Geol<)gy of the Compacting Deposits in the Los Banos­ Kettleman City Subsidence Area, California

GEOLOGICAL SURVEY PROFESSIONAL PAPER 497-E

Geology of the Compacting Deposits in the Los Banos­ Kettleman City Subsidence Area, California By R. E. MILLER, J. H. GREEN, and G. H. DAVIS

MECHANICS OF AQUIFER SYSTEMS

GEOLOGICAL SURVEY PROFESSIONAL PAPER 497-E

Geology of the deposits undergoing compaction due to head decline, including source, type, physical character, and ?node of deposition, and the hydrologic framework so developed

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTO~ : 1971 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY William T. Pecora, Director

Library of Congress catalog-card No. 7o-610408

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS

Page Geology-Continued Abstract ______E1 Geology of the tributary drainage area, etc.-Con. Page Introducuon ______1 Upper Tertiary and Quaternary deposits undif- Previous investigations ______4 ferentiated ______E13 Purpose of investigation and scope of report ______4 Stratigraphy of the water-bearing deposits ______13 Electric-log interpretation ______5 Jacalitos Formation (Pliocene) ______14 Acknowledgments ______8 Etchegoin Formation (Pliocene) ______16 Well-numbering system ______8 San Joaquin Formation (Pliocene) ______Geology ______20 8 Tulare Formation (Pliocene and Pleistocene) __ _ 21 Geologic history and structure ______8 Terrace deposits (Pleistocene) ______33 Geology of the tributary drainage area, Diablo Range_ 9 Alluvium (Pleistocene and Holocene) ______33 Soils ______Jurassic and Cretaceous rocks ______9 33 Franciscan Formation ______10 Hydrologic units in the ground-water reservoir ______34 Ultramafic intrusive rocks ______10 Upper water-bearing zone ______35 Cretaceous sedimentary rocks ______10 Lower water-bearing zone ______35 Lower Cretaceous sedimentary rocks ______10 Chemical character of the ground water ______38 Upper Cretaceous sedimentary rocks ______10 Waters of the upper water-bearing zone ______38 Significance of Mesozoic rocks ______11 Stream waters ______- __ 39 Lower Tertiary sedimentary rocks ______11 Waters of the lower water-bearing zone ______39 Paleocene and Eocene marine sedimentary Saline water body ______---_- __ - __ ---- __ rocks ______40 12 References cited_- ____ - __ - __ -_--_------41 Index ______Miocene deposits ______12 45

ILLUSTRATIONS

[Plates are in pocket) PLATE 1. Geologic map of the late Cenozoic deposits of the west border of the San Joaquin Valley in the LosBanos-Kettlemen City area, California. 2. Generalized geologic map of the Diablo Range tributary to the Los Banos-Kettleman City area, California. 3. Geologic section A-A' from near Los Banos southeast toward Tulare Lake bed, Los Banos-Kettleman City area, California. 4. Geologic sections B-B' to E-E', Los Banos-Kettleman City area, California. 5. Composite logs of selected core holes, Los Banos-Kettleman City area, California. Page FIGURE 1. Index map of central California showing location of report area ______E2 2. Map showing land subsidence, 1922-32 to 1959 ______---- __ ------3 3. Location map of geologic sections and core holes ______6 4. Typical electric log with interpretations ______- ____ - _------8 5-7. Sections of strata in the: 5. Jacalitos Formation ______------15. 6. EtchegoinFormation______18 7. Tulare Formation ______- ____ ·-_------22 8. Map showing thickness of alluvial-fan deposits derived from the Diablo Range in the Tulare Formation below the Corcoran Clay Member------26 9. Map showing thickness of alluvial-fan deposits derived from the Diablo Range above the Corcoran Clay Member of the Tulare Formation ______------27 10. Map showing thickness of micaceous sand overlying the Corcoran Clay Member of the Tulare Formation_-- 29 11. Map showing thickness of the Corcoran Clay Member of the Tulare Formation ___ - __ -_------31 12. Map showing structure of the Corcoran Clay Member of the Tulare Formation ______32 13-15. Generalized sections: 13. A-A', showing hydrologic units ______--- _____ ------35 14. B-B', C-C', and E-E' showing hydrologic units------36 15. B-B', C-C', and E-E' showing yield factors of wells in relation to the depositional environment__ 37 m IV CONTENTS TABLES

Page TABLE 1. Core holes in or near the Los Banos-Kettleman City area ______E7 2. Generalized geologic units of the drainage area tributary to the Los Banos-Kettleman City area ______10 3. Areas of generalized geologic units within stream basins ______11 MECHANICS OF AQUIFER SYSTEMS

GEOLOGY OF THE COMPACTING DEPOSITS IN THE LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA

By R. E. MILLER, J. H. GREEN, and G. H. DAvis

ABSTRACT deltaic, and lacustrine deposits and are identified as to source area-Sierra Nevada or Diablo Range. The one persistent map­ The Los Banos-Kettleman City area includes 1,500 square pable subsurface stratigraphic unit is the Corcoran Clay Mem­ miles on the central west side CJf the San Joaquin Valley, Calif., ber of the Tulare Formation, a diatomaceous lacustrine clay chiefly in western Fresno County. It is an agricultural area, ir­ 0--120 feet thick that underlies most of the project area and rigated chiefly by ground water. Intensive pumping has lowered is the principal confining bed. the artesian head several hundred feet and has caused the Deposits derived from the Sierra Nevada extend far west of water-bearing deposits to compact. By 1959 the resulting re­ the modern axis of the San Joaquin Valley. The axis of the gional subsidence of the land surface exceeded 4 feet in most valley shifted laterally in Tulare time, in response to tectonic of the area and locally attained 20 feet. Superimposed on this uplift in the mountains, warping in the valley, and climatic regional subsidence was as much as 10-15 feet of localized sub­ changes, which determined the relative proportion of sediments sidence due to hydrocompaction of moisture-deficient near-sur­ being contributed from the east and west. In pre-Corcoran time, face deposits, which affected at least 80 square miles. This is Sierra flood-plain deposits extended a maximum of 13-17 miles the largest known area of intensive land subsddence due to with­ west of the modern topographic axis; immediately after deposi­ drawal of ground water. Therefore, the geology of the com­ tion of the Corcoran-about 600,000 years ago-Sierra mica­ pacting deposits, including source, type, physical character, and ceous sands extended as much as 13 miles west. Subsequently, thickness, is of primary interest in appraising the response of the axis gradually moved east to its modern position. the sediments to change in effective stress. In general, the deposits from the Sierra Nevada, which are The fresh-water-bearing deposits of late Pliocene to Holocene mostly flood-plain deposits, are coarser, better sorted, and more age forming the ground-water reservoir in the Los Banos-Ket­ permeable than those from the Diablo Range, which are mostly tleman City area have been derived from both the Diablo alluvial-fan deposits. The depositional history and the character Range to the west and the Sierra Nevada to the east.1 Rocks of the deposits are primary factors in determining areal varia­ exposed in the tributary drainage area in the Diablo Range, tion in permeability and compaction characteristics of the which range in age from Jurassic to Pleistocene, shown on a water-bearing sediments in the Los Banos-Kettleman City area. generalized geologic map, are chiefly sandstone and mudstone. The continental fresh-water-bearing deposits can be subdi­ Unconsolidated to semiconsolidated sediments of continental, vided into two principal hydrologic units. The upper unit, termed and, locally, of marine origin, which crop out along a relatively the "upper water-bearing zone," extends from the land sur­ continuous strip 1-6 miles wide bordering the western flank face to the top of the Corcoran Clay Member at a depth ranging of the subsiding area, were mapped for this report. They include from 20 to 900 feet below the land surface. The lower unit is the Jacalitos, Etchegoin, and San Joaquin Formations of Plio­ referred to as the "lower water-bearing zone." It is 600 to more cene age and the Tulare Formation of Pliocene and Pleistocene than 2,000 feet thick and extends from the base of the Corcoran age. Clay Member down to the deposits containing the main saline The principal aquifers occur within the alluvial and lacustrine water body. deposits of the Tulare Formation, which underlies all of the The chemical character of the ground water changes markedly Los Banos-Kettleman City area .and ranges in subsurface with depth. The major changes with depth are a marked thickness from a few hundred to more than 3,000 feet. The decrease in dissolved solids and an increase in the percent of underlying formations of Pliocene age contain brackish or saline sodium among the cations. water, except in the central southwestern part of the area where fresh water occurs in the San Joaquin and Etchegoin INTRODUCTION Formations. The Los Banos-Kettleman City area of California, In a series of subsurface maps and sections based on electric as referred to in this report, is that part of the west side logs and core records, the Tulare Formation and overlying of the San Joaquin Valley extending from Los Banos younger deposits are subdivided into alluvial-fan, flood-plain, in Merced County, through western Fresno County, to 1 Principal source of deposits, where identified, is indicated as Diablo Kettleman City in Kings County. As shown in figure (derived from the Diablo Range) or Sierra (derived from the Sierra Nevada). 1, it is bounded on the west by the foothills of the Diablo El E2 MECHANICS OF AQUIFER SYSTEMS 119° 122" 121° 120°

38"

37"

EXPLANATION

Boundary between SanJoaquinValley alluvium and de­ formed rocks

36°

FIGURE 1.-Index map of central California. Los Banos-Kettleman City area shown by diagonal ruling.

Range, and on the east, by the trough of the San J oa- due to the intensive pumping of ground water for irri­ quin Valley. _ gation, had caused more than 2 feet of subsidence of the When the first Spanish soldiers entered the valley in land surface throughout 1,200 square miles of the Los 1772, they found it populated with Indians and wild Banos-Kettleman City area as of 1959. Maximum sub­ game. Since that time the changes imposed by man on sidence of 20 feet had occurred west of Mendota; near the landscape have been primarily due to agriculture.. Huron in the southern part of the area, maximum sub­ The land has been tilled nearly to the edge of the foot­ sidence totaled 16 feet in 1959 (fig. 2). Between 1955 and hills and irrigated with water chiefly pumped from 1959 the rate of land-surface subsidence ranged from 0.2 deep wells but, in part, imported in canals; the principal foot to 1.5 feet per year. Near-surface subsidence has crops grown in the Los Banos-Kettleman City area are resulted from hydrocompaction of moisture-deficient grain, cotton, and alfalfa. Sheep graze in the Coast deposits above the water table in 82 square miles along Ranges west of the valley. the western border of the valley (Lofgren, 1960; Bull, The climate is arid and the summers are very hot. This 1964). This hydrocampaction, which is locally (fig. 2) climatic condition combined with high mineral content superimposed on the more widespread compaction due of the ground water has discouraged any large-scale to decline of head, has resulted in startling surface urban or industrial development i:p the area. Less than slum page and very extensive damage to structures. Land a dozen very small towns occupy this 1,500-square-mile subsidence in this area has been, and probably will con­ area where the annual rainfall is from 6 to 8 inches. tinue for some years to be, a serious problem in the Large declines in artesian head in confined aquifers, design and maintenance of highways, oil pipelines, COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E3

120"30'

.. Fres!Lo River ~·. -...... __ .. ·-··~ ... ~··· ·----......

Kerman \"""-.- \ I ."' I I I \ "'- I

36"30'

EXPLANATION

ff4/!P~ Boundary of deformed rocks ---6--- Line of equal subsidence Interval 2 feet. Compiled as sum of (1) comparison of topographic mapping by U.S. Geological Survey in 1922-32 and 1955 (control date) and (2) leveling by U.S. Coast and Geodetic Survey in 1955 (September­ November) and 1959 (October 1959 to January 1960); controlled in part by 1943 leveling by U.S. Coast and Geodetic Survey.

Boundary of area of near-surface subsidence as mapped in 1961

TULARE

LAKE

0 5 10 MILES BED

120"30' Base from U.S. Geological Survey Central 12o·oo• Valley map, 1:250 000, 1958

FIGURE 2.-Land subsidence, 1922-32 to 1959. E4 MECHANICS OF AQUIFER SYSTEMS powerlines, irrigation canals and ditches, and other investigation, which began in 1950, about 700 drillers' large structures. However, increased understanding of logs and electric logs were collected ; these data formed the subsidence phenomenon has made it possible to cope the basis for a general description of the water-bearing with many of the subsidence problems. deposits throughout most of the area covered in this report. PREVIOUS INVESTIGATIONS During 1951 and 1952, the U.S. Bureau of Reclama­ Geologists first turned their attention to the Los tion drilled 64 core holes in the San Joaquin Valley Banos-Kettleman City area in the 1890's when the as part of their ground-water and canal studies. Twelve first oil wells were drilled in the vicinity of Coalinga. of these core holes are in the Los Banos-Kettleman The earliest systematic geologic investigation was City area. A paper by Frink and Kues ( 1954) described that of W. L. Watts (1894), who reported on the some of the late Tertiary and Quaternary stratigraphy oil fields along the border of the San Joaquin Valley of the San Joaquin Valley as interpreted from the core­ for the California State Mining Bureau. Since that hole studies. Their paper was the first to describe time, many reports on the geology of the oil fields in, the wide extent and hydrologic importance of the Cor­ and adjacent to, the Los Banos-Kettleman City area coran Clay Member of the Tulare Formation. have been written. Most of the work, however, has been concerned chiefly with the oil-bearing formations of PURPOSE OF INVESTIGATION AND SCOPE OF REPORT Cretaceous and Tertiary age. The earliest published de­ Previous geologic investigations along the west border tailed geologic descriptions of subsurface Pliocene and of the San Joaquin Valley were concerned primarily Quaternary deposits are in papers on the Kettleman with petroleum development and were directed mainly Hills oil field by Goudkoff ( 1934) , Barbat and Gallo­ at the stratigraphy and structure of marine deposits of way (1934) and Woodring, Stewart, and Richards Pliocene age and older. Hydrologic investigations, al­ (1940). though they dealt with the compacting deposits, were The first detailed geologic studies in the area were directed mainly at evaluating the water resources of the by Arnold and Anderson (1910), who described and area. mapped the geology of the hills around Coalinga and a By 1954, pronounced subsidence of the land surface in part of the Kettleman Hills. Anderson and Pack ( 1915) most of the Los Banos-Kettleman City area and in two extended reconnaissance geologic mapping of the west­ other extensive areas in the valley resulted in the forma­ ern border of the San Joaquin Valley from the Coalinga tion of an Inter-Agency Committee on Land Subsidence area northward to Suisun Bay. Woodring, Stewart, and in the San Joaquin V a'lley for the purpose of planning Richards (1940) enlarged upon the earlier work of and coordinating the study of this phenomenon. The Arnold and Anderson in their comprehensive report on committee recommended (1955) a comprehensive in­ the geology and paleontology of the Kettleman Hills. vestigation of the extent, magnitude, eau'ses, and pos­ Their report contributed greatly to dating of the forma­ sible remedies for the subsidence. tions exposed there. As one result of the Inter-Agency planning, the U.S. Work/by later authors has been mostly detailed stud­ Geological Survey undertook intensive studies of sub­ ies of small areas. These studies include a report on the sidence due to water-level decline in the San Joaquin Moreno Formation at its type section on Moreno Gulch Valley. These studies are being made in cooperation by Payne ( 1951), a report on the geology of the Ortiga­ with the California Department of Water Resources. lita Peak quadrangle by Briggs ( 1953) , and a report on Poland and Davis (1956) summarized the available the geology of Tumey and Panoche Hills by Schoen­ information on subsidence in the Los Banos-Kettleman harner and Kinney ( 1953). The areas covered by these City area as of the start of the investigation. Ireland reports are shown in the index to geologic rna pping (1962) prepared an inventory and description of wells, (pl. 2). and Bull ( 1961, 1964) has described extent, causes, and The rapid growth of irrigation on the central west mechanics of near-surface subsidence in the Los Banos­ side of the San Joaquin Valley during and after World Kettleman City area. War II greatly increased the rate of ground-water with~ Areas of active and substantial land subsidence afford dra:wal from the late Cenozoic water-bearing deposits. an unusual opportunity to study the compaction of sedi­ This increase in withdrawal caused a rapid decline in ments in response to increase in applied stress that can water levels, and an investigation of possible overdraft be measured. In 1956, therefore, the Survey also began was made by the U.S. Geological Survey in cooperation a companion federally financed research investigation; with the California Department of Water Resources it is directed toward determining the principles con­ (Davis and Poland, 1957). In the fieldwork for this trolling the deformation (compaction or expansion) COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E5

of aquifer systems resulting from change in effective posits. Geologic sections measured at eight locations stress (grain-to-grain load), caused by change in in­ are presented in graphic form to illustrate the lithologic ternal fluid pressure. This research study on the character of the late Tertiary and Quaternary deposits mechanics of aquifer systems is under the direction of as eXiposed at the land surface (figs. 5-7) . J. F. Poland. In the 'areas mapped in detail by earlier workers, their This report is one product of the Federal research geologic .mapping was adopted in .most .paut with little program. It describes the geology of the deposits that or no modification. This was done for mapping in the are undergoing compaction in the Los Banos-Kettleman Kettleman Hills (Woodring and others, 1940), the map­ City nrea and includes discussions of stratigraphy, ping in the Tumey and Panoche Hills by Schoellhamer lithology, source, environment of deposition, structure, and Kinney (1953), and the ·mapping in the Ortigalita and geologic history. The report also describes briefly Peak quadrangle (Briggs, 1953). The principal modi­ the hydrologic framework of the compacting deposits fication, discussed under 'the Tulare Formation, involved and the chemical quality of the ground waters. the reassignment of Briggs' Oro Lorna Formation be­ Geologic mapping of the water-bearing deposits ex­ tween Little Panoche and Ortigalita Creeks to the posed along the western border of the valley is shown Tulare Formation on the basis of evidence developed on plate 1. The description of the subsurface geology during 1961-64. is supported by electric-log sections and by maps show­ The reconnaissance mapping was done by J. H. ~Green ing extent, configuration, and thickness of various im­ and ·W. A. Coclwan in July-November 1957. Aerial portant geologic units in the water-bearing section. .photographs aided immensely in this work. The usual The data presented herein furnish the basis for study procedure for mapping was to determine formation of the relationship between the physical character and boundaries by inspection in the field and then to extend depositional environment of the different types of the them on the photographs. Many repetitions of this continental sediments and their relative compaction process, with additional detailed field inspections and in response to the increased effective stress caused by measurements at selected locations, allowed m.apping of the decline in artesian head. a large area in the relatively short period of fieldwork. Other reports in this series describe the physical and The interpretation of the subsurface geology .was hydrologic properties of the: water-bearing deposits based largely on inter-pretation of electric logs of water (Johnson and others, 1968), their particle sizes and wells in conjunction with stratigr.aphic infor·mation clay minerals (Meade, 1967), and the factors that in­ from exploratory core holes. fluence change in pore volume and compaction under As .part of the Inter-Agency Committee's aotivity increasing effective overburden load (Meade, 1968). during 1957 and 1958, four core holes were drilled in Several short papers describing methods of study and 'the Los Banos-Kettleman City area. Composite logs selected findings have been published while the investi­ of these holes are presented on plate 5. gation was in progress (Lofgren, 1961; Meade, 1961a, About 500 eleotric logs and several hundred drillers' b; Miller, 1961; Poland, 1960, 1961; Poland and Even­ logs of W31ter wells collected to June 1961, and more son, 1966). than 400 single-point elootric logs of shallow explora­ The analysis and interpretation of subsurface geol­ tion holes drilled in the :San J o.aquin Valley by the ogy was done by R. E. Miller from data available prior Geochemioal Surveys of Dallas, Tex., were utilized in . to 1963. The surface geologic mapping was done in the present study. Lithologic and strrutigraphic data 1957 by J. H. Green, assisted by W. A. Cochran. A from 31 core holes in or near 1the Los Banos-Kettleman manuscript describing the subsurface geology, hydrol­ City area (table 1) .were used in preparing this report. ogy, and geochemistry of the ground waters was writ­ S.tratigraphic in~rpretations of the subsurface geology ten by R. E. Miller; a companion manuscript written are shown by a series of four transverse ·and one longi­ by J. H. Green described the stratigraphy of the ex­ tudinal sections (fig. 3) . posed rocks. These two manuscripts subsequently were revised and combined by G. H. Davis in this report. ELECTRIC-LOG INTERPRETATION The geologic map (pl. 1) included in this report Electric logs of boreholes in alluvial sediments seek shows the outcrop areas of the unconsolidated and semi­ to measure and record two quantities. The first is the consolidated formations of Pliocene and Pleistocene age variations, in the borehole, of natural electrical currents and the outlines of the moderately to poorly permeruble that flow between clay beds and more permeable beds alluvial soils that border the foothills. The Etchegoin wherever such :beds ,are in contaot. The mud oolumn in and J acalitos Formations are differentiated, and the the :borehole and the adjacent sediments constitute an Tulare Formation is distinguished from the terr.ace de- electrical resistance, and flow of current through this E6 MECHANICS OF AQUIFER SYSTEMS

R. fOE. If 12 13 120°30' 16 17 18 12o·oo• 19 R. 20 E.

T 10

0

16 ~ ~ ~ 36°30' j~ Alluvium ..,~ ~§ Mittfl Tulare Formation 17 ~ "? ~ San Joaquin Formation -~ ~ ~ iX 18 Etchegoin Formation < ~ UJ IT] 1- Jacalitos Formation 19 i~"'"' { ~ ~~ Sedimentary rocks .e undifferentiated A A' Alinement of geologic section Sections are slwum in figures 13-15 and on plates 3 and 4

13R 0 Well for which electric log is shown on geologic sections

e34Nl Core hole shown on geologic 5 T. sections or referred to in text 22 s. 36.00'~------~------~~~--~~~~~~~~~~------~------~ 36°00' 120°30' 12o•oo• Base from U.S. Geological Survey Central Geology chiefly by J. H. Green, 1957 Valley map, 1:250000,1958

FIGURE 3.--Location of geologic sections and core holes. COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E7

