 32 7.1 2.8 42 5.8 2.7 1.8 .32 .23 . 41 1.4 1.8 2.4 3.1 3.6 4.9 7.1 8.5 4.6 300 200 110 25 12 3.5 1.7 2.3 3.2 5.3 6.3 8.2 496 25 3. 0 36 2.4 .25 . 60 0.7 1.2 1.7 2.7 3.5 5.3 8.4 4.8 58 CAL 124 509 910 660 370 140 88 32 7.8 2.2 37 5.8 3.0 1.7 .28 . 16 . 28 0.1 0.6 1.4 2.8 3.5 5.T) 7.0 8.8 4.8 511 70 38 9.1 1.1 2.5 . 18 . 46 1.3 1.5 2.3 3.8 4.7 6.8 9.8 58 CAL 126 523 420 360 240 150 120 27 2.3 2.8 . 25 . 71 1.2 1.5 2.1 2.7 3.1 5.2 8.8 58 CAL 127 534 300 230 180 120 94 54 22 10 1.1 52 4.8 1.8 1.0 . 35 . 23 . 24 1.7 2.1 2.5 3.1 3.4 4.2 5.5 6.6 9.8 4.3 546 5. 4 1. 4 1.7 . 10 1.5 2.0 3.5 5.2 6.0 7.5 9.5 58 CAL 129 561 230 160 110 64 47 24 7.5 3.4 26 6.1 2.1 1.3 .33 .27 .36 2.1 2.6 3.2 4. 0 4.4 5.4 7.0 8.2 5.2 58 CAL 130 582 1, 700 1, 400 930 640 540 300 140 81 420 2.1 1.5 1. 0 .25 . 13 . 13 -0.7 -0.5 0.1 0.6 0.9 1.8 2.9 3.6 1.2 595 300 190 88 45 8.8 2.2 1.1 6.7 3.2 2.2 -.04 -.07 —. 16 1. 4 1.7 2.4 3.5 4.5 6.8 8.9 9.9 58 CAL 132 601 350 250 160 81 55 22 6.4 2.5 34 6.1 2.5 1.6 .25 . 14 . 22 1.5 2.0 2.6 3.6 4.2 5.5 7.3 8.7 4.9 616 170 62 11 1.8 2.6 .03 . 07 'o.o 0.3 0.8 2.5 4.0 6.5 9.1 58 CAL 134 622 410 350 270 150 110 52 20 11 44 4.6 1.9 1.2 . 20 . 13 . 15 1.3 1.5 1.9 2.8 3.2 4.3 5.6 6.5 4.5 58 CAL 135 631 610 440 300 180 140 77 28 9.0 78 4.6 2.2 1.2 .43 . 24 . 28 0.7 1.2 1.7 2.5 2.8 3.7 5.1 6.8 3.7 .58 CAT, 136 644 560 420 300 180 140 68 19 6.0 80 4.9 2.4 1.4 .43 . 28 . 40 0.8 1.3 1.8 2.5 2.8 3.9 5.7 7.4 3.6 58 CAL 137 654 800 570 360 140 77 26 5.2 1.2 34 6.3 3.5 1.9 .29 . 19 . 37 0.3 0.8 1.5 2.8 3.7 5.3 7.6 9.8 4.9 58 CAL 138 660 420 360 290 190 140 72 27 11 51 4.4 2.0 1.2 .32 . 17 . 20 1.3 1.5 1.8 2.4 2.8 3.8 5.2 6.5 4.3 58 CAL 139 673 930 720 490 180 100 29 5.8 1.4 35 6.0 3.5 2.1 .24 . 11 . 23 0.1 0.5 1.0 2.5 3.3 5.1 7.4 9.5 4.9 58 CAL 140 683 220 150 100 59 44 24 10 5.2 33 5.8 1.8 1.1 .27 . 18 . 19 2.2 2.7 3.3 4.1 4.5 5.4 6.6 7.6 4.9 58 CAL 141 694 710 500 380 250 180 78 18 3.7 160 5.0 3.0 1.7 .44 . 26 .43 0.5 1.0 1.4 2.0 2.4 3.7 5.8 8.1 2.6 58 CAL 142 705 400 310 210 125 92 45 20 10 1.7 40 4.8 1.8 1.1 . 19 .06 1.3 1.7 2.3 3.0 3.4 4.5 5.6 6.6 9.2 4.6 724 400 310 190 69 43 16 4.6 1.9 31 6.5 2.6 1.6 . 19 . 12 1.3 1.7 2.4 3.8 4.5 6.0 7.8 9.1 5.0 Finer than 3 microns (percent) 21 18 16 13 15 21 22 23 32 1 19 22 30 31 26 16 20 31 32 40 26 20 16 46 24 17 35 27 8 37 15 4 31 17 31 9 11 12 20 10 20 11 15 7 20PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C61 Table 8.—Particle-size data for cored sediments, Tulare-Wasco area—Continued Depth below land { microns\ Deviations Skewness Finer Sample \ ^ / microns \ \ * J M* Shu QDt than 3 microns surface (feet) 1 (C) 2 5 16 25 50 (Md) 75 84 95 QT>t a Skq Skq QD* Skq,t, 1 (C) 2 5 16 25 50 (Md) 75 84 95 Richgrove core—Continued 59 CAL 397 1,363 240 230 190 100 60 18 4.4 31 1.9 0.10 0.18 23 2.1 2.2 2.4 3.3 4.1 5.8 7.8 5.0 59 CAL 398 1,370 950 650 430 290 230 130 14 2.0 190 5.4 3.6 2.0 0.70 .62 1.27 17 .1 .6 1.2 1.8 2.1 2.9 6.2 9.0 2.4 59 CAL 399 1,421 1,300 1,100 870 610 520 220 4.7 530 3.4 .63 2.12 22 -0.4 -0.1 .2 .7 1.0 2.2 7.7 0.9 59 CAL 400 1,431 1,800 1,600 1,200 680 530 150 6.2 1.1 680 5.2 4.6 3.2 .53 .43 1.38 21 -0.9 -0.7 -0.3 .6 .9 2.7 7.3 9.8 0.5 59 CAL 401 1,447 200 180 150 100 56 15 2.2 33 2.3 .20 .47 28 2.3 2.5 2.7 3.3 4.2 6.0 8.8 4.9 59 CAL 402 1,492 1,400 1,100 690 380 300 150 48 6.5 260 4.3 2.9 1.3 .53 .23 .30 15 -0.4 -0.1 .5 1.4 1.7 2.8 4.4 7.3 1.9 59 CAL 403 1,527 240 230 190 100 56 14 1.8 31 2. 5 . 18 .45 28 2.1 2.1 2.4 3.3 4.1 6.2 9.1 5.0 59 CAL 404.._ 1,688 230 210 170 130 85 10 1.3 3. 0 . 00 -. 01 31 2.1 2.3 2.5 2.9 3.6 6.6 9.6 59 CAL 405 1,721 250 240 230 200 170 100 26 11 2.8 160 4.4 2.0 1.4 .54 .46 .63 5 2.0 2.0 2. 1 2.4 2.6 3.3 5.3 6.4 8.5 2.6 59 CAL 406 1,752 6,600 5,400 3,800 210 160 85 22 6.4 1.5 120 4.8 2.5 1.4 .49 .37 .53 10 -2.7 -2.4 -1.9 2.3 2.6 3.5 5.5 7.3 9.4 3.0 59 CAL 407 1,785 760 610 430 240 200 110 29 16 4.3 180 4.0 2.0 1.4 .45 .44 .60 4 .4 .7 1.2 2.0 2.4 3.1 5.1 6.0 7.9 2.5 59 CAL 408... 1,803 1,600 1,300 870 370 220 96 33 14 83 3.8 2.3 1.4 . 17 . 13 . 18 10 -.7 -.4 .2 1.4 2.2 3.4 4.9 6.1 3.6 69 CAL 409 1,814 4,000 3, 200 2, 200 1,100 670 190 83 55 3. 7 99 2.0 2.1 1.5 -. 15 -. 19 -. 29 4 -2.0 -1.7 -1.2 -. 1 .6 2.4 3.6 4.2 8.1 3.3 59 CAL 410 1,827 210 190 160 130 89 15 3.8 2.7 1.4 150 5.7 2.8 2.3 -.10 -.11 -. 24 20 2.3 2.4 2.6 2.9 3.5 6.0 8.1 8.5 9.5 2.7 59 CAL 411 1,892 210 200 170 140 130 38 5.3 3.7 2.5 160 5.4 2.6 2.3 .27 .23 .53 20 2.2 2.4 2.5 2.8 3.0 4.7 7.6 8.1 8.7 2.6 59 CAL 412 1,912 540 410 270 120 100 75 27 7.3 75 5.1 2. 0 1. 0 .66 .53 .51 13 .9 1.3 1.9 3.1 3.3 3.7 5.2 7.1 3.7 59 CAL 413 1,943 420 370 300 220 200 150 110 83 51 170 2.9 .7 .4 .20 .13 .06 3 1.2 1.4 1.7 2.2 2.3 2.7 3.2 3.6 4.3 2.6 59 CAL 414 1,956 2,300 1,900 1,500 990 810 540 330 250 120 610 1.0 1.0 .7 .11 . 11 .07 1 -1.2 -.9 -.6 .0 .3 .9 1.6 2.0 3.0 .7 59 CAL 415 1,964 3, 200 2, 700 2,100 1,400 1,100 710 360 210 65 820 .9 1.4 .8 .30 . 18 . 15 1 -1.7 -1.4 -1.0 -.5 -.2 .5 1.5 2.3 3.9 .3 59 CAL 416 2, 010 2, 500 2,100 1,700 1,200 1,100 730 500 300 90 780 .7 1.0 .6 .25 .02 .01 1 -1.3 -1.1 -.8 -.3 -. 1 .5 1.0 1.7 3.5 3.4 59 CAL 417 2, 051 3,500 3,000 2,300 1,300 990 330 180 150 67 210 1.2 1.6 1.2 -.27 -.31 -. 37 1 -1.8 -1.6 -1.2 -. 4 .0 1.6 2.4 2.8 3.9 2.3 59 CAL 418 2,102 14, 000 11, 000 7,300 3,800 2,800 1,300 310 180 71 2, 200 .3 2.2 1.6 .30 .31 .49 1 -3.8 -3.5 -2.9 -1.9 -1.5 -.4 1.7 2.5 3.8 -1.1 59 CAL 419 2,174 1,400 1,200 930 520 410 250 150 110 35 270 2.1 1.1 .7 .09 .05 .04 1 -.5 -.3 . 1 .9 1.3 2.0 2.7 3.2 4.8 1.9 Table 9.—Particle-size data for cored sediments, Santa Clara Valley [Particle-size analyses made by the Hydrologic Laboratory of the U.S. Geological Survey, Denver, Colo.] Depth below land / microns\ Deviations Skewness Finer Sample \ ^ / microns \ \ * / Skq* QD~+ than 3 microns surface (feet) 1 (d) 2 5 16 25 50 (Md) 75 84 95 <7* QD* a Skq* (per- cent) Sunnyvale core 60 CAL 10 37 2,000 620 290 130 88 33 7.7 2.2 40 5.9 2.9 1.8 0.34 0.20 0.35 17 -1.0 0.7 1.8 3.0 3.5 4.9 7.0 8.9 4.7 60 CAL 11 50 4, 000 1,400 200 69 39 11 1.0 2.6 .31 .81 33 -2.0 -0.5 2.3 3.9 4.7 6.5 10.0 60 CAL 12 72 210 180 150 75 44 12 1.8 32 2.3 .20 .47 28 2.3 2.5 2.8 3.7 4.5 6.3 9.1 5.0 60 CAL 13... 91 200 140 79 21 11 3 1 51 2.3 2.8 3.7 5.6 6.4 8.4 60 CAL 14 101 150 98 45 19 13 4.8 1.2 1.7 .18 .30 40 2.8 3.3 4.5 5.7 6.3 7.7 9.7 60 CAL 15 113 140 70 28 7.0 4.6 1. 9 63 2.9 3.8 5.2 7.2 7.8 9.1 60 CAL 16 121 42 30 18 9.3 6.6 2.9 1.0 1.3 .13 .17 49 4.6 5.1 5.8 6.7 7.2 8.4 9.9 60 CAL 17 131 170 140 94 46 31 14 4.6 1.9 29 6. 8 2.3 1.4 .24 .12 .17 20 2.6 2.9 3.4 4.4 5.0 6.2 7.8 9.1 5.1 60 CAL 18 141 9,800 4,900 290 75 35 5.1 43 -3.3 -2.3 1.8 3.7 4.9 7.6 60 CAL 19 151 170 140 62 15 8.8 2. 9 50 2.6 2.9 4.0 6.0 6.8 8.4 60 CAL 20 160 83 51 29 12 8. 5 2.8 53 3.6 4.3 5.1 6.3 6.9 8.5 60 CAL 21 178 26 2.4 2.7 3.0 4.2 7.1 C64 MECHANICS OF AQUIFER SYSTEMS Table 9.—Particle-size data for cored sediments, Santa Clara Valley—Continued Sample Depth below land surface (feet) Percentiles (miC~nS) Mode / microns \ v * ) M+ Deviations Skewness Finer than 3 microns (percent) QD* «<*> Skq4, QD* Skq* 1 (C) 2 5 16 25 50 (Md) 75 84 95 Sunnyvale Core—Continued 192 40 7.6 39 -1.2 1.8 2.1 3.6 4.6 7.0 60 CAL 23 . 210 220 190 120 77 61 27 7.7 3.0 37 6.0 2.3 1.5 0.35 0. 21 0.31 16 2.2 2.4 3.0 3.7 4.0 5.2 7.0 8.4 4.8 223 13 9 0 3. 7 44 3.7 4.4 5.2 6.3 6.8 8.1 fift CAL 25 229 2,800 410 220 120 81 27 6.1 2.6 39 5.8 2.8 1.9 .23 .15 .28 17 -1.5 1.3 2.2 3.1 3.6 5.2 7.4 8.6 4.7 60 CAL 26 236 2,900 2,300 320 130 79 21 4.6 1.8 33 6.0 3.1 2.1 .15 .09 .17 20 -1.6 -1.2 1.6 2.9 3.7 5.5 7.8 9.1 4.9 60 CAL 27 254 2,000 250 170 93 66 27 6.7 3.1 37 5.9 2.5 1.7 .27 .21 .34 15 -1.0 2.0 2.5 3.4 3.9 5.2 7.2 8.3 4.8 307 29 20 7. 2 34 2.8 3.4 4.1 5.1 5.6 7.1 313 370 180 42 24 7.4 1.3 2.1 .19 .40 33 0.8 1.4 2.5 4.6 5.4 7.1 9.6 330 210 150 53 29 6.6 1.5 31 2.1 .00 .00 35 1.8 2.3 2.8 4.3 5.1 7.2 9.4 5.0 60 CAL 31 345 240 200 150 79 52 20 3.4 1.1 34 6.7 3.1 2.0 .35 .30 .59 24 2.1 2.3 2.7 3.7 4.3 5.7 8.2 9.8 4.9 362 130 43 8 5 1.6 2.4 .02 .04 33 -2.2 -1.5 1.2 3.0 4.6 6.9 9.3 409 340 190 110 39 22 6.9 1.0 2.3 .24 .55 37 1.6 2.4 3.2 4.7 5.4 7.2 10.0 60 CAL 34 420 830 470 260 150 110 33 5.9 1.5 44 6.1 3.3 2.1 .35 .19 .40 19 0.3 1.1 2.0 2.7 3.2 4.9 7.4 9.4 4.5 432 130 77 21 2.6 2.5 .22 .55 26 1.1 1.5 2.0 3.0 3.7 5.6 8.6 437 170 no 22 2.9 2.6 .13 .33 25 -3.0 -0.6 1.3 2.5 3.2 5.5 8.4 446 640 180 64 6.7 1.6 2.6 -.23 -.61 33 -0.6 -0.3 0.6 2.5 4.0 7.2 9.2 459 110 53 36 15 3. 6 30 1.7 .26 .43 23 2.3 2.6 3.2 4.2 4.8 6.0 8.1 5.1 60 CAL 39 463 220 200 160 130 92 36 4.2 1.1 50 6.4 3.4 2.2 .47 .39 .86 23 2.2 2.4 2.6 3.0 3.4 4.8 7.9 9.8 4.3 523 130 57 11 1.4 2.7 . 10 .27 31 0.3 0.6 1.3 2.9 4.1 6.5 9.4 545 130 86 37 24 8.9 1.7 27 1.9 .26 .49 31 2.6 2.9 3.5 4.7 5.4 6.8 9.2 5.2 555 140 97 33 4 7 41 2.2 .30 .65 23 -0.7 -0.2 1.6 2.8 3.4 4.9 7.7 4.6 563 60 32 7. 9 1. 2 2.4 . 16 .37 35 1.1 1.6 2.3 4.1 5.0 7.0 9.7 575 150 80 33 22 8.0 1. 7 27 1.8 .20 .37 33 2.2 2.8 3.6 4.9 5.5 7.0 9.2 5.2 606 1,100 390 140 80 16 1.3 3.0 .23 .69 31 -1.3 -1.0 1.4 2.9 3.6 5.9 9.6 60 CAL 46 634 370 280 210 140 no 28 2. 9 2.6 .27 .69 25 1.4 1.8 2.3 2.8 3.2 5.1 8.4 60 CAL 47 657 380 280 200 120 68 8. 7 37 1.4 1.8 2.3 3.0 3.9 6.8 666 8 000 460 120 77 63 19 3.0 42 2.2 .23 .50 25 -3.0 1.1 3.1 3.7 4.0 5.7 8.4 4.6 716 330 240 140 39 19 3.4 48 1.6 2.1 2.8 4.7 5.7 8.2 736 350 290 210 120 79 24 2.1 39 2.6 .35 .92 26 1.5 1.8 2.2 3.1 3.7 5.4 8.9 4.7 745 160 110 69 20 11 2.8 53 2.6 3.2 3.9 5.7 6.5 8.5 757 160 130 80 21 9.3 1. 8 59 2.6 2.9 3.7 5.6 6.8 9.2 60 CAL 53 773 180 140 62 26 17 7.7 2.6 1.4 16 7.4 2.1 1.4 .16 .14 .19 27 2.5 2.8 4.0 5.3 5.9 7.0 8.6 9.5 6.0 790 100 63 17 10 3. 7 1.1 1.6 .08 .13 45 2.0 3.3 4.0 6.0 6.6 8.1 9.9 60 CAL 55 797 240 210 180 130 no 66 25 12 68 4.6 1.7 1.1 .42 .33 .35 9 2.1 2.2 2.5 2.9 3.2 3.9 5.3 6.3 3.9 812 160 125 91 48 29 7.2 1.4 33 2.2 .08 .18 36 2.7 3.0 3.5 4.4 5.1 7.1 9.5 4.9 60 CAL 57 824 67 54 40 25 20 8. 5 1. 8 28 1.7 .29 .50 32 3.9 4.2 4.6 5.3 5.6 6.9 9.1 5.2 60 CAL 58 836 400 360 310 240 210 160 130 80 6.0 180 2.9 .8 .4 .30 .00 .00 4 1.3 1.5 1.7 2.1 2.2 2.6 3.0 3.6 7.4 2.5 60 CAL 59 842 40 32 23 13 9. 7 4.1 1.1 1.6 .21 .34 41 4.6 5.0 5.4 6.2 6.7 7.9 9.8 60 CAL 60 854 140 84 28 8. 5 5.2 1. 9 63 2.8 3.6 5.1 6.9 7.6 9.1 60 CAL 61 866 62 32 13 6.4 4. 4 1. 8 64 4.0 5.0 6.2 7.3 7.8 9.2 60 CAL 62 874 190 170 140 72 44 10 36 2.4 2.6 2.9 3.8 4.5 6.6 60 CAL 63 883 310 250 170 70 43 15 1.2 33 2.6 .40 1.03 31 1.7 2.0 2.6 3.8 4.5 6.1 9.7 4.9 900 120 27 11 2.3 56 2.0 2.4 3.1 5.2 6.5 8.8 910 17 8 1 2 6 55 2.8 3.2 4.3 5.9 6.9 8.6 924 34 7 5 3 7 1 3 72 2.6 3.3 4.9 7.1 8.1 9.6 60 CAL 67 937 300 220 120 22 8.6 .8 65 1.8 2.2 3.1 5.5 6.9 10.3 PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C65 Table 9.—Particle-size data for cored sediments, Santa Clara Valley—Continued Sample Depth below land surface (feet) Percentiles (miCr0nS) Mode / microns \ \ * ) A/0 Deviations Skewness Finer than 3 microns (percent) a* QD* a* Skqt QD Slcq# 1 (C) 2 5 16 25 50 (Md) 75 84 95 Sunnyvale core—Continued 60 CAL 68 959 220 150 110 71 48 8.0 1.1 2.7 0.06 0.15 38 2.2 2.7 3.2 3.8 4.4 7.0 9.9 60 CAL 69 967 1, 000 460 220 43 25 6.1 41 .0 1.1 2.2 4.5 5.3 7.3 San Jose core 60 CAL 70 197 430 320 220 120 60 6.2 45 1.2 1.6 2.2 3.1 4.1 7.3 60 CAL 71 207 120 110 92 70 61 21 5.6 2.1 42 6.3 2.5 1.7 0.31 0.10 0.18 19 3.0 3.2 3.4 3.8 4.0 5.6 7.5 8.9 4.6 60 CAL 72 233 170 125 66 26 17 5.4 1.3 1.8 .11 .21 37 2.5 3.0 3.9 5.3 5.9 7.5 9.6 60 CAL 73 . 258 12,000 8,300 400 78 48 12 33 -3.5 -3.0 1.3 3.7 4.4 6.4 60 CAL 74 276 470 320 180 70 44 16 3.5 1.0 30 6.9 3.1 1.8 .31 .20 .36 23 1.1 1.6 2.5 3.8 4.5 6.0 8.2 10.0 5.0 60 CAL 75 301 4,000 690 220 95 58 19 2.0 34 2.4 .34 .84 27 -2.0 .5 2.2 3.4 4.1 5.7 9.0 4.9 60 CAL 76 324 2,800 1,000 630 410 360 270 170 140 33 300 2.1 .8 .5 .21 . 19 .10 4 -1.5 .0 .7 1.3 1.5 1.9 2.5 2.9 4.9 1.7 60 CAL 77 .. 334 67 49 31 15 11 4.4 1.0 1.7 .27 .46 41 3.9 4.3 5.0 6.0 6.5 7.8 10.0 60 CAL 78 355 290 230 190 130 110 52 17 4.4 50 5.4 2.5 1.3 .45 .23 .30 14 1.8 2.1 2.4 2.9 3.2 4.3 5.9 7.8 4.3 60 CAL 79 402 42 34 26 16 10 3.4 47 4.6 4.9 5.3 6.0 6.6 8.2 60 CAL 80 430 560 390 240 120 71 18 2.2 34 2.5 . 22 . 54 27 0.8 1.4 2.1 3.0 3.8 5.8 8.8 4.9 60 CAL 81 441 740 540 390 250 200 130 63 25 1.1 170 3.7 1.7 .8 .46 .28 .24 7 0.4 0.9 1.3 2.0 2.3 2.9 4.0 5.3 9.9 2.6 60 CAL 82 510 8, 500 6, 000 2, 900 190 110 24 1.8 3.0 .27 .79 28 -3.1 -2.6 -1.5 2.4 3.2 5.4 9.1 60 CAL 83 531 2, 700 1,000 390 150 90 25 2.4 35 2.6 .30 .78 26 -1.5 0.0 1.3 2.7 3.5 5.3 8.7 4.9 60 CAL 84 555 1,400 830 420 200 140 39 6.6 1.1 37 6.1 3.8 2.2 .38 . 16 .35 19 -0.5 0.3 1.3 2.3 2.9 4.7 7.3 9.9 4.8 60 CAL 85 570 500 370 240 130 89 32 7.1 1.5 37 6. 1 3.2 1.8 .36 . 19 .35 20 1.0 1.4 2.1 2.9 3.5 5.0 7.1 9.4 4.8 60 CAL 86.- 599 6, 800 4, 800 1,400 230 160 51 10 2.1 38 5.5 3.4 2.0 .36 .17 .33 17 -2.8 -2.3 -0.5 2.1 2.6 4.3 6.6 8.9 4.7 60 CAL 87 697 4, 000 2, 300 390 110 56 14 2.3 31 2.3 . 14 .33 27 -2.0 -1.2 1.4 3.2 4.2 6.1 8.8 5.0 60 CAL 88 705 5, 400 3 800 2 300 610 390 160 24 5.9 290 4. 1 3.3 2.0 .41 .35 .70 12 -2.4 -1.9 -1.2 0.7 1.4 2.7 5.4 7.4 1.8 60 CAL 89 725 1 200 720 270 88 48 12 35 -0.3 0.5 1.9 3.5 4.4 6.4 60 CAL 90-- 750 27,000 23,000 15,000 8, 500 5, 700 1,500 470 310 51 640 -.7 2.4 1.8 -.03 -.05 -.09 2 -4.8 -4.5 -3.9 -3.1 -2.5 -0.6 1.1 1.7 4.3 0.6 60 CAL 91 791 1,200 410 220 100 69 22 3.6 1.4 37 6.4 3.1 2.1 .28 .22 .47 23 -0.2 1.3 2.2 3.3 3.9 5.5 8.1 9.5 4.8 60 CAL 92 812 170 140 110 61 44 22 7.8 3.3 33 6.1 2.1 1.3 .30 .20 .25 15 2.5 2.8 3.2 4.0 4.5 5.5 7.0 8.2 4.9 60 CAL 93 833 250 200 140 74 51 19 4.4 1.5 33 6.6 2.8 1.8 .29 . 18 .32 22 2.0 2.3 2.9 3.8 4.3 5.7 7.8 9.4 4.9 60 CAL 94 848 220 180 140 74 52 23 6.5 2.2 34 6.3 2.5 1.5 .34 .22 .33 17 2.2 2.5 2.9 3.7 4.3 5.4 7.3 8.8 4.9 60 CAL 95 909 320 230 69 43 16 3.1 1.0 32 6.9 3.1 1.9 .30 .23 .43 25 1.6 2.1 2.7 3.9 4.5 6.0 8.3 10.0 5.0 60 CAL 96 938 470 62 37 11 1. 5 30 2.3 .26 .60 31 1.1 1.6 2.4 4.0 4.8 6.5 9.4 5.1 ANALYTICAL PROCEDURES AND TABULATED RESULTS OF CLAY-MINERAL STUDY CLAY-MINERAL SEPARATION As an aid to the study of clay minerals, material coarser than 2/x is removed from a sediment in order that the characteristics of the clay minerals may be observed more clearly. Three different but similar procedures were used to separate the <2^ fractions of the sediments discussed in this report. The first procedure was used in the Sedimentary Petrology Laboratory of the Geological Survey to separate the clay minerals from 25 samples from the Mendota and Huron cores of the Los Banos-Kettleman City area. It is described by Hathaway (1956). The second procedure was used on the other 76 samples from the Los Banos-Kettleman City area. The third procedure, which improved on the second, was used to separate the clay minerals from sediments of the Tulare-Wasco, Santa Clara Valley, and Arvin-Maricopa areas. The procedure used on most of the samples from the Los Banos-Kettleman City area is as follows. Twenty grams of air-dry fine sediment was— 1. Ground with a wooden pestle in a porcelain dish, 2. Placed in 200-300 ml of 0.05-0. IN sodium hexametaphosphate (Calgon) solution,C66 MECHANICS OF AQUIFER SYSTEMS 3. Stirred for 5-10 minutes with a glass rod and left standing for several days, 4. Stirred mechanically on a Hamilton Beach milkshake machine for 1 minute, and 5. Poured through a 230-mesh (U.S. Standard) sieve, and centri- fuged to split off material coarser than 2/i, 6. The material finer than 2/* was centrifuged until all material coarser than 0.2/i had been removed from the suspension. 7. The concentrated 0.2/*-2.0/i fraction was placed on glass slides (26X45 mm) on which it dried at room temperature and formed oriented aggregates. 8. The aggregates were placed in the X-ray diffractometer for identification of the clay minerals. The high concentration of sodium hexametaphosphate used in step 2 is not recommended for general use because in some samples (especially those from streams and near-surface alluvial-fan deposits) it provided enough sodium to replace the exchangeable calcium and magnesium that had been adsorbed by the clay minerals in their natural state. This made it impossible to draw inferences about, the original adsorbed cations from the X-ray diffraction pattern. The dispersing effect of sodium hexametaphosphate seems to be time dependent: samples that were allowed to soak in the solution for a few days dispersed more readily than samples that had soaked in the solution for only a few hours. No dispers ing agent was added to the samples from the Tulare Wasco area, Arvin-Maricopa area, and Santa Clara Valley; these sediments were dispersed in an ultrasonic generator. Material finer than 0.2/* usually was discarded without being analyzed. This did not seem to introduce significant error into the estimates of clay-mineral proportions because, as table 10 shows, the compositions of the 0.2/*-2.0/* fraction and a finer fraction, 0.1/*-0.2/*, in selected samples, do not differ significantly. More detailed study of the sediments in the Tulare-Wasco area and the Santa Clara Valley, however, indicates that the differences between the two size fractions may be significant—the principal difference being a slightly greater proportion of montmorillonite in the finer clay fraction. In spite of this, the proportion of the clay minerals in the 0.2/*-2.0/* fraction probably represents the proportions of the clay minerals in the sediments as a whole because (1) the bulk of the clay minerals is found in this size fraction and (2) the greater proportion of montmorillonite in the finest clay fraction (<0.2/*) is offset by the lesser proportion in the coarsest fraction (>2.0/*, which was analyzed in a few samples). Hathaway (1956, p. 9) and his associates at the Sedimentary Petrology Laboratory avoided the problem by recovering all the material finer than 2/*, using a filter candle under vacuum to remove water and concentrate the clay suspension. Table 10.—Proportions of clay minerals in two clay-size fractions of sediments from Los Banos- Kettleman City area Clay minerals (estimated parts per ten) Core hole Depth below land surface (feet) Size fraction GO 0) C o o £ c o s Mixed-layer montmorillonite-I illite Illite Low-grade illite-montmorillonite Chlorite and kaolinite-type mineral1 75 0.2-2. 0 7 0 Tr. Tr 2 I) Do 75 . 1- .2 o 1 1 2 D Do 551 . 2-2. 0 6 0 1 Tr. 2 B Do.... 551 . 1- .2 6 o 1 2 I) Do 981 . 2-2. 0 6 0 1 1 2 D Do 981 . 1- .2 7 0 1 Tr. 2 1) Do 1.400 1.400 1, 238 1,238 470 .2-2.0 8 0 Tr. 1 Tr. Do . 1- .2 8 0 Tr. 1 Tr. . 2-2. 0 6 0 1 Tr. 2 I> Do . 1- .2 7 o 2 Tr. 1 D . 2-2. 0 6 o 2 Tr. 2 B Do 470 . 1- .2 6 0 1 Tr. 3 D Stream Material sampled Suspended.. 0. 2-2. 0 2 2 4 0 1 A Do . 1- .2 3 2 3 Tr. 2 D . 2-2. 0 7 0 1 0 2 C Do . 1- .2 7 0 1 Tr. 2 C . 2-2. 0 7 0 1 0 2 I) Do . 1- .2 7 0 1 Tr. 2 D . 2-2. 0 7 0 1 Tr. 2 D Do .1- .2 7 0 1 Tr. 2 D i Letters refer to mineral types shown in fig. 40. The procedure used on the samples from the Tulare-Wasco area, the Arvin-Maricopa area, and the Santa Clara Valley is as follows. About 5 grams of air-dry fine sediment was— 1. Ground with a wooden pestle in a porcelain dish and 2. Placed in about 100 ml of distilled water, stirred briefly, and left standing overnight. 3. The sediment was dispersed (no chemical dispersing agent was added) by an ultrasonic generator for %-1 hr. 4. Concentrated slurries of two size fractions—0.2/*-2.0/* and O.l/j-O.2/*—were separated by centrifuging. 5. Oriented aggregates of the size fractions were made on porous ceramic plates (26x45 mm), such as those described by Kinter and Diamond (1956). The slurries were placed on the plates with a dropj>er, and the water was sucked out of the slurry, through the pores of the plate, by a vacuum pump. 6. The aggregates, when dry, were placed in the X-ray diffrac- tometer for identification of the clay minerals. Several of the sediments from the Richgrove core and all the samples from San Francisco Bay, because they contained substantial amounts of soluble salts, flocculated during the centrifuging process. The salts were washed from these sediments by repeated decanting and centrifuging until the fine-grained material remained dispersed. X-RAY DIFFRACTION The clay minerals were identified by X-ray diffraction using a Norelco diffractometer and nickel-filtered copper radiation. The minimum angular aperturePETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C67 through which the X-ray beam was transmitted was 1°. The oriented clay aggregates were placed in the diffractometer in such a way that the maximum width of the sample intersected by the beam was 26 mm (in the Los Banos-Kettleman City sediments) or 45 mm (in the Tulare-Wasco, Arvin-Maricopa, and Santa Clara Valley sediments). Four diffraction patterns were made from oriented aggregates of most of the samples, as follows: 1. Air dry, 2. Treated with glycerol (most of the Los Banos-Kettle- man City sediments) or ethylene glycol (Tulare-Wasco, Arvin-Maricopa, and Santa Clara Valley sediments), 3. Heated to 400° Celsius (centigrade) for 45-60 min- utes, and 4. Heated to 525° C or 550° C for 45-60 minutes. Diffraction patterns were also recorded from the 0.2/*-2.0/* fractions of samples from the Tulare-Wasco area and Santa Clara Valley that had been suspended in 2N MgCl2 and 5-10 percent glycerol solution. This is the procedure suggested by Walker (1958; 1961, p. 314— 317) for distinguishing between montmorillonite and vermiculite. IDENTIFICATION OF CLAY MINERALS MONTMORILLONITE AND VERMICULITE Figure 39 shows X-ray diffraction patterns of two expanding-lattice minerals. The upper row of patterns shows a montmorillonite (shaded reflections) whose exchange positions are saturated with sodium. The pat- AIR-DRY GLYCEROL 18.0 400°C 9.9 Figure 39.—X-ray diffraction patterns of oriented aggregates of expanding clay minerals. CuKa radiation : scanning speed 2° per minute. Locations of reflections given in Angstrom units. Ordinate is linear intensity. Upper row, Montmorillonite (shaded reflections) from sediment suspended in Cantua Creek. Saturated with sodium hexametaphosphate. Lower row, Mixed-layer montmorillonite-illite (shaded reflections) from depth of 154 feet in Oro Loma core hole. Saturated with soduim by treatment with dithionite and sodium citrate (Mehra and Jackson, 1960).C68 MECHANICS OF AQUIFER SYSTEMS terns for air-dry and glycerol-treated montmorillonite were made at two different scales to show clearly the higher order basal reflections as well as the much stronger (001) reflection. The pattern for montmorillonite heated to 400°C was made at the same scale as the upper patterns for air-dry and glycerol-treated montmorillonite. The patterns in the upper row of figure 39 also contain reflections (unshaded) from type-B chlorite, a kaolinite-type mineral, illite, and quartz. Montmorillonite was identified mainly on the basis of X-ray reflections it gave when expanded with organic liquids: 'an integral series of basal reflections related to 18 A 2 when treated with glycerol, or an integral series related to 17 A when treated with ethylene glycol. As recorded in the X-ray diffraction pattern (not corrected for 26 angle, that is), the intensity (area) of the (001) reflection at 17 or 18 A is 20 or more times the intensity of the higher order basal reflections. Air-dry montmorillonite whose exchange positions are occupied by magnesium or calcium gives broad basal reflections at 15 and 5 A and a diffuse band of reflections in the region between 3.0 and 3.3 A. When its exchange positions are occupied by sodium, air-dry montmorillonite gives a nearly integral series of reflections related to 12.6 A. After the montmorillonite is heated to 400°C, its reflections enhance those of illite at 3.3 and 10 A; a broad and sometimes diffuse reflection appears in the region between 4.8 and 5.1 A, and a diffuse reflection appears near 3.2 A. After the mineral is heated to 525° or 550°C, the intensity of the reflection near 5 A is usually reduced, and the intensity of the 3.2-A reflection, relative to the reflection at 3.3 A, is usually enhanced. Vermiculite was identified by a procedure recommended by Walker (1958; 1961, p. 314-317) : combined treatment with glycerol and either magnesium chloride or sodium hexametaphosphate. According to Walker, the montmorillonite lattice will expand to 18 A after such a treatment, whereas the vermiculite lattice will not expand beyond 15 A. Otherwise, the X-ray diffraction pattern of vermiculite and the responses of vermiculite to treatment with ethylene glycol and heat are similar to those of montmorillonite. Vermiculite was positively identified in only one of the eight cores—the Pixley core from the Tulare-Wasco area. MIXED-LAYER MONTMORILLONITE-ILLITE Another expanding-lattice mineral found in a few of the sediments in the Los Banos-Kettleman City area is tentatively identified as mixed-layer montmorillonite- 2 Angstrom unltrrlO-^cm. illite. X-ray diffraction patterns of a sample of this mineral are shown by the shaded reflections in the lower row of figure 39. This sample was saturated with sodium by treatment with dithionite and sodium citrate (Mehra and Jackson, 1960). The lower row of patterns also contains reflections (unshaded) from illite, type-A chlorite, and quartz. Mixed-layer montmorillonite-illite, when treated with glycerol, gives a diffuse basal reflection at 18 A without giving any detectable higher order basal reflections. When heated to 400° C, the mineral gives an integral series of sharp basal reflections related to 9.9 or 10.0 A. The intensity of the 10-A reflection from the heated mineral is several times greater than one would expect from the intensity of the reflection from the 001 plane of the mineral when it is expanded to 18 A. The diffuse band of reflections in the 10- to 14-A region is typical of the material when it is air dry and saturated with sodium. When the air-dry mineral is saturated with calcium and magnesium, the reflections are somewhat sharper and closer to 14 or 15 A. Although this mineral expands to 18 A when treated with glycerol, the broadness of the 18-A reflection and the sharp X-ray diffraction pattern from the heated specimen indicate that the mineral is very different from the type of montmorillonite illustrated in the upper row of figure 39. In contrast to the montmorillonite, it exhibits the greatest degree of structural order in the collapsed rather than in the expanded state. A mineral with similar X-ray diffraction characteristics has been found in the Pierre Shale and identified as a mixed-layer montmorillonite-illite (L. G. Schultz, 1961, oral commun.). ILLITE Illite is identified on the basis of the following characteristic series of reflections. Reflection Air-dry Glycerol or ethylene-glycol treated Heated to 400° C (001).... 10. 0-10. 2 A 9. 8-10. 0 A Masked by (001) reflection from collapsed montmorillonite. (002) 4. 98A 4. 93-4. 98A 4.98 A. (003) 3. 33A 3. 35A 3.33 A. The slight shifts in the basal spacings of illite when treated with glycerol or ethylene glycol seem to indicate the presence of small amounts of expanding material. The intensities of the (001) and (003) reflections are always several times the intensity of the (002) reflection.PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C69 LOW-GRADE ILUTB-MONTMOHILLONITE MIXTURE Many samples contained small amounts of a material that is interpreted as a poorly crystalline mixture, not necessarily interlayered, of illite and montmorillonite. It gives a diffuse band of reflections between 9.0 and 10.0 A when treated with glycerol, or between 8.5 and 10 A when treated with ethylene glycol. When heated to 400° C, it gives a diffuse band of reflections between 3.1 and 3.3 A and another between 4.8 and 5.0 A. CHLORITE At least two types of chlorite, distinguished from one another on the basis of their crystallinity as inferred from their X-ray diffraction patterns, were found in these sediments. These two are designated arbitrarily “type A” and “type B.” Type A (fig. 40, sample A) gives an integral series of sharp basal reflections related to 14 A that is not changed by heating the mineral to 400° C. Type-B chlorite gives an integral series of reflections related to 14 A of which the (003) reflection at 4.7 A, poorly developed in air-dry specimens, is enhanced by heating to 400° C (fig. 40, sample B). This is presumably also true of the (001) reflection, which is masked by the (001) reflection of montmorillonite in X-ray patterns of air-dry samples. Heating both types of chlorite to 525° or 550° C strengthens the (001) reflection and destroys the higher order reflections. Heating to 650° C (patterns not shown in fig. 40) decreases the intensity of the (001) reflection by about half. In figure 40, the apparent decrease in the intensity of the reflections from chlorites A and B after heating to 400° C was not a result of the heat treatment, but came about during an intermediate treatment with ethylene glycol. Although no decrease in the intensity of the reflections was noted between the glycol and heat treatments of these two samples, heating to 400° C did seem to reduce slightly the intensity of reflections from some chlorites. The type-B chlorite in the Santa Clara Valley is different from the type-B chlorite found in the San Joaquin Valley. Its X-ray diffraction patterns are different from the ones given in figure 40B in that the odd-order reflections are more intense, relative to the even orders, and the reflections at 4.7 and 2.8 A are always clearly visible in patterns from air-dry specimens. The difference does not seem to be in the crystallinity of the chlorite in the Santa Clara Valley: the reflections are as diffuse as those of the type-B chlorite shown in figure 40, and the odd-order reflections are enhanced by heating the mineral to 400° C. The difference may be one of composition. As the odd-order reflections from magnesium-rich chlorites are more intense than the same re- flections from iron-rich chlorites (Brindley and Gillery, 1956), perhaps the chlorite in the Santa Clara Valley contains more magnesium and less iron than the chlorites in the San Joaquin Valley. KAOLINITE-TYPE MINERAL A kaolinite-type mineral was recognized by its two basal reflections near 7.2 and 3.6 A (fig. 40, sample C). In air-diy samples, these reflections are broad, and their peaks are often diffuse—these facts suggest that the mineral is less well crystallized than the type-A and type-B chlorites. After treatment with glycerol or ethylene glycol, the peaks of the reflections may be shifted 0.1 °-0.4° 20, or the reflections may become asymmetrical—the 7-A reflection toward lower 20 angles (larger d spac-ings) and the 3.6-A reflection toward higher 20 angles. In some samples the organic liquids have no apparent effect, whereas in other samples the 3.6-A reflection becomes so diffuse after glycerol or ethylene-glycol treatment that it is barely discernible. After the mineral is heated to 400° C, these reflections are found nearer their air-dry positions, sometimes retaining part of the asymmetry developed during glycerol or etliylene-glycol treatment. After the mineral is heated to 525° or 550° C, these reflections are no longer visible. Although it has the appropriate 7-A structure, the mineral cannot be identified specifically as kaolinite. The mineral sample whose diffraction pattern is shown in figure 40(7 was also examined in the Sedimentary Petrology Laboratory of the Geological Survey: P. D. Blackmon (1961, written commun.) reported that the mineral did not behave as kaolinite when subjected to the intersalation procedure prescribed by Andrew and others (1960)—a reliable means of distinguishing between kaolinite and structurally similar minerals such as chamosite and antigorite. Neither were any hexagonal terminations seen in the sample under the electron microscope. Because the identification of the kaolinite-type mineral or minerals was not pertinent to the aims of this study, other samples were not examined thoroughly. Where a mineral occurred whose X-ray diffraction pattern corresponded to figure 40(7, it was reported as “kaolinite-type mineral” with the understanding that it could be either kaolinite, antigorite, chamosite, or another structurally similar mineral. The kaolinite-type mineral and type-B chlorite commonly occur together in these sediments. The characteristic X-ray diffraction patterns of such a mixture are shown by sample D in figure 40. Double peaks appear at 7.1-7.2 A and at 3.5-3.6 A, and the odd-order reflections are less intense than those from pure type-B chlorite. Heating the mixture overnight in 6 A HC1 destroysC70 MECHANICS OF AQUIFER SYSTEMS 14-15 Figure 40.