STATE OF CALIFORNIA- GRAY DAVIS, GOVERNOR CALIFORNIA GEOLOGICAL SURVEY THE RESOURCES AGENCY- MARY NICHOLS, SECRETARY FOR RESOURCES JAMES F. DAVIS, STATE GEOLOGIST DEPARTMENT OF CONSERVATION- DARRYL YOUNG, DIRECTOR GEOLOGIC MAP OF THE Qhf Qof QTu Qhf Qhty Qhly Qhc Qof Tsvm SEARS POINT 7.5' QUADRANGLE Qhf Qhc Qhty Qhc Qof Qhf Qof af QTu Qhc 30 Qhc 20 Tpu Qhf SONOMA, SOLANO, AND NAPA COUNTIES, CALIFORNIA: A DIGITAL DATABASE QTu Qof Th 35 Qhly af Qhty Qof Qha VERSION 1.0 1 Qhty Tpu Tp? By 50 Tsvm 20 Qf Qhbm 1 2 1 2 1 Qof David L. Wagner , Carolyn E. Randolph-Loar , Stephen P. Bezore , Robert C. Witter , and James Allen Tp? af Tsvm Tpu? Qof 49 1 Th 43 Qha Digital Database Qof Qha alf Qhbm 70 Unit Explanation by 1 1 55 Qhbm Jason D. Little and Victoria D. Walker Tsvm Qof (See Knudsen and others (2000), for more information on Qf 2002 30 Quaternary units). Tpu 40 Tp? Qhbm af Artificial fill Qhty Tpu Qhay afbm af 1. California Geological Survey, 801 K st. MS 12-31, Sacramento, CA 95814 Qof Qhbm 30 Qhf af Tsvt 2. William Lettis & Associates, Inc., 1777 Botello Drive, Suite 262 Walnut Creek, CA 94596 Tsvm Tsvm alf Tsvm Tsvm alf Qhbm afbm Artificial fill placed over bay mud 80 Tsvt? Tsvm Qhbm Qls Qhay 80 Qls Tsvt Qhbm Qhbm Qhbm Artificial levee fill Qhf alf 35 45 Tsvt Tsvt Tsvm 40 Tsvm Tsvt Qhbm Qhf 20 Qls Qhbm Qha af Qhc Late Holocene to modern (<150 years) stream channel deposits in active, natural KJfm Franciscan Complex melange. Tectonic mixture of masses of resistant rock including Tsvm stream channels. Consists of loose alluvial sand, gravel, and silt. sandstone, altered mafic volcanics (greenstone), chert, gabbro, exotic Qhbm Qhf Tsvm 35 metamor phic rocks imbedded in a sheared shaley matrix. Blocks with melange Qhbm 30 Qhf large enough to be shown at t his scale are denoted as: 40 Qpf Qhly Latest Holocene (<~1,000 years) alluvial fan levee deposits. Natural levee deposits of 45 Qf Tsvr Qo 20 alluvial deposits along Sonoma Creek. 45 Tsvt afbm Qls alf ss - sandstone Qls 5 alf Qha Qls Qhbm Qhbm Tsvt Tsvm 45 Qhty Latest Holocene stream terrace deposits. Stream terraces are deposited Tsvr Qha ch - chert alf as point bar and overbank deposits by Sonoma Creek. Tsvr Tsvr Tsvm Qls Tp Tsvm Qhbm Qhbm gs - greenstone (altered ma fic volcanic rocks). Tvb Tsvr Qhf Tp Qhbm Qhay Latest Holocene alluvial deposits. Fluvial sediment deposited on the Qhbm sch - schist and semischist Tsvr Qha Tsvm Qhbm modern flood plain of Sonoma Creek. Tsvt Qf Tsvm alf Tdm Serpentinized ultramafic rocks. Tsvt Qhbm Qhbm Holocene (<10,000 years) bay mud. Silt, clay, peat, and fine sand deposited at or near sp Tdm? alf Qhbm sea level in San Pablo Bay. Tdt 65 Tsvm alf 60 Tsvm Qhbm Qha Tsvm Tdm Tsvt Tpm Tsvm Qhbm Qhbm Tdm Tsvt Qhbm Tsvt Tsvt Qhbm Qhbm Qhbm Qhf Holocene alluvial fan deposits. Sand, gravel, silt, and clay deposited by Qls Tsvm Tdr? Tdm63 Tsvt streams emanating from canyons onto alluvial valley floors. Unit Correlation Tdt? Tsvm Tpm Tsvt Qhbm Sediment is poorly to moderatly sorted and bedded. Qls Qf Qhbm Qls Tsvm af afbm alf Qf Qls Tsvt Tsvt Qha Tpl? Tsvt Qhbm Qha Holocene alluvium, undivided. Alluvium deposited on