Preliminary Geologic Map available from: PRELIMINARY ... · Jv KJgvs Jd Jv 0 0 0 1 1.5 1.5 2 2 2...

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KJgvc KJgvc KJgvc KJgvc Qls Qls Jv KJgvs Jd Jv 0 0 0 1 1 1 .5 .5 2 2 2 Thousand Feet Kilometers Miles Scale 1:24,000 Contour Interval 40 feet Supplementary Contour Interval 10 feet National Geodetic Vertical Datum of 1929 UTM GRID AND 2012 MAGNETIC NORTH DECLINATION AT CENTER OF SHEET MN GN 249 MILS 1 MIL 14 1 /3° 0°02’ USGS SIM-2858 (Na (Na (Na (Na (Na (Na (Napa) pa) pa) pa) pa (Na (Na (Na (Na N N N pa) pa) pa) pa a a (Sa (Sa (S (S a acram mento o) ) (La (La (La (Lakep kep kep kep kep k ort ort ort ort rt) ) ) ) ) (La (La (La (Lakep kep kep ke k keport ort ort ort ) ) ) p na na na na) ) Ar Ar Ar Ar A en en en en Po Po Po Po Po oint int int int int int (P (P (P (P (P Po (P a) R U SS IA N R NA P A R Lake Hennessey Lake Berryessa Lake Sonoma Clear Lake Yountville Winters Windsor Sebastopol Pope Valley Occidental Monte Rio Kelseyville Healdsburg Geyserville Forestville Esparto Cloverdale Clearlake Oaks Calistoga Arbuckle Angwin Jimtown Lake Lower 101 175 128 20 12 29 53 281 16 116 121 505 5 5 Kilometers 5 Miles JIMTOWN HEALDSBURG MARK WEST SPRINGS HIGHLAND SPRINGS ASTI GEYSERVILLE GUERNEVILLE KELSEYVILLE THE GEYSERS CLEAR LAKE HIGHLANDS WHISPERING PINES MOUNT SAINT HELENA LOWER LAKE MIDDLETOWN CALISTOGA WILSON VALLEY JERICHO VALLEY AETNA SPRINGS SAINT HELENA DETERT RESERVOIR GLASCOCK MTN WALTER SPRINGS RUMSEY KNOXVILLE CHILES VALLEY GUINDA BROOKS LAKE BERRYESSA WILDWOOD SCHOOL BIRD VALLEY MONTICELLO DAM ESPARTO Colusa County Yolo County Mendocino County Sonoma County Lake County Napa County Solano County Napa County 123° 122° 39° 38°30’ Mapping completed under STATEMAP FY 2009-10 Current project FY 2010-11 Geyserville 7.5-Minute Quadrangle 122°52'30" 123°00' 38°45' 38°37’30” SOURCES OF MAP DATA 1. Quaternary geology from Gutierrez, this study; partially modified from Knudsen and others, 2000. 2. Bedrock geology compiled and modified from Blake and others, 2002; Gealey, 1951. 1 1 1 1 2 2 2 Blake, M.C., 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, scale 1:100,000. Blake, M.C., Irwin, W.P., and Coleman, R.G., 1967, Upside-down metamorphic zonation, blueschist facies along a regional thrust in California and Oregon: U.S. Geological Survey Professional Paper 575-C, pp. 1-9. Blake, M.C., Wright, R.H., and Wentworth, C.M., 1971, Preliminary geologic map of western Sonoma County and northernmost Marin County, California: U.S. Geological Survey, Open-File Report OF-71-44, scale 1:62,500. Bryant, W.A., 1982, Fault Evaluation Report FER-135, Chianti, Healdsburg, Alexander, Maacama, and related faults: California Division of Mines and Geology, 21p. California Division of Mine and Geology, 1983, Geyserville quadrangle, Special Studies Zones, revised official map: State of California, effective July 1, 1983, 1 sheet, scale 1:24,000. Cardwell, G.T., 1958, Geology and groundwater in the Santa Rosa and Petaluma Valley areas, Sonoma County, California: U.S. Geological Survey Water Supply Paper 1427. Delattre, M.P., and McLaughlin, R.J., 2010, Geologic Map of the Jimtown 7.5’ quadrangle, Sonoma County, California: California Geological Survey, scale 1:24,000; http://www.conservation.ca.gov/cgs/maps/Pages/Maps.aspx. Delattre, M.P., 2011, Preliminary Geologic Map of the Healdsburg 7.5’ quadrangle, Sonoma County, California: California Geological Survey, scale 1:24,000; http://www.conservation.ca.gov/cgs/maps/Pages/Maps.aspx. Gealey, W.K., 1951, Geology of the Healdsburg quadrangle, California: California Division of Mines Bulletin 162, 50 p., Plate 1, scale 1:62,500. 