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UTM GRID AND 2009 MAGNETIC NORTHDECLINATION AT CENTER OF SHEET

0

0

0

1

1

1.5

.5 2

2

2Thousand Feet

Kilometers

Miles

Scale 1:24,000

Contour Interval 40 feetSupplementary Contour Interval 20 feet

Datum is Mean Sea Level

MNGN

258 MILS1 MIL

14½° 0°03’

5Kilometers

5Miles

Napa

Mapping completed under STATEMAP

CGS CD 2002-07*

FY 2001-02

FY 2002-03

FY 2003-04

FY 1997-98

FY 2004-05

80680

San PabloBay

37

128

Sonoma

Novato

Mt. George

Napa

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Yountville

Rutherford

FairfieldSouth

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FairfieldNorth

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Mt. Vaca

FY 2006-07

FY 2005-06

Sebastopol

Santa RosaUSGSOF 2008-1009

*GIS data for the Cordelia and Fairfield South 7.5’ quadrangles available on CD - CGS CD 2002-07.

FY 2008-09

116

Two Rock

Valley Ford

116

12 121

121

80

780

Sonoma

Novato

Petaluma

Santa Rosa

Sebastopol

Rutherford

Kenwood

Glen EllenCotatiValley

Ford

Two Rock

Camp Meeker

FY 2007-08

Allen, J.R., 2008, NCGS Fieldtrip to the Wilson Grove and Petaluma formations, Sonoma County, California: Northern California Geological Society, February 23, 2008 Fieldtrip Guidebook.

BACE Geotechnical, 1994, Geotechnical Investigation, pH Adjustment/Corrosion Control Facility, 8001 River Road, Sonoma County, California: prepared for Sonoma County Water Agency, dated February 9, project No. 10323.7 plates 2 and 3.

Bedrossian, T.L., 1981, Geology and slope stability of the west Sebastopol study area, Sonoma County, California: California Division of Mines and Geology, Open-File Report 81-12, 39 p., scale 1:24,000.

Bezore, S.P., Koehler, R.D., and Witter, R.C., 2003, Geologic map of the Two Rock quadrangle, Sonoma and Marin counties, California: A digital database: California Geological Survey Preliminary Geologic Map website: http://www.conservation.ca.gov/CGS/rghm/rgm/preliminary_geologic_maps.htm

Blake, M.C., Jr., Graymer, R.W., and Stamski, R.E., 2002, Geologic map and map database of western Sonoma, northernmost Marin, and southernmost Mendocino, counties, California: U.S. Geological Survey Miscellaneous Field Studies Map MF-2402.

Blake, M.C., Jr., Smith, J.T., Wentworth, C.M., and Wright, R.H., 1971, Preliminary geologic map of western Sonoma County and northernmost Marin County, California: U.S. Geological Survey Basic Data Contribution 12, scale 1:62,500.

Christensen, W.P., 1973, Structure of Franciscan terrane of the Occidental-Guerneville area, California: Geological Society of America Bulletin, v. 84, no. 4, p. 1283-1287.

Delattre, M.P., and Koehler, R.D., 2008, Geologic Map of the Sebastopol 7.5’ quadrangle, Sonoma County, California: A digital database: California Geological Survey Preliminary Geologic Map website: http://www.conservation.ca.gov/CGS/rghm/rgm/preliminary_geologic_maps.htm

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.

Huffman, M.E., and Armstrong, C.F., 1980, Geology for planning in Sonoma County, California: California Division of Mines and Geology Special Report 120, 31 p., scale 1:62,500.

McLaughlin, R.J., Langenheim, V.E., Sarna-Wojcicki, A.M., Fleck, R.J., McPhee, D.K., Roberts, C.W., McCabe, C.A., and Wan, Elmira, 2008, Geologic and geophysical framework of the Santa Rosa 7.5’ quadrangle, Sonoma County, California: U.S. Geological Survey Open-File Report 2008-1009, 51 p.

Powell, C.L., II, Allen, J.R., and Holland, P.J., 2004, Invertebrate Paleontology of the Wilson Grove Formation (late Miocene to late Pliocene), Sonoma and Marin counties, California, with some observation on its stratigraphy, thickness, and structure: U.S. Geological Survey Open-File Report 2004-1017, 54p., Plate 1, scale 1:53,360.

Sarna-Wojcicki, A.M., 1992, Long-term displacement rates of the San Andreas fault system in northern California from the 6-Ma Roblar tuff [abs.] in Borchardt, Glenn, and others, editors, Proceedings of the Second Conference on Earthquake Hazards in the Eastern San Francisco Bay Area: California Department of Conservation, Division of Mines and Geology Special Publication 113, p. 29-30.

Travis, R.B., 1952, Geology of the Sebastopol quadrangle, California: California Division of Mines Bulletin 162, 33 p., Plate 2, scale 1:62,500.