—X-ray diffraction patterns of oriented aggregates of chlorite and kaolinite-type minerals. CuKa radiation : scanning speed 2° per minute. Reflections from chlorite and kaolinite-type minerals shaded; locations given in Angstrom units. Ordinate is linear intensity. A, Chlorite, well crystallized, from depth of 1,134 feet, Mendota core hole. Bf Chlorite, moderately well crystallized, from depth of 412 feet, Oro Loma core hole. C, Kaolinite-type mineral, from depth of 1,512 feet, Cantua Creek core hole. D, Mixture of chlorite (as in B) and kaolinite-type mineral from sediment suspended in Cantua Creek.PETROLOGY, SEDIMENTS UNDERLYING AREAS the chlorite reflections and leaves reflections at 7.2 and 3.6 A. MINOR CHLORITIC MINERALS Some of the sediments in the Santa Clara Valley contain a material that gives a small but broad reflection near 12 A when heated to 550° C. No other evidence of this mineral was seen in the X-ray diffraction pattern, and no evidence of it at all was seen at lower temperatures. It has been reported by Langston and others (1958, p. 225-227) from sediments in the vicinity of San Francisco Bay, and called by them “Chlorite, 12.3 A.” This material may be a poorly crystallized interlayer mixture of chlorite and some expanding mineral such as montmorillonite. For lack of better information and understanding, the material is referred to in this report as the “the 12-A mineral.” A regular mixed-layer chlorite-illite was identified on the basis of the integral series of basal reflections, 24 A, 12 A, and 8 A. Higher order reflections may be present, but they are masked by reflections from other minerals, notably feldspar. The mineral was noted in only two samples, both of which came from a depth of 2,093 feet in the Huron core in the Los Banos-Kettleman City area. It is a minor constituent of these samples and is insignificant as a constituent of the sediments of the area. Its occurrence is reported here only as a matter of interest. RELATIVE PROPORTIONS OF MINERAL SPECIES Most estimates of the proportions of clay minerals in a sediment are, at best, qualitative and arbitrary. The problems involved in estimating the relative amounts of clay minerals in complex mixtures such as one finds in sediments have been discussed by von Engelhardt (1959), Glenn and Handy (1962), Harward and Thei-sen (1962), Hathaway and Carroll (1954, p. 266-269), Jarvis and others (1957), Johns and others (1954), Nor-rishand Taylor (1962), Oinuma andKobayashi (1961), Schultz (1960, 1964), and Weaver (1958, p. 270-271), but no standard method of estimation has been adopted. Clay mineralogists generally adapt arbitrary systems to the particular clay-mineral assemblages with which they are working. The system used in this study is also arbitrary. Proportions of montmorillonite, illite, mixed-layer montmorillonite-illite, and vermiculite were estimated by comparing the intensity of the reflection at 10 A before heat treatment to its intensity after heating the sample to 400° C. Illite and the expanding minerals were assumed to reflect X-rays with equal intensity at 10 A. The amount of low-grade illite-montmorillonite mixture was estimated from the intensity of the band of reflections between 9.0 and 10.0 A in glycerol-treated OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C71 samples or between 8.5 and 10.0 A in ethylene glycol-treated samples. Proportions of chlorite and kaolinite-type minerals were estimated by a method based on work by Schultz (1960). Type-A chlorite, because of its high degree of crystallinity, was assumed to reflect X-rays at 7 A with twice the intensity that illite reflects X-rays at 10 A. The intensity of the 7-A reflection, therefore, was multiplied by 0.5 and compared with the 10-A reflection. The intensity of the 7-A reflection of type-B chlorite, less well crystallized than type A, was multiplied by 0.75 and compared with the illite reflection The kaolinite-type mineral, less well crystallized than the chlorites, was assumed to reflect X-rays at 7 A with the same intensity that illite reflects X-rays at 10 A. Where chlorite and the kaolinite-type mineral occurred in approximately equivalent amounts (as in sample Z>, fig. 40), the intensity of the 7-A reflection was compared directly with the reflection at 10 A. Because the 12-A reflection is weak and because I have no basis for estimating its abundance, the 12-A mineral is reported as a trace where it is present. Estimated proportions of the clay minerals are expressed in parts per ten and given in tables 11 through 15 and in table 18. Where a small amount of mixed-layer montmorillonite-illite or vermiculite is present with an overwhelming abundance of montmorillonite, it is noted in the tables as a trace and included in the figure for montmorillonite. The reverse is reported for samples in which mixed-layer montmorillonite-illite is much more abundant than montmorillonite. Chlorite and the kaolinite-type mineral are reported in tables 11-13 as “A,” “B,” “C,” or “D,” according to the X-ray diffraction patterns illustrated in figure 40 that approximate the patterns for the sample most closely. Chlorite and the kaolinite-type mineral probably never occur to the complete exclusion of one another, but samples that contain considerably more chlorite than kaolinite-type minerals are reported as pure chlorite with no kaolinite-type mineral, and vice versa. Where the proportions of the two minerals approach equality, the mixture is reported as “D.” EXCHANGEABLE-CATION AND SOLUBLE-ANTON ANALYSES Exchangeable cations were determined by H. C. Star-key and T. Manzanares, of the Sedimentary Petrology Laboratory, by the following procedure. One-gram samples of sediment finer than 2 mm were leached with 1 N neutral NH4C1. Sodium and potassium in the leachates were determined by flame photometry, calcium and magnesium by versene titration. Exchangeable hydrogen was measured by Brown’s (1943) method, 232-511 o—oa 4C72 MECHANICS OF AQUIFER SYSTEMS in samples that registered pH values of less than 7.0. The samples were then washed with alcohol, and the cation-exchange capacities were determined by ammonia distillation. The figures for cations in tables 11 through 15 are the averages of duplicate analyses. Soluble anions were extracted by leaching 10 grams of dry sediment with 500 ml of hot water (temperature near boiling). Anions in the leachate were determined by Claude Huffman, A. J. Bartell, H. H. Lipp, and I. C. Frost, of the Sedimentary Petrology Laboratory. Chloride, bicarbonate, and carbonate were determined volumetrically; sulfate was determined gravimetrically. Where the sum of the anions in the leachate was less than 50 ppm (about 3 milliequivalents per 100 g of sediment) , the individual anions were not determined but the total anions were estimated from the specific conductance of the leachate. The total dissolved salts in the leachate was also estimated from the specific conductance. The cations given in tables 11 through 15 are mostly exchangeable; that is, they represent approximately the ions adsorbed to the basal surfaces of the clay minerals. Exact quantitative evaluation of the amounts of each exchangeable cation species and the relations between species is impossible, however, because the sediments also contain calcite, gypsum, and perhaps other soluble salts. As a first approximation of the true sum of exchangeable cations, the measured sum has been adjusted for soluble salts by subtracting the total equivalents of the anions determined in the hot-water leach. This is only an adjustment in the right direction. It is not a correction, mainly because of the differences in the solubilities of calcite and gypsum in hot water and IN NH4C1. MEASUREMENT OF pH Several types of pH measurements were made, two of them in the Sedimentary Petrology Laboratory. The pH of a mixture, that had been allowed at least half an hour to reach equilibrium, of 1 gram of dry sediment and 10 ml of distilled water was determined in samples from the Tulare-Wasco and Santa Clara Valley cores. Also determined was the pH of the hot water leachates in which the soluble anions were identified. These pH values are listed in tables 11 through 15. In addition to the laboratory determinations, a few measurements were made on selected fine sediments while coring operations were in progress at the Men-dota and Cantua Creek holes in the Los Banos-Kettle-man City area. Because the sediments were too hard for direct insertion of the pH electrodes, the clay had to be disaggregated and dispersed in water before measurements could be made. As soon as it was extracted from the core barrel, a sample of clay was mixed with distilled water (that had been allowed to come to equilibrium with the atmosphere) in proportions of approximately 1 part of clay to 3 parts water by volume. Measurements of pH were made as follows: Depth below land surface (feet) pH of water before clay was added pH of clay-wa Within a few minutes of mixing ter suspension 1 hour after mixing Temperature of suspension (°C.) Mendota core 1 435 7. 9 600 8. 4 980 8. 7 Cantua Creek core 821 . 5. 8 8. 9 12 942 5. 7 8. 6 14 1156 ... 5. 6 9. 6 10 1327 5. 7 9. 1 9. 2 16 1475 5. 7 8. 7 9. 3 15 1836 5. 8 9. 9 9. 6 14 1952 5. 9 8. 3 8. 7 17 i Measurements in Mendota core made by Nikola Prokopovich, U.S. Bur. Reclamation. Although this is a common procedure for measuring the pH of clays (see, for example, Bassett, 1950), precisely what is measured by placing an electrode into a mixture of clay minerals, nonclay minerals, distilled water, and interstitial water containing dissolved salts is obscure. The numerical values given in the table certainly are not to be interpreted rigorously because they are subject to many influences, intrinsic and extraneous. Vigorous stirring of the mixture, for instance, caused the pH meter to register increases of as much as 0.7 pH unit. TABLES OF DATA ON CLAY MINERALS AND CHEMICAL ANALYSES Tables 11 through 15 contain the results of the clay-mineral, exchangeable-cation, and soluble-anion analyses of samples from the Los Banos-Kettleman City area, Tulare-Wasco area, and Santa Clara Valley. Unless otherwise indicated, the clay-mineral proportions reported are those in the 0.2//.-2.0/X fraction. Because the estimated clay-mineral proportions were rounded off to the nearest part in ten, the total of the parts do not add up to 10 in all samples. The cations, cation-exchange capacity, soluble anions, and pH of 10:1 water-sediment mixture were determined using the unfractionated sample ground to pass a 2-mm sieve. Tables 16 and 17 contain data not published elsewhere on the chemical quality of water being pumped from wells near the Sunnyvale and San Jose core holes in the Santa Clara Valley.PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C73 Table 11.—Clay minerals and associated ions in fine-grained sediments from cores in the Los Banos-Kettleman City area [Cations and cation-exchange capacity determined by H. C. Starkey; anions and pH of hot-water leachate by H. H. Lipp, I. C. Frost, and Claude Huffman] Oro Loma core 75 7 0 Tr. Tr. 2 D 230 6 0 1 Tr. 3 D 315 3 6 Tr. 1 Tr. 3 B 399 6 0 1 1 2 D 551 . ...... 6 0 1 Tr. 2 B 554 3 6 0 2 Tr. 2 B 631 7 0 2 0 1 D 642 3 8 0 Tr. Tr. 1 D 693 6 0 2 Tr. 2 J) 699 3 7 0 1 Tr. 2 B 746 6 Tr. 2 Tr. 2 D 746 3 7 0 Tr. Tr. 2 D 780 7 0 1 Tr. 2 B 831 6 0 3 Tr. 1 B 833 6 0 2 Tr. 2 D 932 7 0 2 Tr. 1 D 981 . 6 0 1 1 2 D 984 3 7 0 1 Tr. 2 A ,030 4 3 1 0 2 A ,076 3 7 0 1 0 2 B ,134 7 Tr. 2 0 1 A .280 7 0 2 0 1 B ,351 3 8 0 Tr. 0 1 B ,395 3 8 Tr. Tr. 0 2 B ,400.... 8 0 Tr. 1 Tr. 443 7 Tr. 1 1 1 D ’450 3.... 8 0 Tr. 0 1 B Mean 6 'A Tr. 1 Tr. \y2 bd 25.1 11.6 4.7 0.0 35.2 19.6 35 1.4 4.3 0.0 0.5 6.2 99 7.6 37.1 19.7 2.0 .5 54.6 35.0 50 .8 4.4 .0 .1 5.3 88 8.0 16.2 3.9 3.6 .0 21.2 18.9 25 2.5 40 7.9 28.0 4.7 6.8 .0 38.2 35.5 65 1.3 20 7.7 25.7 4.3 9.0 .0 37.6 35.6 55 2.0 31 7.2 Cantua Creek core 299 6 8 7 7 8 8 7 7 8 6 6 6 9 8 7 7 7 7 5 6 0 0 0 0 0 0 Tr. 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 Tr. Tr. Tr. Tr. Tr. 2 2 1 Tr. Tr. 1 2 2 2 3 0 Tr. Tr. Tr. 0 Tr. Tr. Tr. 0 Tr. Tr. Tr. Tr. Tr. Tr. 0 Tr. 0 1 Tr. 3 D 1 D 2 D 1 B 1 B 2 C 2 D 2 D 1 I) 2 D 2 D 2 D Tr. 1 D 2 C 2 D 1 D 1 D 2 B Tr. 418 22.3 23.6 2.3 0.0 42.4 36.0 45 0.8 2.1 0.0 2.9 5.8 105 7.6 22.8 23.3 2.0 .0 47.1 45.7 70 1.0 16 7.2 652 746 828 902 29.6 18.6 2.0 .0 48.0 37.8 55 2.2 35 7.4 973 1,043 1,154 1,238 1,327 35.8 1.2 8.0 .0 42.2 40.4 70 2.8 44 7.7 1,414 1,512 1.632 12.2 1.3 5.7 .0 16.7 15.0 30 2.5 41 7.8 1,717 1, 792 1,871 1,952 37.1 2.1 16.4 .0 51.4 49.5 80 .8 3.4 .02 <.20 4.2 69 8.5 7 0 1 Tr. 1KD See footnotes at end of table.C74 MECHANICS OF AQUIFER SYSTEMS Table 11.—Clay minerals and associated ions in fine-grained sediments from cores in the Los Banos-Kettleman City area—Continued Depth below land surface (feet) Clay minerals (estimated parts per ten) A ® 1! |1 fa © a o aa f| febfl .a s 25 |I s SB 2 XlM S o Cations (meq/100 g) cSo* •S&e as O 2 og* C c3 c ca , © ** >» as l 0.0 O Anions (meq/100 g) o O o o £ CG MH o o a> 'O © T3 3 © © is a?— 3og oJ!“ Huron core 165 8 0 1 Tr. 1 B 312 1 2 3 8 0 Tr. Tr. 1 B 313 8 0 Tr. Tr. 1 B 25.3 21.4 2.0 0.0 46.2 41.8 55 2.5 41 7.7 470 6 0 2 Tr. 2 B 555 3 8 0 Tr. Tr. 1 B 735 7 Tr. 1 Tr. 2 B 13.5 11.9 2.7 .0 25.3 21.7 30 2.8 45 7.4 735 3 7 Tr. 1 Tr. 2 B 905 8 0 Tr. 0 1 B 43.2 21.2 4.2 .0 65.2 39.8 50 0.4 3.6 0.0 <0.2 3.4 53 7.9 905 3 8 0 Tr. 0 1 B 1,030 8 0 1 e 1 B 1,094 i 8 0 Tr. 0 1 B 1,179 7 0 1 Tr. 2 D 1,251 3 8 0 Tr. Tr. 1 B 1,345 3 9 0 Tr. Tr. 1 B 1,387 8 0 Tr. Tr. 2 B 41.5 6.5 3.6 .0 47.5 41.1 50 .5 3.6 .0 <0.2 4.1 63 8.2 1,524 3 9 0 Tr. Tr. Tr. 1,6013 8 Tr. 1 Tr. 1 B 1,651 7 0 1 1 1 D 1,750 3 9 0 Tr. Tr. 1 D 1,801 7 0 1 1 1 D 26.1 2.2 5.3 .0 19.9 22.9 30 13.6 .1 .0 <•2 13.7 240 6.7 1,899 8 0 1 Tr. 1 D 1,956 3 8 Tr. 1 Tr. 1 D 2,0213 8 Tr. 1 Tr. 1 B 2,093 5 Tr. 3 0 2 D 12.9 6.6 9.2 .0 24.5 18.4 55? .6 3.2 .0 .4 4.2 75 8.0 2,093 * 6 Tr. 2 0 2 D VA 0 1 Tr. 114 B D 1 Letters refer to mineral types shown in figure 40. 3 x-ray analysis made in Sedimentary Petrology Laboratory of the U.S. Geological 2 Sum of cations minus sum of anions. Survey by J. C. Hathaway, H. C. Starkey, and G. W. Chloe; <2/i fraction. Table 12.—Clay minerals and associated ions in surface and near-surface alluvial sediments, Los Banos-Kettleman City area [Cations and cation-exchange capacity determined by H. C. Starkey; anions and pH of hot-water leachate determined by H. H. Lipp, I. C. Frost, and Claude Huffman] Surface and near-surface sediments 1 _ Little Panoche. Suspended.. 0 Tr. 3 6 0 1 A 2 0 2 2 4 0 1 A 3 Moreno Gulch.3 Fan 0 7 Tr. 1 Tr. 2 D do 55 4 Tr. 3 Tr. 3 B 4_. Unnamed 3 4.. do 0 8 Tr. Tr. Tr. 1 D 24 9 0 Tr. 0 Tr. 5 Panoche Suspended.. 0 7 0 1 Tr. 2 D 6 0 7 0 1 Tr. 2 C 7 Arroyo Ciervo.3 Fan. 0 8 0 Tr. Tr. 1 D -..do.3... do 33 8 0 1 Tr. 1 8.. Suspended.. Flood plain. Suspended.. 0 7 0 1 Tr. 2 D 9 0 7 0 1 Tr. 2 D 10 Salt * 0 7 0 1 Tr. 2 D 11 0 7 0 2 0 1 D 71 8 0 1 Tr. 1 D 12 Los Gatos Bed. 0 6 0 1 Tr. 2 D 1 Letters refer to mineral types shown in figure 40. 4 First unnamed stream south of Capita Canyon. 2 Sum of cations minus sum of anions. 5 Sample represents mixture of Salt and Cantua Creeks; Salt Creek contaminated 3 Samples collected by W. B. Bull. at time of sampling.PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C75 Table 13.—Clay minerals and associated ions in fine-grained sediments from cores in Tulare-Wasco area [Cations, cation-exchange capacity and pH of 10:1 water-sediment mixtures determined by H. C. Starkey; anions and pH of hot-water leachate determined by Claude Huffman and A. J. Bartell] 4) Clay minerals (estimated parts per ten) Cations (meq/100 g) Anions (meq/100 g) 8 b- pH •S a? S a> £ O, > ^ D. Depth below land , Se surface (feet) See ■s § 2lc2 X3 Sg£ gSS >»8 g iS ■£ a 4) ow-gri illte- monti Ionite Ss“i O & 4> O Cj bfi a M djuste sum 4 ation^ capac: 100 g) O o 6 § ■3 a $ o £ 3 s 2 r-.sa O t—t A w o S 'A X < o CO « u u w Eh Pixley core 70 0.2-2.0 9 Tr. 0 1C 268 .2-2.0 6 2 0 1C 288 .2-2.0 9 Tr. 0 Tr. 451 .2-2.0 7 1 0 2C 601 .2-2.0 5 2 0 3C 724 .2-2.0 6 2 0 2C Mean .2-2.0 7 1 0 V4C 13.3 20.4 36.3 21.3 20.0 22.4 4.5 2.5 1.3 3.1 1.1 2.5 0.0 1.2 .0 1.8 1.5 1.2 0.0 .0 .0 .0 .0 .0 16.8 23.4 35.6 24.9 21.5 25.1 14.5 21.3 32.8 21.6 18.8 22.5 1.0 16 7.3 8.9 .7 11 7.3 8.7 2.0 32 7.5 8.8 1.3 21 8.4 8.7 1.1 18 7.8 8.8 1.0 15 7.8 8.9 Richgrove core 148 0. 2-2. 0 7 2 0 1 C 22.9 9.4 1.1 0.0 32.6 30.3 0.8 13 7.5 . 1- .2 7 2 0 1 C 232 .2-2.0 5 3 Tr. 1 C 20.0 3.8 .6 .0 23.7 22.1 .7 11 7.6 . 1- .2 7 2 0 1 c 290 .2-2.0 6 3 0 1 c 27.6 3.1 2.4 .0 31.6 31.6 1.5 24 6.7 . 1- .2 7 2 0 2 C 371 - . 2-2. 0 6 3 0 1 C 22.9 3.8 .0 .0 26.1 22.2 .6 9 7.3 . 1- .2 6 2 0 2 C 444 - -. . 2-2. 0 5 4 0 1 c 14.1 3.4 .0 .0 17.1 14.8 .4 6 7.0 . 1- .2 6 2 0 2 C 517.. .2-2.0 6 3 0 1 C 40.7 4.4 .0 .0 43.6 16.7 1.5 24 7.2 . 1- .2 6 2 0 2 C 583_. . 2-2. 0 7 2 Tr. 1 C 26.3 4.9 .0 . 0 30.5 29.0 .7 12 6.7 . 1- .2 8 1 0 1 C 649 .2-2.0 6 3 0 Tr. 22.0 4.5 .0 .0 25.2 25.3 1.3 21 7.1 . 1- .2 6 3 0 1 C 764._ .2-2.0 7 3 0 Tr. 36.8 9.4 4.2 .6 44.8 40.7 1.4 3.7 0.0 0.5 5.6 74 7.7 . 1- .2 8 2 0 Tr. 844.. . ... . 2-2. 0 9 Tr. 0 Tr. 32.1 4.0 3.9 .0 37.3 29.1 2.7 43 7.3 . 1- .2 9 Tr. Tr. Tr. 917 . 2-2. 0 8 Tr. 0 1 D 28. 3 6.3 5.7 .0 35.6 31.9 2.6 2. 1 .0 .0 4.7 62 7.7 . 1- .2 9 Tr. Tr. 1 C <. 1 10 0 0 Tr. 1,036 <2® 8 1 0 1 D 24.3 9.0 6.6 .5 33.2 35.4 4.0 2.7 .0 .0 6. 7 94 7.8 . 2-2. 0 7 1 Tr. 2 D . 1- . 2 8 1 Tr. 1 C 1,156 . 2-2. 0 8 Tr. Tr. 1 D 12.6 6.3 3.8 .0 20.1 21.1 2.6 41 6.8 . 1- .2 8 Tr. Tr. 1 C 1,240 <5 5 8 Tr. 0 1 D 9.4 13.3 6.6 .0 7.5 26. 1 36.3 10.4 .4 .0 .0 10.8 170 6.5 .2-2.0 8 1 0 1 C . 1- .2 9 Tr. 0 Tr. 1,364 .2-2.0 8 Tr. 0 1 D 16.0 6.0 5.7 .0 24.8 24.5 2.9 47 7.5 . 1- .2 8 Tr. Tr. 1 C 1,447 <105 7 1 0 2 D 17.5 12.6 7.4 .0 7.1 25.0 28.7 18.9 .6 .0 .0 19.5 290 6.2 .2-2. 0 9 Tr. 0 1 C . 1- . 2 9 Tr. 0 Tr. 1,527 <10 5 6 2 0 2 D 11. 7 13.2 7.5 .0 10.9 23.0 31.4 19.7 .6 .0 .0 20.3 300 6.2 0.2-2.0 8 Tr. Tr. 1 c .1- .2 9 Tr. Tr. Tr. 1,689 . 2-2.0 9 1 Tr. Tr. 29.0 6.7 10.7 .0 41.2 37.8 3.3 1.9 .0 .0 5.2 69 7.4 . 1- .2 9 Tr. 0 Tr. 1,827 <105 9 Tr. 0 Tr. 8.0 17.5 11.1 .0 13.0 35.1 43.5 13.7 .7 .0 .0 14.4 230 6.7 . 2-2.0 9 Tr. 0 Tr. .1- .2 9 Tr. Tr. Tr. 6.9 1,912 <10 5 7 2 0 1 C 10.6 3.6 2.7 .0 4.0 14.9 11.6 5.2 _ 7 .0 .0 5.9 98 . 2-2.0 8 Tr. Tr. 1 C .1- .2 8 Tr. Tr. 2 C Mean: 148-649 . 2-2.0 6 3 Tr. 1 c 764-1,827.. . 2-2. 0 8 n Tr. 1 D C 1 Refers to clay-mineral determinations only; chemical determinations were made 3 Letters refer to type of X-ray-diffraction pattern shown in figure 40. on unfractionated sediment. 4 Sum of cations minus sum of anions. 2 Includes some vermiculite in samples from Pixley core. 5 Sediment flocculated during centrifuging. 8.4 8.7 8.7 8.9 8.7 9.1 8.6 8.7 8.4 8.7 8.5 8.5 8.6 4.5 8.7 4.0 4.0 7.5 4.1 5.3C76 MECHANICS OF AQUIFER SYSTEMS Table 14.—Clay minerals and associated ions in fine-grained sediments from cores in Santa Clara Valley Clay-minerals determined with assistance of J. B. Corliss; cations, cation-exchange capacity, and pH of 10:1 water-sediment mixture determined by H. C. Starkey and Toribio Manzanares, Jr.; anions and pH of hot-water leachate determined by A. J. Bartel] Clay-mineral size fraction 1 (microns) Clay minerals (estimated parts per ten) Cations (meq/100 g) Cation-exchange capacity (meq/100 g) Anions (meq/100 g) Vi i! pH Depth below land surface (feet) Montmoril- lonite Illite Low-grade illite-mont- morillonite Chlorite (type B) 03 o b£ S 03 M Adjusted sum 2 i o m O O a o O O i Sum Total dissolved in hot-water ] ate (ppm) Hot-water leachate 10:1 water-sediment mixture Sunnyvale core 80 0.2-2.0 5 2 0 3 43.9 9.4 0.0 0.0 51.2 10.4 2.1 34 6.8 8. .1- .2 7 1 0 2 142 . 2-2.0 7 Tr. 0 2 16.6 8.0 .0 .0 21.7 19.3 2.9 46 6.6 7. .1- .2 9 Tr. Tr. 1 222 . 2-2.0 8 Tr. Tr. 2 29.4 12.8 .0 .0 40.6 33.8 1.6 25 6.8 8. .1- .2 9 Tr. Tr. 1 313 - . 2-2. 0 7 1 0 1 13.1 3.5 .0 .0 16.1 19.4 . 5 8 6.8 8. . 1- .2 8 Tr. 0 1 437 . 2-2. 0 7 Tr. 0 2 29.8 6.8 .0 .0 34.3 15.6 2.3 36 7.2 8. .1- .2 9 Tr. Tr. 1 526 . 2-2. 0 8 1 0 1 49.0 21.5 .0 .0 67.7 17.2 2.8 45 7.3 9. .1- .2 9 Tr. Tr. Tr. 606 . 2-2. 0 8 Tr. 0 2 38.3 23.4 .0 .0 57.3 17.3 0.0 4.4 0.0 0.0 4.4 62 8.3 9. . 1- . 2 9 Tr. Tr. 1 656 . 2-2. 0 9 Tr. Tr. 1 67.2 25.9 .0 .0 89.6 21.8 .0 3.5 .0 .0 3.5 51 7.6 9. . 1- .2 9 Tr. Tr. Tr. 746 . 2-2. 0 8 Tr. Tr. 2 46.0 18.8 1.3 .0 61.5 33.6 .6 4.0 .0 .0 4.6 66 7.5 9. . 1- .2 9 Tr. Tr. 1 813 . 2-2. 0 7 Tr. 0 2 16.9 7.1 1.1 . 0 23.5 23.4 1. 6 27 7.0 9. . 1- .2 7 Tr. Tr. 2 901 . 2-2. 0 6 1 0 3 20.9 8.5 1.6 . 0 28.2 24. 0 2. 8 46 7.5 9. .1- .2 8 Tr. 0 2 983 . 2-2. 0 9 Tr. 0 1 29.8 9.4 3.7 . 0 41.7 40.6 1. 2 19 6.7 9. .1-2 9 Tr. 0 Tr. Mean - . . 2-2. 0 7H H Tr. 2 B San Jose core 40 0.2-2. 0 .1- .2 5 7 2 2 0 0 3 2 24.2 8.6 0.0 0.0 29.4 28.0 0.7 2.7 0.0 0.0 3.4 49 7.3 8.5 207 . 2-2. 0 6 1 0 3 21.2 6.2 .0 .0 25.4 27.7 2.0 32 7.1 8.6 .1- .2 7 1 0 2 302 . 2-2. 0 8 1 0 1 11.9 5.1 .0 .0 16.2 16.4 .8 13 6.9 8.5 . 1- .2 9 Tr. 0 1 402 . 2-2. 0 6 1 0 3 21.9 8.3 .0 .0 27.5 26.9 2.7 44 7.0 8.5 .1- .2 8 Tr. 0 1 542 . 2-2.0 7 1 Tr. 2 20.5 7.6 .0 .0 26.7 20.1 1.4 23 7.1 9.1 .1- .2 8 Tr. Tr. 1 727 . 2-2. 0 7 1 0 2 15.1 6.1 . 0 .0 19.6 17.6 1.6 25 7.1 8.9 . 1- .2 8 Tr. 0 2 833 . 2-2. 0 8 Tr. 0 2 43.3 9.5 . 0 .0 50.5 21.9 2.3 37 7.3 9.2 . 1- .2 8 Tr. 0 1 937 . 2-2. 0 7 Tr. Tr. 2 19.6 8.6 .0 .0 26.6 22.0 1.6 26 7.3 9. 1 .1- .2 8 Tr. Tr. 2 Mean . 2-2. 0 7 1 Tr. 2 B 1 Refers to clay-mineral determinations only; chemical determinations were made 2 Sum of cations minus sum of anions, on unfractionated sediments.PETROLOGY, SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE, CENTRAL CALIFORNIA C77 Table 15.—Clay minerals and associated ions in fine-grained surficial sediments from Santa Clara-Valley and southern San Francisco Bay (Clay minerals in samples 1-11 determined with assistance of J. B. Corliss, T. J. Conomos, and J. O. Berkland. Samples 12-19 are grab samples, collected and analyzed by Conomos. Cations, cation-exchange capacity, and pH of 10:1 water-sediment mixtures determined by H.C. Starkey and Toribio Manzanares, Jr.; anions and pH of hot-water leachates determined by A. J. Bartel] Sample No. in fig. 34 Sediment type and location Clay minerals (estimated parts per ten) Cations (meq/100 g) Cation-exchange capacity (meq/lOOg) Anions (meq/100 g) Total dissolved solids in hot-water leachate (ppm) pn Montmorillonite Illite Chlorite and kaolinite-type minerals 1 12-A mineral 03 o be s c3 z Sum 6 GO IICOs 6 0 0 Sum Hot-water leachate 10:1 water-sediment mixture 1. . Alluvial San Francisquito Creek fan. 8 9 7 8 7 7 8 7 6 5 6 6 5 6 7 6 6 6 6 Tr. Tr. 1 1 1 1 Tr. 1 2 3 2 2 2 1 1 2 2 2 2 2 C 1 C 2 D 1 D 2 B 2 B 1 B 2 C 2 B 2 B 2 B 2 B 3 B 2 B 2 B 3 B 2 B 2 B 2 B 0 0 Tr. Tr. Tr. Tr. 0 Tr. Tr. Tr. Tr. Tr. Tr. Tr. 0 Tr. Tr. 0 Tr. 27.6 10.2 0.0 0.0 37.8 36.6 1.0 16 7.0 8.5 2 3 Stevens Creek bank. Los Gatos Creek terrace. Coyote Creek terrace. 4 6 7 8 Alameda Creek bottom. Bay bottom Brewer Island 3_ _. San Francisco Bay. Mayfield Slough.. Coyote Slough San Francisco Bay. 9 23.2 18.1 44.2 1.2 86.7 32.9 8.3 4.5 0.0 40.7 53.6 810 7.4 8.3 10 11 16.1 32.8 55.9 1.2 8.0 114.0 36.2 49.7 .0 .0 58.2 107.9 1,500 4.6 4.0 14 IS 16 17 18 19 1 Letters refer to type of X-ray diffraction pattern shown in figure 40. 3 Reclaimed bay-bottom sediments. 2 Slight soil profile developed. Table 16.—Partial chemical analyses of water from selected wells within about 3 miles of Sunnyvale core hole [Analyses by W. C. Pollard, B. H. Geib, Edelle Hansen, and Ignacio Sokula] Well location (T/R-Sec) Dis- tance from Sunny- vale core hole (mile) Total depth (feet) Perforated interval (feet) Day water sample collected Total dis- solved solids (ppm) Parts per million (upper number) and equivalents per million (lower number) for indicated cations and anions Si02 (ppm) Per- cent Na Top Bot- tom Ca Mg Na K SO4 IIC03 C03 Cl 6S/1W-19 1.3 550 8/14/57 354 58 18 41 1. 6 35 268 0. 0 26 30 29 2. 9 1. 5 1. 8 0. 04 0. 7 4. 4 __ 0. 7 6S/1W-29 2.7 300 8/17/54 288 42 18 31 1. 0 34 220 . 0 15 33 27 2. 1 1. 5 1. 3 0. 03 0. 7 3. 6 0. 4 6S/2W-9 3.1 202 163 185 8/14/57 355 46 15 60 2. 0 27 272 . 0 39 32 42 2 2 1 2 2 6 O l)n 0 6 4 4 1. 1 6S/2W-14 . 4 868 _ do 311 46 14 47 1. 4 27 262 . 0 20 26 37 2. 3 1. 1 2.0 0. 04 0. 6 4. 3 0. 6 6S/2W-16 2. 8 500 .do 542 103 31 38 1. 6 127 327 . 0 45 30 18 5. 1 2. 6 1. 6 0. 04 2. 6 5. 4 1.3 6S/2W-21 _ _ 2. 7 264 8/18/54 539 83 30 48 1. 5 150 249 . 0 50 49 24 4. 1 2. 5 2. 1 0. 04 3. 1 4. 1 1.4 — 6S/2W-24 . 6 550 150 535 8/11/53 324 50 18 40 1. 2 32 268 . 0 20 30 30 2 5 1 5 1 7 0 03 0 7 4 4 0. 6 6S/2W-28 3. 1 320 190 316 8/15/57 361 75 23 22 1.3 22 315 . 0 29 30 15 3.7 1. 9 1.0 0. 03 0.5 5. 2 0. 8 — — 6S/2W-34 3. 3 660 do 294 53 19 21 1. 2 15 249 . 0 20 30 18 2. 6 1. 6 0.9 0. 03 0. 3 4. 1 0. 6 — 6S/2W-36 2. 5 480 __do 444 95 21 33 1. 9 41 322 . 0 50 28 18 4. 7 1. 7 1.4 0. 05 0. 8 5. 3 — 1. 4 — —C78 MECHANICS OF AQUIFER SYSTEMS Table 17.—Partial chemical analyses of water from wells within 200 yards of San Jose core hole [All wells in 12th Street Station of San Jose Water Works; samples collected and analyzed by Water Works: analyst, Primo Villarruz. Well numbers are those assigned by Water Works] Well Total depth (feet) Perforated interval (feet) Day water sample collected Total dis- solved solids (ppm) Parts per million (upper number) and equivalents per million (lower number) for indicated cations and anions SiC>2 Percent Na Top Bottom Ca Mg Na K so< hco3 co3 Cl 4 800 605 780 1/31/62 336 52 19 39 2. 4 40 271 1. 2 18 22 28 2. 6 1. 6 1. 7 0. 06 0. 8 4. 4 0. 04 0. 5 5 800 454 778 do 427 72 34 31 2. 0 60 351 1. 5 23 22 17 3. 6 2. 8 1. 3 0. 05 1. 2 5. 7 0. 05 0. 6 6 794 276 772 2/15/62 387 63 26 36 3. 6 50 311 1. 8 22 21 23 3. 1 2. 1 1. 6 0. 09 1. 0 5. 1 0. 06 0. 6 7 725 278 682 1/31/62 396 74 24 34 2. 0 53 315 1. 2 23 21 21 3. 7 2. 0 1. 5 0. 05 1. 1 5. 2 0. 04 0. 6 8 716 280 697 2/3/62 390 59 32 33 2. 1 52 321 1. 5 22 21 20 3. 0 2. 7 1. 4 0. 05 1. 1 5. 3 0. 05 0. 6 9 800 270 746 4/4/62 408 72 29 32 1. 5 55 329 1. 5 23 23 19 3. 6 2. 4 1. 4 0. 04 1. 1 5. 4 0. 05 0. 6 11 870 306 842 1/22/62 355 47 16 58 2. 5 44 274 2. 1 26 20 40 2. 4 1. 3 2. 5 0. 06 0. 9 4. 5 0. 07 0. 7 Table 18 contains the results of clay-mineral analyses of sediments from the Lakeview test hole in the Arvin-Maricopa area. 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Mon. 5 of Pergamon Press, New York.) ------ 1964, Quantitative interpretation of mineralogieal composition from X-ray and chemical data for the Pierre Shale: U.S. Geol. Survey Prof. Paper 391-C, p. C1-C31, 1 pi. Shepard, F. P., 1954, Nomenclature based on sand-silt-clay ratios: Jour. Sed. Petrology, v. 24, p. 151-158. Shukri, N. M., and Higazy, R. A., 1944, Mechanical analysis of some bottom deposits of the northern Red Sea: Jour. Sed. Petrology, v. 14, p. 43-69. Shumway, George, 1960, Sound speed and absorption studies of marine sediments by a resonance method: Geophysics, v. 25, p. 451-467, 659-682. Sigvaldason, G. E., and White, D. E., 1961, Hydrothermal alteration of rocks in two drill holes at Steamboat Springs, Washoe County, Nevada, in Short papers in geology and hydrology: U.S. Geol. Survey Prof. Paper 424-D, p. D116-D122. Taliaferro, N. L., 1943, Geologic history and structure of the central Coast Ranges of California: California Div. Mines Bull. 118, p. 119-163. Trask, P. D., 1930, Mechanical analyses of sediments by centrifuge : Econ. Geology, v. 25, p. 581-599. Upson, J. E., 1949, Late Pleistocene and Recent changes of sea level along the coast of Santa Barbara County, Calif.: Am. Jour. Sci., v. 247, p. 94-115. Walger, Eckart, 1961, Die Korngrossenverteilung von Einzella-gen sandiger Sedimente und ihre genetische Bedeutung [The grain-size distribution of single layers of sandy sediments and its genetic significance] : Geol. Rundschau, v. 51, p. 494-507. Walker, G. F., 1958, Reactions of expanding-lattice clay minerals with glycerol and ethylene glycol: Clay Minerals Bull., v. 3, p. 302-313. ------ 1961, Vermiculite minerals, in Brown, George, ed., The X-ray identification and crystal structures of clay minerals: London, Mineralogieal Society, p. 297-324. Waugh, A. E., 1952, Elements of statistical method [3d ed.] : New York, McGraw-Hill, 531 p. Weaver, C. E., 1958, Geologic interpretation of argillaceous sediments; Part I. Origin and significance of clay minerals in sedimentary rocks: Am. Assoc. Petroleum Geologists Bull., v. 42, p. 254-271. Wiklander, Lambert, 1955, Cation and anion exchange phenomena, in Bear, F. E., ed., Chemistry of the Soil: Am. Chem. Soc. Mon. 126, p. 107-148. Williams, Howel, Turner, F. J., and Gilbert, C. M., 1955, Petrography—an introduction to the study of rocks in thin sections: San Francisco, Calif., Freeman, 406 p. Wood, P. R., and Dale, R. H., 1964, Geology and ground-water features of the Edison-Maricopa area, Kern County, California : U.S. Geol. Survey Water-Supply Paper 1656, 108 p., 12 pi. Yates, R. G., and Hilpert, L. S., 1945, Quicksilver deposits of central San Benito and northwestern Fresno Counties, California : California Jour. Mines and Geology, v. 41, p. 11-35.INDEX Acknowledgments............................. C5 Alameda Creek (No. 8), clay minerals........45,77 Alluvial-fan deposits___5,7,8,13,16,17,21,27,30, 88 differences between Tulare-Wasco and Los Banos-Kettleman City areas............. 