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Late Quaternary Depositional History, Sea-Level Changes, and Vertical Crustal Movement, Southern Bay,

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1014

This page intentionally left blank LATE QUATERNARY DEPOSIT IONAL HI§TOR Y, HOLOCENE SEA-LEVEL CHANGES; AND VERTICAL CRUSTAL MOVEMENT, SOUTHERN , CALIFORNIA

Late Quaternary Depositional History, Holocene Sea-Level Changes, and Vertical Crustal Movement, Southern San Francisco Bay, California

By BRIAN F. ATWA.rER, CHARLES \V. BEDEL, ond EDWARD .J. BELLEY

GEOLOGICAL SURVEY PROFESSIONAL PAPFR 101~

JUN 151987

lt!Hl.AR~

?o'J,576

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1977 ------~------

UNITED STATES DEPARTMENT OF THE INTERIOR

CECIL D, ANDRUS, Secretary

GEOLOGICAL SURVEY

V. E. McKelvey, Dirator

Library of Congress Cataloging in l'ublication Data Atwater, Brian F. Late Quaternary depositional history, Holocene sea-tevd dunt_:cs, ;md vertical crust movtem.:nt, southern San Francisco Bay, California.

(Gcological.Survcy Professional Paper 1014) Bibliography: p. 14-15. SupL of Docs. No.: I19.16:1014 L , Stratigraphic-Quaternary. 2. Sea lcvcl--Pacific coast. 3. Earth movemcnts-.·Catifornia-- San Francisco Bay. L Hcdcl, Charles W.. joint :mtllor. IL Hcl!cy, Edward J., joint author. IIL Tit!c:Late quaternary depositional history... IV. Series: United States Geological Survey Professional Paper 1014. QE696.A89 551,7'93'091641 76-608265

F01 \ale by the Supcrintfndent of Documents, U.S. Government Printing Office Washington, D,C 20402 Stock Number 024-001~02966-9 CONTENTS

Page Page Abotract l Holocene sea levels--Continued Introduction l Numerical uncertainties in sea-level data· Continued Acknowledgments l Postdepositional subsidence ...... 9 Methods 2 The Holocene transgression 9 Late Quaternary depositional history 3 Vertical movement of the Earth's crust 12 Estuarine deposits 3 Evidence and rates of subsidence . . 12 Terrestrial deposits 4 Quaternary at least 200 m below present Holocene sea levels .... 6 sea level 13 Relation of dated samples to former sea levels 6 Wisconsin thalwegs higher than the deepest Salt- deposits .. 6 Sangamon estuarine deposits 13 Intertidal or uppermost subtidal deposits 7 Relative sea-level rise greater than that expected deposits .... 7 from eustatic sea-level changes alone . . 13 Numerical uncertainties in sea-level data 8 Age of the bedrock depression containing southern Modern sample elevation ... 8 San Francisco Bay . - ...... 14 Sample elevation at time of deposition 8 Summary and conclusions 14 References cited 14

ILLUSTRATIONS

Puge PLATE L Crm;s sections showing late Quaternary sediments beneath southern San Francisco Bay, California In pocket F'IGVR:t;: 1. Map showing the modern San :Francisco Bay and adjacent continental-shelf area 2 2. Chart showing chronology for sediments under southern San Francisco Bay·- 4 3. Photographs of representative pelecypods from post-Wisconsin estuarine sediments under southern San Francisco Bay 7 4. Scannlng electron micrographs of representative foraminifers, an ostracode, , and marsh-plant seeds from post-Wisconsin estuarine sediments under southern San Francisco Bay 8 5. Chart showing comparison of stratigraphic nomenclature for sediments under southern San Francisco Bay . 9 6. Graph sho.,.,ing Holocene sea-level changes in the vicinity of southern San Francisco Bay-· I I 7. Graph showing longitudinal profiles ofburied land surfaces under southern San Francisco Bay-· 12

TABLES

P<>ge TABLE L Description and interpretation of sediments and bedrock under southern San Francisco Bay 5 2. Data on Holocene sea levels . 10 3. Evidence and inferred rates of crustal down-warping in the vicinity of southern San Francisco Bay .. 13 v

This page intentionally left blank LATE QUATERNARY DEPOSITIONAL HISTORY, HOLOCENE SEA-LEVEL CHANGES, AND VERTICAL CRUSTAL MOVEMENT, SOUTHERN SAN FRANCISCO BAY, CALIFORNIA

By llRJAl\ F. ATWATER, CHARLES W. HEDEJ., and EDWARD J. BELLEY

ABSTRACT dence of late Quaternary sea-level changes in the Sediments collected for bridge foundation studies at southern . Lawson (1894, p. 266) San Francisco Bay, Calif., record that formed during interpreted the numerous Sangamon (100,000 islands, peninsulas, and ago) and post·Wisconsin (less than small embayments 10,000 years ago) high stands of sea leveL The estuarine deposits near San Francisco (fig. 1) as of Sangamon and post-Wisconsin ages are separated by alluvial former hills, ridges, and stream valleys recently and eolian deposits and by erosional unconformities and surfaces submerged by the sea. He suggested that San Fran­ of nondeposition, features that indicate lowered base levels and cisco Bay did not exist prior to this submergence and oceanward migrations ofthe shoreline accompanying low stands that the ancestral of the sea. Estuarine drainage of the San Joaquin­ deposits of mid-Wisconsin age appear to be Sacramento absent, suggesting that sea level was not near its present height Rivers flowed through the 30,000-40,000 years ago in . to a coastline some distance west of the present one. Holocene sea-level changes are measured from the elevations Gilbert (1917, p. 16-24) cited partial submergence of and apparent 14C ages of plant remains from 13 core samples. aboriginal shell mounds and historic retreat of the Uncertainties of ±2 to ±4 min the elevations of the dated sea levels hayward edges of salt represent the sum of errors as -evidence of an in determination of (1) sample ongoing relative elevation relative to present sea level, (2) sample elevation relative sea-level rise. to sea level at the time of accumulation of the dated material, and Both Lawson and Gilbert initially attributed (3) postdepositional subsidence of the sample due to compaction of these sea-level changes to tectonic subsidence of the underlying sediments. land. Subsequently, Louderback (1941; 1951, p. 84, Sea level in the vicinity of southern San Francisco Bay rose · 86) suggested that San Francisco about 2 cm/yr from Bay was created by 9,500 to 8,000 years ago. The rate of relative a worldwide sea-level sea-level rise then declined abo~t tenfold from 8,000 to 6,000 years rise of about 100m caused by ago, and it has averaged 0.1-0_2 cm/yrfrom 6,000 years ago to the melting of late (Wisconsin) . present This submergence history indicates that the rising sea The purpose of this study is to elucidate the late entered the Golden Gate 10,000-11,000 years ago and spread Quaternary history of the site of southern San Fran­ across land areas as rapidly as 30 m/yr until 8,000 years ago. cisco Bay by dating post-Wisconsin sea levels, docu­ Subsequent shoreline changes were more gradual because of the decrease in rate of sea·level rise. menting earlier sea-level fluctuations, and measur­ Some of the sediments under southern San Francisco Bay ing vertical crustal movement. This history con­ appear to be below the level at which they initially accumulated. tributes to the understanding of the recent sedi­ The vertical crustal movement suggested by these sediments may mentary and tectonic history of the densely be summarized popu­ as follows: (1) Some Quaternary(?) sediments have lated area around southern San sustained at least 100 m of tectonic subsidence Francisco Bay. In in less than 1.5 addition, it million years (.::::: 0.07 mm/yr) relative to the likely elevation of the accounts for the foundation character­ lowest Pleistocene land surface; (2) the deepest Sangamon estu­ istics of late Quaternary sediments beneath and arine deposits subsided tectonically about 20-40 m in about 0.1 peripheral to the bay. Finally, it provides a time million years (0.2±0.1-0.4±0.1 mm/yr) :relative to the assumed perspective on the principal geographic features of initial elevations of the thalwegs buried by these sediments; and the San Francisco Bay area. (3) Holocene salt-marsh deposits have undergone about 5 m of tectonic and possibly isostatic subsidence in about 6,000 years (0.8±.0.7 mm/yr) relative to elevations which might be expected ACKr\0\YLEDGMENTS from eustatic sea-level changes alone. Most of the core samples on which this study is Ii\'TRODUCT!ON based were collected and logged by the California Division of Bay Toll Crossings. State engineers and Geologists long ago recognized geomorphic evi- geologists who participated in bridge foundation CALIFORNIA 2 DEPOSITIONAL HISTORY, SEA-LEVEL CHANGES, AND CHUSTAL MOVKMEN1',