TABLE 1.-Core holes in or near the Los Banos-Kettleman City area made using two or more different electrode spacings. [Locations of core holes shown in figure 3] The purpose of this method, in part, is to make pos­ sible a determination of the depth of the invasion of Core hole Year Depth Drilled by- drilled (feet) the drilling-mud filtrate into the beds adjacent to the borehole. This can only be done in permeable forma­ 12/12-16111 ______1957 1,005 Inter-Agency Committee on Land Subsidence in the tions, however, and in addition, the mud resistivity, San Joaquin Valley. borehole diameter, and bed thickness must be known. 14/13-11][)1 ______1957 1, 500 lDo. 16/15-34~1 ______1958 2,000 lDo. In the more heterogeneous alluvial sediments, only 19/17-22J1, 2_--- 1957 2,203 lDo. the relative amount of drilling-mud-filtrate invasion 10/14-8BL ______1952 1,002 U.S. Bureau of Itcclamation. 11/11-2J1 ______1952 600 lDo. can be determined. This is done by noting the differ­ 11/11-22Q1 ______1952 598 lDo. ences in resistivity recorded for the same stratum by 11/15-33P1 ______1952 850 lDo. 11/16-10~1 ______1952 500 I>o. resistivity curves made with different electrode spac­ 11/18-8QL ______1952 810 lDo. ings. If the drilling mud has a lower restivity than the 12/12-20J1 ______1952 430 lDo. 12/12-25][)1 ______1952 420 lDo. pore water in the formation, then the resistivity re­ 12/17-8GL ______1952 500 lDo. corded by the shorter electrode spacing is lower than 12/18-13111 ______1952 700 lDo. 13/15-35EL _____ 1952 735 lDo. that recorded by the longe.r spacing and the radius of 13/16-2CL ______1952 750 U.S. Bureau of Iteclamation. the drilling-mud-filtrate invasion is greater. If the 14/15-25111______1952 705 lDo. 15/12-23Q1 ______1952 850 lDo. drilling-mud filtrate has a higher resistivity than the 15/14-15EL _____ 1952 800 lDo. pore water, the reverse relationship occurs. The depth 15/16-12CL _____ 1952 733 lDo. 15/16-17L1 ______1952 800 lDo. of the mud-filtrate invasion is sometimes an indicator 15/16-28A1 ______1952 800 lDo. of the relative permeability of the bed invaded, be­ 17/16-30A2 ______1952 1, 500 lDo. 20/18-13C_------1936 3, 501 Seaboard Oil Corp. of cause, in beds composed of similar sediments, the greater lDelaware. the permeability, the greater the amount of mud-filtrate 19/18-15C ______1929 1, 022 Shell Oil Co. 19/18-24]1 ______1929 2,559 lDo. penetration. This criterion can only be used as a rough 19/18-2611 ______1929 3,071 lDo. indicator, however, and is not always dependable be­ 19/18-27~------1929 2, 242 lDo. 19/19-17P ______1929 3,835 lDo. cause other factors are involved, such as variations in 20/18-6B ______1929 3, 607 lDo. hole diameter, thickness of the bed in relation to the 20/18-llA ______1929 1, 881 lDo. electrode spacings, and the difference in head between NOTE.-In determining the source areas of the deposits, the authors are indebted the drilling mud and the formation water. to Ira E. Klein, of the U.S. Bureau of Reclamation, for his petrographic analysis of many of the core samples. The type of sediments forming alluvial strata is re­ resistance causes a potential change equal to the pro­ flected by their spontaneous potential and resistivity duct of the ·magnitudes of the resistance and the cur­ as shown in figure 4. Clays generally give a maximum rent. The driving potential that causes the currents to deflection to the right on the spontaneous-potential circul.ate is called a spontaneous or self potential. The curve and have a low resistivity on the resistivity curve. record of variations of this potential in millivolts is Fresh-water sands and gravels give a deflection to the the "S. P. curve" of .the electric log. left on the spontaneous-potential curve and have a high The second quantity that the electric log seeks to resistivity on the resistivity curve. The greater the measure is the electrical resistivity of the strata amount of clay and silt present in a sand, the lower penetrated by the borehole, generally expressed in ohm­ the resistivity. If a bed contains brackish water, it gen­ meters (ohm-m2/m). This measurement is commonly erally gives a large deflection to the left on the spon­ done by what is known as the three-electrode method, taneous-potential curve and has a low resistivity. The in which one current electrode is placed at the surface, type of alluvial sediments present in the bed then has and the other current electrode and two potential elec­ to be approximately by the relative amount of drilling­ trodes variously spaced on a mandrel or "sonde" are mud invasion, assuming that greater invasion would lowered into the borehole. The distance between the occur in sands than in clays. :More detailed information potential electrodes is called the pickup span, which on electric-log interpretation can be found in many is generally small compared with the distance between texts on the subject. the borehole current electrode and the midpoint be­ The electric logs included on geologic sections in tween the potential electrodes which is commonly called this report show only two curves. These two are the the electrode spacing of the arrangement. The greater spontaneous-potential curve on the left and the short the electrode spacing, the deeper the penetration of the spacing ("short normal") resistivity curve on the right. current into the beds forming the walls of the bore­ Because of the small scale of the sections, it was not hole. Resistivity curves on electric logs are generally practicable to show the longer spacing ("long nor- ES MECHANICS OF AQUIFER SYSTEMS

TYPICAL ELECTRIC LOG WITH INTERPRETATION by the California Department of Water Resources. It SELF-POTENTIAL RESISTIVITY REMARKS shows the locations of wells according to the rectangu­ lar system for the subdivision of public land. For ex­ Interbedded sand, silt, and clay indi­ ample, in the number 14/15-18E1, which was assigned cated by moderate deflection of the self-potential and resistivity to a well 2% miles south of Mendota, the part of the curves number preceding the slash indicates the township (T.

Clay or shale beds indicated by 14 S.); the number following the slash, the range (R. ;;mall self-potential and resisitiv­ •ty deflections 15 E.) ; the digits following the hyphen, the section (sec. 18); and the letter following the section number, Fresh-water sand beds separated the 40-acre subdivision of the section as shown in the by silt and clay strata. Fresh-water sand typically has moderate self­ accompanying diagram. potential and high resistivity values

Sand beds containing slightly saline D c B A water interbedded with silt and clay strata, indicated by large self­ potential and moderate resistivity E F G H deflections ---- M L K J Thin-bedded sand, silt, and clay --- containing brackish or salt water indicated by high self-potentiai N p Q R and low resistivity values

Within each 40-acre tract the wells are numbered EXPLANATION serially, as indicated by the final digit of the number. ~ D ~ ~ ~ Thus, well14/15-18E2 is the second well to be listed in Sand Clay Silt Sand As and silt the SW1,4 of the NW% of sec. 18. all of the Los Banos--Kettleman City area is south and east of the FIGURE 4.-Typical electric log with interpretation. From Davis and Poland (1957, pl. 30). Mount Diablo base and meridian, the foregoing abbrevi­ ation of the township and range is sufficient. Explora­ mal") resistivity curve on the geologic sections· but tion test holes and oil wells have not been assigned ~his second. resistivity curve also was used in stud; and final digits. InterpretatiOn of the electric logs. GEOLOGY

ACKNOWLEDGMENTS GEOLOGIC HISTORY AND STRUCTURE The writers are grateful for the whole-hearted co­ The San Joaquin Valley is a great structural down­ opera~ion and material aid received from other public ways between the tilted block of the Sierra Nevada on ~genCies part~cipating in the Inter-Agency investiga­ the east and the complexly folded and faulted Coast tiOn, from private firms, and from individuals in the Ranges on the west. The geologic history and develop­ San Joaquin Valley. Special thanks are due to Ira E. ment of the valley is intimately related to events in the Klein, geologist, Bureau of Reclamation, whose petro­ bordering mountains ; hence, geologic studies in the graphic studies of many of the core sample furnished mountains are most helpful in unraveling the geology part of the basis for interpretations of the source of of the valley. the deposits; to Geochemical Surveys Inc., of Dallas, The Sierra Nevada rises from an altitude of 500 feet Tex., who supplied electric logs of some 400 explora­ along the east border of the San Joaquin Valley to more tory holes drilled by them; to the California Division than 14,000 feet in a distance of about 60 miles. The of Highways for supplying excellent low-altitude aerial range may be visualized as a much-dissected tilted pla­ photo¥raphs of the western border of the valley, which teau, uplifted along its eastern flank and depressed were Invaluable in the geologic mapping; to Griffin along its western flank, where it is overlain by sedimen­ Inc., for permission to drill core holes on their prop­ tary deposits of the San Joaquin Valley. erty; and to the Pacific Gas & Electric Co., for supply­ The erystalline complex of the Sierra Ne,vada con­ ing information on well yields and pumpage. sists of metamorphosed shale, sandstone, limestone, and chert, intruded by plutonic rocks that range in composi­ WELL-NUMBERING SYSTEM tion from peridotite to granite. The bulk of the rocks The well-numbering system used in this report is the of the range,, however, are of granitic composition. one used by the Geological Survey in California and Sparsely scattered fossils found in the metasediments COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E,g

indicate marine deposition during the Paleozoic Era GEOLOGY OF THE TRIBUTARY DRAINAGE AREA, and in the Triassic and Jurassic Periods. Potassium­ DIABLO RANGE argon dating of the intrusive rocks (Curtis and others, Beneath the Los Banos-Kettleman City area, pre­ 1958; Kistler and others, 1965) suggests three intrusive dominantly well-sorted sandy sediments from the Sierra episodes: Early Jurassic, Late Jurassic, and Late Nevada interfinger with predominantly poorly sorted Cretaceous time. silty and clayey sediments from the Cbast Range. Con­ Beneath the San Joaquin Valley, crystalline base.­ tinental deposits of Pliocene and Pleistocene age, and, ment rocks similar to those exposed in the Sierra N e­ to a lesser extent, Pliocene marine sediments, together vada are overlain by a wedge of sediments, partly of with overlying Holocene alluvium, constitute the marine origin, that thickens westward. The full thick­ ground-water reservoir of the Los Banos-Kettleman ness of these rocks has not been penetrated by drilling, City area. but geophysical and other indirect evidence suggests The geology of the tributary drainage area in the that the Sierra Nevada block extends westward to the Diablo Range to the west is directly pertinent to this flanks of the Coast Ranges (Davis and others, 1959, investigation for several reasons. First, this tributary p. 41). The oldest beds known from driUing in the Los area is the source of more than half of the deposits that Banos-Kettleman City area are of Late Cretaceous age. constitute the ground-water rese~rvoir. Second, the geo­ Marine sediments of Early Cretaceous age, however, logic history of the tributary mountain area is an aid in are exposed in the Diablo Range to the west and may deciphe,ring that of the valle,y deposits. Third, the fine­ extend a short distance beneath the San Joaquin Valley grained deposits of the ground-water reservoir, which along its western border. are derived chiefly from the Diablo Range source area, The Diablo Range (the most easterly of the Coast are the ones most subject to con1paction. For these sev­ Ranges) forms the western border of the San Joaquin eral reasons, the source areas in the Diablo Range a.re Valley. In a general sense, the structure of this range is described in some detail on following pages. a broad anticline whose eastern monoclinal limb dips Plate 2 presents a highly generalized picture of the beneath the valley. The exposed core of the range is geologic units that underlie the drainage basins of the formed by complexly folded and contorted sedimentary west border of the San Joaquin Valley between latitude and igneous rocks of the Franciscan Formation. Less 36°N. and 37°N.-virtually the west border of the Los deformed sedimentary strata exposed along the western Banos-Kettleman City area. The geologic units have borde.r of the valley and folded during the uplift of the been combined into six broad categories as shown in Coast Ranges range in age from Late Cretaceous to table 2. Qua.ternary. The formational units listed are those given in the Although broadly anticlinal, the Diablo Range is principal sources of the m:apping as shown in the index eha:ra.cte~ized by lesser folds that trend obliquely to the to plate 2-namely, Arnold and Anderson, 1910; range and pass beneath the valley. In general, the struc­ Anderson and Pack, 1915; Woodring and others, 1940; tural complexity along the west flank of the Los Banos­ Schoellhamer and Kinney, 1953; Briggs, 1953; and the Kettleman City area increases southwa,rd. For example, California Division of Mines, 1958 (Santa Cruz sheet). the Kettleman Hills is the surface expression of one of The general description of the geology of the drain­ these oblique-trending anticlinal folds. age area tributary to the Los Banos-Kettleman City During the Cretaceous and throughout early Tertiary area is based on the same sources as plate 2. Specific of time, the Los Banos-Kettleman City a,re~a was the site references have largely been omitted for the sake of ma.rine deposition. From Miocene time onward, depo­ simplicity. Formational names and ages used in the discussion are in accord with the currently accepted sition was mainly nonmarine in the northern part of nomenclature of the U.S. Geological 'Survey. the area., while marine deposition continued in the southern part until late in Pliocene time. The youngest JURASSIC AND CRETACEOUS ROCKS marine deposits, 'vhich are extensively exposed along In can readily be seen from plate 2 that rocks of the the southwestern border of the area, are sedimentary oldest generalized unit, those of Jurassic and Creta­ rocks of the Etchegoin and San Joaquin Formations, ceous age, are common in the tributary drainage basins of middle and late Pliocene age, respectively. The Plio­ in the northern part of the area. Rocks of this unit are cene marine deposits grade northward into nonmarine not ·common in the southern part of the area where deposits. At the north edge of the area., the youngest marine rocks of Cretaceous and Tertiary age predomi­ exposed marine deposits are in the San Pablo Forma­ nate in the drainage basins. The areas occupied by the tion of Miocene age. different geologic units within 13 df the largest drain- ElO MECHANICS OF AQUIFER SYSTEMS

TABLE 2.-Generalized geologic units of the drainage area tributary has been recognized, but Briggs ( 1953, p. 11) estimates to the Los Banos-Kettleman City area that at least 20,000 feet of the Franciscan is exposed Generalized geologic unit Symbol Formations and age near Ortigalita Peak. on pl. 2 The Franciscan of this area consists predominantly Alluvium ______Qal Alluvium (Pleistocene and of thin-bedded and massive graywacke sandstone, dark Holocene). slaty shale, and siltstone. Other common rock types in­ clude bedded chert and mafic volcanic rocks (sometimes Undifferentiated QTu Alluvium (Pleistocene and continental Holocene), terrace deposits 1urn ped under the general term "greenstone") . Less deposits. (Pleistocene), and Tulare common rock types include limestone, glaucophane Formation (Pliocene and Pleistocene). schist, and ·actinolite schist.

Continental and QT Terrace deposits (Pleistocene); ULTRAMAFIC INTRUSIVE ROCKS marine sedimentary Tulare Formation (Pliocene deposits of late and Pleistocene); San Joaquin, Ultramafic rocks intrusive into the Franciscan have Tertiary and Etchegoin, and Jacalitos Quaternary age. Formations (Pliocene). been noted in many places. Most of these are narrow bodies of small extent, although one such body under­ Marine sedimentary Tu San Pablo, Temblor, Santa lies more than 35 square miles in T. 18 S., Rs. 12 and and volcanic rocks Margarita, and Vaqueros of early Tertiary Formations (Miocene); 13 E. The ultramafic rocks are commonly termed ser­ age. Monterey Shale (Miocene); pentine, beoause they have been almost completely Qui en Sabe Volcanics of Taliaferro (1949) (Miocene?); altered to minerals of the serpentine group. In addi­ Kreyenhagen Formation (Eocene and Oligocene?); tion, hornblende-quartz gabbro has been reported in the Domengine Sandstone, northern part of the area by Briggs ( 1953, p. 17). Yokut Sandstone of White, (1940), Avenal Sandstone, and Tesla Formation CRETACEOUS SEDIMENTARY ROCKS (Eocene); Lodo Formation (Paleocene and Eocene) ; LOWER CRETACEOUS SEDIMENTARY ROCKS Laguna Seca Formation of Payne (1951) (Paleocene); Lower Cretaceous sedimentary rocks unconforma:bly and Martinez Formation (Paleocene). underlie Upper Cretaceous strata north of Little Panoche Valley in sees. 8 and 17, T. 1'3 S., R. 10 E. Marine sedimentary Ku Moreno Formation (Upper (Briggs, '1953, pl. 1). At least 1,800 feet of dark shale rocks of Cretaceous Cretaceous and Paleocene?) ; age. Panoche Formation (Upper and thin hard carbonaceous sandstone extends for 2 Cretaceous); Wisenor Forma­ miles between the basal conglomerate of the Panoche tion of Briggs (1953) (Lower Cretaceous). Formation and rocks of the Franciscan Formation, with which they are in fault contact on the west. These Marine sedimentary KJu Franciscan Formation and Lower Cretaceous str·ata have been named the Wisenor and volcanic rocks associated ultramafic intru­ of Jurassic and sive rocks (Jurassic and · Formation by Briggs ( 1953, p. 20). Cretaceous age and Cretaceous). associated ultra- mafic instrusive UPPER CRETACEOUS SEDIMENTARY ROCKS rocks. The thickest and most extensively exposed strati­ graphic unit in the areas tributary to the Los Banos­ age basins are given in table-3 (modified from Davis, Kettleman City area is the Panoche Form·ation of Late 1961, table 1, p. B7). Because most of the materials Cret•aceous age. This unit forn1s a nearly continuous eroded from these basins have been deposited on allu­ belt roughly 6 miles or 1nore wide t.hat extends virtually vi·al fans, there has been little mixing of erosional uninterrupted nearly the entire length of 1the ·area. The debris from drainage basins underlain by differing lithologies. thickness ranges from about 8,000 feet north of Coalinga to 30,000 feet north of Little Panoche Valley '"here FRANCISCAN FORMATION the base and top of the unit are both exposed (Briggs, 'The Franciscan Formation, which forms the core of 1953, p. 24). Except where it overlies Lower Creta­ the Dia:blo Range, is most extensively exposed in the ceous rocks, the Panoche is in fault contact with the northern part of the area shown on plate 2, particularly Franciscan Formation along its western contact. in the drainage areas between Los Banos and Little In the southern part of the area the Pm1oche con­ Panoche Creeks. It underlies '26-81 percent of these sists predominantly of massive sandstone, flaggy sand­ four drainage areas (table 3). Its maximum thickness stone, coarse cong·lomeraJte, siltstone, and mudstone. is unknown as neither the top nor base of the formation North of Panoche Creek, the Panoche is generally finer, COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA Ell

TABLE 3.-Areasl of generalized geologic units within stream basins

[Modified from Davis, 1961, p. B7]

Area, in percent, occupiE"d by indicated geologic unit Drainage Marine sedi­ Marine sedi­ Continental Drainage basin area (square Franciscan Ultramafic mentary mentary deposits of miles) Formation intrusive rocks of rocks of Tertiary and rocks Cretaceous Tertiary age Quaternary age age

Los Banos ______132 81 0 16 3 0 Salt (Merced County) ______26 26 0 55 0 19 60 43 0 33 0 24 Panoche ______103 41 0 25 0 34 ~r:Irea~~~~ch~~~~~======298 17 0 26 42 15 Cantua------~------48 0 13 52 35 0 Salt (Fresno County) ______25 0 0 68 32 0 1Dornengine ______11 0 0 59 41 0 Los Gatos ______127 0 6 84 10 0 VVarthan ______110 3 0 34 59 4 Jacalitos ______60 34 0 5 61 0 Zapato ______47 5 0 40 50 5 Canoas ______20 0 0 19 65 16

