Energy 2 ~~2 / TEI-.&9- TEITEl i 769769 - , ' 1111/lllllil/Jli~lillll/WII c. "I 1 08 0004801488 GEOLOGIC SUMMARY OF THE CENTRAL VALLEY OF CALIFORNIA, WITH

REFERENCE TO DISPOSAL o~ tIQUi n

R A D I O A C T I V E W A S T' E

By Charles A. Repenning

. t '

Trace ElementJ

UNITED STATES TEI-769

UNITED STATEs DEPARTMEM' OF THE INTmIOR

GEDLOGICAL SURVEr

GIDLOGIC SUMMARYOF THE CmI'RAL VALLEr

OF CALIroRNIA WI!I'H R.EF'1!RmCE TO THE DISPOSAL

OF LIQUID RADIOACTIVE WASTE*

By

Charles A. Repenning

June 1960

Trace Elements Investigations Report 769

This report is preliminary and has not been edited for conformity with Geological SUrvey format and nomenclature.

.. , '" ' "'." ~PTeparedc on. behalf ..of the U. S. Atomic Energy Commission. �---

USGS - TEI-769

RADIOACTIVE WASTE (U C - 70)

Distribution No. of copies

Division of Reactor Development, Wasb;lngton • • • • • • • • • • 25 Office of Technical Information Ex:tension, Oak Ridge ••••• 6

U. S. Geological Survey: Geologic Division. • • • •• • 0 • 0 0 • • • 0 • • • • • • • • 44 Water Resources Division • • o 0 • • • • • • • 0 • • • • ••• _....l7~5_ 150 CONT:EMS

Page Abstract------_ 1

Introduct1on------.'.__ 2

Strat1g:roaphy"-- . 0<3- _ 7 Pre-Cretaceous rock~------_ 9

Cretaceous a __ ~ • _ rocks------10 Shasta ser2es------_ 10 Chicosenes------_ J2 Tert~ rocks------_ 15 Paleocene rocks------.------_ 16 .El)cenerocks------_ 19 Oligocene rocks------_ 29 Miocene rocks------~---- _ 32 Pliocene rocks------_ 43 Pleistocene rocks------~------_ 48 Structure------_ 49

Waste disposal possibilities------_ 53 Reservoir rocks------_ 55 Sandstone reservoirs------_ 55

Artificial reservoirs in shale units------_ 57 M1gration barriera------_ 57 Other considerations------• _ 60

Selectedreferences------·------_ 63 -==:~---

Page

Figw;oe 1. bdex map showiDg generalized geology of Califomia-- 6

2. Thiclol.ess of sedimentary rocks in the Central

Valle,y of Californi&------______Ia pocket

3. Ncmenclature and. correlation of selected

stratigraphic units in the Central Valle,y of CaliforDia------______In pocket

4. Distribution and thicl!J!.essof Cretaceous

sediments at the beginning of Tertiary time

in Central Valley of California------______11

5. Distribution and thickaess of Paleocene and lower

Ebcene sedimeIlts at the beginning of late Ehcen.e

time in C~tral Valley of California------_____ 17

6. Distribution and thickness ot: upper Ehcene

sediments at the beginning of Oligocene time

in Central Valley of Cali:f'ornia------______23

7. . Distribution and thickness of Oligocene sediments

at the beginning of Miocenetime in Central Vall~ of California------~______30

8. Distribution and thickness of lower Miocene

sediments at the beginning of middle Miocene

time in Cstral Valley of Californ1a------_____ 34 ILUJ~ONS

Page

~igure 9. Distribution and thickneii of middle Miocene

sediments at the beg:inuingof late Miocene

time in Central Valley of CaJ.ifornia------38

10. DistributioJl and thickaess of upper Miocene

sediments at the beginping of Pliocene time

in Central Valley of CaliforDia------40

11. Distributioa ad thickness of Pliocene sedimewta

at beg;Jnpipgof Pleistocene time in Central

Vall~ of CalifarRia-.------.------44 12. Structural elemeD.taof the Central Valley of California------ID poCket

13. Proba.blemaximum seismic intensity of the

Central Valley and adJa.cent areas of Caliform1a------52 14. Oil and gas fields and well delillilityof Central

Va1l~------~------.------62 1

GEOLOGIC SUMMARYOF THE CmlTRAL V.AI.LEr OF CALIFORNIA

W1TH R.EF:ERmCE TO THE DISPOSAL OF LIQUID RADIOAC'l'lvE WASTE

By Charles A. Repenning

ABSTRACT

The Central Valley of California lies west of the Sierra Nevada.and

east of the Pacific Coast Ratlges. It is about 450 miles lcmg and bas an

average width of about 40 miles. The northern part is drained by the

Sacramento River aad ia called the SacramentoValley. Much Of the southera

part is drained by the Sa.li Joaquin River and the remainder bas 8J1 interior

drail'lage; the southern. part is called the San Joaquin Valley.

As muchas 6 miles of sedimentary rocks acc"nD,lated in the Sa.n JoaquiB

Valley and as muchas 10 miles in the SacramentoValley. Most deposits in

the Sacramento Valley are composedof Cretaceous sandstone and siltstolle

with little regional variation. The deposits in the San Joaquin Valley, by

contrast, are largely Tertiary sandstone, siltstone, and claystone with

great regional variatiOl!l.in rock types. The complexity of the facies of-

the Tertiary rocks bas resulted in a large stratigraphic namenclature, aad

muchof it, because most of the information is :from well data, is loosely

defined and of informal nature. It is, nevertheless, widely used, and must

be used in ~ regional SUIlIlllS.rY of the stratigraphy. Cretaceous deposits are largely marine, but the Tertiary rocks contain a high proportion of continental deposits tllat are increasingly abundant in the younger parts of the stratigraphic sectioll. Many stratigraphic traps of several types are present tllat might be used to store liquid waste. The potel1tially usef'ul stratigraphic storage reservoirs are cClllllllOnandthe selection of more favozoableareas for waste disposal is iD.f'lueacedby areas of favorable geologic structure. 2

INTRODUCTION

This report has been prepared as a part of the Radioactive Waste

Disposal Program of the Division of Reactor Development, Atomic Energy

Commission. It is the second of a series of reports covering areas

underlain by sedimentary rocks in the United States. The first was a

summary of the San Juan Basin, New Mexico, released to open file in

September 1959 as TEl 603 (Repenning, 1959).

These reports describe the geology of the area only to the extent

necessary for preliminary evaluation of the possibilities for the disposal

of liquid radioactive waste by injection through deep wells. Their value

will increase with development of extensive commercial production of

atomic power and attendant creation of radioactive waste from the processing of spent fuel elements. The disposal of liquid waste in deep reservoirs is only one of several possibilities that must be considered.

Many factors must be considered in disposing of radioactive wastes, such as certainty of containment for the duration of hazardous radioactivity, monitoring requirements, regional and local hydrology, engineering problems, and cost. These factors can be more adequately evaluated when a specific disposal site is considered. Although this report is not sufficiently detailed for specific site selection it may be used as a guide to more favorable areas through the generalized picture of the important subsurface geologic conditions. No recommendations for any site, medium, or method for waste storage are made. But areas are pointed out that appear more favorable for waste disposal under certain assumed conditions, chosen to provide a basis for discussion of waste disposal possibilities. 3

This report is based on existing literature except tbat unpublished vertebrate fossil records on flle at the University of California,

Berkeley, have been used in establishing someage relations and correla- tions. These data are not mentioned in the text, and their effect will be noted o~ by those who are 1'am111ar with the stratigra~ of the area.

The author has accepted or mod1f1edpublished records to the best of his Judgpvmt, as otherwise the report would be a maze of conflicting statements. Unless di.rectly quoted, references to pUblished material in the following text do not necessa.ri1y re..-f1ectthe precise meaning of the person cited.

The stratigraphy of the Central Valley of California has many currently irreselvable problems, partly regard1llg temporal equivalents of rock un!ts but particularly regarding assignment of these rock units to standard time divisions of the Cretaceous and Tertiary. Temporal equivalence of different rock units is important in establishing the areal extent of units of possible significance for either oil exploration or waste disposal. Differences in intezpretation of local correlations in the Central Valley of California are few, and most of the correlations shownon figure 3 and discussed in the text are reliable. Question marks indicate tbat same uncertainty exists. Correlation of rock units within the Central Valley to the standard rock chronology of the world is subject to diverse opinions, which, fortunately, have no bearing whatever on the problems of waste disposal.

In accordance with the custom of discussing the stratigra~ of any area. in terms of the standard rock ages of system and series, the author has adopted the most CC'III1I!Ollly used age assignments of the rock units. In same cases these assignments to series disagree with those of The Geolog:1c 4

Names CO'JDlIlitteeof the U. S. Gi;olegical SUrvey, 8.lldin some cases the

author believes other assignments more reasonable.

Subdivision of serie$ into upper and lower (or upper, middle, and

lower) parts will. undoubtedly be questioned by sane readers. The sub-

d1.v:1sions of series show:m on figure 3 and used throughout the text are

used by the author o~ for arrangement of the stretigrapbic discussion.

They are cOlZvenient gI'OlIps af rock units which can be discussed as an

entity throughout the Central Valley and have no :1m;pliedcorrelation to

upper, middle, 01: lower divisicms of the type series in Eu.."'OIle• Thus,

the series subdivisiolllS are a purely artificial device for convenient

grouping for the pu..-pcses of the present report, and the same is true of

the series assignments, except that they represent the majority of

published opinilrjl1S.

In. order tAl> expla.in the assigned age of stratigraphic units Sh01rlll

in the age c01UI1!!1of figure 3. it was necessary to include the three

Pacific Coost faunal "age" scales. One e.xampleillustrates this need.

In severaJ. areas in aJlldadJacent to the Centr.aJ. Valley. the santa Margarita sandstone contains both continentaJ. vertebrate and marine molluscan faunas. The vertebrate material indicates an early Clarendonian provincial manpnalianage, and the IIlQllusks indicate a Cierbo or Neroly mega.f'aUJ:!.BJ."age."~st workers correlate the Clarendonian with the lower

Pliocene of E;Jropeand the Neroly and Cierbo with the upper Miocene of

~e. The assignment of the Santa Margarita either to Miocene or to

Pliocene on figure 3 WIOuldimmediatelyarouse debate, but the assignmwt to the Clarendonian, the De1montianand Mohnian. and the Neroly and Cierbo

"stages," zones, or provincial stages is specific and valid. The assign- ment of the San-ta. Margarita to the upper Miocene is arbitrary and admits 5

variatiOll. Its correlation to the three "age scales" of f1gure 3 is based

upon faUDaJ.ell'id.enc::e. Similar examples.of disagreement of correlation with

the standard European series are present throughout the Tertiary and be-

tween all. three faun.a.l age d:!.sciplines. The colU!llMdo not concern local

stratigrapb,y but are included as explanation for relations to areas beyond

the limits of the Central Valley of California.

The geology 111~ parts of the Central Valley is poorly known be-

cause the older rocks are masked by younger Pleistocene and Recent

sedimentS. 0Dl,y in scattered areas around the margins of the valley,

mainly en the west side, de the older rocks crop out. Therefore,

knowledge of the geology in the covered parts of the basin is dependent

upon the amount of subsurface data ava.11a.ble. These data tend to be

concentrated in local areas of ec>oonmicinterest, and many large areas w:i.thin the valley are still undrilled. 0n1,y published subsurface data have been used 1n preparing this report. Unpublished well data in many areas are available oDly after negotiation with the operating companies.

The stzatig:re,phic namenclature of the Central Valley shown on figure 3 ref.lects this lack of av'ailable information. Many informal rock names are in ctllIllllOnuse. These units cannot be defined more precisely until correlations between areas can be established by detailed work-.

The Cent:raJ.Valley of California, also calJ.ed the Great Valley of

CaJ.i:fornia, is nearly flat west of the Sierra Nevada and east of the

Coast Ranges (fig. 1). It is about 450 miles long, extending from the

Tehachapi z.i)untains on the south to the IC1.alIIa.thMountainson the north.

The valley has an average w1dth of about 40 miles and a maximUm w1dth of about 75 miles. Most of the valley is near sea level and all of it is below 1,000 feet in elevation. - ~ --

6

REG 0 N EXPLANATION v •

F:::) Q\,laterury and Tertiary ~ sedimentary rocks z Tertiary volcanic rocks

Cretaceous and Jurassic III sedimentary rocks Franciscan group ~ Pre-Cretaceous sedimentary mIlJ and metamorphic rocks Plutonic rocks and other igneous ,::~i and metamorphfc rocks ---""... Fault

eo 120 160 200 MILES

- Bas in

and A" E DESERT Ron g e o

Province

Figure 1. --Index map showing generalized geology of California. 7

The northem part of the Central Valley is called the Sacramento

Valley and the southem part is called the San Joaquin Valley. Rivers of the same name drain most of the area, entering the Pacific Ocean near

San Francisco. The southern half' of the San Joaquin Valley has interior draina.ge.

STRATIGRAPHY

The Centre.l Valley is a northwest-trending structural trough that has been. 1'1lled with a thick sequence of sedimen:ta.ryrocks rang:!ng in age f'ram

Jurassic to Recent. In general, the rocks of Jurassic and Cretaceous age are lIIOre widespread in the sacramento Valley and the Tertiary rocks more widespread in the san Joaquin Valley. The deepest part of the trough is alOI!8 the westa.-rnedge of the vaJJ.ey, where as much as 6 miles of sedi- mentary rocks have accumnJated in the San Joaquin Valley and as much as

10 miles have acclD!D,latedin the sacramento Valley (fig. 2).

The thick sedimentary sequence rests on a basement floor composedof metamoz:phicand granitic rocks. These basement :rocks crop out in the hills surro1.mding the Central Valley and have been reached by wells in many areas. Eastward !':rom the deep part of the basin, the basement floor rises gen:tly and is apparently continuOUSwith the surface cut on the metamorphic and granitic rocks of the westiiard_tllted Sierra Nevada block.

The western side of the Central Valley is probably 1.mderlain by basement rocks similar to those forming the care of the California Coast Ranges.

These rocks 1n.clude the "Franciscan" formation, consisting of a hetero- genous mixture of graywacke, shale, basalt, chert, and serpentine, all of which locally have been metamorphosedto glaucophane schist, and graD1tic rocks that occur in large isolated fault blocks. 8

The granitic rocks around the Central Valley are Meso~oic (pre-Late

cretaceous) in age p and the "Franciscan" is in part Cretaceous and in part

Jurassic. One of' the unsolved problems in Call1'ornia is the correlation

between the ''Franciscan'' of the Coast Ranges and its umne1;a.morphosedage

equivaJ.ents in the Sacramento Valley (Irwin, 1957). "Basementcomplex" is

the term generaJ.J.y used for these older rocks in the Central Valley, and

no attempt will be made to describe or discuss them further.

Cretaceous and Tertiary rocks of marine and continental origin attain

a maximumthickness of about 10 miles (fig. 2) in the deepest part of the

Central VaJ.ley. These rocks are composedalmost entirely of clastic material derived f'rom surrounding upland areas. Sandstone, siltstone, and

claystone are the dominant lithologic types, and significant amounts of

carbonate rocks are completely absent.

The Cretaceous section is characterized by lithologic cont1nu1ty over large areas. Thick lithologic units have been traced throughout muchof the west side of the Sacramento Valley (Kirby, 1943, p, 303-304), and some sf these urdts bave been correlated with f0l111B.tionsofSimila.r lithology alODgthe west side of the San Joaquin VaJ.ley, although south of' )bunt Diablo Lowerand someUpper Cretaceous units are absent.

Cretaceous d.eposits are apparently absent in the southern part of the san Joaquin Valley where the Tertiary rocks attain their maxiuulDl thickness.

In contrast to the regional lithologic similarity of the Cretaceous rocks, the Tertiary section is highly variable, particularly in its younger part, and ma.IJ;Y rock units ~ correlated with considerable uncertainty over distances of only a few miles.

The Cretaceous sediments were probably derived largely f'rom the rocks that at one time covered the granitic mass of the Sierra Nevada, but 9

loca.l1zed so-arce areas :iD. the Coaat Ranges to the west may also have COIl-

tributed. Tertiary rocks, by cootrast, are more arkosic and presumably

were derived :f'rGm the gr.an1tic batholith of the Sierra Nevada. In some

areas 1 marl.ne Cl'etacetmS rocks may have covered large areas between the

present Central Valley and the Pacific Ocean. The Tertiary Central

Valley was structurally more distinct than the Cretaceo'.lS basin and

pMbably had only a restricted cmmectioo with the Pacific Ocean.

The oldest k!:IIlJwn sedime:nta.:J:y unit in the Cer.t:rel Valley is the

Kno.xv1lle f'o:rma.tionof Late Jurassic age. It crops out locally along the

west side of the Sacramento Valley f'nm1 the north side of M:>untDiablo

northward to Paskenta. The easteza li!llit of the Knoxville is unknown.

The Knoxville cOWlists :mainly of' well-i.D.chL..-atedmarineshaJ.e and silt-

stone as muchas 10,000 feet thick. Loca1.ly present are relatively thick

units of impermeable axgflJaceous sandstone and conglomerate, an"- minor

lenses and thin beds (Jf U.mes~.

The base of' the f'or.ma.tionis not exposed in the Sacramento Valley.

In. :most areas the contact with the overlying Cretaceous rocks is

gradationaJ., and similar lithologies above and below the contact represent

contiIlul>us deposition :f':N:lm Jurassic into Cretaceous time. LocaJ.ly an

uncooi'ormity is reported between the two units, and in other areas a

conglomera:l;eis arbitrarily selected as the base of the Cretaceous.