F araPon

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5 iO 20 MILCS f----r·-'-,-- ___ .L·:-·--'~----,-' o s , :J 15 ·2u 2!: JO v, I 1_Qi\::ETE 1=;s

AJiJ used in this :~report, oouthem San Franci!WO FlouRE 1.-Modem San F-caucisco &y and adjacent cordinental-shelf axea. 100-m isobath approximate!! the £~horeline refers to the pa:rt of the bay that lies south of the latitude of the Golden Gate, The position 15,000 .s ago.

San Francisco Bay, AH of the boreholes penetrated studies S. K. Atkinson, T. firm terrestrial sediments beneath Holocene estu­ Barnwell, C. C. Bohannon, F. R. Carraro, T. arine deposits, and som.e extended more than 100 m W. Driskill, G. Emerson, T. :F'ox, Hernon, S. below sea leveL Hunt, S. Kelsey, M. C. Knickelbein, B. McCreary, J. Borehole information assembled by Bay Toll Marzotto, M. Matsumoto, D. Morgan, M. Oxen· Crossings consists of samples, hand speci- dine, J. W. Rolston, S. Samuelson, Schott, men cross sections, and M. Schwartz, P. D. Trask, Venskus, J. the results of -mechanics tests. The samples, Wright. Fossil identifications for this report were 20-50 percent of the sediments, by W. 0. (mollusks J. :representing in tubes 5-8 em in diameter. Hedel (diatoms), R. E. A:mal were collected C. W. in the tubes, whereas (foraminifers), P. Valentine F. Atwater placed in glass jars. Many "''·'""'"''"''· Photographs of samples were subsequently Kenji Sakamoto, tests. About 5,000 of been donated LATE QUATERNARY DEPOSITIONAL HISTORY 3 replacement of framboidal pyrite by limonite, and cisco Bay contain a approximately 1 m.y. (mil­ color changes from gray to olive and brown. In lion years) old (table 1; Sarna-Wojcicki, 1976)andare addition, calcareous fossils may have dissolved in consequently of age. This earliest these sediments because of oxidation of pyrite or estuary probably connected with the Pacific Ocean other reactions that increase the concentration of via a shallow marine embayment at the site south of hydrogen ions. However, the common absence or San Francisco in which sediments of the Merced decomposition of calcareous fossils in desiccated Formation were deposited. These sediments were samples of Holocene estuarine deposits (such as in later deformed and uplifted. Freshwater drained to borehole 11, section A-A', pl. 1) is probably due to this estuary from the Great Valley, as evidenped by dissolution prior to coring. This natural dissolution the presence of Great Valley in a coeval part is evidenced by the absence of calcareous fossils in of the Merced Formation (Hall, 1966)_ many of the fresh core samples we have collected The youngest known estuarine deposits of Pleis­ from Holocene estuarine . tocene age under southern San Francisco Bay were Sediments from 18 Bay Toll Crossings boreholes probably produced by Sangamon high stands of the were examined for this study. Paleoecological inter­ sea. Although no unconformities have been recog­ pretations are based in part on color, texture, authi­ nized within the Sangamon estuarine deposits, the genic mineralogy, bulk density or moisture content, record of sea levels at New Guinea (fig. 2; Chappell, and penetration resistance of sediments, and on 1974, p. 568) suggests that the Sangamon estuary megascopic plant and animal fossils. In addition, may have expanded and contracted several times in splits of about 175 samples from these boreholes were response to sea-level changes 70,000-130,000 years washed through sieves with a mesh opening of 0.063 ago. The maximum areal extent of the Sangamon mm for separation of foraminifers, ostracodes, dia­ estuary was probably at least as great as that of the toms, seeds, and microscopic authigenic minerals. post-Wisconsin estuary because, despite postdeposi­ Nearly all of these washed samples come from tional , Sangamon estuarine deposits under­ sediments less than 60 m below modern sea level, lie most of the area of the post-Wisconsin estuarine and most come from Holocene estuarine deposits. deposits (pl. l)_ Finally, paleoecological interpretations were extrap­ Data from the continental shelf of the olated to additional Bay Toll Crossings boreholes United States suggest that sea level approached its using the hand-specimen descriptions and physical present height 30,000-40,000 years ago (middle properties recorded by the engineers. Wisconsin) (Milliman and Emery, 1968). Estuarine Carbon-14 dates (pl. 1) were prepared with pro­ sediments of this age appear to be absent under portional gas counting techniques by Isotopes, Inc. southern San Francisco Bay_ Presurrtably, if the Because of the small size of samples and the ten­ volume of estuarine deposits that woul

