| UC BERKELEY MASTER NEGATIVE STORAGE NUMBER 03-67.23 (National version of master negative storage number: CU SNO03067.23) MICROFILMED 2003 UNIVERSITY OF CALIFORNIA AT BERKELEY LIBRARY PHOTOGRAPHIC SERVICE REPRODUCTION AVAILABLE THROUGH INTERLIBRARY LOAN OFFICE MAIN LIBRARY UNIVERSITY OF CALIFORNIA BERKELEY, CA 94720-6000 COPYRIGHT The copyright law of the United States (Title 17, United States Code) governs the making of photocopies or other reproductions of copyrighted materials including foreign works under certain conditions. In addition, the United States extends protection to foreign works by means of various international conventions, bilateral agreements, and proclamations. Under certain conditions specified in the law, libraries and archives are authorized to furnish a photocopy or other reproduction. ‘One of these specified conditions is that the photocopy or reproduction is not to be "used for any purpose other than private study, scholarship, or research." If a user makes a request for, or later uses, a photocopy or reproduction for purposes in excess of "fair use," that user may be liable for copyright infringement. University of California at Berkeley reserves the right to refuse to accept a copying order if, in its judgment, fulfilment of the order would involve violation of copyright law. Erskine, N. M. The structure and stratigraphy of an area on upper San Pablo Creek in Contra Costa County 1924 BIBLIOGRAPHIC RECORD TARGET University of California at Berkeley Library Master negative storage number: 03-67.23 (national version of the master negative storage number: CU SN03067.23) GLADIS NUMBER: 184783311C FORMAT : BK AD:991004/FzB LEVEL:b BLT:am DCF:a CSC:d MOD: EL:7 UD: 030604 /MAP CP:cau L:eng INT: GPC: BIO: FIC: CON: ARCV: PC:s PD:1924/ REP: CPI: FSI: JC: 11:0 CUScCU 040 090 100 245 260 300 502 504 610 690 20 0 SbDISS.ERSKINE.GEOL 1924 Erskine, N. M. The structure and stratigraphy of an area on upper San Pablo Creek in Contra Costa County /$cby N.M. Erskine. $cl1924. 18 leaves :$bill., map ;$c29 cm. Thesis (B.S. Geology) --University of California, Berkeley, April, 1924. Includes bibliographical references. University of California, Berkeley.S$SbDept. of Geology and Geophysics$xDissertations. Dissertations, AcademicS$SxUCBS$SxGeologySy1921-1930 Microfilmed by University of California Library Photographic Service, Berkeley, CA Diss RRR La ERS KITA en Geol Structure and Stratigraphy of an Area on Upper /72H » : 2 San Pablo Creek in Contra Costa County. EAT fillment of the Thesis Require- t for the degree of Bachelor of Science in the ollege of Mining, Department of Geology, University Submitted April 26, Table of Contents INTRODUCTION ' Page Location and Extent of the Arefles sessceccccecess 1 Acknowledgement Becececsecccsescsccssnscsscscsccvcccse i Nature of the Problem and Field MethOQe:esseeee 2 TOPOGRAPHY. Relief. $00 cess 0200000000000 0000000800000800 Drainage. © 9 60 OO POP OOO POOP GOSS 0 00000 0D esse Culture and AccessibDilitye ecscercrocscncnnse Bd WO Vegetation. © 9 OO BOO OOO OPO OPO ODEON OOOH PYSETSDS GEOLOGY General Statement sececeesssssssssecsssssscnces Stratigraphy ssceesssecsoccssssssssscssscscesence Briones ecsssescessscscsssssssssessssessose Orindan SS FS 0 FO PP OHI P OES CBOE EEN Oy OF I» ib Morags Series eccesesesesssssosocsnssscnss Igneous Rocks General description esscessscssessseccsses 6 Petrographic Description esseessccccceses 8 CONCLUSIONS eececsssscesssssssssssscsscss 12 Sedimentary Rocks. © 09 008039 0805000000000 030000008 13 STRUCTURE © 8 8S 8:0 PPS SP SVB PSPSPS NLIEDOILISLSTPISS 15 HISTORICAL GEOLOGY 00 0 00 SPP SITIOS OOPOLNNIEEPIRRIESIAS 16 ECONOMIC ASPECTS. © 0 9S 0 8S SESE BIDEN SILER ILOEN SS 17 A paneramic view showing San Pablo Valley. A INTRODUCTION TOCATION AND EXTENT OF THE AREA. This report describes the geology of an area three miles square in San Pablo Valley, to the northeast of Rureka Peak in Contra Costa County. The southwestern limit of the map 1s ap~- proximately parallel to San Pablo Ridge which has an approximate trend of S. 45° E from Eureka Peak and which is roughly parallel to the strike of the region. ACKNOWLEDGMENTS » This region has been previously mapped on a small scale with little reference to detail by A. Ce. LAWSON (S. Fe Folio No. 193). The age relations of the different formations were obtained from this folio. Mapping work was done in conjunction with Mr. He. Be Lloyd, who also worked out a thesis in this area. Much credit and appreciation must be expressed to Dr. R. Re. liorse who has offered many valuable sugges=- tions and aided in the progress of the works NATURE OF PROBLEM AND FIELD METHODS. The original intent was to map the area in | detail and make petrogrphic determinations of the prin- ll cipal rock types encountered. £) Considerable difficulty was encountered in doing detailed BAPE of the area due in part to the inexperience of the author and to the difficulty in locating contacts which in many places aris covered by detrital material or a heavy mantle of vegetation. The purpose of undertaking the problem was chiefly to gain experience in geologic field work and incidentally to fulfill the thesis requirement for the degree of Bachelor of Science. | The map used was an enlargement of the U. S. G. S. map of the area. The topography on the map was found to be very inaccurate so it became necessary, in order to accurately locate one's self on the map, to locate conspicious cultural features such as towers, houses, etc. This was done by running Brunton compass and pace traverses along the state Highway, tieing in the cultural features to the traverse. Twenty seven days were spent in the field six days of which were employed solely for reconaissance work. The remainder being devoted to areal mapping. All points were located by means of intersection, using the Brunto Compass, with two or more cultural features. § 1 | | San (aw Lid 7c A panoramic view | ooking westward showing Tee RETAKE OF PRECEDING FRAME 3 &y g " . badly 1d. ; bb i po. Rh the development of step like topography below San Pablo Ridge. A panoramic view looking westward showing A TOPOGRAPHY RELIEF . The most conspicious feature of the area is San Pablo Ridge which at its highest point (Eureka Peak) attains an altitude of 1625 feet. To the north of San Pablo Creek, in this area, the highest elevation is around 900 feet. The contrast is due no doubt to the presence of the lavas which top San Pablo Ridge. On the south side of San Pablo Creek a sort of step like topography has been developed. The lava flows fppm the edges of the steps while the lentils of gravel and sandstone form the flat portions. Landsliding is particularly noticeable in the Orindan on the south side of San Pablo Creek in the Orindan and to a lesser extent in the intervolcanic gravels. DRAINAGE. The drainage in this area is to the west. The streams on both sides of San Pablo Creek are roughly at right angles to the trend of the ridges and form a trellace drainage pattern. These streams carry water only during the wet season but due to the steep slope and nature of the underlying rocks, JOSSEess great erosive power on south side of San Pablo Creek. On the north atest mtn idl am A side of San Pablo Creek the greater porosity of the underlying rocks causes a large portion of the rain~ fall to be absorbed. CULTURE AND ACCESSIBILITY. | A state highway extends through San Pablo | Valley. Roads have been constructed on both side of | the Valley. Water has been developed by the Orinda | Development Company for the purpose of promoting real : estate sales. | The area is readily accessible being but six miles over trails from the University Campus and twelve miles by paved highway from the City of Oaklend. VEGETATION. Vegetation is rather sparse along the slopes of San Pablo Ridge and on the hills to the north, being concentrated in the stream cut valleys. Oaks, scrub oaks, poison oak, and underbrush form most of the vege- tation. The barren spaces are grass covered giving the land some value for cattle grazing. GEOLOGY GENERAL STATEMENT In this area described there is a variety of rock types encountered, both sedimentary and igneous. The geologic history of the region is quite varied including varying conditions of deposition, erosion, volcanic activity, and diastrophism. The