Marine fossils indicative of a Late Jurassic age are locally present in the

KDoxvi...lle. �-

10

Cretaceous rocks

Lower Cretaceous rocks are present only in the Sacramento Valley but

Upper Cretaceous rocks are found throughout the Central Valley. The

Cretaceous rocks have a maximnmthickness of about 25,000 feet in

Sacramento Valley and are about 20,000 feet thick near Coalinga in the

San Joaquin Valley (fig. 4).

Lithologic simi1ari ty throughout the thick Cretaceous section has made division into formational units difficult, and faunal changes are

generaJ..1ymore distinctive than changes in rock type. Rocks of .Early

Cretaceous age are often assigned to the Shasta series and rocks of Late

Cretaceous age to the Chico series. Local formation namesare frequently used within this series classification.

Shasta series.--The Shasta series, present only on the west side of the Sacramento Valley as far south as MountDiablo, consists of about

10,000 feet of mudstone and siltstone with someinterbedded conglomerate and argillaceous sandstone. Nodules, lenses, and thin beds of limestone are present in minor amounts. The Shasta series has so little litho- logic variation that it has not been divided into formations in most areas. Its fauna. has been divided into the older Paskenta stage and the younger Horsetownstage. Murp~ (1956) has namedtwo lithologic units in the northern SacramentoValley. These are the Rector formation, consisting of about 400 feet of sandstone, conglomerate, and mudstone that rests on an igneous basement; and the overlying OlIo formation, consisting of 4,200 feet ot mainly mudstoneand siltstone (fig. 3, column2). The <>no contains two conglomeratic and argillaceou sandstone tongues. Murp~ correlates most ot his section with the Horsetown stage ot the southern SacramentoValley; a considerable part ot the older 11

~~",+, J .. I I EXPLANATION ,,~ ~. I , ...... 2ZJ..... ~ ~'" I / I rr'" ...... 1-:..' ••••••• ';.....,..,...... ·11/ 'I . .'?\ MARINE CONTINENTAL DEPOSITS DEPOSITS .: /'\ 40· HEAVY LINE SHOWS PRESENT L1UITS OF \' SEDIMENTARY ROCKS IN THE CENTRAL VALL£Y \

. ("'l.\ \ \ \ SCALE IN ""LES \ , 01030.0 . ~ \ "Q. \ • • o 'I> \ .\ \ ... ~ \y I} I. ·1 ~ N

se·

o

3.·

SOURCES

SACRAMENTO VALLEY-- Jenkins, 1943, with some modification. SAN JOAQUIN VALLEY-- Jenkins, 1943 and. Hoots, Bear, and Kleinpell, 1954a, with some modification. SANTA e.RIARA --~1200~

FIGURE 4. Distribution and thickness of Cretaceous sediments at the beginning of Tertiary time in Central Valley of California ... 12

Paskenta stag@ is absent» as is the Km:'rJl:v1lleformatiQll\.No one has

applied Mu:t:PbY'1i f'orma.tional M.meS farther sooth» and most of the Shasta

series of the Cent;ml Valley xemaiJlJswdivided.

Chico series. ==TheChico s~l'ies is .IIl1'J.cll. lOOIl'e widespread than the

olde.I" sed1lllen"t,axyrocks and is pl"esent throughout the Sacramento Valley

and the northern San Joaqui». Valley. The contact between the Shasta

sel'ies and the Chico sel'ies of Late Cretaceous age appears to be campletely

gradational a.nd is based ma1J'!1.y Olll chalPges:in the fauna. AtteD!Ptsare

usually made to place tJle contact at a lithologic cbang~ near the faunal

OOWl.dary. In gxIl)6S li tl:wlogy the Chico se:rles is similal" to the Shasta

and Klwoorille but contains oore sandstone and a greater variation of

lithologic types. The average thickness of the Chico is about 15»000 feet

in. the western pan; of tille Sacramento Valley, a.:adin general·i t thins to

the east and northeast. This +,binning represents both a reduction in

thickness of correlative stratigraphic units and the eastward onlap onto

basemex!.trock.

The litholl'»g1c variation of the Chico series is illustrated by the

number of formations and membersthat have been recognized in the Central

Valley. These Wlits are generally interbedded sandstone and shale and

have been variously named»or numbered, in different areas. Kirby (1943)

recGgD.1zedsix such un!ts of the Chico in the western part of the

Sacramento Valley. Others have included a seventh, a thick shale unit underlying Kirby's lowest f'orma.tio!J.»not on the basis of lithologic unity but because it contains Late Cretaceous fossils (fig. 3, column 1).

The Chico senes in Kirby's area consists of about 50 percent sand- stone and 50 percent siltstone and claystone. Three of his fO:nDat10ns

(the Guinda» Sites, and Venado)are sandstone units 1,000 to 4,000 feet - ----=-- ====-

13

thick. These sandstone units are largely fine to mediumgrained and quite

argillaceous. They are interbedded with minor amounts of shale, and con-

glomeratic beds are locally coxmnon.

FB.stwardfrom Kirby's sections the Chico series thins and becomes

increasiDgly san~. In the Marysville Buttes area (fig. 3, column3) the

exposed section is about 2,750 feet thick (Kirby, 1943, p. 301) and con-

sists of about 35 percent shale and 65 percent sandstone that varies from

fine grained and argillaceous to very coarse grained. Subsurface infor-

mation north of Marysville Buttes indicates that the total Upper

Cretaceous section is lIllOrethan 4,500 feet thick. The unexposed part of

this section is predominantly shale, and the uppermost 700 feet, in-

cluding the fine-grained micaceous and very argillaceous "Kione sand," is

of uncer-taan age and may be Paleocene rather than Cretaceous. These

younger units are not present in the western part of the Sacramento

Valley.

In the northern part of the Sacramento Valley, east of Redding

(fig. 3, colUJllll2), Popenoe (1943) has divided the 4,000-foot Chico

section into six numberedunits, of which three are clean, fine- to coarse-grained, co:oglomeratic sandstone. These units range from 200 to

1,000 feet in thickness and makeup about 45 percent of exposed section.

Popenoe's units seem to be correlative with the middle part of the Chico on the west side of the Sacramento Valley. In general the sandstone units of the Chico in eastern and northern Sacramento Valley contain less argillaceous material and are coarser grained than those along the western side of the valley.

Nearly continuous outcrops of the Chico are found from Mount Diablo southward to Coalinga. Here it is subdivided into two units, the PaDoche 14

:forma;tion and the Moreooformat1onp part of which is o:f Paleocene age.

Locally both the Pa.uocheand the MQrenoare divisible into members. In the

Mount Diablo area Ta1'f (1935) recognized a third unit beneath the Panoche

and overlyiDg the Shasta series (fig. 3, column 6). He re:ferred this unit

to the Chico :fo:nnation. a usage in conflict with the term Chico series.

Taf:f abandoned the Chico as a serieS name and referred the three formations,

Chico, Panoche, and Iobreoo. to the "Upper Cretaceous series." The Chico

series is about 19.000 :feet thick ill the Mount Diablo area but thins

rapidly southward to about 113000 feet in the Coalinga area (:fig. 3,

column 10). This thinning may be due largely to the loss of Taf'f's Chico

fonnatiollp which is about 7,000 feet thick in the Mount Diablo area.

Ta.f':f" s Chico fonnation (1935, p. 1088) has a basal membercomposed

primarily of ~d.stone and conglomerate that is nearly 1,000 feet thick.

This memberis overlain by about 1,000 :feet o:f JJ..m.y and cherty sbale.

The remaining 5,000 feet are composedof interbedded thin sandstone and

shale units. Similar interbedded sandstone and shale, with some con-

glgmera;te, continues t.hroJughoutthe overly1ng 5,000 feet of the Panoche

fO:rnJat1on. However, southward from MountDiablo the sand content of the

Panoche increases and two prominent sandstone units become recognizable.

In the Coalinga area, these have been namedthe BrownMountain sand

member, at the top o:f the Panoche, and the Joaquin Ridge sandstone member,

separated fiImn the BrownMountainmemberby a thick shale member(fig. 3,

col1JmIlS10, 11). These sandstone membersare fine to mediumgrained and

composedof angular 1;0 subangular grains of quartz and feldspar. They are

relatively free of argillaceous material. In places they are somewhat

conglomeratic and much of the sandstone is concretionary. The Joaquin

Ridge sandstone memberis as muchas 4,400 feet thick, and the Brown 15

Ikluntain sand member is about 350 feet thick. Near Coalinga the Panoche

rests unconformably on Franciscan basement rocks and is in part older than

the Panoche of' the Mount D:1ab10area.

The contact between the Paooche formation and the overlyiDg Moreno

formation appears to be gradational over IIIOstof the western side of the

SaD Joaquin Valley, although Taff'mentiol1S the possibility of an UI1COl1-

f'crm1ty separating the two formatiol1S in the Mount Diablo area. The

Moreno formation has an average thickl1ess of about 2,000 feet, although

Ta1'f' (1935, p. 1089) est:iJDates a thickl1ess of 7,000 feet in the J&)UI1t

Diablo area. The uppermost 1,000 feet is Paleocene in age (Payne, 1951, p. 11). The Moreno is composed of brown, red.d1sll--broWl1,and gray sbale, with some massive sandstone beds in the IIIOrenorthern outcrop areas. Some parts are s1l1ceous and other parts are calcareous; platy dia1;imla.ceous shale units as much as 200 feet thick are locally present.

The uppermost part of the PaI10cheand all of the Moreno are younger than the Chico series 111the western, IlOrthern, and IlOrtheastern parts of the Sacramento Valley. They seem to be approximately correlative with the outcrop section of the Chico at Marysville Buttes.

Tertiary rocks

The greatest accUDDllation of Terti.ary rocks is near the southern end of the San Joaquin Valley, where IIIOrethan 6 miles of sediments have been deposited. Tertiary' depositional history is IIIOrecomplex than that of the

Cretaceous because of IIIOretectonic activity. Rapid lateral changes 111 t.b.1ckDess and lithoJ.ogy of the Tertiary rocks have resulted 111a large number of formational units, both formal and 1I1formal (fig. 3), and com,plicate 8ZJY attempt at regional synthesis. 16

Paleocene rocks.--Rocks of Paleocene age are present in the northern part of the San Joaquin Valley and probably extended into the southern

Sacramento Valley. (See p. 13, discussion of "Kionesand.") In most areas , deposition was continuous :from Cretaceous into Paleocene t:iJneand from Paleocene into early liDcene. Therefore, the time boundaries do not correspond with the formational subdivisions, and it bas becomecustomary to discuss rocks of paJ.eoceneand liDceneage, separating rocks of liDcene age from rocks of Late Cretaceous and Paleocene age, which are grouped together as of Paleocene age.

A high area of Cretaceous rocks, known as the stockton arch (figs. 2 and 5), separates Paleocene, liDcene,and perbaps Oligocene rocks of the southern SacramentoValley :from similar rocks in the San Joaquin Valley.

Available inf'ormation suggests that the stockton arch is related to the uplift south of MountDiablo (fig. 5) whichbecameactive during Late

Cretaceous time. It seemsprobable, therefore, that dlIriDg the early

Tertiary the southern SacramentoValley was a separate basin, not connected to the San Joaquin basin but to the Pacific Oceanby a rGute north of MountDiablo through the area nowoccupied by San Pablo Bay and the type Martinez formation. NoPaleocene rocks seemto be present south of the Bakersfield arch in the southern San Joaquin Valley (fig. 2).

The type section of the Martinez formation, exposed at the town of

Martinez about 5 miles upstream from the head of San Pablo Bay, consists of about 2,000 feet of dark silty claystone with thin, hard, glauconitic sandstone and someconglomerate. The type Martinez, however, contains rocks younger than those ordinarilY considered to be of ''Martinez'' age

(fig. 3, colUlllIl7). Southeast of the type section, toward MsuntDiablo, the Martinez thins to 700 feet of caJ.careousshale and brownto green 7

~ __ ..!I~ --- EXPLANATION

...... ·ZillJ· ...... cz.... , ..... ,. MARINE CONTINENTAL DEPOSITS DEPOSITS

HEAVY LINE SHOWS PRESENT LIMITS OF SEOIMENTARY ROCKS IN THE CENTRAL VALLEY

SCALE IN MILES O O-'WICJ'O.. -==':,;O"c=:::i'

N

SAN FRANCISCO

o .e·

;, 8~KERSFIELO SOURCES ~-,.. 11 .,.fL/. 0 ~q.Okerat'eld NORTH OF STOCKTON ARCH--'- ~ Several sources but information very approximate SOUTH OF STOCKTON ARCH-- Hoots,Bear,and Kleinpell,19540, with slight addition. SANTA e.RBA". \..--~ 120°.-----0

FIGURE 5. Distribution and thickness of Paleocene and lower Eocene sediments at the beginning of late Eocene time in Central Valley of California. 18

audatoae. The format:!.o..pachea out a ahort diatuce aouth of Mouat Diablo.

It ia pres eat a the aubsurface to the east aad aortheaat ud may grade laterally iA thia directioJl ato au~ facies web aa are exposed beaeath

the so-called MegaaOIiformatio.. at Maryllville Buttell. From the }.i)u:atDiablo

area Ilouth to Pacheco Palill ..0 IMartiAez" beda are prellelltj however, Ilouth

of Pacheco Paaa beda of lleem1Bg1y1l1m11a:ragebut of differellt lithology

are preaeat. Theile beda were alllligaed to the Laguu. Seca formatio. by

Payae (1951) ud are primarily a ailty, micaceous, fille-graaed IlUdiltolle

(fig. 3, co11.llllll\8). Farther aouthward, they aeemto grade uto the

Cerroll shale memberof the Lodo formatioll (fig. 3, C01UlDll9).

Eastward from the welltera Ilide of the 8aJl Joaquill Valley the Martuez-

equivalent rocks are present beneath muchof the ceatral part of the

valley. However, in the eastera half of the valley they are truacated by

oae of the most signific&JLt Ullcoaf'ormities of the area. This uacollf'ormity

ia overlaiD. by the upper Ebceae Dome»ginesandlltolle or by youager rockll

which overlap the Domeagine. These wlits above the Ullcoaformity maybe

equivaleat to part of the cOlltilleatal Saildlltollebedll called the Walker

formatio., although a someareas the Walker may cOJataillbedll all youag all

early Mioceae. YOUllgerPaleocene rocks of the Su Joaquia Valley cOlltaill more fiae-

grailled to coaglomeratic sudlltoae ud are relatively free of aigaificut

amou:atsof argillaceous matriX ud probably are quite permeable. Ia

add!tio. to beag illterbedded with shale u:ai t., the .udato.e Ull1til them-

selves co.taill sEllllerelatiVely thia .hale bedll. They are illcluded ill the

lower part of the Megees fermatio. (u:ader aeveral aames or lettera) ud

poaaibly ill the lower part of the Cutua sudato.e memberof the Lodo

formatio.. The Cutua member,however, is geaerally co.ddered to be part

of the lewer Ebceae sectie •• 19

Eocene rocks.--Eocene rocks are widespread in the Central Va.ll.eyand are separated into lower and upper parts by a region.a.l UD,coD!o.rm.ity.

Lower Eocene deposits in the Sacramento Valley, overlyiDg the Paleocene

Martinez rormation or older rocks, are assigned to the Capay and the

Meganos rormations, and those in the northern San Joaquin Valley are assigned to the upper part Qf the 1000 rormation or its correlatives and to the Yokut sandstone or correlatives. No early EDcenedeposition is recorded in the southern San Joaquin Valley south of the Bakersfield arch, a paleogeographic situation inherited from the Paleocene.

Lower EDcenerocks of the Sacramento Valley are present over a

larger area than Paleocene rGcks. They are exposed on the west side or

the valley, 'Wherethey overlie Cretaceous rocks, and seem to be present

in most or the valley as far north as Chico. From Chico southward at

least lj() miles the major part of the lower EDcenesection is confined in

a deep narrow subsurface gorge (Frick, Ha.rding, and Marianas, 1959).

(See fig. 5, "Capay gQrge.") The older EDcenerocks of the Sacramento Vall.ey are all. referred to the Capay formation except in the »:>unt Diablo

area and nearby subsurface sections, Here (fig. 3, column 6) rocks

apparently equivalent to i;he Capayare called the "E" sh,a.1ememberof the

Meganos rormation (Clark, 19218, p. 187). This is the type area of the e Meganos and seems to be the only plaCe where rocks of early Epcen age

are included in the Meganos. Elsewhere, the Meganollis believed to be

entirely Paleocene and to underlie the Capay formation. The Capay

formation, including the "E" shale memberof the Meganos, is cQlllPOsedor

greenish-brown to gray fetid shale with phOsphatic nodules and beds

conta g dissem ated authigenic pyrite. These rocks suggest deposi- 1n1n 'n tion in a basin with little cirCUlation to the open sea and very 20 stagnant bottom conditions. In some areas the Capay contains a glauconitic sand;y' conglomerate at its base. In general the Capay formation thickens westward; it is thickest at the type section (fig. 3, column 1) near the town of Capay, where crook and Kirby (1935) report 2,500 feet. In the area north of )bwlt Diablo the

"E" shale of the Meganos (equals Capay) is about 1,200 feet thick.

Throughout the central Sacramento Valley, howeVer, the Capay is between

300 and 400 feet thick, except within the buried gorge, which it fills to depths as great as 2,000 feet (Frick, Hard;l.Dg, and MariaIlOs, 1959). T):le

Capay is generally thinner along the eastem edge of the valley and contains san9Btone units, as the Dry Creek sandstone member(or "formation" where the remainder of the Capay is missing) (fig. 3, columns 3 and 4).