27 distinguishing criteria.................. 7,28 particle sizes....................10,12,13,20 relations between median diameter and other particle-size measures__16,17,88 Amnicola....................................... 9 Anions, soluble, analyses.................... 71 soluble, relation to pH and total salt concentration..................... 37 tables of analytical data______________ 72 Anticline Ridge............................... 5 Arroyo Ciervo (No. 7), clay minerals_____ . 20,74 Artesian pressure, depletion------------------- 2 Arvin-Maricopa area_______________________ . 2,46 clay mineral content of sediments---------- 45 location of Lakeview test hole_____________ 47 B Bartell, A. J., analyst.................. 75,76,77 Berkland, J. O., analyst...................... 77 Biotite_____________________________ 5,21,24,27,35 Brewer, Roy, quoted.-------------------------- 27 Bull, W. B., cited__________________________ 16,18 C Calcite__________________________________ 40,72 Cantua Creek, exchangeable cations_____ .25,74 Cantua Creek (Nos. 8, 9), clay minerals______20,74 Cantua Creek core__________________ 5,9,58,58,73 clay minerals_______ ____________ .. ... 19,73 core-hole location....................... 4 exchangeable cations___________________ 25,73 particle-size distribution________ 12,53,58,59 Cations, exchangeable: analytical procedures_____________________ 71 Cantua Creek........................... 25,74 Little Panoche Creek----------------- 23,25,74 Los Banos-Kettleman City area............ 22 in modem stream sediments______________ 28 in subsurface sediments_________________ 28 Los Gatos Creek (Fresno County, No.T2) . 25,74 Mayfield Slough.. _______ ... ______ 77 Panoche Creek______________________ 23,25,74 relation to cations in associated waters.. 28,86, 44 relation to pH....................... 28,86 San Francisquito Creek_____________ . 77 Santa Clara Valley______ 44 tables of analytical data.. 72 Tulare-Wasco area______ 85 Cenozoic sedimentary rocks.. 5 Chao, T. T., cited........................... 35 Chert...................................... 5,38 Chlorite........ ........... .. 18,22,34,44,46,65 Chloritic minerals, minor... __________________ 71 Clay aggregates....................... _ 8 Clay-mineral study, analytical procedures 65 tabulated results........................ 72 Clay minerals: Alameda Creek (No. 8)___________________ 45,77 Arroyo Ciervo (No. 7)_________________ 20,74 Arvin-Maricopa area_______________________ 45 [Italic page numbers indicate major references] Clay minerals—Continued Page assemblages...................... C 18,84,45,46 Cantua Creek (Nos. 8, 9)________________ 20,74 Coyote Creek__________________________41,45,77 Coyote Slough (No. 12).................45,77 identification criteria____________________ 67 ions associated with................. 22,85,44 Los Banos-Kettleman City area_____ 18,66,73,74 Los Gatos Creek (Fresno County, No. 12). 20,74 Los Gatos Creek (Santa Clara County, No. 4)........................_____ 45,77 Martinez Creek (No. 11)________________20,74 Mayfield Slough (No. 11)...............45,77 Moreno Gulch (Nos. 2,3)_________________ 20,74 Panoche Creek (Nos. 5, 6)................20,74 Salt Creek (No. 10)_________________ 20,74 San Francisco Bay................. 41,45,77 San Francisquito Creek (Nos. 1, 2)_______45,77 Santa Clara Valley................... 48,76,77 sources........................... 18,22,84,44,46 Stevens Creek (No. 3)................... 45,77 total material in sediments__________ 22,85,44 Tulare-Wasco area......................84,75 CM diagrams..........................14,16,17,33,43 Coast Ranges................................ 21,38 Collection of samples...................... 2,48 Compaction........................... 3,6,18,24,47 Conomos, T. J., analyst........................ 77 Corcoran Clay Member of the Tulare Formation, lacustrine deposits_____8,9,12,27 Core-hole sediments, particle-size analyses_ 9, 22,28,41 Coro holes, location and description............. 3 Corliss, J. B., analyst___________________ 76,77,78 Coyote Creek---------------------------- 38,40,41 clay minerals-------------------- ... 41,45,77 Coyote Slough (No. 12), clay minerals ________45,77 Cretaceous sedimentary rocks.__________________ 5 Cutans......................................... 27 D Davis, G. II., cited___________________ 23,24,50 Deltaic deposits_______________________________ 6,9 distinguishing criteria.......... ......... 7 particle sizes_________________________ 10,12 Deposition of sediments, rates_______ 4* relation to particle-size measures_ 18,16,88,48 textural evidence of processes___________ 7,27 Deposits, alluvial-fan. 5,7,8,13,16,17,21,27,28,30,33 alluvial-fan, differences between Tulare-Wasco and Los Banos-Kettleman City areas_____________ ________ 27 particle sizes______ 10,12,13,16,80,33 criteria for distinguishing principal types. 6 deltaic------------------------------ 6,9 particle sizes______ ________ _ 10,12 estuarine, absence of... _________ 40 flood-plain_____________ 5,7,9,11,16,27,28 particle sizes______ ________ ._ 10,12,16,50 lacustrine_______________________ 6,8,9,27 Corcoran Clay Member of the Tulare Formation......... 8 particle sizes________________ 10,12,80 marine...............................21, $4,28 particle sizes______ ____________ 29,80,33 mudflow.................................. 16 types___ ___________________________ 5,24,88 Page Diablo Range.............. C3,5,8,9,77,77,55,22,38 sand description------------------------- 5 Diamond, Sidney, cited........................ 66 Diatoms, lacustrine deposits_________________ 8 marine deposits.........................24,28 Diepenbrock, Alex, cited----------------- 24,31 E Ephemeral streams, defined---------------------- 8 Etchegoin Formation.......................... 3,5 F Fabric of fine-grained sediments....... .. 7,8 Fang, S. C., cited........................... 35 Flood-plain deposits__________ 5,7,5,11, /6,77,27,30 distinguishing criteria......^------ . 7,28 particle sizes......................70,12,50 relations between median diameter and other particle-size measures._. 77 Fluminicola............................. 9,40 yatesiana............................... 40,41 Fossiliferous silts__________________________ 40 Fossils: Amnicola___________________________________ 9 Fluminicola_______ 9,40 yatesiana........................ 40,41 Gyraulus________________________________ 40 Helisoma................................. 40 Littorina................................. 9 Lymnaea.............................. 40 Menetus................................ 40 Pisidium............................. 40 Franciscan Formation______________ 5,18,22,38,44 Fresno County________________________________ 3,18 Frost, I. C., analyst______________________ 73,74 G Gastropods________________________________ 9,40 Geib, B. II., analyst___________________ . 77 Gilbert, C. M., cited.................. . 5 Glaucophane................................. 38 Granitic rocks_________________________________ 18 Graywackes.................................. 18,38 Green, J. H., cited___ . . 38 Guadalupe River....... 38 Gypsum_________ _______ . 38,72 Gyraulus____ 40 H Halloysite_____ ____________________________ 21,35 Hansen, Edelle, analyst.. 77 Harward, M. E., Cited. ... 35 Helisoma... 40 Hilton, G. S., cited__ - 38 Hornblende___________________________________ 5,24 Huffman, Claude, analyst. 73,74,75 Huron core - 6,9,12,23,55,58,74 clay minerals— 75,73 exchangeable cations.................. 25,73 particle-size distribution___ 12,55,58,59 Hydrodynamic sorting______... ------- 15 C81C82 INDEX mite_____________________ 018,21,22,34,41,44,46,68 Illite-montmorillonite mixture, low-grade--- 18, 34,44,69 Inman, D. L., cited_________________________ 14,49 Ions associated with clay minerals. _. 18,22,54,85,43 Janda, R. J., cited J 9,21,34 K Kaolinite_________________________________ 21,34 Kaolinite-type mineral_____________ 18,22,34,46,69 Kinter, E. B., cited___________________________ 66 Klausing, R. L., cited_________________________ 38 Knoxville Formation________________________38,44 Krumbein, W. C., cited_______... ...11,49,50 L Lacustrine deposits__________ _____5,8,9,24,27,30 Corcoran Clay Member of the Tulare Formation_______________________________8,9,12,27 distinguishing criteria_______________ ... 7 particle sizes________________________10,12,80 Lakeview test hole, clay minerals----------- 49,78 location__________________________________ 47 Lipp, H. H., analyst_______________________ 73,74 Little Panoche Creek_________________________22,58 alluvial fan_____________________________ 18 cation composition of water samples.......... 23 clay minerals_______________________ 18,20,74 exchangeable cations.......... ....... 23,25,74 Little Panoche drainage basin__________________ 18 Littorina................................... 9 Lofgren, B. E., cited__________________________ 24 Los Banos-Kettleman City area__________________ 2, 3,5, 6, 7,8,16,17,18,22,24,29,58, 66 age of sediments_________________________ 3 alluvial-fan deposits___________________ 8,17 cation composition of streams and ground waters............................ 23 clay-mineral composition of sediments. 18,73,74 core-hole locations_ . 4 deltaic deposits__ 9 deposition of sediments_______ _______ 6,17,21 exchangeable cations on clays_____ .. 28,73,74 flood-plain deposits__________ .. 9,17 lacustrine deposits... __________________ 9 particle sizes________________ _ 9,13,51,58,59 principal types of deposits. ..... 5 sediments_________________________ ... 3 sources of sediments____ _________ . 5 Los Gatos Creek (Fresno County, No. 12), clay minerals______________ ____20,74 exchangeable cations___________________ 25,74 Los Gatos Creek (Santa Clara County, No. 4), clay minerals____ .. ___ _ 45,77 Lymnaea______________________________________ 40 M McClelland, E. J., cited_____ 38 Manzanares, Toribio, Jr., analyst ...... 76,77 Marine deposits__________________________ .21,34 distinguishing criteria_ . 28 particle sizes__________ _____________30,31 relations between median diameter and other particle-size measures_______ S3 Martinez Creek (No. 11), clay minerals_______20,74 Mayfield Slough, exchangeable cations__________ 77 Mayfield Slough (No. 11), clay minerals______45,77 Mendotacore______________ 5,9,12,21,22,51,58,73 clay minerals_______ _________ _________19,73 core-hole location__ 4 exchangeable cations__________ _______ 25,73 particle-size distribution__________ 12,51,58 Menetus______________________________________ 40 Metamorphic rocks____________________________18,24 Miller, R. E., cited__________________________ 9 Page Mineral species, estimation of relative proportions............................... C 71 Montmorillonite...... 5,18,20,22,34,41,43,46,48,67 sources_____•_........................... 18 alteration of volcanic material_________ 18 Montmorillonite-illitc, mixed-layer______ 18,22,68 Moreno Gulch (Nos. 2, 3), clay minerals_____20,74 Mudflow deposits_______________________________ 16 N Naugler, F. P., analyst________________________ 78 Nelson, B. W., cited_________________________ 22 O OroLomacore______________ ... 5,9,18,22,23,58,73 clay minerals_________________________ 18,19,73 core-hole location_________________________ 4 exchangeable cations______________________25,73 particle sizes_____________________________ 58 Oxyhornblende__________________________________ 38 P Panoche Creek, cation composition of water samples_________________________ 23,58 exchangeable cations____________________ 23,25,74 Panoche Creek (Nos. 5, 6), clay minerals____20,74 Particle-size distribution, CM diagrams. 14,16,33,43 descriptive measures...................... 49 interrelations of particle-size measures.. 16,82,48 measures of central tendency............. 11 median diameters........................ 11, 13,14,16,29,81,32,33,4*. 43, 49 modal diameters................ 11,29,81,42 relations to depositional history of sediments.................................... 13 skewness__________ 11,14,16,29,81,33,42,43,49,50 sorting___________ 11,14,16,29,81,33,42,43,49 Particle sizes, analytical procedures.......... 48 Los Banos-Kettleman City area_________ 9,51,58 sampling________________________________ 3,48 Santa Clara Valley_____________________ 41,68 spatial distribution in cores________ 12,81,42 tables of data............................ 50 Tulare-Wasco area______ ________________ 27,60 Passega, Renato, cited___________________ 14,15,49 Permeability, relation to grain size___________ 13 Petrologic study, summary of results----------- 46 Pettijohn, F. J., cited.................... 11,50 pH, effect on cation exchange of clays......23,36 measurement............................... 72 pH environment of the San Joaquin Valley sediments__________________________ 21 Phi, defined___________________________________ 49 Pisidium____________________________________ - 40 Pixley area.................................. 36 Pixley core________________ 22,24,27,29,82,34,60,75 chemical composition of nearby ground water______________________________ 36 clay minerals___________________________84,75 core-hole location_________________________ 26 exchangeable cations____________________85,75 particle sizes__________________________82,60 Pliocene sandstones_____________________________ 5 Poland, J. F., cited_____________________ 23,24,38 Pollard, W. C., analyst______________________ 77 Porosity___________________________________ 8,47 Potassium-argon dating of volcanic ash______ 9 Pratt, P. F., cited__________________________ 36 Purposes of report____________________________ 2 Pyrite_________________________________ 7,23,28,38 R Resistivity logs______ _________ 12,13,26,29,32,43 Review of previous work of sedimentologists.. 14 Richgrove area_________________________ ... 36 Page Richgrove core............. C24,27,29,32,33,35,38,61 chemical composition of nearby ground waters.......................... 36 clay minerals___________________________84,75 core-hole location...................... 26 exchangeable cations..................... 85,75 particle sizes......................... 81,82,61 soluble salts and anions____________________ 87 Roy, Rustum, cited____________________________ 22 Rubin, Meyer, cited________________________ 41 S Salt Creek (No. 10), clay minerals________20,74 Salts, San Jose core_______________________ 40 Sunnyvale core___________________________ 40 San Emigdio Mountains_________________________ 46 San Francisco area........................... 18 San Francisco Bay, clay minerals___________41,45,77 San Francisquito Creek, exchangeable cations. 77 San Francisquito Creek (Nos. 1, 2), clay minerals______________________45,77 San Joaquin Formation_______ 3,5 San Joaquin River basin_________... ________ 21 San Joaquin Valley........................ 3,5,8,18 pH environment of sediments____________ 21 San Jose area, deposition rate_____________ 41 San Jose core--------------------------- 40,65,76 chemical composition of nearby ground water.............................. 78 clay minerals_______________________ ___44,76 core-hole location......................... 39 date of, by carbon-14 analysis_________ 41 exchangeable cations..................... 40.76 particle sizes........................ 4$, 65 Sands, andesitic................................ 5 arkosic................................... 5 Arvin-Maricopa area_________________________ 46 Diablo Range_______________________________ 5 Richgrove core____________________________ 24 San Jose core..___________________________ 38 Sunnyvale core______________ _______ . 38 Santa Clara County----------------------------- 38 Santa Clara Valley______________ 2,24,39,41,68,77 age of sediments.................... 88,40,4/ chemical composition of ground waters. 44.77,78 clay-mineral assemblage................... 48 core-hole "locations---------------------- 39 exchangeable cations on clays__________ 44 particle sizes------:------------------- 41 rates of deposition----- ...------------ 41 sediments______________________________ 88 soils.................................... 39 source of sediments_____ 88 types of deposits------------------------- 88 Santa Cruz Range____________________________ 38 Santa Margarita Formation.. _ _ 24,31 Sedimentary rocks_____________________________ 18 Serpentine_________________________ 5,22,24,38,46 Shepard, F. P., cited--------------------------- 9 Sierra Nevada___________ - 3,5,9,11,17,21,24 Sigvaldason, G. E., cited... ------ ...... 22 Skewness, Bowley’s measure of. _______________ 50 Soil textures_________________________________ 27 Soils, modern alluvial.. 39 older alluvial______ ... .. ----- - 40 Sokula, Ignacio, analyst....................... 77 Sources of clay minerals---- . . . 18,22,84,44,46 Sources of sediments---------------------- 5,24,88 Starkey, II. C., analyst---- --- 73,74,75,76,77 Stevens Creek (No. 3), clay minerals-------- 45,77 Stream sediments, exchangeable cations------ 28 Sulfate.------------------------------------- 23 in marine siltstones___________________ 87 origin............................... 38 Sulfides, authigenic__________________ 7,9,28,37,38 Summary of results-------------------------- 46INDEX C83 Page Sunnyvale core______________________ C40,41,63,76 chemical composition of nearby ground waters_____________________________ 77 clay minerals____________________________44,76 core-hole location_________________________ 39 date of, from fossil remains--------------- 41 exchangeable cations_____________________46,76 particle sizes--------------------------43,63 T Taylor, D. W., fossils identified by___________ 40 Trask, P. D., cited____________________________ 50 Tulare County, core holes______________________ 24 Tulare Formation____________________________3,5,21 andesitic sands_____________________________ 5 Coicoran Clay Member, lacustrine deposits. 8,12,27 waterlaid deposits______________________ 5 Page Tulare-Wasco area__________________ C 2,22, S3,35,60 age of sediments____________________________ 24 alluvial-fan deposits__________________21,27,33 chemical composition of ground waters____36,38 clay-mineral assemblages__________________34,75 core-hole locations_________________________ 26 exchangeable cations on clays............. 35,75 lacustrine and flood-plain deposits____________ 27 marine deposits________________________21,24,33 nonmarine sediments, description____________ 29 particle sizes____________________________27,60 principal types of deposits_______________24,27 sediments___________________________________ 24 source of deposits________________________24,27 Turner, F. J., cited_____________________________ 5 V Page Vermiculite____________________________ C21,3i,67 Villarruz, Primo, analyst_____________________ 78 Volcanic ash, potassium-argon dating of__________ 9 Volcanic glass________________________________ 24 Volcanic material________________________5,18,24 Volcanic rocks________________________________ 18 W Waugh, A. E., cited___________________________ 50 White, D. E., cited______________________ 22,38 Wiklander, Lambert, cited_____________________ 36 Williams, Howel, cited_________________________ 5 X X-ray diffraction, procedure__________________ 66 U. S. GOVERNMENT PRINTING OFFICE : 1967 O - 232-511I^ IT] 7 DAY IS' ispLACompaction of Sediments Underlying Areas of Land Subsidence in Central California GEOLOGICAL SURVEY PROFESSIONAL PAPER 497-DCompaction of Sediments Underlying Areas of Land Subsidence in Central California By ROBERT H. MEADE MECHANICS OF AQUIFER SYSTEMS GEOLOGICAL SURVEY PROFESSIONAL PAPER 497-D A study, partly statistical, of the factors that influence the pore volume and fabric of water-bearing sediments compacted by effective overburden loads ranging from J to go kilograms per square centimeter UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1968UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price 35 cents (paper cover)CONTENTS Page Abstract________________________________________________ D1 Introduction_______________________________________________ 1 Purpose of report_____________________________________ 2 Acknowledgments_______________________________________ 2 Review of factors influencing compaction of clays and sands____________________________________________________ 3 Removal of water from clays____________________... 3 Rearrangement of clay-mineral particles_______________ 5 Development of preferred orientation______________ 6 Development of turbostratic orientation___________ 8 Reduction of pore volume in sands at pressures less than 100 kilograms per square centimeter____________ 9 Influence of particle size_______________________ 9 Influence of particle sorting.................... 11 Influence of particle roundness__________________ 12 Influence of mica particles______________________ 12 Influence of interstitial water__________________ 12 Pore volume of sandstones at pressures greater than 100 kilograms per square centimeter________________ 12 Summary of petrology of sediments in areas of land subsidence______________________________________________ 14 Analysis of factors influencing compaction of the sediments___________________________________________________ 17 Use of multiple-regression statistics for analysis_ 17 Effect of overburden load____________________________ 18 Effect of particle size______________________________ 22 Page Combined effects of overburden load and particle size________________________________________________ D23 Effect of particle sorting_____________________________ 24 Combined effects of selected physical and chemical factors_____________________________________________ 25 Fabric of the sediments and its relation to overburden load and other factors____________________________________ 28 Orientation of clay-mineral particles__________________ 28 Observation and measurement________________________ 28 Relation to depth of burial and type of sedimentary deposit____________________________________ 29 Relation to particle size and chemical factors— 31 Domainlike aggregates_____________________________ 31 Distribution of montmorillonite orientation within the sediments_____________________________ 32 Fabric of sands_______________________________________ 32 Preparation of thin sections_______________________ 32 Distortion of compressible grains__________________ 32 Orientation of mica particles_____________________ 34 Conclusions_________________________________________________ 34 Glossary of statistical terms_______________________________ 36 References_________________________________________________ 37 Appendix A. Samples used in statistical studies_____________ 39 Appendix B. Effective overburden loads at different depths in the cored sections at time of coring_________ 39 ILLUSTRATIONS Page Figure 1. Graphs showing influence of different factors on the relations between void ratio and pressure in clayey materials______________________________________________________________________________________________ D4 2. Graph showing influence of pH on relations between void ratio and pressure in <4-micron fractions of kao- linite mixed with 10~3 M sodium chloride solution______________________________________________________ 5 3. Sketches showing idealized clay-mineral particle arrangements that may be formed during compaction________ 6 4-8. Graphs showing: 4. Influence of particle size on void ratio of silts, sands, and sandstones___________________________ 11 5. Influence of particle sorting on void ratio of sands_______________________________________________ 11 6. Influence of degree of roundness of pure quartz, 420 to 840 microns in size, on relation between void ratio and pressure_________________________________________________________________________________ 12 7. Influence of proportion and size of mica particles on relations between void ratio and pressure in sands and silts__________________________________________________________________________________________ 13 8. Influence of interstitial water on relation between void ratio and pressure in well-sorted clean quartz sands_____________________________________________________________________________________________ 14 9. Map showing locations of core holes in central California_____________________________________________________ 15 10. Composite logs of petrologic characteristics of sediments cored in areas of land subsidence in central California_________________________________________________________________________________________________ 16 11. Graphs and diagrams showing simple relations between void ratio and effective overburden load in fresh- water-bearing alluvial sediments___________________________________________________________________________ 20 mIV CONTENTS Figures 12-17. Graphs showing: Page 12. Relations between median diameter and the residuals of the void ratio-load regressions______ D22 13. Simple relations between void ratio and median particle diameter in fresh-water-bearing alluvial sediments_______________________________________________________________________________ 23 14. Influence of particle size on relations between void ratio and effective overburden load____ 23 15. Relations between quartile deviation and the residuals of void ratio-load-Md^ and void ratio- Mdj, regressions___________________________________________________________________________ 25 16. Simple relation between void ratio and quartile deviation in silty sands from Los Banos-Kettleman City area___________________________________________________________________________________ 25 17. Relations of void ratio of fine sediments in Richgrove core to depth of burial, type of sedimentary deposit, and effective overburden load_______________________________________________;__ 26 18-20. Diagrams showing: 18. Relations of montmorillonite-particle orientation to depth of burial and type of deposit represented by fine sediments cored in Los Banos-Kettleman City area________________________________ 30 19. Relations of montmorillonite-particle orientation to depth of burial and type of deposit represented by fine sediments in Richgrove core_________________________________________________________ 31 20. Orientation of montmorillonite in sections cut at different angles to the bedding of sediments from Huron and Richgrove cores__________________________________________________________________ 33 21. Sketches showing distortion of compressible sand grains_____________________________________________ 34 22. Sketches showing sections of micaceous sands from Mendota core______________________________________ 35 TABLES Page Table 1. Summary of experimental data on compaction of unconsolidated sands------------------------------------------- DIO 2. Details of significant regressions of void ratio on effective overburden load, median particle diameter, and quartile deviation of particle-size distribution_______________________________________________________ 21 3. Selected properties of fine sediments in Richgrove core___________________________________________________ 27 4. Selected details of multiple regressions of void ratio on different combinations of variables, representing properties of selected fine sediments in Richgrove core________________________________________________ 27 5. Selected details of multiple regressions of orientation ratio on different combinations of variables representing properties of marine siltstone in Richgrove core_______________________________________________________ 31MECHANICS OF AQUIFER SYSTEMS COMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA By Robert H. Meade ABSTRACT An increase in effective overburden load from 3 to 70 kilograms per square centimeter, partly natural and partly manmade, has caused an average reduction of 10 to 15 percent in the volume of alluvial sediments in the San Joaquin and Santa Clara Valleys of California. The effects of load, however, are complicated by the effects of other factors on the pore volume. The most easily discerned of these factors in the alluvial sediments are particle size and particle sorting. The variation in pore volume that is related to differences in average particle size is of the same order as the variation related to differences in load. The effects of particle sorting are probably subsidiary to the effects of load and average particle size. A multiple-regression analysis of the pore volume, overburden load, and selected petrologic characteristics of a group of 20 fine alluvial and shallow-marine sediments from the east side of the San Joaquin Valley shows the pore volume to be most closely related to particle size, diatom content, and the proportion of sodium (relative to other exchangeable cations) adsorbed by the clay minerals. Other factors that may have direct or indirect influence on the pore volume are the large proportions of mont-morillonite in the sediments, and the variable pH and concentration of the interstitial electrolytes. The effects of overburden load on the pore volume of this group of sediments is completely obscured by the influence of the petrologic factors. The degree of preferred orientation of the montmorillonite particles in the fine sediments in the San Joaquin Valley shows no regular relation to the depth of burial. The degree of orientation is related most consistently to the types of deposits represented by the sediments and decreases in the order: lacustrine, shallow marine, flood plain, and alluvial fan. The identity of the specific sediment properties or environmental characteristics that control the orientation, however, is uncertain. The only effects of compaction observed in the sands are distorted and broken fragments of mica, shale, and metamorphic rock. INTRODUCTION The compaction of clastic sediments is influenced by several factors in addition to the load exerted by over-lying sediments. During the early stages of compaction, these factors include such textural properties as particle size and sorting, such compositional characteristics as the proportions of mica or the different clay minerals, and such chemical properties as the composition and concentration