general geologic structure of the region is somewhat similar to that of the Berkeley Hills although not of the same magnitude. Folding and faulting are common features. In rauterwaser Creek near the north western limits of the map the Briones sandstone was encountered. The Orindan conglomerates overlie the eroded surface of this formation. The Moraga Series overlies the Orindan conformably. In order that the reader maybe aided in keep~- ing the age sequence in mind the following teble is in- serted. (Moraga Series (andesites, basalts, inter- ( calated gravels, and Pliocene ( sandstones) ( (Orindan (sandstones, shales, clays, ( and conglomerates) | |} Upper Miocene (Briones (Hard grayish quartzose | ( sandstone) | STRATIGRAPHY. \ BRIONES The Briones sandstone occurs in the extreme northwestern portion of the area. This formation under- 1ies the urindan unconformably, the Orindan resting on the eroded edges of the Briones. In Lauterwaser Creek, the only place where the Briones was observed, the Briones consisted of a very hard, greyish quartzose | sandstone containing small grayish brown inclusions of shale. Because of the limited occurrence of the Briones in this area it will receive no further mention. ORINDAN This formation outcrops over the greater portion of the area and is composed of sandstones, con- glomerates, gr:vels, shales, clays, and tuffs. The orindan is overlain by the loraga series with apparent conformity. MORAGA SERIES The Moraga Series consists chiefly of lava flows with intercalated gravels and sandstones with lignite and occasional lenses of limestone. The division of the Pliocene series into Orindan and Moraga Series seems to be one of convenience as nowhere are the gravels of the Moraga and the sediments of the Orindan in contact except in the case of fault con- tacts. Evidence as to the age of the Moraga and Orindan was obtained from the fluviatile deposits of the Moraga in the finding of two horses teeth. These were 1dentified by Doctor Chester Stock of the Paleontology Department as teeth of Hipparion speciosum of Pliocene age having affinities with the Miocene. IGNEOUS ROCKS GENERAL DESCRIPTION There are apparently eight distinct flows in the area. The uppermost flow extends along the top and sides of San Pablo Ridge. Immediately underlying this first flow is the second flow. These two flows may be differentiated in the field on the basis of their textural differences. In the region to the north of the locality where San Pablo Ridge changes its east-west trend to that of a north-south one it is possible to distinguish six other separate flows. A thin section was made from each of these flows from specimens collected in this region. The first and second flows are separated from the third flow by sandstones and conglomerates varying from four hundred to five hundred feet in thickness. The third flow is immediately underlain by a layer of rhyolitic agglomerate (2?) which is approximately twenty feet thick. The occurrence of the agglomerate 1s rather restricted in this area extending from the base of San Pablo Ridge in the above described locality about a quarter of a mile to the west where it pinches out or is covered by detrital material. Between the agglomerate and the fourth flow is a layer of gravel and sandstone about 150 feet thick. The fourth and fifth flows are separated by approximately three feet of intervolcanic gravels. The remaining flows are each sep- arated by about two hundred feet of gravels and sandstones. In this section the lavas vary from twenty to fifty feet in thickness and thicken to the westward. CE CR Tony PLATE I. exhibited in the Fluxional arrangement of the feldspars as uppermost flow. RETAKE OF PRECEDING FRAME PLATE I. In the field flow structure is apparent in some of the lavas although in not all of them is it observable. All of the flows are amygdaloidal - the amygdules being composed of quartz, chalcedony, and calcite varying in size from microscopic dimensions to larger than a hen's egg. PETROGRAPHIC DESCRIPTION OF LAVA. The following is a description of the thin sections made from the previously described flows. The slides are numbered