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sediments under southe~7i San FTI:mci.r;;~o Bay s.ncl their con·eiatirm ""-ith oodiment<~ of r£J.ari.ne terrace ._.~.,.,,,_., .. ~ .., l!'Jidegprea.d :i.n California. Correlation!! are where l.ineg m:'e dashed. Vertical scale of right gide of m:tJ.in ;,.tratigraphie cdun:m it~ approximawly te thickn,=.e!J of umts nea.r borehole 2 (map, pl. 1). Wavy H.nei> lnd:kate zig-zag line!! indicate interfinged.ng of tirrw-equivalent. unit14. Gladal chronology fm· mid·continentsJ and boundaries after Bm·ggren and VanCouveri.ng (1974, p, 144); glacial chronology fm Siena Nevada after Wahrhaftig and Birman (1965, p. :J08, 331); paleoclimatic cycles from. Broecli<·r and VanDonk (1970, p. 181); age l'ang,, of marine terrace fro:m compilation by Birkeland (1972, p. 443).Cm:relation of tuff in type Formation after Sarna-Wojcicki 11976). Radiomr•tric a£;es of this tuff range from OA tv 2.6 m.y., but the most amum:i l.IJ m.y. (A. Sarna-Wo_icic:ki, writkn commt~n., l.97i); see table 2), LATE QUATERNARY DEPOSITIONAL HISTORY 5 TABLE l.~Description and interpretation of sediments and bedrock under southern San Francisco Bay

Environment Unit Lithology Stratigraphy Age of deposition Correlations

~~ ...... ··---· -~···-·····~ ~~~~~ Estuarine Clny nnd silty day with wre Cover stream Pre8ently forming. Oldest Ca. 9,500 yearE ago: Bmall Equivalent to bay deposits sand and graveL Dark gray valleys, dated deposits approxi· brackish estuary extending mud of Trask and (Holocene; {5Y 3/0.;') to 5Y 4/l) fresh, allu~-ial fans, matdy 9,300 years ago; no further south than IW!ston (1951) post­ dark grayish brown (2.5Y 4/2) and sand dunt>S oldest deposits near HunWrs Point. and to normally Wisconsin). and olive gray {5Y 4/2) in of latest Golden Gate, if pre· Ca. 9.500-7,000 years ago: consolidated OJddil.ed samples. Pleistocene served, pwhably 10,000- rapidly enlarging member of Commonly contain framboidai (Wisconsin) and ll,OOO years ago. estuary, progressively younger bay mud pyrite. Slight to strong early Holocene less diluted by fresh of Treasher {1963, H2S

Table l.-Description and interpretation of sediments and bedrock under San Francisco Ba}'·-··Continued

Environment Unit Lithology Stn1tigraphy Age of deposition Correlations

Estuarine Commonly contain eshmrine diu­ Represent the youngest deposits (late toms. pelecypodR, and foraminifers major PldstfK:ene high Pleistnc<•ne; similar to those in Holocene sea-level Rtand, as shown Sangamon}~ deposits. [.<)cally include peaty by their great extent and Continued clays near contact with older tern:s· thickness and by the trial deposits. apparent absence of over· lying pre-Holocene estu· arinc deposits. Therefore correlated with the Sungamon Interglaciation and regarded as 7.5,000- 12..1,000 years old. Terrestrial and Clay, silt, sand, and gravel. Unconformably Oldest deposita probably Pli­ B

~dr~ck­ Predominantly clastic sedimen.tB.ry Late Mesowic Francis- The.~e rocks fnnn1'd in (MesoZoic and mcks and ii;neoi:i.s rocks, in part can rocks and s-erpentinite various ancient nwnnc. Tii£1~-ryt-. altered by low-temperature form the knoy,

~--- ~~~---·~-~- ····-~-~~~- Francisco by prevailing westerly winds (Cooper, HOLOCENE SEA LEVELS 1967, p. 48-52). '-. c •• ·• The lowest base l()v:el_ .at'the Golden Gate during RELATIO!> OF DATED SA)IPLES TO FOR)!ER SEA LEVELS Wisconsin time wa"'s' probably about ?o m below Holocene sea levels are typically dated by the present sea level. This base !~vel is suggested by radiocarbon ages of plant or animal remains that bedrock sills located abou(() km.<:Jast and northeast initially accumulated near sea level. The roots of of the Golden Gate, the lowest of which is 65 m belo.w · salt-marsh plants are the principal materials dated present sea level (Carlson and McCulloch, 1910). for this study and represent upper intertidal condi­ Consequently, assuming thatsea level during the tions. Adqitional control on the age of former sea late Wisconsin glacial maximum stood about 100m levels is given by dated plant remains from intertidal below present sea level (Flint, 1971, p. 322), the late or uppermost subtidal environments and from pre­ Wisconsin shoreline must have been located west of dominantly freshwater marsh environments at or the Golden Gate on what is now the continental shelf above the highest tides (table 2). (fig. 1). Plant fossils dated at 23,600 years old and found S:\LT-:..IARSH DEPOSITS 10 km southeast of Menlo Park (map, pl. 1) about8m With the possible exception of eelgrass (Zostera), below present sea level show a relative abundance of an which is very rare or absent in San cedar and Douglas fir and a relative scarcity of oak Francisco Bay today, plants which inhabit salt and redwood, th)ls suggesting a cooler, wetter cli­ marshes are the only ones that can produce peaty mate than today (David P. Adam, oral commun., estuarine muds composed largely of roots in growth 1973). Associated animal fossils indicate that positions. Therefore the principal feature of salt­ vertebrates, including camels, marsh deposits that differentiates them from other bison, , sloths, and , roamed the estuarine sediments is the a'l:nmdance of roots in late Wisconsin valley now occupied by southern San growth positions. Additional diagnostic character· Francisco Bay (Edward J. Helley and Kenneth R istics of salt-marsh deposits include a typical abun­ Lajoie, unpub. data). dance of arenaceous foraminifers, a scarcity or H()L\}CE~JE SE.A_ LE\lE·Ls 7

c

B

G ~,._____ .;..! southm·n San Francisco Bay. Scale bat FIG1JRE pelecypods from e11tuarine sedinwnts under of Clinocardium cf. C nuttalli :represents 1 em. A, lurida B, sp. to a .Macorna C, Clinocardium nuttalli (Conrad); D.. E, !dacoma nasuta (Conrad); fi~ balthica (Linne); G, My til us edulis f!·agme.nt.