fans, terraces, or Holocene 45 Tsvr Tsvm Tsvm } 47 in basins. Sand, gravel, and silt that are poorly sorted. Qhc Qhly Qhty Qhay Qhbm Qhbm Qha Qls Tsvm Tdm Tsvm afbm Quaternary Tsvr 45 Qhf Qls 35 Qls Landslides. Includes debris flow and block slump landslides. Qf } Tsvt 64 Arrows show the direction of movement. Qpf Qf Tpl? Tsvr Qhbm Qhbm Qoa Pleistocene Qls } 70 Tsvt Tsvm Tsvt Tdt 40 Qhbm Qf Latest Pleistocene (<30,000 years) to Holocene alluvial fan deposits. Sand, gravel, silt QTu Qls Tvb Tdm 40 Qls Tpm R Tsvm 35 Tsv and clay mapped on gently sloping, fan-shaped, relatively }Pliocene Tdm Tsvr o Tpl d Th 42 g undissected alluvial surfaces. e alf rs Qhbm Qhbm Qhbm Qha Qls 50 Tsvt C Trt Qls re Tsvm Qpf Latest Pleistocene fan deposits. Sand, gravel, silt, and clay that is e Qhbm Tpu Tsvm Tvb Tpl Tpl? k Qf 38 45 F moderately to poorly sorted and bedded. Mapped on alluvial Qha a Tpl? u Tsv Tsvt 60 lt fans where greater dissection indicates latest Pleistocene age. Z Tpl o Tsvt Tp Tpm Tpm n Tdm e Tsvr Tertiary Tdm Tsvm Tvb Tsvm Tdm R Tdm Qhbm och Tpl e C Tdt 40 Qls Miocene ard Tdm Qoa Early to late Pleistocene alluvial deposits, undivided. Alluvial fan, stream KJfm Tdm oza Tpl Fa Qls alf ult Tdm afbm terrace, basin, and channel deposits. Topography is gently rolling Qls Qhbm } Qha 30 af Tsvm with little or no original alluvial surfaces preserved; moderately to } Qls Qhbm Tdr Tdm 20 deeply dissected. Tdr Qf Qhbm Qls Tdr Qls QTu Gravel, sand, reworked tuff and clay of unknown age. Sediments derived Tdm Tdt Tdr 67 Tsvm alf Tpl? Tdm af mostly from the Sonoma Volcanics. Tp Qha Tsvr Qf KJfm Qhc Tpl? Tpl Qls Qf Th Huichica Formation. Gravel, sand, reworked tuff and clay. Sediments derived Qls 40 }Cretaceous Trt Tdr Qha 45 af mostly from the Sonoma Volcanics. A tuff interbed yields a K/Ar date KJfm 40 30 Tp 45 of 4.09+-0.19 [Andrei Sarna, written communication, 1981 reported in KJfm Tpl? Qf Kelly (1982)]. Qls sp }Jurassic Tpu Tpl Tsvm afbm Petaluma Formation. A predominantly lacustrine and fluvial deposit with esturine 13 Tpu? Tdr and transitional marine horizons consisting of siltstone, sandstone, shale, Qls KJfm Qhbm conglomerate, with minor silicified tuff, chert, lignite, and limestone. Qls Tpl Qhf Symbol Explanation KJfm 19 Qhf Divided into three subunits: Qhf alf Tpm Qls Trt Tpu Contact between map units - solid where accurately located, dashed where gs Qls 25 Trt Qhty Qhbm Qhbm Tpu- Upper Petaluma Fm. Massive, well sorted sandstone, siltstone, approximately located; short dash where inferred; dotted where concealed. 30 sch ss Qhf Tp Tpu Tpm and conglomerate. Conglomerate is rich in laminated siliceous Tp 27 ch Tdr Qhf shale (Monterey Fm.) fragments and Tertiary volcanics, with sp Qls Tpl Fault - solid where accurately located, dashed where approximately located; Qhty Franciscan clasts. The Roblar Tuff (Trt), dated at 6.26 Ma (Robert short dash where inferred; dotted where concealed. U = upthrown block, 54 44 Fleck, written communication, 2002) is interbedded with the Upper D = downthrown block. Arrow and number indicate direction and angle 40 Qhf Petaluma. 49 Tp Qhty of dip of fault plane. 