Witter, R.C., Knudsen, K.L., Sowers, J.M., Wentworth, C.M., Koehler, R.D., and Randolph, C.E., 2006, Maps of Quaternary deposits and liquefaction susceptibility in the central San Francisco Bay Region, California: U.S. Geological Survey Open-File Report 2006-1037, scale 1:24,000.

Wiegers, M.O., 2008, Geologic map of the Valley Ford 7.5’ quadrangle, Sonoma and Marin counties, California: A digital database: California Geological Survey Preliminary Geologic Map website: http://www.conservation.ca.gov/CGS/rghm/rgm/preliminary_geologic_maps.htm

SELECTED REFERENCES

ACKNOWLEDGEMENTS

Thanks to Trinda Bedrossian for access to her field notes and maps that formed the basis for the 1981 CDMG publication on the west Sebastopol area (OFR 81-12), and to Don Ristau for sharing his geologic observations in the Freestone area.

SYMBOL EXPLANATION

Contact between map units - solid where accurately located; dashed whereapproximately located; short dash where inferred.

Landslide - arrows indicate principal direction of movement.

Strike and dip of bedding plane25

Fault - solid where accurately located; dashed where approximately located;short dash where inferred; dotted where concealed; queried where uncertain.U = upthrown block, D = downthrown block. Arrow and number indicate direction and angle of dip of fault plane.

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Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

}Quaternary

Tertiary}CORRELATION OF MAP UNITS

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DESCRIPTION OF MAP UNITS(See Witter and others (2006), for more informationon Quaternary units).

Qa

Artificial dam fill (historical) – Earth dams, rock-fill dams, and embankments constructed to impound water.

Stream channel deposits (modern to latest Holocene) – Fluvial deposits within active, natural stream channels composed of loose sand, silt, and gravel.

Alluvial deposits, undivided (latest Holocene) – Fluvial sediment deposited on the modern flood plain.

Stream terrace deposits (latest Holocene) – Stream terrace deposits of sand, silt, gravel, and minor clay. Estimated to be latest Holocene in age based on elevation and/or records of historical inundation.

Basin deposits (Holocene) – Sediment accumulated in topographic basins from slow moving or standing water. Consist of horizontally stratified sand, silt, and clay; may be interbedded with lobes of coarser alluvial deposits.

Alluvial deposits, undivided (Holocene) – Alluvium deposited in fan, terrace, or basin environments that could not be readily separated for mapping. Typically, consist of poorly to moderately sorted sand, silt, and gravel that form smooth geomorphic surfaces with little to no dissection.

Qhb

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Alluvial fan deposits (Holocene to latest Pleistocene) – Moderately to poorly sorted deposits of sand, gravel, silt, and clay mapped on gently sloping, fan-shaped, relatively undissected, alluvial surfaces where age of deposits is unknown.

Alluvial deposits, undivided (Holocene to latest Pleistocene) – Sand, gravel, silt, and clay mapped in small valleys and where separate fan, basin, terrace, and active stream channel units could not be delineated at the scale of mapping.

Qht

Landslide deposits (historical to Pleistocene) – Arrows indicate direction of movement; queried where landslide existence is questionable.

Older alluvium (early to late Pleistocene) – Undivided alluvial fan, stream terrace, and basin deposits. Gray to brown, orange- to red-weathering, poorly sorted, sand, silt, and gravel composed of Franciscan basement material with conspicuous red and green chert, and lesser volcanic clasts.

Older Stream terrace deposits (early Pleistocene?) – Yellowish-brown, orange to reddish- brown-weathered, silty sand, and gravel. Lithologically similar to Qoa, but more deeply weathered and found at higher elevations.

Wilson Grove Formation (late Pliocene to late Miocene) – Light-gray to yellow-brown marine sandstone. The sandstone is fine- to medium-grained, well-sorted, massive or thick-bedded, and locally fossiliferous or tuffaceous. Well-rounded pebbles of chert and quartz occur in scattered stringers and lenses of pebbly sandstone. Tuffaceous lenses and more persistent beds vary from less than 1 cm to over 5 m thick. Thicker beds distinguishable at map scale (Tt) vary laterally and vertically from gray tuffaceous sandstone to white water-laid tuff and yellow to gray pumice breccia. Portions appear lithologically similar to the informally named Roblar tuff (Sarna-Wojcicki, 1992) that is found interbedded with the Wilson Grove and Petaluma formations farther west, and most reliably dated by Ar/Ar at 6.26 Ma (McLaughlin and others, 2008); however, definitive correlations within the study area remain to be established.