re· DEPOSITIO:\IAL Hi:STO:liY, SE.i\.-Ui.:VEL CHA.NGES, }I,ND CRUSTAL M(}\TJ<:MENT, Cl\UFORNIA

FIGUR.E ~t-·Ser-;.;,:aniT1g' n1ic1·og-rapJ:'tS oi!for~ilni:n.if(·T~'I (1~.~·11f£)} :-1r~ ostrac,xl~? (F;, diH1.:oms (G-(J), and ffifj:rshvplant needt::t (_P, Q) frorn post-.1l'V'iBconain e.3tufii.rin.e ~tdirnentb UA-:tdr.:.~r· Bf:Jnthe-rn SaJ1 F·ean.cisco Bay. Scale bar represents 0.1 rnm. il, Elphidium incertu.nL obscurut.•t (Vi,~'illian~son) v·ar cbscuru.rn '\/oloshino'lf/R_; BJ Elph:idiuJn gunt:eri Col~~; C, A.nt?nort..ia becca.rii (Linn€); D~ Ji:lphidiella hannai (Cunhman a.r_~_d G:ra.nt/; 1!:~. TrochJJ..rn ;-r::.ina in/lata. (}/[ont.a~:ru); 17 ~ Cyiheror.--:.ol~v.;lu~t sp.; c;y r1ctin.o]Jtychus splendens (Shad bolt) :Ralfs; _h.Jr, C1oscirtodiacus sp_ (not~ fra.1Ythoida1 p:y-ritr~· in frugtule); l! .Aulacodiscns kittoni i\rnott; f.l, _Btddulphia sp.; J( Isthrrua r;_eruosa I._,; { 1anr_pyludiscus sp.; lvf:.> c~yrnbeila. cf. (7. ·28pera O~:atrenbe:rg') C:leve; lv"'"~ 8urirella sp.; OJ Surirella? sp.; P_. 8alicornia gp.. ; ({. Sc1:rpu~~:? H:p. HOLOCENE SEA LEVELS 9

fhts report 1 Tr1-~ --- "]II 1! ~-- .. ·--·----~ --~~~~~-~;~~-~ ±L5 m. Freshwater marsh deposits provide only wv Estuarin'-' norn·lally i upper limits on the I depostts deposits I I Bay mud consol- 1 elevation of sea level at the time of I (Holocene) (Holocene) , ! iclated 1 their accumulation (table :1). 1------~ j ~./'\._/'-1--r':"mbe> I I'OSTIHTOSITIO:\.-\L St 'BS!Di.·::'\CE (.>)

I Postdepositional subsidence (table 2) is likely >/''Alluvial deposits /tt'>~~~~~-I (I 1 I M . I I ·~a_ 1 < (late Pleistoceno;;· s ate I I erntt I m where sediment overburden has placed a load on H I ) Pletstocenet 1 Sand I I ~ ant o ocene and ~ 1 ! -0 ;;>I I I I c compressible sediments beneath the elated samples. Holo 1 1 (A Errors in thickness and consolidation of the com­ ~/• ----.."c"_")_. ~~~~~- -~rv, pressible sediments lead to uncertainties as large as ±2.5 m in the subsidence estimates. ~~~:(~:! ~:::~---~- ~--- ~~Focme

TABLE 2.-Data on Holocene sea levels [All linear m€asurement.s in meters·, ace plate l for location of boreholes]

Postdepoaitional subsidence (s) of dated sample caused by compaction of undedying sediments T ~ thickness of compressible sediments S" settlement E:Jev(·ltion of Age and mean sea analytical levd Sample at elevation tin>e of lH> tainty in Sample Pleistocene cumulation "C years at time of Late elevation Pleistocene deposits, of dated before depoai.tion Holocene and Holoc{'ne relative groundwater material 1950 A.D. relative estuarine terrestrial to withdruwal relative to (half life modern Principnl tn former deposits deposits (Poland, 1971) modem 00 Bon"· mean sea dated l~nvirunrnent

:.!5 -7.9.±0.5 Roots of Abundant rooW, prob- l.Q.:;l.O 2.0 0.5-3.0 0.0-1.5 0.0-0.4 0.3-0.7 Sl'l]t. ably in growth 2.4±.1.6 -6.5±3.1 3,,'160.t.l05 marsh positions; Trocham- plant~>. mina inflata (Fa); CampylodiscWJ (Dp). Fragments Abundant plant frag· -0.5;,1.5 O.l-1.5 0 0 of IHllt· ments, probably 0 0.8_!0.7 marsh detrital, and Sa/i- plants. cornia seeds (A, s); E/phidium spp. (Fcl; O.s·trea lurida (P,s); shells broken and probably detrital ~9.0.t0.:3 Roots of Abundant roots, prob· l.O.::t:U) 0.0-2.0 0.0-3.0 2.0-3.0 0.0-0.8 0.:3-0.7 ,salt· ubly in growth 2.4!.2.1 5,745!_185 marsh positions; 1'rocham­ plants. mina inflata (Fa); framboidal pyrite. 32 -lL4:0.5 ---.. --do·-· ···-Abundant roots, prob­ LO;tl.O 0.0-l.O 0.0-2.0 0.0-l.O 0.0-0.:3 o.:J-o.? ably in growth L6..t1.3 5,S45.tl00 positions; Trocham­ mirw inflata (Fa); Campylodiscus {Dp). 33 -10.8±.0.5 -----do .. ---··-·do--- l.O:cl.O 0.0-1.0 0.0-2.0 2J)-3.0 0.0-0.8 0.,'3-0.7 LS!:l.fl -9.9;:3.1 6,200_:!:320 12 -ll.8i.0.5 ······do---· Abundant root.sln 0.7.±0.7 0 0 0 0 0 0 growth positions: -125:;1.2 6,485;:_110 Trochammirw inflata (Fa): Cymbella {Dp). 21 -9.2.±_0.:1 ······do··--- Abundant roots, O.S.!:_0.9 prob- 0.5--2.5 0.2-5.0 0 0 () 2.6.t2.4 ably in growth -7.5::3.6 6.855:cll5 poslthms; Campylodiscas iDp). ll -24.6.:!:0.7 ------do---·· Abundant roots, prob- 0.7.:.0.7 1.5--2.5 0.6-5.0 2.0-3.0 0.0-0.8 0 :1.2t2.6 -22,1!:1-.0 ably in growth 8,2:30.~:13.'5 positions; Campylodiscus (Dp); frarnboidal pyrite. 10·' -2LO;tl.O -----do .. Abundant roots, prob- 0.7.;;.0.7 0.0-2.0 0.0-4.0 0.0-2.0 0.0-0 .•'5 0 2.2~2.2 -l9.5;t:l.9 ably in growth 8,29E>t.l:-\5 positions; Trocham· mina sp. (Fa); Campylodi.~cus (Dp), Hyalodiscus (De). 16 -18.7:t0.3 """'··do--· Abundant roots, prob· 0.9.::t:0.9 0.0-1.0 0.0-2.0 2.0-3.0 0.0-0.8 0 4:t)A .. 11\.2!2.6 ably in growth 8,~'l65tl3~l positions; Campy/odiscus (Dp). 3" -32.5.t.l.O Remains of Abundant roots in Probably 0 0 0-2 0-2 0 l.!;l Below 8,88.5±145 fresh· or growth positions, above brackiah· and abundant highest -31.5!2.0 wat<:>r Scirpus? seeds (A, n, tides. marsh rare lirnonitized plants framboidal pyrite. -3fJ.5:t0.5 Chunks of Abundant detrital O.O;tL5 0 0 0 0 wood. wood; Ammonia 0 0 -39.5;:2.0 9,255:.::.110 beccarii, Elphidium sp. (Fe); Cythero- morpha sp. (0); Cocconeis, Surirel/a, Cymbclla (Dp); Valvata (G, f), Psidium (G, f); Thoecamoebina (fresh- and brackish- water protozoans); mosquito larvae (R E. Amal, written comrnun,, 1974). HOLOCENE SEA LEVELS 11