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. Knudsen, K.L., Sowers, J.M., Witter, R.C., Wentworth, C.M., and Helley, E.J., 2000, Preliminary maps of Quaternary deposits and liquefaction susceptibility, none-county San Francisco Bay region, California: A digital database: U.S. Geological Survey Open-File Report 00-444, scale 1:24,000; http://pubs.usgs.gov/of/2000/of00-444/ 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. http://pubs.usgs.gov/of/2008/1009/ McLaughlin, R.J., and Sarna-Wojcicki, Andrei, 2003, Geology of the right step-over region between the Rodgers Creek, Healdsburg, and Maacama faults, Northern San Francisco Bay Region - A contribution to northern California Geological Society Field Trip Guide, June 6-8, 2003: U.S. Geological Survey Open-File Report 03-502, 23 p. http://pubs.usgs.gov/of/2003/of03-502/ Metzger, L.F., Farrar, C.D., Koczot, K.M., and Reichard, E.G., 2006, Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California: U.S. Geological Survey Scientific Investigations Report 2006-5115, 83 p. 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; http://pubs.usgs.gov/of/2006/1037/ SELECTED REFERENCES Inclined Vertical Overturned SYMBOL EXPLANATION Contact between map units – Solid where accurately located; dashed where approximately located; dotted where concealed, queried where uncertain. Landslide - arrows indicate principal direction of movement. Fault – Solid where accurately located, dashed where approximately located; short dash where inferred; dotted where concealed; queried where uncertain. ? ? Strike and dip of beds 25 25 KJfmg Kfss Jfgs KJfs KJfc Kfgwy alf adf af Qhc Qhay Qhfy Qha Qpa Qa Qls Qoa ? ? ? Qhf Qpf Qf ? Qpt Qt ? sc QTg Tsvb ? Franciscan Complex ? ? ? Holocene Pleistocene Pliocene QUATERNARY TERTIARY CORRELATION OF MAP UNITS Great Valley Sequence Coast Range Ophiolite sp Jv Jd spm KJgv KJgvc KJgvs KJfms CRETACEOUS JURASSIC TKfs KJfm ? ch gs m Artificial fill (historical) – May be engineered and/or non-engineered Artificial dam fill (historical) – Earth dams, rock-fill dams, and embankments constructed to impound water. May be engineered and/or non-engineered. Artificial levee fill (historical) – Artificial levees constructed along rivers and streams to control flood waters. May be engineered and/or non-engineered. 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; composed of loose sand, silt, clay and gravel. Alluvial fan deposits (latest Holocene) – Alluvial fan sediment deposited on the modern alluvial valley. Sediments are typically moderately to poorly sorted and bedded, and consist of gravel, sand, silt, and clay. Alluvial deposits, undivided (Holocene) – Alluvium deposited in fan, terrace, or basin environments that could not be readily separated for mapping. Sediments are typically poorly to moderately sorted, and consist of sand, silt, and gravel that form smooth geomorphic surfaces with little to no dissection. Alluvial fan deposits (Holocene) – Sediment deposited by streams emanating from canyons to produce relatively undissected, fan-shaped deposits on alluvial valley floors. Sediments are typically moderately to poorly sorted, and consist of sand, gravel, silt, and occasionally clay. 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. Alluvial fan deposits (Holocene to latest Pleistocene) – Sediment deposited by streams emanating from canyons to produce slightly to moderately undissected, fan-shaped deposits on alluvial valley floors. Sediments are typically moderately to poorly sorted, and consist of sand, gravel, silt, and occasionally clay. Stream terrace deposits (Holocene to latest Pleistocene) – Relatively flat or gently sloping surfaces with slightly to moderately weathered, and slightly to moderately dissected deposits of sand, gravel, silt, and minor clay. Landslide deposits (historical to