of the material dissolved in the interstitial waters. Our understanding of the process of compaction, therefore, involves understanding how these factors interact with each other and with increasing overburden loads to inhibit or to enhance the removal of fluids and the reduction of pore volume in sediments. The compaction of the water-bearing sediments in three areas of land-surface subsidence in the San Joaquin and Santa Clara Valleys of California is the subject of this report. The historic compaction and land subsidence in these areas are clearly related to the depletion of artesian pressure (increase of grain-to-grain load) in the sediments, which is a result of confined ground water being pumped from the sediments faster than it is being replenished. Because the rates of compaction and subsidence are rapid and can be measured, these areas were selected as field laboratories for a program of study of the mechanics of aquifer systems. Because the compaction represents an acceleration of the natural processes that would have taken place with the further accumulation of overlying sediments, these are also opportune areas for general studies of the compaction of sediments. Two factors complicate these studies of compaction which are based on void ratios (pore volumes) determined in the laboratory from core samples obtained between 1957 and 1960. First, the void ratios reflect the combined effect of (1) the natural compaction due to the slow long-term increase in effective stress (effective overburden load) accompanying gradual burial and (2) the manmade compaction due to the rapid shortterm increase in effective stress resulting from decline in artesian head. At the time the cores were taken, the increment of void ratio resulting from the natural compaction was in equilibrium with the effective overburden load because time, an essential ingredient, had been adequate. The deeper cores, 1,000 to 2,000 feet beneath the D1D2 MECHANICS OF AQUIFER SYSTEMS land surface, have been compacting under increasing sediment burial for one to possibly 5 million years. On the other hand, the application of the additional manmade stress began only 30 to 50 years ago and this stress had increased irregularly but rapidly to the coring date. The thicker fine-grained beds of low permeability were still experiencing pore-pressure decay and had not had time to attain hydraulic equilibrium with the head decline in the beds of coarser texture and higher permeability—the aquifers. Hence, in the fine-grained beds, the void ratio increment had not reached equilibrium because of man’s change of the hydrologic regimen. Second, data are not available for differentiating the increments of void ratio due to the natural and manmade increases in effective stress partly because, at the time of coring, the manmade increment was transient. The reader should keep this in mind, especially in the chapter on analysis of factors influencing compaction of the sediments. At the time the samples were cored, the ratio of manmade to natural stresses varied with depth and hydro-logic regimen and ranged from 0 to about 22 percent. For example, in the Santa Clara Valley at San Jose, the natural effective overburden load in 1960 (time of coring) at a depth of 500 feet was about 16 kg per cm2 (kilograms per square centimeter) or 230 psi (pounds per square inch), and the manmade increase was about 3.5 kg per cm2 based on 120 feet of artesian-head decline. Thus, the manmade increase in effective stress at the 500-foot depth in San Jose as of 1960 was 22 percent. On the other hand, in the San Joaquin Valley at Cantua Creek, the natural effective stress in 1958 at a depth of 300 feet was 13 kg per cm2 (185 psi) and the manmade increase was zero (based on a constant water table); at a depth of 2,000 feet, however, the natural effective stress was about 65 kg per cm2 (930 psi), and the manmade increase was about 13 kg per cm2 based on 400 feet of artesian-head decline. Thus the manmade increase in effective stress at the 2,000-foot depth at Cantua Creek as of 1958 was 20 percent. A discussion of the problems of land subsidence and aquifer compaction and the ways in which the problems have been approached are given by J. F. Poland in his foreword to the first chapter of this series (Johnson and others, 1967). PURPOSE OP REPORT This report is one of a series of chapters of Geological Survey Professional Paper 497, on the mechanics of aquifer systems in California and elsewhere. It is also the last of three chapters by the same author that concern the petrologic aspects of compaction. The first of these three chapters (Meade, 1964) is a comprehensive review of previous work on the factors that influence pore volume and fabric of clayey sediments under increasing overburden loads. The second of the chapters (Meade, 1967) is a description of the variation and distribution, in the sediments of central California, of some of the petrologic factors that the review of previous work showed to be significant influences on compaction. The third chapter—this report— relates, partly by statistical analysis, the variations in overburden load and petrologic factors to variations in the pore volume and fabric of the sediments. Although these reports are part of a comprehensive series, their organization and content are such that they can be read separately. The first section of this report is a review of previous work that identifies and evaluates factors that influence the responses of clastic sediments to loads between 0 and 100 kg per cm2 or 1,422 psi (15 psi«=*l atmospheres 1 ton per sq ftsl kg per cm2). This section consists of (1) a brief summary of the first chapter (Meade, 1964) plus a discussion of new evidence, mostly on the development of preferred orientation in clays, that has become available since the earlier chapter was completed, and (2) a review of the factors that influence the compaction of sands. Then follows a brief summary of the second chapter (Meade, 1967), describing the distributions of relevant petrologic factors in the sediments of the San Joaquin and Santa Clara Valleys in enough detail to set the stage for what follows. The final sections are detailed studies, largely statistical, that explore the following questions: (1) What factors influence the water content and fabric of these sediments under effective overburden loads between 3 and 70 kg per cm2? (2) What is the relative importance of these factors? Some preliminary results of these studies have been published in three earlier papers (Meade, 1961b, 1963a, 1963b), which are now superseded by the present report. ACKNOWLEDGMENTS I would like to thank the following people, all of whom are members or former members of the Geological Survey: J. B. Corliss, for assistance in measuring the fabric of the clayey sediments; D. R. Dawdy, for instructive discussions in the uses and misuses of statistics; H. C. Starkey, Claude Huffman, and A. J. Bartell, for determining selected chemical characteristics of the clayey sediments; and P. H. Held and Ruperto Laniz, for careful attention to the difficulties of making thin sections of unconsolidated clays and sands. I also appreciate the critical discussions and reviews of the manuscript by my supervisor, J. F. Poland, and my colleagues, W. B. Bull, D. R. Dawdy, A. I. Johnson, B. E. Lofgren, L. K. Lustig, and R. P. Moston.COMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D3 REVIEW OF FACTORS INFLUENCING COMPACTION OF CLAYS AND SANDS Because the pore volume of clastic sediments decreases with increasing overburden loads, it is a useful and convenient measure of compaction. In water-saturated sediments, it is also a measure of water content. Factors other than overburden load, however, influence the pore volume and water content of sediments and must be considered in any comprehensive study of compaction. This section of the report summarizes the pertinent previous studies that identify these factors and indicate the nature and degree of their influence on compaction processes. This review is restricted largely to compaction in the range of pressures between 0 and 100 kg per cm2, which includes the range that applies to the waterbearing sediments whose compaction accounts for the observed land subsidence in central California. It is further restricted mainly to consolidation processes that involve direct responses to load and mostly ignores the reduction of pore volume by the formation of interstitial cement. The measure of pore volume used most extensively in this report is the void ratio, which is defined as the ratio of the volume of pore space to the volume of solids. Percent porosity is also included in most of the figures and in some of the text discussions. REMOVAL OF WATER FROM CLAYS Because of the intimacy of the relations between water and clay, the reduction of pore volume in clays under increasing overburden loads is best considered in terms of the removal of water. The factors that are known to influence the water content of clayey sediments under applied loads are particle size, clay minerals, adsorbed cations, interstitial electrolyte solutions, acidity, and temperature. The effects of all but the last two of these factors are shown in figure 1. With the exception of particle size, the influence of these factors is inferred mainly from laboratory studies of monomineralic clays mixed with simple electrolytes. Very little of the present knowledge is based on the study of sediments in nature or on laboratory mixtures of clays and electrolytes that approach the complexity found in nature. This section of the review is mainly a summary of material that was treated earlier in much greater detail (Meade, 1964, p. B2-B13). Some newer evidence on the influence of acidity and temperature, taken from the work of Warner (1964), is included here to bring the earlier paper up to date (1965). Void ratio is used as a volumetric measure of water content. The influence of particle size on the pore volume and water content of fine sediments is represented in figures 1A and IB. The five lines in figure 1A represent groups of sediments from different areas— river reservoirs, an estuary, and the deep sea. None of these sediments were buried more than 20 feet below the water-sediment interface. Figure IB is a summary of the effects of particle size on the water content of sediments under pressure that was prepared by Skempton (1953, p. 55) from studies of sediments in the United States and Great Britain. The two graphs show the inverse relations between particle size and pore volume and how these relations persist during compaction under pressures approaching 100 kg per cm2. The influence of different clay minerals on water content is discernible over a wide range of pressures, as shown in figure 1C. The observed differences are related to differences in the surface areas per unit weight (specific surfaces) of the clay minerals. The larger the specific surface, the larger the amount of water retained by the clay under pressure. Mont-morillonites have larger specific surfaces than illites, which in turn have larger specific surfaces than kaolinites. The influence of different exchangeable cations on the water content of montmorillonite is shown in figure ID. Sodium-saturated montmorillonites retain more water than montmorillonites whose exchange positions are saturated with other common cations. These effects, however, have only been observed at pressures less than 50 kg per cm2; at greater pressures, differences in the exchangeable cations do not seem to be related to differences in water content. Because of the larger specific surface of montmorillonite and its associated larger capacity for adsorbing cations, the effects of different exchangeable cations on water content are much more pronounced in montmorillonite than in the other clay minerals. But in addition to showing effects of a lesser degree, other clay minerals may be affected in different ways by the exchangeable cations. An experiment by Samuels (1950; see Meade, 1964, fig. 12) on kaolinite saturated with different cations showed the largest water content in kaolinite saturated with aluminum and the smallest in kaolinite saturated with sodium— an effect opposite to the one shown in figure ID. The relative differences in water content, however, were substantially less than those shown in figure ID. The graphs in figures IE and IF show two opposite effects of electrolyte concentration on the water content of clays under pressure. The relation shown in figureVOID RATIO VOID RATIO VOID RATIO D4 MECHANICS OF AQUIFER SYSTEMS 0 10 o cd O > z >-■ H cn O q: o CL LLl O cr LlI Q- o > (/) o o CL EFFECTIVE OVERBURDEN PRESSURE, IN KILOGRAMS PER SQUARE CENTIMETER z LlI O Cd LlI Q. LlI D _J O > z £ (/) o Cd o Q. I- z LlI o a: LlI Q. LlJ 2 D _J O > z o Cd o CL PRESSURE, IN KILOGRAMS PER SQUARE CENTIMETER PRESSURE, IN KILOGRAMS PER SQUARE CENTIMETER Figure 1.—Influence of different factors on the relations between void ratio and pressure in clayey materials (summarized from Meade, 1964, p. B5—B12). Note different void-ratio and pressure scales. A, Relation of void ratio to median particle diameter at overburden pressures less than 1 kg per cm2 (Meade, 1964, p. B6). B, Generalized influence of particle size (modified from Skempton, 1953, p. 55)’. C, Influence of clay-mineral species (modified from Chilingar and Knight, 1960, p. 104). D, Influence of cations adsorbed by montmorillonite (modified from Samuels, 1950), E, Influence of sodium chloride concentrations in unfractionated illite—about 60 percent coarser than 2 microns (modified from Mitchell, 1960, fig. M-3). F, Influence of sodium chloride concentration in illite finer than 0.2 micron (modified from Bolt, 1956, p. 92>).COMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D5 IE—greater water contents associated with more concentrated electrolyte—seems to be characteristic of most clay-water-electrolyte systems. The effect is related to the tendency of the clays to flocculate more readily in more concentrated electrolyte and to form openwork aggregate structures that resist compaction. The opposite relation shown in figure IF is characteristic of a restricted clay-water-electrolyte system, namely fine clays (montmorillonite or fine illite) associated with sodium electrolytes in concentrations less than about 0.3 M (molar solution). In this system, the effect of the electrolyte concentration may be its control (as predicted by double-layer theory) of the tendency of the adsorbed sodium to diffuse and its consequent control of the thickness of the layer of adsorbed water that surrounds each particle. The different electrolyte concentrations do not seem to affect the water content of clays at pressures greater than 50 kg per cm2. They do, however, seem to affect the fabric of clays at greater pressures, as discussed in the next section. Recent experiments by Warner (1964, p. 51-62) describe some of the effects of acidity on the water content of clays. In figure 2, showing some results of Warner’s pressure experiments on kaolinite (<4 microns) mixed with 10-3 M sodium chloride at different pH values, the greater void ratios are associated with the lower pH. This effect is related to the tendency of kaolinite and illite flakes to form more open flocculated structures in acid than in alkaline solutions—as shown by the studies reviewed earlier (Meade, 1964, p. B15), and supported by Warner’s (1964, p. 38-46) own sedimentation experiments. Warner found, however, that kaolinite mixed with a more concentrated electrolyte (0.55 M sodium chloride) showed void ratio-pressure relations that did LlI o cc LU CL- UJ 5 D -I o > (/) O QC O a. PRESSURE, IN KILOGRAMS PER SQUARE CENTIMETER Figure 2.—Influence of pH on relations between void ratio and pressure in <4-micron fractions of kaolinite mixed with 10-3 M sodium chloride solution. Modified from Warner, 1964, p. 52. not vary with changes in pH (in the range 2.0 to 8.5). Furthermore, he found no variations in the void ratio-pressure relations in illite or montmorillonite (mixed with different concentrations of sodium chloride solution) that could be related to variations in pH. The sum of his results seems to indicate that (1) the degree of acidity influences the water content of kaolinite under pressure and in contact with dilute electrolyte solutions and (2) that it has no influence on the pressure response of kaolinite mixed with more concentrated electrolyte, of illite, or of montmorillonite. The influence of temperature on the water content of clayey sediments under pressure is not well defined. It is well known, however, that temperatures between 100° and 150° Celsius (centigrade) will remove the interstitial water from most clays under otherwise atmospheric conditions. One would expect the natural increase in temperature that accompanies increasing depth of burial to enhance the tendency of the increasing overburden load to remove water from clays. Little evidence is available, however, to support this expectation. At low pressures, furthermore, the temperature may have little effect. Warner’s experiments (1964, p. 51-55, 59-62, 70-75) showed that variations in temperature in the range between 25° and 80°C caused no differences in the equilibrium water content of kaolinite or montmorillonite at pressures between 1 and 8 kg per cm2. The rates of compaction under these pressures, however, did increase with increasing temperature. The experimental studies of van Olphen (1963, p. 183-186; reviewed by Meade, 1964, p. B13), suggest that increasing temperatures may assist in the removal of water at pressures greater than several hundred kilograms per square centimeter. The influence of temperature on the compaction of clays is a promising subject for future study—especially enlightening would be experiments in which pressure and temperature were increased simultaneously by appropriate increments that corresponded to geostatic and geothermal gradients. REARRANGEMENT OF CLAY-MINERAL PARTICLES As a corollary to the reduction of pore volume under increasing loads, clay particles must move closer together in space and into more efficient packing arrangements. Many different arrangements are possible. The most widely considered arrangement, taking the characteristically platy shape of clay-mineral particles into account, is a preferred orientation such as is represented in figure 3A. This arrangement has been assumed to be the most likely result of the compression of clays—often to the exclusion of other possibilities. Another arrangement which some evidence suggests might be formed during compaction is shown in figure 3B, and consists 280-804 O—<57---2D6 MECHANICS OF AQUIFER SYSTEMS of packets or domains of clay particles within which the planar orientation is perfect and between which the orientation is random. This fabric has been called turbo-stratic by Aylmore and Quirk (1960, p. 1046). Other regular fabrics as yet undescribed may be formed during compaction. Some clays may be compacted without developing any regular arrangement of particles. DEVELOPMENT OP PREFERRED ORIENTATION Because preferred orientation has received most of the attention in studies of the changes in clay fabric under increasing loads, many of the factors that influence its development have been identified. In the studies published through 1962, as reviewed earlier (Meade, 1964), much of the evidence on which the identification was based was indirect and included few actual measurements of the degree of orientation. In the years 1963 through 1965, several new studies have been completed that provide more direct evidence in the form of X-ray-diffraction measurements of clay fabric. Mainly on the basis of the newer studies, we may make a systematic assessment of the nature and degree of the influence of the following factors on the relations between pressure and preferred orientation in clayey sediments: initial water content, particle size, clay minerals, exchangeable cations, electrolyte concentration, acidity, and organic matter. Figure 3.—Idealized arrangements of clay-mineral particles that may be formed during compaction. A, Preferred orientation. B, Turbostratic orientation. Experiments by Martin (1965) on kaolinite slurries and by O’Brien (1963, p. 20-40) on illite and kaolinite pastes indicate that, given sufficient initial water content, most of the reorientation of clay particles that occurs at pressures less than about 100 kg per cm2 takes place during the very early stages of compaction. Martin stated that a pressure of 1 kg per cm2 produced “a very marked preferred orientation which does not change upon further consolidation up to 32 kg/cm2.” O’Brien’s experimental results tabulated in the next paragraph also show well-developed preferred orientation at low pressures—0.02 to 0.2 kg per cm2. The influence of the initial water content on the development of preferred orientation is shown in the following results obtained by O’Brien (1963, p. 36-37; 1964, p. 827-828) during pressure experiments on pastes of kaolinite and illite mixed with a prepared “marine” water (27 grams sodium chloride plus 1 gram calcium chloride per liter). Initial water content Pressure Orientation value (percent of wet weight) (kg per cm2) Kaolinite (unfractionated) Not specified Uncompressed 1.2 48 2.4 32 48 7.6 Illite «2 microns* Not specified Uncompressed 1.5 44 0.08 1.5 Ulite-kaolinite (<2 microns) Not specified Uncompressed 3.0 50 0.17 20.0 55 . 08 38.0 67 .02 28.0 The orientation value here is similar to the orientation ratio described on page D29: values near 1.0 denote random orientation, higher values denote greater degrees of preferred orientation. These data show fairly clearly that the initial water content is a critical factor in determining the degree of preferred orientation that develops during the early stages of compaction. A certain amount of interstitial water is required to allow the particles to move easily past one another into positions of preferred orientation. The studies cited in this and the previous paragraphs substantiate Hedberg’s (1936, p. 272,281) inference that most of the mechanical rearrangement of particles during compaction takes place while porosities of the sediment are on the order of 75 to 90 percent and perhaps within 5 to 10 centimeters of the surface of deposition.COMPACTION ,OP SEDIMENT'S UNDERLYING AREAS OF LAN® SUBSIDENCE IN CENTRAL CALIFORNIA D7 The relation of particle size to the preferred orientation of clays is not clear. Grim, Bradley, and White (1957) in studying Paleozoic shales in Illinois suggested that preferred orientation was better formed in finegrained shales (in which most of the particles were finer than 2 microns) than in coarser grained shales that contained appreciable amounts of nonclay mineral grains. A similar observation was reported by Folk (1962, p. 541) in Silurian black shales in West Virginia: the most extreme examples of preferred orientation of clay-mineral particles were seen in shales having the least calcite and the least silt. On the other hand, Beall (1964, p. 79) said that he could find no relation between the degree of orientation and the grain size of the Cretaceous mudstones that ho studied in Texas. No experimental evidence is available to shed light on these studies of natural claystones. They may only indicate that some fine-grained sedimentary rocks have well-developed preferred orientation and some have not. Studies reviewed earlier (Meade, 1964, p. B17-B19), supported by the experiments of Martin and O’Brien cited above, give the impression that low pressures on the order of a few kilograms per square centimeter can produce marked preferred orientation in kaolinite and illite but do not seem to produce much orientation in montmoril Ionite. Greater pressures on the order of 100 kg per cm2 or more, as applied in laboratory studies, can produce preferred orientation in any clay minerals of platy habit—including montmorillonite. At lower pressures, however, the larger clay particles of illite and kaolinite seem to be more susceptible to preferred orientation than the smaller particles typical of montmorillonite. This impression is substantiated by Beall’s (1964, p. 42) studies of the fabric of Cretaceous mudstones of Texas in which kaolinite and illite always showed a greater degree of preferred orientation than montmorillonite, within the same rocks. Odom (1963, 1964), on the other hand, noted a lack of correlation between the variable clay-mineral composition and the preferred orientation of different Paleozoic argillaceous rocks in Illinois. The only previous direct evidence of the influences of the different exchangeable cations on fabric was presented by Beall (1964, p. 82-84). He noted that the degree of preferred orientation of the clay minerals was inversely related to the amount of exchangeable sodium, relative to exchangeable calcium and magnesium, in seven samples of the Cretaceous mudstones that he studied. However, the opposite relation—a direct relation between the degree of montmorillonite orientation and the proportion of adsorbed sodium—was found in 11 samples of shallow-marine sediment in the San Joaquin Valley (described later in this report). The influence of electrolyte concentration on the fabric of clays under pressure is indicated by the results of experiments made by Engelhardt and Gaida (1963, p. 926-927), and by Warner (1964, p. 84-91). In montmorillonite compacted under a pressure of 800 kg per cm2, Engelhardt and Gaida found an increase in the degree of preferred orientation with decreasing concentrations of sodium chloride solutions in the range 1.1 to 0.16 M. A similar increase in orientation with decreasing sodium chloride concentration (range 2.4 to 0 M) was shown in experiments with kaolinite compacted under a pressure of 160 kg per cm2, although these results were not as clearly expressed as the results of the experiments with montmorillonite. From experiments with kaolinite sedimented at a pH of 8.5 in sodium chloride solutions of two concentrations (0.55 and 0.001 M) and compacted under a pressure of 4,200 kg per cm2, Warner reported that the better developed preferred orientation was associated with the lower electrolyte concentration. These results, however, pertain to pressures greater than 100 kg per cm2. No clearly expressed relations between electrolyte concentration and preferred orientation resulted from the experiments conducted at low overburden pressures by O’Brien (1963, p. 21-28). He suspended two different concentrations of kaolinite in three different electrolyte solutions and allowed the clay to settle out. Then, over a period of 3 weeks, he sedimented 3 feet of silt and sand on top of the clay. The volume of the clay was reduced by about half during the 3-week period. The degrees of orientation produced are illustrated in the following table. The number in the last column is the final orientation value after the overburden load was applied. Electrolytes Kaolinite Final (grams per liter) in original orien- Solution ---------------------- suspension tation NaCl CaCh (grams per value liter) “Salt lake” water__________ 85 0. 55 5 48 Do_________________ 85 .55 50 11,2 “Marine” water_____________ 27 1 5 64 Do____________________ 27 1 50 10 “Fresh” water______________ 0. 05 0. 1 5 4. 