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W I L M A R A V E N U E F A U L T
O C E A N O FA U LT
OC
E A NO
FA U
LT
0
0
0
1
1
1.5
.5 2
2
2Thousand Feet
Kilometers
Miles
Scale 1:24,000
Contour Interval 20 feetSupplementary Contour Interval 10 feet
National Geodetic Vertical Datum of 1929
MN
GN
UTM GRID AND 2013 MAGNETIC NORTHDECLINATION AT CENTER OF SHEET
235 MILS
25 MILS
13°13’
1°24’
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 OCEANO 7.5’ QUADRANGLE, CALIFORNIA
Copyright © 2013 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 OF THEOCEANO 7.5' QUADRANGLE
SAN LUIS OBISPO COUNTY, CALIFORNIA: A DIGITAL DATABASEVERSION 1.0
By Peter J. Holland
Digital Preparation by
Peter J. Holland and Matt D. O’Neal
2013
This geologic map was funded in part by the USGS National Cooperative Geologic MappingProgram, Statemap Award no. G12AC20278
35°7'30''120°30'
35°35°120°30'
35°7'30''
Projection: Universal Transverse Mercator, Zone 10N, North American Datum 1927.
Topographic base from U.S. Geological SurveyOceano 7.5-minute Quadrangle, 1979.Shaded relief image derived from USGS 1/3 arc-second National Elevation Dataset (NED).
120°38'30''
120°38'30''
Professional Licenses and Certifications: P.J. Holland, PG No. 7994, CEG No. 2400
Preliminary Geologic Map available from:http://www.conservation.ca.gov/cgs/rghm/rgm/preliminary_geologic_maps.htm
120°37'30''
120°37'30''
(Paso Robles) - Adjacent 30’ x 60’ quadrangles
Santa Margarita Lake
Lopez Lake
Twitchell Reservoir
Twitchell Res
Santa Maria River135
58
41229
227
166
46
1
101
SantaMaria5
Kilometers5
Miles
CAYUCOS
MORROBAYNORTH
MORROBAYSOUTH
PORTSAN LUIS
PISMOBEACH
SAN LUISOBISPO
ARROYOGRANDE NE
LOPEZMTN
TARSPRINGRIDGE
CALDWELLMESA
LOSMACHOSHILLS
BRANCHMTN
MIRANDAPINEMTN
HUASNAPEAK
NIPOMO
OCEANO
CHIMNEYCANYON
SANTAMARGARITA
SANTAMARGARITALAKE
WILSONCORNER
CAMATTARANCH
POZOSUMMIT
LA PANZARANCH
LA PANZA
CALIFORNIAVALLEY
LA PANZANE
ATASCADERO
(P(P(P(Pasassaso Roblleses)))(Paso Robles)
(Paso Robles) - Adjacent 30’ x 60’ quadrangles
(T(T(T(T(TTaft)Taft)
(S(S(S(S(S(S(S((S(S(S( anananananantatttatta MMMMaria)(S(Sananta MMaria) Mapping completed under STATEMAP
PREVIOUS YEARS
CURRENT YEAR
FY 2008-09
FY 2010-11
FY 2009-10
FY 2011-12
FY 2012-13
FY 2012-13
121°0’0” 120°30’0” 120°0’0”
35°3
0’0”
35°0
’0”
MAP SYMBOLS
Strike and dip of bedding plane.
Horizontal Bedding
Sand boil caused by 2003 M6.5 San Simeon earthquake
Lateral spread extensional features caused by 2003 M6.5 San Simeon earthquake
Lateral spread compressional features caused by 2003 M6.5 San Simeon earthquake
30
Synclinal axis - Solid where accurately located, dashed where approximately located, dotted where concealed. Arrow shows plunge direction. Anticlinal axis - Solid where accurately located, dashed where approximately located, dotted where concealed. Arrow shows plunge direction.
Contact between map units - Solid where accurately located, dashed where approximately located, dotted where concealed.
Fault - Solid where accurately located, dashed where approximately located, dotted where concealed. U = upthrown block; D = downthrown block.
X
California Department of Water Resources, 2002, Water Resources of the Arroyo Grande – Nipomo Mesa Area, Southern District Report.