The relation of older EDcenerocks in the san Joaquin Valley to the

Capay formation in the Sacramento Valley is uncertain. T):leyare now dis- continuous in the subsurface across the Stockton arch. South of the arch the rocks in the upper part of the Lode formation are generallY" Sirol1ar

1i thologica.l.ly, but-contain a higher proportion of sandstone and less material suggesting a stagnant marine enviromnent• T):lesedifferences

suggest a barrier between the two baSinS, with the northern Capay basin having a IIiOreconstricted connectiOn to the sea than the southern Lodo basin. In the san Joaquin Valley the Lodo fo:rms.tion is composed of silt-

stone and c~stone with sane interbedded sandstcme. Ita lower member,

the Cerros shale, is highly glauconitic and sand;y in its lower part but .

otherwise is quite Similar to the upper memberof the Lodo--the An'03°

Hondo shale member. In parts of the northern and western San Joaquin

Valley, the two shale membersare separated by the Can1;Uasandstone 21 member, a medium- to coarse-grained sandstone containing irOn-stained con- cretions up to 7 feet in diameter. Locally the Cantua.memberis as much as 4,50 feet thick (¥lb1te, 1940, p. 1740). Where the Cautua is absent, 0 the two shale membersof the IQdo are inSeparable. The Lodo formation bas a maxiwDD outcrop thickness of about 5,000 feet but is less than a thousand feet thick in most areas. It is thickest in its westernmost exposures and, like the Capay, thins east1llal'd toward the central part of the northern San Joaquin VaJ.ley. Most of this eastward thinning is a result of the loss of the older parts of the LodD, and in these areas the Arroyo Hondomemberof the Lodo is often referred to formational rank (fig. 3, columns 10 and 11). Because of truncation by the IXuneng:!ne or yOUIlgerformations, the Looo formation is not present in the eastern half of the northern San Joaquin VaJ.ley· The Yokut sandstone (White, 1940, p. 1746) overlies the Looo for- mation and is also cut by the pre_IXunengineunconformity. It occupies a

position comparable to the Dry Creek sandstone memberof the Ca~. It

crops out only aJ.ong the western side of the san Joaquin VaJ.ley between

Coalinga and the PanOcheHillS, where it is less than 200 feet thick.

Eastward, toward the center of the valley, the sandstone thickens be-

neath the pre_Domengineunconformity to as much as 800 feet and is known

as the Gatchell sand. The Gatchell sand intertongues with, and apparently

is locally replaced by, the Arroyo Hondoshale member of the Lodo. It is

the oldest oil_producing unit in the Tertiary section of the San Joaquin

Valley. The Gatchell sand is a light-pink to nearly white, medium- to

coarse-grained, clean, quartzose sandstone. It contains interbedded

claystone and IlDldstonewhich becomeincreasingly abuJldsn:ttoward the areas 22 where the Gatchell intertongues with the ArrOyoRondomember. It 11J8Y be equivalent to the Tesla f'onaation to the north, which hae a max1Dmmthick- ness of nearly 2,000 feet CRuey, 1948) (fig. 3, columns8, 9, 10, and 11).

The Tesla formation pinCheSout along the outcrop northward near

Mount Diablo and is overlaPped by Miocene'lmits. Accord.in8to lluey it is b a white, fine- to medium-grained, well-sorted, massive to t jnly bedded,

friable sandstone interbedded with coal. It is composedof about 75 per-

cent angular quartz and 10 to 30 percent feldspa:t'. BedJ;I 15 to 20 feet

thick have been mined in the Livermore area as a source of glass sand. lluey notes that the Tesla formation, altho1Jgb.containing fossUS

believed to be equ;iva~en.tin age to the 1.Odo formation and the YokUt

sandstone (Capay "stage"), is strjkjngly sirnllar to the DO'Denginefor-

mation, which crops Glutalong a 20-mile belt on the northeast side of

MountDiablo. One60-f'oot bed of' this D:Jmenglneunit has been mined for

glass sand and is a white, fine-grained, well_sorted, compact, quartz-

rich sandstone. It maybe an extension of the lone formation f'rODl the

eastern part of' the sacr.a.mentoValley· The Glder rocks of the central Valley &>cenesection are separated

from the yOUDger&>cenerocks by So pronouncedunconformity. In the sacramento Valley this unconformity is at the base of the lone formation

or its correlatives, or beneath younger units that overlap the lone. In

the northern part of the san Joaquin Valley the unconformity is at the

base of the nomenginesandstone or beneath younger units which overlap

this forma.tion near the marginSof the basin. The younger &>ceIU!rocks

were deposited across the Bakersfield arch and thrOughoUtthe southern san. Joaquin Valley (fig. 6). The similarity of rock types on either side

of' the stockton arch suggests that dllr1IIg late &>cen.etimethis positive -----

23

I O· EXPLANATION o MARINE CONTINENTAL DEPOSITS DEPOSITS

40' HEAVY LINE SHOWS PRESENT LIMITS OF SEDIMENTARY ROCKS IN THE CENTRAL VALLEY

SCALE IN MILES 010 30 ~O o -

N

IAN FRANCiSCO

o

o so'

se'

SOURCES NORTH OF STOCKTON ARCH-- Several sources but information approximate. SOUTH OF STOCKTON ARCH-- ,- Hoats,Sear, and Kfeinpell, 19540,

with some change. . SANTA BARBARA 120°:--.-0

Distribution and thickness of upper Eocene sediments at the beginning of FIGURE 6. Oligocene time in Central Valley of California. 24

area was not an effective barrier, and the absence of late Eocene rocks rm.y be dne entirely to subsequent uplift and erosion prior to Miocene deposition.

In the Sacramento Valley the lone formation is nearly as extensive as

earlier Eocene rocks, but it crops out only along the eastern side of the vall.ey. This tl.Ilit is a poorly consGlidated, nearly massive, quartzose

sandstone with a high percentage of interstitial clay. It has been mined locally for glass and for clay. The lone is present throughout the central part of the Sacramento Valley and grades eastward into the Butte gravels which crop out along the eastern edge of the valley and overlie the

gra.ni tic basement of the western slope of the Sierra Nevada(fig. 3,

column 3). The formaticm is about 200 feet thick throughout most of the area. It is locally over1a1n by shale, which is treated as part of the

formation or as undifferentiated Eocene. Near »:>untDiablo the possible

lone equivalent is interbedded with coal and is about 500 feet thick.

Except for the overlying shale locally present in the central

Sacramento Valley, younger Eocene rocks are absent, and the lone is un-

conformably overlain by a thick sequence of volcanic :rocks of questionable

Oligocene and Miocene age and by continental beds of probable Pliocene age.

The lone tb,erefore represents the last known marine invasion of most of

the Sacramento Valley. younger marine beds, however, are present in the

southern part from the MountDiablo area eastward nearly to the Sierra

Nevada. In the area north of MountDiablo the yaunger Eocene rocks include,

in ascending order, the DcJmeDgineformation,the Nortonville shale, and

the sandstone and shale of the Markley formation. The Damenginefor-

mation is about 1,000 feet thick and consists of a lower shale and coal

unit, 500 feet of sandstone alreactr mentioned as a possible equivalent 25

of the lone, and an upper ~ sandstone. The Nortonville consists of

about 500 feet of gray to dark.brown claystone with silty or san~ units

and a few lenticular sandstone beds. It ranges from 50 to 500 feet in

thickness, with a gradual decrease eastward to within 20 miles of the

eastern edge of the Sacramento Valley, where it is truncated by the un-

con:f'ormity beneath the Valley Springs formation of Miocene age.

The Markley formation is more than 3,000 feet thick near ~t

Diablo and is COlllPOsedofabout three-fourths sandstone and one-fourth

shale. It has been divided into a lower 2,000-foot sandstone member, a

medial shale unit about 700 feet thick, and an upper sandstone unit about

500 feet thick (fig. 3, column6). The sandstone units are gray, very

micaceous, mediumgrained, and carbonaceous. The shale units are gray

to brown and contain silt, clay, and carbonaceous material. The Markley

thins uniformly eastward from MountDiablo beneath the Oligocene Kirker

formation to about 200 feet in the central part of the valley and main-

tains this approximate thickness eastward to the point where it is

truncated by the Valley Springs formatien near the eastern edge of the

Valley. Taf'f' (1935, p. 1092) referred the medial 700-foot shale member of the Markley in the M?unt Diablo area to the Kreyenbagen shale, with

"Whichit is undoubtedly correlative.

Apparently the Nortonville and Markley formations are of limited extent in the Sacramento Valley. As typicallY developed marine units they seem to be restricted to only the southern end of the Sacramento

Valley. Possibly they were at one time continuous with the

Kreyenbsgen shale of the San Joaquin Valley, but they are now separated from it by subsequent erosion across the stockton arch. Possibly they contain correlatives of the Wheatlandformation or of the volcanic rocks 26

overlyi.Dg the lone farther north in the Sacrame:o.to Valley.

In. the San Joaquin Valley the youn.gerEocene rocks represent a fairly

complete cycle of basin deposition. Initial invasion of the sea follow1Dg

(or producing) the pre-lJomeng:lneunconfomty was accom:pan1edby the

deposition of the conglomeratic sandstone of the nomeng:lnefonnation. At

the same time or earlier, the Uvas conglamerate memberof the Tejon for-

mation was deposited south of the Bakersfield arch (fig. 3, column 16).

The relation. between the Damengineand the lower part of the Tejon is

uncertain. If at one t:lme part of a continl..wusUIli.t, their connection

would seem to have been aloog the western side of the valley in the area

of thickest sedimentation. Ho'.rever,present evidence suggests that the

fumengine was restricted to the area north of the Bakersfield arch and

that the older part of the Tejon was restricted to the extreme sctrthezn

end of the valley. Subsequent Ehcene deposition covered the Bakersfield

arch, and the earliest deposits across the arch (the Point of Rocks

sandstone) ba've'been interpreted as at'. ancient and thick regolith re-

worked by the ma...>"inet!'SJ1Sgression(Hoots, Bear, and IO.einpe11, 1954a,

p. 119). The Damenginesandstone is a tan, medium- to coarse-grained,

poorly sorted, arkosic sandstone. It usua1.lY contains thin gray clay-

.stone and siltstone beds and,characteristically has beds of dark chert

pebbles in its lower part. It is quite variable in thickness but is

about 200 feet thick in most areas. It is thickest in the Mount Diablo

area, where 1,000 feet of strata are assigned to the fonnation, and

thins irregularly southward and southeastward. In the Coalinga area it

bas t.binned to a 5-foot bed of siltstone with large angular chert pebbles

(called the "grit zone"), but southward it thickens to about 1,000 feet 27

in the Kettleman Hi11 5 area, where it is called the Avenal sandstone

(figo 3, collIlll!l10)0 Fifteen miles farther south, in the Devils Den area,

it consists of about 300 feet of tan, coarse-grained sandstone with black

chert pebbles. This variation in thickness mayrepresent the irregularity

of the erosiona.l su..-f'aceupon which the Ibmengine. and the correlative

units, were depositedo The formation is present in IlD1chofthe central

and eastern parts of the valley north of the Bakersfield arch.

South of the Bakersfield arch the Uvas conglomerate memberof the

Tejon formation is composedlarge],y of granite debris derived tram the

nearby Tehachapi and san EmigdioMountainso It is of local extent and

about 100 feet thick. The Uvas contains a marine fauna that was either

contemporaneous with the fauna of the Ibmengine (Marks, 1941) or somewhat

older (Mallory, 1959). Conformably overlying the Ibmenginesandstone in IlD1chof the

San Joaquin Valley ,is a thick, conspicuous, and ..'idespread sequence of brown to white gypsiferous and diatomaceous shale called the Kreyenbagen

shale. The Kreyenbagenis one of the most lithologicaJ.J.y cOl2Sistent units in the Tertiary section of the San Joaquin Valley. In general the lower two-thirds of the section is a brown siltstone and claystone inter- bedded with samemedium-to coarse-grained sandstone which is increasingly abundant toward the base. In most areas the sandstone units contain grains of black and white chert and are widely referred to as "salt-and- pepper sandstone." The upper third of the formation is a near-white, highly diatomaceous and gypsiterous shale and diatomite. Outcrops along the western side of the valley range tran 600 to 1,000 feet in thickness from the Kett1e1DWlHillsnorthward, and rapidly increase in thickness to more than 4,000 feet southward with the development of the thick Point of 28

Rocks saudstone iD. the lower sand;r pa.."';; of the IQ:-eyenb.agen.This extreme thickness is recorded ill. the Devils ~ azea (Van CO"'..1Vex1.IlgandAllen,

194-3). Farther south, in the McKitt..-ick &"ea, and eastwrd across the valley the average thick!:i\ess of the Kreyenb.agenand Poi!lt ot: Rocks for- mations is about 1,000 feet. Towa;rdthe eastern edge of the valley these formations intertongue with, and aze replaced by, u.n.d.i:fferentiated continental beds usuaJ.].y called the Walker fozmation (fig. 3, column 15).

In the Bakersfield area, the Kreyenbagenand Point of Rooks grade laterally into interbedded marine and continental beds called the Famoso sand. It, in t-am, grades eastwaxd mto tJ.w contil:lentaJ. Walker formation.

The Kre",)'"enbagenandits equivalents e.-nend across the Bakersfield arch into the southern basin of the San Joaquin Valley and are continuOUS with the Tejcm.fomation. However, the Tejon is lithologically unlike the Kreyenbagen. It consists of mediUlna to coarse-grained sandstone

(upper one-third) and firmly cemented gray siltstone with thin sandstone beds (lower two-t!l1rds). The Tejon is about 3,500 teet thick and bas been subdivided into four members(Marks, 1943) (fig. 3, column 16).

To the north of Pacheco Pass the Kreyenbagen becomes sandier and is correlative with the Nortonville and Markley formations of the Mount

Diablo area. Taff (1935, p. 1092) separated the Sidney shale member from the Markley fo:nnation in the !-bunt Diablo ar-ea and called it Kreyenbagen.

The overly:i.ng "upper Markley sand" he apparently included in the basal beds of his "undifferentiated Miocene." In some areas the upper part of the Kreyenbagen is of Oligocene age, and in a few areas (fig. 3. column 12) the overlyiDg and lithologically similar Tumey shale of Oligocene age 1s not differentiated from the

Kreyenbagen. 29

Oligocene rocks. --Rocks of Oligocene age are not well represented in

the Central Valley. In someareas they were eroded prior to Miocene

deposition; some maybe included with upper Eocene or lower Miocene strata

because of uncertain faunal correlations with the type Oligocene of EUrope.

Oligocene rocks are represented in the Sacramento Valley by the

Kirker formation and possibly by the Wheatland formation, which is com-

posed of andesitic debris (Clark and Anderson, 1938, p. 945) (fig. 7 and

fig. 3, columns 4, 5, and 6). The Kirker formation was described by

Clark (1918, p. 86-99) in the area north of M:luntDiablo as consisting of

about 400 feet of sandstone, tuffaceous sandstone, and tuff. It rests

uncomformably on underlying rocks, and the unconformity represents con-

siderable erosion in someareas. For example, the ''Markley gorge" north

of M:lunt Diablo in the Sacramento Valley (fig. 7) is cut in rocks rang:!ng

from the upper Eocene Markley formation to.the Cretaceous and is filled

with Oligocene sed:lments (AJJDagren and Sch1aX, 1957) correlative with the

Kirker formation. The Kirker has been recognized as far southeast as the central part

of the northern San Joaquin Valley (Forrest, 1943, pl. III) and may be

continuous with the Tumey shale farther south. It may be correlative,

at least in part, with the Wheatland forma.tion known locally in the

southeastern part of the SacramentoValley and to the San Ramonformation

in the Berkeley Hills. Little is known about the distribution of the

Kirker, and most subsurface informa.tion in the southern Sacramento and

northern San Joaquin Valleys is inadequate to separate possible K1rker

correlatives from continental sandstone of younger epochs.

Oligocene rocks of the san Joaquin Valley include the Tumey shale,

San Enigdio formation, parts of the n()]]llllU"1neWalkerformation, and in O' EXPLANATION ...... ".."""...... " .. o EITIJ',',',':: . MARINE CONTINENTAL DEPOSITS DEPOSITS HEAVY LINE SHOWI P~U!NT LIMITS 0' SEDIMENTARY ROCKS IN THE CEHT'UL VALLEY

'CAL! IN lULU 010 !O &0 • o

N

n·

3'_ -0 .,.. SAN FRANCISCO

o

o •••

•••

SOURCES NORTH OF STOCKTON-- Several sources. SOUTH OFSTOCKTON-- . H?ots, Bear, and Kleinpell,1954a, with considerable revision

SAIl". BARBAfIIA 1200-.--0

FIGURE 7. Distribution and thickness of Oligocene sediments at the beginn1ng of Mi"ocenetime in Centrol Volley of California, same areas the ~er part of the KreiYenbagenshale. These units seemto be represented in most of the San Joaquin Valley. They have been eroded from the stockton arch and other local. areas. The Tume'Y shale is treated either as a separate formation or as an

Oligocene part of the Kreyenbagen shale. It is present in most areas along the western and central parts of the San Joaquin Valley from near the

Panache Bills southward. In part of its 0utcrop area, the Tumey has a basal sandstone as llIllChas 800 feet thick and au overly"'...ngshaleunit as muchas 700 felet thick. Wherethe basal sandstoMJis present, the TumeY is generally separated f'rom the Kreyenhagen,par.,ly because of its

Oligocene age. The basal sandstone is present in the subsurface of the

southwestern part of the valley and has been called the Oceanic sand

(fig. 3, column 13). The basal TumeY sandstone along the west side of the valley north

of Coalinga is well cemented, dark brown, medium "t9 fine grained, and

somewhatconglmeratic. Southwrd the Oceanic sand is less conglomeratic,

more friable, and al tho"llgb. medium grai1.V'd,:I.t containS a higher percentage

of silt. It 1fAY be correlative with the upper part of the Famososand in

the southeastern part of the valley (fig. 3, column15)·

The Oligocene shale units, whether called Tumey or Kreyenhagen,

intertongue with the variegated shale and sandstone of the Walker for-

mation along the eastern margin of the valley, and toward the southern

end of the valley the marine beds intert;ongUewith the thick sandstone

and siltstone of the San Emigdiofozmation, which UJ:Y be nc:mmarinein

part. Elctensive Jll)llIII81'1nesand;runits of Oligocene age (S:1JDIIIlerand

Sespe formations) west of the San Andreasfault apparently represent

continental facies s:lm:l'a:r to the WalJterand parts of the san SDigdio (lower part of the Tecu;yaformation) but are more closely related to the marine Oligocene of the southwestern part of the valley.