consecutively from San Pablo Ridge northward. Number 1. (Olivine Basalt) The texture has a tendancy to be porphyritic with phenocrysts or olivine. The feldspars have fluxional arrangement inclosing angular particles of isotropic glass in minor proportions giving a texture similar to what Harker describer as the intersertal texture. See: plate #1. The essential minerals consist of labradorite and bytownite (extinction angles of 35 and 50 degrees by stastical method.) Olivine is the characterising accessory which occurs in relatively large sized apparently once euhedral crystals, although their original outline 1s some- what masked due to chloritization that has taken place. 7ircon occurs rather sparingly. Magnetite (or illmenite) occurs abundantly as xenomorphic erystals desséminated throughout the section. PLATE 2. X-NICOLS., Porphyritic texture of the second flow showing phenocryst of oligoclase, PLATE 3A. X-NICOLS. J derable amounts of J) devritified glass enclosed between lath shaped feldspars. RB ATR AR ATO dB AN —— A ls Nl lO Tl. i. dtl A. BAA. AE a -. COLS, NT X Gy oS ~i > - - 0 fa : ~ a A A, © 0 . ©. ‘COLS., “NT O a3 >< co O 0 -~— 1! < } £5 . i +2 -< w ¢ oo rl PLATE ¢ -3 - \ O ro! 0 w 1 oO 3 orf — — ~ © 0 EH < O CO ™ 0 oO A — Cy to Oo 4 oO { ori > ha ~~ 0 vritif J de wi A partial devitrification of the glass of the ground mass has taken place giving a radiating texture which has an undulatory extinction. Number 2. (Augite - Andesite) This lava is distinctly porphyriEi naving as phenberysts oligoclase, andesine, labradorite, and augite. Many of the feldspar phenocrysts show a marked zonal growth. See plate #2 o The ground mass consists simply twinned crystals of oligoclase and andesine with a residium of glassy matter which is characteristic of the 'andesitic' groundmass. Isotropic glass also occurs both as inclusions in the feld- . spar phenocrysts and interstacially. | The chief accessory mineral is xenomorphic magnetite or illmenite which is quite abundant. Zircon is sparingly present. Number 3. (Augite - Andesite.) The texture is porphyritic with the chief phenocrysts consisting of andesine, labradorite, and augite. The groundmass is composed of isotropic glass and what appears to be devitrified glass. See plates 3 A and B. That portion considered as devitrified glass has what might be termed a pseudo~-crystalline -ap- pearance and under crossed nicols appears as if a shade or net had been superimposed over a crystalline aggregate. Microspherules are quite common although not sufficiently PLATE 3B. High magnification of a portion of 3A showing the devritified glass, PLATE 4, X-NICOLS. - Fourth flow, Feldspar microlites enclosing angular patches of isotropic glass illustrating the intersertal texture, RECEDING FRAME [> High magnification of a portion showing the devritified glass, PLATE 4, X-NICOLS. 1 Fourth flow. Feldspar microlites enclosing Oo angular patches of isotropic glass illustrating the intersertal texture, ws "RETAKE OF PRECEDING FRAME JA m a fH ~ ” ws - Ww —- eS Nd - - “ - 1 ™ LLAr avenes Cc - 1 i , w vd dO LA ade € "J LLLUSLr L 4 —- - rt ~ 10. abundant to give a microspherulitic texture to the groundmasse The essential minerals present are hypautomorphic lath shaped crystals andesine and labradorite. -Augite, the characterising accessory, occurs rather abundantly as hypautomorphic grains being in a few instances euhedral in outline. The augite in all of the thin sections exaimined is of the non-pleocroic variety. Zircon and magnetite (or illmenite) make up the accessory minerals. Zircon eccurs sparingly as idiomorphic barrel shaped crystals. Magnetite oceurs abundantly as evenly dessiminated xenomorphic grains throughout the section. Very little alteration has taken place. Number 4. (Augite - Andesite) Texture porphyritic with rounded and irregular shaped grains of augite making up the phenocrysts. The groundmass consists of singly twinned feldspar microlites enclosing angular patches of isotropic glassy material giving what is termed by Harker as the intersertal structure. See plate 4. Extinction angles measured in the zone of (010) : (00I) show the presence oligoclase, andesine, and