Middle Petaluma Formation (late Miocene) – Fluvial deposits previously mapped as part of the Wilson Grove Formation (Travis, 1952; Blake and others, 1971); assigned to Tpm based on lithology and stratigraphic relationships described by Allen (2008). Light-gray, yellowish-gray, brown-weathering, sandstone and conglomerate. Conglomerate is both clast- and matrix-supported, with sub-angular to sub-rounded clasts of graywacke and other Franciscan basement rocks, with subordinate volcanic clasts.

Franciscan Complex, Coastal or Central Belt Sandstone (late Eocene to Late Creta-ceous) – Composed chiefly of broken, massive to distinctly bedded, light-gray to greenish-gray, brown- and orange-weathering sandstone. Unit also includes some argillite and shale with disrupted bedding. Sandstone is mostly feldspathic-lithic wacke with detrital biotite and muscovite (Blake and others, 2002).

Alluvial fan deposits (Holocene) – Sediment deposited by streams emanating from canyons onto alluvial valley floors. Sediments are typically moderately to poorly sorted and composed of sand, gravel, silt, and occasionally clay.

Sandstone, shale, and Conglomerate (Early Cretaceous and Late Jurassic) – Predominantly pebble to cobble conglomerate, but also includes distinctly bedded, dark- to light-gray, brown-weathering, coarse-grained lithic wacke and shale. Clasts include quartz- and plagioclase-porphyry volcanics, black chert and quartzite.

Knoxville Formation (Late Jurassic) – Dark-gray to black, thin-bedded shale with occasional interbeds of biotite-lithic wacke; contains only Late Jurassic fossils.

Keratophyre and quartz keratophyre tuff (Late Jurassic) – Well-bedded, white to red- and green-stained, intermediate and silicic tuff, and greenish-gray fine- to coarse-grained tuffaceous sandstone. Contains Late Jurassic (Tithonian) radiolarians, and thought to be correlative with tuff of the Lotta Creek Formation of the western San Joaquin Valley (Blake and others, 2002).

Serpentinite (Late and Middle Jurassic) - Highly sheared, fault-bounded blocks and slivers of serpentinite and serpentinized harzburgite.

Serpentinite matrix mélange (Late and Middle Jurassic) – Sheared meta-serpentinite containing blocks and lenses of greenstone, high-grade metamorphic rocks, and graywacke.

Franciscan graywacke and mélange (Late Cretaceous to Early Jurassic) – Predominantly broken and locally sheared, massive to distinctly bedded, gray to green, brown- to orange-weathering, lithic wacke, and dark-gray shale. Also includes areas of mélange (see KJfm) not differentiated from the more coherent graywacke due to extensive forest cover, gradational contacts, and/or size relative to map scale.

Franciscan Complex, Central Belt mélange (Late Cretaceous to Early Jurassic) – Tectonic mixture of penetratively sheared argillite and graywacke that forms a matrix around more coherent rock masses of varied lithology, including greenstone (gs) and serpentinite (sp) blocks large enough to be mapped separately, as well as chert, coherent graywacke, schist, and other metamorphic rocks.

Greenstone – Variably altered basalt and other mafic volcanic rocks. Dark greenish-gray to black, weathered dark-brown to orange, predominantly massive, occasionally vesicular, or with pillow structure preserved.

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STATE OF CALIFORNIA - ARNOLD SCHWARZENEGGER, GOVERNORTHE NATURAL RESOURCES AGENCY - MIKE CHRISMAN, SECRETARY FOR NATURAL RESOURCES

DEPARTMENT OF CONSERVATION - BRIDGETT LUTHER, DIRECTORCALIFORNIA GEOLOGICAL SURVEYJOHN G. PARRISH, Ph.D., STATE GEOLOGIST

Copyright © 2009 by the California Department of ConservationCalifornia Geological Survey. All rights reserved. No part ofthis publication may be reproduced without written consent of theCalifornia Geological Survey.

"The Department of Conservation makes no warranties as to thesuitability of this product for any given purpose."

GEOLOGIC MAP OF THECAMP MEEKER 7.5' QUADRANGLE

SONOMA COUNTY, CALIFORNIA: A DIGITAL DATABASEVERSION 1.0

ByMarc P. Delattre1 and Richard D. Koehler2

Digital Database by

Marc P. Delattre1 and Carlos I. Gutierrez1

2009

1. California Geological Survey2. William Lettis & Associates, Inc., Walnut Creek, CA

This geologic map was funded in part by the USGS National Cooperative Geologic MappingProgram, Statemap Award no. 08HQAG0102

38°30'122°52'30''

38°22'30''122°52'30''

38°30'

38°22'30''123°00'

Topographic base from U.S. Geological SurveyCamp Meeker 7.5-minute Quadrangle, 1995UTM projection, Zone 10, North American Datum 1927

123°00'

Revised: 9/28/2009

Preliminary Geologic Map available from:http://www.conservation.ca.gov/cgs/rghm/rgm/preliminary_geologic_maps.htm