TABLE 2.-Data on Holocene sea levels-Continued

Poatdepoaitional subsidence (8) of dated sample caused by compaction of underlying sediments T" thickness of compress! ble aedJmen ta S ~ settlement Elevation of Age and ·- mean sea anal).i:ical level at uncer­ Sample time of ac­ tainty in elevation Pleistocene cumulation "C years Sample at time of Late Pleistocene deposits, ofdatd elevation before deposition Holocene and Holocene groundwater material 1950 relatlve A.D. relative estuarine terrestrial v.ithdrawal relative to (half life Principal to modern to former deposits deposits (Poland, 1971) modern "5,5<38 Bore- mean sea Environmental d"ted mean sea mean sea years) hole No. level (h) material indicators 1 level (h F T 0 s T s 8 Total s level (HJ (see pl. 1)

------· ·--·--··---·-,----- .~-- --- 2 -37.5.!;.0.5 Remains of Predominance of Above 0 0 2-6 0-4 0 2;t2 Below 9,280c:l20 fresh-water plant remains over highest -3G.5±2.5 marsh plants inorganic detritus; tides, abundant Scirpus? seeds (A, f).

'Explanation of symbols; A~marsh angiosperm Dp"' , pennate Fa foraminifer, arenaceoua; typically livea in salt marshea De" diatom, centric Fe "'foraminifer, calcareous; typically liv{!s in lower intertidal P = pelecypod and subtidal environment!J G =gastropod 0 = ostracode s ·~salinity range predominantly ;wltwater and brackish water f"' salinity range predominantly brackish water and freshwater See figures 3 and 4 for photographs of some of these organisms, and plate 1 for additional ecological information. ''Estimates based on analogy with vertical distribution of seed plants, diatoms, and foraminiferstHinde, 1954; Amal and others, 1977; Phleger, H170, p. 532-533)in mo-l"""'"''""'""' fur '!Borehole not shown on cross sections (pl. 1). Mean amplitude sea-level oscillations, so a smoothed curve sea was visually fitted to the data points (fig. 6). This level curve displays a more than tenfold decrease in slope between 8,000 and 6,000 years ago. On the average, sea level in the vicinity of southern San Francisco -10 Bay rose about 2 cm/yrfrom 9,500 to 8,000 years ago, but it w has risen only 0.1-0.2 cm/yr from 6,000 years ~ w ago to the present. A similar change in rate appears f- w ~20 in sea-level records from other parts of the world (for I example, Milliman and Emery, 1968) and probably "~ E,XPLANATION! z -- So<.1thern San Francisco ~ay coincides with the disappearance of the large Wis­ 0 f- Probable range of erro'r 'ln age consin ice sheets (Bloom, 1971, p. 368). <:[ ··30 > <.lnd elevation of formet sea level Extrapolation of the sea-level curve to the pre­ w ~I] {table 2). Arrow indica{tes former ~ sumed w sea level below some doint late Wisconsin base level, located about 65-70· in rectangle 1 m below modern sea level at the Golden Gate (A, fig...... Micronesia I 7), indicates that the rising sea entered the Golden 40 ' Gate 10,000-11,000 years ago. Driven by the sea-level I rise of several centimeters per year, an estuary then ' spread rapidly, advancing about 30 m/yr along I the j___ _j___ -50 , __ _... ..1 ...... ~ ... -.-1. course of the trunk stream draining the site of 0 2 3 4 5 t 7 8 9 10 southern San Francisco Bay and reaching the vicin­ AGE, IN THOUSANDS OF YEARS BEFORE PRESENT ity of Menlo Park by 8,000 ( G, fig. 7) years ago (fig. 7). Subsequent shoreline changes have been more grad­ FIGURE 6.-Holocene sea·levelchangesin the vicinity of southern ual because of the decrease in rate of sea-level rise. San Francisco Bay. The curve for Micronesia, shown for A change from predominantly fresh- and comparison, approximates Holocene eustatic sea·level brackish-water diatoms in estuarine sediments changes according to Bloom (1970, p. 1901). about 8,500-9,300 years old to predominantly marine average water salinities by permitting larger propor­ diatom assemblages in younger sediments (bore­ tions of saltwater to enter the estuary. holes 4, 5, 6, section A-A', pl. 1) indicates increasing Changing rates of sea-level rise largely control salinity. This increase was probably caused by the the stratigraphic distribution of salt-marsh deposits. rapid early growth of the estuary. Assuming a nearly The sea-level rise of several centimeters per year constant long term inflow of freshwater, the large probably exceeded most local rates, so increases in water volume accompanying this tidal marshes before 8,000 years ago were scarce and growth should have resulted in substantially greater small and, moreover, were ultimately submerged by 12 DEPOSITIONAL HISTORY, SEA-LEVEL CHANGES, AND CRUSTAL MOVEMENT, CALIFORNIA

121° Northwest Southeast

Mean 21 Mean sea 43 sea level 65 level 7 8 -50 -20 Approximate course of (fJ drainage of San Joaquin -100 a: 1- and Sacramento Rivers w w during late Wisconsin 1- w u.. time ~ -40 by post-Wisconsin estuarine deposits -150 ~ 5 10 MILES ~ z" z 0 5 10 15 KILOMETERS 0 1- 1- <( <( -60 -200 > > w w .J .J Land surface buried w w t by Sangamon N estuarine deposits 250 -80

•Hayward t c -300 1 A 8 D E F G -100 10 0 70 80 DISTANCE FROM GOLDEN GATE, IN Kl LOMETERS •Fremont EXPLANATION

Menlo Park• Buried thalwegs Buried bedrock sills (Carlson and 0 Covered with post-Wisconsin estu­ McCullockl, 1970) arine deposits (pl. 1) • Across line of profile 0 Covered with sediments, probably !:> Not across line of profile of post-Wisconsin age, recogniz­ 8 Radiocarbon age of Holocene sea ed in seismic reflection profiles level in 103 years before pres­ (Carl,son and others, 1970, ent (fig. 6) p. 105) 0 Covered with Sangamon estuarine deposits; elevations estimated from unpublished borehole logs and cross sections by Calif. Div. of Bay Toll Crossings, 1948-71