5 Do_________________ .05 .1 50 34 Whereas the data do not show a simple relation between electrolyte concentration and fabric, they may indicate a complex, and as yet undefined, interrelation between fabric, concentration of clay suspensions, and concentration of electrolytes. The effects of variations in acidity on the orientation of clay particles under pressure can only be inferred indirectly from Warner’s (1964, p. 51-62) experiments that were discussed earlier (fig. 2). In kaolinite mixedD8 MECHANICS OF AQUIFER SYSTEM'S with electrolyte solutions of low concentration, the degree of preferred orientation may be better developed in alkaline than in acid solutions. On the other hand, acidity may have little or no effect on the orientation of kaolinite associated with more concentrated electrolyte solutions, of illite, or of montmorillonite. The presence of organic matter seems to enhance the degree of preferred orientation in argillaceous rocks. Odom (1963, 1964) found, in claystones overlying coal beds in Illinois, that the degree of preferred orientation correlated directly with the content of organic carbon (as C). This is substantiated by O’Brien’s (1963, p. 13) summary of his measurements of the preferred orientation of illite and kaolinite in black and gray shales of Pennsylvanian age in Illinois—the black shales, having an approximate range of orientation values from 10 to 20, contain more organic matter than the gray shales, having a range of orientation values from 6 to 10. Beall (1964, p. 86-87) also reported a greater degree of preferred orientation in the darker colored of some of the Cretaceous mudstones that he studied in Texas. These newer studies confirm the earlier work of Ingram (1953, p. 873-875) on the orientation of clay-mineral particles in clayey rocks, Ordovician to Eocene in age, from Colorado, Iowa, and Wisconsin. Ingram noted, in thin sections of the rocks, that organic stain was associated with clays that showed preferred orientation and was absent from clays in which the orientation was random. In one rock sample, this relation was expressed in alternate organic and nonorganic clay layers. Folk (1962, p. 541) has suggested that a large proportion of organic matter in a sediment may aid the development of preferred orientation by its initial deposition as a stagnant clay-organic “soup” which is compacted markedly and allows the clay flakes to become well oriented. Spatial variations of the preferred orientation of clay minerals with respect to depth of burial and the inferred environments of deposition of Cretaceous mudstones in Texas have been described by Beall (1964, p. 46-54, 104-107). He noted no variation in preferred orientation that could be related to overburden load or degree of compaction—that is, no relation between fabric and bulk density. He did note, however, lateral changes in preferred orientation that were related to changes in the inferred depositional environment: in one horizon that graded laterally from shallow-marine to near-shore sediments, the better preferred orientation was associated with deposits of a tidal mud flat or shallow lagoon. In an over-lying horizon, the whole pattern of depositional types and associated preferred orientation was shifted laterally, indicating a westward transgression of the Cretaceous sea. Beall concluded that preferred orien- tation was best developed in a low-energy brackish-water environment. The specific characteristics of the environment that are most responsible for the development of preferred orientation are not clearly shown, but he did note (as cited in the preceding paragraphs) relations with clay minerals, exchangeable cations, and the dark color of the rocks. These laboratory and field observations of preferred orientation can be summarized as follows. During the compaction of clayey sediments under pressures between 0 and 100 kg per cm2, most of the rearrangement of clay particles takes place and most of the preferred orientation is developed very early—at pressures of only a few kilograms per square centimeter. During this very early stage, the amount of water held in the clayey sediment may be the most critical factor. If enough water is present, the particles may slip past one another easily into efficient packing arrangements; if not, the preferred orientation may be poorly developed or absent. A large concentration of carbonaceous organic matter seems to assist the development of preferred orientation by its ability to retain large amounts of water during the early stages. The influence of other factors is less certain, but one might expect the development of preferred orientation to be favored by larger proportions of kaolinite and illite relative to montmorillonite, by lower concentrations of interstitial electrolytes, and perhaps by greater alkalinity of interstitial solutions. DEVELOPMENT OF TURBOSTRATIC ORIENTATION Whether a turbostratic fabric of the kind shown in figure SB can be formed during the compaction of clayey sediments is not certain. This fabric consists of domains of clay particles within which the planar orientation is nearly perfect and between which the orientation is random. If the domains were also oriented with respect to each other, this fabric would be nearly indistinguishable from the preferred orientation of individual particles shown in figure 3A. Note that the permeability of a clay that has a turbostratic fabric is greater than the permeability of a clay of the same water content that has preferred orientation—the two sketches in figure 3 are drawn with approximately equal void ratios. Several indirect lines of evidence, summarized from an earlier chapter (Meade, 1964, B9-B10, B18), suggest that a turbostratic fabric may develop under pressure in some montmorillonites. Montmorillonite that is mixed with electrolyte solutions containing calcium or magnesium and that has exchange positions saturated with these cations will not swell to interparticle distances greater than 9 ACOMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D9 (angstrom), regardless of the concentration of the interstitial electrolyte (Norrish, 1954). This is in contrast to mixtures of montmorillonite and sodium electrolytes in which the interparticle distance is a direct function of water content (greater than about 50 percent) and an inverse function of electrolyte concentration (less than about 0.3 M). Nitrogen-sorption measurements of calcium montmorillonite by Aylmore and Quirk (1962, p. 109-112) showed the existence of two different sizes of interparticle spaces, the smaller of which was on the order of 10 A, which suggested a particle arrangement such as the one shown in figure SB. Other experiments suggest that pressure may assist in the development of domains in calcium montmorillonite or in sodium montmorillonite associated with a concentrated electrolyte. From measurements of the sharpness of X-ray reflections from compressed calcium montmorillonite, Blackmore and Miller (1961, p. 171) inferred that the number of unit 10-A sheets per domain increased progressively with pressure and ranged from about five unit sheets at 0.5 kg per cm2 to nearly eight unit sheets at 90 kg per cm2. The process seemed to be irreversible; that is, the sheets in the domains did not seem to dissociate when the pressure was released. In sodium montmorillonite compressed under 800 kg per cm2, Engelhardt and Gaida (1963, p. 926) found that increasing concentrations of interstitial sodium chloride solution (from 0.16 to 1.1 M) were related to decreasing degrees of preferred orientation and increasing permeabilities. The equilibrium water content, however, was the same at all sodium chloride concentrations. These results may be explained by a lessening development of preferred orientation and a greater degree of turbostratic orientation at the higher concentrations. Because of the small size of the domains and their random orientation, however, the existence of a turbostratic fabric is difficult to prove, either optically or by X-ray diffraction. REDUCTION OF PORE VOLUME IN SANDS AT PRESSURES LESS THAN 100 KILOGRAMS PER SQUARE CENTIMETER The compaction of sands and the factors that influence the pore volume of sands and sandstones under pressure have received less attention than the corresponding processes and factors in clays and shales. One reason is that the decrease in pore volume with increasing depth of burial is not as easily observed in sands and sandstones as it is in clays and shales because cementation and other effects obscure the relation. Another reason is that unconsolidated sands are difficult to core and nearly impossible to bring to the laboratory without disturbing their natural pore volume. Furthermore, sands have not received the same attention from soil engineers that clays have because sands cause fewer difficulties in foundation engineering. Information on the response of sands to increasing pressures between 0 and 100 kg per cm2 consists of laboratory compression tests summarized in table 1. One cannot extrapolate indiscriminately from these results to most natural sands because the comprehensive testing to date has all been done on pure quartz sands in a restricted range of sizes. Although the experiments were made under different conditions (sample dimensions, rate of pressure application), they seem to show that the void ratio of a well-sorted and rounded quartz sand will decrease by about 0.03 in pressures from 0 to 70 kg per cm2. If the sand consists of angular grains, its void ratio will decrease by 0.15 to 0.30 in the same pressure range. Under pressures between 0 and 100 kg per cm2, the experimental quartz sands compacted principally by the shifting of particles into more dense packing arrangements and, to a lesser degree, by elastic compression of the grains themselves. At pressures in excess of about 100 kg per cm2 (especially in the experiments of Roberts and de Souza), the rate of compaction increased as the grains cracked and shattered under pressure. I doubt, however, that quartz grains would shatter extensively at these pressures in naturally compacting sands. The slow rate of pressure application in nature allows the grains to accommodate themselves in other ways, perhaps mainly by solution and reprecipitation at points of contact. Furthermore, polymineralic sands should respond differently to pressures, the softer grains deforming more readily and bearing much of the load. The factors that influence the pore volume of sands at pressures between 0 and 100 kg per cm2 are mainly the textural characteristics of the constituent particles: size, sorting, roundness, shape, and flexibility. The influence of these factors on the pore volume of un-compaoted sands has been reviewed and discussed extensively by Engelhardt (1960, p. 3-16), Fraser (1935), Gaither (1953), and Hamilton and Menard (1956). They will be reviewed here rather briefly, with some emphasis on their effects under pressure. INFLUENCE OF PARTICLE SIZE Although ideally the pore volume of well-sorted sands is independent of particle size, most natural sands show a slight inverse relation between pore volume and average size (fig. 4). Notice, however, that the relation is much more pronounced in silts than in sands. In sandstones or in sands that are buried under several hundred feet or more of overburden, the relation between pore volume and particle size is both similar toDIO MECHANICS OF AQUIFER SYSTEMS Table 1.—Summary of experimental data on compaction of unconsolidated sands [Void ratio and porosity at 70 kg per cm2 are interpolated from data as presented; 70 kg per cm2 represents approximate maximum pressure to which sands from cores in San Joaquin and Santa Clara Valleys have been subjected by natural overburden loads] Properties of sand Pore volume Reference Size (mm) Mineral composition Initial packing Roundness Interstitial fluid Void ratio at indicated pressure Porosity in percent volume at indicated pressure Initial 70 kg per cm2 Maxi- mum Initial 70 kg per cm2 Maxi- mum Terzaghi (1925, p. 987-988). Do 0. 25-1. 0 Quartz Loose. _ Angular Dry 0. 97 0. 66 0. 56 49. 2 39.8 35.9 . 25-1. 0 _ _do Compact- __do __do .67 . 53 . 45 40. 1 34. 7 31.0 Botset and Reed CO 1 (M ed. Compact- Kerosene. _ .70 .67 .60 41. 2 40. 1 37.5 (1935). Do .42- .6 ed by tamping. Compact- _ _do . 58 . 56 . 56 36.8 36.0 35. 9 Urul (1945—data ed six times at 210 kg per cm2. Dry .79 . 74 . 33 44. 0 42. 5 25. 0 reported by Weller, 1959, p. 295). Roberts and de Souza .42- .84 Quartz Loose. Rounded. _ Dry .65 .62 . 49 39. 4 38. 3 32. 9 (1958). Do .42- .84 (Ottawa). __do __do _ _do _ _do .60 . 58 . 31 37.5 36. 7 23.7 Do .42- .84 __do _ _do __do Water . 55 . 53 . 44 35. 5 34. 7 30. 6 Do .42- .84 Quartz __do Angular Dry. . 97 . 71 . 30 49. 2 41. 5 23. 1 Do .1 - .84 Quartz _ _do Rounded.. _ _do . 49 . 47 . 32 32. 9 32. 0 24. 2 (Ottawa). Table 1.-—Summary of experimental data on compaction of unconsolidated sands—Continued Reference Applied pressure (kg per cm2) Elastic recovery (percent difference in porosity at initial and maximum pressures) Grains crushed at maximum pressure (weight percent) Pressure application Dimensions of sample (cm) Initial Maximum Minimum interval Increment (kg per cm2) between applications (hours) Initial height Diam- eter Terzaghi (1925, p. 987- 0 110 None, presumably i 1/60 4.0 15 988). Do 0 115 do_ _ i 1/60 4. 0 15 Botset and Reed 0 240 27 5-12... 2 6.7 7 (1935). Do... . 0 210 80 8 (after 7 load- 5-12... 2 7 unload cycles). Urul (1945—data reported by Weller, 1959, p. 295). Roberts and de Souza 1. 3 1,970 410 Extensive About 15_ _ _ Two times previous increment, .do.. 24 1-2 3-1 (1958). Do 1. 3 985 About 50.. 24 1-2 3-1 Do 1. 3 575 .. ... _ _do__ 24 1-2 3-1 Do 1. 3 705 do _ 24 1-2 3-1 Do 1. 4 915 About 10.. _ _do__ _ _ _ _ 24 1-2 3-1 and different from the relation in unconsolidated sands. It is similar in that the pore space, if it is not filled by cement, increases with decreasing particle size: curve V in figure 4 represents Cretaceous sandstones buried under 3,580 to 3,680 feet of overburden. The relation may be different, however, in that the void ratio may be expressed as a linear, rather than curvilinear, function of the logarithm of the median particle size. Although this is only suggested in the narrow range of particle sizes represented by curve V, it is supported by other evidence that will be presented in the final sections of this paper.COMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA Dll INFLUENCE OF PARTICLE SORTING Sorting of constituent particles also affects the pore volume of a sand. “Generally the porosity decreases as grains vary from a uniform size because (a) the finer grains tend to occupy voids between larger grains and (b) the coarsest grains reduce porosity by occupying a <*> 6 4 2 0 Figubb 4.—Influence of particle size on void ratio of silts, sands, and sandstones. Curves I through IV represent unconsolidated sediments. I, North Sea bottom off Wilhelmshaven (modified from Fuchtbauer and Reineck, as reported by Engelhardt, 1960, p. 15) ; II and III, shallow sea bottom off San Diego (II, data from Shumway, 1960, p. 454—457; III, data from Hamilton and others, 1956, table 1) ; IV, Colorado Elver delta in Lake Mead (modified from Sherman, 1953, p. 399). Curve V represents Cretaceous sandstone (Germany) buried under 3,580 to 3,680 feet of overburden (modified from Engelhardt, 1960, p. 21). volume that would otherwise be occupied by finer grains and voids” (Gaither, 1953, p. 184). This statement is supported by the experiments of Rogers and Head (1961) on lognormally distributed artificial mixtures of different sand sizes (fig. 5A). The void ratio is related inversely to quartile deviation (QD—a measure of sorting which was introduced and explained by Krum-bein (1936, p. 102-103), and which is the logarithm to the base 2 of the Trask sorting coefficient, So (Trask, 1930, p. 594). Although the relations in figure 5A seem to plot as straight lines, they probably apply only to the short range of QDj, values indicated. If they were extrapolated, they would imply that sands whose quartile deviations amounted to 2.5 or more would have no porosity at all. The results plotted in figure 5A also show how particle sorting influences the relation between the pore volume and particle size of sands. In the well-sorted sands, the void ratio is virtually independent of the average particle size. As the sorting becomes poorer (QD$ increases), the void ratios of the different-sized sands diverge—the finer sands having the greater pore volumes. The influence of particle sorting on the relation between void ratio and pressure is indicated in figure 5B, which is adapted from the experimental data of Roberts and de Souza (1958) on well-rounded quartz grains. The void ratio of the less well sorted sand (greater QD# ) remained below that of the two better sorted sands at pressures up to a few hundred kilograms per square centimeter. At the greater experimental pressures, the well sorted sand was fractured more extensively (see details in table 1), and its void ratio-pressure curve converged with the curve for the less well o < cc o 5 > z UJ o cr UJ 0. UJ 5 D -J O > z £ o tr O 0. z UJ O £T UJ 0. UJ 5 D -J O > z if) o cr O 0. PRESSURE, IN KILOGRAMS PER SQUARE CENTIMETER Figure 5.—Influence of particle sorting on void ratio of sands. A, In artificial mixtures of fractions of two natural sands from Texas (modified from Rogers and Head, 1961, p. 469). B, In well-rounded pure-quartz sand under pressure (modified from Roberts and de Souza, 1958) ; median diameter (Md) of the two better sorted sands, 600 microns; median diameter of the poorer sorted sand, 480 microns ; details of pressure experiments listed in table 1.Dl,2 MECHANICS OF AQUIFER SYSTEMS sorted sand. As pointed out, however, this type and degree of fracturing is probably not common at these pressures in nature. INFLUENCE OF PARTICLE ROUND NESS The angularity of sand particles also affects the pore volume, as shown in figure 6 by the experiments of Roberts and de Souza (1958). Whereas the initial void ratio of angular, ground quartz was nearly 1.0, the initial void ratio of rounded quartz (Ottawa sand) was considerably lower—on the order of 0.6. The initial void ratio of the loose angular quartz used by Terzaghi (1925) in his experiments was also large (0.97), as shown in table 1. These void ratios reflect the instability of the initial packing of angular grains. Furthermore, angular sands are more compressible than rounded ones. This relation also has been observed in consolidated sandstone by Fatt (1958, p. 1940-1941) who noted that sandstones consisting of poorly sorted, angular grains are more compressible than sandstones whose grains are well sorted and rounded. INFLUENCE OF MICA PARTICLES If a sand contains a few percent of mica flakes, the flexibility and elasticity of the micas contribute to the compressibility of the whole. The pronounced effect of increasing mica content on the compressibility of prepared sand-mica mixtures has been demonstrated by Gilboy (1928). Figure 7A shows the results of some of his experiments on mixtures of rounded quartz grains and “white mica” (presumably muscovite) flakes. The larger initial pore volume of the more micaceous sands is apparently caused by bridging of open spaces by the mica flakes. Because the flakes respond to pressure by bending around spherical grains, the more micaceous PRESSURE, IN KILOGRAMS PER SQUARE CENTIMETER Figure 6.—Influence of degree of roundness of pure quartz, 420 to 840 microns in size, on relation between void ratio and pressure. Modified from Roberts and de Souza (1958). Details of experiments listed in table 1. sands are more compressible and their greatest compaction takes place at lower pressures than in less micaceous sands. Note also the greater elastic rebound upon release of pressure on the more micaceous sands. Results of experiments made by McCarthy and Leonard (1963) on the compressibility of mixtures of different proportions of two different sizes of fine muscovite and a natural sandy silt from Pennsylvania are shown in figures 7B and 70. Because the samples were compacted dynamically by tamping rather than being compressed under a static load, the results are not strictly comparable to those in figure 7A, nor are they directly applicable to equivalent sediments under natural loads. The results do show, however, that the addition of mica increases the void ratio of the silt and that, the finer the mica, the greater the increase in void ratio per unit increase in mica content. INFLUENCE OF INTERSTITIAL WATER The degree to which the presence or absence of interstitial water influences the compressibility of a sand is related to the amount of finer material that the sand contains. In clean sands, the compressibility is apparently independent of the water content. Terzaghi (1925, p. 987) noted this in his early experiments, and the results obtained by Roberts and de Souza (1958) substantiate his observations. In figure 8, the difference in void ratio between wet and dry sands is the same as the difference between duplicate tests on the dry sand. When clay is present in sufficient quantity to act as a binder or as a coating on sand grains, however, the difference between the behavior of the wet and dry aggregates is substantial. Bull (1964, p. A58-A59), for example, made compression tests on a sand that contained 5 percent clay, most of which was montmoril-lonite. The sand was markedly more compressible when wet than when dry. In the compression tests made by McCarthy and Leonard (1963) on sands and silts mixed with different proportions of mica, the water content had a small but markedly consistent effect on the compaction. In the range of water contents roughly between 39 and 84 percent of saturation and in the range of mica contents between 0 and 100 percent, the void ratio at a given pressure was nearly always smaller (by 0.01 to 0.04) in the more saturated sediments. This indicated a small but consistent influence of water content on the efficiency of the compaction. PORE VOLUME OF SANDSTONES AT PRESSURES GREATER THAN 100 KILOGRAMS PER SQUARE CENTIMETER Although studies of the porosity of sandstones and the factors that influence it at pressures greater than 100 kg per cm2 (depth of burial about 3,000 feet) areCOMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D13 not directly applicable to the studies that follow this review, they indicate effects that may be incipient at lower pressures and they provide useful insights. Although the work reviewed below relates to sandstones rather than sands, its chief asset is that most of it is based on natural sedimentary rocks rather than on sands prepared in the laboratory. The porosity of sandstones seems to decrease regularly with increasing depth of burial. In well-sorted quartzose sandstones, the relation between depth of burial and percent porosity (rather than void ratio) may be linear (Maxwell, 1964; Philipp and others, 1963a, p. 461; 1963b, p. 465; or Fiichtbauer and Reineck, 1963, p. 304). On the basis of the available studies, however, one cannot be certain of the depth range in which such a linear relation might apply (Walker and Maxwell, 1964), or what form the relation might have in poorly sorted mixtures of sand, silt, and clay. One of the most informative studies of the processes by which sandstones respond to pressure was made by Taylor (1950). In thin sections of Mesozoic sandstones from Wyoming, she studied the number and types of contacts between sand grains. The number of contacts increased with increasing depth of burial, and the type Figure 7.—Influence of proportion and size of mica particles on relations between void ratio and pressure in sands and silts. Percentage of mica by weight indicated on each diagram. A, Artificial mixtures of mica and quartz ; particles of both constituents 420 to 590 microns in size (modified from Gilboy, 1928, p. 560). B, Sandy silt (Md = 60 microns, QD =1.7, material finer than 4 microns in size = 12 percent) mixed with silt-sized mica (Md = 24 microns, QD =2.5)-; water saturation 80 to 82 percent (modified from McCarthy and Leonard, 1963, p. 33). Ct Sandy silt as in B, mixed with finer grained mica (Md = 7 microns, QD = 0.7) ; water saturation 78 to 80 percent (modified after McCarthy and Leonard, 1963, p. 34). 280-804 0—67------3D14 MECHANICS OF AQUIFER SYSTEMS changed progressively from tangential through long and concavo-convex to sutured. She believed that the progressive change of contact type was due to (1) solid flow of material under pressure and (2) solution and redeposition of dissolved material, both of which were caused by the pressure that accompanied deep burial. Other pressure effects that she observed were “the crushing and yielding of micas, feldspar and rock fragments, and the development of tension and pressure cracks in the grains” (p. 715). Unfortunately, she did not report the depths at which these phenomena became important. Factors other than pressure that have been clearly shown to affect the porosity of sandstones are the interstitial cement (carbonate or silica), the size of the sand particles, and temperature. The effect of interparticle cement on porosity is intuitively obvious, and it is documented by recent detailed studies. Clear inverse relations between porosity and calcite content, for example, are described by Fiichtbauer (1964, p. 243-244) in Tertiary sandstones buried at depths between 3,600 and 11,500 feet in Switzerland, Austria, and Bavaria. Similar inverse relations between porosity and silica overgrowths on quartz grains are shown by Fuchtbauer (1961, p. 172-173) in Mesozoic sandstones buried at depths between 4,700 and 5,300 feet in northwest Germany. Inverse relations between porosity and the amount of cementing material (both carbonate and silica) are also revealed by the statistical studies of Paleozoic sandstones in the Appalachian region by Griffiths (1964, p. 653-664) and his students. (See also Griffiths, 1958, p. 27-29.) In sandstones that do not contain large proportions of cement, the relations of porosity to particle size and, to a lesser extent, particle sorting are often clearly visible (curve V in fig. 4; Griffiths, 1958, p. 27-29; 1964, PRESSURE. IN KILOGRAMS PER SQUARE CENTIMETER Figure 8.—Influence of interstitial water on relation between void ratio and pressure in well-sorted clean quartz sands. Modified from Roberts and de Souza 1958). Details of experiments in table 1. p. 652- 664). Whereas the relation between porosity and particle size in sandstones is often inverse, it occasionally is found to be direct—that is, in some sandstones the porosity increases with increasing particle size (Fuchtbauer, 1964, p. 243-244; McCulloh, 1964; Moda-ressi and Griffiths, 1963, p. 258). This reversal in the relation between porosity and particle size is at least partly a function of the depth of burial. Although finer sediments have greater initial porosities than coarser sediments, they are compressed more rapidly during the early stages of compaction. As compaction continues with progressive depth of burial, a critical depth or depth range must be reached at which the porosity of the finer sediments equals that of the coarser and below which the porosity of the finer sediments is less than that of the coarser. This extrapolation is supported by the well-known fact that, among older or deeply buried sediments, sandstones are usually more porous than closely associated claystones—see, for example, the data of Proshlyakov cited by Maxwell (1964, p. 698). The effects of temperature on the porosity of quartz-ose sandstones are best shown in the laboratory experiments and, to a lesser extent, in the analysis of field data by Maxwell (1960, 1964). Two main effects were observed in the laboratory experiments. Increasing temperatures from 20° to 235° C and from 270° to 345° C increased the compaction of quartz sands under a fixed pressure of about 2,000 kg per cm2—roughly equivalent to a depth of burial of 26,500 feet. The greater temperatures apparently decreased the strength of the quartz grains so that they failed mechanically under pressure. Furthermore, temperatures greater than 270° C seem to enhance the solution of silica and its reprecipitation as interparticle cement. The reduction of porosity in sandstones seems to be a time-dependent process. In Maxwell’s laboratory studies (1960), the longer the experimental conditions of temperature and pressure were maintained (up to 100 days), the greater the observed decrease in porosity. Observations of progressively smaller porosities in successively older natural sediments by Maxwell (1964) and McCulloh (1964) supported the laboratory results and led Maxwell to suggest (1964, p. 708) “that compaction will continue so long as porosity exists; that is, there is no suggestion of an equilibrium porosity at a given depth which would persist throughout geologic time.” SUMMARY OF PETROLOGY OF SEDIMENTS IN AREAS OF LAND SUBSIDENCE The petrologic features of the sediments whose compaction accounts for the observed land subsidence in central California were described in some detail in theCOMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAN® SUBSIDENCE IN CENTRAL CALIFORNIA D15 preceding chapter in this series (Meade, 1967). Special emphasis was given to the features that influence the compaction behavior of the sediments. A short summary is given here as general background for the studies that follow. Selected petrologic features are plotted against depth in figure 10. The sediments included in the studies that follow were collected from eight cored sections whose locations are shown in figure 9. Four of the cores—Oro Loma, Mendota, Cantua Creek, and Huron—were taken in the Los Banos-Kettleman City area on the west side of the San Joaquin Valley. Two cores—Pixley and Rich-grove—were taken in the Tulare-Wasco area on the east side of the San Joaquin Valley. Two cores—Sunnyvale and San Jose—were taken in the Santa Clara Valley. Details of the coring procedure, core recovery, and sampling are given in an earlier chaipter (Meade, 1967, p. 2-3, 48). The source terranes of the sediments, identified by the distinctive assemblages of minerals and rock fragments that comprise the sand and gravel fractions, are represented by letter symbols in the composite logs in figure 10. The sediments in the Sunnyvale and San Jose cores in the Santa Clara Valley were derived entirely from the Coast Ranges—specifically, the Diablo and Santa Cruz ranges that flank the valley on the northeast and southwest. The sediments in the Pixley and Rich-grove cores in the Tulare-Wasco area were derived entirely from the Sierra Nevada. The sediments in the 122° 120" Oro Loma, Mendota, Cantua Creek, and Huron cores in the Los Banos-Kettleman City area were derived from both the Sierra Nevada and the Coast Ranges. The sediments are mainly alluvial, having been deposited either on alluvial fans or on the flood plains of perennial streams. This is shown in the second column of each composite log in figure 10. Other types of deposits, subsidiary in their abundance, are the lacustrine sediments cored in five of the six holes shown in the San Joaquin Valley, the shallow-marine sediments below about 760 feet in the Richgrove core, and the deltaic sediments below 1,800 feet in the Huron core. Particle sizes are represented indirectly by the electrical resistivity of the sediments and numerically by the median diameter. Resistivity, in the third column of each composite in figure 10, increases to the right; the greater resistivities are characteristic of the coarser sediments. Median diameter, in microns on a logarithmic scale, is plotted in the fourth column. The particle sizes are diverse, ranging from fine clay to gravel. The geometric mean size is probably in the coarse-silt range, or between 30 and 60 microns. The general degree of sorting is fair to poor; the average quartile deviation (QD4,) is about 2.0. The general degree of skewness of the particle-size distributions indicates (1) that the sizes are not distributed lognormally and (2) that the sediments contain disproportionately large admixtures of finer particles. Variations in the degree of rounding of the sand-sized particles are not extreme, ranging from subangular in quartz grains to subrounded in the softer rock fragments. The proportions of mica flakes in the sediments reflect the source terranes. Relative size of mica flakes Source of sediments Percent of mica to associated nonmica particles Los Banos-Kettleman City area [Cores: Oro Loma, Mendota, Cantua Creek, Huron] Sierra Nevada.................... 2 to 5, max 10................. Same or larger. Coast Range...................... Trace to 2, max 8______________ Same or smaller. Tulare-Wasco area [Cores: Pixley, Richgrove] Sierra Nevada.................... 2 to 5, max 10................. Same. Santa Clara Valley [Cores: Sunnyvale, San Jose] Coast Range...................... 0 to trace, max 1............... Figure 9.—Locations of core holes in central California.D16 MECHANICS OF AQUIFER SYSTEMS 0R0 LOMA 1 8 62 500 0.5 1 CANTUA CREEK EXPLANATION PIXLEY 1 8 62 4000 0.5 1 1.5 RICHGROVE 1 8 62 500 0.5 1 1 8 62 4000 0.5 1 SAN JOSE Figure 10.