? ? ? 40 40 50 50 30 45 30 40 43 50 30 15 70 10 10 5 20 10 5 9 5 45 55 36 72 69 85 50 45 41 32 32 14 sp KJgv Jk Qls Qls sp Qls Qls KJgv? Qls sp Qls sp af sp Jgb Tsvasl Tsvabsl Qls Qha Tsvasl af Tsvasl Tsvdg Qhf Tsvabsl Tsvdg Tsvdg Tsvr Qpf Qf Tsvdg KJgv KJgv Tsvdg Qhf Tsvasl Tsvdg KJgv Tsvr Tsvdg Qha Qhf Qls Qha Tsvatsl Tgisl Tsvabsl Tsvabsl Qhty Tgisl Qha Qhf Qhf Tsvdg Tsvabsl Qhty Qhty Tgisl Qhty Tsvasl Qpf Tsvdg Qf Qhf Tsvrt Tsvdg Tsvdgp Tsvt Tsvdg Tsvasl Tsvasl Tsvasl Tsvasl Tsvdg Tsvdg Tsvasl Tsvasl Tsvasl Tsvasl Qa Qha Qha Qha Tsvt af af af af af af af af Tsvdg Qls Qls Qls sp Tsvt Tsvasl Jb Jb Qls Qls Qls Qls Qls Qls sp sp sp KJfs KJfs Qls Qls Qls Qls Qls Qls Qls Qls Qls Qls Qls Qls af Qls Qls Qls Qls sp Tsvasl Tsvt Qhc sp Qha Qha Qls Qls af af af Qls Qls Qls Tsvt KJgv Tsvdgp Tsvdg Tsvdgp Qhf Qhf Qf Qpf Qhf Qf KJgv Qpf Tsvatsl Qpf Qha Qhty Qhty Qhf Tsvdg Qha Qf Qf Qhfy Qhty Tsvdg Qf Qht Tsvabsl Tsvdg af af Qls Qhty Tsvasl Tsvdg af Qhty Qhty alf alf Qhty Qhc KJgv af af af af Qhty Qhty Qls Qf KJgv Qf Tsvasl Qls Qht af af af Tsvasl Qf Tgisl Qls KJgv af KJgv af KJgv af KJgvm af KJgv Tsvatsl Qha Qhc af alf af af alf af Qhc af ac af Qls Qls Qls Qls Tsvdg Tsvatsl Qls Qls Qls Qhc af af af Qhc Qhty af af af af af Qhc alf Qhty Qls af af af Qls Qls af af Tsvdgp Tsvdgp Tsvdg Tsvdg Tsvdg Tsvdg Tsvdgp Tsvdg Tsvasl Tsvdgp KJgv KJgv Qls Qha Qf Tsvabsl Qhty Tsvt Tsvt Tsvasl Tsvabsl Qha Qha Qhc Qhty Tsvabsl Th Th Th KJfs Th Tsvpf Qls Qls Qhf Qhty Tsvasl ? Qhty Qf ? ? Qhty Qhfy ? Qpf Qoa UTM GRID AND 1968 MAGNETIC NORTH DECLINATION AT CENTER OF SHEET 0°26' 8 MILS 18° 320 MILS GN MN 0 0 0 1 1 1 .5 .5 2 2 2 Thousand Feet Kilometers Miles Contour Interval 20 Feet Dotted Lines Represent 5 Foot Contours Scale 1:24,000 Fox, K.F. Jr., 1983, Tectonic setting of late Miocene, Pliocene and Pleistocene rocks in part of the Coast Range North of San Francisco, California: U.S. Geological Survey Professional Paper 1239, 92 p. Fox, K.F. Jr., Fleck, R.J., Curtis, G.H., and Meyer, C.M., 1985, Potassium-Argon and fission track ages of the Sonoma Volcanics in an area north of San Pablo Bay, California: U.S. Geological Survey MIscellaneous Field Studies Map MF-1753, scale 1:250,000. Graymer, R.W., Jones, D.L., and Brabb, E.E., 2002, Geologic map and map database of northeastern San Francisco Bay region, Most of Solano County and parts of Napa, Marin, Contra Costa, San Joaquin, Sacramento, Yolo, and Sonoma counties: U.S. Geological Survey Miscellaneous Field Studies Map MF-2403, scale 1:62,500. Knudsen, K.L., Sowers, J.M., Witter, R.C., Wentworth, C.M., Helley, E.J., 2000, Preliminary geologic maps of the Quaternary deposits and liquefaction susceptibility, nine-county San Francisco Bay Region, California: A digital database: U.S. Geological Survey Open-File Report 00-44, version 1.0, scale 1:52,500. Mankinen, E.A., 1972, Paleomagnetism and potasium-argon ages of the Sonoma Volcanics, California: Geological Society of America Bulletin, v. 83, p. 2063-2072. McLaughlin, R.J., Sarna-Wojcicki, A.M., Fleck, R.J., Langenheim, V., Jachens, R.C., and Deino, A., 2005, Framework Geology and Structure of the Sonoma Volcanics and Associated Sedimentary Deposits of the Right-Stepped Rodgers Creek- Maacama Fault System and Concealed Basins Beneath Santa Rosa Plain, in Late Neogene Transition from Transform to Subduction Margin East of the San Andreas Fault in the Wine Country of the Northern San Francisco Bay Area, California: Field Trip Guidebook to accompany the 2005 Geological Society of America Cordilleran Section Meeting, San Jose, California, April 