labradorite as the essential minerals. Augite is the characterising accessorye. PLATE 5, X-NICOLS., Sixth flow. Plate illustirtes the nearly holocrystalline texture of this flow. AINAY A AAACN AER YY JA A ANAUN AJA AL NT A AN ALVA RJ PLATE 5, X-NIGOLS, The accessory minerals magnetite and zircon, the former occurring abundantly as small xenomorphic grains and shaped the latter occurring as occasional automorphic barrel, crystals. Number 5. (Augite - Andesite). Texture porphyritic with phenocrysts of albite SL LodL ate, and andesine, and augite. The groundmass is made up essentially of small hypautomorphic feldspar laths which are of the same composi- tion as the phenocrysts and angular isotropic glass which is enclosed by the feldspar lathse. Most of the augite has altered to chlorite. Zircon is sparingly present, Magnetite occurs abundantly dessiminated throughout the section. Number 6. (Olivine - Augite Andesite) Texture pdphrytic with phenocrysts of oligoclase, andesine, and olivine. The groundmass which makes up about 25% of the slide, consists chiefly of small lath shaped feldspars of the same composition as the phenocrysts along with a few grains of augite and minor amounts of isotropic glass. See plate #5. 7ircon and i%lmenite or magnetite are present as accessories. Magnetite or illmenite is rather abundant as in the previous sections. The augite is found in many places altering to chlorite. a AE RE Number 7. (Andesite.) Texture porphyritic with phenocrysts of andesine and labradorite. The groundmass is composed of small lath shaped feldspars (andesine and labradorite) and considerable amounts of isotropic glass. The texture resembles that described by Harker as the hyalopilitic texture. The accessories consist of zircon and abundant magnetite. Calcite occurs abundantly as a secondary con- stituent. In places it has apparently replaced the feldspars while in places it has no definite outline. Chlorite is present. Number 8. (Olivine Basalt.) Texture porpliyritic with occasional phenocrysts of olivine and labradorite. The groundmass consists of small laths of labradorite and a residium of glassy material. The accessories consist of zircon and magnetite, the latter being abundant as in the previous sections. Chlorite is developing around the boundaries of and in the cracks of the olivine. CONCLUSIONS The examination of the sections brings out the following facts: 1. The mineral constituents both the essestials and the accessorries are nearly constant in six of the eight flows. 2. The separation of the flows microscopically is for the most part dependent upon textural differences rather then in variability of the mineralogical constituents. SEDIMENTARY ROCKS:- The sediments of this area are of fluviatile and lacustrine origin. Fossil content of some of the sediments indicate a lacustrine origin while the heterogeneity of some of the accumulations indicates clearly a fluviatile origin. The sedimentary rocks in the area consist chiefly of lacustrine and fluviatile sandstones and conglomerates. Lignite occurs in limited quantities as thin seams that rapidly lense out. Clays shales and tuffs are rether common. Limestone occurs in lenses between some of the lava flows. The prevailing type of sandstone in the Moraga Series is a fairly well indurated gray greywacke sandstone. In the orindan the most common type is a buff colored, poorly indurated, medium grained, argillaceous sandstone, containing an iron oxide rement. It 1s a well sorted sand- stone. Occasional sandstones of an arkosic nature are en- countered in the Orindan. The conglomerates of fluviatile origin occur chiefly in the Moraga Series and are very heterogeneous consisting of sands, reworked conglomerate, and lave fragments. The lava fragments in the conglomerate are angular and range in size up to two or more feet in their long dimension. It was in such a fluviatile accumulation that the horse's teeth were found. The conglomerates of lacustrine origin in the Moraga consist chiefly of lava and cherty pebbles up to an inch or two in diameter in a matrix of fine gravelly material. The conglomerates of the Orindan are almost