—Composite logs of petrologic characteristics of sediments cored in areas of land subsidence fa central California. Key to composites in upper right corner. Source terranes indicated by C(('oast Ranges), S (Sierra Nevada) and M (mixed Coast Range and Sierra Nevada). Types of deposits indicated by A (alluvial fan), F (flood plain), and L (lacustrine). Locations of core holes shown in figure 9.COMPACTION tOF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D17 More mica in larger flakes is present in the sediments derived from the Sierra Nevada. Montmorillonite is consistently the dominant clay mineral, as shown by the shaded area of the central column of each composite in figure 10. It comprises 60 to 80 percent of the clay-mineral assemblages and 5 to 25 percent of the different sections of sediments represented in the several cores. Yermiculite is included with montmorillonite in the log for the Pixley core. Other common but subsidiary clay minerals in the sediments, included in “other clays” in figure 10, are illite, chlorite, a kaolinite-type mineral, and mixed-layer illite-montmorillonite. Exchangeable cations, adsorbed largely by the montmorillonite, are represented in figure 10 in terms of the proportion of sodium (and hydrogen, in the Richgrove core) relative to calcium and magnesium. Calcium is the most abundant of the exchangeable cations. The proportion of adsorbed sodium increases downward in most of the cores, probably reflecting the corresnonding downward increase in the proportion of sodium dissolved in the associated interstitial waters. Although pore volume was not treated in detail in the preceding chapter in this series (Meade, 1967), it is included in figure 10 to show its spatial variations relative to variations in the petrologic characteristics. Expressed as void ratio, it is plotted in the right column of each composite. The largest void ratios are found in some of the lacustrine sediments of the Mendota and Pixley cores and in the shallow-marine sediments of the Richgrove core. No decrease in void ratio with increasing depth of burial is obvious. The most apparent relation is with particle size: the graphs of void ratio for several cores—especially Mendota, Richgrove, and Sunnyvale—are distorted mirror images of the graphs of median diameter. ANALYSIS OF FACTORS INFLUENCING COMPACTION OF THE SEDIMENTS This section of the report is an assessment of the influences of selected factors on the pore volume of the sediments whose compaction accounts for the land subsidence observed in central California. It consists mainly of two progressive multiple-regression analyses of successive factors or groups of factors. The first analysis explores the influence of overburden load, particle size, and particle sorting in a large number of samples in the following general steps: (1) evaluation of effects of overburden load, (2) relation of particle size to the variation in void ratio that is “unexplained” by load, (3) evaluation of combined effects of load and size, and (4) relation of particle sorting to the variation in void ratio that is “unexplained” by the com- bination of load and size. The other multiple-regression analysis is an attempt to sort out the relative influences of overburden load, particle size, clay minerals, exchangeable cations, electrolyte concentration, pH, fabric, and diatom content in a small group of fine-grained samples by successive eliminations of the less significant factors. In addition, the influence of montmorillonite is assessed qualitatively without resort to statistical techniques. Judging from experimental results such as the ones shown in figure 1G (others are shown in Meade, 1964, fig. 4) the large proportions of montmorillonite must exert a strong influence on the compaction behavior of these sediments. This influence cannot be demonstrated by statistical analysis because the montmorillonite content within the sediments does not vary sufficiently to cause any discernible variations in void ratio. The abundance of montmorillonite, however, probably contributes to the compaction behavior in several ways. The void ratios are probably larger and the sediments are probably more sensitive to changes in load than they would be if less montmorillonite were present. And the large exchange capacity and surface area of montmorillonite certainly contribute to the discernible effects of the different exchangeable cations on the void ratio shown in this report. Three progress reports of this work have been published (Meade, 1961b, 1963a, 1963b). The approach used in the earliest of these—involving computations of the amounts of adsorbed water and free pore water in clayey sediments in the Cantua Creek core—may not be valid. Two of the assumptions that were made, concerning the thickness of the layers of adsorbed water and the uniformity of interparticle distances, are questionable enough to throw serious doubts on that approach to the removal of water. In any event, all three earlier papers are superseded by this report. USE OF MULTIPLE-REGRESSION STATISTICS FOR ANALYSIS The statistical techniques of multiple-regression analysis are the principal tools used in this section of the study. These techniques have been used previously and successfully by Griffiths (1964) and his students to sort out the relative influences of different petrologic factors on the porosity of Paleozoic sandstones. Although this is a promising approach, especially because the necessary arduous computations can be done quickly on a digital computer, it involves some difficulties. In the first place, one must be able to give numerical values to each factor. For some factors, such as effective overburden load, one can use numerical measures that describe the factor fairly completely. For others, oneD18 MECHANICS OF AQUIFER SYSTEMS must use generalized index measures that do not describe the factor completely: the average size and sorting, for instance, do not characterize entirely the nonnormal distribution of particle sizes in many natural sediments. Another difficulty in using the techniques of multiple regression is that one must either find out or assume the nature of the numerical relations between the measure of pore volume and the measures of the influencing factors. That is, one needs to know whether the relations are linear or nonlinear. As these relations are virtually unknown, much of this chapter is concerned with attempts to discern their nature. This is a first step in applying numerical statistical techniques to the study of pore volume. For selected groups of samples, the following statistics were computed on the U.S. Geological Survey’s Burroughs 220 computer: 1. Correlation coefficients—simple, multiple, and par- tial—using void ratio as the dependent variable. 2. Probability of significance (Student’s t test) of cor- relation coefficients. 3. Regression equation of the straight line that best represents the observed relation between void ratio and the other variables. 4. Residuals (arithmetic differences) between the measured values of the void ratio and the values predicted from the regression equation. 5. Standard error of estimate of the void ratio. The simple correlation coefficient is a measure of the degree of linear correlation between any two variables; the multiple correlation coefficient measures the linear correlation between the dependent variable (void ratio in this study) and a combination of independent variables. When correlation is perfect, the coefficient (r) equals ±1 (the sign is a convention to indicate whether correlation is direct or inverse); when correlation is poor or absent, r values fall near zero. The significance test yields a probability (P) that the observed correlation is not due to chance alone. For example, when P equals 0.95, chances are 19 to 1 that the observed correlation is real rather than merely fortuitous. The standard error of estimate, expressed in units of the void ratio, is a measure of the deviation of the observed void ratios from the regression line. Approximately two-thirds of the observed void ratios should fall within one standard error of the values predicted from the regression equation. Approximately 19 observed values in 20 should fall within 2 standard errors of the predicted values. Several assumptions, in addition to the assumption that the numerical relations between void ratio and the independent variables are linear, are involved when probability statements, such as those in the preceding paragraphs, are made on the basis of the computed statistics. None of the assumptions are entirely satisfied by the data used in this study. The correlation coefficient is computed with the assumption that the sample errors are random and normally distributed. Significance tests concerning the equation of the regression line are based on the assumption that the distribution of the values of the void ratio that correspond to any single value of the independent variable follows the normal distribution law. The use of the standard error of estimate as in the preceding paragraph adds the additional assumption that the distribution of void ratio with respect to the independent variable is constant for all values of the independent variable. Although their underlying assumptions are not fulfilled entirely, these statistical measures and methods are used with the understanding that their interpretation involves more risk than is indicated by the statistics themselves. The statistical terms used in this paper are defined in the glossary. For simple and nontheoretical discussions of correlation and regression, see Ezekiel and Fox (1959), Fisher (1950), and Williams (1959). EFFECT OF OVERBURDEN LOAD The relations between pore volume and overburden load are examined in selected groups of alluvial sediments, including 135 samples from the Mendota, Cantua Creek, and Huron cores of the Los Banos-Kettleman City area and 23 samples from the Sunnyvale and San Jose cores of the Santa Clara Valley. The alluvial sediments are singled out for study because they are more abundant than the other types. No distinction is made between alluvial-fan and flood-plain deposits. The clays and clayey silts included among the analyzed samples are only those whose textures suggest that they were deposited by moving water (Meade, 1967, p. 7). Lacustrine sediments and other sediments whose finely laminated textures suggest that they were deposited in standing water (that is, some of the fine flood-plain deposits) are not included in the statistical study, nor are samples included that represent heterogeneous or cemented alluvial sediments. Clean, well-sorted sands are also excluded because they are the most likely to have been disrupted during the coring process; only those sands containing 25 percent or more of silt and clay are included. All sediments included in the analysis were collected from below the water table. No sediments from the Tulare-Wasco area are included in the analysis— the range of effective load between the water table and the bottom of the alluvial-fan sediments in the PixleyCOMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D19 and Richgrove cores (roughly 16 to 27 kg per cm2) is too small for the effects of load to be clearly visible. Void ratio and effective overburden load are the dependent and independent variables in this analysis. Depth of burial is not used as a variable because the presence of artesian pressures in the sediments causes the relation between depth and load to be irregular. I computed the void ratios from the porosity measurements that were made on these sediments by Johnson, Moston, and Morris (1967). Effective overburden loads were computed by subtracting the fluid pressures in the sands and gravels, as measured at the time that the sediments were cored, from the total load (bulk weight) of the overlying sediments. R. E. Miller computed the effective loads in the Los Banos-Kettleman City area; J. H. Green computed those in the Santa Clara Valley. Computed effective overburden loads are listed in “Appendix B.” The tabulated data represent loads that were computed at discrete points in the sections, based on the physical properties of the sediments and water-level conditions. The effective overburden loads at intervening depths, which were used in the statistical analysis, were estimated by linear interpolation between the data points listed in the table. The effective (grain-to-grain) loads computed for the sands and gravels, however, probably do not represent the effective loads in the adjacent silts and clays because of a time lag in the adjustment of the finer sediments to the rapid declines in artesian pressure. The artesian head in the sands and gravels has been falling at rates as great as 15 feet per year because of the excessive pumping of confined ground water. The less permeable silts and clays cannot equilibrate immediately to such a rapid change. Residual excess pore pressures remain in the finer sediments and decay at rates that are controlled by sediment thickness and permeability. These excess pore pressures cause the void ratios of the silts and clays to be larger than the void ratios that represent a state of equilibrium with the effective overburden pressures in the adjacent sands and gravels. Another effect that may limit the use of the void-ratio measurements is the expansive rebound that probably takes place when the overburden load is removed from the sediments as they are cored (Poland, 1963)MThe actual amount of rebound involved, however, is not easily determined. For laboratory tests made of compression and rebound of 48 of the fine clayey sediments from the San Joaquin and Santa Clara Valleys, rebound from the simulated field effective load to the unloaded condition was accompanied by an average increase in void ratio of about 0.1 (from 0.56 to 0.67). This rebound, however, took place in the presence of excess water over rather long periods of time. Saturated clays must imbibe water in order to swell, and the silts and clays whose void ratios are used in this study were not exposed to excess water long enough to swell to their full rebound capacity during the coring process. I suspect, therefore, that the increases in void ratio related to rebound experienced by these samples are considerably less than the 0.1 observed in the laboratory compression and rebound tests. The relation between void ratio and the logarithm of effective overburden load is assumed to be linear. This assumption is based on the data of Hedberg (1936, p. 256, 262) and Storer (1959, p. 520-523), which are summarized together by Engelhardt (1960, p. 39-42). These data suggest that the relation between void ratio and the logarithm of depth is linear in the depth range between 1,500 and 10,000 feet. Using these data to support the assumption of a linear relation between void ratio and the logarithm of effective load in the sediments of the San Joaquin and Santa Clara Valleys involves two further assumptions: (1) that the relation between depth and effective overburden load in the sediments studied by Hedberg and Storer is linear and (2) that the relation between void ratio and the logarithm of depth is also linear at depths shallower than 1,500 feet. Relations between void ratio and the logarithm of effective overburden load in the selected groups of alluvial sediments are shown in figure 11. The sediments from the Los Banos-Kettleman City area are segregated into four groups (A through D, fig. 11) by particle size in order to minimize the effects of the strong correlation between size and void ratio that is also found in these sediments (fig. 13). The 23 sediments from the Santa Clara Valley were treated in one group (E, fig. 11). Although the correlation between size and void ratio in this group is also strong (fig. 13), there are too few suitable samples from the Santa Clara Valley to permit any further segregation by particle size. Most of the sediments that were sampled in the Santa Clara Valley are either heterogeneously bedded or too full of calcite cement to be included in the analysis of pore volume. The solid lines through the scatter diagrams are the regression lines that best represent the observed change in void ratio with overburden load. The dashed lines represent approximately the 95-percent confidence limits: 19 void ratio observations in 20 should fall within these limits. Details of the regressions illustrated in figure 11 are listed in the upper part of table 2. The conspicuous gap in the plots for groups A through D, between loads of 25 and 35 kg per cm2, shows the manmade change in effective load across the principal layer of fine sediment (the lacustrine Corcoran Clay Member of the Tulare Formation) that confines the artesian aquifer system in the San Joaquin Valley. Samples that plot to the left of the gap are from theVOID RATIO D20 MECHANICS OF AQUIFER SYSTEMS GROUP A SILTY SANDS Clay GROUP B SANDY SILTS Clay EFFECTIVE OVERBURDEN LOAD, IN KILOGRAMS PER SQUARE CENTIMETER Figure 11.—Simple relations between void ratio and effective overburden load in fresh-water-bearing alluvial sediments. Groups A through D from Mendota, Cantua Creek, and Huron cores from Los Banos-Kettleman City area; group E from Sunnyvale and San Jose cores from Santa Clara Valley. Note different range of effective load for group E. Particle sizes i*n each group are represented by triangular sand-silt-clay diagrams, which are subdivided according to the system proposed by Shepard (1954).COMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D21 semiconfmed aquifer system above the confining layer; those to the right are from the confined artesian system. The gap represents the increase in effective overburden load caused by excessive pumping of the artesian water. The correlation between void ratio and load in the silty sands (group A) is not entirely as represented in figure 11. The void ratio also correlates significantly with QD4, (see bottom of table 2 and figure 16), and the correlation between load and QDt may be significant (r=0.29, P= 0.92). That is, the sorting becomes progressively poorer (QDt increases) at greater depths, and this accounts for part of the apparent decrease in pore volume with increasing load. The line representing the actual change of void ratio under increasing load, therefore, should be less steep than the regression line in figure 11. The silts and clays of groups B, C, and E show the most unequivocally significant relations between void ratio and load. The slopes of the regression lines in groups B and C should represent the relation between pore volume and load fairly clearly, as no simple correlation was observed between load and the particle-size variables in these groups. Note, in table 2, that the equations for the regression of void ratio on load are virtually identical for groups B and C. In the silty clays of group D, the decrease in void ratio with increasing load is only fairly significant (/>=0.88). The wide scatter of samples in this group may be related to variability in several other factors. Some sediments in this group, for example, contain aggregates of fine silt and oriented clay particles surrounded by a poorly sorted and disoriented sand-silt-clay matrix (Meade, 1967, p. 8); whereas other clays in this group contain few of these aggregates or none at all. Considering that the geometry of the pore space within the aggregates may be different from that of the pore space in the rest of the sediments, the variable proportions of aggregates may cause some of the wide scatter of points in group D. Another possible cause of the scatter is the influence of variations in particle size: The correlation between void ratio and median diameter (Md^) within group D is probably significant (P= 0.96). Still another cause might be differences in the elastic rebound of the clays between the time that they were cored and the time that their pore volume was measured in the laboratory, although, as stated previously, I doubt that this is a strong enough effect to account for the wide scatter in group D. And finally, considering also that the rate of decrease in the void ratio in group D is anomalously low, the scatter of Table 2.—Details of significant regressions of void ratio on effective overburden load, median particle diameter, and quartile deviation of particle-size distribution [e=void ratio, log Z=logarithm (base 10) of effective overburden load (in kg per cm2), .Afd*=median particle diameter ( units, see Inman, 1952, p. 133), QD«=quartile deviation (particle sorting, units, see Krumbein, 1936, p. 102-103)] Designa- Correia- Probability of Standard error Group tion in Number tion coef- significance Regression equation of estimate figures of samples ficient (r) of correlation coefficient (P) of void ratio Simple regressions of void ratio on effective overburden load Los Banos-Kettleman City—__________________________ A-D 135 -0.48 >0.99 e= 1. 15-0. 28 log L 0.11 Silty sand_______________________________________ A 39 —.40 >.99 e=l. 00 — 0.23 log L .12 Sandy silt___ __ ____________________ B 28 -.68 >.99 e=l. 33-0.39 log L .07 Clayey silt-_______________________________ C 40 -.62 >.99 e=l. 35-0.40 log L .08 Silty clay.____ D 28 -.30 .88 e=l. 00-0. 15 log L .12 Santa Clara._______________________________________ E 23 -.63 >.99 e=0. 90-0. 21 log L .08 Simple regressions of void ratio on median particle diameter Los Banos-Kettleman City__________________________ A-D 135 0.38 >0.99 e= 0.55+ 0.024 Md<, 0.11 Santa Clara____ E 23 .60 >.99 e= 0.33+0.048 itfd* .08 Tulare-Wasco_______________________________________ F 48 .52 >.99 e=0.37 + 0.054 Md* .10 Multiple regressions of void ratio on effective overburden load and average particle diameter Los Banos-Kettleman City_______________________ A—D 135 0.58 ^>0.99 e= 0.99 — 0.26 log L 0. 10 L-f 0.020 Md,f, Santa Clara____________________________________ E 23 .78 >.99 e=0.61 —0.18 log L .06 + 0.038 Md* Silty sand. Simple regression of void ratio on quartile deviation A 39 -0.44 >0.99 e= 0.81 —0.099 QD<, . 11D22 MECHANICS OF AQUIFER SYSTEMS points above the regression line may show the effect of residual excess pore pressures in the thicker silty clays of low permeability. EFFECT OF PARTICLE SIZE The decrease in pore volume that corresponds to increasing particle size is studied in 3 groups of alluvial sediments: those included in groups A through D (fig. 11) from the Los Banos-Kettleman City area, those in group E from the Santa Clara Valley, and a group of 48 alluvial-fan sediments from the 2 cores of the Tulare-Wasco area. These 48 samples were all taken from below the water table; excluded from the group are sediments that contain calcite cement or conspicuous soil cavities of the types shown in the earlier chapter (Meade, 1967, fig. 18). Void ratio and median diameter are the dependent and independent variables used in this part of the analysis of pore volume. The median diameters are taken from particle-size analyses that were made in the Hydrologic Laboratory of the Geological Survey. They are expressed logarithmically in units, wherein

notation.) Note that a numerical increase in Md$ corresponds to a decrease in median diameter. Whether the numercial relation between void ratio and Md# is linear is uncertain. From most of the studies that are summarized in figures 1A and 4, one might expect the relation to be nonlinear. Those studies, however, were done on sediments that were under overburden loads less than 1 kg per cm2. The large initial void ratios of sediments should be expected to be reduced rapidly under increasing overburden loads to values on the order of 1.5 or less (as shown in fig. 11). The question then becomes: Would such a reduction of void ratio involve a transformation of the numerical relation between void ratio and Md$ from a nonlinear relation to one that is essentially linear within the sand-silt-clay size range ? Considering that the fresh-water-bearing alluvial sediments of the San Joaquin and Santa Clara Valleys are all under significant overburden loads, one might suppose that the relations between void ratio and Md+ could be linear. This supposition is tested, but not conclusively, by plotting the residuals of the void ratioload equations against Md$ in 2 groups of sediments, namely the 135 samples of groups A through D and the 23 samples of group E (fig. 12). The residual is the difference expressed in void-ratio units between the measured value of the void ratio and the value predicted from the equation for the regression of void ratio on the effective load. (See the first and sixth equations listed 0.4 10 8 6 “i----------1---------1---------r Groups A-D 0.3 0.2 0.1 < cr V... •••• - :• o > -0.1 o Q LlI cr Q. O z < Q LU > cr LU (/> CD o -0.2 -0.3 - _]________l________I_______l_______I_______i i 16 62 250 UJ O z UJ cr 10 0.2 0 8 6 4 “1----1----1---1----1 Group E 0.1 - • • -0.1 - -0.2 - J________L_ _l________I________I 4 16 MEDIAN DIAMETER, IN MICRONS 62 Figure 12.—Relations between median diameter and the residuals of the void ratio-load regressions (observed void ratio minus the void ratio predicted by the regression equation) in sediments of groups A through D and group E. See figure 11 and table 2 for identification of groups.COMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D23 in table 2.) The residual is an indication of the variation in void ratio that is unaccounted for by variation in load. If its relation to Md$ is linear, then presumably the relation between void ratio and Md* also should be linear. Unfortunately, the scatter in the graphs of figure 12, reflecting the influence on void ratio of sampling error, and of factors other than load and average particle size, is so great that one cannot draw firm conclusions about the nature of the relation. These graphs do show that the pore volume decreases with increasing particle size. This, however, is shown more clearly in the simple correlations between void ratio and Md$ illustrated in figure 13. Figure 13 shows the simple relations between void ratio and the logarithm of median diameter in 3 groups of sediments: groups A through D taken together, group E, and the 48 samples from the Pixley and Rich-grove cores of the Tulare-Wasco area which are designated group F. As in figure 11, the solid and dashed lines represent the regression equation and the 95-percent confidence limits. Pertinent statistical details are <*> 10 8 6 4 2 I listed in table 2. In all three groups, the decrease in void ratio with increasing particle size (decreasing Md*) is clear. The relation between void ratio and Md+ seems to be approximately linear. COMBINED EFFECTS OF OVERBURDEN LOAD AND PARTICLE SIZE After treating separately the relations between pore volume and the two factors, overburden load and particle size, we may now consider the relations in combination with each other. This is done in two ways: (1) in qualitative terms of the influence of particle size on the relations between void ratio and load, and (2) in the numerical terms of multiple-regression analysis. The regression lines from figure 11 are grouped together in figure 14 for comparison with each other and with similar curves derived by Skempton (1953, p. 55). The curves in the upper graph in figure 14 are segments of the more complete curves shown in figure 12?. They represent the most complete synthesis of information of this sort that has been published so far. They show that, with decreasing particle size in the EFFECTIVE OVERBURDEN LOAD, IN KILOGRAMS PER SQUARE CENTIMETER MEDIAN DIAMETER, IN MICRONS Figure 13.—Simple relations between void ratio and median particle diameter in fresh-water-bearing alluvial sediments. Groups A through D and E as in figure 11. Group F from Pixley and Kichgrove cores of Tulare-Wasco area. Figure 14.—Influence of particle size on relations between void ratio and effective overburden load. Upper: As modified from summary by Skempton (1953, p. 55). Lower: As observed in San Joaquin and Santa Clara Valleys; letters correspond to sample groups in figure 11; dashed lines are from upper graph by Skempton.D24 MECHANICS OF AQUIFER SYSTEMS silt-clay range, the void ratio becomes greater at any given load, and it decreases more rapidly with increasing load. The sediments from the San Joaquin and Santa Clara Valleys (fig. 14, lower graph), however, do not behave exactly as predicted from Skempton’s curves. Before comparing Skempton’s results with those observed in California, one must understand that Skempton’s size nomenclature does not coincide with the nomenclature used in this report. His nomenclature is based on Atterberg limits; mine is based on particle-size analyses and the Shepard (1954) system. A basis for comparison of the two terminologies is the Atterberg limits of the California sediments, determined and reported by Johnson, Moston, and Morris (1967). The Atterberg limits show that the silts of groups B and C probably correspond to Skempton’s “silty clays,” and that the silts and clays of groups D and E probably correspond to Skempton’s “clays.” The silty sands (group A) presumably correspond to Skempton’s “silts.” Of the five groups of sediments, only those of group E have void ratios that might have been predicted from Skempton’s synthesis. The void ratios of the sediments in groups A through D are larger than expected. Why this might be so is uncertain. The sediments in all five groups have similar clay-mineral assemblages (fig. 10) and appear to have been in fairly similar chemical surroundings. The greater amount of sodium adsorbed by the clay minerals in the sediments of the Los Banos-Kettleman City area may contribute to their larger void ratios: experimental studies by others (fig. 1D) and evidence presented later in this chapter suggest strongly that the pore volume of montmorillonite-rich sediments is a direct function of the amount of sodium (versus cations of larger valence) adsorbed by the mont-morillonite. However, this would not account for the large void ratios in the silty sands (group A) which presumably do not contain enough clay to reflect strongly the influence of the adsorbed cations. Another difference between the sediments from the two areas of California is the almost complete lack of mica in the Santa Clara Valley and its relative abundance in many of the sediments of the Los Banos-Kettleman City area. As figure 7 shows, the presence of mica may influence the pore volume of sands and silts under loads as great as 10 kg per cm2. Perhaps it also influences the pore volume of sediments under larger loads. Whereas the slopes of the regression lines for groups A, B, and C correspond approximately to the slopes of Skempton’s curves for “silts” and “silty clays”, the regression line for group D is anomalous. If the analogy with Skempton’s curves is valid, the line for group D should be steeper than and entirely above the lines for groups B and C in figure 14. This anomaly could be accounted for by at least two possible factors—the downward increase in the proportion of adsorbed sodium or the residual excess pore pressures—both of which could cause the void ratios to be larger than anticipated in the artesian aquifer system below the principal confining layer. The second approach to the description of the combined relation of overburden load and particle size to pore volume is by way of multiple-regression analysis. Multiple-regression statistics for 2 groups of sediments, namely the 135 samples from the Los Banos-Kettleman City area and 23 samples from the Santa Clara Valley, are given near the bottom of table 2. Taking the correlation coefficients (the square root of the coefficient of determination—see glossary, p. D36) at face value, the combined influence of effective overburden load and average particle size accounts for 61 percent of the observed variance in void ratio in the sediments of the Santa Clara Valley and only 34 percent of the variance in void ratio observed in the Los Banos-Kettleman City area. This leaves approximately one-third and two-thirds of the variances in void ratio, respectively, to be accounted for by other factors. EFFECT OF PARTICLE SORTING Experimental studies of the influence of particle sorting on the pore volume of artificial sand mixtures (fig. 5) confirm the intuitive expectation that well-sorted sediments have larger pore volumes than poorly sorted sediments of the same average particle size. The numerical relations involved, however, are uncertain. Figure 5A shows the relation between void ratio and quartile deviation (QD4,) to be linear over a short range of QD^ values. The nature of the relation over a wider range of values in natural sands, silts, and clays is not known. In most of the central California sediments, simple correlations between void ratio and particle sorting are obscured by the more prominent relations of void ratio to overburden load and particle size. To minimize this difficulty, the sorting is compared to the variation in void ratio that is left over from or “unexplained” by the combined influence of load and particle size. That is, QD$ is graphed against the residuals (expressed in void-ratio units) of three regression equations: the two multiple-regression equations for groups A through D and group E and the equation for the regression of void ratio on median diameter for group F (table 2). Inasmuch as these equations assumed linear conditions, any conclusions that are drawn from the graphed relations between the residuals and QD* involve theDIFFERENCE BETWEEN OBSERVED AND PREDICTED VOID RATIO COMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D25 0.3 r Groups A-D 0.2 - 0.1 - 0 - -0.1 - -0.2 - -0.3 1 0.2 p Group E 0.1 -0.1 i 1 2 0.4 r Group F 0.3 - 0.2 - 0.1 - -0. 