Pleistocene) – Arrows indicate direction of movement; queried where landslide existence is questionable. Alluvial deposits, undivided (late Pleistocene) – Moderately to highly dissected, poorly to moderately sorted deposits of sand, silt, and gravel. Alluvial fan deposits (late Pleistocene) – Sediment deposited by streams emanating from canyons to produce fan-shaped deposits on alluvial valley floors. Sediments are moderately to highly dissected, typically moderately to poorly sorted, and consist of sand, gravel, silt, and occasionally clay. Terrace deposits (late Pleistocene) – Orange to red-stained, poorly sorted sand and gravel with clasts that vary from subangular to well-rounded and up to cobble size. Deposits generally consists of a variety of both Tertiary volcanic and basement lithologies. Age estimated from degree of iron oxide staining and weathering, dissection, and elevation above active channel. Older alluvial deposits, undivided (Pleistocene) – Highly dissected alluvial fan, channel and terrace deposits consisting of poorly to moderately sorted, sand, silt, and gravel. Unnamed fluvial deposits (early Pleistocene to Pliocene) – Light-brown to yellow- brown, weakly consolidated gravel, tuffaceous sand, silt, clay, and reworked tuff. Clasts are derived from Tertiary volcanic and Franciscan basement rocks. Includes gravels previously mapped as Glen Ellen; name not used here because of unreliable lithologic and age criteria for distinguishing between the units and correlation with the formation type localities (McLaughlin and others, 2008). Silica carbonate rock (Pleistocene and Pliocene) – Hydrothermally altered ultramafic rocks that consist of varying proportions of quartz and magnesium carbonate mineral assemblages. Color is variable and may include shades of white, green, red, brown and yellow. Sonoma Volcanics, andesite, basaltic andesite, and basalt (Pliocene to Miocene) – Dark-gray to dark-brownish-gray flows and flow breccias, phenocrysts of olivine and plagioclase; locally vessicluar. Franciscan Complex – Central Belt Sandstone (late Eocene to Late Cretaceous) – 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). Sandstone (Late Cretaceous) – Massive to distinctly bedded, brown-weathering, greenish-gray, white mica- and K-feldspar-bearing feldspathic-lithic wacke and dark-gray shale; locally, the sandstone exhibits incipient foliation. Age based on similarity to fossil-bearing sandstone outside the study area (Blake and others, 2002). Sandstone (Late and Early Cretaceous) – Thin-bedded to massive, buff-weathering, graywacke and minor interbedded black shale; locally interbedded with chert and greenstone. Distinguished from other Cretaceous Franciscan sandstones by the large amount of lithic detritus and apparent lack of K-feldspar (Blake and others, 2002). Chert (Cretaceous and Jurassic) – Thin-bedded red chert with buff-weathering, dark-gray shale and slate partings (Blake and others, 2002). Franciscan graywacke and mélange, undivided (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 gradational contacts, and/or size relative to map scale. Franciscan 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. Individually mapped blocks differentiated as follows: Chert – Red, green, and white, thin-bedded chert, with minor interbedded shale and tuff; frequently intermingled with greenstone. Greenstone – Variably altered and sheared basalt, flow breccias, tuff, and diabase. Dark greenish- gray to black, weathered dark-brown to orange, predominantly massive, occasionally vesicular, or with pillow structure preserved. High-grade metamorphic rock – Includes metabasalt and metasediments with phyllitic to gneissose texture; largely blueschist grade, and amphibolite to eclogite partially