1 Areas and percentages based on them are approximate; determined by planimeter from "Geologic map of California" (Jenkins, 1938; Kundert, 1955). and, although massive fine concretionary sandstone the Franciscan Forn1ation (p. 022, C73). In contrast forms an important part of the unit, dark mudstone he found that the clay minerals derived from the marine with thin beds of fine sandstone predominates. sedimentary rocks of Cretaceous and Tertiary age are Overlying the Panache with little, if any, unconform­ predominantly montmorillonite. Such differences in clay ity, is the Moreno Formation, which includes the young­ mineralogy directly affect the compactability of the est Cretaceous rocks and probably beds of Paleocene sediments that are subject to increased effective stress age. The Moreno ranges in thickness from 1,000 to about resulting from artesian-head decline. 2,500 feet. The different types of rocks also have a profound The Moreno is characterized by purplish or maroon influence on the chemical character of the stream waters organic mudstone. Much of the mudstone is diatoma­ of the area, as shown by Davis (1961, p. B20-B21). The ceous and is white where weathered. M,assive concre­ ultramafic rocks supply abundant magnesium, and the tionary sandstone identical to that of the Panoche n1udstones and shales account for large sulfate con­ Formwtion locally makes up a substantial part of the centrations in the waters. Moreno, but the :most important constituent after the organic deposits is mudstone. LOWER TERTIARY SEDIMENTARY ROCKS The marine sedimentary rocks of early Tertiary age, SIGNIFICANCE OF MESOZOIC ROCKS as the term is used in this report (pl. 2; table 2), include Underlying more .than half of the drainage basins all the rocks of Paleocene, Eocene, Oligocene, and Mio­ tributary to the western slope of the San Joaquin Valley cene age. In the northern part of the area especially, in the Los Banos-Kettleman City area, 1and the steepest some sedin1entary deposits laid down in brackish water parts of those drainage basins, the rocks of Mesozoic and some continental deposits are included in this unit. age are the predominant source of sediment of the west­ As compared to the Mesozoic rocks, the post-Oligocene side streams. These rocks are 'more than 50,000 feet thick rocks are characterized by rapid changes in lithology in places and consist predominantly of clastic sedi­ over short distances and by a greater proportion of or­ ments-chiefly feldspathic sandstone and mudstone, ganic deposits. As shown on plate 2, the lower Tertiary although mafic' and ultramafic igneous rocks are promi­ deposits form a narrow, discontinuous ribbon of out­ nent in the Fr;tnciscan sequence and organic sediments crops flanking the San Joaquin Valley north of Panache are important in the uppermost Cretaceous deposits. Creek. They are thicker and more extensively exposed The type of material eroded from the various source south of Panache Creek, especially along the flanks of rocks influences the lithology, mode .and rate of deposi­ the Vallecitos syncline south of Panoche Valley, and in tion, and compactibility of the materials deposited in the drainage basins of W arthan and J acalitos Creeks the ~San Joaquin Valley. For exam,ple, Meade (1967) southwest of Coalinga. concluded in his studies of the sediments from the Little The large eX~posure of lower Tertiary rocks shown in Panache Creek basin that mixed-layer montmorillonite­ the northwest corner of the area consists of the Quien illite and iHite seem to be derived largely from rocks of Sabe Volcanics of Taliaferro (Leith, 1949). These vol- E12 MECHANICS OF AQUIFER SYSTEMS

canic rocks consist of about 4,000 feet of andesite and near the base and is cut by many sandstone dikes. The basalt flows, and sediments, including agglomerate, con­ Kreyenhagen is as much as 2,000 feet thick north of glomerate, and tuffaceous sandstone, intruded by Cantua Creek but thins to about 700 fe,e.t in Merced rhyolite and andesite. The age of the volcanic rocks has County. The Kreyenhagen is extensively exposed in the not been determined, but, on the basis of evidence from basins of Arroyo Ciervo and Arroyo Hondo, and frag­ other areas in the Coast Ranges. Leith concluded that ments of the distinctive shale are ubiquitous on the Hol­ the Quien Sabe Volcanics was of Miocene age. ocene alluvial fans of these streams in the San Joaquin The marine sedimentary rocks of early Tertiary age Valley. are similar in many respects to the Cretaceous sedimen­ The Kreyenhagen is particularly important as a tary rocks. Arkosic sandstone, commonly containing as ma,rker, especia.lly in the northern part of the area and much as 50 percent feldspar, and sandy or silty shale, beneath the valley, where it not only is of distinctive commonly micaceous, make up most of the lower Ter­ lithology but also is the youngest e!Xtensive marine de­ tiary section. In parts of the area, however, organic posit. The overlying Miocene deposits, although marine siliceous shale of the Kreyenhagen Formation makes up in part, are in part subaerial and a,re therefore difficult fully half of the lower Tertiary section. to trace on the surface and in the subsurface. The marine Kreyenhagen Formation where it under­ PALEOCENE AND EOCENE MARINE SEDIMENTARY ROCKS lies the fresh-water-beraring deposits on geologic sec­ Between the organic siliceous Moreno Formation tions A -A' and B-B' (pis. 3, 4) is about 700-800 feet (Upper Cretaceous and Paleocene?) and the organic thick. At the nearest outcrop north of Panoche Hills siliceous Kreyenhagen Formation (Eocene and Oligo­ (Briggs, 1953, p. 41-44), the Kreyenha,gen is 700 feet cene?) are clastic marine sedimentary rocks of Paleo­ thick, the basal part consisting primarily of a brown cene and Eocene age. In most of the area a sequence of sandy shale and white laminated sandstone, overlain hy dark clay shale with fine sandy beds rests conformably more than 600 feet of white-weathering diatomite and on the Moreno. This unit, the Lodo Formation, is ex­ radiolarite. Seven miles northeast of this outcrop, on posed from Panoche Creek south to the Coalinga anti­ longitudinal geologic section A -A' (pl. 3), the top of cline. Locally, especially in the upper basins of Cantua the Kreyenhagen Formation is at a depth of 2,800- Creek and Arroyo Hondo, the Lodo contains a massive 3,200 feet. Opposite the Panache Hills the dip of the concretionary sandstone member. The Lodo ranges in formation incre,ases southward; beneath Tula,re Lake thickness from about 1,000 feet north of Coalinga to as bed, 45 miles to the south, electric logs of deep oil ex­ much as 5,000 feet in the upper basin of Arroyo Hondo. ploration holes show its top to be at a depth below North of the Fresno-Merced County line similar dark 11,000 feet. The Kreyenhagen Formation is unconform­ clay shale about 1,200 feet thick exposed along the west ably overlain by Miocene marine and nonmarine strata, border of the San Joaquin Valley has been called the except in surface exposures in the Panoche Creek area Laguna Seca Formation by Payne (1951). (Schoellhamer and Kinney, 1953) where it is over­ Overlying the shale of the Lodo Formation and rest­ lapped by the Tulare Formation (Pliocene and ing directly on Cretaceous rocks in the Panoche Hills Pleistocene,) . is a light-yellow to white quartzose sandstone unit 50- MIOCENE DEPOSITS 750 feet thick. The sandstone is interbedded with highly The Miocene deposits along the west border of the colored shale, carbonaceous clay, clay shale, and pebble Los Banos-Kettleman City area are ma,rked by great beds. This distinctive lithology, which generally is in­ changes in thickness and lithology along their strike. terpreted as indicating tropical weathering in Eocene In the southern part of the area,.--south of Coalinga time, is known variously as the Tejon Formation, and at Kettleman Hills-the Miocene is represented by Domengine Sandstone, Y okut Sandstone of White thick marine shales and sandstones. North of Coalinga ( 1940), and the Telsa Formation. and extending to Panoche Creek the section is pre­ Southwest of Coalinga the Kreyenha,gen Formation dominantly marine sandstone with interbedded diato­ is underlain by an Eocene sandstone (the A venal Sand­ ma,ceous shale. North of the Fresno-Merced County line stone) about 500 feet thick that rests directly on Upper the Mi·ocene is represented by a thin sequence of tuf­ Cretaceous rocks. faceous, partly nonmarine sandstone, gravel, and clay. Overlying the clastic sedimentary rocks of Eocene Wells in the Kettleman Hills penetrate some 4,000 age throughout the are~a is a highly organic siliceous feet of Miocene strata consisting of 500 feet of the Reef marine shale, the Kreyenhagen Formation, locally of Ridge Shale, a soft silty shale with some interbedded Eocene and Oligocene(?) age. In addition to the or­ volcanic sandstone; 1,500 feet of the McLure Shale ganic shale, the Kreyenhagen also contains sandstone Memrber of the Monterey Shale, a brown porcelaneous COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E13 organic mudstone; and 2,000 feet of the Temblor For­ posits capping the older rocks as well as valley fill in mation, predominantly dirty sandstones and inter­ the Vallecitos, Panoche Valley, and lesser valleys, have bedded shales. been treated on plate 2 as undifferentiated continental Only 20 miles northwest along strike, from Kettleman deposits df Pliocene to Holocene age. Hills, the Miocene section exposed at the north end of Anticline Ridge consists of nbout 1,200 feet of pre­ STRATIGRAPHY OF THE WATER-BEARING DEPOSITS dominantly sandstone. The upper 550 feet, the Santa The fresh-water-bearing deposits forming the Marga,rita Formation, is a fine-grained, locally pebbly, ground-water reservoir in the Los Banos-Kettleman brown sandstone with some calcareous reef-forming City area are restricted to late Pliocene and younger beds. The lower 650 feet is the Temblor Forn1ation, fonnations. The principal aquifers occur within the chiefly soft gru,y to blue sandstone interbedded with alluvial and lacustrine deposits of the Tulare Forma­ diat•otnaceous siltstone and shale. Between Anticline tion of Pliocene and Pleistocene age. The underlying Ridge and Cantua Creek the upper part of the Te,mblor formations of Pliocene age contain brackish or saline consists of the Big Blue Serpentinous Member, a shale water, ex,cept in the central southwe,stern part of the characterized by a high content of serpentine flakes area where fresh-,vater-bearing strata occur in the San which give it a distinctive blue color. Bet,veen Panoche J oa.quin Formation and in the upper part of the Creek and the Fresno-Merced County line, the Miocene Etchegoin Formation. No fresh water is known to occur beds are ovedU1pped by younger deposits. North of the in the tT acalitos Formation or underlying strata. county line the Miocene section consists of the San Surface and subsurface geologic studies made as part Pablo Formation, which rests unconformably on the of this investigation were focused on the fresh-water­ Kreyenhagen Formation. The San Pablo varies in bearing deposits because compaction of these deposits thickness from less than 100 to 400 feet and consists of due to withdrnwal of ground water was presumed to volcanic gravel, sand, and clay. It is characterized by be the major cause of the land subsidence. irregulady colored red, yellow, and green tuffaceous Unconsolidated to semiconsolidated deposits of Plio­ deposits. Locally, marine fossils are found in the San cene and Pleistocene age which erop out along a rela­ Pablo, hut much of it is of fresh water or suba,erial tively continuous strip 1_.:6 miles wide bordering the deposition. western flank of the project area were mapped for this The subsurface geologic information available was report. They include 'the J acalitos, Etchegoin, San insufficient to differentiate the Miocene formations that Joaquin, and Tulare Formations, ancl terrace deposits. have been mapped in the foothills along the western These strata are chiefly continental but, locally, of boundary of the Los Banos-KettleJnan City area on the marine origin. The surface extent of each oif these for­ electric logs of the geologic sections. They are shown, mations is shown on plate 1; they are shown jointly therefore, as an undifferentiated unit overlying the as one unit, "Continental and marine sedimentary de­ J(reyenhagen Fonnation. posits," on the generalized geologic map (pl. 2). In the southern part of the area, where the undiffer­ In general, the older of these Pliocene and Pleisto­ entiated Miocene deposits underlie the fresh-water­ cene formations are more consolidated than the younger bearing deposits, the section is primarily marine. There, units. Silt, sand, and sandy silt strata comprise the it is 3,000--4,000 feet thick, and its top is at a depth of tnajor part of the exposed section; true day is rare. 6,000-7,000 feet. In the northern part of the area, the Sandstone, gravel, and conglomerate are relatively com­ subsurface Miocene section is prim·arily of continental mon, and the,ir presence is usually marked by strong deposition, 700-800 feet thick, and its top is at a depth topographic relief. Good exposures are uncommon, of 1,900----:2,000 feet. owing to the relatively unconsolidated character of the UPPER TERTIARY AND QUATERNARY DEPOSITS deposits. Slumpage, weathering, and soil formation UNDIFFERENTIATED also contribute to the difficulty of finding fresh expo­ sures. Generally, deep stream cuts, roadcuts, and back In the drainage basins tributary to the Los Banos­ slopes of hills provide the best outcrops. Ketfleman City area are many isolated bodies of con­ tinental deposits of late Tertiary and Quaternary age. Lithologic characteristics change parallel to the Rocks of this age flanking the San Joaquin Valley have strike of the beds as weU as normal to it. This feature, been mapped (pl. 1) ns part of this investigation, but coupled with the lack of good exposures, makes long­ time and funds did not permit study of presumably distance correlations impractical. Extensive use of equivalent deposits farther back in the Coast Ranges. aerial photographs, in part, helped to alleviate this Accordingly, these deposits, which include terrace de- problem. E14 MECHANICS OF AQUIFER SYSTEMS

In the following descriptions of the surface geology, comprising the J acalitos Formation greatly influence the Jacalitos, Etchegoin, San Joaquin, and Tulare For­ its topographic development. Strike valleys, formed mations ~are described from south to north. Measured between more resistant stData above and below, charac­ geologic sections are presented in the text in the same terize the major paDt of the outcrop area near Oilfields order. ·and near Arroyo Hondo. Elsewhere, the more consoli­ In order to show the character, source and environ­ dated sandy rocks of the J acaHtos resist erosion equally ment of deposition, and 'the relationship of the strata ·as well as the younger deposits above, but not nearly forming the aquifer systems in the Los Banos-Kettle­ so well as the older rocks below. Therefore, the surface man City area, five geologic sections based on drill-log, outcrops of the J acalitos generally are considerably core-hole, and electric-log data are presented on plates low·er than rthose of the older rocks rto the west. 3 and 4. The location of these sections is shown in figure 3. The land-surf,ace elevation datum used on all LITHOLOGY the cross sections in this report is taken from the 1922- The J,acalitos Formation consists mainly of banded 32 series of U.S. Geological Survey topographic maps. red, green, and gray silt and sandy silt beds and only It was not considered 1practical to compensate for eleva­ minor amounts of sandstone and gravel. When seen tion changes caused by compaction and 1to adjust :the from the West, particularly in the late afternoon or land-surface datum on ~any of the geologic sections or evening sun, the color banding of the silt is very notice­ on the structure map because of the subsidence. The able and in places very outstanding. land-suriace datums of the individual core Jogs and elec­ Measured sections of :the J acalitos Formation are tric logs used in this report -are from the .period 1929- shown in figure 5. A section spanning the full outcrop 1961; so the approxi~mate maximum error ~that could of the Jacalitos (fig. 5A, section a to a') was measured have been introduced by }and-surface subsidence oon 3.5 miles south of Salt Creek. be determined from the rna p shown in figure 2. From near the tbwn of Oilfields north to Salt Creek •Generalized composite logs of four core holes, drilled the upper part of the :f1ormation contains a blue sand­ as part of the ~program of the Inter-Agency Commit­ stone similar to those found in the overlying Etchegoin tee on Land Subsidence, are presented on plate 5. Formation. Logically, this sandstone might be included JACALITOS FORMATION (PLIOCENE) with lithologically similar materials above. Arnold and Anderson (1910, p. 114), however, defined the base of The Jacalitos Formation was named ,by Arnold and the Etchegoin Formation as the Glycymeris fossil zone, Anderson ( 1908) for its chaDacteristic exposures near which in this area lies above the lowest blue sandstone. J acalitos Creek. According to Arnold ( 1909, p. 23), That definition was followed for this investigation. The formation may be roughly distinguished as that portion Below the sandstone, and continuing to the base of the of the series between the shale of the Santa Margarita ( ? ) J aealitos Formation, is an alternating se·ries of red and ;below 'and the major 'beds of 1blue sand that characterize the gray silt interbedded with sandstone and gravel. The lower par.t of the formation above i:t (the Etchego in) through­ out the district. The Jacalitos, however, includes a great thick­ basal unit of the forma.tion in this area generally is a ness of rblue sand 'bedS at its summit in the southeastern part deep red silt, but, locally, a fossiliferous sandy gravel of the Kreyenhagen Hills. ma,rks the base. Fossils found in the Jacalitos generally a.re waterworn and broken, indicative of reworking by EXTENT streams. Opalized wood fragments are common, includ­ The J acalitos is the oldest formation mapped for this ing remnants of large logs or tree trunks. report. It crops out discontinuously from the southern Between Salt and Cantua Creeks, the top of the J aea­ end of the San Joaquin Valley to a point about .4 miles litos is taken as the top of the bed just beneath the north of Arroyo Hondo. Plate 1 shows the extent of lowest blue sandstone. In a section measured 0.3 mile the formation ns mapped in this investigation-from south of Cantua Creek (fig. 5B, section b"' to b""), the Anticline Ridge north about 23 ~miles to 1 mile north top is an olive sand. The blue sandstone found in the of Arroyo Ciervo. The average width of surface ex­ J acalitos farther south does not extend into this area, posure of the Jacalitos in this area is less than 1 mile. In nor does the Glycymeris zone. The red silt found at the general, the outcrop width decreases from about a mile base to the south grades northward into drab gray and near the junction of State Highway 33 and the tan silt. With the gradational color change, the basal Coalinga-Fresno Road to less than a quarter of a mile member becomes more sandy in the vicinity of Salt at Arroyo Ciervo, north of which it is overlapped by Creek. At Cantua Creek, the basal member is taken as younger deposits of the Etchegoin Formation. the first gray silt overlying fossiliferous Miocene gravel The predominantly fine-grained sedimentary rock and sandstone. COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E15

A B THICKNESS, MODE OF ORIGIN, AND STRATIGRAPHIC RELATIONS

=-+~ 0 • -:-: · · ·.· ·· Olive ~;~ ~~~ 2.i The exposed section of the J acalitos Formation thins f+:d~ gray progressively from a stratigraphic thickness of more than 1,000 feet, near the intersection of State Highway EXPLANATION ~~~ :::::::::::Blue ~ 33 and the C()alinga-Fresno Road, to nothing about 4 E§E ~~~ miles north of Arroyo Hondo where it is overlapped by ~~..;.:gray the Etchegoin Formation. Sand Massive, thick sections of silt suggest the possible ti~ti marine origin of most of the J acalitos Formation. ~}~~Blue Minor amounts of crossbedded sandstone indicate that Silt at least part of the formation is of deltaic origin. The presence of a number of bones and teeth of unidentified terrestrial animals, found in NW;iNWlA, sec. 13, T.

Gravel 19 S., R. 15 E., indicates continental deposition at that locality. Angular unconformities are not apparent between the J acalitos Formation and either the overlying or Shale underlying formations in this area. Aerial photogra;phs, however, show that each unit in turn overlaps tJhe next older formation, indicating that disconformities prob­ Silt, sandy ably exist between them. Other evidence of a discon­ formable contact at the base of the J acalitos Formation is the presence of fossil wood in the basal conglomerates. f{} Brown Siltstone The Jacalitos Formation is generally considered to

..:..:....:...: be of Pliocene age. Woodring and others ( 1940, p. 103) state, 100 l*~ Brown The assignment of the Jacalitos, Etchegoin, and San Joaquin Sandstone ~*~ jt.,:.;~ Red and Formations to the Pliocene is now generally accepted. The ma­ ::::.:::-:-;-::::::::gray rine faunas of these formations have a Pliocene aspect in terms t~t of the succession of Tertiary :fiaunas on the Pacific Coast. The f~-~- vertebrate evidence now known is not opposed to this Conglomerate ~~~ :::Y and assignment. 200 SUBSURFACE EXTENT VERTICAL SCALE In the subsurface of the Los Banos-Kettleman City FIGURE 5.-Sections of strata in the Jacalitos Formation. area approximately south of a line extending from A. Section a-a', strata exposed near Martinez Creek, sec. 20, T. 18 S., Arroyo Hondo to the town of Cantua Creek, electric R.15E. B. Section b"'-b"", strata exposed near Cantua Creek, sec. 2, T, 18 S., logs indicate that possibly as much as 500 feet of con­ R.14E. tinental deposits of the J acalitos F"ormation overlies the Miocene section. In the subsurface at Kettleman North of Cantua Creek, the J aca.litos consists prin­ Hills, Goudkoff (1934, p. 440). differentiated the Jacali­ cipally of dull-green, gray, and tan slightly sandy silt. tos into seven zones on the bases of faunal and lithologic The color banding, so conspicuous farther south, is sub­ evidence and noted a distinct break in deposition at the dued here, owing to lesser amounts of contrasting red base. silt in the section. Gravel and sandstone are present in The relation of the subsurface J acalitos to the surface small amounts. The base of the formation is marked by section is illust!'ated on plate 4. On geologic section 0-0' a slightly gravelly gray to tan sand or sandstone. Opal­ the Jacalitos, which is 375 feet thick where it crops out, ized wood fragments were observed but not in amounts is shown dipping 18° toward the valley. On section comparable to the area farther south. About 3 miles D-D', parallel to 0-0' and about 8 miles southeast, the north of Arroyo Hondo, the coarse gravelly sand at the S acalitos dips 33° and is about 1,800 feet thick. Electric base of the Jacalitos fills root or worm holes that ex­ logs of oil exploration holes indicate th~t in the San tend into the underlying Miocene strata. Joaquin Valley proper to the east, the top of the J acali- E16 MECHANICS OF AQUIFER SYSTEMS tos Formation is at a maximum depth of slightly more tion rat six places between Anticline Ridge and Tumey than 4,000 ff,et. Gulch rare shown in figure 6 (A -F). Two of these sec­ tions (fig. 6A, B), both of which span the full exposed ETCHEGOIN FORMATION (PLIOCENE) thickness of the Etchegoin Formation, illustrate its The Etchegoin Formation was named hy F. M. An­ lithologic character between Anticline Ridge and the derson (1905, p. 178} for its exposure near the old Coalinga-Fresno Road. Here, the Etchegoin is pre­ Etchegoin Ranch in NW~4 sec. 1, T. 19 S., R. 15 E. dominantly gray, brown, and red silt and sandy silt, Arnold and R. E. Anderson (1910, p. 114} defined the wi:th thinner, but massive, beds of brown and blue Etchegoin Formation as sandstone. the succession of beds of sand, gravel, and clay, in part in­ Between the Coalinga-Fresno Road and Cantua durated, occurring in the oilfield northeast of Coalinga above Creek, the Etchegoin Formation is characterized by beds the base of the hill-fonning sandstone beds referred to for con­ of massive blue sandstone and banded sandy silt. Near venience as the Glycymeris zone, and in the Kettleman Hills Cantua Creek, the blue sandstone grades into brown below the fresh-water beds described as the base of the Tulare Fonnation. sandstone interbedded with light-brown, tan, and gr·ay silt (fig. 60) ; blue sandstone is not found north of They did not attempt to define the top of the formation Cantua Creek in the Etchegoin Formation. in the hills north of Coalinga owing to the "indefinite­ ness of the line between the Etchegoin and the Tulare From the Coalinga area northward to about 3 miles there." In the Kettleman Hills, Woodring and others north of the Coalinga-Fresno Road, the base of the (1940, p. 28) placed the Etchegoin below the San Joa­ Etchegoin is marked hy the Glycymeris zone; this zone quin Formation, whose base was drawn at the base of can be traced as far north as NW% sec. 35, T. 18 S., R. the Cascajo Conglomerate Member. South of State 15 E. North of there to Salt Creek, the base is taken as Highway 198 on Anticline Ridge the contact between the base of the blue sandstone that lies directly over the Glycymeris zone :farther south. 'Between Salt and the Tulare and Etchegoin is indefinite, but to the north, Cantua Creeks, the base is taken ~as the bottom of the the contact is relatively easy to delineate with the use of aerial photographs. On photographs, features such as lowest persistent blue sandstone. topographic expression, color (contrasts of dark and Just south of Cantua Creek, the Etchegoin can he light}, and overlap of one formation on the other helped divided into three lithologic units. A section measured to delimit the two formations. 0.3 mile southeast of Cantua Creek (fig. 60} illustrates the threefold lithologic subdivision in that area. The EXTENT upper unit is mostly yellow to light-tan silt with thin The Etchegoin Formation is exposed discontinuously stringers of gravel. Below this lies a middle unit of in the foothills from the southern end of the San brown arid blue sandstone and gray to reddish-gray Joaquin Valley to a point about 2 miles north of silt, with blue sandstone at the top and ibase. The lower Panoche Creek. Where mapped for this investigation, unit consists predominantly of gray siJt with red and its outcrop forms a band that averages slightly more tan handing. than 1 mile in width. The basal part of the formation is Between Cantua Creek and Arroyo Hondo, the sec­ not exposed in the Kettleman Hills or on the southern tion consists chiefly of sandy silt with relatively thin part of Anticline Ridge, where erosion has failed to cut lenses of sandstone, gravel, and silty sand. The silt beds through to the base. North of the- Coalinga-Fresno display prominent color banding of red, tan, brown, Road, the uppermost part is not exposed because of over­ and gray. The sandstone and gravel are usually gray lap by the Tulare Form-ation. or grayish brown. Definite evidence of overlap of the Etchegoin by the Tulare Formation is present north LITHOLOGY of Cantua Creek; therefore, the base of the Tulare was In the North Dome of Kettleman Hills, the exposed used as the -contact between the two formations. Etchegoin strata consist chiefly of brown silty sand and The Etchegoin characteristically contains ·an exten­ sandy silt wi:th lenses of blue sandstone. About 6 miles sive basal gravel and sandstone between Cantua Creek north of Coalinga, the Etchegoin, the base of which is and Arroyo Hondo. Just north of Cantua Creek this marked by the Glycymeris fossil zone, consists of beds basal bed consists of interbedded gravel and gravelly of compact coarse and fine bluish-gray silty sandstone sandstone about 20 feet thick containing cobbles as much alternating. with zones of pebbly sand, fine gray sand' as 6 inches in diameter. This bed thickens northward silt, -and clay. The clay increases upward in the section and, in the vicinity df Arroyo Hondo, is about 80 feet (Arnold and Anderson, 1910, p. 117}. thick. A sootion measured across the full outcrop of the Measured seotions of strata in the Etchegoin Forma- Etchegoin 0.1 mile southeast of Arroyo Hondo (fig. COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E17