FIGURE 7.-Longitudinal profiles of buried land surfaces under southern San Francisco Bay. Profiles are based primarily on the elevations of buried thalwegs (lines of maximum valley depth) at points A, E, F, and G. PointE is locate~ between boreholes 4 and 5 (A-A', pl. 1), point F, approximately at borehole 17 (B-B', pl. 1), and pointG, between boreholes 32 and 34 (C-C', pl. !).The upper profile is also based on the elevations of bedrock sills (points A, B, and D), which indicate the deepest possible base levels during late Wisconsin time. All vertical bars show approximate uncertainties-in elevations ofthalwegs and sins. We speculate that the late Wisconsin trunk stream draining the site of southern San Francisco Bay met the drainage of the San Joaquin-Sacramento Rivers north and east of Angel Island because the bedrock sill between Angel Island and Tiburon Peninsula (B) is about 15m lower than the sill between San Francisco and Angel Island (C); therefore the profile of the land surface buried by post-Wisconsin estuarine deposits loops north of Angel Island. The intersection of Holocene sea levels with this profile shows the rapid lo~gitudinal growth of the post-Wisconsin estuary from 10,000 to 8,000 years ago and the subsequent decline in the rate of longitudinal growth. the rising sea. Later, the declining rate of sea-level of southern San Francisco Bay was first reported by rise was approached and finally surpassed by the Lawson (1914, p, 3), who observed that late rate of sediq1ent accumulation in much of the estu­ structural features bound the valley that is partly ary, permitting progradation of and salt flooded by the bay. Subsequently, Louderback (1951, marshes. Most of the hayward growth of marshes p. 83) proposed that the bedrock surface under this has occurred during the past several thousand years, valley had been downwarped during Quaternary as evidenced by the lower intertidal and subtidal time. Both men asserted that the valley containing deposits which typically lie no more than a few southern San Francisco Bay had been shaped not meters below mean sea level beneath the historic salt only by running water but also by vertical tectonic marshes (boreholes 13, 26, 27, 29, 30, 32, 38, 39, movement of the Earth's crust. sections B-B' and C-C', pL 1). Several additional lines of evidence suggest that VERTICAL MOVEMENT OF THE EARTH'S CRUST subsidence of the valley floor has taken place .and permit rough estimates of the rates of subsidence EVIDENCE AND RATES OF SUBSIDENCE (table 3): (1) Quaternary(?) sediments are situated at Evidence of vertical crustal movement at the site least 200 m below present sea level, (2) Wisconsin