In the area f:rom the Kettleman Hills north to Mendota, a sbale unit is often distinguished from the upper part of the Tumey (or Kreyenhagen) shale and is called the "Lelia- zone." The contact of the "Lelia zone" with the underlyiIlg Oligocene has been described as an erosional surface by some workers; however, the unit is considered as a part of a continu- ous sequence of Oligocene sbale by others. The recogni tioD. of the "Lelia- zone" as a distinct unit seems to be largely due to the contained fossils, for which it is named. In IIIOstareas of the Central Valley an erosional unconformity separates the Oligocene rocks 1'roIIl the overlying Miocenerocks. In the

southern part of the San Joaquin Valley the unconformity is apparently represented by a period of erosion. Northward 1'roIIl the region of the

Panoche Hills, however, the unconformity is marked by increased a.nguJ.a.rity, indicated by truncation of beds along the western, and particularly along the eastern, margins of the valley. Greater defor-

!Dation is indicated farther BOrth, in the area of the Stockton arch, where the pre-Miocene beds are truncated across the entire width of the vaJ.ley. Miocene rocks.--The Miocenedeposits of the central Valley show

extreme lithofacies variation. AlthoUghlithologic variation is

characteristic of Tertiary sediments in this area, the Miocene rocks far

/' exceed older and younger depOsits in interfacies comple.xity and the

stratigraphic nomenclature is extremely complex. In general the depOsits of Mioceneage include continental con-

glomeratic sandstone around the margin of the depOsitional basin, marine II-I!!!!!

33

conglomeratic sandstone of near-shore envirOnmentin intermediate areas,

and marine "deep-water" sbale and sandstone in the central part of the

deposi tionaJ. basin. Continental beds are considerably more prominent in

Miocene deposits than in rocks of earlier age.

Miocene rocks are characterized by an increase in granitic detritus

from the Sierra Nevada to the east and by the introduction of ]'rancisean

debris from the rising Diablo uplift to the northwest. Granitic source

areas to the west of the san Andreas faUlt also becameprominent at the

beginning of Miocene time. Earliest Miocene deposition was broadly similar to Oligocene

d.eposition. However, the early Miocene seas inundated the area west of

the San Andreas faUlt and adjacent to the southwestern part of the

San Joaquin Valley where Oligocene continental dePosition bad taken

place (fig. 8). 'l'brOUghoutMiocenetime the seas extended westward from

the San Joaquin Valley across the present trace of tle San Andreas faUlt.

This extension of the dePositional basin contrasts with earlier paleQoo

geography, as does the progressive northward extension of deposition up

the San Joaquin Valley and across the Stockton arch into the southern

Sacramento Valley by late Mioceneand Pliocene time. ThrOUghout

Miocene time the basin margins were changing because of essentially

continuous tectonic activity in adjacent highlands. Continental deposits of early and middle Miocene age were deposited

aleng the southern end of san Joaquin Valley at the foot of the

San l2Digdio and Tehachapi MountainS, along the eastern side of the

valley, and across its northern part freIIl the Sierra Nevada to the

Diablo uplift at least as far north as Sacramento. These continental

beds are referred to the Tecuya f01'lll8tionin the southern end of the ~--~------_. EXPLANATION

CONTINENTAL (j') MARINE DEPOSITS DEPOSITS

HEAVY LWE SHOWS PRESENT LIMITS OF SEOIMENTARY ROCKS IN THE CENTRAL VAllEY

SCALE IN MILES 010 30 so •

N

SAH FRANCISCO - - o

o ,.,

SOURCES

NORTH OF FRESNO-- (m Several sources SOUTH OF FRESNO-- Hoots, Bear, and Kleinpell, 19540, with some modifi- SANTA eARBA'" cation. '---~ 120°.---J:J

FIGURE 8. Distribution and thickness of lower Miocene sediments at the beginning of middle Miocene time in Central Volley of California. 35

vaJJ.ey and 1nf'omaJ.ly to the Zilch zone or formation along the eastern side

and in the northern part of the valley.

The recognition of subdivisiQIlS within the continental beds is

difficult and in some areas iII!POssiblefrom subsurface data. In much of

the southern and eastern areas of the SaD. Joaquin Valley the Tecu;yaand

Zilch are inseparable frQm the Pliocene CbarJacformation. In the northern

part of the valley the Zilch merges with the Valley Springs formation of

middJ.e Miocene and possibly older age. Probably the greatest thickness of

these lower to middle Miocene continental beds is present at the southern

end Qf the basin, where as muchas 4,000 feet of the Tecuya formation

accumuJ..ated Rear the foot of the Tehachapi and San Fmigdio Mountains.

Along the eastern side of the valley the Zilch bas a maximumthickness of

about 2,000 feet, but where inseparable from the overlyiDg beds, the

entire continental sequence of Miocene, pliocene, and probably

Pleistocene age is as much as 4,000 feet thick. South of Fresno the

Zilch is about 2,200 feet thick but th1ns northward beneath younger

Miocene units to about 400 feet south of .lerced. Near here the younger

Miocene Wine units pinch aut, and to the north the Zilch is inseparable

from Pliocene and probably Pleistocene continental beds; the cQlllbined

continental sectdcn is aboUt 3,000 feet thick in the Merced area.

Locally thin continental units, 1nfo:rmallYassigned to the Zilch, are present along the west side of the valley, as in the PaDocheHills

(R. G. Schenck, oral C'ODD!Dtnication,1959),but for the most part continental Miocene deposits are not well deVelopedalong the :f'la.nks of the Diablo uplif"t. Although continental beds of Miocene age

(Caliente formation) are now present west of the southern end of the valley, these beds seem to bave been derived f'roIIl the san Fmigdio and Tehachapi Mountains and have since been displaced along the San Andreas fault from some area to the south or southwest of the San Pmigdio

Mouatains • The gross lithology of these continental beds is ejrnilar in all areas. They are tan to red coarse-grained sandstone and conglomerate.

Red and green shale beds are iJl.terbedded with the sandstoJ:le in lIIIl,.IIy areas, particularly those closest to marine intercalations. The continental units are coarsest, often a boulder conglomerate, near the source areal! and are thickest in areas closest to the mariJI.edeposits. The principal source areas were lIIOstly graJlitic, with increasing amounts of volcanic and, to the west, Franciscan debris present iJI.the younger Miocene and

Pliocene rocks. Toward the celltral parts of the basin the col1tinel1tal sandstone units intertongue with, and are replaced by, near-shore marine sandstone and shale units. These near-shore sandstone and shale units are frequently assigned to the Vaqueros (lower Miocene) or Temblor (miQ.dle

Miocene) formatioJlS. This assignment is based mainly 011 faunal differences rather than lithologic variation. Since interpretations of the faunas differ, rocks called Vaqueros by SOllIepeeple may be called

Temblor by others. For example, Vaqueros has been used locally in the

subsurface of the Coalinga-Kettleman Hills area and farther south

(fig. 3, column 11); the II8IlleTembloris more generally used, however,

far the same rocks throughout muchof the san Joaquin Valley. The marg:!na1marine or near-shore marine sandstone units of Miocene

age in the san Joaquin Valley are mostly weakly cemented, mediumto

coarse graiJled, and somewhatconglomeratic. For the most part they are

relatiVely cleaD., but toward the central part of the basin III&JIY became 37 increasiDgly argillaceous. The increase in argillaceous material forms

"permeability barriers," and in someareas these lithologic variations have resulted in the acc11lDn1atiol1ofoil. The best know. example of such a "permeability-barrier" oil trap is in the upper Miocene steveIlS sand southwest of Fresno (Hoots, Bear, and IG.einpell, 1954b).

In someplaces these marginal marine sandstone beds occur as more or less isolated bodies surrounded on all sides by less permeable rocks.

Typically they coalesce toward the basin margins with the more extensive continental sandstone units, and intertongue toward the center of the basin with marine shale. They are locally as IIIllchas 2,000 feet thick, particular~ the lower Miocene Vedder sand and the upper Miocene Stevens sand in the thick Miocene section south of the Bakersfield arch, but more typically they are between 500 and 1,000 feet thick. The better known aands'toae units included in this group are called "Vaqueros,"

"Temblor," Stevens, Vedder, Phacoides, Rio Bravo, Olcese, and CarReros

( figs. 3 and 9). someof these namesare derived from the nameot an oil field or from a characteristic fossil or faUDa. Probably someare synol1CllllOUS • The marg:!na1marine sandstone units are interbedded with shale units which range from 100 to 1,000 feet in thickness and which, in the central part of t.he southern san Joaquin Valley, aggregate as muchas five-sixths of the total Miocene section. Locally the total Miocene thickness exceeds 12,000 feet and is more than 6,000 feet throughout the southwestern 8aJl Joaquin Valley. These shale waits have maDY names, ucluding Reef Ridge, McDoD&1d,Antelope,RoundMountain, Freeman,

Jewett, Fruitvale, Vedder, Devilwater, Gould, Salt Creek, Saatos, aad

Media (figs. 3 and 9). They are all brollllish IIIlldstone, baviDg all EXPLANATION o MARINE CONTINENTAL VI DEPOSITS DEPOSITS 40' HEAVY LINE SHOWS PRESENT LIMITS Of' SEDIMENTARY ROCKS IN THE CENTRAL VAlL!Y

SCALE IN MILES o- 10 30 ~O

N

58'

SAN FRANCISCO I - - o

o .1'

SOURCES , NORTH OF MERCED-- Several sources SOUTH OF MERCED-- ~~to:s, Bear, and Kleinpell,1954a, I some modification. SANTA BARB."A ----120°...... ,-0

Distribution and thickness of middle Miocene sedimentsat the beginning FIGURE .9. of late Miocene time in central Volley of California. 39 appreciable percentage of silt and variable quaatities of fine sand. Some are siliceous. For the most part, thick sections of claystone are absent.

These thick shale units bave somet:lJneSbeen considered membersof the

Monterey formation that is typically developed in the Coast Ranges west of the Central Valley. The Santa Margarita saadstone of latest Miocene age is probably the most extensive and uniform margi.Dal marine sandstone unit in the

San Joaquin Valley. This unit was deposited at the time of the most extensive marine iJlvasion and is correlative with the San Pablo group that was deposited during a mariBe re.iBvasion of the southern Sacramento

Valley (fig. 10). contemporaneous continental deposits, referred to the

Valley Springs and Mehrten formations, were deposited across the

Stockton arch at this time and perhaps some distaace northward up the

Sacramento Valley as the basal part of the Tehama. formation.

The Santa Margarita is light-gray friable sandstone composed of poorly sorted, subangUlar, fine- to coarse-grained quartz, feldspar,

and granitic fragments. conglameratic beds and maIIY interbeds of sandy

mudstone are common. It is quite variable in thicDess and locally is

as much as 2,000 feet thick; however, in most areas it is less than

1,000 feet thick. TOwardthe basin margins the Santa Margarita inter-

tongues with continental sandstone units knOwn as Bena gravel to the

south and Zilch tEl the north. It is d11'ficult to distiDgUish between

these marine and ceatinental units iB subsurface sections. Toward the

central parts of the basin the santa Margal'ita intert;oJlgUes with, aad

is replaced by, the McLure, Reef Ridge, aad Antelope abales. The

Stevena sand is a partieuJ,.arly exteasive basinward to~e of the lower

e part of the Saata Margarita .... dston • 40

EXPLANATION ...... o E2JZ]...... '....:..:::.'.','.'. MARINE CONTINENTAL DEPOSITS DEPOSITS

HEAVY UNE SHOWS PRESENT LIMITS OF SEDIMENTARY ROCKS IN THE CENTRAL vALLEY

SCALE IN MILES 0103050 o -

N

30'

- - o

o so'

SOURCES NORTH OF MERCED-- Severo I sources SOUTH OF MERCED-- Hoots, B ear, and Kleinpell,1959a.

FIGURE 10. Distribution and thickness of upper Miocene sediments ot the beginning of Pliocene time in Central Volley of California. 41

The Sa.ll.ta Margarita $BJ!,dsooaeis present 1!1. the subsurface throughout

most of the San Joaquin Va.lley except in the southvest~ part between

Coalinga. and the San Emigdio M:!U11tains. In this area it has been replaced

by the Reef Ridge, McLure, and Antelope shales. Although w:l.~ dis-

tributed in the substl.!'f'ace, it does not crop out in 11JB.DY areas. It is

absent aJ..cmg the west side af the valley except between Coalinga and

Tumey GuJ.ch south of' the Panache Hills. To the north it is truncated by

Pliocene units and to the south it is replaced by shale UIlits. Coarse

coD8lomerate J.enses in the McLu!'e and its equivale.1l.ts farther south at

Reef' Ridge aad in the Temblor Ra!:lge may be santa Margarita tongues

extending far into otherwise dissjmjlar lithology.

The Santa Margarita is not represented in outcrops along IIIOstof

the east side of the San Jeaquin Valley because of eastward gradation,

ill the SUbsurface, into the more marginal and largely continental Zilch

fO:rnJatioD.. In the central part of the valley the Santa Margarita sand-

stone is present as far north as Merced. Hel'e it is replaced by

Ulldif'f'ere!l.tiated Mioc~e and Plioceme continental sed,imeats.

The MehrteB formation and the UIlderJ..y1DgValley Spr1Dg~formatiOJl

(equals Zilch farther south) were depOsited across the Stockton arch

and intertcmgue w:i.th marine formations of the San Pablo group at the

southern. end of' the Sacrameato Valley (fig. 3, colUlllJlS4, 5, and 6).

They are t;ypicaJ.. continstal conglomerate, sandstone, and shale units

and are reg:! ODally distiDgUished by 11thologic differences. The

vauey Springs contains a high proportion of fregmeatal rby011te and

i s deVOid of the :fresh aades1te f'r'arntl fOWldabuadantlY in the

Mebrten. Where present, the rbyollte &Ad andesite debris seem to be tioll d1&gQ.ostic. The Miocene part of the J(ebrteI1 forma east of stockton (near colc:mlbia) lacks volcanic rocks and overlies the g!'alli tic basement of

the Sierra. Nevada. In such areas fossils seem to be the only means of

separating the tw formations.

The Mehrten formation is aB muchas 500 feet thick 011 the eastern

side of the southern. SacramentoValley and the Valley Springs formatioll

is about 450 feet thick. Here the overlying upper Pliocene and Pleistocene

units (laguDa. formation) are as much as 1,000 feet thick. ID. the sub-

surface of the central part of the valley from the stockton area southward,

the combined and undifferentiated Valley Springs, Mehrten, and younger

formations are uniformly between 3,250 and 3,500 feet thick.

The Valley SpriDgs formation seems to be correlative, and perhaps

centdnnous , with rhyolitic tuffs of approx:!JDate1YMioceneage overlying

. the Wheatland and lone formations of the eastern and central Sacramento

Valley as far north as Marysville Buttes. The Mehrten seems correlative with the younger a.lI.desitic tuff of the samearea. To the west the

Valley Springs formation is replaced by the Cierbo sandstone in the

Rio Vista gas field (fig. 3, celUlllll5), and in the outcrop section north of MoUlltDiablo the Mehrtel1formatioD.is replaced by the Neroly formation.

The Cierbo sandstone and the Neroly formatioD.of the San Pablo group are the o:oJ.ymarine Miocenerocks recorded in the central Valley north of the Stockton arch (fig. 10). AlthoUghquite widespread farther west in the Coast Ranges, their extent in the southern Sacramento Valley is essentially coRfined to the area west of the Rio Vista gas field. The formations are cOlDPosedlargely of marine sandstone and conglomerate with minor amounts of shale. MarlY units are tuffaceous, and south of Mount

Diablo the Neroly contains andesitic debris suggestive of the Mehrten formation to the east. Muchof the sandstone of the Neroly formation is 43

colored a distinctive blue because of a "dull opaline coating on the grains"

(Huey, 1948, p, 43). The Cierbo and Neroly vary considerably in thickness.

Clark (1915, p. 406) reports about 600 feet on the north side of Mount

Diablo and about 2,600 feet to the south of the mountain. Of this greater thickness Huey assigns about 500 feet of the lower part to the Cierbo formation and the rema:lnder to the Neroly formation.

West of Mount Diablo and il'l the Berkeley H:I.1lsthe marine rocks grade into thick continental beds (fig. 3, ColUlllllS6 and 7). This area lies within the structural belt of the Coast RaDges, and thickness, facies, and distribution of deposits are quite variable.

Pliocene rocks •• ~Tectonic activity in the Central Valley at the beg:lnn:lng of Pliocene time resulted in erosion in Diany areas, particularly aloli1g the western edge of the SaIl. Joaquin Valley. The erosional uncon- fOrmity upon wh:I.chPliocene rocks were depesited is regionally allDost as s·~ • ficant as the pre_Domeng:lneunconformity and the unconformity above the l-t>reno shale. E;:onomical1Yit is more significant, for IDllJlY of the

011 fields on the west side of the San Joaquin Valley either produce froIIl traps caused by the early Pliocene warping or 1'rOIII truncated. reservoir beds sealed by later Pliocene deposition. Considerable modification of the overall shape ot the depositional basin also took place during this erogeJ:IY. The central Valley assumed its P~sent form; and Pliocene deposits, largely continental, are fOlmd in all parts af the valley. Regional elevatioa of the valley progressed t~t Pliocene time and lII&I'il1edeposition was restricted to the western ha11' of the southern Saa Joaqu:iAValley (fig. 11).