retrograded to blueschist. Greenstone (Jurassic) – Massive and pillowed basalt metamorphosed to greenstone. Amygdaloidal in places. Franciscan Complex – Eastern Belt Metagraywacke (Cretaceous and Jurassic) – Fine- to coarse-grained, highly reconstituted (textural zone 2 to 3 of Blake and others, 1967), white mica- and glaucophane-bearing metagraywacke, with minor interbeds of low blueschist grade metachert and greenstone. Metabasalt (Cretaceous and Jurassic) – Green, glaucophane-muscovite-lawsonite- sphene-bearing, non-foliated metabasalt, and greenstone. Great Valley Sequence Mudstone, sandstone and conglomerate, undivided (Early Cretaceous and Late Jurassic). Conglomerate (Early Cretaceous and Late Jurassic) – Predominantly massive, gray to brown cobble conglomerate, with minor thin interbeds of mudstone and sandstone. Clasts are generally rounded to well-rounded, composed of distinctive light-colored rhyolite porphyry, along with welded tuff, quartzite, greenstone, chert, serpentine, and vein quartz. Mudstone, shale, and sandstone (Early Cretaceous and Late Jurassic) – Dark-gray to black marine mudstone and shale, with occasional thin interbeds and thicker intervals of greenish-gray sandstone. Sporadic, concretionary carbonate beds locally include Tithonian to Valanginian buchia, belemnites, and radiolarians. Coast Range Ophiolite Mafic and intermediate volcanic rocks (Late and Middle Jurassic) – Mostly massive, dark-green to gray, aphanitic basalt with amygduloidal and plagioclase-porphyry basalt, and pillow basalt. Also includes diabase, keratophyre, and amygduloidal and plagioclase-hornblende-porphyry andesite (Blake and others, 2002). Mafic and intermediate intrusive rocks (Late and Middle Jurassic) – Diabase, gabbro, and diorite. Also includes minor intrusive keratophyre (Blake and others, 2002). Serpentinite (Late and Middle Jurassic) – Highly sheared, variably serpentinized ultramafic rocks. Occurs mostly along faults and shear zones, or as isolated blocks within Franciscan mélange and graywacke. Serpentinite matrix mélange (Late and Middle Jurassic) – Fault-bounded slivers of sheared serpentinite enclosing blocks of graywacke, greenstone, metachert, and high-grade metamorphic rocks. KJgv KJgvc KJgvs KJfms KJfmg sp spm Jv Jd af Qhf Qf Qt Qa Qhay Qhfy Qhc Qha Qls Qoa Qpt Qpf Qpa Tsvb KJfs TKfs Kfss Kfgwy KJfc QTg adf alf sc Jfgs DESCRIPTION OF MAP UNITS KJfm ch gs m STATE OF CALIFORNIA - EDMUND G. BROWN JR., GOVERNOR THE NATURAL RESOURCES AGENCY - JOHN LAIRD, SECRETARY FOR NATURAL RESOURCES DEPARTMENT OF CONSERVATION - MARK NECHODOM, CONSERVATION DIRECTOR CALIFORNIA GEOLOGICAL SURVEY JOHN G. PARRISH, Ph.D., STATE GEOLOGIST PRELIMINARY GEOLOGIC MAP OF THE GEYSERVILLE 7.5’ QUADRANGLE, CALIFORNIA PRELIMINARY GEOLOGIC MAP OF THE GEYSERVILLE 7.5' QUADRANGLE SONOMA COUNTY, CALIFORNIA: A DIGITAL DATABASE VERSION 1.0 By Carlos I. Gutierrez, Peter J. Holland, and Marc P. Delattre Digital Database by Carlos I. Gutierrez and Matt O’Neal 2012 This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program, Statemap Award no. G11AC20220 38°45' 122°52'30” 38°37'30” 122°52'30” 38°45' 38°37’30” 123°00' Projection: Universal Transverse Mercator, Zone 10N, North American Datum 1927. Topographic base from U.S. Geological Survey Geyserville 7.5-minute Quadrangle, 1993. Shaded relief image derived from USGS 1/3 arc-second National Elevation Dataset (NED). 123°00' Copyright © 2012 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." Preliminary Geologic Map available from: http://www.conservation.ca.gov/cgs/rghm/rgm/preliminary_geologic_maps.htm Professional Licenses and Certifications: C.I. Gutierrez - PG No. 8686; P.J. Holland - PG No. 7994, CEG No. 2400; M.P. Delattre - PG No. 5230, CEG No. 1819