1 - -0.2 1 2 3 QUARTILE DEVIATION (QD) Figure 15.—Relations between quartile deviation and the residuals of void ratio-load-3fd* and void ratio-Mdt regressions (observed void ratio minus the void ratio predicted by the regression equation) in sediments of groups A through D, E, and F. assumptions that the relations of void ratio to Mand the logarithm of the effective load are linear. The graphs in figure 15 confirm the expectation that pore volume decreases with decreasing degree of sorting (increasing QD^). The graphs for groups A through D and group E also suggest that a sediment whose quartile deviation is 1 might have a void ratio that is about 0.2 larger than the void ratio of a sediment whose quartile deviation is 3<£. A significant simple correlation between void ratio and QD$ was found in the silty sands of group A (fig. 16), apparently because the range of QD$ values in this group was especially large. The simple regression equation given at the bottom of table 2 and illustrated in figure 16, however, does not represent the influence of sorting alone. The degree of sorting also decreases systematically with depth, so that the simple regression coefficient of either factor, load or QDreflects some of the effects of the other factor. The wide scatter in the graphs of figure 15 indicates that even when the relations with load, Md^, and QD^ are accounted for much of the variance in void ratio remains unexplained. It reflects the influence of other properties of the sediments or characteristics of their surroundings, some of which are evaluated below. COMBINED EFFECTS OF SELECTED PHYSICAL AND CHEMICAL FACTORS For several reasons, the sediments of the Richgrove core provide a good opportunity to evaluate some of the factors other than load that might influence the pore volume. In the first place, the apparent relation of the pore volume to depth and load is anomalous: the pore volume increases with increasing depth (fig. 17). The influence of other factors is more strongly expressed than that of load. Secondly, the variations in some of the other factors—the clay-mineral assemblage, adsorbed cations, and other chemical factors—are much greater in the sediments of the Richgrove core than in SORTING (So) 2 4 6 8 QUARTILE DEVIATION {QDq) Figure 16.—Simple relation between void ratio and quartile deviation in silty sands (group A) from Los Banos-Kettleman City area. See bottom of table 2 for details of regression equation.D26 MECHANICS OF AQUIFER SYSTEMS any of the other groups of sediments. These variations can be tested statistically to see if they correlate with variations in pore volume. Although the downward increase in pore volume in the Richgrove core can be related qualitatively and approximately to changes in the type of sediment and the particle size (fig. 17), these changes do not account for all the observed features of the distribution of pore VOID RATIO POROSITY, IN VOLUME PERCENT EFFECTIVE OVERBURDEN LOAD, IN KILOGRAMS PER SQUARE CENTIMETER Figure 17.—Relations of void ratio of fine sediments in Richgrove core (median diameters finer than 62 microns) to depth of burial, type of sedimentary deposit, and effective overburden load. volume with regard to depth. The finest of the nonmarine sediments above 760 feet are generally coarser than the fine-grained marine siltstones below 760 feet (fig. 10), so one might expect the marine siltstones to have generally larger pore volumes than the nonmarine sediments. The gradualness of the increase in pore volume between 600 and 1,300 feet, however, compared with the more abrupt change in the type of sediment between 745 and 785 feet, suggests strongly that other factors are influencing the pore volume. Twenty samples of the fine sediments in the Richgrove core were selected for analysis of a number of factors that might influence the pore volume. These factors are, in addition to overburden load and particle size: 1. Clay minerals, which are represented numerically by the percentage montmorillonite in the clay-mineral assemblage. 2. Exchangeable cations, which are represented numer- ically by the equivalent percentage of sodium in the exchangeable-cation assemblage. 3. Soluble salts, which are represented by the total dis- solved solids leached by 500 ml (milliliters) of hot water from 10 g (grams) of sediment. 4. Acidity, represented by the pH of a mixture of 10 ml distilled water and 1 g of sediment. 5. Orientation of clay-mineral particles, represented by the montmorillonite orientation ratio. The details of the procedures used in determining the clay minerals, exchangeable cations, soluble salts, and pH are given in the previous chapter (Meade, 1967, p. 65-72). The procedure for determining the orientation ratio is outlined in the next section. Also included in the analysis is the amount of diatom skeletal remains in the sediment; this amount was determined by point counts (300 points each) of thin sections of the sediments. Results of these analyses are listed in table 3. Multiple-regression techniques are used to sort out the important factors. All the measures that are listed for the 20 samples in table 3, with the exception of Md^,, register simple correlations with void ratio that are significant at the 99-percent level. Furthermore, many of them register significant simple correlations with load—a fact indicating that they change systematically with depth—or with each other. Analyses of simple correlations and regressions would be fruitless, therefore^ because of the complex and perhaps fortuitous interrelation of the factors. Multiple-regression techniques must be used with the hope that the variables that seem to be the most significant numerically do in fact represent the most important influences on pore volume. I assume for convenience that the relations between void ratio and the numerical indicators of eachCOMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D27 Table 3.-—Selected 'properties of fine sediments in Richgrove core Depth Effective Adsorbed cations4 Total dis- Diatom Sample 1 below overburden land load2 surface (kg per cm2) (feet) Void Median Montmorillonite ratio 3 diameter3 (percent of clay-(Md*) mineral fraction) - (adjusted percent of equivalents) Na Ca + Mg H solved solids in leachate 3 - (ppm) Montmoril-pH 4 Ionite orientation ratio 6 remains (percent of sediment) 59CAL319 148 7. 9 0. 62 8. 7 71 3 97 0 13 8. 3 1. 1 0 327 232 11. 2 52 4. 6 55 3 97 0 11 8. 7 1. 3 0 333 290 13. 2 67 5. 2 57 8 92 0 24 8. 7 1. 0 0 341 371 16. 0 50 4. 0 59 0 100 0 9 8. 9 1. 1 0 349 444 18. 5 51 5. 0 52 0 100 0 6 8. 7 . 8 0 356 517 20. 9 55 5. 8 56 0 100 0 24 9. 1 . 8 0 363 583 23. 1 63 5. 7 68 0 100 0 12 8. 6 1. 1 0 369 649 25. 0 71 7. 2 62 0 100 0 21 8. 7 1. 5 0 381 764 28. 7 98 7. 6 70 9 91 0 74 8. 4 1. 1 0 385 844 30. 9 96 6. 5 89 10 90 0 43 8. 7 1. 5 0 389 917 33. 1 88 6. 6 83 16 84 0 62 8. 5 1. 8 0 390 _ 1, 037 36. 4 l. 01 7. 8 68 20 80 0 94 8. 5 2. 0 0 394 1, 156 39. 4 l. 16 6. 1 80 19 81 0 41 8. 6 1. 8 3 396 1, 240 41. 3 l. 45 6. 6 76 25 46 29 173 4.5 1. 7 12 397 . 1, 364 44. 0 l. 11 5. 8 84 23 77 0 47 8. 7 1. 3 3 401 _ 1, 447 46. 1 l. 58 6. 1 86 30 42 28 286 4. 0 1. 4 6 403 . 1, 527 48. 3 l. 35 6. 2 83 33 20 47 300 4. 0 1. 6 12 404 1, 689 52. 0 l. 01 6. 7 89 26 74 0 69 7. 5 1. 6 0 410 _ 1, 827 55. 7 l. 08 7. 0 89 32 31 37 226 4. 1 1. 8 0 412 1, 912 57. 9 60 3. 6 83 18 55 27 98 5. 3 1. 0 0 1 Numbers assigned by Hydrologic Laboratory. 2 Estimated from hydrologic data by B. E. Lofgren. 3 From analyses made in Hydrologic Laboratory. 4 Determined by H. C. Starkey. 3 Determined by Claude Huffman and A. J. Bartell. 6 Determined with assistance of J. B. Corliss. of the factors are linear, even though no evidence is available to support this assumption for any of the factors other than load and average particle size. It must be understood that multiple regression is used here only to sort out the factors and not to derive any descriptive equations that can be applied generally to all sediments. The factors are sorted out by deriving regression equations for several combinations of variables, noting the level of significance of the partial correlation coefficients in each equation, and eliminating the variables that seem to be the least significant. The statistics on which this process is based are given in table 4. All the “significant” partial correlations (P>0.75) represented in the table are positive. At first inspection of the significance levels of the partial correlation coefficients, one may eliminate the following variables from further consideration: load, percentage of montmorillonite, and (although only evaluated once) orientation ratio. Although the evidence is not as clear, I suspect that pH may also be eliminated. If the diatoms are ignored for the moment, particle size, absorbed sodium, and soluble salts are the remaining factors. Of these, particle size and adsorbed sodium seem to be the most important. Soluble salts seem to be of subsidiary importance: note that the large significance levels for soluble salts are registered only when adsorbed sodium is left out of the analysis. Judging from the multiple correlation coefficient of 0.89 (third line from the bottom in table 4), these three factors together may account for about 80 percent of the observed variance in void ratio (/?2=0.79). Table 4.—Selected details of multiple regressions of void ratio on different combinations of variables, representing properties of selected fine sediments in Richgrove core. Standard Probability of significance (P)i of coefficient of partial correlation between void ratio and— Number of Number of Coefficient of error of esti- -------------------------------------------------------------------------------------------—— ----------— ------- samples independent multiple corre- mate of void Percentage of Percentage of Logio total Montmonl- Percentage of variables lation (ff) ratio Logio load Mi* montmoril- adsorbed Na dissolved pH Ionite orienta- diatoms Ionite solids tion ratio 20 8 0. 94 0. 14 20 6 . 94 . 14 20 5 .89 . 18 20 4 .89 . 17 20 4 .89 . 17 20 3 . 86 . 18 20 3 . 88 . 17 20 3 .86 . 18 20 3 . 89 . 16 15 4 .94 . 08 15 2 . 91 . 10 (2) 0.85 <0.75 0.81 (2) .96 <.75 .83 (2) . 88 (3) . 93 .........90 (s) .94 ____ .87 ........ .95 ____ .82 <.75 __________ ____ .94 ....... >.99 ____ .82 ____________ __________ .90 ______ .95 ____ .98 - .96 ____ .99 _______ __________ <0. 75 <.75 <.75 <.75 <.75 >.99 <0.75 <0.75 >0. 99 .99 <. 75 <. 75 >.99 <.75 . 85 <•75 _ . 91 >.99 1 One-sided significance test used for logio load, Mit, percentage of montmorillonite, 2 Positive (and therefore insignificant) partial correlation with void ratio, and percentage of adsorbed sodium; two-sided test used for other variables. (See Dixon « Negative (and therefore insignificant) partial correlation with void ratio, and Massey, 1957, p. 97-99.)D28 MECHANICS OF AQUIFER SYSTEM'S The influence of the diatoms cannot be evaluated properly by these methods because only five samples contain diatoms. The fact, however, that these five samples have the five largest void ratios suggests strongly that the diatom skeletons contribute significantly to the pore volume. This suggestion is supported by multiple-regression analyses of the 15 diatom-free samples (bottom two lines, table 4), in which the removal of the diatomaceous samples seems to improve the degree of multiple correlation with the other variables and lessen significantly the standard error of estimate of the void ratio. The specific effect of the diatom remains in the preservation of pore volume under load is uncertain. Perhaps the large open spaces in the skeletons themselves account for the larger void ratios. Or perhaps, as suggested by Hamilton (1964, p. 4263), the diatom skeletons contributed material to an incipient lithifica-tion process that kept the pore space open under load. That is, perhaps a little of the silica in the skeletons was dissolved and later reprecipitated at the contacts between sediment particles. Perhaps this slight reprecipitation of silica cemented the particles together but preserved the greater pore volume that was characteristic of a shallower depth of burial. No petrographic evidence of this process could be seen in thin sections of the siltstones; but one should not expect to be able to see such evidence because of the difficulty of resolving minute amounts of cementing material at contacts between fine particles. Hamilton’s suggestion does seem paradoxical, however, in that it calls upon cementation, a process that eventually fills pore space, to account for anomalously large pore volumes. The conclusion in any event is that particle size, the proportion of sodium adsorbed by the clays, and the amount of diatom skeletal material are the main factors influencing the pore volume of this group of sediments. This conclusion is supported by the studies of the sediments in the other cores. The influence of particle size is confirmed by the statistical studies summarized in figures 12 and 13. The influence of the downward increase in adsorbed sodium was suggested as a possible cause of the anomalously low slope of the void ratioload curve for group D (p. D24). And the influence of diatom skeletons is suggested by the large void ratios of the upper lacustrine layer in the Mendota core (the Corcoran Clay Member, at depths between 600 and 700 feet—see fig. 10), which also contains large proportions of diatom skeletons. But one must keep in mind that the variables are interdependent: the montmoril-lonite content, pH, and soluble-salt concentration, although they seem to be insignificant or only marginally significant, probably have an indirect influence on the void ratio through their influence on the amount of adsorbed sodium. Although variations in the amount of montmorillonite do not seem to correspond to variations in void ratio, the very presence of montmorillonite with its large cation-exchange capacity probably makes the influence of the exchangeable sodium large enough to be discernible. Furthermore, the proportion of sodium adsorbed by the montmorillonite (see Meade, 1967, fig. 26) is closely related to the concentration of soluble salts and to pH. FABRIC OF THE SEDIMENTS AND ITS RELATION TO OVERBURDEN LOAD AND OTHER FACTORS ORIENTATION OF CLAY-MINERAL PARTICLES The fabric of the fine sediments was studied with the aim of discovering any systematic changes that might be related to an increase in overburden load or to variations in other factors. The results showed no variation in fabric that could be related unequivocally to variation in load. The fabric does seem to vary significantly, however, between the different types of deposits. The best developed preferred orientation was found in lacustrine deposits; whereas little or no preferred orientation was found in alluvial-fan deposits, regardless of the depth of burial below the land surface. OBSERVATION AND MEASUREMENT The orientation of clay-mineral particles was observed in thin sections and was measured by a method involving the use of X-ray diffraction. The thin sections were prepared from samples of clayey sediments (whose natural moisture had been sealed in at the coring site) that had been impregnated in the laboratory with a waxlike polyethylene glycol compound according to the method described by Tourtelot (1961). The X-ray diffraction method for measuring preferred orientation, described in detail in an earlier paper (Meade, 1961a), involves a numerical comparison between the intensities of the basal (001) reflection and the nonbasal (020) reflection from montmorillonite. In the diffraction patterns from each of several sections of air-dry clay, the intensities of these reflections are measured and recorded. From these intensities a peak-height ratio, which is the height of the (001) trace on the diffractometer chart divided by the height of the (020) trace, is computed. Peak-height ratios are measured in at least three mutually perpendicular sections—one parallel, and the other two perpendicular to the bedding direction. (In some samples, six sections were scanned— the three mutually perpendicular sections plus sections at angles of 22°, 45°, and 67° to the bedding direction.) The peak-height ratios are combined into another ratio which is the quotient of the peak-height ratio of theCOMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D29 bedding-direction section divided by an average peak-height ratio for the two sections perpendicular to the bedding. This quotient is called the orientation ratio. Values of the orientation ratio near 1.0 signify random orientation of montmorillonite particles with regard to the bedding direction. Progressively larger values signify progressively greater degrees of orientation parallel to the bedding. The general range of orientation ratios or their equivalents measured by X-ray diffraction in sediments and sedimentary rocks is shown in the following listing. Approximate range of orientation ratio Devonian shales, Alberta 1________________________________ 6-13 Pennsylvanian clays and claystones, Illinois:2 Black shales__________________________________________ 10-20 Gray shales____________________________________________ 6-10 Underclays____________________________________________ 1- 3 Cretaceous mudstones, Texas 3_______________________________ 2-30 Cretaceous shales, Alberta and Saskatchewan 1______________ 2- 5 Pliocene to Recent sediments, California: Lacustrine clays____________________________________ 1. 5- 3 Marine silts and siltstones_________________________ 1. 5- 2 Flood-plain clays_____________________________________ 1- 2 Alluvial-fan clays__________________________________ «1 ' Computed from data of Kaarsberg, 1959, p. 469-470. 2 Data from O’Brien, 1963, p. 12-15. 3 Data from Beall, 1964, p. 154-158. The main advantage of the X-ray diffraction method is that it provides a numerical expression of orientation that can be used to compare the different amounts of orientation in different samples. The main disadvantages are (1) that it measures the orientation only with regard to a single arbitrarily selected direction and (2) that it measures only the bulk orientation over an area of 3 to 4 square centimeters and does not resolve small-scale orientations. Montmorillonite, the most abundant of the clay minerals in these sediments, is the mineral whose reflections were used in the study of orientation. The detailed study of orientation was confined to the sediments of the San Joaquin Valley. The sediments of the Santa Clara Valley were not included because they contain a chlorite mineral whose (001) reflection interferes with the (001) reflection of montmorillonite and obscures the relation between the intensity of the reflection and the orientation of montmorillonite. The degree of orientation observed in thin sections (in the samples for which sections were available) generally confirmed the amount of orientation that was measured by the X-ray method. RELATION TO DEPTH OF BURIAL AND TYPE OF SEDIMENTARY DEPOSIT The orientation ratios of fine sediments in the four cores from the Los Banos-Kettleman City area are plotted against depth in figure 18. Thirty-five of these measurements were presented and discussed in an earlier paper (Meade, 1961b). Figure 18 contains another 17 measurements, in sediments from the Cantua Creek and Huron cores, that were made since the earlier results were published. All samples were taken from sediments that had been below the water table and had presumably been saturated with water in their natural states. In most of the samples, sand and silt appeared to be “suspended” in clay. That is, the coarser particles did not touch one another, and the clay fraction must have borne any load that was placed on the sediment. Ignoring the types of deposits for the moment, the results plotted in figure 18 give little indication of progressive development of preferred orientation with increasing depth of burial. The range between 0.9 and 1.2 of most of the orientation ratios indicates that very little orientation of montmorillonite developed parallel to the bedding—either before or during compaction. Comparison of the orientation ratios to the type of deposit in which they were measured sheds more light on the observed variations in orientation. The best developed preferred orientation is found in the lacustrine deposits in the upper parts of the Oro Loma and Mend-ota cores—the Corcoran Clay Member of the Tulare Formation—although the orientation in the lacustrine ( ?) beds at the bottom of the Mendota core seems to be random. The alluvial-fan deposits consistently show the most random orientation. The orientation in the flood-plain deposits ranges from random to fairly well preferred (orientation ratios between 1.0 and 2.0). The differences in the orientation of montmorillonite particles in the different types of deposits perhaps reflect different means of deposition. In the still waters of a lake, the particles may have an opportunity to settle out individually into a well-oriented arrangement. On an alluvial fan, on the other hand, clayey materials are deposited rapidly, often in a heterogeneous mixture that includes an assortment of coarser particles. The clay particles have little opportunity, therefore, to develop a preferred fabric. On flood plains, the physical conditions of deposition probably range between those visualized in lakes and those on alluvial fans. Differences in the water content of the sediments, immediately following their deposition and during their burial beneath the first few tens of feet of overburden, may account for the differences in the orientation of montmorillonite. This supposition is based on results of the experimental work of Martin and O’Brien (reviewed on p. D7) which suggested (1) that the preferred orientation, if it develops at pressures lower than about 100 kg per cm2, forms at pressures near 1 kg per cm2D30 MECHANICS OF AQUIFER SYSTEMS and (2) that the amount of water in the clay at this early stage may determine the degree of development of the orientation. The lacustrine sediments must have remained saturated with water as long as the lake in which they were deposited remained in existence, and preferred orientation presumably could develop during the deposition of successive layers of sediment on the lake bottom. The alluvial-fan sediments, on the other hand, were dried out soon after they were deposited, and they did not become saturated with water again until they were buried below the water table. Judging from modern conditions in the Los Banos-Kettleman City area, the alluvial-fan sediments must have been covered with several hundred feet of overburden before they reached the water table. By the time that the sediments met the water table, the volume and geometry of their pore space were such that preferred orientation could not develop. As with the conditions of deposition discussed in the previous paragraph, one might expect the degree of water saturation in flood-plain sediments to have been intermediate between that in lacustrine sediments and that in alluvial fans. The orientation of montmorillonite particles in sediments from the Richgrove core of the Tulare-Wasco area is shown in figure 19. The 4 samples nearest the land surface may not have been saturated with water at the time that they were cored; the other 16 samples, taken from depths below 400 feet, were below the water table. The alluvial-fan sediments represented in figure 19 are coarser than those represented in figure 18. The sand and silt grains in the alluvial-fan sediments of the Richgrove core are not “suspended” in a clay matrix, and the sand-and-silt skeleton probably supports most of the overburden load. This textural arrangement was found also in many of the samples of marine siltstone. The orientation seems to be random in the alluvial-fan sediments that make up the uppermost 600 feet of the Richgrove core. Orientation ratios in the samples from this interval range between 0.8 and 1.3. In the marine siltstone layers, on the other hand, most of the orientation ratios fall into the range between 1.3 and 2.0, indicating a degree of orientation greater than in the alluvial-fan sediments but less than in the lacustrine Corcoran Clay Member in the Los Banos-Kettle-man City area. Within each type of deposit at Richgrove, there is little indication of a progressive increase in preferred orientation with depth. Such an increase should not be expected, however, in view of (1) the textural arrangement of sand and silt grains that prevents the load from being borne directly by the clay and (2) the observation (fig. 17) that the pore volume does not decrease systematically with increasing depth. 5 0 _l LU CD 1 f-0. L±J Q MONTMORILLONITE ORIENTATION RATIO 1 1500 1 1 1— AF • • FP LA ' . • • • • FP • • • • AF %* r~ > •%> MENDOTA CORE 2000 1 AF FP CANTUA CREEK CORE 2000 1 2 3 AF AF Deltaic ___I_____ HURON CORE Figure 18.—Relations of montmorillonite^particle orientation to depth of burial and type of deposit represented by fine sediments cored in Los Banos-Kettleman City area. Orientation ratios determined with assistance of J. B. Corliss. AF, alluvial-fan deposit; FP, flood-plain deposit; LA, lacustrine deposit.COMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D31 RELATION TO PARTICLE SIZE AND CHEMICAL FACTORS The previous work reviewed earlier in this paper showed that certain physical and chemical factors might be expected to help or hinder the tendency of a clay to develop preferred orientation under load. The relation of some of these factors—particle size, electrolyte concentration, exchangeable cations, and pH—to the orientation ratio is examined in the 11 samples of marine siltstone from the Richgrove core (depths between 764 and 1,827 feet below land surface). These samples were selected because (1) their relatively uniform lithology suggests approximately uniform conditions of deposition, (2) the orientation ratio and the other factors are variable enough to show differences that might be correlative, and (3) the data are already available from the analysis of pore volume (table 3). Multiple-regression techniques are used, in the same way that they were used in a preceding section (table 4), in an attempt to sort out the important factors. The montmorillonite orientation ratio is used as the dependent variable, and its numerical relation to each of the measures of the independent variables is assumed to be linear. The pertinent correlation and regression sta- MONTMORILLONITE ORIENTATION RATIO TYPE OF DEPOSIT 500 UJ O < Li. CC D (/) O z £ o 1000 £ 1500 - 2000 L Alluvial fan Flood plain Marine (siltstone) 2000 Marine (sand) Figure 19.—Relations of montmorillonite-particle orientation to depth of burial and type of deposit represented by fine sediments in Richgrove core. Orientation ratios determined with assistance of J. B. Corliss. tistics are listed in table 5. The significant partial correlations between the orientation ratio and each of the first three listed independent variables—effective load, Md$, and percentage of absorbed sodium—are positive. Partial correlations between the orientation ratio and the concentration of soluble salts are negative. The statistics listed in table 5 suggest that particle size, adsorbed sodium, and soluble salts may have some influence on the degree of preferred orientation in the marine siltstones. The multiple-correlation coefficient of 0.48 for the regression relation in which these three are used as the independent variables (bottom line, table 5) suggests that they only account for about one-fourth of the observed variance in orientation ratio (I?2 = 0.23). These conclusions are rather tentative, however, mainly because too few samples were available. DOMAINLIKE AGGREGATES Many of the fine alluvial-fan sediments of the Los Banos-Kettleman City area have a fabric that consists of sand-sized aggregates of clay-mineral particles in a matrix of poorly sorted and randomly oriented sand, silt, and clay. (See Meade, 1967, fig. 4.) The orientation of clay minerals within these domainlike aggregates is highly preferred, but the orientation of the aggregates with regard to each other or to any plane through the sediment is random. As the orientation is preferred in small areas only (a millimeter or so across) it was not detected by the X-ray diffraction method which integrates the bulk orientation over an area of 3 to 4 square centimeters. The oriented aggregates were apparently deposited as such, either as shale fragments or as fragments of previously deposited clay layers on the alluvial fan. These aggregates were observed in the alluvial-fan sediments of the Los Banos-Kettleman City area only; none were seen in the alluvial sediments of the Tulare-Wasco area or Santa Clara Valley. Whether or not this kind of orientation is enhanced by increasing overburden loads is not clear from the evidence visible in thin sections. Even though these Table 5.