The marine lower and middle PlioCelle rocks of, the San Joaqu1Jl tiOJl Valley are described variously &8 the Etchego:1:afDrma ,the Etchegoia 1200 I·-CJE'PLANAT"r;;;a-

MARINE CONTINENTAL U'>- DEPOSITS DEPOSITS

HEAVY LItlE SHOWS PRESENT LIMITS OF SEDIMENTARY ROCKS IN THE CENTRAL VALLEY

SCALE IN MILES 01030- '0

N

SAN FRANCISCO - - o

o ••• '..

SOURCES NORTH OF Many FRESNO-- SOU Sources HootsTH OF B F RESNO-- With's ear,and Kleinpell 19540 Orne m odif1 icution. " ' SANTA BARBARA

---- 1200..---0

FIGURE II Distribution and thickness of Pliocene sediments ot the beginning of Pleistocene time in Central Volley of california and Jacalitos formations undiff'erentiatedo or as the two formations

differentiated. In the defilrltion of the Jacalitos formation (ArnOld and

Anderson, 1910.l' :po 96), it was pointed out that the unit could DOtbe separated from the overJ.yi.Dg Etchegoin formation on the basis of litho<-

lOgic or topographic indi vidllali ty, but aBly on the basis of its contained

fossils.

The Etchegoin formation, used in the bread sense to wclude the beds

Containing the lower Pliocene Jacalltos fauna as well as the middle

Pliocene Etchegoin fauna, is composed of sandstone .• conglanerate, and

shale. The sandstone contains a high percentage at volcanic detritus and

is brown, locally bluish, conglomeratic, generallY quite silty, and is

qUite variable in grain size and sorting. The sbale varies 1'rOIII a dark- attaiDS green C~stone to gray or brown pebbly mudstol!.e. The Etchegow a tb.1c:kneas (;)1' a1lcut 2,000 feet in the Coalinga area and thickeJlS east-

"Alrd 1;0 as much as 3,500 feet in the central part of the valley· lSSt of

the central part of the valley it rapidly intertongues with, and is replaced by, continental beds asdgned ..-eG the ClJa,naCaad overJ.y1JJgKeI'I1

R1ver formations. In the central part of the basin the Etchegoill is J1e preSent d t.rolII coa ga sOUthward acrass the Bakersfield arch; JlDrthw&r it is mo t vall and is reported 8 extensive aloag the western side of the ey llear4r cated by over- as far north as the paneche Hills. Here it is trun ~ Pli-"'-' _a..-l: of the Ocene and PJ.eistoceDe units, bUt ill the C~ ..... ~· eat .vau.ey it grades northward into COllt1Jle:atal beds equival to the upper

Part or the Mehrte:a. formation sad to the LagU1I& fo~tioa.

The most exte:a.sive marine unit of the Et;ehegoiS t.-tioa is the ~ z ...,... reaeat is it. _ Olle or lIhal.e, aamed tram the :ressID .blada&...." p

It extea"- -'A" ;u is the .....well. eaa-tward of the ma1A bediY of the ",...-ego Bakersfield area (fig. 3p col1.DDD.15)and is used there to separate the lower Plioce:ae C:b.a.nacformation from the overlying KernRiver formation.

Where the Macomashale is absent it is impossible to separate the CbaDac from the Kern. River formation, and one or the other IlAIlle is applied to the entire sequence, which ranges from 1,000 to 2,500 feet in thickness.

Overlying the Etchegoin formation, and also gradiDg into the Kern

River formation in the southeastern part of the San Joaquin Villey, is as much as 2,000 feet of mudstone, sandstone, and mudd;vconglomerate called the San Joaquin formation of latest Pliocene age. In the

Coalinga and adjacent areas the SaI1 Joaquin formation is partly of marine origin and cCllnsists mainly of claystone, siltstone, and silty sandstone.

This fine-grained lithology persists ill. the westerJland central parts of the valley as far south as the Bakersfield arch and nearly as far north as the recognizable Etchegoin. Beyondthese limits the San Joaquin grades into continental sand and gravel •.cbaDacto the south, KernRiver to the east, Laguna to the north. NorthwardaJ..ong the west side it is e1ther replaced by the Tulare(?) formation of Pleistocene age or is absent in the outcrop, The base of the Tulare formation is customarilYplaced at the toP

01' the highest marine bed. In areas marginaJ.to the main Pliocene marine baSin, this boundary nay be variable, and part of the TuJ,.are "/JJ8.Y be eqUivaJ.ent to part of the San Joaquin formation. In someareas the

Tulare contains Pliocene fossil mammals. In the area. of the stockton arch the Pliocene rocks include parts

01' the upper Miocene to middle Pliocene )IehrteD. formation and the middle

Pl10 i TheLagUDa is ceae to probably Pleistocene Lag1.UIBo format es- larg~ an 1UI.consolidated fluvial depOsit coasist1Dg of silt, c1JI.Y, 47

medium.. to coarse-grained sand, and lenticular gravel. In the type area

northeast of' stock:tcm (Piper aad others, 1939, p, 57), it does not exceed

500 feet in thiclOless. To the west in the IDOrecentral part of the

valley, it has not been differentiated fran the under1yillg Mehrten for-

mation or the overlying 1'iJle-grained Pleistocene tmits. In the stockton

arch area the upper Miocene Pliocene, and Pleistocene continental section

is at least 3,000 feet thick.

In the western part of the southern sacramento Valley, north of

Jblm.t Diablo, outcrops C!Jf continental beds apparently continUOUSwith the

Lagwaa, formation to the east range from middle to late Pliocene in age.

These beds are locally as much as 1,000 feet thick and have been called

the Wolfskill formation. They overlie a middle to lower Pliocene tuff

Ul'lit ca.1J.ed the Pinole tuff ar, lacally, the Lawlor tuff. In this area

the tuff overlies the upper Miocene Neroly fonoatiOI1 or older rocks and thiCkens west-ward to about 1,000 feet near san Pablo Bay.

Fifteen miles north of the type section of the Wolfskill fonoa- t1oa, at the northern edge of SalaDO COUllty", a sjmi1ar section has been lDa.:ppedas the Tehama formaticm. Here, as in IDOstother areas, the

1akj Tehama overlies a w.ldespread tuff bed called the Nam tuff. Al1;hoUgh the Piaol ( tc 7 miles south of e Lawlor) tuff pinches out aloDg tbe ou rop the +--_ ted f'l'GII outcrops of -07 J:I<= sectiOD of the WoJ.f'ski n and is thus separa the N, th two tuff beds am ak1 tuff at Capay by a distance of 22 miles, e

IDa.y be COrrelative. BQwever, AladerSP &I1dRuSsell (1939, p. 250) feel that the e of differesce• tuff at Capay is not the Nap" aki tuff, becaUB

~ cCllDpositiOJl. !be the flaC1'IIIIIdto Vallet Teba!l!ll foxmatioa is pre.eat ~t &ad 18 ed ef JJ,gI1t-~d as JlIU.ch as 2,000 reet thick. It is ~I 48

silty and san~ fluvial deposits with sane gravel that becCllllesoore

abundant toward the source areas. ~e cam,positionof' the Tehama varies

greatly with dH'ferent source areas. On the eastern side of the valley it

is usuaJ.ly called the Tuscan formation and is cOIIIJ?Osedlargelyof volcanic

debris derived from the Sierra. Nevada to the east and lokldocPlateau area

to the northeast. It is underlain by the Nomlakituff :1Jl the I10rthem

Part of the valley. To the south aloDg the eastern edge of the Sacrameato

VaJ.J.ey and away f'r.:ll1J1 the volcanic source, the Tuscan presumablyillter-

tongues with rocks lithologically similar to the contemporaneousLaguDa

~~. ch 1;1011, although the name Tehamaformation is customarilYused fer su lithology except in the extreme southern end of the SacramentoValley.

Pleistocene rocks. --Rocks of Pleistocene age are present throUgiloUt the

CentraJ..Valley of California. They are all of continelltal orig:ill ud,

~cept loc~ a10Dg the margins of the valley, they are not differentiated from the underlying upper Pliocene formations. Twa units are recognized at ~ el recogniZed - ~site ends of the Central Valley. The RedBluff' grav , in the D.orthern part of the Sac~to Valley, is a coarse flUvial for-

IllatiOJl,of bright_red color that 1s less than 100 feet thick iJI. most areas. Th rn.., th them ba1f of' the e "'u.L

the Ceatral Valley. Recent a.lluvium covers much of the lowland areas of

the present-day valley.

STRUCTURE

The Central Valley of California is an elongated northwest-trending

structuraJ. basin or trough formed by the westward tilting of the Sierra

Nevadablock against the eastern flank of the coast Ranges. This has

resUlted in the relatively uniform slope of the basin floor westwardto

~de epest ;part, near and parallel to the eastern edge of the Coas t

!laDges(fig. 12, in pocket). Between the central axis of the basin and

its western margin, the beds filling the dePression are folded and

locally faulted.

In the central part of the basin, the stockton areb bisects the

Central Valley and structuraJ.ly unites the Diablo uplift of the Coast

IlaIlgesWith the Sierra Nevada. block. This areb had fonned by libcene

t_ and was active at least uatll the elld of Oligocene depOsition. A

81lD:Uar feature in the seutheI'2l part af the valley, the Bakersfield ~, Pro....- til middle libCeJle _b~ formed the southem end of the basa un t1JDe,Wh the area of deposi- en it was GVerlapped and for the first tillle tioa extended as far south as the present lim:!.ts of the valley· 1'10-_ ..... eae time covered -~IilitioD. across the Bakersfield arch ill late _c the &.rea be li)Digd1O )foUJltaiJl'. tween the arch ud the Tehpchapi and Baa "J.~ Valley d,epOlitioaal th:1s area baa beeJI a part of the Baa JoaquiJl ~~ tt-. d iAto sad !Id late EDceae t1me to the preseJlt, it deVelope ~t1Jaued rd"f,der of tJJe to be a structural basiJI. di.tUct trfJIJ tbe "U.~• ther tile ve,-rd- It COJlta:l:u ao part that 1. aP"ogoua te e1 50 tilted fl.oor of the Central Valley or to the folded and somewhatfaulted western side of the valley, but rather appears related to structural basins which formed in the Coast ~es to the west in. Oligocene ud particularly Miocenetime. These basinS west of the SaD. Andreas fault were offset northward by the fault by Pliocene time and were 110 lODger continuous with the basin south of the Bakersfield arch (figs. 6 to 11).

On figure 12 the basin south of the Bakersfield arch is shoWn as the "southern basin;" the westwrd-til ted basemeJ1tfloor of the Central

VeJ.ley basin is shoWll as the "Sierran slape;" aad the western folded belt parallel to the coast RaJlgesis shOWll as the "folded trench." The division between the Sierran-slope aIld the folded-trench structural elemen.ts bas been draWll at the axis of the major syJlclines which form the deepest part of the structural basin. This seemsto be the approxi- - mate boundary betwee1l relatively UDt'oldedstrata with a prevailing west- ward dip and folded strata with a geaeral eastward dip. Althougllmost of the Central Valley is covered by Receat alluvium that conceals the

structure iA lIIBJlY areas, this distinction betweeJ:lthe major structural

elements fits the kJIoWll iAformation.

The Sierran-slape and folded-trench elemeats JlJB:3 be further sub-

divided at the stocktOJl.arch all the baSis of samewha.tdiSSimilar

structural history; the Sierran slope aad folded trench of the

San J0&quiIl Valley are oore complexand varied than these structural

UJlli ts in the sacramento Valley. In the Central Valley four major periOds of tectonism are recorded:

the post.MoreDO,the pre_Dameng:lBe,thepre-Pliocene, and the mid-

PleistoceJ:le periOds of deforma.tioB.. Ik1ring these struc~ active

periods the major change."in the configuration of the depositional basiA 51 took place and the majo:t,>ityof fGlc'l.l3with:i.l! the sedimmts wez:ef01"Jlied. The mid-Pleistocene peri d is clMSidered by !II&'.Y to Davebeen the most severe, and during this time apparently all flexures iJl the c~tral Valley were either f'oJ:'lllt')dor accen:tuated fram older eDsth.g strac'tlll"es. Locally mid-

Pleistocene waJ:'lling produced. a structural relief as great as 5,000 feet.

Local. areas were structurally active at ther t:lmes 1;hNugb.oUtthe

Mesozoic and Cenozoic. The recency of majol': tectonic activity ill. the Central Valley is not

surprising ill view of historical seismic activit-,f. Figure 13. tak= from

Ri('hter (1959), is an estimate of probabl~ ma.x;Unuin seismic intensity to

be expected in the central Valley and other parts of Califor>'...1a. It is

based all the known geology in the area, tempered by historic records of

seismic activity. In view of the p:roporlionate briemefls at the histonc

record as c~d with the total ti1lle rep1'ese:ritt~dby t,h@ moder.nstructural le pattern, it IIlllStbe admitted that the sei&mlOlogicsaJIIP is quite small and

statistically uncertain. The evaluati

with depth as well as with area. The distribution of areas of probable

intensity on figure 13 iii largely based upOll surficial rock types. Uncon-

solidated sediments are markedly more sensitive to seismic disturbaJlce than

consolidated rocks. If considered f'rOIII the standpoint of conditi ns at a

depth of about one mile, ,mere consolidated rocks are more prevalent,

nearly all of' the area wouJ.dbe included in the VII maximUDl intensity

ScaJ.e, or less, except for the southern end of the San Jeaquin Valley.

This area, essentially the southern basin south of the Bakersfield arch,

is cam,posedlargely of poorly COllSolidatedPliocene and Pleistocene sedi-

ments at this depth. In addition the southern basin is partly encompassed 52

zn

JX:. Occasionally

• Historic earthquake• epicenters. !lI MM or greater

- -

o

Heavy boundary shows limit of Cretaceous and Cenozoic sedimentary rocks in Central Valley

SCALE

0b";Ili:;O~2~O~__~4CJ!b5iii~60MILES

FIGURE 13 Probable 53 and crossed by fault zones that are know!!. to be active. The southern basin, therefore, is est:lma.ted as having a probable maximum seismic im.tensity of VIII or occasionally IX even at a depth of one mile.

WASTE DISPOSAL POSSIBn.mES

The safe storage of liquid radioactive waste in subsurface reservoirs is a complicated subject. Although geology is unquestion- ably one of the most :ilIlportant considerations, alone it is not ade- quate basis for even suggesting favorable storage enV'irOJ]lDelLts.Ia the follewimg discussion more or less untested assumptions have bee». made in order to provide a foundation upon which the geologic evalu- ation may be constructed. Without these assumptions the geologic aJ1aJ.ysis has no purpose or direction. These assumptions are as follows: 1) Permeable formations may be used for waste storage. This

assumption is subject to many doubts and qualifications.

(See Roedder, 1959, for example.) ble 2 ) Artificial reservoirs may be created in im,permea rocks

by hydraulic fractur'iDg or deep unde~d explosion.

The use of such reservoirS for radioactive waste is un-

tested al thG'Jgb studies and tests on a s:ma.1J. scale are in

progress at Oak Ridge National Laboratories.

3) The qua:ati ty of' waste to be dimsed of' i8 not considered

great relative to the capacity of the geologic reservoirS

'mder consideratiOll. This assumption caa be 0B.1Y partly

true aud its evaluatiOll IllUStwait for more specific iDfor-

maticm regard1Dg quaatity of waste aad stud;r of specific storage reservoir capacity. Roedder (1959, p. 17) suggests

that within a CCllll,PU8otive1yfewyears, a daily output of 100,000

galJ.OllS of high-level waste for the entire United States is a

reasonable assumption. With quantities of waste as large as

this, reservoir capacity will need to be carefully deterJDi,ned

bef'are the investment in a disposal plant is made.

4) Saf'e storage is understood to mean positive coBfinement for

1,000 years but is werred to 1llClude slow migration, which,

because of the time inVOlved, loss of same radioactive CQlll-

ponents by becoming "fiXed" tb.".-ough rea,ctiOl1 with miJlera.ls with-

in the reservoir, and dilution and dispersiom. while migratiJIg,

has remained within safe limits. 5) Opt:lmumsteNe depth is one mile, which is well below the

current water-supply level in the Central Valley. storage

o~ below the depth of potable water is couidered. In

general this will mean at depths greater than 2,000 to

3,000 feet. 6 ) The selection of a particular area or spec:l,fic site for

waste di/3l'Osal c8JilllOtbe made withoUt very detailed geologiC

studjr. Because of the hazard inVOlved, the detail of the

geologic investigatiOl1 IIIllStbe far greater than most sub- ble surface studies so far made for 011. The couidera cost

aad time involved diacourages stuct" 1JI. raJldCll!lly ae1ected

areas au.d 1'a.vors a JoiSt reactor site-diapesal site atuct"

pregram. This report does no JDGre tball poat GUt that

possibilities for waste diapoaal de exist is the subsurface a roeka of the estral valley of Ca.lif'ora1 • content would be of considerable value because part of the radioactive components would be adsorbed by ion excllange. In the extreme southern end of the Sacramento Valley, in the area just north of the stockton arch, the ne sandstone UDits of the MeganoS formation, and partiCularly the DomenIP

sandstone, are of potential use in that they are permeable and are iSOlated

by marine shale units. Also of possible use are sandstone beds of the

Kirker formation, particularly where they fill the ''Markley gorge."