Transcript of Preliminary Geologic Map available from: PRELIMINARY ... · Jv KJgvs Jd Jv 0 0 0 1 1.5 1.5 2 2 2...

Page 1: Preliminary Geologic Map available from: PRELIMINARY ... · Jv KJgvs Jd Jv 0 0 0 1 1.5 1.5 2 2 2 Thousand Feet Kilometers Miles Scale 1:24,000 Contour Interval 40 feet Supplementary

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Colusa CountyYolo County

Mendocino CountySonoma County

Lake County

Napa County

Solano County

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123° 122°39°

38°30’

Mapping completed under STATEMAP

FY 2009-10 Current project

FY 2010-11

Geyserville 7.5-Minute Quadrangle122°52'30"123°00'

38°45'

38°37’30”

SOURCES OF MAP DATA

1. Quaternary geology from Gutierrez, this study; partially modified from Knudsen and others, 2000.

2. Bedrock geology compiled and modified from Blake and others, 2002; Gealey, 1951.

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Blake, M.C., 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, scale 1:100,000.

Blake, M.C., Irwin, W.P., and Coleman, R.G., 1967, Upside-down metamorphic zonation, blueschist facies along a regional thrust in California and Oregon: U.S. Geological Survey Professional Paper 575-C, pp. 1-9.

Blake, M.C., Wright, R.H., and Wentworth, C.M., 1971, Preliminary geologic map of western Sonoma County and northernmost Marin County, California: U.S. Geological Survey, Open-File Report OF-71-44, scale 1:62,500.

Bryant, W.A., 1982, Fault Evaluation Report FER-135, Chianti, Healdsburg, Alexander, Maacama, and related faults: California Division of Mines and Geology, 21p.

California Division of Mine and Geology, 1983, Geyserville quadrangle, Special Studies Zones, revised official map: State of California, effective July 1, 1983, 1 sheet, scale 1:24,000.

Cardwell, G.T., 1958, Geology and groundwater in the Santa Rosa and Petaluma Valley areas, Sonoma County, California: U.S. Geological Survey Water Supply Paper 1427.

Delattre, M.P., and McLaughlin, R.J., 2010, Geologic Map of the Jimtown 7.5’ quadrangle, Sonoma County, California: California Geological Survey, scale 1:24,000; http://www.conservation.ca.gov/cgs/maps/Pages/Maps.aspx.

Delattre, M.P., 2011, Preliminary Geologic Map of the Healdsburg 7.5’ quadrangle, Sonoma County, California: California Geological Survey, scale 1:24,000; http://www.conservation.ca.gov/cgs/maps/Pages/Maps.aspx.

Gealey, W.K., 1951, Geology of the Healdsburg quadrangle, California: California Division of Mines Bulletin 162, 50 p., Plate 1, scale 1:62,500.

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.

Knudsen, K.L., Sowers, J.M., Witter, R.C., Wentworth, C.M., and Helley, E.J., 2000, Preliminary maps of Quaternary deposits and liquefaction susceptibility, none-county San Francisco Bay region, California: A digital database: U.S. Geological Survey Open-File Report 00-444, scale 1:24,000; http://pubs.usgs.gov/of/2000/of00-444/

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. http://pubs.usgs.gov/of/2008/1009/

McLaughlin, R.J., and Sarna-Wojcicki, Andrei, 2003, Geology of the right step-over region between the Rodgers Creek, Healdsburg, and Maacama faults, Northern San Francisco Bay Region - A contribution to northern California Geological Society Field Trip Guide, June 6-8, 2003: U.S. Geological Survey Open-File Report 03-502, 23 p. http://pubs.usgs.gov/of/2003/of03-502/

Metzger, L.F., Farrar, C.D., Koczot, K.M., and Reichard, E.G., 2006, Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California: U.S. Geological Survey Scientific Investigations Report 2006-5115, 83 p.

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; http://pubs.usgs.gov/of/2006/1037/

SELECTED REFERENCES

Inclined

Vertical

Overturned

SYMBOL EXPLANATION

Contact between map units – Solid where accurately located; dashed whereapproximately located; dotted where concealed, queried where uncertain.

Landslide - arrows indicate principal direction of movement.

Fault – Solid where accurately located, dashed where approximately located;short dash where inferred; dotted where concealed; queried where uncertain.

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Strike and dip of beds25

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Franciscan Complex

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Holocene

Pleistocene

Pliocene

QUATERNARY

TERTIARY

CORRELATION OF MAP UNITS

Great ValleySequence

Coast Range Ophiolite

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KJgvs

KJfmsCRETACEOUS

JURASSIC

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Artificial fill (historical) – May be engineered and/or non-engineered

Artificial dam fill (historical) – Earth dams, rock-fill dams, and embankments constructed to impound water. May be engineered and/or non-engineered.

Artificial levee fill (historical) – Artificial levees constructed along rivers and streams to control flood waters. May be engineered and/or non-engineered.

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; composed of loose sand, silt, clay and gravel.

Alluvial fan deposits (latest Holocene) – Alluvial fan sediment deposited on the modern alluvial valley. Sediments are typically moderately to poorly sorted and bedded, and consist of gravel, sand, silt, and clay.