6D) shows this basal gravel which there includes two brown friable arkosic sandstone, a sequence of greenish­ interbeds of sandy silt. In many places the basal gravel gray clayey siltstone and sandstone, and a cros8bedded contains ~a large amount of secondary gypsum in the arkosic sandstone, the highest exposed bed. form of crack and cavity fillings. The lithologic compo8ition of gravel throughout the THICKNESS, MODE OF ORIGIN, AND STRATIGRAPHIC RELATIONS Etchegoin Formation is fairly constant. Fragments The exposed thickness of the Etchegoin is not constant consist mostly of fine-grained igneous and metamorphic because of the unconformable contact at the base and rocks, white quartz, chert, and jasper. Less common progressive overlap of the Tulare Formation at the top. constituents are fragments of older resistant sandstone Measured sections at six localities (fig. 6) indicate that and shale, fossils reworked from Miocene strata, and the exposed Etchegoin thins from south to north. At concretions from Cretaceous sandstone. State Highway 198 the thickness exceeds 2,000 feet, but From Arroyo Hondo northwest about 6 miles to a near Tumey Gulch, 30 miles northwest, it is less than point in the hills opposite Panoche Junction, the Etche­ 500 feet, and near Panoche Creek, it is only a few tens goin becomes more gravelly and sandy. The upper part of feet. is predominantly banded silt but contains much more The Etchegoin Formation is partly marine and partly sand and sandstone than farther south. The basal gravel fluviatile and lacustrine in origin. Marine fossils are thickens, and, in sec. 14, makes up about a quarter of absent throughout much of the formation north of Anti­ the formation thickness, as indicated in section F'-F" cline Ridge but are abundant in the Kettleman Hills ('fig. 6E). (Woodring and others, 1940, p. 55). North of Anticline Between Panoche Junction 'and Tumey Gulch, the Ridge, many of the sandstone and grayel beds contain Tulare Formation progressively overlaps and conceals fossilized bones of terrestrial animals and are doubtless the upper Etchegoin strata. Silt and sandy silt still of continental origin. Rock constituents of the clastic persist as the major constituents of the Etchegoin, but sediments indicate that the source of the Etchegoin was the proportion of sandy material is greater than farther the older rocks of the Diablo Range farther west. south. The basal part of the Etchegoin grades from Angular discordance between the Etchegoin and J aca­ gravel near Panoche J un

B ~ Gray

..o··.:_·; __ ::: Brown Yellow ~-~~::·:~::O~.:·i:::_~.~:. White :+: Gray [ti:ili Greenish t:'~~ .. Reddish gray ~~~. ill

Iii Blue Gray Light gray I :.:..:.=.:..:.. Gray

White I li Greenish gray I. ""' Brown ···-·· Light :..:..:.':"":"'7.:..:..: gray

Red and ~ gray I Gray ::::-:~=~:_.·=-:--::·::::===-_:__·::::·: ~E~ Light -:~ brown and iron il_:·.:;i_: stained Gray ·=~:· -

Light Gray brown Gray l_l_:·_c_:_._l:_!_ii.• :~: II! ~§~

li Tan Glycymeri.~ zone

Red and green Tan II Ill Blue FEET Gray 0

Blue Light gray :.:,:;.:.;;...;if: Glycymens zone Brown

Gray

100 VERTICAL Iron-stained SCALE II FIGURE 6.-Sections of strata in the Etchegoin Formation.

A. Section c-c,. strata exposed along State Highway 19R, S{'{'. 30, T. 19 S., R. 16 E. and sees, 25 and 26, T. 19 S., R. 15 E. B. Section d-d', strata exposed along Coalinga-Fresna Road, sec. 7, T. 19 S., R. 16 E. and sec. 12, T. 19 S., R.'15E. C. Section b"-b"', strata exposed near Cantua Creek, sec. 35, T. 17 S., R. 14 E. and sec. 2, T. 18 S., R.14E. COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E19

D E F c A A ) Gray (~~~ Red to 000 gray; ,0:, .. .·.·;·. Yellow Yellow wood .... and Red bones ::it Yellow Gray il·~~{ ~~~~~- ::;·.:.: :; Brown ~:-:-;:!! Yellow Ill·~c;·~ Light Gray co grayish ~ tan Light Greenish gray Gypsum yellow 00000 .... ~*~ -~fo/.:~ Yellow Gray SB~ Blue Greenish gray O'Ci"' to c;~;o Light tan :J~tt Yellow ~ gray; II .. !:!..;..;.~ Greenish gray gypsum ~··~·~· Q) ~~ij and Q. ~~::;:: some silicified Q. ~±::~ bones Light olive ~ tt:~ gray Light Gray tan

#:~§ Light ~::;.j. Bluish tan gray Yellow Red II Variegated Tan

Gray; bone fragments Dark gray Blue Reddish and yellowish tan Ill Gray Light tan Light gray Tan to Bluish gray Light gray gray; and brown abundant i~~ 0• 0. Dark gypsum Gray brown

: ~(~\~ Blue c:: ::::::::::: :J ::::::::::: Tan to :-:-:-:-:-: reddish -Q) :::::::::::.·.·.·.·.·. Brown ""0 ::::::::::: ""0~·;:;~ Gray ;~E~t il Reddish m~.~ gray ;.·~:-: Greenish H~E gray Blue to Brown li Gray Ill

D. Section e'-e" strata exposed near Arroyo Hondo, sees. 9 and 10, T. 17 S., R. 14 E. E. Section!'-!", strata exposed near Panoche Junction, sees. 14 arid 23, T. 16 S., R. 13 E. F. Section g'-g", strata exposed near Tumey Gulch, SW%.NE%,, sec. 1, T. 16 S., R. 12 E. E20 MECHANICS OF AQUIFER SYSTEMS

The Etchegoin is differentiated near the western end THICKNESS AND STRATIGRAPHIC RELATIONS of three of the transverse geologic sections (pl. 4). How­ The San Joaquin Formation is 1,200-1,800 feet thick ever, it is not differentiated beneath most of the valley where it is exposed on the flanks of Kettleman Hills proper because of lack of subsurface stratigraphic infor­ (Woodring and others, 1940, ·P· 28). In the Guijarral m~tion. On the basis of electric logs alone, the Etche­ Hills, where i1t is concealed .beneath the Tulare Forma­ gmn cannot be reliably distinguished from the tion, the San Joaquin Formation consists of sand clay underlying and overlying deposits, which in much of and conglomerate and is 1,700 feet thick (Hunter,' 1951, ' the area are lithologically similar to the Etchegoin. p. 15). Kaplow (1942, p. 22) concluded that on Anti­ SAN JOAQUIN FORMATION (PLIOCENE) cl~ne Ridge along State Highway 198, exposu;es of clay EXTENT with sand streaks, 1,570 feet thick should he assigned to the San Joaquin. The San Joaquin Formation, which is extensively exposed at Kettleman Hills and underlies the southern No angular unconformities or major disconformities part of the Los Banos-Kettleman City area, contains the are recognized wt either the base or the top of the San uppermost marine strata in the San Joaquin Valley. Joaquin in the Kettleman Hills. This fact suggests that F. M. Anderson (1905) first described the "San Joaquin the Etchegoin, San Joaquin, and Tulare Formations of the Kettleman Hills were },aid down during a time clays" from the Kettleman Hills, but he did not desig­ of relatively continuous deposition. However, north of nate a ty'Pe locality. Barbat and Galloway (1934) pre­ Oantua Creek where distinct unconformities mark the sente~ ~he fir.st definitive paper o~ the "San Joaquin contact~ between the Jacalitos, Etchegoin, and Tulare Clay, Includrng the first designatiOn of a type section FormatiOns, folding and erosion evidently interrupted and a type locality for the formation. Woodring and 1 the depositional sequence. Thus, it seems that deforma- others (_1940, p. 27) changed the name to San Joaquin 1 tion in the Kettleman Hills began somewhat later than ~ormation· and ~uggested a section along Arroyo Hondo that in the foothills north of Oantua Creek. In Kettleman Hills as a standard section. In this report, th? San Joaquin is distinguished only in the Kettleman woodring and others ( 1940, p. 103) assigned the San !fills, as mapped by Woodring and others (1940), and Joaquin Formation to the upper part of the Pliocene In the su~urfu.ce. On Anticline Ridge, the upper part on the basis of vertebrate and m·arine invertebrate of :What Is mapped as Etchegoin on plate 1 may be fossils. equivalent to the San Joaquin Formation of the Kettle­ SUBSURFACE EXT.ENT ~an Hil_ls. Th~re is, however, no readily distinguishable In the Los Banos-Kettleman City area, the UJpper­ lithologic basis for separation. A detailed study to try .;most stratum in which the pelecypod Mya is recognized, to resolve this problem was not within the scope of this has generally been taken as the top 6f the San ,Joaquin field mapping. Formation. This so-called upper Mya zone was cored LITHOLOGY in seve:ml exploratory holes drilled in the vicinity of Westhaven in 1929 .by the Shell Oil Co. 2 By correlating The most apparent lithologic feature of the San this lithologic horizon on electric logs, the San Joaquin Joaquin Formation as ex.posed on Kettleman Hills is Formation has been differentiated from the overlying the predom_inance of fine-grained materials-silty Tulare Form.ation in the southern ,part of geologic sandstone, silt, and clay. On weathered surfaces the section A-A' (pl. 3). The 500-700 feet of fresh-water­ unit appears to consist mostly of clay, hut fresh expo­ bearing sand and interbedded clay underlying the sures show that silt and silty sandstone make up much Tulare Formation ·and indicated ·as littoral or estuarine of the form3!tion. Many beds show pronounced litho­ deposits on the southern .part of geologic section A-A' logic changes along the strike. However, the basal stra­ ·are considered to be .a shoreline phase of the San J oa­ tum of the formation, the :Casoajo Conglomerate Mem­ quin Formation. Many deep wa;ter •wells in the south­ ber, was mapped by Woodring and others (1940) over a large part of the Kettlem·an Hills. western pait of the Los Banos-Kettleman City area are The San Joaquin Form.a;tion is of mixed continental perfovated in these strata, which are highly permeable, and marine deposition. Much of the fine material ap­ and are presently an excellent source of ·water. (See pears to be nonmarine, ·and the rem,ains of fresh-water pl. 4, sections D-D', E-E'.) He~, the deposits tenta­ shells and land 1plants have been found in some of them. tively assigned to the San Joaquin Formation are Interbedded sandstones and oonglomerates contain ·much coarser and more permeable than those on Kettle­ marine fossils. Thus, the San Joaquin Formation was man Hills. probably deposited during •a time of fluctuating sea 2 Shell Oll Co., 1929, "Results of Core Drilling on the Boston Land Co. level. Property," unpubllshed report. COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E21

TULARE FORMATION (PLIOCENE AND PLEISTOCENE) Pliocene shown on plate 1. Boulders, however, are rus The alluvial deposits forming the Tulare Formation much as 3 feet in diameter. The occurrence of these cob:ble and boulder gravels were first described by W. L. Watts ( 1894, p. 55, 67) and later assigned the name Tulare Form3!tion by F. M. suggests that they once were latevally extensive and later were largely removed by erosion. Their distribu­ An~erson ( 1905, p. 1'81-182). No type locality was tion and st~atigraphic position are similar to thrut of design,ruted for th~ Tulare Formation by Anderson, but the Tulare Formation in .the Panoche Hills, suggesting the Kettleman Hills have been regarded generally as a possible correlation with the Tulare; however, a the type region, and Woodring has proposed the east definite correlation is not pr,acticable. side of northern North Dome on La Cej a as the type On Anticline Ridge, the contact between the Tulare locality (Woodring and others, 1940, p. 13). Woodring and underlying deposits here included in the Etchegoin pl.aced the base df the Tulare just above the youngest Formation is difficult to locate on the ground, and the widespread m·arine deposit constituting the upper M ya contact shown on .plate 1 was delineated on aerial photo­ zone of the San Joaquin Formation. The Tulare con­ graphs on the basis of soil ·and vegetation differences. formably overlies the San Joaquin Formation in the North of this area, the base of the Tulare is generally Kettleman Hills, but, where exposed elsewhere in the recognizable on both the ground and aerial Diablo Range, it rests unconformably on Pliocene and photographs. older formations. The top of the Tulare Formation by At most places, the uppermost exposed part of the definition is the bound·ary between th~ uppermost de­ Tulare may be differenti,ated easily from the overlying for~ed or tilted strata and the overlying alluvium, alluvium hy angular discordance. Where the discord­ whiCh can be mapped with fair accuracy along most of ance is small, the relatively more consolidated Tulare the outcrop of the Tulare as shown on plate 1. generally is more resistant to erosion and can be

SURFACE EXTENT distinguished from the alluvium by its more pronounced topogra.phie expression. The Tulare Formation ex·tends almost continuously from the southeast to the northwest edge of the area LITHOLOGY shown on plate 1. Its outcrop averages less than 1 mile Fron1 Anticline Ridge to Cantua Creek the Tul,are in width and at only a few places exceeds 1 mile. Nota­ Form,a;tion consists of beds of poorly sorted sand, ble exceptions are in the Guijarral Hills, 'between gravel, and si1lt with a few interbedded lenses of well­ Tumey Gulch and Panoche Creek, along Li,ttle Panoche indurated sandstone ,and siltstone. The basal zone, Creek, and in the vicinity df ·Ortigalita Creek where where fine grained, generally is somewhat limy. In broad outcrops result from gentle dips in the Tulare. much of this area the basal zone consists of coarse In addition to the narrow strip that borders the foot­ gravel or gravel and sandstone. The coarse basal sedi­ hills, the Tulare also caps some isolated hills north of ments commonly contain many secondary gypsum veins. Anticline Ridge, but most of the individual exposures are too small to show on plate 1. At one time the Tulare Conspicuous dip slopes, generally formed on the more resistant lower members of the Tulare, ;are found in may have formed ·a broad blanket across most of the several pl,aces 'between Domengine and Cantua Creeks. present foothill·area. Deposits suppor:ting these slopes locally contain sand­ In the North Dome of Kettleman Hills the Tulare stone concretions, as large as 2 feet in diameter, consists principally of sand, much of whlch is silty, pebbly, and crossbedded; it contains some gravel ap­ reworked from Cretaceous rooks to the west. paren:tly laid do~n as stream deposits. The lower 'part Measured sections of strata in the Tulare Formation contams some thin-bedded fine sediments that are inter­ at seven places between Oantua and Little P~anoche preted ~~ lake de~osits. 'In the Kreyenhagen, J acalitos, Creeks ,are shown in figure 7 (A-G). Section b-b' (fig. and GIDJarral Hills, the exposed 'Tulare is predomi­ 7 A) illustra.tes the lithologic character of the Tulare nantly coarse gravel. Formation 'as exposed on the south flank of Cantua L~ ~avels which probably are remnants of high Creek valley. depos1ti~:mal terraces, are found soattered over hilltops Between Oantua Creek and Arroyo Hondo the base underlain by the Etchegoin and J acalitos Formations of the Tulare is marked lby a layer of locally concretion­ from near Domengine Creek north to Arroyo Ciervo. ary well-indurated light-grayish-brown sandstone Individual exposures are not large enough to map and about 15-20 feet thick. At several places north of at some places consist only of a few cobbles or boulders. Cantua Creek, the basal sandstone is overlain by •a bed Lithologically, the rock constituents ~are about the same of hard reddish-tan marl. This lower marl is not found as those in gravels of the Tulare Formation and older at Arroyo Hondo but is common near the base of .the E22 MECHANICS OF AQUIFER SYSTEMS