Pleistocene and Recent rocks in the sacramento valley are largely of

continental origin and are considered to be of little use for liquid-waste

storage. AJ.though composed of coarse and permeable sandstone, these con-

tinen.tal deposits are poorly consolidated and characterized by complex

lithologic variation. It is believed that the migration pattern of

liquid waste through such un! ts would be very difficult to predict and

would be uncontrollable for the most part. In the San Joaquin Valley sandstone units of Tertiary age with

potential storage capacity include the cantua sandstone memberof the

10<10formation, the YokUt sandstone and Gatchell sand, the Domengineand

Avenal sandstones, the Oceanic sand and other sandstone units within the

Kreyenbagen, and the rIJB1JY marIPnaJ. ma.r1ne sandstone units of the Miocene.

Sandstone tongues and beds in the Etchegoin (inCluding the JacaU tos)' and

Tulare formations may also be of use. As in the sacramento Valley, use

of continental beds in the san Joaquin Valley is generallY considered

impractical. because of the probabill ty of uncontrollable migratiOll. of

'Waste. However, discrete tongUes of continental beds within the JD8,1'1ne <,, - section would be usef'uJ.. The thick sandstone and couglomerate beds 111the southern bas1l1 at

the foot of the S&n Emigdio and Tebecbapi Mountain are of possible content would be of' considerable value because part of the radioactive components would be adsorbed by ion excbaDge. In the extreme southern end of the Sacramento Valley, in the area just north of the stockton arch, the

sandstone units of' the MeganOSformation, and partiCularly the J)oD!engine

sandstone, are of' potential use in that they are permeable and are isolated

by marine sbale units. .uso of possible use are sandstone beds of the

Kirker f'ormation, particularly where they fill the ''Markley gorge."

Pleistocene and Recent rocks in the sacramento valley are largely of

continental origin and are considered to be of little use for liquid-waste

Although composed of coarse and permeable sandstone, these ccn- storage. zed t1nental deposits are poorly consolidated and cha1'&cter1 by complex

lithologic variation. It is believed that the migration pattern of

liqUid waste through such units would be very difficult to predict and

Would be uncontrollable for the most part. In the San Joaquin Valley sandstone units of Tertia.r1 age with

POtential storage capacity include the cantua sandstone member of the

1odo formation, the YokUt sandstone and Gatchell sand, the J)aDengineand

AVenal sandstones, the Oceanic sand and other sandStone units with1l1 the Kreyenbagen, and the many marg:11lBol mar1Ile sandstone units of the Miocene.

Son"""" tongue. and beds .. tbe'-goiA (.- tbe ,.-toS) ... Tulare l' th sacramento Valley, use ormations '1JJAY also be of use. As 111 e idered

ot contin ental beds in the San Joaqu1l1Valley ill generalJ3 COl1S

:1m.Practi L_ a,ble m1gr&t101lof " cal because of' the pro'bab1l1t1 of UI1Conwv-- e waste t1l1en~_1 beds with1l1 the mar1I1 • However, tliscrete tongUes of con .... sect1 ' onTh wouJ..dbe usef'ul. the southe1'Xl ba8111 at '- e thick sandstoae and conglomerate beds 111 the l' ta1I1 are of pOssible ha oct of the san l!m1gtlio and Te1"c p1 J'?UJl

57 interest. These rocks il'lclude parts of the TeJon ., 57 San 12Digd.1o ., and interest.Tecuya These f'ormati,:,ns.rocks il'lclude This parts area. of theis, however,TeJon ., San quite 12Digd.1oactive ., andtectonically; Tecuyamost f'ormati,:,ns. major historic This area.earthquakes is, however, in the quite Central active tectonically;Valley have centered here. most majorThe southern historic earthquakesbasin, therefore, in the is Central not onsidered Valley have centeredfurther athere. th.ts time. The southernAr-t1f'1cial basin, reservoirs therefore, in is shale not units.--Artificial onsidered further at th.ts time.reservoirs in Ar-t1f'1cialshale reservoirsmight be created in shale 1n units.--Artificial a ftN units, but reservoirsin in general thick bodies of shale mightshale beare created not as widely1n a ftN available units, but as in are general sandstone thick bodies reservoirs.of Many of shale areth enot predom:1.nantly as widely available shale as uni are ts sandstoneare 1nterbedded reservoirs.w1 th Many thin bedaof of sandstone th e predom:1.nantlywhich are believed shale to uni be ts permeable. are 1nterbedded Those w1units th thin bedathat of seem sandstone to which haveare believed low enough to be permeability permeable. Those and thickness units that for seem touse w1 th artificially have lowcreated enough reservoirs permeability are the and Capay thickness shale forin the use southe w1 th artificiallyrn Sacramento ValJ.ey createdand reservoirs arm.th of'are Chico the Capay where shale it fills in the deepsouthe gorge, rn Sacramentothe Lodo ValJ.ey formation and arm.thwhere of' thickest Chico where in the itBan fills Joaquin the deep Valley gorge, east the of Lodo formationthe Panoche Hills, the where Kreyenhagenthickest in the shal Ban e Joaquin in a large Valley area eastac ross of thethe Panochecentral Hills, parts the of the KreyenhagenSan Joaquin shal e Valley, in a large and area the acse rossveral the shale central units of parts ofMiocene the age 1n the San Joaquinextreme Valley, southwestern. and the se pa.rt veral of shale the San units Joaquin of MioceneVall age ey, 1n where the they contain extremethe southwestern. fewest interbeds pa.rt of of sands the San tone. Joaquin Vall ey, where Inthey SUJmnary, contain potential. reservoir rocks, of both the fewestpermeable interbeds and of sands tone. In SUJmnary,impermeable potential. types, reservoir are available rocks, atof many both localities permeablew1 thin and the Central impermeableVa.J.J..ey, types, and are 1n available same areas at manyseveral localities potentially w1 thin theuseful Central rock un1 ts are Va.J.J..ey,available and 1n at sameone s1 areas te. nie several selection potentially of areas useful rock un1geologic&ily ts are favorable availablefor at"'8.ste one s1 disposal, te. nie selectiontherefore, of will areas be geologic&ilygoverned favorableprimarily by factors for "'8.sterestricting disposal, the therefore, migration will of waste.be governed primarily by factorsMigration barriers restrictingBarriers the migration to the migration of waste. of liquid waste within Migrationrock barriers units are Barriersof to :1.ml)ortance the migration pr1JD&ril.y of liquid waste to pemeable within rock reservoir units are storage. It ia assumed of :1.ml)ortancethat waste pr1JD&ril.y stored in artificia.lly to pemeable created reservoir reservoirs storage.formed It ia assumed 1n impermeable that wasteunits stored will be in permanentlyartificia.lly created sealed reservoirsin, and hence formed 1n impermeablecannot migrate. As much of units willthe bewaste permanently is expected sealed to be in, largely and hence nitric cannot acid or migrate.acid As aluminum much of nitrate the wasteand is heavier expected than to water,be largely a permeable nitric acid reservoir or acid aluminumbounded nitrate by impermeable uni ts and heavierin a sync.line than water, seems, a permeable at first glance, reservoir to be bounded an ideal by impermeableenvironment uni ts for in a sync.linerestricting seems, waste at firstmigration. glance, Tb.is to be ia an an ideal environmentoversimplification, for for account restrictingShou.1.d waste be migration. taken of theTb.is fact ia thatan oversimplification, the reservoir in for accountwhich waste would be Shou.1.dinjected be taken will of be the saturated fact that with the reservoirwater which, in which if it is waste wouldnot already be in injectedmotion will be because saturated of pressurewith water gradients which, ifimposed it is not alreadybeyond in the limits of the motionsyncline, because ofwill pressure start to gradientsm:,ve because imposed of beyond the limits ofdisplacement the by the injected syncline,waste will and start because to m:,ve of because convectional of displacement currents by the injectedgenerated by radiogenic heat. waste andBoth because diffusion of convectionalof the waste into currents the moving generated ground by radiogenicwater heat. and actual Both diffusionmovement of theof the waste waste into dawn the movinggradient ground might takewater and actualplace. The simple movement8YllClinaJ. of the waste stru.cture dawn therefore gradient maymight be take only place. of The simplepartial help in controJ J 1 ng 8YllClinaJ.'Waste stru.cture migration; therefore it may mayindicate be only the directionof partial help inmigration controJ J is1 ngmost likely 'Wasteto migration; f'ollov o it may indicate the direction migration is mostA likely mere certain means of restricting migration of to f'ollovliquid o waste is A mereby certain taking means advantage of restricting of relatively migration impenneable of liquid waste isbarriers. Such barriers by takinga.re advantage present 1n of reasonable relatively abundanceimpenneable in barriers.the Central Such barriersValley of California a.re presentand consist 1n reasonable of facies abundance cbacges w1 in thinthe Centralsandstone uni Valley tsof such California as those and consistresponsible of facies for cbacges oil accunmJation w1 thin sandstone in the Stevens uni ts such assand those at the North Coles responsibleLevee for field oil oraccunmJation iD. the Gatchell in the sand Stevens at the sand Coa.l at the Northjnga Coles Nose field. Levee Pefield rmeab111 or iD. the ty Gatchell barriers sandalso resuat the lt Coa.lfrom sandstonejnga Nose field.tongues that pinch out Pe rmeab1111n. impermeable ty barriers aha.lealso resu units lt fromand tram sandstone sandstone tonguesbeds that truncated pinch out beneath 1n. impermeableu.n.conf'ormities aha.le unitsor agajnst and tram faults. sandstone These migration beds truncatedbarriers beneath are discussed u.n.conf'ormitiesby Hoots, Bear,or agajnst and KJ.einpell faults. These (1954b) migration 1n barriersconnection are discussed with the accumulation by Hoots,Of OUBear, o and KJ.einpell (1954b) 1n connection with the59 accumulation Of OUChanges o in permeability of aandst;0ne uni s 59 undoubtedly occur in most Changesunits in permeabilityand in many ofareas. aandst;0ne The selection uni s undoubtedly of the most occur infavorable most areas for units andsuch in migrationmany areas. barriers The selection will necessa.rily of the most have to favorablefollow areas more for detailed such migrationstuey. The barriers same canwill be necessa.rily said of sai:.dstone have to followtongues more detailedwhich pinch out into stuey. Theimpermeable same can shalebe said uni of ts. sai:.dstone Sandstone tongues beds faulted which pinch outa.!!d into tightly sealed impermeableagainst shale impermeable uni ts. Sandstone uni ts are beds believed faulted to bea.!!d the tightly mostsealed unccmmion type of againstmigration impermeable barriers, uni ts although are believed about to 8 bepercent the most of the unccmmionoil :fields type inof the migrationSan barriers, Joaciuin although Valley obtain about oil8 percent :from fault of the traps and oil :fieldsin an in additionalthe 25 San Joaciuinpercent Valley faulting obtain in combination oil :from fault with traps structure and in and an additional(or) 25facies cbanges percenthas faulting trapped in thecombination oil. On the with other structure band the and ioore (or) or facies cbangesless continual has trappedstructural the oil. activity On the duriDg other Tertiaryband the deposition ioore or less continualwithin the San Joaciuin structuralValley activity area duriDgproduced Tertiary several deposition widespread within the San Joaciuinunconf'ormities and many more of Valley localarea producedextent; each several truncates widespread underlying unconf'ormities beds. and manyMigration more of barriers by local extent;truncated each sandstone truncates units underlying are, therefore, beds. Migration quite barrierscOimOOn by and occur mainl.y truncatedwithin sandstone broad beltsunits alongare, therefore, both the easternquite cOimOOn and and occurwestern mainl.y margins of the within va.l..ley.broad belts The along western both belt the ofeastern truncated and westernbeds is also marginspresent of the in the va.l..ley.Sacramento The western Valley belt butof truncated the eastern beds one is is also absent for presentthe in moatthe part north Sacramentoof the Valley Stockton but arch. the eastern one is absent for the moat partThese north several natural migration barriers may well of the Stocktonbe combined arch. to These severalform Slll natural table reservoirsmigration barriersw1 th the may desired well degreebe combinedof confineme to nt for form Slllstored table radioactive reservoirs waste.w1 th theIn addition, desired degree artificial of confinememigration nt for barriers stored mayradioactive al.so be waste. pra ctical In addition, in scmie artificial circumstances migration . barriersRoedder (1959, P• 45-50) may al.sodiscusses be pra possiblectical in methodsscmie circumstances for such artificial . Roedder (1959, confinementP• 45-50) of waste. discussesAs possiblea means methodsof el.1m1nating for such precipitation artificial confinement of the of waste.waste, which would clog As a meansthe reservoir of el.1m1nating pore space, precipitation acid treatment of the of waste, the which sandstonewould clog prior to the reservoirwaste 1l1Jpore ectionspace, ha.aacid beentreatment suggested. of the Thesandstone clogg:1 prior tong ettect of precipi tat waste 1l1J1cm ectionwoul.d ha.a operate been a• suggested. a migration The barrier clogg:1 beyond ng ettect ofthe precipi area of tat acid 1cm woul.d6o operate a• a migration barrier beyond the area of acidtreatmeD.t, and under suitable conditions c?UJ.d 6o foim a.n adecraate, selfseal treatmeD.t, ba.r.rie,r. and under suitable conditions c?UJ.d foim a.n adecraate,0th.er selfseal considerations ba.r.rie,r.In add.1.tion to the con;trol of waste migration, the 0th.er considerationsselection of a In add.1.tiond1sposaJ. to the site con;trol should oftake waste into migration, account 'What the selectionmight of a be called accidental d1sposaJ.failure site ofshould confinement. take into Such account failure 'What might might :r-esult be called accidentalfrom rupture of the failure reservoirof confinement. by eart.hquake, Such failure leakage might t :r-esultimp erl.y from rupturesw.ed of the wells that reservoirpenetrate by eart.hquake, tb.e storage leakage reservoir, t imp f'aUu't"e. erl.y sw.ed CJf wells thatinJectir.,n equipment, or penetrateleakage tb.e storage tram sur.f'ici&l reservoir, irurta f'aUu't"e. J J a.tions CJf inJectir.,n such as equipment,stCJ7:'8.ge or tax.ks. leakageIn tram general, sur.f'ici&l the hazard irurta of J a.nJ a.tions earthquake such as producing stCJ7:'8.gea rupture tax.ks. 1n a In general,sandstone the hazard reservoir of a.n bed earthquake seem.a remote producing except a 1n rupturethe 1n southerna basin of sandstonethe 8a.nreservoir Joaquin bed Valley.seem.a Thisremote area except is Vf!!r'Y 1n the active southerntecton.ically. basin of For the 8a.nother Joaquin parts Valley. of the CentralThis area Valley, is Vf!!r'Y if a fault active contact tecton.ically.is considered For other partsas a barrierof the Central to fluid Valley, migration, if a thefault possibility contact is of consideredsubsequent movement as a barrierand the to fluidlikelihood migration, of leakage the possibility should be of considered. subsequentIt is alsomovement and theto likelihood be noted thatof leakage surf'1c1al should uncor,.solicJa+ be considered. a. It is also deposits r"8.ct mre severely to be notedto earthquakes, that surf'1c1al and uncor,.solicJa+1 t would be best, a. tramdeposits the r"8.ct mrestand;point severely of the to earthquakes,disposal plantand 1 equipment, t would be tobest, locate tram the the disposal site stand;pointwithin of the the areas disposalof plantlesser equipment, seismic intensity to locate probability the disposal as shownsite on within figurethe areas 13. of lesserIn seismicconsid.e intensity specific probability site locations, as shown account on shouldfigure 13. also be In consid.etaken ofspecific the consequences site locations, of accountthe accidental should surface also be taken ofspillage the consequences of of the accidental surface spillageliquid of waste at the disposal site. The geologic liquid wasteenviromnent at the disposal in wh:1.ch site. The geologic enviromnentit would in thuswh:1.ch fall and steps that could be taken to it wouldcontain thus fall it should and steps that could be taken to contain it shouldbe considered. be considered.The disposal of radioactive waste within an area The disposalunderlain of radioactive by an waste within an area underlainoil orby gasan £1el.d is to be avoided 1'"ca1J.Se of the oil or gasuncertainty £1el.d is of.to be avoided 1'"ca1J.Se of the uncertainty61 of. 61 completely sealing all of the previougly drilled completelywells sealing and test all boles. of the previougly drilled wells and test boles.Figure 14 shows the location of cozmnercial oil Figure and14 shows gas fields the locationin the of cozmnercial oil and gas fields inCentral the Valley and the approximate density of Centraldeep Valley wells and per the township approximate density of deep wells per townshipthroughout the valley. In general, the eastern side throughoutas far the south valley. as In general, the eastern side as far south asFresno and the extreme oorthern end of the Central FresnoValley and the seem extreme more oorthern end of the Central Valley favorabJ.eseem more f'rom the standpoint of rn1n1zmun favorabJ.edeep-well f'rom thedensity, standpoint and the of rn1n1zmun deep-well density,southern and the end and most of the western side of the southernSan end Joaquin and most Valley of the and western side of the San Joaquinthe Valley area betweenand and west of Stockton and the areaSacram between to andin t.lle west Sacramento of Stockton and Sacram to in t.lle SacramentoVaJ.J.ey is less favorable. VaJ.J.eyThe is regionsless favorable. of greater hazards from deep wells and The regionsfrom surf1c1&1of greater hazards from deep wells and from surf1c1&1eeismic intensity roughly coincide {compare figs. eeismic13 intensity and 14). roughly The coincide {compare figs. 13 and 14). Thelo cation of areas with greater well densiti ea a.lso lo cationroughly of areas coincides with greater well densiti ea a.lso roughlyWith coincides thicker sections of basin fill, with the With thickerfolded.trench sections structural of basin fill, with the folded.trench structuralelement of the Central Vall ey, and w1 th most of elementthe of areas the Central in which Vall thick ey, and w1 th most of the areas inimpermeable which thick uni ts are present. This coincidence impermeablemakes uniartificial ts are present. This coincidence makes artificialreservoir construction in imperm eable uni ts seem reservoirless construction pra.cticaJ. fo in rimperm eable uni ts seem less pra.cticaJ.waste fo atoragr e. waste atoragAnother e. consideration makes impermeable uni ts Anotherseem consideration less practicaJ.. makes impermeable uni ts seem less practicaJ..Sandstone ordinarily has about twice the heat Sandstoneconductance ordinarily of has shale about twice the heat conductance(Birch, of 1954, shale p. 658) and thus would be more (Birch,effective 1954, p. when658) andconsidering thus would be more effective when consideringdissipation of radiogenic heat. dissipationIn conclusion, of radiogenic the easternheat. side of the Central In conclusion,Valley of the Calif'ornia, eastern side of the Central Valley of Calif'ornia,as .:far south as Fresno, seems to be the most as .:farpromising south as Fresno, area for seems the to be the most promising area forseJ.ec the tion of a radioactive-waste disposal site. seJ.ec tionHere, of south a radioactive-waste of the disposal site. Here, south ofStockton the arch, the geologic enviromnent to be Stocktonsought arch, is the a thick geologic sandstone enviromnent to be sought is a thick sandstonebed tonguing westward into impermeable sb&le bed tonguinguni ts and westward along its into impermeable sb&le uni ts and alongeastern its end warped upward, truncated ., and sealed easternby end an warped overlying upward, truncated ., and sealed by an overlying- - 0 0 SC ALE SC ALEO JO 20 40 60 MILES O JO 20!!!!!!!!!!liiiiiiiii!!!!!!!!!5iiiii 40 60 MILES !!!!!5 2 !!!!!!!!!!liiiiiiiii!!!!!!!!!5iiiiiEXPLAili\TION !!!!!5 2 EXPLAili\TIOND D 1 to 5 wells per 1 to 5 wellstownship per township