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

Alluvial fan deposits (Holocene) – Sediment deposited by streams emanating from canyons to produce relatively undissected, fan-shaped deposits on alluvial valley floors. Sediments are typically moderately to poorly sorted, and consist of sand, gravel, silt, and occasionally clay.

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.

Alluvial fan deposits (Holocene to latest Pleistocene) – Sediment deposited by streams emanating from canyons to produce slightly to moderately undissected, fan-shaped deposits on alluvial valley floors. Sediments are typically moderately to poorly sorted, and consist of sand, gravel, silt, and occasionally clay.

Stream terrace deposits (Holocene to latest Pleistocene) – Relatively flat or gently sloping surfaces with slightly to moderately weathered, and slightly to moderately dissected deposits of sand, gravel, silt, and minor clay.

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

Alluvial deposits, undivided (late Pleistocene) – Moderately to highly dissected, poorly to moderately sorted deposits of sand, silt, and gravel.

Alluvial fan deposits (late Pleistocene) – Sediment deposited by streams emanating from canyons to produce fan-shaped deposits on alluvial valley floors. Sediments are moderately to highly dissected, typically moderately to poorly sorted, and consist of sand, gravel, silt, and occasionally clay.

Terrace deposits (late Pleistocene) – Orange to red-stained, poorly sorted sand and gravel with clasts that vary from subangular to well-rounded and up to cobble size. Deposits generally consists of a variety of both Tertiary volcanic and basement lithologies. Age estimated from degree of iron oxide staining and weathering, dissection, and elevation above active channel.

Older alluvial deposits, undivided (Pleistocene) – Highly dissected alluvial fan, channel and terrace deposits consisting of poorly to moderately sorted, sand, silt, and gravel.

Unnamed fluvial deposits (early Pleistocene to Pliocene) – Light-brown to yellow- brown, weakly consolidated gravel, tuffaceous sand, silt, clay, and reworked tuff. Clasts are derived from Tertiary volcanic and Franciscan basement rocks. Includes gravels previously mapped as Glen Ellen; name not used here because of unreliable lithologic and age criteria for distinguishing between the units and correlation with the formation type localities (McLaughlin and others, 2008).

Silica carbonate rock (Pleistocene and Pliocene) – Hydrothermally altered ultramafic rocks that consist of varying proportions of quartz and magnesium carbonate mineral assemblages. Color is variable and may include shades of white, green, red, brown and yellow.

Sonoma Volcanics, andesite, basaltic andesite, and basalt (Pliocene to Miocene) – Dark-gray to dark-brownish-gray flows and flow breccias, phenocrysts of olivine and

plagioclase; locally vessicluar.

Franciscan Complex – Central Belt

Sandstone (late Eocene to Late Cretaceous) – 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).

Sandstone (Late Cretaceous) – Massive to distinctly bedded, brown-weathering, greenish-gray, white mica- and K-feldspar-bearing feldspathic-lithic wacke and dark-gray shale; locally, the sandstone exhibits incipient foliation. Age based on similarity to fossil-bearing sandstone outside the study area (Blake and others, 2002).

Sandstone (Late and Early Cretaceous) – Thin-bedded to massive, buff-weathering, graywacke and minor interbedded black shale; locally interbedded with chert and greenstone. Distinguished from other Cretaceous Franciscan sandstones by the large amount of lithic detritus and apparent lack of K-feldspar (Blake and others, 2002).

Chert (Cretaceous and Jurassic) – Thin-bedded red chert with buff-weathering, dark-gray shale and slate partings (Blake and others, 2002).

Franciscan graywacke and mélange, undivided (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 gradational contacts, and/or size relative to map scale.

Franciscan 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. Individually mapped blocks differentiated as follows:

Chert – Red, green, and white, thin-bedded chert, with minor interbedded shale and tuff; frequently intermingled with greenstone.

Greenstone – Variably altered and sheared basalt, flow breccias, tuff, and diabase. Dark greenish- gray to black, weathered dark-brown to orange, predominantly massive, occasionally vesicular, or with pillow structure preserved.

High-grade metamorphic rock – Includes metabasalt and metasediments with phyllitic to gneissose texture; largely blueschist grade, and amphibolite to eclogite partially retrograded to blueschist.