A B c Tulare farther north. The remainder df the formation =;:i =-:=-:-~ is predominantly sandy silt containing thin stringers Gray ¢f.~ £:~.!i of gravel !and sandstone. Section e-e' (fig. 7B) shows the lithology of the

~~~:"":"':';..;.,;':7' Tulare Form·ation exposed along the south side of ~~~ ~~ht Arroyo Hondo. ~jj:~ gray -··-;-;.:..:a; Between Arroyo Hondo and Panoche J unc·tion the E;~:E Marl; bone basal part of the Tulare Formation becomes gravelly tt:t~ fragments (fig. 70) and commonly contains cobbles as large as 6 inches in diameter. T-he gravel constituents are about the same as those of gravels in the Etchegoin-igneous qu~rtzite, :...._• .. ".-....: and metamorphic rocks, ·chert, whi·te quartz, siliceous shale, and large oyster shells reworked from :.:-:-:-:-: Brownish 0 00 Iii :~..:.7::..:. Yellow ~~:j gray the Miocene strata. Abundant secondary gypsum fills 000 iti 0• •. =:::::::::Yellow ::::=::<: Tan to brown; -c:>- the interstitial openings in the gravel. Above the base c;-oc; ~ concretions oo :-:··o· the formation consists of poorly consolidated ·inter­ 0 00 ~~ ~~~eto bedded sandy and gravelly silt, as shown by section ~ ~:a f-1' (fig. 70) of the Tulare Formation near Panoc~e :::0:.:.; Grayish ~a;.,~~~ tan Junction. In part, this silt is moderately to highly ;c:}:o: calcareous. Between Panoche Junction and Tumey Gulch the coarse basal bed df the Tu}are Formation thickens and D F grades into a light-tan silty gravel and sand (fig. 7D). -o- ~~~ Reddish Gravel constituents are the same ·as described above, ~~g brown but .they also include olivine-basalt and sandstone :.~8 fragments. Strata in the upper part of· the section, par­ ticularly the uppermost exposed layer, appear to con­ tain a large amount of gypsite. It is uncertain whether G j~·::: White the gypsite is within the Tul!are Formation or is an d ~ ti Red brown to eV1aporite deposited on the slightly eroded Tulare sur­ a' b'o--.3 greenish gray o..:...:;; )OOO =:~~= Olive green to .face, and therefore it is not included in the measured ~Eo~ ~:;~;ish gray section shown in figure 7D. St..cr'~ -~ ~~~ tan In the Tumey and Panoche Hills, the Tulare Forma­ ~;~~ ;.~ ~ Grayish tion consists of clayey and siltly sandstone ·and siltstorte ~~-~ ~:j~ tan ~~~ interbedded with pebble conglomerate ·and unconsoli­ d·ated sand. The conglomerate heds are lenticular and ~~~~ FEET 0 grade laterally into sandstone. The gravel fragments are mostly of igneous and volcanic rocks, shale chips, and glaucophane schist; in addition, the basal con­ glomerate contains fragments of limy brown sandstone. The basal gravel grades northward into finer mate­ rial until, at Little Panoche Creek, the basal zone is

100 about 90 percent marl or marly silt with thin gravel VERTICAL stringers. The gravels are predominantly igneous and SCALE metamorphic rock fragments, but, locally, they con­ FIGURE 7 .. -Sections of strata in the Tulare Formation. tain sandstone concretions as large as 3 feet in diameter A.. Section b-b', strata exposed near Cantua Creek, sees. 35 and 36, 1 T. 17 S., R. 14 E. reworked from Cretaceous rocks. Gypsite is common, B. Section e-e', strata exposed near Arroyo Hondo, sees. 3 and 10, but as farther south, its exact age and its position in the T. 17 S., R.14 E. a. Section 1-/', strata exposed near Panoche Junction, sees. 12-14, T. 16 S., R. 13 E. D. Section g-g', strata exposed near Tumey Gulch, sec. 31, T. 15 S., F. Section h"-h"', strata in middle part of Tulare Formation exposed R. 13 E., s-ec. 6, T. 16 S., R. 13 E., and sec. 1, T. 16 S, R 12 E. near Little Panoche Creek, NE*SW%, sec. 20, T. 13 S., R. 11 E. E. Section h-h', strata in upper part of Tulare Formation exposed G. Section h""-h""', strata in lower part of Tulare Formation exposed near Little Panoche Creek, SE;4NW*, sec. 21, T. 13 S., R. 11 E. near Little Panoche Creek, NE*NW%, sec. 31, T. 13 S., R. 11 E. COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E23

section are somewhat in doubt. 'At most places, however, Kettleman Hills, the maximum exposed thickness is the gypsite appears to be either in the uppermost ex­ about 2,600 feet. North of Coalinga, the thickness in posed Tulare or to be an evaporite deposited on a measured seotions (fig. 7) _does not exceed 350 feet and slightly eroded Tulare surface. The columnar sections in ·most .places is less than 300 f~. of figure 7E -G show the lithologic character of strata The exposed Tulare consists m·ainly of .alluvium de­ in the upper, middle, and lower parts, respectively, of posited on the post-Etchegoin erosion surface. How­ the Tulare Formation near Little Panoche Creek. ever, calcareous beds and clay strata of considerable In his report on the Ortigalita Peak quadrangle, lateral extent indicate that locally it is of lacustrine Briggs ( 1953, p. 46) assigned the name Oro Lorna For­ origin. The processes of deposition prob81bly •were mation to a narrow unit of continental deposits exposed similar to those that currently are forming alluvial-fan, along the front of the Laguna Seoa Hills, extending flood-plain, and lake-bed deposi'ts on the west side and northwest for a;bout 6 miles nearly to Ortigalita Creek in the trough of the San Joaquin Valley. and dipping at angles as much .as 40° under the allu- In the southern part of the area, the Tulare >appears to -viurn. He concluded th8Jt these beds were lithologically rest conformably on the ~San Joaquin and Etchegoin and structurally distinct from, and older than, relatively Formntions. North of Cantua Creek, aerial photo­ fl8it-lying deposits to the south near Little Panoche graphs show defini,te evidence of overlap of the Tulare Creek, which he mapped as Tulare Formation. on the Etchegoin, although this relationship is not obvi­ In 1961 the Bureau of Reclamation drilled several ous on the ground. Numerous strata of the Etchegoin, core holes in connection with foundation studies for a indistinguish31ble on the ground hut traceable on aerial pumping plant for the San Luis .project about 3 miles photog~aphs, are progressively overl~pped to the north­ south of Ortigalita Creek ·and ubout a quarter of a mile ward by the Tulare. From the vicinity of Tumey Gulch from the foothills. A diatomaceous silty clay 3~ feet northward, angular discordance between the Etchegoin thick penetrated in these test holes has :been identified as and Tulare Formations is apparent in the field and in­ the Corcoran Clay Member of the Tulare Formation, on dicates pronounced pre-Tulare deformation. As already the basis of the presence of diatoms, lithologic similar­ noted in the discussion of the Tulare in the Laguna ity, and the known subsurface occurrence of the Cor­ Seca Hills, some deforma,tion evidently occurred there coran Cluy Member to the east (I. E. Klein, U.S. Bur.· during Tulare time. Furthermore, the steep dip of the Reclam®tion, written commun., May 1962). The core Tulare beds along the front of these hills demonstrates holes ·also ·Were the basis for extension of the Corcoran pronounced post-Tulare deformation. South of the to the outcrop of a gray silty clay in the foothills dip­ Tumey Gulch area, all exposed sections of the Tulare ping 30°-50° .toward the valley (Carpenter, 1965), ·are ti1ted, suggesting post-Tulare folding in tha,t ~area which had been mapped by Briggs (1953, p. 47) as the also. uppermost unit of his Oro Lorna Formation. Where ex­ The age of the Tulare Form·rution has been -a subject posed, the gray silty clay is. underlain conformably by of disagreement among geologists for many years and several hundred feet of reddish-gray gravel, silty sand, it is still in dispute. The dispute involves also the posi­ and silt, stratigraphically above the San Pablo Forma­ tion of the Pliocene-Pleistocene boundary in the •Coast tion. The gray silty cl.ay (Corcoran Clay Member) and Ranges :and the geomor,phic development of the present the underlying gravelly deposits are therefore shown topography of the Sierra Nev,ada. ·Discussion of these in the Tulare Formation on plate 1. problems is beyond the scope of this report; however, The steeply dipping Tulare along the front of the direct evidence on the age of the Tulare is pertinent. Laguna 'Seca Hills appears to be unconformable rwith Direct evidence on :the age of the Tulare in and near gently dipping beds to the south near Little Panoche the study area includes a fresh-water molluscan'faunain Creek and to the north near Ortigalita Creek, •which the basal part of the Tulare exposed ·at Kettlemmi Hills, were mapped by Briggs as Tulare Formation and have which has also been cored at several points in the San been so m·apped on plate 1. Working out the d~ailed Joaquin Valley; di·atom floms from the basal part of field rela;tions was not practicable within the scope of the Tulare Formation exposed :at Kettlemun Hills ,and this study, but, evidently, beds of different ages sepa­ from the Corcoran Clay Member of the Tulare Forma­ rated .by an unconformity are included in the Tulare tion cored at many places in the valley; potassium-argon Form.ation from Little Panoche Creek to Ortigalita dating of .a rhyolitic •ash bed exposed near Friant which Creek as mapped on plate 1. has been correlated with volcanic ash just overlying the Corcoran Clay !Member; and fossil mammal 'bones ex­ THICKNESS AND STRATIGRAPHIC RELATIONS cavated from the Corcoran ·Clay 'Member in the San The exposed Tulare Formation ranges widely in Luis project canal section of the Californi1a Aqueduct thickness. On the west side of North Dome in the in 1964. E24 MECHANICS OF AQUIFER SYSTEMS

According to Woodring ~and others ( 1940, p. 104), the coran, and at least part of the Tulare beneath the Cor­ lower .part of the Tulare Formation in Kettleman Hills coran is of Pleistocene age. As shown on geologic section contains the largest fossil fauna of fresh-water mollusks A.-A.' (pl. 3), the part of the Tulare Formation under­ known on the Pacific coast. On the basis of study of this lying the Corcoran Clay Member attains a thickness of fossil assemblage (.p. 22-26), Woodring concluded ( p. 2,500 feet near Tulare Lake bed (south end of section 104) that "assignment to the upper Pliocene is consist­ A.-A.'). A substantial part of this 2,500 feet of pre­ ent with the character of the fauna." Corcoran Tulare doubtless is of early Pleistocene age, Dwight Taylor (oral commun., 1963), who has but data are not available to define the position of the studied the fresh-water mollusks from the Tulare, con­ Pliocene-Pleistocene boundary in these str81ta. cluded that- the fresh-water mollusks indica,te that the basal Tulare in the SUBSURFACE CHARACTER Kettleman Hills i·s equiv•alent to the lower part of the Santa Clara. Formation of the Santa CLara Valley and to some part In the subsurface, sediments derived from the Diablo of the Tehama Formation of 1the Sacramento Valley. On the Range interfinger with, and grade into, sediments de­ basis of present knowledge, it is convenient to assign this se­ rived from the Sierra Nevada. The eastern source quence to the Pliocene. arkosic sediments may be equivalent to part of the In the upper part of the Tulare, near Little Panoche · Kern River Formation of Diepenbrock (1933), which Creek, he concluded that fossils suggest :a Pleistocene is exposed in the foothills adjacent to the southeastern .age ( writte~ commun., January 1962). part of the San Joaquin Valley. However, no attempt K. E. Lohman (1938) assigned the basal Tulare to was made to assign •an eastern boundary to the Tulare the Pliocene on the basis of diatom studies. Di·atom Formation on the geologic sootions. floras studied by Lohman from the Corcoran Clay Mem­ The Tulare Formation consists of deposits laid down ber (report on referred fossils, February 1954) resemble in a fresh-water environment, and it underlies all of the the assemblage from the basal Tulare much more than Los Banos-Kettleman City area. As discussed above, it they do numerous Pleistocene collections from the crops out nearly continuously along the eastern slope Western States (oral oommun., 1963). From this, of the Diablo Range where it is poorly- to moderately Lohman concluded that at .the youngest the Corcoran is consolidated. probably no later than early Pleistocene. The top of the Tulare Formation in the subsurface A volcanic ash exposed near Friant in eastern Fresno in the Los Banos-Kettleman City area is not definable County •and correlated with volcanic ·ash just overlying because the boundary between the uppermost tilted the Corcoran Clay Member was dated at 600,000-+- strata and the overlying alluvium in the outcrop area is 20,000 years by G. B. Dalrymple (in Janda, 1965). The a feature that cannot be recognized in wells in the San potassium-·argon date demonstrated that the upper part Joaquin Valley. In fact, beneath most of the Los of the Tulare Form·ation is of Pleistocene age. Banos-Kettleman City area, the deposits between the In 1964, fossil m:amm·al bones ·Were recovered by Corcoran Clay Member and the land surface presuma­ Bureau of Reclamation geologists from the Corcoran bly are conforma;ble -and thus the criterion used at the Clay Member during excavation of the San Luis project outcrop does not even exist beneath most of the valley canal section of the California Aqueduct (Carpenter, a·rea. Furthermore, .these deposits, which are as much 1965, p. 143). These bones were found :about 5 miles as 900 feet thick, are almost entirely of alluvial-fan southeast of the Dos Amigos pumping: plant, in NW%,, and flood-plain origin. Although the topogvaphic axis sec. 28, T. 12 S., R. 11 E., at a depth of 25-30 feet below migrated eastward during post-Corcoran time, as shown the land surface (R. E. Trefzger, oral commun., Au­ by the gradual eastern extension of Dia;blo Range gust 1967). The assemblage, which included remains source materi·als, there is no marked c4ange in physi­ of mammoths, camels, and E quus, has been ex,a·mined by cal character or other criterion that can be related to Dr. J. E. Mawby; he reported (written commun., July the top of the uppermost tilted beds that define the top 1967, to J. F. Poland) that the mammoths identify of the Tulare in the foothills. For purposes of defining the ·age of the Corcoran Clay Member as Irving.tonian thicknesses in this report, the depth to the top of the or younger. Tulare Formation is arbitrarily assumed to increase According to the Holmes ( 1965) time scale, the eastward from a featheredge at the foothills to about Pleistocene Epoch began 2-3 million years ago. If vol­ 200 feet below the land surface beneath the present canic ash beds just overlying the Corcoran Clay Mem­ valley axis. Obviously, a top so arbitrarily defined in ber are about 600,000 years old, :and the Corcoran is no sense represents a time line. of Irvingtonian (middle Pleistocene) age, then all of The subsurface thickness of the Tulare Formation the Tulare above the Corcoran Clay Member, the Cor- ranges from more than 3,000 feet in the southern part COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E25 of the Los Banos-Kettleman City rarea. to less than 800 criteria, see Meade, 1967, p. C5.) They consist mainly feet locally in the northern part of the ·area. Thus, the df poorly sorted silt, clay, and fine to medium sand. The subsurface thickness is much greater than the thick­ all uvial-fan deposits of Panache :and Los Ga-tos Creeks ness in the outcrop area to the west. are the coarsest; they contain n few layers of medium The Los Banos-Kettleman City area has been pre­ to coarse sand, with some gravel. Although most of the dominantly a region of rapid and nearly continuous material presuma;bly was laid down by intermittent deposition during late Tertiary and Quaternary time. streams, !boulder deposits suggest mudflow origin for Consequently, the fresh-water-bearing sediments un­ parts of the deposits. The alluvial-fan deposits adjacent derlying the valley floor have undergone little weather­ to the Diablo Range foothills can easily be recognized in ing :and reworking. Analysis of core samples indicates well cuttings or cores by their yellowish-brown to brown that very little discernible alteration has taken place color. 'They are calcareous and gypsiferous and locally in the clay minerals since their deposition (Meade, contain· small calcareous concretions, fragments of ser­ 1967, p. C6). Accordingly, oxidized sediments can gen­ pentine, glaucophane schist, siliceous shale, chert, and erally be assumed to be representative of subaerial jasper derived from older rocks to the west. deposition and reduced deposits indicative of subaque­ The bulk of the alluvial-fan deposits from the Dia;blo ous deposition. Range proba-bly was laid down in post-Corcoran time. In its subsurf.ace extent, the Tulare Form·ation has Prior to the deposition of the lacustrine Corcoran Clay been suhdi vided on the basis of drill-log and electric­ Member, the ancestral Los Gatos Creek fan extended log correlations and petrogvaphic analysis of core sam­ 18-22 miles ea;st from the present western edge of the ples, into deposits representing four different types of valley. (See fig. 8; pl. 4, geologic section E-E'.) ·After continental deposition. These include alluvial-fan, the deposition of the Corcoran Clay Member, the Los flood-plain, deltaic, and lacustrine deposits, ns shown in Gatos fan again expanded 18_:22 miles eastward from the geologic sections (pis. 3, 4) and the core-hole logs the western edge of the valley (fig. 9). However, the (pl. 5). Criteri,a that were used to identify the types post-Corcoran alluvial-lfan deposits that extend north­ of deposits have been summarized by Meade (1967, eastward from the western border of the valley in the table 2). The distribution and poorly sorted character central part of the Los Banos-Kettleman City area are of the highly oxidized deposits underlying the alluvial generally more extensive than the older pre-Corcoran slopes near the west border of the valley suggest that alluvial-fan deposits. such deposits accumulated under subaerial conditions The Panache Creek fan in the northern rpart of the similar to those prevailing on the present-day alluvial Los Banos-Kettleman City area is one of rthe largest fans, and therefore they are designruted alluvial-fan modern alluvial fans on the west side of the San deposits. Similarly, the lenticular and interfingering Joaquin Valley, extending 18 miles across the valley reduced fine- to coarse-grained fluvial deposits in the floor from the western edge of the valley. However, trough of the valley rare designated as flood-plain de­ prior to the deposition of the 'Corcoran Clay Member, posits, implying that they were deposited on the ancient ·an alluvial fan of rwestern source extended several miles river flood plain. This general term, "flood-plain de­ east of the !present axis of the valley. The top of a layer posit," embraces channel, overbank, natural levee, as much as 50 feet thick consisting of oxidized deposits back-swamp, and point-bar deposits, most of which derived from rthe Diablo Range was cored below the cannot be differenti:ated in the subsurtface. The lacus­ Corcoran Cl,ay Member at depths below land surface trine deposits, where fossil evidence is lacking, are dif­ of 687 .and 591 feet, respectively, in Bureau of Redamn­ ferentiated from the flood· plain deposits by their high tion core holes 13/15-35E1 (pl. 4) and 13/16-2Cl. A clay content, indicative of a still-water environment, well-developed soil profile has been recognized ·at the the highly reduced nature of the sediments, and their to:p of the western source m·aterials. homogeneity and stratigraphic continuity as indicated WH~ter rwells in the area from near ·Mendota to the by electric logs and drill logs. A few extensive, but thin, edge .of the Panoche Hills commonly bottom in western beds of well-sorted sand, associated with the fine­ source oxidized deposits. The uppermost layer of these grained lacustrine silty clay beds, also have been identi­ deposits probably is a soil horizon heoause it is com­ fied as of lacustrine origin. monly described in drillers' logs as being red or rpink. The location of wells in this ·area that bottom in such ALLUVIAL-FAN DEPOSITS oxidized deposits ure plotted in figure 8. These deposits The alluvial-fan deposits of the Tulare Formation in ·are intey,preted as having been l·aid down on an alluvial the Los Banos-Kettleman City area are derived chiefly fan :that extended fron1 the Panoche Hills east across from source nreas in the Diablo Range. (For source the present valley trough in pre-Corcoran time. E26 MECHANICS OF AQUIFER SYSTEMS

120°30' 120°00'

0 0 0 00 oo 0 0 0 0 0 0

0 0

< 0

EXPLANATION

36°30' ~ Boundary of deformed rocks

----400--- Line of equal thickness of alluvial-fan deposits that occur in the Tulare Formation below the Corcoran Clay Member; dashed where approxi­ mate. Interval 200 feet

Control point from electric log or core log

Location of driller's log or core log for well that entered, but generally did not pass through, oxidized sediments occurring in the Tulare Formation below the Corcoran

Approximate boundary of alluvial-fan deposits derived from the Diablo Range that occur in the Tulare Formation below the Corcoran Clay Member

Approximate western boundary of the Corcoran Clay Member of the Tulare Formation LAKE

0 5 10 MILES BED

120°30' 12o•oo• Base from U.S. Geological Survey Central Valley map,l:250000,1958

FIGURE 8.-Thickness of alluvial-fan deposits derived from the Diablo Range in the Tulare Formation below the Corcoran Clay Member. COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E27

120°30' 120°00'

37"00'

/

36°30' EXPLANATION

~ Boundary of deformed rocks ------200------Line of equal thickness, of alluvial-fan deposits that occur above the Corcoran Clay Member of the Tulare Formation; dashed where approxi­ mate. Interval 100 feet

Approximate western boundary of the Corcoran Clay Member of the Tulare Formation

Control point from electric log or core log

LAKE

BED 0 5 10 MILES

120°30' Base from U.S. Geological Survey Central Compiled by R. E. Miller Valley map, 1:250 000, 1958

FIGURE 9.-Thicknf'ss of alluvial-fan deposits derived from the Diablo Range above the Corcoran Clay Member of the Tulare Formation. E28 MECHANICS OF AQUIFER SYSTEMS