6 or more wells 6 or moreper wellstownship per township.. .. Oil or gas field Oil or gasHeavy field line is boundary of Heavy Cretaceousline is boundary and Cenozoic of Cretaceousrocks and within Cenozoic Central Valley rocks withinFigure Central 14.--011 Valley and 8as fields and ,rell density of Figure Central14.--011 Valley. and 8as fields and ,rell density of Central Valley.younger shale u.nit. NortJi of the Stockton arch youngerw""estwa.rd-tbinn:fng shale u.nit. NortJi of sandstone the Stockton arch w""estwa.rd-tbinn:fngtongues are less sandstoneabundant and have not beer. tongueswarped are less and abundant truncated and have not beer. warped and truncatedto the east. A study of hydrologic conditions might to the east.reveal A pl.acesstudy of were hydrologic conditions might reveal pl.aces eaetwardwere migrati on would be slow enough to stay eaetwardwithin migrati safe on lim.1ts. would be slow enough to stay within safe lim.1ts.SEUm'ED REFER.E:lCES SEUm'EDAlmgren, REFER.E:lCES A. A. , and Schla.x, W. N. , 1957, Post Almgren,Ehcene A. A. age , and for Schla.x, W. N. , 1957, Post Ehcene age for"Markley gorge" fill, Sacramento Valley, California: "MarkleyAm. gorge" Ass oc. fill, Sacramento Valley, California: Am. Ass oc.Petroleum Geologists Bull., , • 41, no. 2, p. 326-330. PetroleumAnderson, Geologists C. A., Bull., 1933, , • The 41, no.Tuscan 2, p. formation326-330. of Anderson,northern C. A., Ca.J.1.fornia: 1933, The Tuscan formation of northern Ca.J.1.fornia:California Univ. Publ., Dept. Geol. Sci. Bull., v. 23, Californiano. 7,Univ. Publ., Dept. Geol. Sci. Bull., v. 23, no. 7, p. 215.276.p. 215.276. Anderson,Anderson, C. A., andC. A., Russell, and Russell, R. D., 1939,R. D., Tert 1939, ia...7 Tert fo:nna..tionsia...7 fo:nna..tions of of northern.northern. Sacramento Sacramento Valley, Valley, Ca.l.ifomia: Ca.l.ifomia: California Div. Mines,California Div. Mines, State MineralogistsState Mineralogists Rept., v.Rept., 35, no. v. 35, 3, P• no. 219 3, P•.. 253. 219 .. 253. Anderson,Anderson, F. M., 1905,F. M., A 1905, stratigraphic A stratigraphic stucy- instucy- the in the MountMount Diablo Diablo Range Rangeof California: of California: Calif'. Acad.Calif'. Sci.Acad. Proc., Sci. 3rdProc., ser., 3rd v. 2, no. 2. ser., v. 2, Anderson,no. 2. Robert, and Pack, R. w., 1915, Geology and oil resourcesAnderson, of Robert, and Pack, R. w., 1915, Geology the westand border oil resources of the San of Joaquin Valley north of CoaJ:inga,the west border of the San Joaquin Valley north of California:CoaJ:inga, u. s. Geol. SUrvey Bull. 6o3, 220 P• Arnold,California: Ralph, and u. .Anderson, s. Geol. SUrvey Robert, Bull. 1910, 6o3, Geology 220 P• and oil resourcesArnold, Ralph, and .Anderson, Robert, 1910, of the CoalingaGeology anddistrict, oil resources California: u. S. Geol. Survey Bull. 398, 354of p.the Coalinga district, California: u. S. Geol. Birch, Francis,Survey Bull. 1954, The present status of geothermal investigations:398, 354 p. Geophysics,Birch, v. Francis, 19, p. 645-659. 1954, The present status of 64 geothermal investigations: Bowen,Geophysics, O. E., Jr., and v. 19,Cri:pp, p. 645-659. R. A., J-,:,, 1951, Geologic map of64 the San FranciscoBowen, BayO. E., region: Jr., and California Cri:pp, R. Div. A., MinesJ-,:,, 1951, Bull. 154, p. 161-174.Geologic map of the Bramlette,San FranciscoM. N., 1946, Bay The region: Monterey California fonnation Div. Mines of CaJ.iforniaBull. and154, the p. 161-174. origin ofBramlette, its siliceous M. N.,rocks: 1946, u. s.The Geol. Monterey SUrvey fonnation Prof. Paper of 212, CaJ.ifornia and the 57 p. (1947].origin of its siliceous rocks: u. s. Geol. SUrvey Prof. Briggs,Paper L. I., Jr.,212, 1953, Geology of the Ortigalita Peak quadrangle,57 p. (1947]. California:Briggs, California L. I., Jr., Div. 1953, Mines Geology Bull. of 167. the Ortigalita Clark, PeakB. L., quadrangle,1915, Fauna of the San Pabl "' group of middJ.eCalifornia: Ca.lifornia: California Div. Mines Bull. 167. CaliforniaClark, Univ. B. L., Publ., 1915, Dept. Fauna Geology of the SanBull., Pabl v. 8, "' no.group 22, ofp. 3 85.572.middJ.e Ca.lifornia: ----- 1918,California The San Univ. Lorenzo Publ., series Dept. of Geology middle California:Bull., v. 8, Californiano. 22, p. 3 85.572. Uni v. -----Publ. 1918, , Dept. The Geology San Lorenzo Bull., v. series ll, no. of 2, middle p. 45-234. ----- 1921a,California: The stratigraphy California and faunal rela tionship s ot the Uni v. Publ. , Dept. Geology Bull., v. ll, no. 2, p. Meganos45-234. group, middle Eocene of California: Jour. Geology,----- v. 1921a,29, The stratigraphy and faunal rela no. 7, P•tionship 125-165. s ot the ----- 192lb,Meganos The marinegroup, middleTertiary Eocene of the Westof California: Coast of Jour. the Unit edGeology, v. 29, States; no.its sequence 7, P• 125-165. , pa1eogeograpby, and the problems of correlation:----- 192lb,Jciw:. Geology,The marine v. 29, Tertiary no. 7, ofP• the 583-614. West Coast Clar k,of B. the L., endUnit Anderson, ed c. A., 1938, Wheatland formationStates; and its its sequence , pa1eogeograpby, and the re.J..ationproblems to early of Tertiary andesites in the Sierra Nevada.:correlation: Geol. Jciw:. Geology, v. 29, no. 7, P• 583-614. Soc. AmericaClar k, Bull.,B. L., v.end 49, Anderson, no. 6 , P• c.931.956. A., 1938, Wheatland Crook,formation T. H., and and Kirby, its J. M., 1935, Capa.y formation [abs.]: re.J..ationGeol, to early Tertiary andesites in the Sierra Soc . AmericaNevada.: Proc. Geol. for 1934, p. 334-335 • Durham,Soc. J. Americaw., 1954 ,Bull., The marinev. 49, no. cenozoic 6 , P• 931.956. of so uth ern Ca.lif' orn.ia:Crook, T. H., and Kirby, J. M., 1935, Capa.y Californiaformation Div . Mines [abs.]: Bull· Geol, 170, chap, 3, pt. 3, P• 15-31, Durham,Soc J. . W.,America Jahns, Proc. R. H., for and 1934, 5avage, p. 334-335 D, E., 1• 954, Marinenomoa.rineDurham, J. w., 1954 , The marine cenozoic of so relationshipsuth ern in Ca.lif' the Cenozoic orn.ia: section of California: C&l.if'oCalifornia rnia Div .Div Mines . Mines Bull· Bull· 170, 170,cb&P• chap, 3, sec. 3, pt. 7 , 3,P• P• 59-71•15-31, Forrest,Durham, L. c., 1943, J. W., quence Jahns, of R. Oligocene H., and 5avage, fon:a-;:.ans D, E., of 1 CaJ 1 forni.a:954, Marinenomoa.rine Ca.l.Uornia.relationships Div. Min.es in the Bull. Cenozoic llB, p. section199-200. of California: Frick., C&l.if'o.J. Do, H.a.rd1.ng, rnia Div . MinesT. P., andBull· Ma-s, 170, cb&P•A. W., 3,1959, sec. 7 , EbceneP• gorge 59-71• in nor+-..b.ernForrest, Sacramt!rlto L. c., 1943, Valleyquence (abs. of Oligocene J : Am. Assoc. Petroleumfon:a-;:.ans Geologists of CaJ 1 forni.a: Bull., v.Ca.l.Uornia. 43, no. 1, p. Div. 255. Min.es Bull. llB, p. 199-200. Ful.me1:,Frick., C. F., .J. 1954,Do, H.a.rd1.ng, Stratigraphy T. andP., and pa].eont/.>logy Ma-s, A. W., of the typical1959, Ebcene gorge in Markleynor+-..b.ern and Nortonvill Sacramt!rlto fonration Valley of central (abs. CaliforniaJ : Am. [abs. ] Assoc.: Petroleum Geologists Geolo Soc.Bull., America v. 43, no. Bull., 1, p. v. 255. 65, no. l2 , p. 1341. Garrison,Ful.me1:, L. E., 1959, C. F., Miocene 1954, Stratigraphy foxmation and north of CoaJinga,pa].eont/.>logy Call.fornia: of the typical Jour. Paleontology,Markley and v.Nortonvill 33, no. 4, fonration po 662-669. of central Goudkoff'California , P. P., [abs.1945, ] Stratigraphy : rel.a tions of Upper CretaceousGeolo in Soc. America Bull., v. 65, no. l2 , p. 1341. Great Valley,Garrison, California: L. E., 1959, Am. Miocene Assoc. Petroleum foxmation north of GeologistsCoaJinga, Bull., Call.fornia: v. 29, no.Jour. 7, p.Paleontology, 956-1007. v. 33, no. 4, po 662-669. Harding,Goudkoff' Tod, 1958, , P. IJP., ano 1945, Seco Stratigraphy and Perkins rel.a Lake tions gas of fields, ButteUpper and Cretaceous in TehamaGreat Counties, Valley, California California: [abs.]: Am. Am.Assoc. Asiroc. Petroleum PetroleumGeologists Bull., Geologistsv. 29, Bull., no. 7,v. p.42, 956-1007. no. 1, p. 216. Hobson,Harding, H o n., Tod,1951, 1958, Bacrcwento IJ ano Seco Valley: and Am. Perkins Assoc. Lake Petroleumgas fields, Butte and GeologistsTehama Bull., Counties, v. 35, no. California 2, p. 209-214. [abs.]: Am. Asiroc. Hoots,Petroleum H o w., 1930, Geology and oil resources along the southernGeologists Bull., v. 42, no. 1, p. 216. borderHobson, of San Joaquin H o n., Valley, 1951, Bacrcwento Calii'ornia: Valley:u. S. Geol. Am. SurveyAssoc. Petroleum Bull. 812,Geologists pt. 2 , p. Bull., 243-332· v. 35, no. 2, p. 209-214. Hoots,Hoots, H0 W OH ,o Bear, w., 1930, T. L Geology0 , and IQ.einpell, and oil resources W. D., 1954&,along Geologic the southern summaryborder of the of SanSan JoaquinJoaquin Valley,Valley, California:Calii'ornia: California u. S. Div. Geol. Survey Mines Bull. 812,170, pt.chap. 2 , 2,p. pt.243-332· 8, P• ll3-l29. ----- 1954b,Hoots, Stratigraphic H0 W O , Bear, traps T. for L 0oil , and and IQ.einpell, gas in the SanW. JoaquinD., 1954&, Geologic Valley:summary California of Div. the Min.esSan Joaquin Bull. 170,Valley, chap. California: 9, pt. 4, P• 29-32. California Div. 66 Mines Bull. 170, chap. 2, pt. 8, P• ll3-l29. Huey, Ao----- So, 1954b, 191'8, Stratigraphic Geology of the traps Tesla. for oilquadrangle, and gas in California.:the San Calif>ornia Joaquin Divo MinesValley: Bull California o 140, 75 Div. P o Min.es Bull. 170, chap. 9, pt. Irwin, W4, P• • P., 29-32. 1957, Franciscan gzxJ1zp 1n Coast Ra:zl8es and its66 equivalents in SacramentoHuey, Ao Valley, So, 191'8, Califrnia: Geology Amo of Aas,:Jc.the Tesla. Petrole1..tmquadrangle, Geologists California.: Calif>ornia Bull., v.Divo 41, no. Mines 10, pBull . 2284-2297. o 140, 75 P o K:.Ukemzy,Irwin, J. W E., • 1951,P., 1957, San Franciscan Joaqv.1.u Va.J..ley: gzxJ1zp 1nA:rr!. Coast Assoc. Ra:zl8esPetroleum and its equivalents Geologist,13in Sacramento Bull., v. 35, Valley, no. 2, Califrnia: p. 215-218. Amo Aas,:Jc. Kirby, Petrole1..tmJ. M. , 1943, UpperGeologists Cretaceous stratigraphy of west side ofBull., v. 41, no. 10, p . 2284-2297. SacramentoK:.Ukemzy, VaJ.ley J. SfJUth E., 1951, of Willows,San Joaqv.1.u Glenn Va.J..ley: Co,mty, California:A:rr!. Am. Assoc. Petroleum Assoc. Geologist,13Petroleum Geologists Bull., v. 35, Bull., no. v.2, 27,p. 215-218. nn. 3, p. 279-305. La:im1ng,Kirby, Boria, J. M. 1943, , 1943, Ebcene Upper foram1n1feral Cretaceous stratigraphy correlatiollB in California:of west side of CaliforniaSacramento Div. Mines VaJ.ley Bull. SfJUth llB, p. 193-198.of Willows, Glenn Lawson,Co,mty, A. c., 1914, California: San Francisco Am. folio: u. s. Geol. Survey Geol. Assoc. Petroleum Geologists Bull., v. 27, nn. 3, p. Atlas, Folio279-305. 193. Lael, Wayne,La:im1ng, and Boria, Corey, 1943, w. H. Ebcene , 1932, foram1n1feralThe Vaqueros formation,correlatiollB lover in California: MicceneCalifornia of California; Div. Mines I-PaJ.eont')logy: Bull. llB, p. Cal 193-198. ifornia Univ. Publ. , Lawson, A. c., 1914, San Francisco folio: u. s. Geol. Dept. GeologySurvey Geol. Bull., v. 22, oo. 3, .Po 31-410., Mall ory,Atlas, v. s., Folio 1959, 193. Lower Tertiary biostratigraphy of' the CaliforniaLael, Wayne, and Corey, w. H. , 1932, The Coast RangesVaqueros : Tulsa, formation, Am. Assoc. lover Petroleum Geologists, 298 p. Miccene of California; I-PaJ.eont')logy: Cal ifornia Marks,Univ. J. G., Publ.1941, ,Stratigrapey of the Tejon formation 1n its typeDept. Geology Bull., v. 22, oo. 3, .Po 31-410., area, KernMall County, ory, v. s., California 1959, Lower (abs.]: Tertiary Geol. biostratigraphySoc. America Bull., of' the California v. 52, no.Coast 12, Rangespt. 2, p. :1922. Tulsa, Am. Assoc. Petroleum Merriam,Geologists, c. w., and 298 Turner, p. F. E., 1937, The Capay middleMarks, F.ocene J. of'G., 1941, Stratigrapey of the Tejon California:formation California 1n its Univ., type Pub., Dept. Geology Bull., v. 24, area, Kern County, California (abs.]: Geol. Soc. noo 6, Americap. 91-114. Bull., Murphy,v. 52,M. no.A., 1956,12, pt. wwer 2, p. 1922.Cretaceous stra.tigZ"B.phic units ofMerriam, northern c. w., and Turner, F. E., 1937, The Capay California:middle Am. F.ocene Assoc. of' Petroleum Geologists Bull., v. 4o, no. 9, California: California Univ., Pub., Dept. Geology p. 2098-2119.Bull., v. 24, Oakeshott,noo 6,G. p. B., 91-114. Braun, L. T. Jennings, c. w., and Wells, Ruth, 1952,Murphy, M. A., 1956, wwer Cretaceous Exploratorystra.tigZ"B.phic wells drilled units outside of northern of oil and gas fields in CaliforniaCalifornia: to December Am. Assoc. 31, 1950: Petroleum California Geologists Div. Mines Bull., Spec. v. 4o, no. 9, Rept. 23.p. 2098-2119. Pack, R.Oakeshott, w., and English, G. B., Braun, w. A., 1914,L. T. Jennings,Geology andc. w., oil and prospectsWells, in Ruth, 1952, Waltham,Exploratory Priest, Bitterwater, wells drilled and outside Peachtree of oil Valleys, and gas California,fields in with notesCalifornia on coal: to u. December s. Geol. Survey 31, 1950: Bull. California 581-D, p. Div. ll9-16o.Mines Spec. Payne, Rept.M. B., 23. 1951, Type reno formation and overl.yi.ng EbcenePack, strata R. w., and English, w. A., 1914, Geology and on the oilwest prospects side of the in San Joaquin Valley, Fresno and MercedWaltham, Priest, Bitterwater, and Peachtree Counties,Valleys, California: California, California Div. Mines Spec. Rept. 9. Peck, D.with L., notesImlay, on R. coal: w., and u. s. Popenoe, Geol. Survey W. P., Bull. 1956, 581-D, Upper p.Cretaceous ll9-16o. rocks ofPayne, parts M.of southwesternB., 1951, Type Oregon reno formation and northern and Ca.lif ornia:overl.yi.ng Ebcene strata Am. Assoc.on the Petroleum west side Geologistsof the San JoaquinBull., v. 4o,Valley, no. 8,Fresno p. 1968- and Merced 1984. Counties, California: California Div. Mines Spec. Piper, A.Rept. M., 9. Ga.le, H. s., Thoma&, H. E., and Robin8on, T. W., Peck,1939, D. L., Imlay, R. w., and Popenoe, W. P., 1956, GeologyUpper and ground-waterCretaceous hydrology of the Mokelumne area, rocks of parts of southwestern Oregon and California:northern u. s. Geol.Ca.lif Surveyornia: Water-Supply Paper 78o, 230 p. Am. Assoc. Petroleum Geologists Bull., v. 4o, no. 8, Popenoe,p. 1968- w. P., 1943, Cretaceous--Eastside Sacramento Valley,1984. Shasta and ButtePiper, counties, A. M., California:Ga.le, H. s., Am. Thoma&, Assoc. H. Petroleum E., and GeologistRobin8on, a T. W., 1939, Bull., v.Geology 27, no. 3,and P• ground-water 3o6.3l2 • hydrology of the Reed, R.Mokelumne D., 1933, Geology area, of California: Tulsa, Okla., Am. Assoc.California: u. s. Geol. Survey Water-Supply Paper Petroleum78o, Geologists,230 p. 355 P• 68 Popenoe, w. P., 1943, Cretaceous--Eastside Repenn1Sacramento ng, C • A.; Valley, 1959, Geologic.Shasta summary of -w San Ju.a.D andBasin, Butte Nev counties, Mexico, California: Am. Assoc. with ref'encePetroleum to disposal Geologist of liquid a ra.dtoactive waste: u. s. Geol. Bull., v. 27, no. 3, P• 3o6.3l2 • SurveyReed, open-f'ile R. D., report 1933, TE'.I Geology 6o3, of57 California: p. Tulsa, Richter,Okla., C. F., Am. 1959, Assoc. Seismic ona.lization: Seimnol. Boe. AmericaPetroleum Geologists, 355 P• Bull., v.68 49, no. 2, P• J23-J.62. Robinaon,Repenn1 G. D., ng, 1956, C • Hayward,A.; 1959, Geologic. Ca.l.if'ornia: summary U. S. Geol. of - Surveyw Geol. San Ju.a.D Basin, Nev Mexico, Quad. withMap ref'enceGQ-88. to disposal of liquid ra.dtoactive Roedder,waste: Mwin, u. s. 1959, Geol. Problems in the dispoaa.l of a.cid alumimtmSurvey nitrate open-f'ile report TE'.I 6o3, 57 p. high.levelRichter, radioactive C. F., 1959, waste Seismic aolut1on.a ona.lization: by i.D.jection into dee-plyingSeimnol. Boe. America permeableBull., formation: v. 49, no. 2,u. P•s. l.J23-J.62. Survey Bull. lo88, 65 p. Savage,Robinaon, D. E., 1958, G. Nonmar1ne D., 1956, Hayward, lower PJ..1ocene Ca.l.if'ornia: U. S. aedimentsGeol. in Survey Ca.lif'orn.1.a: Geol. CsJ.if'orniaQuad. Univ. Map Pt.tbl., GQ-88. Dept. Geol. Sci. Bull., v. 31, no. 1, p. 1-26.Roedder, Mwin, 1959, Problems in the dispoaa.l of ScboeJ a.cidJ ba:mer, alumimtm J. E. , and nitrate Kinne>J, D. M. , 1953, Geology of portionhigh.level of' radioactive waste aolut1on.a by Tumeyi.D.jection and Panache into Hille, dee-plying Fresno County, California: U. s. Geol.permeable formation: u. s. l. Survey Bull. lo88, 65 Surveyp. Oil a.nd Gas Inv. Map OM-128. Stewart,,Savage, Ralph, D. 191'6, E., 1958, C..eolDgy Nonmar1ne of Rt:ef lower Ridge-Coa PJ..1ocene J1 nga di&tr!.ct,aediments in Ca.lif'orn.1.a: Ca.J.ti>ornia:CsJ.if'ornia u. s. Univ.Geol. SurveyPt.tbl., Dept.Prof. PaperGeol. 205-C,Sci. Bull., p. 81-v. ll5, 31, no. 1, [1947 ].p. 1-26. Stewart,ScboeJ Ralph, J ba:mer,Popen.oe, J. E. W. , and P., and Kinne>J, Snavely, D. M.P. D., , 1953, Jr., 19 44, Geology of portion of' Te rtiaryTumey and late and Upper Panache Cretaceous Hille, Fresno stratigraphy County, of west borderCalifornia: U. s. Geol. of San SurveyJ oaquin Oil Valley, a.nd Gasnorth Inv. of MapPanoche OM-128. Creek, Fresno, Merced,Stewart,, Ralph, 191'6, C..eolDgy of Rt:ef Ridge- &lld Sta.nisl.au.8Coa J1 nga counties, di&tr!.ct, C&liforn..1.a: u. s. Geol. SurveyCa.J.ti>ornia: Oil u. s. Geol. Survey Prof. Paper 205-C, and Ge.ap. 81-ll5,Inv. Prelim. Chart 6 • Ta:tt, J.[1947 A., 1935, ]. Geology of )bunt Diablo and vicinity: Geol. Soc.Stewart, Ralph, Popen.oe, W. P., and Snavely, P. D., AmericaJr., BulJ.., 19 44, v. 46, no. 7, P• 1079.llOO. • Te rtiary and late Upper Cretaceous stratigraphy of Van Covering,west border Martin, and All , H. B., 1943, Devils Den oil field:of San J oaquin Valley, north of Panoche Creek, California.Fresno, Div. Merced, Min.es Biill. l.18, P• 496 -501. Weaver,&lld C. Sta.nisl.au.8E., 1949, Geology counties, of the C&liforn..1.a: Coast F.u8ea u. s. Geol. 1.JmnediatelySurvey Oilaorth of the San Franciacoand Ge.a Bay Inv. region, Prelim. California: Chart 6 • Geol. Soc • .AmericaTa:tt, Mem. J. A., 35,1935, Geology of )bunt Diablo and 242 p. vicinity: Geol. Soc. White,America B. T., 194o, BulJ.., Eocene v. 46, Yokut no. 7, aan.dstoneP• 1079.llOO. north of Coa.J 1nga,• California.: .Am. Assoc.Van Covering, Petroleum Martin, Geologiata and AllBi.1.ll., , H. B.,v. 24, 1943, no. Devils 10, P• 1722-1751.Den oil field: Woodr1.ng,California. W. P., Div. Stewart, Min.es Ralph, Biill. andl.18, Richarda, P• 496 -501. R. W., 1940, GeologyWeaver, of C. E., 1949, Geology of the Coast F.u8ea the Kettleman1.Jmnediately Hilla oil aorth field, of California: the u. s. Geol. SUrvey P rof. PaperSan Franciaco 195, 170 P•Bay (1941] region, • California: Geol. Soc • .America Mem. 35, 242 p. White, B. T., 194o, Eocene Yokut aan.dstone north of Coa.J 1nga, California.: .Am. Assoc. Petroleum Geologiata Bi.1.ll., v. 24, no. 10, P• 1722-1751. Woodr1.ng, W. P., Stewart, Ralph, and Richarda, R. W., 1940, Geology of the Kettleman Hilla oil field, California: u. s. Geol. SUrvey P rof. Paper 195, 170 P• (1941] • 57