29 - May 1, 52 p. Weaver, C.E., 1949, Geology of the Coast Range immediately north of the San Francisco Bay Region, California: Geological Society of America Memoir 35, 242 p., plates 6, 10, scale 1:62,500. References 12 121 37 780 128 12 116 5 Kilometers 5 Miles Mapping completed under STATEMAP FY 2001- 02 FY 2002- 03 FY 2003- 04 FY 2004- 05 Napa Sonoma Novato Mt. George Napa Petaluma Petaluma River Cuttings Wharf Glen Ellen Cotati Two Rock Sears Point Yountville Rutherford GEOLOGIC MAP OF THE YOUNTVILLE 7.5' QUADRANGLE NAPA COUNTY, CALIFORNIA: A DIGITAL DATABASE VERSION 1.0 By Stephen P. Bezore 1 , Kevin B. Clahan 2 , Janet M. Sowers 3 , and Robert C. Witter 3 Digital Database By: Carlos I. Gutierrez 1 2005 Copyright © 2005 by the California Department of Conservation California Geological Survey. All rights reserved. No part of this publication may be reproduced without written consent of the California Geological Survey. "The Department of Conservation makes no warranties as to the suitability of this product for any given purpose." This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program, STATEMAP Award no. 04HQAG0074 Topographic base from the U.S. Geological Survey UTM Projection, zone 10, North American Datum 1927 STATE OF CALIFORNIA- ARNOLD SCHWARZENEGGER, GOVERNOR THE RESOURCES AGENCY- MICHAEL CHRISMAN, SECRETARY FOR RESOURCES DEPARTMENT OF CONSERVATION- BRIDGETT LUTHER THOMPSON, DIRECTOR CALIFORNIA GEOLOGICAL SURVEY JOHN G. PARRISH, PhD., STATE GEOLOGIST 38°22'30" 122°22'30" 122°15'00" 38°22'30" 122°15'00" 38°30'00" 122°22'30" 38°30'00" 1. California Geological Survey, 801 K St. MS 12-31, Sacramento, CA 95814 2. California Geological Survey, 185 Berry St., Suite 210, San Francisco, CA 94107 3. William Lettis & Associates, Inc., 1777 Botello Drive, Suite 262 Walnut Creek, CA 94596 Preliminary Geologic Map available from: http://www.conservation.ca.gov/cgs/rghm/rgm/preliminary_geologic_maps.htm Strike and dip of inclined bedding. 25 Landslide - Arrows indicate principal direction of movement, queried where existence is questionable; hachures indicate headscarp (source area). Contact between map units - Solid where accurately located, dashed where approximately located, dotted where concealed. 25 Strike and dip of inclined foliation. Vertical foliation. Fault - Solid where accurately located, dashed where approximately located, dotted where concealed, queried where uncertain. ? Symbol Explanation QUATERNARY Pliocene Holocene Pleistocene Miocene TERTIARY CENOZOIC Unit Correlation MESOZOIC CRETACEOUS JURASSIC af alf ac Qhc Qhty Qhfy Qht Qha Qhf Qf Qa Qoa Qls sp KJfs KJgv Th unconformity unconformity Tsv Tsvrt Tsvr Tsvasl Tsvdg Tsvdgp Tsvabsl Tsvt Tsvatsl Jb Jgb Jk Tgisl Tsvpf Qpf Landslide deposits (Holocene and Pleistocene) - Includes debris flows and block slides. Serpentinite Alluvium, undivided (latest Pleistocene to Holocene) - Flat, relatively undissected fan, terrace, and basin deposits. Fan deposits (Pleistocene) - Sand, gravel, silt, and clay that is moderately to poorly sorted and bedded. Mapped on alluvial fans where greater dissection indicates latest Pleistocene age. Alluvial deposits, undivided (early to late Pleistocene) - Alluvial fan, stream terrace, basin, and channel deposits. Topography is gently rolling with little or no original alluvial surfaces preserved; moderately to deeply dissected. Alluvium, undivided (Holocene) - Alluvium deposited on fans, terraces, or in basins; composed of sand, gravel, silt, and clay that are poorly sorted. Stream terrace deposits (latest Holocene <1,000 years) - Stream terraces deposited as point bar and overbank deposits; composed of moderately sorted clayey sand and sandy clay with gravel. Alluvial fan deposits (latest Holocene) - Alluvial fan sediment deposited by streams emanating from Dry Creek drainage, composed of moderately to poorly sorted and bedded sand, gravel, silt, and clay. Modern stream channel deposits (Holocene <150 years) - Deposits in active, natural stream channels; consists of loose alluvial sand, gravel, and silt. Artificial stream channel (Holocene, historic). Artificial fill (Holocene, historic) - May be engineered and/or non-engineered. Artificial levee fill (Holocene, historic) - May be engineered and/or non-engineered. Alluvial fan deposits (Holocene) - Alluvial fan sediment deposited by streams emanating from mountain drainages onto alluvial valleys; composed of moderately to poorly sorted sand, gravel, silt and clay. (See Knudsen and others (2000), for more information on Quaternary units). Alluvial fan deposits (latest Pleistocene <~30,000 years to Holocene) - Sand, gravel, silt and clay mapped on gently sloping, fan-shaped, relatively undissected alluvial surfaces. Stream terrace deposits (Holocene <10,000 years) - Stream terraces deposited as point bar and overbank deposits; composed of moderately to well-sorted and bedded sand, gravel, silt, and minor clay. Unit Explanation Qhfy alf af Qhf Qls Qa Qpf Qoa Qha Qhty Qhc ac Qf Qht Tgisl Th KJfs Jb Jgb Jk sp KJgv Tsvrt Tsvpf Tsvr Tsvdg Tsvdgp Tsvasl Tsvabsl Tsvatsl Tsvt Gabbro Basalt Great Valley Sequence (Early Cretaceous and Late Jurassic) - Sandstone, pebble conglomerate, siltstone, and shale, weak, moderately weathered. Stags Leap stock. Coarse to fine-grained granitic intrusive with abundant quartz veining and hydrothermal alteration. Franciscan graywacke (Early Cretaceous and Late Jurassic) - Thick-bedded graywacke with minor interbedded shale. The graywacke is moderately to intensely sheared but lacks tectonic blocks characteristic of Franciscan melange. Knoxville Formation (Late Jurassic) - Black shale and thin beds of sandstone. The unit contains only Late Jurassic fossils (Graymer and others, 2002). Huichica Formation (Pliocene) - Gravel, sand, reworked tuff, and clay. A tuff interbed yields a K-Ar date of 4.09±0.19 Ma (Fox and others, 1985). Sonoma Volcanics (Pliocene to Miocene) Tsvpf - Ash flow tuff and welded ash flow tuff, locally perlitic. Includes the 3.34-3.19 tuff of Petrified Forest (Fox and others, 1985, McLaughlin and others, 2005). Tsvrt - Rhyolite ash flow tuff. Black to light grey vitrophyre with angular lithic clasts. Tsvdg - Dacite of Mt. George - Flows, domes and shallow intrusions of gray to tan porphyritic dacite. The dacite is typically strongly flow banded. The upper surfaces of flows and the margins of domes and intrusions are commonly perlitic. The base of the flows is a black porphyritic pitchstone and pitchstone breccia. K-Ar ages for the dacite on the Mt. George quadrangle are 4.3±0.2 and 3.73±1.23 Ma (Mankinen, 1972; Fox and others, 1985). Tsvdgp - Pumice breccia, pumice lapilli tuff, and pumice lapilli tuff with lithic fragments and perlitic glass fragments that mantle flows and domes and occur between dacite flows. Tsvr - Undifferentiated rhyolite lava flows, and flow breccias. Light grey to dark grey. Tsvasl - Andesite lava flows and flow breccias of Stags Leap. Tsvabsl - Andesite flow breccia of Stags Leap. Tsvt - Light colored ash flow tuff. Lithic rich in places . Tsvatsl - Andesite ash flow tuff and tuff breccia of Stags Leap.