The alluvial-fan deposits underlying the western high mineral content that it is not satisfactory for slope betJween Oantua Creek 'and Anticline Ridge gen­ domestic or irrigation use. (See pl. 4, geologic sections erally are finer grained :and less permeable than similar B-B', 0~0'.) deposits to the northwest or southeast. The alluvial-fan The flood-plain deposits derived chiefly from the deposits derived from the Diablo Range-are of relatively Diablo Range generally have low to moderate ·perme­ low permeabili,ty :and, for this reason, where such de­ abilities. They generally ~are greenish gray to greenish posits form the bulk of the Tulare Formation, irriga­ black and are characterized by an abundance of andesit­ tion wells in parts of the ·area are drilled as deep as ic and basaltic detritus. Locally, they contain moderate 2,500-3,800 feet to tap ·more ~permeB~hle aquifers in the amounts of serpentine, chert, and other rock fragments underlying San ,Joaquin and Etchegoin Formations. derived from older rocks in the Diablo Range. They (·See pl. 4, geologic sootions 0-0', D-D'.) are also slightly to moderately micaceous, in contrast Alluvial-f.an deposits derived from the SieiTa to the generally nonmicaceous character of the ~alluvial­ Nevada that extend subsurface into the northern part fan deposits derived from the DiB~hlo Range. Most of of the Los Banos-Kettlem·an 1City :area (tpl. 4, geologic the western-source flood-plain deposits .are found in section B-B') are composed chiefly of fine to medium­ the northern half of the Los Banos-Kettleman City grained micaceous granitic sand and varying amounts area. of silt and clay. The color of these deposits ranges from Modern near-surface deposits laid down in flood gray to brown. Where the clay content is low, alluvial­ basins by overflow of the .San Joaquin 'and Kings Rivers fan deposits derived from the Sierra Nevada are in the level central floor of the valley consist 1argely of moderately permeable and yield adequate water to irri­ impervious clay ·and clay ·adobe with a texture thwt gation wells. ranges from medium to heavy (Davis and others, 19~59, FLOOD-PLAIN DEPOSITS p. 27, pl. 29, basin soils). In contrast, the flood-plain de­ posits of the Tulare Formation are coarser and contain The term "flood-plain deposit" is used in the present little clay, indicating that the depositional environ­ report in a broad sense to include all reduced fluvial ment was different from the present regime. The com­ de,posits laid down in the valley trough area. parative coarseness of flood-plain sediments in the The flood-plain deposits derived from t:he Sierra Tulare suggests that streams that deposited them were Nevada as described from core samples generally con­ more competent than the modern streams of the same sist of gr:ay ·micaceous or :arkosic sand with interbedded areas. The relatively low clay content of the flood­ micaceous sandy silt ·and cl-ay l-ayers ranging in color plain deposits indicates excellent sorting. from olive brown to greenish blue. The sands generally ~are subangular to subrounded :and have a moderate to DELTAIC DEPOSITS high permeability. As shown by the geologic sections, these deposits ·are extensive below the Corcoran Clay Thick beds of medium to coarse well-sorted sand in Member in the are-a west of Fresno Slough. The thick­ the Tulare Formation in the southern part of .the Los ness :and areal extent of micaceous sands derived from Banos-Kettleman City area are interpreted 1as deltaic the Sierra Nevada that overlie the Corcoran Clay r:Mem­ deposi,ts of extensive lakes. These deposits consist pri­ her are shown in figure 10. This unit, which consists m.arily of bluish- or greenish-gray angular and sub­ angular medium- to coarse-grained arkosic sand with primarily of flood-plain deposits, includes just above the a high biotite mica content. Crossbedding and deposi­ Corcoran a zone up to 200 feet thick conltaining varying tional dips of 10°-40° :and numerous carbonaceous amounts, up to 89 percent hy weight, of rhyolitic vol­ layers are reported in core descriptions of these de­ canic glass and pumice fragments (pl. 3, geologic sec­ posits. Deltaic deposits are differentiated on geologic tion A-A'; pl. 4, B-B', '0-0'). The approximate west­ sections A-A' and E-E' (pis. 3, 4). At the east end of ern boundary of these volcanic deposits is shown in geologic section E-E', sandy deposits beneath the Cor­ figure 10. coran Clay Member, presumably of deltaic origin, are 'The micaceous sands, which form the bulk of the 2,000 feet thick. (See well 19 /20-32R.) Where ta.pped flood-plain deposits from tthe Sierra Nevada, are highly by wells, these thick sands yield abundant water. permeable and yield water freely. In fact, from Tran­ quillity Ito the Kings River and for several miles !West, LACUSTRINE DEPOSITS most of the irrigation wells taJp the micaceous sand The basal deposits of :the Tulare Formation in the above the Corcoran Clay Member. In parts of the Fresno southern and central parts of the Los Banos-Kettlem'an Slough 1area, however, the ·water in the flood-plain de­ City area and nearly all the deposits underlying the posits both :above and below the Corcoran has such a modern Tulnre Lake bed consist of clay, silt, and sand COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E29

120°30' 12o•oo•

37•oo•

/

36°30'

Boundary of deformed rocks ---300--- Line of equal thickness of micaceous sand derived from the Sierra Nevada; dashed where approximate. lntervallOO feet

Approximate western boundary of zone of rhyo­ litic volcanic glass and ash within the micaceous sand

Eastern boundary of Corcoran Clay Member f.'0'0'l t;:;:;:;:;:;:;: Extent of water of high NaCl content in mica­ ceous sand overlying the Corcoran Clay Member

Control point, from electric log or core hole

TULARE LAKE 5 0 5 10 MILES BED

36 •oo·~------12~o~·-3o~.------Base from U.S. Geological Survey Central Valley map, 1:250 000, 1958

FIGURE 10.-Thickness of micaceous sand overlying the Corcoran Clay Member of the Tulare Formation.

411-341 0-71--3 E30 MECHANICS OF AQUIFER SYSTEMS commonly containing lacustrine fossils. These deposits the Corcoran -and land surface in the vicinity of Tu­ are more homogeneous than the flood-plain deposits and lare Lake. A l·acustrine cl-ay about 30 feet thick, 250 feet ~nerally are fine grained, except where intermixed above the Corcoran, and 250 feet below the land sur­ wrth deltaic sands derived from the Sierra Nevada. The face, is shown at the eastern end of section E -E' (pl. lac~strine sediments usually are strongly reduced, 4). This unit has been designated the C clay by Croft. whiCh accounts for their greenish or bluish color and carbonaceous clay and peat layers are common. Thin CORCORAN CLAY MEMBER oxidized layers found in parts of this sequence are A widespread diatomaceous clay stratum, first named generally yellowish brown to reddish orange. as -a separate form·ation by Frink and Kues (1954, p. As shown on geologic sections A.-A.' and E-E' (.pis. 3, 2357-2370), was redefined as the Corcoran Clay Mem­ 4), at least three extensive lake expansions since the ber of the Tulare Formation by Davis (in Inter-Agency retreat of .the late Pliocene sea are recorded in the sub­ Committee, 1968, p. 120). The Corcoran Clay Member surface deposi.ts in the southern part of the Los Banos­ extends beneath the entire Los Banos-Kettleman City Kettleman City area. The initial lake in the basin is area, except in a narrow zone adjacent to the ·hills in the represented hy the basal Tulare sedi•ments which con- southern part of the area where, as shown in figure 11 Sist. of 400-500 feet of sandy lacustrine ·and' deltaic de- and geologic section E-E' (pl. 4), it grades into the posits. Core holes drilled by the Shell Oil Co. 3 in the surrounding deposits. vi~inity of Westhaven indicate that these deposits con­ tain abundant fossils of A.mnicola and other fresh­ The Corcoran Clay Member is the prinCipal confin­ water lacustrine f·auna. Analyses of water from this ing layer !for the artesian system throughout a large interval and electric logs indicate that the water in part of the San Joaquin Valley. The Corcoran is of these lacustrine deposits is now very brackish. very low permeability (Davis and others, 1964, p. 88), On the west flank of North Dome where the Tulare and in 1960 the difference in head in aquifers above and Formation is well exposed, Woodring and others ( 1940, below the Corcoran locally was as much as 200 feet. p. 22) noted small oysters and mussels in a sandstone The Corcoran Clay 1Member was deposited in a fresh­ 1,636 feet above the base of the formation and upward water lake 10-40 miles .wide 'and more than 200 miles to the top of the measured section through a thickness long (D-avis and others, 1959, p. 77; pl. 14). The longi­ of 322 feet of sandstone and conglomerate. About 1,300 tudinal axis of the lake in which the clay was deposited 'feet of apparently nonfossiliferous poorly bedded and was about 5-10 miles west of the present topographic crossbedded yellowish to brownish-gray sandstone con­ axis of the valley. The maximum known thickness of taining conglomerate lenses and a few interbedded silt the Corcoran Clay Member in the Los Banos-Kettle­ layers separate this fossiliferous zone from the upper­ man City area is 120 feet, at -a tplace 5 miles northeast most A. mrn,wola zone in the lower part of the Tulare of the mouth of P.anoche Creek, and beneath Tulare ~orm.ation. The fossiliferous zone described by Wood­ Lake .bed. At hoth places, thickness is based on electric­ nng In the uppermost exposed Tulare Formation on log inter.pretation. As shown in ·figure 11, the thickness North Dome represents a second major l'ake phase. A exceeds 100 feet in several localities. Along the west edge lacustrine deposit is found at a similar position in the of the valley -adjacent to Monocline Ridge and the subsurface northeast of North Dome. It is shown at the Ciervo Hills, the Corcoran is less than 20 feet thick. Its south end of geologic section A.-A.' (pl. 3) 1,200-1,600 exact western extent is difficul,t to delineate because, as feet above the base of the Tulare Formation. This de­ it thins, it bifurcates and its sand and silt content gradu­ posit is about 100 feet thick, and in core holes 20/18- ally increase until it cannot be distinguished in electric 11A and 19/l8-24R (pl. 4) where samples of it were logs from littoral sands that occur along its western recovered from depths of 1,151-1,1'60 feet ·and 1,039- edge. The Corcoran is generally reduced and is greenish 1,050 feet, respectively, ostracodes, A.mnicola and fish blue, except looally along the western border of the Los remains0 were reported. ' Banos-Kettleman City area where it has been uplifted The third and largest lake is represented by the and has :been partially oxidized to brown or red. diatom·aceous Corcoran Clay Member of the Tulare Adjacent to the Panoche and Tumey Hills, the Cor­ Formation, which at core hole 20/18-6B is separated coran is 30-80 feet thick. At core hole 15/12-23Q1 from deposits of the second lake phase by 800 feet of (pl. 4), on the east flank of the Tumey Hills, 35 feet, the western-source alluvium. lower 10 feet of which is diatom·aceous, has been ·assigned Additional' lacustrine deposits df lesser extent and to the Corcoran Clay Member. thickness have been mapped by Croft (1968) between From Tumey Hills northward in the Los Banos­ Kettleman City area, the western edge of the Corcoran 1 Shell Oil Co., 1929, "Results of Core Drllllng on the Boston Land Co. Property," unpubllshed report. ClayMemberhasbeen uplifted (fig.12) .. Finedarksilty COMPACTING DEPOSITS, LOS BANOs-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E31

0

36"30' EXPLANATION /%%%C%CW w Boundary of deformed rocks

----20--- Line of equal thickness of the Corcoran Clay Member; dashed where approximate. Interval 20feet

Approximate boundary of Corcoran Clay Member

Control point from electric log or core log

Note: Where Corcoran Clay Member bifurcates, only the thickness stratum is represented

5 0 5 10 MILES

Base from U.S. Geological Survey Central Valley map, 1:250 000, 1958

FIGUBJI 11.-Thlckness of the Corcoran Clay Member of the Tulare Formation. E32 MECHANICS OF AQUIFER SYSTEMS

12o•oo•

/

-"?o 1-o 0 ~ryr WW C';~ <;,., 36°30' ~L-: ~ Boundary of deformed rocks 0 ----200--­ Structure contour Slwws altitude of top of Corcoran Clay Member of the Tulare Formation. Dashed where approximate. Con­ tour interval 50 feet below mean sea level and 100 feet above mean sea level. Prepared from data available as of 1962

Control point from electric log or core log

Approximate boundary of upper clay stratum of Corcoran Clay Member

Approximate boundary of lower clay stratum of Corcoran Clay Member where upper clay layer is absent

(~~ Area where lacustrine sand deposits along the western margin of the Corcoran Clay Member are in excess of 100 feet in thickness.

5 0 5 10 MILES

120°30' Base from U.S. Geological Survey Central Valley map, 1:250000, 1958

FIGURE 12.-Structure of the Corcoran Clay Member of the Tulare Formation. COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E33

material exposed at ·an altitude of ·500 feet in a roadcut ALLUVIUM (PLEISTOCENE AND HOLOCENE) at the north end of the P.anoche Hills where Little For practical purposes, the entire post-Tul·are section P.anoche Creek enters :the San Joaquin Valley may in the San Joaquin Valley is grouped in this report into represent the Corcoran. The material consists of ~wo a single uni~lluvium-which includes stre~-laid grayish-green silt straJta; the upper, about 1 foot thick, and still-water deposits ranging in a.ge from Pleistocene and the lower' 4 feet thick. The upper stratum. is over- . to Holocene. As the Tulare Formation is defined (p. lain by .about 90 feet of ill-sorted red alluvial detri~us E21) as the uppermost deformed or tilted strata, the ranging from silt to cobble conglomerate. Separating valley alluvium can readily be distinguished from the the two reduced silt strata is 6-8 feet of sand ~and gravel. Tulare along most of the west border of the. are~ ~e­ The materi·al underlying the lower silt is poorly ex­ neath .the San Joaquin Valley, however, this distinc­ posed but it wppears to consist of intermixed sand and tion is virtually meaningless because the Tulare and the gvavei. The silt strata are exposed intermittently for overlying alluvium are conformable. . . more than a quavter of a mile in the roadcut ·and indi­ The thickness of the post-Tulare alluvium Is not cate ·a slight anticlinal upwarp. The silt appears to be known because the top of the Tulare Formation cannot nondiatomaceous and contains m:any suhrounded peb­ be identified in the valley. An indicated on page E23, bles and sand gvains indic81ting a probable nearshore for purposes of defining thickness in this report the lake environment. Where the Corcoran Clay Member is depth to the top of the Tulare Formation is arbitrarily known in the subsurface 2lh miles east of this outcrop, assumed to increase eastward :from a featheredge at it is 25 feet thick. At that point, the Corcoran is 320 the foothills to about 200 feet below the land surface feet lower in altitude than the exposure described, but beneath the present valley axis. Under this arbit~ary is rising about 110 feet per mile toward the west at a assumption, the thickness of the post-Tulare alluvium gradually increasing rate. Lithologic similarity, strati­ ranges from 0 to about 200 feet. graphic position, and the f~oot tha;t in this part of the The lithology of the alluvium is similar to that of the San Joaquin V·alley the Corcoran is the uppermost underlying deposits of the ~are; it consists ~f sand, reduced deposit, strongly suggest correlation of 1the silt, clay, and minor gravel laid down~ alluvial fa~s lacustrine silt exposed at the mouth of Little Panoche and on flood plains. Poorly sorted alluvial-fan deposits Creek with ;the Corcoran. 'from the Diablo Range generally predominate, except A few miles to the northwest, the outcrop of the Con­ in the eastern part of the area, which is underlain coran Clay Member along the east edge of the Laguna chiefly by well-sorted mic81ceou~ sands ~erived f~om the Seca Hills has been described (p. E23). Sierra Nevada, and by fine-grained IQaSin deposits near TERRACE DEPOSITS (PLEISTOCENE) the surf81ce. SOILS Stream-terr81ce deposits, obviously older than the present flood plains, are found along nearly all the The alluvium at the land surface near the west border streams but only along the north sides of Cantua and of the valley has heen subdivided on plate 1 mainly on Panoche' Creeks .are they sufficiently extensive. to be the basis of soil-profile development. Soil surveys of the shown on plate 1. The deposits are similar to some of U.S. Department of Agriculture ( Harmdine ~and others, the coarser materials in the underlying Pliocene and 1952, 1956) were used to delineate the soil types. !he Pleistocene formations. They consist principally of valley soils in .the area of plate 1 that a~ characten.zed gravel containnig boulders to about 2 feet in diameter by .profile development include the P.anhill, Lost Hills, in •a matrix of sand and silt. Thickness commonly and ·OrtigaHta soil series. In the area m•apped, only ranges between 2 and 20 feet. the P~anoche soil series is characterized by a lack of .pro­ file development. The terrace deposit mapped along Cantua Creek evi­ Other :f81Ctors being equal, the degree of profile de­ dently was laid down by the creek when its erosional velopment could he taken as a meas~r? of relative. age and load-carrying capabilities were much greater than of the soils. However, the characteristics of the soil at at present. The deposit ·appears to be flat lying, or a given place depend also on such variable :factors as nearly so, and thus is uncon!formaJble on, and younger (1) the lithology of the source mater~al, (2) the e~- than, .the Tulare. As the terr81ce deposits are younger vironment in 1which the soil was deposited and the ch­ than the Tulare but older than the alluvial deposits mate since deposition, ( 3) plant and animal. life ~n now laid down in the stream channel, they are presumed the soil, and ( 4) relief and drainage. These variables In to be of Pleistocene age. the area mapped are very complex. As a result, the

411-341 0-71-4 E34 MECHANICS OF AQUIFER SYSTEMS two classes of soil-profile development indicated by compressible than sand under load, such ·as that applied .plate 1 are at best poor indic8!tors of younger and older when artesian head declines. Therefore, it is important surfaces. in study of sll!bsidence problems and the compaction of The division of the surface alluvium into the two deposits under increased effective stress to differentiai:e classes is useful as a rough measure of relative perme­ between a water-bearing unit that is composed entirely ability to influent seepage. The Panoche soils are per­ of coarse material, such as clean sand and gravel, and meable to mode:r.ately permeable; the others (Panhill one that contains many fine-grained interbeds of .silt series and older) are in general only moderately to and clay. For purposes of differentiation in the studies poorly permeable. of compaction and subsidence, a water-bearing unit characterized by approximate hydraulic continuity but HYDROLOGIC UNITS IN THE GROUND-WATER that contains many fine-grained interbeds is termed an RESERVOIR aquifer system. Thus, under this definition, the lower water-bearing zone is ·a confined aquifer system. The geologic maps and sections in this report show A simplified picture of the hydrologic units toot con­ that the subsurface geology of the fresh-water-lbearing stitute the ground-water reservoir is presented in four deposits is highly complex when the deposits are generalized sections to show the principal geologic con­ differentiated with re$pect to source, environment of trols and the two hydrologic units-the semiconfined deposition, and, in part, lithologic character. Fortu­ aqui1fer system of the upper zone and the confined 'aqui­ nately, the hydrologic units are not so complex in their fer system of the lower zone. These sections (figs. 13, gross fea,tures rel8!ting to occurrence .and movement of 14) coincide with the detailed geologic sections of plates ground water. As pointed out by Davis and Poland 3 and 4, and ·are identified by the same letters. ( 1957, .p. 421), ·a generalized threefold subdivision of the The depth of wells tapping the ground-water reser­ fresh-water-hearing deposits can be made as follows: An voir generally decreases from w~ to east and ranges upper unit extending from the land surface to the -from ,as much as 3,800 feet in the southwestern part of top of the relatively impervious Corcoran C1ay Mem­ the area along the west border of the valley to less than ber (diatomaceous clay) at a depth ranging from 10 200 feet near Fresno Slough. In the western and cen­ to 900 feet below the land surface; the Corcoran Clay tral parts of the area, most wells tap both the upper and Member, ranging in·thickness from 'a featheredge to 120 lower w8!ter-bearing zones, although many tap only feet, which separates waters of substantially different the lower zone. The deepest wells are in the western part chemical quality; and a lower unit 100 to more than of the area south df Panoche Creek, because the average 2,000 feet thick that extends down :to the deposits con­ permeability of the ·aquifer systems is low. In order to taining :the main saline water !body. The saturated pant obtain the locally required 1,000-2,000 gallons per min­ of the uper, unit they referred to as the upper water­ ute for irriga,tion, wells must tap a thicker saturated bearing zone, and the lower unit, as the lower w8!ter­ section and are drilled through thick all uvial-fan de­ bearing zqne. posits of generally low perme8!bility to reach more per­ As shown by the electric logs on the geologic sections meaJble underlying flood-plain and deltaic deposits. In and by core-hole logs, the fresh-water-bearing deposits the eastern part of the area from Tranquillity south to in the Los Banos·Kettleman City area are heterogene­ the Kings River, in the reach where the thickness of the ous, as would be expected from their environments of highly permeable Sierra micaceous sand above the Cor­ deposition, 'and they display rapid v·ariation in texture coran exceeds 300 feet and the water is of good quality and permeability, especially in the vertical direction. (fig. 10), most wells tap only the upper zone. Here, the Beds or lenses of sand are separated by strata of silt average depth of wells is 400~600 feet. and clay of low permeability. The yield faetor 4 (Poland, 1959, p. 32), whi~h is an If an ·aquifer is defined as a permeable deposit that approximate measure of the average perme~bility of will yield water to wells, the entire lower zone can be the water-bearing material tapped by a well, is shown considered an aquifer in a broad sense. On the other in figure 15 to ;be highest for shallow wells which tap hand, the permeable sand units can be considered as only the flood-pl,ain deposits (Sierra micaceous sand) aquifers, sepamted hydraulically in varying degree by in the upper water-bearing zone (section 0-0'). The the finer grained less permeable interbeds of silt and wells .with the lowest yield factor are generally those clay. Silt and clay, especially the latter, are much more which tap mainly alluvial-fan deposits.

4 Specific capacity (gallons per mlDIUte per foot of drawdown X 100). Yield factor Perforated casing interval, in feet COMPACTING DEPOSITS, LOS BANOS-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E35 NORTH SOUTH A A' 800'