interest. These rocks il'lclude parts of the TeJon., San 12Digd.1o., and

Tecuya f'ormati,:,ns. This area. is, however, quite acti ve tectonically;

most major historic earthquakes in the Central Valley have centered here.

The southern basin, therefor e, i s not ~onsidered further at th.ts t ime.

Ar-t1f'1cial res ervoirs in shale units.--Artificial reservoirs in

shale might be created 1n a ftN units, but in general thick bodies of

s hale are not as widely avai lable as are sandstone reservoirs. Many of

t he pre dom:1.nantly shale units are 1nterbedded w1 th thin beda of sand­

stone whic h are believed to be permeable. Those units that seem to

have low enough permeability and thickness for use w1 th artificially

created reservoirs are the Capay shale in the southern Sacramento ValJ.ey

and arm.th of' Chico where it fills the deep gorge, the Lodo format ion

where thicke st in t he Ban Joaquin Valley east of the Panoche Hills, the

Kreyenhagen shale in a large area across the central parts of the

San J oaquin Valley, and the several shale units of Miocene age 1n the

extr eme sout hwestern. pa.rt of the San Joaquin Valley, where they contain

the f ewe st inter beds of sandstone.

In SUJmnary, potential. reservoir rocks, of both permeable and

impermeable t ype s , are available at many localities w1 thin the Cent ral

Va.J.J..ey, and 1n same areas several potentially useful rock un1ts are

a vailable a t one s1te. nie selection of areas geologic&ily favorable

f or "'8.s t e disposal, therefore, will be governed primarily by factors r estricting the migrati on of waste.

Migration barriers

Barriers to the migration of liquid waste within rock units are of :1.ml)ortance pr1JD&ril.y to pemeable reservoir storage. It ia assumed t hat waste stored in artificia.lly cr eated reservoirs formed 1n impermeable

units will b e p ermanently sealed in, and hence cannot migrate. As much of

the waste is expected to be largely nitric acid or acid aluminum nitrate

and heavier t han water, a permeable r eservoir bounded by impermeable units

in a sync.l ine seems, at first glance, to be an ideal environment for

r estricting waste migration. Tb.is ia an oversimplification, for account

Shou.1.d be taken of the fact that the reservoir in which waste would be

injec ted will be saturated with water which, if i t is not already in

motion because of pressure gradients imposed beyond the limits of the

syncl ine, will start to m:,ve because of displacement by the inject ed

waste and because of convectional currents generated by radiogenic heat.

Both diffusion of the waste into the moving ground water and actual

movement of t h e waste dawn gradient might take place. The simple

8 YllClinaJ. s tru.cture theref ore may be only of partial help in cont roJ J 1 ng

'Waste migration; it may indicat e the direction migration is most likely

to f'ollovo

A mere c ertain means of restricting migration of liquid waste i s by taking advantage of relatively impenneable barriers. Such barriers a.re p r esent 1n reasonable abundance in the Central Valley of California and consi s t of f aci es cbacges w1 thin sandstone units such as those r esponsi ble for oil accunmJation in the Stevens sand at the North Coles

Levee field or iD. the Gatchell sand at the Coa.l jnga Nose field.

Permeab111ty barriers also result from sandstone tongues that pinch out

1n. impermeable aha.le units and tram sandstone beds truncated beneath u.n.conf'ormities or agajnst faults. These migration barriers are discussed by Hoots , Bear, and KJ.einpell (1954b) 1n connection with the accumulation

Of OUo 59

Changes in permeability of aandst;0ne uni s undoubtedly occur in most

units and in many areas. The selection of the most favorable areas for

such migration barriers will necessa.rily have to f ollow more detailed

stuey. The same can be said of sai:.dstone tongues which pinch out into

impermeable shale units. Sandstone beds faulted a.!!d tightly sealed

against impermeable units are believed to be the most unccmmion type of

migration barriers, although about 8 percent of the oil :fields in the

San Joaciuin Valley obtain oil :from fault traps and in an additional 25

percent faulting in combination with structure and (or) facies cbanges

has trapped the oil. On the other band the ioore or less continual

structural activity duriDg Tertiary deposition within the San Joaciuin

Valley area produced several widespread unconf'ormit ies and many more of

local extent; each truncates underlying beds. Migration barriers by

truncated sandstone units are, therefore, quite cOimOOn and occur mainl.y

within broad belts along both the eastern and western margins of the

va.l..ley. The western belt of truncated beds is also present in the

Sacramento Valley but the eastern one is absent for the moat part north

of the Stockton arch.

These several natural migration barriers may well be combined to

form Sllltable reservoirs w1 th the desired degree of confinement for

stored radioactive waste. In addition, artificial migration barriers may al.so be practical in scmie circumstances. Roedder (1959, P• 45-50) discusses possible methods for such artificial confinement of waste.

As a means of el.1m1nating precipitation of the waste, which would clog the reservoir pore space, acid treatment of the sandstone prior to waste 1l1J ection ha.a been suggested. The clogg:1 ng ettect of precipita­ t1cm woul.d operate a• a migration barrier beyond the area of acid 6o

treatmeD.t, and under suitable conditions c?UJ.d foim a.n a decraate, self­

seal~ ba.r.rie,r.

0th.er considerations

In add.1.tion to t he con;trol of waste migration, the selection of a

d1sposaJ. site should take into account 'What might be called accidental

failure of confinement. Such failure might :r-esult from rupture of the

r eservoir by eart.hquake, l eakage t~ imp~erl.y sw.ed wells that

penetrate tb.e storage r eservoir, f'aUu't"e. CJ f inJecti r.,n equipment , or

leakage tram sur.f'ici&l irurta J J a.tions such as stCJ7:'8.ge tax.ks.

In general, the hazard of a.n earthquake producing a rupture 1n a

sandstone reservoir bed seem.a remote except 1n the southern basin of the 8a.n Joaquin Valley. This area is Vf!!r'Y active tecton.ically. For other parts of the Central Valley, if a fault contact is considered a s a barrier to fluid migration, the possi bility of subsequent move­ ment and the likelihood of leakage should be considered. It is also to be noted that surf'1c1al uncor,.solicJa+~a. deposi ts r "8.ct m re severely to earthquakes, and 1 t would be best, tram the stand;point of the

disposal plant equipment, to locat e the dispo sal site within the areas of lesser seismic intensity probability as shown on figure 13.

In consid.e~ specific site locations, account should also be taken of the consequences of the accidental surface spillage of liquid waste at the disposal site. The geologic enviromnent in wh:1.ch it would thus fall and steps that could be taken to contain it should be considered. The disposal of radioactive waste within an area underlain by an oil or gas £1el.d is to be avoided 1'"ca1J.Se of the uncertainty of. 61

completely sealing all of the previougly drilled wells and test boles.

Figure 14 shows the location of cozmnercial oil and gas fields in the

Central Valley and the approximate density of deep wells per township

throughout the valley. In general, the eastern side as far south as

Fresno and the extreme oorthern end of the Central Valley seem more

favorabJ.e f'rom the standpoint of rn1n1zmun deep-well density, and the

southern end and most of the western side of the San Joaquin Valley and

the area between and west of Stockton and Sacram~to in t.lle Sacramento

VaJ.J.ey is less favorable.

The regions of greater hazards from deep wells and from surf1c1&1

eeismic intensity roughly coincide {compare figs. 13 and 14). The

location of areas with greater well densiti ea a.lso roughly coincides

With thicker sect ions of basin fill, with the folded.trench structural

element of the Central Valley, and w1 th most of the areas in which thick

impermeable units are present. This coincidence makes artificial

reservoir construction in impermeable units seem less pra.cticaJ. for

waste atorage.

Another consideration makes impermeable units seem less practicaJ..

Sandstone ordinarily has about twice the heat conductance of shale

(Birch, 1954, p. 658) and thus would be more effective when considering

dissipation of radiogenic heat. In conclusion, the eastern side of the Central Valley of Calif'ornia,

as .:far south as Fresno, seems to be the most promising area for the

seJ.ection of a radioactive-waste disposal site. Here, south of the

Stockton arch, the geologic enviromnent to be sought is a thick sand­

stone bed tonguing westward into impermeable sb&le units and along its eastern end warped upward, truncated., and sealed by an overlying EXPLAili\TION D 1 to 5 wells per township

~ ~ 6 or more wells per town.. ship Oil or gas fiel d

Heavy l ine is boundary of Cr etaceous and Cenozoic rocks within Central Valley

-

0

S C AL E

O JO 20 40 60 MILES !!!!!!!!!!liiiiiiiii!!!!!!!!!5iiiii~ !!!!!5~2

Figure 14.--011 and 8as fiel ds and ,rell density of Central Valley. younger shale u.nit. NortJi of the Stockton arch w""estwa.rd-tbinn:fng sand­

stone tongues are l ess abundant and have not beer. warped and truncated

to the east. A study of hydrologic conditions might reveal pl.aces were

eaetward migration would be slow enough to stay within safe lim.1ts.

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•