—Selected details of multiple regressions of orientation ratio on different combinations of variables representing properties of marine siltstones in Richgrove core Number of independent variables Coefficient of multiple correlation CR) Standard error of estimate of orientation ratio Probability of significance (P)»of coefficient of partial correlation between montmorillonite orientation ratio and— Logm load M d* Percentage of adsorbed sodium Logio total pH dissolved solids 4 0.61 0.27 <*) 0.88 0.87 0.87 4 .48 .30 .77 .81 <•75 (!) 3 .36 .30 0.76 <•75 <.75 .. 3 .48 .28 .81 .85 .77 1 One-sided significance test. (See Dixon and Massey, 1957, p. 97-99.) ! Negative (and therefore insignificant) partial correlation with orientation ratio.D32 MECHANICS OF AQUIFER SYSTEMS aggregates are much larger than the submicroscopic domains that supposedly characterize turbostatic orientation, perhaps their role during compaction is the enhancement of a fabric that is at least analogous to the one represented in figure 3B. The development or enhancement of turbostatic orientation in these sediments is possible on several counts. The main clay-mineral constituent is calcium-montmorillonite, which according to experimental evidence reviewed earlier may be susceptible to this kind of arrangement under pressure. Furthermore, perhaps the deposited aggregates provide nuclei for further orientation of clay-mineral particles under pressure. No evidence, however, was found in the sediments themselves to support or reject this possibility. A fruitful approach might be to measure the internal and external surface areas of the sediments (Diamond and Kinter, 1958) or their pore-size distributions (Aylmore and Quirky 1962, p. 109-115; Barrett and others, 1951) and look for changes under increasing overburden loads. DISTRIBUTION OF MONTMOBILI.ONITE ORIENTATION WITHIN THE SEDIMENTS The distribution of the orientation of montmoril-lonite particles within some of the sediments from the Huron and Richgrove cores is shown in figure 20. In this figure, the orientation is indicated by the ratio of the heights of the diffractometer peaks that represent the reflections from montmorillonite at 15 A and 4.4 A. Larger values of the peak-height ratio, within any one sediment, correspond to greater degrees of preferred orientation. Determinations for each sample were made for five planes of reference from 0° to 90° from the bedding direction. The peak-height ratio should not be confused within the orientation ratio used in figures 18 and 19, which is computed from the peak-height ratios of different sections. Within the alluvial-fan and the deltaic sediments (left and center columns, fig. 20), the distribution of the orientation from section to section varies in a random way from sample to sample. In the marine sediments from the Richgrove core (right column, fig. 20), the peak-height ratios seem to decrease at fairly regular rates with increasing angular distance from the direction of bedding. This indicates that the preferred orientation is not strictly confined to the plane of the bedding, but only reaches a maximum there. FABRIC OF SANDS This section of the report contains observations of the fabric of the sands and some inferences about how the observed fabric may be related to compaction. No quantitative measurements of sand fabric were made because the sands probably were disrupted somewhat during the coring process. Thin sections were made, however, and some features were observed in them. Indirect inferences were made by relating some of the observable features to the experimental studies whose results were reviewed earlier. Although its effects do not show in the thin sections, the simple movement of grains into more efficiently packed arrangements was probably the principal response of the sands to increasing overburden loads. This supposition is based mainly on the experimental work, reviewed earlier, on pure-quartz sands. Its chief modifications in polymineralic sands such as those in the San Joaquin and Santa Clara Valleys are the supplementary processes of distortion and bending of the softer and more flexible grains. PREPARATION OF THIN SECTIONS A group of well-sorted sands from the Mendota, Cantua Creek, and Huron cores of the Los Banos-Ket-tleman City area was selected for thin-section study. Their good sorting, atypical of the recovered sands as a whole, was a necessary requisite for the impregnating and sectioning procedures. The sands were sealed in wax at the coring sites to preserve their textures as well as possible. One must assume, however, that tlieir original textures were disturbed during the coring operations. In the laboratory, they were impregnated under partial vacuum with a polyester resin which, when hardened, has a refractive index of 1.54. Thin sections were made from the impregnated sands along planes normal (and, in some samples, parallel) to the lidding. The sections were taken from near the center of the core to minimize the disruptive effects of the coring. Sieve analyses of contiguous samples of the sands were also made and results have been published (Meade, 1967, table 7). DISTORTION OF COMPRESSIBLE GRAINS The distortion of compressible grains—elastic micas and nonelastic soft rock fragments—was observed in some of the sections. In the San Joaquin Valley this process is significant in the sands, derived from the Sierra Nevada, which usually contain 3 to 5 percent mica. And many sands, especially those in the Los Banos-Kettleman City area that are derived from the Diablo Range, contain fragments of soft materials such as partly weathered shales or metamorphic rocks. A few of the distorted grains are sketched in figure 21. The distortion of the mica in figure 21A is the most extreme example observed. A more typical degree of mica distortion is sketched in figure 215. This represents a minimum distortion of this grain because one cannot tell how much elastic recovery may have taken place between the time the sand was cored and the time itPEAK-HEIGHT RATIO (15A/4.4A) COMPACTION OP SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D33 DELTAIC HURON CORE Sample from 822-foot depth is from Cantua Creek core) ORIENTATION OF SECTION (DEGREES FROM BEDDING DIRECTION) 0 45 90 L___I__I___I___I 0 45 90 1 _____I_____I----1------1 ALLUVIAL FAN MARINE V RICHGROVE CORE 764 844 917 1037 1156 1240 1364 1447 1527 1689 1827 ______/ Figure 20.—Orientation of montmorillonite In sections cut at different angles to the bedding of sediments from Huron and Rlchgrove cores. Determined with the assistance of J. B. Corliss. DEPTH BELOW LAND SURFACE, IN FEETD34 MECHANICS OF AQUIFER SYSTEMS was impregnated and sectioned. Neither, incidentally, can one be certain of how much of the distortion is due to natural loading and how much is due to the coring procedure. In general, the wide thin flakes of mica were more distorted than the thick books. Other factors influencing the degree of distortion were the orientation of the flakes with regard to the compacting pressure, the size of the mica flakes relative to the sizes of adjoining grains, and the nature of the contacts between flakes and grains. Because of the direction of orientation and poor contacts with adjacent grains, for instance, some mica flakes in the section from which figure 21A was sketched showed no evidence of distortion. Shale fragments were broken and squeezed by pressure exerted through more resistant adjoining grains. The distortion in figure 21C is as severe as any observed in the sand sections. The distortion of soft rock fragments was controlled by the same factors that controlled the distortion of micas. ORIENTATION OF MICA PARTICLES Two mica fabrics—differing in the orientation of mica flakes and the size of the flakes relative to the nonmica grains—are illustrated in thin-section views of sands from the Mendota core. Figure 22A shows a micaceous sand derived from the Sierra Nevada; figure 22R, one derived from the Diablo Range. In the sand derived from the Sierra, the larger mica flakes tend to be oriented parallel to the bedding. The long dimensions of the mica flakes are generally larger than the A C Figure 21.—Distortion of compressible sand grains. A, Bent and broken biotite; Mendota core, depth 1,347 feet. B, Bent biotite; Cantua Creek core, depth 1,551 feet. C, Crushed and broken shale fragment (stippled) ; Mendota core, depth 1,347 feet. diameters of the nonmicaceous grains. In the sand derived'from the Diablo Range (fig. 22B), the long dimensions of the micas are approximately the same as the diameters of the nonmicaceous grains. Furthermore, the micas are oriented roughly at angles of 45° to the bedding. One cannot be certain whether the orientation is a depositional feature or a result of changes during compaction, but W. B. Bull (written commun., 1964) says that such an orientation is common in the modern alluvial sands in the western San Joaquin Valley. Because of their different mica fabrics, these two sands should be expected to respond differently to compacting pressures. The mica flakes shown in figure 2QA should respond to loads by bending around adjacent grains, a process that enhances the compressibility of the aggregate. In the event that the pressure is released, the large mica flakes should regain some of their original shape, giving the aggregate a certain amount of elasticity. In the sand shown in figure 22R, on the other hand, one should expect a greater degree of compressibility but a lesser degree of elasticity. Their size, shape, and orientation should allow the mica particles to slip more easily past the nonmica particles (or vice versa) into more compact arrangements; but this kind of movement is largely irreversible. The compressibility of both these sands, however, is probably greater than that of otherwise equivalent sands that contain no mica. CONCLUSIONS In the fresh-water-bearing alluvial clays, silts, and silty sands in the San Joaquin and Santa Clara Valleys of California, the loss in pore volume that results from compaction by effective overburden loads in the range between 3 and 70 kg per cm2 averages about 0.3 void-ratio units or about 15 percent of the bulk volume of the fine sediments. When one allows for the lesser compaction of the interbedded coarser sands and gravels, the reduction of the total volume of the alluvial sediments amounts to about 12 percent between 10 and 70 kg per cm2 on the west side of the San Joaquin Valley and about 10 percent between 3 and 33 kg per cm2 in the Santa Clara Valley. The factors that directly influence the pore volume of the alluvial and shallow-marine sediments under these loads are the average particle size, the particle sorting, the large proportion of montmorillonite, the proportion of exchangeable sodium relative to exchangeable calcium and magnesium, and the presence of diatom skeletons. Although not shown by direct evidence, the proportion of mica probably also influences the pore volume. Factors having at least indirect influence, if not direct influence, are the acidity of the sediments and the concentration of interstitial electrolytes. The relativeCOMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D35 importance of all these factors is not easily evaluated because (1) their interrelations are often complex and (2) some of them are too constant (the proportion of montmorillonite, for example) to show variable effects on pore volume within this group of sediments. But one can distinguish with a fair degree of certainty the factors of primary importance from those of subsidiary importance. The average particle size and the content of diatom skeletons are certainly primary factors. Under these overburden loads, a sediment that has a median diameter of 1 micron can be expected to have a void ratio greater by at least 0.2 (about 7 percent of the total sediment volume) than a sediment whose median diameter is 100 microns. Diatom skeletons, where they are present, increase the pore volume markedly. In sands and silts, the influences of the particle sorting and the proportion of mica flakes on the pore volume are probably of subsidiary importance. Whether particle sorting is a primary or subsidiary factor is not clear. Rather uncertain statistical correlations suggest that one might expect a difference in void ratio near 0.2 between sediments whose QD+ values are 1 and 3; but the relation of pore volume to sorting is probably less important and almost certainly less pervasive than the relation to average particle size. The ranges of mica content and overburden loads in the sediments and the experimental work carried out in previous studies indicate that the differences in the mica content probably do not cause differences in void ratio much greater than 0.1. In the more clayey sediments, the content of montmorillonite and the proportion of adsorbed sodium become important. Judging mainly from the previous experimental work, the large proportion of montmorillonite must be a primary influence on the pore volume. No numerical estimates are made of the range of its possible effects, but the sediments of the San Joaquin and Santa Clara Valleys are certainly more porous than they would be if their principal clay-mineral constituents were illite or kaolinite. The proportion of adsorbed sodium relative to the other exchangeable cations is probably of subsidiary importance because (1) it is closely related to the pH and concentration of the interstitial electrolytes and (2) its total effect depends on the amount of clay-mineral surface available for cation sorption—the amount of montmorillonite, in these sediments. The degree of preferred orientation of the montmorillonite particles parallel to the bedding direction is consistently related to the depositional types of the fine sediments. Lacustrine sediments show the greatest degree of orientation; alluvial-fan sediments, the smallest degree; flood-plain and shallow-marine sediments show intermediate degrees of orientation. However, there is no clear identification of the specific properties of the sediments or characteristics of the depositional environments that control the degree of orientation. A , B 1mm Figure 22.—Sections of micaceous sands from Mendota core. Sections cut normal to bedding, which is parallel to top of page. A, Flood-plain sand from 833 feet; Sierra Nevada source. Mainly quartz, potassium feldspar, twinned plagioclase (light cleavage), biotite, shale fragments (strippled), and a little hornblende. B, Flood-plain sand from 1,076 feet; Diablo Range source. Mainly quartz, potassium feldspar, “dirty” twinned plagioclase (light cleavage), shale and other rock fragments (strippled), biotite, chlorite, and dark accessory minerals. Optical relief of grains exaggerated in both sections.D36 MECHANICS OF AQUIFER SYSTEMS Experimental work by O’Brien and the inferred post-depositional histories of the sediments suggest that the water content of the sediments during the very early stages of compaction may be a critical factor. A limited regression analysis suggests that the development of preferred orientation in the shallow-marine sediments may be favored by decreasing particle size, decreasing concentration of interstitial electrolyte, and increasing proportion of sodium adsorbed by the montmorillonite. Only the influence of electrolyte concentration is well supported by experimental studies. The most certain conclusions from the study of clay fabric are negative: the degree of preferred orientation of the montmorillonite does not increase with decreasing pore volume or with increasing depth of burial beneath overburden loads as great as 70 kg per cm2. GLOSSARY OF STATISTICAL TERMS Most of the statistical terms used in this report and in another report (Meade, 1967) in this series are defined below. Many of these definitions were taken, with little or no modification, from James and James (1949). References to further explanation and discussion are given after most of the definitions. Coefficient of determination. The percentage to which the variance in the dependent variable is determined by the independent variable or variables. The square of the coefficient of linear correlation. Correlation coefficient or coefficient of linear correlation. A number between —1 and +1 that indicates the degree of linear relationship between two or more sets of numbers. See Coefficient of determination. The simple correlation coefficient (r) indicates the degree of linear correlation between two sets of numbers. The multiple correlation coefficient (R) indicates the degree of linear correlation between one set of numbers (values of the dependent variable) and a combination of two or more sets of numbers (values of the independent variables). The partial correlation coefficient indicates the degree of linear correlation between the dependent variable and one of the independent variables, while eliminating the linear tendency of the remaining independent variables to obscure the relation. See Ezekiel and Fox (1959, p. 127-129, 190-197), Fisher (1950, p. 175-210), Moroney (1956, p. 271-320), and Waugh (1952, p. 446-449, 508-509). Cumulative frequency. The sum of all preceding frequencies, a certain order having been established. Dependent variable. A quantity that takes on a value corresponding to every value or set of values of another variable or set of variables (called independent variables). For example, in the regression equations y=a+bx, or y=a-\-bx-\-cz, where y is the dependent variable, x and z are independent variables; and & and c are regression coefficients. See Ezekiel and Fox (1959, p. 47—48) and Fisher (1950, p. 129-130). Independent variable. See Dependent variable. Mean. The sum of observed values, divided by the number of values observed. Measures of central tendency. Values loosely referred to as “averages”. Measures of central tendency used in these reports are the mean, median, and mode. See Moroney (1956, p. 34-55), and Waugh (1952, p. 61-125). Median. The midpoint of a group of measurements; the point in a distribution above and below which lie half the values. Mode. The value that occurs most frequently. Normal distribution or normal frequency distribution. The distribution is described by /(*) KW, where y is the mean, a the standard deviation of the distribution, and e is the base of Naperian logarithms. When graphed, the curve of the normal distribution is bell shaped, symmetrical about the mean, and extends infinitely far in both the positive and negative directions. See Dixon and Massey (1957, p. 48-66), Krumbein and Pettijohn (1938, p. 252), Moroney (1956, p. 106-119), and Waugh (1952, p. 155-186). Percentiles. In a particle-size distribution, the 99 points that divide the distribution into 100 segments in such a way that the segments contain equal amounts (by weight) of particles. A given percentile is the value which divides the range of particle sizes into two parts such that a given percentage (by weight) of the particles is coarser than this value. See Waugh (1952, p. 77-78). Probability of significance. Probability that the assumed model is correct; probability that the observed relation could not have occurred by chance. See Ezekiel and Fox (1959, p. 293-298) and Moroney (1956, p. 216-237). Quartiles. The three points that divide a distribution into four equal parts. The 1st and 3d quartiles correspond respectively to the 25th and 75th percentiles. The 2d quartile corresponds to the 50th percentile, or median. See Waugh (1952, p. 75-76). Quartile deviation. A measure of dispersion: one-half the distance between the first and.third quartile. See Krumbein (1936, p. 102-103). Regression coefficient. The coefficient of an independent variable in a regression equation. In simple regression (two variables only), the slope of the regression line. See Dependent variable. See also Ezekiel and Fox (1959, p. 134-140, 147-150) and Fisher (1950, p. 126-136). Regression equation or equation of linear regression. The equation of the straight line used to estimate one variable (the dependent) from one or more other (independent) variables. It is computed by the method of least squares which minimizes the sum of squares of the residuals between the observed values of the dependent variable and the values computed by the regression equation. See Ezekiel and Fox (1959, p. 55-68, 170-187), Moroney (1956, p. 276-320), Waugh (1952, p. 301-316), and Williams (1959, p. 10-52). Residual. The difference between the observed value of a quantity and the value predicted from the regression equation. See Ezekiel and Fox (1959, p. 119-121). Skewness. A measure of the asymmetry of a distribution. See Waugh (1952, p. 200-206). Standard deviation. A measure of dispersion: the square root of the arithmetic mean of the squares of the deviations fromCOMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D37 the mean. For a normal distribution, approximately two-thirds of the samples fall within one standard deviation, plus or minus, of the mean; approximately 95 percent fall within two standard deviations of the mean. See Moroney (1956, p. 61-62) and Waugh (1952, p. 135-147). Standard error of estimate of the dependent variable. A measure of how close the observed values fall to the regression line: The standard deviation of the residuals between the observed values and the corresponding values computed by the regression equation. See Ezekiel and Fox (1959, p. 119-121, 147-150). Variance. A measure of dispersion: the arithmetic mean of the squares of the deviations from the mean. The square of the standard deviation. REFERENCES Aylmore, L. A. G., and Quirk, J. P., 1960, Domain or turbostratic structure of clays: Nature, v. 187, p. 1046-1048. ------1962, The structural status of clay systems, in Swine- ford, Ada, ed., Clays and clay minerals, Volume 9, National conference on clays and clay minerals, 9th, Proceedings: New York, Pergamon Press, p. 104r-130. Barrett, E. P., Joyner, L. G., and Halenda, P. P., 1951, The determination of pore volume and area distributions in porous substances. I. Computations from nitrogen isotherms: Am. Chem. Soc. Jour., v. 73, p. 373-380. Beall, A. 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Kaarsberg, E. A., 1959, Introductory studies of natural and artificial argillaceous aggregates by sound-propagation and X-ray diffraction methods: Jour. Geology, v. 67, p. 447-472. Krumbein, W. C., 1936, The use of quartile measures in describing and comparing sediments : Am Jour. Sci., v. 32, p. 98-111.D38 MECHANICS OF AQUIFER SYSTEMS Krumbein, W. 0., and Pettijohn, F. J., 1938, Manual of sedimentary petrography: New York, Appleton-Century-Crofts, 549 p. McCarthy, D. F., and Leonard, R. J., 1963, Compaction and compression characteristics of micaceous fine sands and silts: Highway Research Rec. 22 ([U.S.] Natl. Acad. Sci.-Natl. Research Council Pub. 1119), p. 23-37. McOulloh, T. H., 1961, Factors controlling subsurface density variations in post-Oligocene sedimentary rocks [abs.]: Geol. Soc. America Spec. Paper 76, p. 112. Martin, R. T., 1965, Quantitative measurements of wet clay fabric [abs.]: North American Clay Minerals Conf., 14th, Berkeley 1965, Program and Abstracts, p. 31. Maxwell, J. C., 1960, Experiments on compaction and cementation of sand, in Griggs, David, and Handin, John, eds., Rock deformation (a symposium) : Geol. Soc. America Mem. 79, p. 105-132. ------ 1964, Influence of depth, temperature, and geolpgic age on porosity of quartzose sandstone: Am. Assoc. Petroleum Geologists Bull., v. 48, p. 697-709. Meade, R. H., 1961a, X-ray diffractometer method for measuring preferred orientation in clays, in Short papers in the geologic and hydrologic sciences: U.S. Geol. Survey Prof. Paper 424-B, p. B273-B276. ------ 1961b, Compaction of montmorillonite-rich sediments in western Fresno County, California, in Short papers in geology and hydrology: U.S. Geol. Survey Prof. Paper 424-D, p. D89-D92. ------ 1963a, Relation of the pore volume of silty sediments to overburden load, particle size, and sorting, in Short papers in geology and hydrology: U.S. Geol. Survey Prof. Paper 450-E, p. E111-E114. ------ 1963b, Factors influencing the pore volume of fine-grained sediments under low-to-moderate overburden loads: Sedi-mentology, v. 2, p. 235-242. ———1964, Removal of water and rearrangement of particles during the compaction of clayey sediments—review: U.S. Geol. Survey Prof. Paper 497-B, p. B1-B23. ------1967, Petrology of sediments underlying areas of land subsidence in central California: U.S. Geol. Survey Prof. Paper 497-C, 83 p. Mitchell, J. K., 1960, The application of colloidal theory to the compressibility of clays, in Parry, R. H. G., ed., Interparticle forces in clay-water-electrolyte systems: Commonwealth Sci. and Indus. Research Organization [Melbourne], p. 2.92-2.97. Modarresi, H. G., and Griffiths, J. C., 1963, Relationship between reservoir properties and petrography of “First Venango Sand”: Pennsylvania State Univ. Mineral Industries Expt. Sta. Circ. 66, p. 251-278. Moroney, M. J., 1956, Facts from figures [3d ed.] : Baltimore, Penguin Books, Inc. 472 p. 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Shepard, F. P., 1954, Nomenclature based on sand-silt-clay ratios: Jour. Sed. Petrology, v. 24, p. 151-158. Sherman, Irving, 1953, Flocculent structure of sediment suspended in Lake Mead: Am. Geophys. Union Trans., v. 34, p. 394406. Shumway, George, 1960, Sound speed and absorption studies of marine sediments by a resonance method: Geophysics, v. 25, p. 451-467, 659-682. Skempton, A. W., 1953, Soil mechanics in relation to geology: Yorkshire Geol. Soc. Proc., v. 29, p. 33-62. Storer, Dionisio, 1959, Costipamento dei sedimenti argillosi nel bacino padano [Compaction of clayey sediments in the Po Valley Basin], in I giacimenti gassiferi del! Europa occi-dentale, v. 2: Rome, Accad. Nazionale dei Lincei, p. 519-536. Taylor, J. M., 1950, Pore-space reduction in sandstones: Am. Assoc. Petroleum Geologists Bull., v. 34, p. 701-716. Terzaghi, Karl, 1925, Principles of soil mechanics: VI. Elastic behavior of sand and clay : Eng. News-Rec., v. 95, p. 987-990. Tourteiot, H. 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E., 1952, Elements of statistical method: New York, McGraw-Hill Book Co., 531 p.COMPACTION OF SEDIMENTS UNDERLYING AREAS OF LAND SUBSIDENCE IN CENTRAL CALIFORNIA D39 Weller, J. M., 1959, Compaction of sediments: Am Assoc. Petroleum Geologists Bull., v. 43, p. 273-310. Williams, E. J., 1959, Regression analysis: New York, John Wiley & Sons, Inc., 214 p. APPENDIX A Samples used in statistical studies The groups of alluvial sediments shown in figures 11 to 15 consist of the following samples. The numbers were assigned by Johnson, Moston, and Morris (1967). Group A: 57 CAL: 8, 11, 27, 37, 40, 57, 62, 76, 78, 79, 81, 82, 84, 85, 90, 108, 113, 115, 136, 139, 142, 152, 155, 162, 176, 177, 186. 58 CAL: 1, 4, 7, 28, 41, 47, 74, 75, 76, 81, 82, 93. Group B: 57 CAL: 7, 29, 31, 50, 64, 65, 83, 121, 130, 149, 154, 166, 168, 169, 174,178,181. 58 CAL: 2,20, 33,42,49, 52,59,65, 72, 73,90. Group C: 57 CAL: 25, 39, 48, 51, 54, 55, 56, 58, 59, 61, 86, 88, 114, 123, 124, 146, 147, 150, 159, 161, 164, 167, 173, 175, 185, 187, 188, 189, 190. 58 CAL: 5,9,10,12,26,31, 50, 53, 64,67,84. Group D: 57 CAL: 9, 10, 12, 13, 14, 52, 107, 109, 111, 112, 131, 135, 137, 148, 151,157,163,165,183. 58 CAL: 23, 30, 32, 38, 46, 48, 51, 57, 60. Group E: 60 CAL: 16, 17, 18, 23, 24, 29, 34, 35, 38, 42, 44, 48, 49, 57, 64, 72, 73, 74, 79, 83, 92, 93, 95. Group F: 58 CAL: 102, 104, 105, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 125, 126, 127, 128, 129, 131, 132, 133, 134, 135, 136, 137, 138, 140, 141. 59 CAL: 350, 351, 352, 353, 354, 355, 356, 357, 361, 362, 363, 364, 365,366,367, 369. APPENDIX B Effective overburden loads at different depths in the cored sections at time of coring [Computed by R. E. Miller (Mendota, Cantua Creek, and Huron), B. E. Lofgren (Pixley and Richgrove), and J. H. Green (Sunnyvale and San Jose)] Depth below land surface (feet) Effective overburden load (psi) (kg per cm*) Mendota 1957 120 104 7.3 625 308 21. 6 700 475 33. 4 1, 500 832 58. 5 Effective overburden loads at different depths in the cored sections at time of coring—Continued Depth below land Effective overburden load surface (feet) (psi) (kg per cm*) Cantua Creek 1958 192 170 12. 0 565 305 21. 4 575 475 33. 4 1, 720 970 68. 2 2, 000 1, 090 76. 6 Huron 1957 120 105 7. 4 730 305 21. 4 747 540 38. 0 1, 640 915 64. 3 2, 200 1, 155 81. 2 Pixley 1958 120 86 6. 0 285 165 11. 6 296 213 15. 0 760 413 29. 0 Richgrove 1959 1 180 135 9. 5 533 306 21. 5 744 400 28. 1 1, 053 524 36. 8 1, 175 568 39. 9 1, 205 578 40. 6 1, 377 629 44. 2 1, 384 634 44. 6 1, 743 760 53. 4 1, 818 790 55. 5 1, 900 819 57. 6 2, 200 950 66. 8 Sunnyvale 1960 150 64 4. 5 185 130 9. 1 215 144 10. 1 415 235 16. 5 680 360 25. 3 1, 000 503 35. 4 San Jose 1960 137 120 8. 4 245 166 11. 7 475 270 19. 0 785 418 29. 4 815 432 30. 4 865 449 31. 6 895 464 32. 6 930 481 33. 8 1, 000 513 36. 1 1 Pore pressures in finegrained beds in 1959 were assumed equivalent to water-level conditions of 1921. This assumption probably is reasonable for pressures in the recently tapped (1946-H), slow draining, thick marine siltstone beds between depths of 744-1,900 feet. However, computed effective loads between depths of 180-744 feet in the alluvial deposits may be as much as 15 percent low. U.S. GOVERNMENT PRINTING OrFICE : I9«8 0-280-804