Cantua Creek (town)

SEA LEVEL (Upper zone)

(Lower zone)

4000'

h 3 for Iocation of section. drologic units. Tranqui I bowing Y See figure from 'll'tyr ctlon A-A'' • h however, . the uppe FIGuam 1&.-Generallzed •• 'de along Fresno ~lou~i~er, wells tappdiO:,d quality TER BEARIN G ZONE d :utheast· ld to WR tteher ture o :wter M fromfththeseisst o UPPER WA 'ng- zone has a The~;:~:quate quanftit~(fig. 20"o-500 feet t..r-bean 'I generawaterlta~~~.:r: • ~~:~:.~~ation.s from :~~:"';5oF· aceous sa15~d The upper wa . unconfined. n . nfined to con- wells range ..... rmeable rotc Cl y ·Member. ll the water ~s h' zone is semtco h d differ- supPly is fromi.·~ the Corcovan a loca y' d ater m t IS •ng draft, ea n h' k that overl lNG ZONE d the groun w ditions of ;pump! developed betwee t IC WER WATER-BEAR. ectively confine :fined. U~'7~~ feet or roo'{' h~:~n wellstappin~2r~ W . zone IS eff 12) except entials o bl nd the wat..r ev ran Clay Mem The lower ( figfs. Los 'Banos- theence, water confinemen ~ :: just a;boved in the genera c;:c:ubstantial '. more in coarse so~: the CorcoranwaterC~~:yar~~mber estern part o t~;'Clay !Member base of thts zo tis known to' 1 it increases WI bloycally in th.e soruetah wwhere the Corcloarack~Ing. This.Io.w er_ of area,s 0: the.deposJ:,:;,ility, differ- KettlBlllan is .water pd~rts pth. butt~e In ,place oferh~re vertical pe ne thus con- is absent, an<;;~:finement . . al source or;;~~d City area, fo~~~~~san 75 e . ed ' and h av e greu~L t ThiS up per. zo with t h e zone IS. the princiBanos-- p K~~~-tieman"" d thwt I't su pplies 1- grain in head are not greanu.~nfined aqulflers, to place. tion in the Los 57 p. 432) estimatefthe waterp~esen't y ences be of se f p ace . nd ( 19 ' Much o s pore 1 tainsfi a num ~ement varying r:~s termed a semi- and Po at f the pumpage. the lower zone rained degree of con unit .this upJ?Br zo rt 80 percen .o roduced from ut of the fine-g f the Considered O:S a ~min this rep~ . 'rrigation wells {1966) :~nf, king squeez~d) ~by compaotion 1o con n ed aquifer h syore t h ·an 1' 000 active· tion I supply in theh water t adun . errts (aquitar· ~ n a'rtesi' an head. ells Most of t e m b lk of the irrJga furated in t e clayey se due to declme I oduced from w h t furnish the u City area are per . the lower aquifer system re of the water zone ranges i.:s Banos--Kettleman er zone as well as ':rmea:bility The temperatu ·w,.ter-beanng~r . drnwn .fro~from lower part ofr the t&pping only where w":"r !;ormation. In zone. ' ti:em':~ofthe n deposits, an. ardeai!:l~;~~ ' more permeaeaste{~ bout soo to th~~o:::ept90 ' . ts below the Tu are of theHowe~e qualilty md!:he upper zone perme,.ble deposJ part, thealluvJa~f:..ter r;lain deposits precl~ an area about 5 ID!~~~ ~he soleSierra source floo o f irrigation water. E36 MECHANICS OF AQUIFER SYSTEMS

c c'

400'

SEA LEVEL

400'

800'

1200'

1600'

2000'

2400'

2800'

E E'

SEMICO ____ _ SEA LEVEL --- __ N~I~~DAQUIFER ------Piezomet.Ma/~~~rface ------;.;- ·- - ___ _ (Upper zone)

(principal ;~ayf_n mmg ~ember bed)

(Lower zone)

2400'

2800'

3200'

0

FIGURE 14 G 8 MILES .- enerallzed sectiODS B-B', C- , VERTICAL EXAGGER ATION X13 C, andE-E' • showing h ydrologlc units. See figur e 3 for locatl on of sectiolliS. COMPACTING DEPOSITS, LOS BAN08-K:Ji1TTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E37

B 1200'

800'

400'

SEA LEVEL

400''

800'

1200'

1600'

2000'

c -;: ~ c' 1200' ~ ;;! ol 0 ..s""' B~ ~ 800' 1=1.;.:: ol"' u~ ~ 400' u ~

SEA LEVEL ~ Flood-plain 400'

800'

1200'

1600'

2000'

2400'

2800'

1200'

800'

400'

SEA LEVEL

400'

800'

Chiefly deltaic 1200' '\ \ 1.3 deposits \\""­ 1600' \\ 2000' \ "'-- 2400' \ --- 2800'

3200' J------~ 0 4 8 MILES

VERTICAL EXAGGERATION X 13 EXPLANATION 4.3 gg•F Confining clay layer i Well for which yield factor and water temperature is shown The upper number (above the line) indicates the yield factor which is the specific capacity (gallons per minute per foot of drawdown) times 100 divided by the thickness, in feet, of deposits opposite the perforated inter­ Zone of brackish or saline water val of the well casing. The lower number is the water temperature, in de­ grees Fahrenheit, at the point of discharge from the well. The position of perforated casing is indicated by heavy line segment. Wells more than 1 mile from the profile are shown by dn.. •hed lines

FIGURE 15.--Generalized sections B-B', 0-0', and E-E' showing yield factors of wells in relation to the depositional environment. See figure 3 for location of sections. MECHANICS OF AQUIFER SYSTEMS

such wells, the wlliter tempe:vature generally exceeds montmorillonite saturated with sodium has a larger 90°F (fig. 15, section E-E') and is as high as 114°F. void ratio and is more compressible than montmoril­ West of. the edge of the confining clay bed (Corcoran lonite saturated with calcium or mangesium (Meade, Clay Member) the temperature of the water produced 19'64, fig. 11). Meade's ( 19'63) study o£ montmorillonite­ from wells which do not completely penetrate the Tulare rich sediments in the San Joaquin Valley suggests that Formation is generally in the high seventies (fig. 16, sec­ the influence of different exchangeable cations may be tions 0-0', E-E'). This fact suggests thaJt recharge to significant for effective stresses as great as 750 psi. The the lower water-hearing zone by surface and shallow percent of absorbed sodium compared to other cations ground waters is rapid enough to alter the geothermal increases with depth in the montmorillonitic sediments gradient locally. of the project ·area (Meade, 1967, fig. 15). For these Although the geologic sections accompanying this re­ reasons the chemical character of the ground waters port indicaJte a complexity of geologic elements in this in the Los Banos-Kettleman City area is reviewed lower zone with respect to source and type of deposits, briefly in this report. hydrologic evidence of various types and consideration Many of the irrigation wells in the western two­ of the relatively uniform chemical quality of the thirds of the Los Banos-Kettleman City area are ground water in this lower zone lead to the conclusion perforated opposite both the upper and lower water­ that, in general, the zone has reasonably good hydraulic bearing zones. There are marked differences in quality continuity laterally and vertically. At Westhaven, for between the waters of the two zones; ·accordingly, ithe example, paired observation wells perforated 8Jt the top chemical quality of water from different wells differs and near the base of the lower zone, respectively, have considerably, depending chiefly upon the position of the not shown more than 30 feet difference in artesian head perfornted interval in the stratigvaphic section ·and the during an 8-year period (195~65), although the sea­ relative permeability of the zones ·at that place. The sonal :fluctu8!tion of head in both wells due to nearby chemical character of the waJter of the upper and lower pumping has been as much as 80 feet. From 1962 to wruter-bearing zones in this part of the San Joaquin Val­ 19'65, the head in both wells was equal within a few ·feet ley has been described in some detail by 'Davis and fur about three-quarters of eooh year. On the other Poland (1957, p. 448-462), and the character of the hand, ~t the northern end of the area near Oro Lorna, surface streams ~was discussed by Davis (1961). Much head differences of 7·5 feet have been observed in paired of the following discussion is :based on these earlier re­ observation wells tapping two separate :aquifers in the ports. The chemical ·analyses furnishing the basis for lower zone. Water-level data indicate that in the south­ the discussion of ground waters were made on water ern and central parts df the Los Banos-Kettleman City samples from 774 wells collected in August 1951. About area at least north to P·anoche Creek, hydraulic con­ all the well .. pumps had been operated continuously for tiunity throughout the zone is reasonably good; but a week to a month or more prior to sampling; therefore, from Little Panoche Creek north, confining interbeds the chemical character of the discharge ·at the time of are sufficiently thick, extensive, and impermeable to sampling was, for most wells, representative for the cause substantial differences in artesian head locally. intervals tapped. The sum of determined constituents utilized in defining concentOOJtion includes all principal CHEMICAL CHARACTER OF THE GROUND cations and •anions, hut it does not include nitrate and WATER silica. Therefore, the value cited is 20-150 mg/1 (lllillion gallons per liter) less than total dissolved solids. The chemical character of the ground water in the Los Banos-Kettleman City area changes notably with WATERS OF THE UPPER WATER-BEARING ZONE depth. The two major and most consistent changes with Ground waters of the upper water-bearing zone gen­ depth are (1) a marked decrease in dissolved solids and erally contain high concentrations of calcium, magne­ (2) .an increase in the percent of sodium among the sium, and sulfate. Pronounced changes in the chemical cations. The increase in percent sodium among the characteristics of these waters occur l~aterally along the a geochemical feature influencing the compaction of the eastern and western margins of the area, and gradational sediments under increasing effective stress. The clayey changes occur vertically with increasing depth. The sediments are .primarily montmorillonite (Meade, 1967, ground waters of the upper zone, however, can be p. C18). Experimental studies, summarized by Meade divided into two types: ( 1964, fig. 4), have demonstr.ated that montmorillonitic 1. The ground waters occurring in the uppermost 200- clays are more compressible than illitic or kaolinitic 300 feet :below the land surf,ace are ,predominantly clays. They have also demonstrated that, at effective calcium and magnesium sulfate :waters with total stresses up to at least 150 psi (pounds per square inch), determined constituents averaging about 3,000 COMPACTING DEPOSITS, LOS BAN08-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E39

mg/1 and ·a percent sodium of about 35. Except f.or stream wa;ters contain high concentrations of sulfate local variations caused Jby differences in quality and sodium with dissolved solids ranging tfrom less of the surf.ace streams that provide recharge along than 1,000 mg/1 to as much as 9,000 mg/1 (Davis, 1961, the western margin of the area, the chemical char­ p. Bl'6}. Davis explained the wide variation in the ·aoter of the ground waiters tapped by most shallow chemical character of the surface water as due mainly wells is relaltively constant. An abrupt change, to fluctuations in rainfall and local differences in the however, occurs along the eastern border of the lithology of the rocks underlying the drainage basins. area, where the water from the west side, char­ Examples from the five largest streams of the area, acterized by high concentration of suHate, merges Los Banos, Little Panoche, P.anoche, Los Gatos, and into the calcium and sodium bicarbonate ground Warthan Creeks (Davis, 1961, table 2) illustrate the waiter of low dissolved solids typical of shallow extreme variability of the chemical composition and water of the east side of the San Joaquin V~alley. character. In Los Banos Creek, the dissolved-solids con­ 2. The chemical charaoter of the waters contained in the tent ranged from 128 mg/1 at a flow of 450 cfs (cubic deposits from 200 .to 300 feet .below land surf·ace feet per second) to 583 mg/1 at a flow of 0.7 cfs. An down to the top of the Corcoran Clay Member is intermediate cation composition characterized the water m'arked by considerable lateral variance. As com­ at both extremes; the anion composition, however, pared to the overlying shallower waters, these changed from predominantly bicarbonate at high flow waiters have lower total determined constituents-­ to bicarbonate chloride ·a;t low flow. In Little Panoche on the order of 1,500 ·mg/1, and higher percent Creek, the dissolved-solids content ranged from 422 sodium-aboult 55. mg/1 at a flow of 30 cfs to 3,820 mg/1 at 0.8 dfs. At the West of the Fresno Slough the ground water of the highest stage, the water w.as characterized by an inter­ upper zone in the micaceous sand just overlying the mediate cation distribution, and bicarbonate and chlo­ Corcoran Clay Member (excluding the area of brackish ride, among the anions. At all other stages the stream water shown in fig. 10) has average total determined was a sodium chloride water. constituents of about 850 mg/1, and the .percent sodium In Panoche Creek, the dissolved-solids content is ®bout 60. This ·micaceous sand stratum represents de­ ranged from 1,310 mg/1 at a flow of 200 cfs to 5,250 position by streams originating in the Sierra Nevada, mg/1 at 1 cfs. At all stages, it wa;s predominantly sul­ and east of Fresno Slough it is presently receiving re­ fate water of intermediate cation composition. In Los charge water that is probably little differenit from that Gatos Creek, the dissolved-solids content ranged from in which it was deposited. Water that runs off the rela­ 273 mg/1 at a flow df 375 cfs to 1,530 mg/1 at 0.7 cfs. tively insoluble silicate rocks of the basement complex The water changed from ·a magnesium bicarlbona;te of the Sierra Nevada is predominantly calcium bicar­ water at high stage to a sodum bicarbonate sulfate bonate water generally containing less than 100 mg/1 water at low stage. In Warthan Creek, the dissolved­ of dissolved solids. solids content ranged from 350 mg/1 at a flow of 400 In the Fresno Slough area along the axis of the San cfs to 3,280 mg/1 at 0.5 cfs. The w:a;ter changed in chem­ Joaquin Valley from Mendota southeast about 22 miles, ical character from sodium sulfate bicarbonate type at flood-plain and lacustrine deposits that form most of high flow to sodium magnesium sulfate ·at low flow. the post-Corcoran section contain brackish water (fig. As most of the ground-wa;ter recharge from west-side 10). Presumably, this mineralized water resulted from streams is contributed ·a;t high stage, the chemical char­ evaporation at land surface in ·a swampy environment. acter df the ground waters commonly more closely re­ In this area, ground waters containing high sulfate and sembles that of the high flows than the low flows. chloride concentrations ·are found in the basal ·and mid­ die parts df the upper water-bearing zone (see fig. 15, WATERS OF THE LOWER WATER-BEARING ZONE generalized sections B-B', 0-0'). The total deter­ Ground waters of the lower water-bearing. zone mined constituents in this ground water of poor quality (confined aquifer system) under native conditions were average about 5,000 mg/1, and the percent sodium aver­ effectively separated from those of the upper water­ ages about 55. The ra;tio of sulfate to chloride is on the bearing zone throughout most of the Los Banos-Kettle­ order of 2 to 1. man City area by the Corcoran Clay Member of the STREAM WATERS Tulare Formation. Because about three-quarters of the The chemical character of the ground water in the water pumped from the project area has been taken upper water-bearing zone along the western margin of from the lower zone, the head in that zone has been the Los Banos-Kettleman City ar~a reflects the chemi­ drawn down 150-500 feet, historically. The head in cal character of the tributary streams. In general, the the lower part cYf the upper zone also has been drawn E40 MECHANICS OF AQUIFER SYSTEMS

down substantially. Looally in the southern third of ' alluvial fan (pl. 4, geologic section E-E'). The dis­ the area, the head in the basal aquifers of the upper solved-solids content in the 'Water from deep wells in zone has been drawn down as much ·as 30 feet below the this area :r,anges from 1,000 mg/1 to ·as much as head in the lower zone, hut in the northern two-thirds 2,100 mg/1, ·and the percent sodium is 50 or less. of the area, the head in the upper zone is still 50-200 In the southern and southeastern parts of the Los feet higher than that in the lower zone. Therefore, in Banos-Kettleman City .area, ·analyses of ground .waters most of the project area, most wells tapping the lower taken from wells near Westhaven 2,000-2,200 feet deep, water-hearing zone admit water from the upper water­ show th8!t, ·aJt ·a depth of 1,800-2,000 feet below the land bearing zone either through perforations or casing surface, the chemical character of the water changes leaks above the Corcoran or by movement from the from sodium sulfate water above to sodium chloride upper zone outside the casing through gravel envelopes. water below. This deeper water, although definitely For wells per'forated only in the lower zone, however, poorer for irrig81tion than the overlying water, is still downward movement of w8.ter from the upper zone is usable for a hlend and is considered .a basal water in small, and this water is withdrawn after a few hours of the lower waiter-hearing zone. The d8e!per wells in the continuous pump operation. vicinity of Westhaven .produce a mixture of the norm·al The data accompanying the chemical ,analyses of well lower zone sulf81te w8!ter ~and the deep chloride water waters collected in August 1951 (Davis ~and Poland, that ·averages about 900 mg/1 in dissolved solids and 90 1957, tables 2, 3) indicate that of 77 4 wells in the percent sodium. Carbon dioxide and hydrogen sulfide Los Banos-Kettleman City area sampled for chemical have .also been reported from these deep wells, •which analysis, perforated interval,was known for 447. Strati­ partially penetr81te the deltaic ·and lacustrine deposits graphic control largely developed since 1957 indicates in the lower part of the Tulare Formation. that the casings of 108 of these wells (24 percent) .were Electric logs suggest ~th81t the water from the sands perforated only in the lower zone, or in its stratigraphic in .the confined aquifer system !that underlie lthe Tulare equiv.alenlt in the areas where the Corcoran Clay Mem­ Formation in generalized sections A-A', 0-0', and ber is absent. Based chiefly on the :analyses .from the E-E' (figs. 13, 14) has a relatively low sodium chloride 108 wells, the areal variation in chemical character of content. Any marine water originally present in these the ground :waiter in the lower zone as of 1951 is sum­ estuarine or littoral sand deposits must have been marized 'as follows (W. B. Bull, U.S. Geol. Survey, flushed out. written commun:, March 1968): SALINE WATER BODY The sum of determined constituents in the lower zone ranged A saline water body underlies the fresh ground-water from about 600 to 2,500 m.g/l. The concentration was lowest, 600- reservoir throughout the Los Banos-Kettleman City 800 mg/1, in ·a strip a;bout 8 miles wide just west of F·resno Slough ex,tending from 7 miles south of Mendota to the Kings area. Along the eastern margin of the area, northwest River. To the west, the concentration ranged from 800 to from about the town of San Joaquin, this saline water 1,200 mg/1, except in two lobes of high concentration within · body is high in sodium chloride, and its top occurs at 6-8 miles of the foothms-on Los 'Gatos Creek fan and op­ depths of 800-1,500 feet below the land surface. (See posite the Big Blue Hills south of 'Cantua 'Creek, where con­ fig. 14 generalized section B~B'.) At one place 5 miles centra.tion is as much as 2,100 mgjl. In the 255-mile reach from the vicinity of Mendota to .the ·Fresno--

Los Banos-Kettleman City area, the general movement 320 mg/1 to 17,000 mg/1; the maximum would be com­ of the fresh ground water in the confined aquifer sys­ parable to modern sea water. tem was northeasterly from the Diablo Range foothills to the vicinity of Fresno Slough, and flowing artesian REFERENCES CITED wells were common in the valley trough .area. The large Anderson, F. M., 1905, A stratigraphic study in the Mount withdrawal of water from the aquifer system below Diablo Range of California : Oalifornia Acad. Sci. Proc., the Corcoran Clay Member gradually reversed the hy­ 3d ser., v. 2, p. 155-248. draulic gradient, and by 1960 it was 20-25 feet per mile Anderson, Robert, and Pack, R. W., 1915, Geology and oil re­ sources of the west border of the San Joaquin Valley north southwestward to within a few miles of the Diablo of Coalinga, California: U.S. Geol. Survey Bull. 603, 220 p. Range foothills. Arnold, Ralph, 1909, Paleontology of the Ooalinga district, In the central part of the Los Banos-Kettleman City Fresno and Kings Counties, California: U.S. Geol. Survey area the altitude of the top of the saline water body east Bull. 396, 173 p., 30 pls. of Fresno Slough is at least 1,000 feet higher than it is Arnold, Ralph, and Anderson, R. E., 1908, Preliminar;v report 0-0'). on the Coalinga oil district, Fresno and Kings Counties, a few miles west of the slough (fig. 14, section California: U.S. Geol. Survey Bull. 357, 142 p., 2 pls. It would seem likely that, in response to the reversed -- 1910, Geology and oil resources of the Coalinga district, hydraulic gradient, the shallow saline water east of California: U.S. geol. Survey Bull. 398,354 p. Fresno Slough would move westw.ard ·and displace fresh Axelrod, D. I., 1962, Post-Pliocene uplift of the Sierra Nevada, water. However, water sa.mples taken from scattered California: Geol. Soc. America Bull., v. 73, p.183-198. Axelrod, D. I., and Ting, W. S., 1960, Late Pliocene floras east wells west of the saline water front in this area during of the Sierra Nevada, California: California Univ. Geol. the 10 years 1953-62 and at equivalent depths have Sci. Pub., v. 39, no. 1, p. 1-118. shown no significant chemical changes. This is not sur­ --1961, Early Pleistocene floras from the Chagoopa SJUrface, prising, however, because ground w,ater moves very southern Sierra Nevada, Calif~rnia: California Univ. Geol. slowly through even the coarsest and most permeable Sci. Pub., v. 39, no. 2, p. 119-194. deposits in this area under the hydraulic gradient de­ Barbat, W. F., and Galloway, John, 1934, San Joaquin Clay, California: Am. Assoc. Petroleum Geologists Bull., v. 18, veloped. For example, the coefficient of permeability of No. 4, p. 4 78-499. the coarsest deposits in the confined aquifer system Bull, W. B., 1961, Causes and mechanics of near-surface subsi­ probably is on the order of 500-1,000 gallons per day dence in western Fresno County, California, in Short papers per square foot. At a GQnstant hydraulic gradient of in the geologic and hydrologic sciences: U.S. Geol. Survey Prof. Paper 424-B, p. B182-B189. 20 feet per mile, about 9-18 years would be required --· 1964, Alluvial fans and near-surface subsidence in west­ for water to move 1 mile. Thus, westward movement of ern Fresno COunty, California: U.S. Geol. Survey Prof. the relatively shallow upper part of this saline water Paper 437-A, 71 p. body into the Los Banos-Kettleman City area in the Briggs, L. I., 1953, Geology of the Ortigalita Peak quadrangle, vicinity of the town of San Joaquin (section 0-0') California: California Div. Mines Bull.167, 61 p. probably has not exceeded 1-3 miles, even in the coarsest California Division of Mines, 1958, Geologic map of California, Santa Cruz sheet. deposits. Carpenter, D. W., 1965, Pleistocene deformation in the vicinity The saline water body above the base of the Tulare of the Mile 18 pumping plant, in Northern Great Ba·sin and Formation in the southeastern part of the Los Bano&­ California: lnternat. Assoc. Quaternary Research Cong., Kettleman City area (fig. 14, generalized section E-E') 7th, USA, 1965, Guidebook for Field Conf. 1, p. 142-145. contains fresh-water fossils, and its present salinity is Cole, R. C., and others, 1952, Soil survey of the Los Banos area, California: U.S. Dept. Agriculture, ser. 1939, no. 12, 119 p., thought to be a secondary feature. Chloride analyses of soil map, 1:31,680. core samples from core hole 19/19.....:17P show a range of Croft, M. G., 1968, Geology and radiocarbon ages of late Pleisto­ chloride concentration in this zone of 2-60 grains per cene Lacustrine clay deposits, southern part of San Joaquin 1,000 cc of core sample.5 Porosities in this zone are Valley, California, in Geological Survey research 1968: U.S. thought to average about 40 percent. This would indi­ Geol. Survey Prof. Paper 600--B, p. B151-B156. cate that the approximate chloride concentration of Curtis, G. H., Evernden, J. F., and Lipson, J., 1958, Age deter­ mination of some granitic rocks in California by the Potas­ the water ranges from 320 mg/l to 9,.700 mg/1. Core sium-argon method : California Div. Mines Spec. Rept. 54, samples in the main •saline water body below the base 16 p. of the Tulare Formation to a depth of 3,735 feet below Davis, G. H., 1961, Geologic control of mineral composition of land surface show chloride concentrations that range stream waters of the eastern slope of the southern Coast from 2 to 106 grains per 1,000 cc of core sample. As­ Ranges, Oalifornia: U.S. Geol. Survey Water-Supply Paper 1535-B, 30 p. suming a 40 percent porosity for these samples also, the Davis, G. H., Green, J. H., Olmstead, F. H., and Brown, D. W., chloride content of this water would range from about 1959, Ground-water conditions and storage capacity in the San Joaquin Valley, Calif.: U.S. Geol. Survey Water-Sup­ II Shell on Co., 1929, "Results of Core Drilling on the Boston Land Co. Property," unpublished report. ply Paper 1468,287 p. E42 MECHANICS OF AQUIFER SYSTEMS