Greenstone (Jurassic) – Massive and pillowed basalt metamorphosed to greenstone. Amygdaloidal in places.

Franciscan Complex – Eastern Belt

Metagraywacke (Cretaceous and Jurassic) – Fine- to coarse-grained, highly reconstituted (textural zone 2 to 3 of Blake and others, 1967), white mica- and glaucophane-bearing metagraywacke, with minor interbeds of low blueschist grade metachert and greenstone.

Metabasalt (Cretaceous and Jurassic) – Green, glaucophane-muscovite-lawsonite- sphene-bearing, non-foliated metabasalt, and greenstone.

Great Valley Sequence

Mudstone, sandstone and conglomerate, undivided (Early Cretaceous and Late Jurassic).

Conglomerate (Early Cretaceous and Late Jurassic) – Predominantly massive, gray to brown cobble conglomerate, with minor thin interbeds of mudstone and sandstone. Clasts are generally rounded to well-rounded, composed of distinctive light-colored rhyolite porphyry, along with welded tuff, quartzite, greenstone, chert, serpentine, and vein quartz.

Mudstone, shale, and sandstone (Early Cretaceous and Late Jurassic) – Dark-gray to black marine mudstone and shale, with occasional thin interbeds and thicker intervals of greenish-gray sandstone. Sporadic, concretionary carbonate beds locally include Tithonian to Valanginian buchia, belemnites, and radiolarians.

Coast Range Ophiolite

Mafic and intermediate volcanic rocks (Late and Middle Jurassic) – Mostly massive, dark-green to gray, aphanitic basalt with amygduloidal and plagioclase-porphyry basalt, and pillow basalt. Also includes diabase, keratophyre, and amygduloidal and plagioclase-hornblende-porphyry andesite (Blake and others, 2002).

Mafic and intermediate intrusive rocks (Late and Middle Jurassic) – Diabase, gabbro, and diorite. Also includes minor intrusive keratophyre (Blake and others, 2002).

Serpentinite (Late and Middle Jurassic) – Highly sheared, variably serpentinized ultramafic rocks. Occurs mostly along faults and shear zones, or as isolated blocks within Franciscan mélange and graywacke.

Serpentinite matrix mélange (Late and Middle Jurassic) – Fault-bounded slivers of sheared serpentinite enclosing blocks of graywacke, greenstone, metachert, and high-grade metamorphic rocks.

KJgv

KJgvc

KJgvs

KJfms

KJfmg

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Qhf

Qf

Qt

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Qhc

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Qls

Qoa

Qpt

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KJfs

TKfs

Kfss

Kfgwy

KJfc

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DESCRIPTION OF MAP UNITS

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STATE OF CALIFORNIA - EDMUND G. BROWN JR., GOVERNORTHE NATURAL RESOURCES AGENCY - JOHN LAIRD, SECRETARY FOR NATURAL RESOURCES

DEPARTMENT OF CONSERVATION - MARK NECHODOM, CONSERVATION DIRECTOR CALIFORNIA GEOLOGICAL SURVEYJOHN G. PARRISH, Ph.D., STATE GEOLOGIST PRELIMINARY GEOLOGIC MAP OF THE GEYSERVILLE 7.5’ QUADRANGLE, CALIFORNIA

PRELIMINARY GEOLOGIC MAP OF THEGEYSERVILLE 7.5' QUADRANGLE

SONOMA COUNTY, CALIFORNIA: A DIGITAL DATABASEVERSION 1.0

ByCarlos I. Gutierrez, Peter J. Holland, and Marc P. Delattre

Digital Database by

Carlos I. Gutierrez and Matt O’Neal

2012

This geologic map was funded in part by the USGS National Cooperative Geologic MappingProgram, Statemap Award no. G11AC20220

38°45'122°52'30”

38°37'30”122°52'30”

38°45'

38°37’30”123°00'

Projection: Universal Transverse Mercator, Zone 10N, North American Datum 1927.

Topographic base from U.S. Geological SurveyGeyserville 7.5-minute Quadrangle, 1993.Shaded relief image derived from USGS 1/3 arc-second National Elevation Dataset (NED).

123°00'

Copyright © 2012 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."

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

Professional Licenses and Certifications: C.I. Gutierrez - PG No. 8686; P.J. Holland - PG No. 7994, CEG No. 2400; M.P. Delattre - PG No. 5230, CEG No. 1819