entirely of a lacustrine origin and consist of pebbles varying in size from an inch to six inches in diameter em- bedded in a rather fine matrix. The occurrence of thin beds of lignite was noted in a number of places. Nowhere does it appear to be very persistent but lenses out rapidly. Clays and shales occur rather widespread through out the area but in much greater thickness in the Orindan. Clay occurs as a thin bed about 150 feet below the top of San Pablo Ridge. The contact with the sandstone above and the conglomerate below is marked in a number of places by water seepages as the clay is very impervious. Two wells have been driven in the north side of Bureka Peak for the purpose of obtaining water from the sandstone above the clay member. These wells produced only a slight amount of water. In the Orindan some of the clays attain quite a thickness. Distinctly banded shales occur near the top of the Orindan. These shales show alternate light and dark colored band which are probably due to slight seasonal variations. Thin beds of fine tuff occur at intervals through- out both the Morage and Orindan. A rhyolite agglomerate(?) occurs in the Morags. Series near the base of San Pablo Ridge which apparently has an equivalent along Skyline Hidge. Further reference to this deposit has been made under the heading of Igneous Rocks. Iimestone lenses occur between some of the 1ava flows. An individual lense varies from one to forty feet in width. Although one limestone member is rather per- sistent laterally the limestone is of little value for commercial purposes. Some of the beds contain abundance of fresh water ostracods. STRUCTURE The general structure of the region is that of a series of minor folds. The west end of San Pablo Ridge is the northern 1imb of the Berkeley Hills syncline. Along the north side of Fureka Peak the beds dip about 45° south. Traveling northward from Eureka Peak towards San Pablo Valley one encounters Morage, Orindan, and Moraga. Within a thousand feet the dip has been reversed. The sequence of the formations and the change 1n dip indicate the presence of an anticline. tvavorges. Up Lauterwaser Creek and the Creek opposite the Tunnel Koad, in the region north of this anti- cline prove the existence of a smaller anticline with an average trend of north 60° west. The presence of this fold 1s evident only from the observations of the exposures in the creek beds, as the alluvium covers the rocks over most of the intervening area. A panoramic view looking northward from San Fablo Ridge. RETAKE OF PRECEDING FRAME | A panoramic view looking northward from San Pablo Ridge. “«» RETAKE OF PRECEDING FRAME | A panoramic view looking northward from San Pablo Ridge, Faulting is a common feature throughout the area. Many of the Faults ave of but slight displacement and are not shown on the map. The Pinole Fault, which has been excellently described by Professor Iawson runs across the western border of the area. Two cross faults with a throw of a few hundred feed have been indicated on the map. A small fault scarp is still visible on the one to the east. The fault to the west is quite ovious when one observes the displacement of the Limestone member. It was possible to trace these two faults but a short distance. Land sliding 1s quite a common feature in the Orindan to the south of San Pablo Creek and in the Morage sediments. This feature is not so pronounced on the north side of San Pablo Creek. lhe folding that has developed the anticlinal structure has weakened the competent lava beds and has greatly aided in the erosion of these members. This erosion has in places uncovered the underlying Orindan particularly in the region to the north of Eureka Peak. HISTORICAL GEOLOGY. Considerable information relative to the geologic history of the region may be drawn from the field evidence. Moraga and Orindan times were marked by great igneous activity. The tuff beds of both the Orindan and Moraga are well sorted. They are very fine, a feature which 17. may indicate transportation by wind over considerable distance. The presence of limestone beds between the lava flows indicate that time must have