Davis, G. H., Lofgren, B. E., and Mack, Seymour, 1964, Use of Lohman, K. E., 1938, Pliocene-diatoms from the Kettleman Hills, ground-water reservoirs for storage of surface wat~r in the Calif.: U.S. Geol. Survey Prof. Paper 189-C, p. 81-102. San Joaquin Valley, Calif.: U.S. Geol. Survey Water-Supply Matthes, F. E., 1930, Geologic history of the Yosemite Valley: Paper 1618, 125 p. U.S. Geol. Survey Prof. Paper 160,137 p. Davis, G. H., and Poland, J. F., 1957, Ground-water conditions Meade, R. H., 1961a, X-ray diffractometer method for measur­ in the Mendota-Huron area, Fresno and Kings Counties, ing preferred orientation in clays, in Short papers in the California: U.S. Geol. Survey Water-Supply Paper 1360-G, and hydrologic sciences: U.S. Geol. Survey Prof. 180 p. geolo~c Paper 424-B, p. B273-B276. Diepenbrock, Alex, 1933, Mount Poso oilfield : Summary of op­ erations, California Oil Fields, v. 19, no. 2, p. 12-29. --- 1961b, Compaction of montmorillonite-rich sediments in Frink, J. W., and Kues, H. A., 1954, Corcoran clay-A Pleisto­ western Fresno County, Calif., in Short papers in the geo­ cene lacustrine deposit in San Joaquin Valley, California: logic and hydrologic sciences: U.S. Geol. Survey Prof. Paper Am. Assoc. Petroleum Geologists Bull., v. 38, no. 11, p. 424-D, p. D89-D91. 2357-2371. --- 1963, Factors influencing the pore volume of fine-grained Goudkoff, P. P., 1934, Subsurface stratigraphy at Kettleman sediments under low-to-moderate overburden loads: Sedi­ Hills oilfield, California : Am. Assoc. Petroleum Geologists mentology, v. 2, p. 235--242. Bull., v.18, no. 4, p. 435-475. --- 1964, Removal of water and rearrangement of particles Harradine, F. F., and others, 1952, Soil survey of the Coalinga during the compaction of clayey sediments-Review: U.S. area, California: U.S. Dept. Agriculture, ser. 1944, no. 1, 91 Geol. Survey Prof. Paper 497-B, 23 p. p., soil map, 1 : 63,360. --- 1967, Petrology of sediments underlying areas of land --- 1956, Soil survey of the Mendota area, California: U.S. subsidence in central California: U.S. Geol. Survey Prof. Dept. Agriculture, ser. 1940, no. 18, 96 p., soil map, 1:63,360. Paper 497-C, 83 p. Holmes, Arthur, 1965, Principles of physical geology [2d ed.] : --- 1968, Compaction of sediments underlying areas of land New York, Ronald Press, p. 360. subsidence in central California : U.S. Geol. Survey Prof. Hunter, G. W., 1951, Guijarral Hill·s oil field : Summary of Paper 497-D, 39 p. operations, California Oil Fields, v. 37, no. 1, p. 13-19. Inter-Agency Committee on Land Subsidence in the San Joaquin Mendenhall, W. C., Dole, R. B., and Stabler, Herman, 1916, Valley, 1955, Proposed program for investigating land sub­ Ground water in the San Joaquin Valley, Calif.: U.S. Geol. sidence in the San Joaquin Valley, California: Sacramento, Survey Water-Supply Paper 398, 310 p. Calif., 59 p., 9 pis. Miller, R. E., 1961, Compaction of an aquifer system computed ---1958, Progress report on land-subsidence investigations from consolidation tests and decline in artesian head, in in the San Joaquin Valley, California, through 1957: Sacra­ Short Papers in the geologic and hydrologic sciences: U.S. mento, Calif., open-file report, 160 p., 45 figs. (prepared Geol. Survey Prof. Paper 424-B, p. B54-B58. chiefly by U.S. Geol. Survey). Payne, M. B., 1951, Type Moreno Formation and overlying Ireland, R. L., 1963, Description of wells in the Los Banos­ Eocene strata on the west side of the San Joaquin Valley, Kettleman City area, Merced, Fresno, and Kings Counties, Fresno and Merced Counties, California : California Dlv. Calif.: U.S. Geol. Survey open-file report, 519 p. Mines Spec. Rept. 9, 29 p., 5 pls., 11 figs. Janda, R. J., 1965, Quaternary alluvium near Friant, California, Poland, J. F., 1959, Hydrology of the Long Beach-Santa Ana in Northern Great Basin and California: Internat. Assoc. area, California, with special reference to the watertight­ Quaternary Research Cong., 7th, USA, 1965, Guidebook for ness of the Newport-Inglewood structural zone: U.S. Geol. Field Conf. 1, p. 128--133. Survey Water-Supply Paper 1471, p. 32. Jenkins, 0. P., 1938, Geologic map of California: California --- 1960, Land subsidence in the San Joaquin Valley, Calif., Dept. Nat. Resources, Div. Mines. and its effect on estimates of ground-water resources: In­ Johnson, A. I., Moston, R. P., and Morris, D. A., 1968, Physical ternat. Assoc. Scientific Hydrologists, Comm. Subterranean and hydrologic properties of water-bearing deposits in sub­ Waters, Pub. 52, p. 324-335. siding areas in central California: U.S. Geol. Survey Prof. Paper 497-A, 71 p. --- 1961, The coefficient of storage in a region of major sub­ Kaplow, E. J., 19i.2, East Coalinga extension oil field : Summary sidence caused by compaction of an aquifer ssytem, in of operations, California Oil Fields, v. 28, no. 1, p. 15-29. Short papers in the geologic and hydrologic sciences: U.S. Kundert, C. J., 1955, Geologic map of California : California Geol. Survey Prof. Paper 424-B, p. B52-B54. Dept. Nat. Resources, Div. Mines. Poland, J. F., and Davis, G. H., 1956, Subsidence of the land Kistler, R. W., Bateman, P. C., and Brannock, W. W., 1965, surface in the Tulare-Wasco (Delano) and Los Banos­ Isotopic ages of minerals from granitic rocks of the central Kettleman City area, San Joaquin Valley, California: Am. Sierra Nevada and Inyo Moun1tains, California: Geol. Soc. Geophys. Union Trans., v. 37, no. 3, p. 287-296. America Bull., v. 76, p.155-164. Poland, J. F., and Evenson, R. E., 1966, Hydrogeology and land Leith, C. J., 1949, Geology of the Quien Sabe quadrangle, Cali­ subsidence, Great Central Valley, Calif., in Bailey, E. H., fornia: Calif. Div. Mines Bull.147, 59 p. ed., Geology of northern California : California Div. Mines Lofgren, B. E., 1960, Near-surface land subsidence in western and Geology, Bull. 190, p. 239-247. San Joaquin Valley, California: Jour. Geophys. Research, Schoellhamer, J. E., and Kinney, D. M., 1953, Geology of a part v. 65, p. 1053-1062. of Tumey and Panoche Hills, Fresno County, California: --- 1961, Measurement of compaction of aquifer systems in U.S. Geol.. Survey Oil and Gas Inv. Map OM 128. areas of land subsidence, in Short papers in the geologic and Taliaferro, N. L., 1949, Geologic map of the Hollister quadrangle, hydrologic sciences: U.S. Geol. Survey Prof. Paper 424-B, California: California Dept. Nat. Res., Div. Mines Bull. p. B49--B52. 143, pl. 1. COMPACTING DEPOSITS, LOS BANOs-KETTLEMAN CITY SUBSIDENCE AREA, CALIFORNIA E43

Wahrhaftig, Clyde, and Birman, J. H., 1005. The Quaternary of White, R. T., 1940, Eocene Yokut sandstone north of Coalinga, the Pacific Mountain system in California, itn Wright, H. California: Am. Assoc. Petroleum Geologists Bull., v. 24, E., Jr., and Frey, D. G., eds., The Quaternary of the United no. 10, p. 1722-1751. States, A Review Volume for the 7th Congress of the Woodring, W. P., 1952, Pliocene-Pleistocene boundary in Cali­ Internat. Assoc. for Quaternary Research: Princeton, N.J., fornia Coast Ranges: Am. ,Jour. Sci., v. 250, no. 6, p. 401- Princeton Univ. Press, p. 299-340. 410. Watts, W. L., 1894, The gas and petroleum yielding formations Woodring, W. P., Stewart, Ralph, and Richards, R. W., 1940, of the central valley of California: California State Mining Geology of the Kettleman Hills oil field, California: U.S. Bureau, Bull. 3,100 p. Geol. Survey Prof. Paper 195, 170 p.

INDEX

[Italic page numbers indicate major reference!(]

A Page Page Page Diablo Range. ______------______E17, 21,24 Geologic sections ••. ------E14 Acknowledgments______E8 alluvial-fan deposits. ______------_ !5, 18,33 Geologic units of drainage area tributary to Los Age, Tulare Formation______IS geology of tributary drainage area______9 Banos-Kettleman City area______10 Agriculture.-_------______------___ I structure.- ______. ______.__ 9 Geology.------·------8 Alluvial-fan deposits, Diablo Range ______15,!8,SS Diablo Range foothills______41 tributary drainage area, Diablo Range____ 9 Los Gatos Creek .. ------15,40 Diatom floras, Tulare Formation ______23,14 Glvcvmeris fossil zone, Etchegoin Formation._ 14, 16 Sierra Nevada. ______.. ____ 18 Dissolved solids, decrease in______38 Goudkoff, P. P., cited______15 Tulare Formation.______15 in stream waters------S9 Ground water, chemical character __ • ______. _ S8 Alluvium ______. ___ ._ SS lower water-bearing zone._- ______. ___ . 40 Ground-water reservoir, hydrologic units._ .• _ S4 Amnicola fossil zone, Tulare Formation.______30 Domengine Creek.______21 Ground-water withdrawal from Cenozoic Anderson, R. E., cited ______14, 16, 20,21 Domengine Sandstone------12 water-bearing deposits______4 Anticline Ridge ______13, 14, 16, 20,21 Drainage basins. ______------11 Guijarral Hills------20,21 Areas of generalized geologic units within Gypsite._--- ______-- __ ------II stream basins______11 E Gypsum ______------17,22 Arnold, Ralph, quoted ______14,16 veins. ______----- 21 Arroyo Ciervo______21 Electric-log, interpretation------5 Arroyo Ciervo basin------12 resistivity curve______7 H Arroyo Hondo______14, 15, 16,22 S.P. curve.______7 Arroyo Hondoupperbasin______11 spontaneous-potential curve. ______._._.__ 7 Holmes, Arthur, cited______24 Artesian head, declines______I Electric logs ______------40 Hornblende-quartz gabbro______10 Eocene marine sedimentary rocks______a Hydrocompaction of moisture-deficient de- B Equus ____ ------______24 posits above water table______! Etchegoin Formation ______5, 9, 16,23 Hydrologic units in ground-water reservoir-.- S4 Big Blue Serptinous Member of Temblor For- blue sandstone ______.______16 mation ______------______1S fresh-water-bearing strata..• ______1S, 17 I Blue sandstone, Etchegoin Formation•• ______16 Glvcymeris fossil zone. ______------14, 16 Jacalitos Formation.• ------____ 14 unconformity between Tulare Formation. 17 illite._------__ ------11 Briggs, L. I., cited------10, 12,23 wells .. ______------· ______-····---- 17 Inter-Agency Committee on Land Subsidence Bull, W. B., quoted______40 Echegoin Ranch ______.______16 in the San Joaquin V~ey ______4,5, 14 Introduction. __ • ______---- __ -- ____ --_------1 Extent, Etchegoin Formation------16 c Jacalitos Formation______14 Irrigation ______------2, 4 San Joaquin Formation______!0 wells _____ ------28, 35, S8 Calcium concentrations in upper water-bear- ing zone______S8 F J Cantua Creek. ______16, 33 Feldspar ______------_____ 12 Jacalitos Creek drainage basin______14 Cantua Creek (town>------U,SS Fieldwork ______------_ 4, 5 5, 14 Cantua Creek upper basin______12 Flood-plain deposits, Sierra Nevada. ______!8,35 Jacalitos Formation. ____ . ___ -______-- __ ----- Tulare Formation ______!5,!8 blue sandstone. ____ ------14 Cantua Creek valley. __ ------21 opalized wood fragments ______14,15 Cascalo. Conglomerate Member of San Joa- Fossils, fresh-water, in saline water body.____ 41 Jacalitos Formation______14 Jacalitos Hills .• ------21 quin Formation___ ------16,20 Jurassic rocks ______.----____ ----- 9 Chemical character of ground water______S8 mammal bones, Corcoran Clay Member Chloride concentrations, In saline water of Tulare Formation______IS,!4 K body------40,41 marine, Etchegoin Formation, Kettleman in upper water-bearing zone______S9 Hills.------____ ------__ ---__ 17 Kaplow, E. J., cited.______20 Ciervo Hills •• ______------_ 30 San Joaquin Formation.______!0 Climate .• ------1 San Pablo Formation______13 Kern River Formation.------24 Coalinga.------______4,16 Tulare Formation ______SS,14,SO Kettleman Hills. ______4, 5, 9, 15,16,20,21 Coalinga antlcllne______12 Franciscan Formation ______------9, 10,11 deformation._. ______---- __ .. --. 20 Coast Ranges _____ ------______------8, 23 Fresh-water-bearing deposits, Etchegoin fossils, in Tulare Formation._--.- ___ -.--- IS, !4 uplift______9 Formation______1S, 17 marine, in Etchegoin Formation______17 Corcoran Clay Member of Tulare Forma- San Joaquin Formation______1S wells. ______.. __ - __ ---.------1! tion ______------4, 15, SO, 34, 35 subsurface geology______S4 Kings River ______. ___ --_------_-----.- 28,35 fossil mammal bones._------!S, !4 Tulare Formation______1S Kreyenhagen Formation, thickness------IS Core holes, in or near Los-Banos Kettleman Fresh-water mollusks, Tulare Formation.____ 14 Kreyenhagen Hills------21 City area ______5, 7, IS, 25 Fresno Slough ______28, 34, 35, 39, 40,41 Kues, H. A., cited------30 logs.______14 Friant..------______------23,24 Cretaceous rocks.______9 Frink, J. W., cited------30 L Cretaceous sedimentary rocks •• ______1fJ G Lacustrine deposits, Tulare Form ation __ 21, 15, 18, 40 D Laguna Seca Formation------12 Geochemical Surveys of Dallas, Tex ______5 Laguna Seca Hills ______------23,33 Dalrymple, G. B., cited______24 Geologic history ___ ------______8 Davis, G. H., cited----~------11,30,39 Geologic mapping, water-bearing deposits.-_- 5 Lakes in subsurface deposits------SO Deltaic deposits, Tulare Formation______!8,40 Land-surface subsidence, problems •• ------I, 4 E45 E46 INDEX

Page Page Thickness-Continued Page Lithology, Etchegoin Formation...... E16 Reef Ridge Shale. ______.• ___ .______E12 Jacalitos Formation ______E1o Jacalitos Formation______14 Rhyolitic ash bed------23 Kreyenhagen Formation______11 San Joaquin Formation...... SO Lodo Formation..______1! Tulare Formation ••• "·------11 s Moreno Formation______11 Little Panoche Creek ______21,22,1a,33,38 Saline water bodY------40 Panoche Formation______10 dissolved solids .••.•... _____ ------a9 fresh-water fossils·------"------. 41 San Joaquin Formation______so Little Panoche Creek basin.______11 San Joaquin ClaY------SO Tulare Formation •• ______-----___ sa Location ofarea.------1 San Joaquin Formation------9,SO Tranquillity______-----_---- ____ ----______35 Lodo Formation, thickness.______11 Cascajo Conglomerate Member.______so Trefzger, R. E., cited______24 Logs of core holes·------14 fresh-water-bearing strata______1a Tulare Formation ______5, 16, 17, 20,S1,41 Lohman, K. E., cited______24 marine fossils. ______------SO alluvial-fan deposits •• _____ •• ______So Los Banos Creek, dissolved solids------a9 Mga zone.------20,21 Amnicola zone______30 Los Gatos Creek, alluvial-fan deposits ______lo, 40 wells .• - ______.------______.• ---- __ . SO Corcoran Clay Member•• ______4,15,80,34,35 dissolved solids•••. ______------______a9 San Joaquin (town).------40,41 fossil mammal bones ______13,14 Lost Hills soil series·------33 San Joaquin River.------28 deltaic deposits. ______18,40 Lower Cretaceous sedimentarY------10 San Joaquin ValleY------4, diatom Jloras .• - ______• ______23, S4 Lower Tertiary sedimentary rocks______11 5, 11, 12, 13, 15, 20, 23, 25, 30, 33, 38, 39 Jlood-plain deposits ______lo,l8 Lower water-bearing zone, chemical character. a9 structure ••• ______------8 fossils .•.•. _____ ---·--______30 waters ••. ______• ______• __ ------___ a9 water-level decline______4 fresh-water-bearing deposits .. ______13 San Luis project ______23,24 lacustrine deposits. ___ •• ____ • ______21, So, 18, 40 M San Pablo Formation, marine deposits of Mio- unconformity between Etchegoin Forma- tion. __ ._----______17 McLure Shale Member of Monterey Shale.__ 12 cene age. ____ ------9 Magnesium, concentrations in upper water- marine fossils. __ . _____ . ____ . __ .----____ --- 13 Tulare Lake bed ______------12, 28,30 bearing zone •• ______a8 Santa Margarita Formation.- .•.. __ ...... ___ 13 Tumey Gulch ______17,23 in ultramafic rocks______11 Scope of report. __ .------4 Tumey Hills. ______------___ 4, 5, 22,30 Sections, showing principal geologic controls Marine deposits------9, 11 Mawby, J. E., cited______24 and hydrologic units______a4 u Meade, R. H., cited ______11,25,38 strata of Etchegoin Formation.. ______16,18 16,17 strata ofJacalitos Formation______14 Ultramafic intrusive rocks, Franciscan Forma- Measured sections, Etchegoin Formation...... tion. __ .______10 Jacalitos Formation______14 Sedimentary rocks, Cretaceous______10 lower Tertiary.••. ______.______11 Tulare Formation______11 Ultramafic rocks, magnesium______11 Serpentine..•• _____ ------10 Upper Cretaceous sedimentary rocks______10 Mendota.------25, 39,40 Shell Oil Co ______20,30 Mesozoic rocks, significance______11 Upper Tertiary and Quaternary deposits un- 13 Micaceous sands, Sierra Nevada•. ______33 Sierra Nevada _____ ------9, 23,39 differentiated.•• ______Sierra Nevada, water-bearing. ______18,a9 alluvial-fan deposits .• ______. __ ._____ 18 Upper water-bearing zone, chemical character. 38 waters .. ______38 Miocene deposits.______11 crystalline complex.______8 Jlood-plain deposits ______S8, 35 U.S. Bureau of Reclamation ______4, 23,24,25 Mode of origin, Etchegoin Formation...... 17 micaceous sands ... ____ .. _____ ... ___ ._____ 33 Monocline Ridge______30 water-bearing micaceous sands ______S8,a9 Monterey Shale, McLure Shale Member..... 12 v Montmorillonite.•.• ______11, a8 Sodium chloride.______40 Vallecitos syncline______11 in saline water body______40 Vallecitos Valley._.______13 Montmorillonite-illite.------___ 11 Veins, gypsum .•• ______------______21 Moreno Formation•• ______4, 11, 11 Sodium concentrations in ground water..•• a8, a9, 40 Soils ..••. ______. _____ . __ . ____ .. __ . ____ ._ aa Moreno Gulch .••• ______4 Volcanic ash overlying Corcoran Clay Mem- Mudstone, Moreno Formation .•. ______11 Stratigraphic relations, Etchegoin Formation. 17 ber of Tulare Formation... ______23,14 Jacalitos Formation.______Myra zone, San Joaquin Formation....• ______SO, 21 to San Joaquin Formation. ___ ------SO W,Y N Tulare Formation.______sa Stratigraphy of the water-bearing deposits.... 1a Warthan Creek, dissolved solids______39 North Dome of Kettleman Hills .• ______16, 21, 23, 30 Stream basins, areas of generalized geologic drainage basin ______------__ -~- 11 North Dome on La Ceja .•.. ______21 units within______11 Water-bearing deposits, geologic mapping_.. 5 Stream waters, chemical character______a9 stratigraphy. ______.-----______13 0 Structure••• ______8 Oilfields. ______14 Water-bearing micaceous sands, Sierra Ne- Subsurface character, Tulare Formation______14 vada ______S8, 39 Opalized wood fragments, Jacalitos Forma- Subsurface deposits, lakes______80 Water-bearing zone, lower ______34,3o,39 tion._--... ______. ______14, 15 Subsurface extent, Etchegoin Formation______17 lower, waters ______---__ 39 1o Origin, Jacalitos Formation______Jacalitos Formation______1o upper ___ • ______34, 35,39 Oro Loma Formation______5,1a San Joaquin Formation______SO waters .• ______38 Ortigalita Creek.. ------______21, sa Subsurface geology, fresh-water bearing de- Waters, lower water-bearing zone______39 Ortigalita Peak quadrangle. ______4, 5, 23 posits .•••.. ______a4 upper water-bearing zone______a8 Ortigalita soil series .•••.. ______33 interpretation •.• ______5 Well-numbering system __ ------8 p Sulfate concentrations in upper water-bearing Wells, chemical changes in water samples_____ 41 zone •. ______a8 deep, chemical character______40 Paleocene marine sedimentary rocks______11 Surface extent, Tulare Formation______S1 Etchegoin Formation______17 Panoche Creek •• ______38 ground-water reservoir.------34 alluvial-fan deposits.______lo T irrigation ______28,.35, 38 dissolved solids.______a9 Taylor, Dwight, quoted ____ ------24 Kettleman Hills______11 Panoche Formation.______10 Tejon Formation______12 lower water-bearing zone.-. __ --___ ------34, 40 Panoche Hills •. ------4, 5, 12, 21, 22, 25, 30,33 Telsa Formation______12 observation______38 Panoche soil series •• ______33,34 Temblor Formation •• ______1a San Joaquin Formation ____ ------SO Panoche Valley______13 Big Blue Serptinous Member.______1a upper water-bearing zone. ______34,35,40 Poland, J. F., cited______34 Temperature, water from wells in lower water· water..•. ______------15 Previous investigations.______4 bearing zone .. ______3o,a8 Westhaven ______20, 30,38,40 Purpose ofinvestigation .. ______4 water from wells in upper water-bearing White, R. T., cited------43 3o zone •. ______Wisnor Formation------10 Q,R Terrace deposits, stream.. ______aa Woodring, W. P., cited ______15, 16, 17, 20, 21,24,30 Quien Sabe Volcanics______11 Thickness, Corcoran Clay Member of Tulare Rainfall, annuaL______2 Formation•..• _____ ------______ao, a4 Yield factor, defined .• __ • ___ ._·------.----- 84 Reconnaissance mapping •• ______o Etchegoin Formation______17 Yokut Aandstone.. .••..•• --·------··· U

U. S. GOVERNMENT PRINTING OFFICE: 1971 0- 411-341