• VERTICAL MOVEMENT OF THE EARTH'S CRUST

TABLE :3.-Evidence and inferred rates of crustal downu;arpinp sediments under most of southern San Francisco in the of southern San Francisco Bay Bay (pL 1), The Sang am on deposits persisted in such Rat<' Evidentr: (mm·'yr) How measured Time period Orig-in quantity because Wisconsin trunk streatns were unable to cut through them: the thal wegs (lines of quatt>rnc;ryi?) sedi­ '>o.1r; Ekvatwn difference Ui m.y Tectnnk menls situated at betwl'l!!l deepe~t ((juaternary) maximum valley depth) of Wisconsin trunk stream least 2(){} m lwkw ()iwtemary sedi- present sea level. ments and level at are located at least 15 m above the deepest San· v;hkh thev were gam on estuarine deposits. Assuming probably deposited that the trunk stream draining the bay basin Wisc-onsin thalweg '0.2:.\U Diff('renccs in (•leva- lU nLy. Do during the low situated higher '0.-L:O.l tion between thf.' (late Plcislo· stand of sea level before the first major marine thun t.lw deepest '0.4;JL l thulwegs covered cene: Sanganwn SG.ngamon cstu v,clth Sanp:mmn and Wi~consinl. transgression of Sangamon age was similar in arine deposits. and pa· ern San Franciseo isostatic. le;•cl chanw~s alone 1:\Hy with those at Wisconsin thalwegs. Micronesia, an an'a of presumed crustal The differences in elevation between the ancient stability (fig. 5). land surfaces covered with Sangamon and post· 'Applies to must of sit\• of southern Ban Francisco Bay below latit.udl' of Hayward. Wisconsin estuarine deposits should approximate 'Applies to site b;,tween boreholes ·land ~l (A-A', pi. lJ. •Applies tn site near borehole 17 (B-B', pl. ll. the magnitude of this tectonic subsidence during 'Applies tn site betWN'l'l bon' holes 32 and a4 {C-C', pL ll. Sangamon and Wisconsin time, a period of about 100,000 years. Assuming that the initial longitudinal profiles of these land surfaces were similar in gradi­ ent and elevation, the present differences in eleva· trunk streams were unable to cut through the deepest tion between the profiles (fig. 7) indicate the follow· Sangamon estuarine deposits, and (3) the late Holo­ ing average rates of tectonic subsidence : 0.2±0.1 cene rise in sea level exceeds what might be expected mm/yr, between San Francisco and Oakland; from eustatic sea·l<;vel changes alone. 0.4+0.1 mm/yr, between San Mateo and Hayward Ql 1:\TF.R:\,\RY SEDI:\!E:\TS AT LEAST 200M and between Menlo Park and Fremont. BELO\\. PRESE:\'T Sb\ LE\"EL RELATIVE SE.-\-LF\'EL RISE GRL:\TER THA\: THAT Sediments of Quaternary age may extend at EXPECTED FRO~! EUSTATIC SEA-LEVEL CI-L-1.:\"CES ALO:\E least 200 m below present sea level under much of The record of post· Wisconsin sea levels at south southern San Francisco Bay, particularly between ern San Francisco Bay can be used as a datum to San Mateo and Hayward and between Menlo Park determine vertical crustal movement by comparison and Fremont (Finlayson and others, 1967, pL 5; with sea-level data from areas of presumed crustal Meade, 1967, p, 40-41), Assuming that they were stability, Sea level has risen more rapidly in the deposited during the past L5 million years and vicinity of southern San Francisco Bay than in within 100 m of present sea level, these sediments Micronesia by 0.8±0, 7 mm/yr during the past 6,000 probably have been lowered by tectonic subsidence years (fig. 6), Assuming that the relative sea-level of at least 0.07 mm/yr, rise in Micronesia approximates purely eustatic Conceivably, an extremely low stand of sea level changes (Bloom, 1970, p, 1901), the more rapid could have allowed streams draining the bay basin submergence at the site of southern San Francisco to grade to a base level200 m below present sea level, Bay represents downward crustal movement. thereby allowing Quaternary sediments to accumu­ Tectonic subsidence is probably the principal late at lower elevations than we assume, However, component of this crustal movement. Given the such a stand of the sea during Pleistocene time is range of our uncertainties, the rates of tectonic sub· unlikely because it is lower than what might be sidence during the last 100,000 years of Pleistocene expected from ice volumes during Pleistocene glacial time may be considered equivalent to the rate oflate maxima (Flint, 1971, p, 84) or from the overall rise of Holocene crustal down warping (table 3).lfthe actual sea level independent of glacioeustatic fluctuations rate of Holocene downwarping is as high as 1 (Vasil'kovskiy, 1973, p. 857). mm/yr, however, then tectonic subsidence has accel· erated or has been augmented by isostatic down· WISCOASI:\ TIL\LWFGS HIGIIEK Til:\:\ THE warping of the continental margin. DEEPEST SA:\C,\;\iO;"\" ESTCARL'\E DEPOSITS The likelihood of isostatic adjustment to post-Wisconsin seawater The volume of Sangamon estuarine deposits loads has been established for the Atlantic coast of remaining after Wisconsin erosion appears to be the United States by Bloom (1967b), but at present close to the volume of post-Wisconsin estuarine we cannot differentiate its effects from those of tee- 14 DEPOSITIONAL HISTORY, SEA-LEVEL CHANGES, AND CRUSTAL MOVEMENT, CALIFORNIA tonic subsidence in the vicinity of southern San mm/yrfrom 6,000 years Francisco Bay. ago to tbe present(figs. 6, 7). 4. Some· of the sediments under southern San ACE OF THE BEDROCK DEPRESSIO:'\ Francisco Bay appear to be situated below the level CO."\T AI:'\Il'\"G SOVTHER?\ .SAl'\ FRA:"\CISCO IL\ Y at which they initially accumulated. The vertical Rates of tectonic subsidence can be extrapolated crustal movement suggested by. these sediments to estimate the age of the structural trough that (table 3) may be summarized as follows: (a) Some contains southern San Francisco Bay. For example, Quaternary(?) sediments have tectonically subsided the top of Mesozoic bedrock under southern San at least 0.07 mm/yr relative to the lowest likely Francisco Bay is located as much as 200 m below Pleistocene land surface; (b) the deepest Sangamon present sea level near Menlo Park (R. M. Hazelwood, estuarine deposits have subsided tectonically oral commun., 1975). Assuming that streams flowing 0.2-0.4±0.1 mm/yr relative to the assumed initial in this area cut no deeper than 100m below present elevations ofthethalwegs buried by these sediments; sea level during a Pleistocene glaciation, this bed· and (c) Holocene salt-marsh deposits have under· rock surface has undergone at least 100m of tectonic gone about 0.8±0.7 mm/yr_of tectonic and possibly subsidence. Extrapolation of local tectonic subsid­ isostatic subsidence relative to elevations that might ence rates, which averaged 0.3-0.5 mm/yr during be expected from eustatic sea-level changes alone. Sangamon and Wisconsin time, indicates that this 5. Rates of tectonic subsidence and the depth to subsidence began as recently as 0.2-0.3 m.y. ago. Mesozoic bedrock indicate that the structural depres· The structural trough appears to be older in some sion containing southern San Francisco Bay may be other areas. The depth to bedrock along the east as young as 0.2-0.3 m.y. in some areas. shore of southern San Francisco Bay near Hayward, for instance, probably exceeds 300 m (R. M. Hazel­ REFERENCES CITF.D wood, oral commun., 1975). At subsidence rates of Arnal, R. E., Quinterno, P. J., Conomos, T. J., and Gram, K, 1977, 0.3-0.5 mm/yr, this depth suggests an age of at least Trends in thedistribution of recent Foraminifera in San Fran­ 0.4-0. 7 m.y. Furthermore, a tuff about 1 m.y. old is cisco Bay: Springer-Verlack, Bandy memorial volume in found in estuarine sediments micropaleontology (in press). 87 m below present sea Atwater, B. F., and level in borehole Hedel, C. W., 1976, Distribution of tidal-marsh 2 (table 1). This tuff indicates that a plants with respect to elevation structural and water salinity in the trough may have been located just east of natural tidal marshes of the northern San Francisco Bay the site of San Francisco during early Pleistocene. estuary, California: U.S, Geol. Survey, open-file report 76- 389, 41 p. SUMMARY AND CONCLUSIONS Bastin, E. S., and Davis, C. A., 1909, Peat deposits of Maine: 1. Two units of estuarine deposits are recognized U.S. Geol. Survey BulL 376, 127 p. in sediments less Berggren, W. A., and VanCouvering, J. A, 1975, The Late Neo· than 60 m below present sea level at gene: , the Palaeoclimatology, Palaeoecology, site of southern San Francisco Bay (table 1; pl. 1). v. 16, p. 1-216. These deposits were produced by Sangamon and Birkeland, P. W., 1972, Late Quaternary eustatic sea-level changes post· Wisconsin high stands of sea level (fig. 2). along the Malibu Coast, County, California: Estuarine sediments of middle Wisconsin age appear Jour. Geology, v. 80, p. 432-448. Bloom, A L., 1964, Peat aceumulation to be absent, suggesting that local sea level was not and compaction in a Con­ necticut coastal marsh: Jour. Sed. Petrology, v. 34, no. 3, near its present height 30,000-40,000 years ago. p. 599-603. 2. The estuarine deposits of Sangamon and post· --1967a, Coastal of Connecticut; Final RepL, Wisconsin age are separated by alluvial and eolian Geography Br., Office Naval Research, contract NORN-401 deposits and by erosional unconformities and sur­ (45), 72 p. faces of nondeposition (pl.l). --1967b, Pleistocene shorelines, a new test of isostasy: Geol. These features indicate Soc. America lowered base levels Bull., v. 78, p. 1477-1494. and oceanward migrations ofthe --1970, Paludal stratigraphy of shoreline 'l'ruk, Ponape, and Kusaie, accompanying low stands of the sea. Eastern Caroline Islands: Geol. Soc. America Bull., v. 81, 3. The late Wisconsin shoreline was situated p. 1895-1904. --1971, some distance west of the site of San Francisco (fig. Glacial-eustatic and isostatic controls of sea level since the last glaciation, 1). The rising post-Wisconsin sea entered the in Turekian, K. K, ed., The late Golden Cenozoic glacial ages: Yale Univ. Gate 10,000-11,000 years ago. Press, p. 355-379. As sea level rose about Bonilla, M. G., 1959, Geological observations in 2 cm/yr, an the epicentral estuary spread across adjacent land area of the San Francisco earthquake of March, 1957: Cali­ areas as rapidly as 30 m/yr until about 8,000 years fornia Div. Mines Spec. Rept. 57, p. 25-37. ago. Subsequent inundation has been more gradual --1965, Geologic map of the San Francisco south quad­ because the rate of sea rangle, California: U.S. Geol. Survey open-file map, scale -level rise has declined at least 1:20,000. tenfold since 8,000 years ago, averaging only 0.1-0.2 Broecker, W. S., and VanDonk, ,J., 1970, Insolation changes, ice llEFEHENCES CITED 15