elapsed between periods of igneous activity. That the limestone accumulated in a lake basin is indicated by the fossil content. The final events in the history of the region were folding and faulting. The folding has greatly weakened the competent lava beds and greatly assisted the agents of erosion. The most recent event in the history of the region is rejuvenation of the drainage indicated by the rather steep sided stream trench which San Pablo Creek has cut into the alluvium. The rejuvenation of the drainage might be brought either by climatic change where in the amount of water carried by the stream was greater or by a change of base level due to slight regional uplift. ECONOMIC ASPECTS: - Deposits of economic importance include water, clay, and gravel. Limestone is of questionable economic importance. Due to its lense like occurrence it seems doubtful that there is a sufficient quantity of limestone to be worked commercially. As the writer has not analyzed the limestone for its magnesium content he is not in a position to corment on its possibilities for cement mak= ing. Should the limestone prove to be of the proper chemical composition for cement making exploration by means of drilling to prove the thickness of the deposit should be conducted before any equipment to mine the limestone is obtained. Lignite occurs in thin seams which lense out rapidly and is therefore of no importance as an economic deposit. Several water wells have been drilled in the region of Lauterwaser Creek and may be of sufficient im- portance to supply the future needs of the town of Orinda. Clay exists in workable quantities in the Orindan and is exposed in Tauterwaser Creek. Gravels are quite abundant and of the character that may be used in making concrete. LEGEND Moraga Series [1 Andesitic and basaltic flows. Pliocene E] Undifferentiated lavas and intercalated gravels. Limestone lentils, Orindan [] Sandstones , conglomerates, clays, and shales. Miocene { ones Hard greyish rt [J acd grnfish quarizose © 3 North Re. ee ervasser = Section A-B Jo’ ”, - {= 7250’ -l é Vert Horiz Lake Orinda «Natural Segle ~ North Section E-F MAPPED BY LLOYD &ERSKINE Scale 1“=750 feet. Section C-D | RETAKE OF PRECEDING FRAME LEGEND Moraga Series [1] Andesitic and basaltic flows. Pliocene [] Undifferentiated lavas and intercalated gravels. Limestone lentils, Orindan [] Sandstones , conglomerates, clays, and shalés. Miccene Briones rd ish [1 {ord Fh quarizose Tank Sprin 5 z — b. ote” Se raat | SeTervasser Section A-B "= 250" Vert 1-30’ Lake Orinda Rood White House ! cut og NS. barn 2s «Natural Seale North | Sealevel Section FE - F MAPPED BY LLOYD &ERSKINE Scale 1“ =750 feet. Section C-D [mera | 4 (ITT gl Ta Ts Tel 7 Te] 2 'al 'a] 's| '6] '7| '8 VERVE TT FR TTT EN Ey i 9 "1011712 13'141% | - i | - ? 9 tll td Zain 7 LEGEND Moraga Series Pliocene [] Andesitic and basaltic flows. [Undifferentiated lavas and Cl intercalated gravels. Limestone lentils. Orindan Sandstones , conglomerates, clays, and shalés. [] Miccene {Briones -1=50’ "= 250" Vert «Scale Section E-F [5rd stopyion quartzose 7 North Section A-B «Natural Seale ~ North | Sealevel Section C-D | RETAKE OF PRECEDING FRAME | { { | Willow Spring 1 lrolp Spring Tunnel du : Tunnel well : 7 Lake Orinda A \ . 4 / \\ . / { ’ ” / AN « { / | PA " . i We W { . 7 . N / \ / oe’ \ ’ \ / p / \ 2 y NS | o x NE | 0 . N\ | \ " y . A | . . J | r \ | \ Na — | . | . \. ~— | i. ap A 1 \ y, ¢ AA ADDI T mY | at : MAPPED BY | us ™ Tw AN OYD&ERSKINL Scale 1“=750 feet Ii Lally — — a ————. — ———————————————_————] fT a er TTT £1] 2] 3] ‘3! 5 6) '70 '8s] '9] "1011'12'13'1415 : > til Satta Zeta Stet Estunsl Sansa tasbisban usa y 5 | RETAKE OF PRECEDING FRAME LEGEND Moraga Series Andesitic and basaltic flows. Pliocene Undifferentiated lavas and intercalated gra vels. Limestone lentils, Orindan [] Sandstones , conglomerates, clays, and shalés. Hard greyish rt C0 tg gon src ] North Section A-8 Jo’ - ("= 750" l= o Vert Horiz £2 Oo |v] vs) } t 3 3 — 5 & 3 35; v 8 i 4 “le 9 a 5 Q 3 1 0 o c Q 3S 0 1p] e (HEHE EE 1 mi , wid 2) "al al sl el 170 '8l le 10 11712 131415 td Sante BE Eats Zee Ga tanaka leat n ay END OF TITLE Sh SR Sa