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UTM GRID AND 1968 MAGNETIC NORTHDECLINATION AT CENTER OF SHEET

0°26'8 MILS

18°320 MILS

GNMN

0

0

0

1

1

1.5

.5 2

2

2Thousand Feet

Kilometers

Miles

Contour Interval 20 FeetDotted 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

12116

5Kilometers

5Miles

Mapping completed under

STATEMAP

FY 2001- 02

FY 2002- 03

FY 2003- 04

FY 2004- 05

NapaSonom

a

Novato

Mt. G

eorge

Napa

Petalum

a

Petalum

aRiver

Cuttings

Wharf

Glen E

llen

Cotati

Two R

ock

Sears P

oint

Yountville

Rutherford

GEOLOGIC MAP OF THE

YOUNTVILLE 7.5' QUADRANGLE

NAPA COUNTY, CALIFORNIA: A DIGITAL DATABASE

VERSION 1.0

By

Stephen P. Bezore1, Kevin B. Clahan2, Janet M. Sowers3, and Robert C. Witter3

Digital Database

By:

Carlos I. Gutierrez1

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

MESOZOICCRETACEOUS

JURASSIC

af alf ac Qhc Qhty Qhfy

Qht Qha QhfQf Qa

Qoa

Qls

sp

KJfs KJgv

Th

unconformity

unconformityTsv

Tsvrt

Tsvr

Tsvasl

Tsvdg Tsvdgp

TsvabslTsvt

Tsvatsl

Jb JgbJk

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.