volumes and the ~-~o record in deep·seacores: Rev. Geophysics ---1914, Geology of the San Francisco District: U.S. GeoL and Space Physics, v. 8, p. 169-198. Survey United States, GeoL Atlas, 24 p. California Division of Bay Toll Crossings, 1966, Final report of Louderback, G. D., 1941, Development of San _Francisco Bay preliminary soil exploration for a southern crossing of San abs. : Geol. Soc. America Bull., v. 52, p. 1952. Francisco Bay: California St.at.e Dept. Public Works, 72 p. ---1951, Geologic history of San Francisco Bay, in ,Jenkins, Carlson, P. R, Alpha, T. R., and McCu1loch, D. S., 1970, The 0. P., ed., Geologic guidebook to the San Francisco Bay f1oor of San Francisco Bay: California Geology, v. 23, p. 97- counties: California Div. Mines Bull. 154, p. 75-94. !07. Meade, R H., 1967, Petrology of sediments underlying areas of Carlson, P.R., and McCulloch, D. S., 1970, Bedrock-surface map of land subsidence in central California: U.S. Geol. Survey central San Francisco Bay, California: U.S. Geol. Survey Prof. Paper 497-C, 3;3 p. open-file map, scale 1:27,200. Milliman, J. D., and Emery, K. 0., 1968, Sea levels during the Chappell, ,John, 1974, Geology of coral terraces, Huon Peninsula, past 35,000 years: Science, v. 162, p. 1121-1123. New Guinea-A study of Quaternary tectonic movements and Nichols, D. R., and Wright, N. A., 1971, Preliminary map of his­ sea-level changes: GeoL Soc. America Bull., v. 85, p. 553-570. toric margins of marshland, San Francisco Bay, California: Cooper, W. S., 1967, Coastal dunes of California: GeoL Soc. U.S. GeOl. Survey open-file map, scale 1:125,000. America Mem. 104, 131 p. Phleger, F. B., 1970, Foraminiferal populations and marine marsh Finlayson, D. J., Hansen, W. R., Ford, R S., Scott, R. G., and processes: and , v. 15, p. 522-534. Vantine, J. V., 1967, Evaluation of ground water resources, Poland, J. F., 1971, Land subsidence in the , south Bay-App. A, geology: California Dept Water Re­ , San Mateo, and Santa Clara Counties, California: sources BulL 118-1, 153 p. U.S. Geol. Survey Misc. Field Studies Map MF-336, scale Flint, R F., 1971, Glacial and Quaternary geology: John Wiley 1:125,000. and Sons, New York, 892 p. Radbruch, D.H., and Schlocker, Julius, 1958, Engineering geol­ Gilbert, G-. K., 1917, Hydraulic-mining debris in the Sierra ogy of the Islais Creek Basin, San Francisco, California: Nevada: U5. Geol. Survey Prof. Paper 105, 154 p. U.S. Geol. Survey Misc. GeoL Inv. Map I-264, scale 1:12,000. Hall, N. T., 1966, Late Cenozoic stratigraphy bptween Mussel Sarna-Wojcicki, Andrei, 1976, Correlation oflate Cenozoic tuffs in Rock and Fleischhacker Zoo, San Francisco Peninsula, in the central Coast Ranges of California by means of trace- and A walker's guide to the geology of San Francisco: California minor-element chemistry: U.S. Geol. Survey Prof. Paper 972, Div. Mines and Geology, Spec. Supp. Mineral Inf. Service, 30 p. v. 19, no. 11, p. 22-25, Schlocker, Julius, Bonilla, M.G., and Radbruch, Dorothy, 1958, Hanna, G. D., 1944, Diatomaceae, in Shimer, H. W., and Shrcick, Geology of the San Francisco North quadrangle, California: R. R., editors, Index fossils of North America: New York, U.S. Geol. Survey Misc. GeoL Inv. Map I-272, scale 1:24,000. John Wiley and Sons, Inc., 837 p. Trask, P. D., and Rolston, J. W., 1951, Engineering geology of Helley, E. ,J., Lajoie, K. R., and Burke, D. B., 1972, Geologic map of San Francisco Bay, California: GeoL Soc. America BulL, Late Cenozoic deposits, Alameda County, California: U.S. v. 62, p. 1079-1!10. Geol. Survey Misc. Field Studies Map MF-429, scale 1:62,500. Treasher, R C., 1963, Geology of the sedimentary deposits in San Hinde, H, P., 1954, Vertical distribution of phanero­ Francisco Bay, California: California Div. Mines and Geol. gams in relation to tide levels: EcoL Mon., v. 24, p. 209-225. Spec. Rept. 82, p. ll-24. Kaye, C. A., and Barghoorn, E. S., 1964, Late QuateltJary sea­ Vasil'kovskiy, N. P., 1973, Sea level changes in thtl g;eological level change and crustal rise at Boston, , with past: P. P. Shirshov Inst. Oceanology, U.S.S.-R. Acad. Sci­ notes on the autocompaction of peat: Geol. Soc. America ences, p. 847-859. BulL, v. 75, p. 63-80. Wahrhaftig, Clyde, and Birman, J. H., 1965, The Quaternary of Lajoie, K. R., Helley, E. J., Nichols, D. R., and Burke, D. B., 1974, the Pacific mountain in California, in Wright, H. E., Geologic map of unconsolidated and moderately consolidated Jr., and Frey, D. G., eds., The Quaternary of the United deposits of San Mateo County, California: U.S. Geol. Survey States: Princeton _Univ. Press, p. 299-340. Misc. Field Studies Map MF-575, scale 1:62,500. Weller, J. M., 1959, Compaction of sediments: Am. Assoc. Petrol­ Lawson, A. C., 1894, The geomorphogeny of the coast of Northern eum Geologists BulL, v. 43, no. 2, 273-310. California: California Univ. Dept. Geology Bull., v. 1, p. 241- 27L Atwater

and

others

-DEPOSITIONAL

HISTORY,

SEA

-

LEV:EL

CHANGES,

CRUSTAL

MOVEMENT,

SAN

FRANCISCO

BAY,

CALIFORNIA-

Gt·ological

Survey

Professional

Paper

1014