34 alf 50 Tpu 35 Qhbm Tpm- Middle Petaluma Fm. Siltstone with interbedded conglomerate. Thrust fault- solid where accurately located; dashed where approximately 42 Qhf sp 30 Clasts in conglomerate are mostly pebbles derived from the located; short dash where inferred; dotted where concealed. 48 ~ ~ Franciscan, but clasts of Cretaceous and Tertiary sandstone KJfm 38 ~ Qhbm Qls KJfm ~ ~ as well as Tertiary volcanics are present. Minor siliceous shale Detatchment surfaces of mega-landslide masses. Qls 38 ~ ~ ~ ~ Qha 65 fragments from the Monterey Formation are also present. ~ ~ ~ alf ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 38 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Zone of intense shearing along the Tolay Fault Zone. Qls 45 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ T ~ Qhbm Tpl- Lower Petaluma Fm. Dominantly bluish to green clayey siltstone and sch Tp o ~ ~ Qhbm 10 la ~ 20 y F~ ~ shale with interbeds of silicified tuff, siliceous limestone, lignite, Syncline - Dashed where approximately located; dotted where concealed. 18 au 69 lt ~ ~ Qhbm 18 47 Zo Qhbm and rare bituminous chert. Laminated siltstone near the base in Qls ne ~ ~ 13 ~ Qhbm places. Localities near Tolay Creek and elsewhere have yielded ~ ~ Strike and dip of sedimentary beds: 30 alf transitional marine and estuarine horizons in a predominantly Qoa Tpu 10 47 ~ ~ 12 ~ lacustrine and fluvial deposit 80 Qls ~ ~ Qhbm 25 20 ~ ~ ~ Inclined af Qls ~ ~ ~ Tvb Basalt that occurs along the Rodgers Creek Fault Zone. 22 30 46 ~ ~ afbm Qhbm Qls ~ alf ss Qhbm Sonoma Volcanics- Mafic lava flows, breccias, agglomerate tuff, tuff breccia with Horizontal Qhf ~ ~ Qhbm interbedded fuffaceous sediments; also includes dacitic to rhyolitic lava 35 40 afbm Qhbm Qha Qhbm 25 Trt Trt af flows, debris flows, tuff, and tuffaceous sediment. The age range for the Qoa 12 Tsvm 5 18 alf Sonoma Volcanics on this quadrangle is 8.65 to 3.80 Ma (Fox and others, Landslide - arrows indicate principal direction of movement. Queried where questionable. Tp? Trt af Qhbm 1985; Youngman, 1989). The Sonoma Volcanics are divided into the 37 Qls Qhbm Tsv Tsvt following subunits. 40 42 Qhbm Trt Tsvr 30 47 Tsvm- Mafic flows and breccias. Andesite and basaltic andesite. Age Qoa 24 Qoa 37 range is 7.28 to 3.80 Ma (Youngman, 1989). References Qhf 30 Qhbm af 30 af Tpu Qoa Qha Tsvt- Silicic tuff and interbedded tuffaceous sediments. Interbedded sand Cebull, S.E., 1958, The structure and stratigraphy of portions of the Mare Island, Sears Point, and Richmond Qoa Qhf Qhf and gravel is similar to the MIddle Petaluma Formation. quadrangles, California: University of California, Berkeley, M.A. Thesis, 79 p., scale 1:24.000. Qoa afbm Qoa Qhbm Huffman, M.E., and Armstrong, C.F., 1980, Geology for planning in Sonoma County, California: California Qpf Tsvr- Rhyolitic to dacitic flows, breccias, and sediments. Pink, white, gray, Qhbm Division of Mines and Geology Special Report 120, 31 p., plate 3A, scale 1:62,500. Qhf brown flow banded rhyolite in flows, debris flows and breccia. Qoa Qha Interbeds of sand, gravel, and tuff. Dates (Ar/Ar) range from 7.36 Qhf Qhbm Fox, K.F.