Dibblee, T.W. Jr., 2006, Geologic Map of the Oceano Quadrangle, San Luis Obispo County, California: Dibblee Geology Center Map #DF-209, Scale 1:24,000
Hall, C.A., 1973, Geology of the Arroyo Grande 15’ quadrangle, San Luis Obispo County, California: California Division of Mines and Geology Map Sheet 24, Scale 1:48,000
Holzer, T.L., Noce, T.E., Bennett, M.J., Di Alessandro, C., Boatwright, J., Tinsley, III, J.C., Sell, R.W., Rosenberg, L.I., 2004, Liquefaction-induced lateral spreading in Oceano, California, during the 2003 San Simeon Earthquake. USGS Open-File Report 2004-1269, 51 pp.
Knott, J.R. and Eley, D.S., 2006, Early to Middle Holocene Coastal Dune and Estuarine Deposition, Santa Maria Valley, California, Physical Geography, 27, 2, pp. 127-136.
Lettis, W.R. and Hall, N.T., 1994, Los Osos Fault Zone, San Luis Obispo County, California in Alterman, I.B., McMullen, R.B., Cluff, L.S., and Slemmons, D.B., editors, Seismotectonics of the Central California Coast Ranges: Geological Society of America Special Paper 292, p. 73-102.
Nitchman, S.P., 1988, Tectonic geomorphology and neotectonics of the San Luis Range, San Luis Obispo County, California: University of Nevada, Reno, M.S. thesis, 120 pp.
Hanson, K.L., Wesling, J.R., Lettis, W.R., Kelson, K.I., and Mezger, L., 1994, Correlation, Ages and Uplift Rates of Quaternary Marine Terraces: South-Central Coastal California in Alterman, I.B., McMullen, R.B., Cluff, L.S., and Slemmons, D.B., editors, Seismotectonics of the Central California Coast Ranges: Geological Society of America Special Paper 292, p. 45 - 72.
REFERENCES
SURFICIAL DEPOSITS
Artificial fill (historic) - various amounts of fill along levees and highway and railroad embankments.
Stream channel deposits (late Holocene) - Unconsolidated sand, gravel and cobbles in active channels.
Alluvial flood-plain deposits (late Holocene) - Active and recently active flood-plain deposits. Consists of unconsolidated sandy, silty, and clay-bearing alluvium.
Beach sand (late Holocene) – Unconsolidated beach deposits consisting mostly of fine- to medium-grained well-sorted sand.
Dune sand (late Holocene) – Unconsolidated, well-sorted white to brown windblown sand. Forms active dunes behind modern beaches.
Landslide deposits (Holocene to late Pleistocene) – Highly fragmented to largely coherent landslide deposits.
Young eolian deposits (Holocene) – Vegetated stationary sand dune deposits displaying dune morphology. Well-sorted white to brown windblown sand. Inception of dune sheet occurred at approximately 3.5 to 4.3 ka (Knott and Eley, 2006).
Young alluvial valley deposits, undivided (Holocene to late Pleistocene) – Unconsolidated sand, silt, and clay-bearing alluvium deposited on flood-plains and along valley floors. Surfaces are slightly dissected and display weak soil development. Approximately 4.3 to 11 ka in the Santa Maria Valley (Knott and Eley, 2006).
Old eolian deposits (late Pleistocene) – well sorted red to brown wind blown sand with weak soil development in places. Surfaces are dissected and dune morphology is generally obscured.
Older alluvium (late to middle Pleistocene) – Unconsolidated boulders, cobbles, gravel, sand, silt and clay poorly to moderately sorted; some discontinuous horizontal bedding, weakly to strongly cemented horizons (duripans) present locally, clasts generally consist of Franciscan Complex, Obispo and Monterey Formation lithologies.
Marine deposits (middle to late Pleistocene) – Unconsolidated, well to moderately sorted cobbles and sand; clasts are typically subrounded to rounded and consist of Franciscan Complex, Obispo and Monterey Formation lithologies. (Hansen, et al, 1994).
TERTIARY AND OLDER ROCKS
Pismo Formation, Squire member (lower Pliocene) – Massive, white to light gray, fine- to medium-grained, quartzose to arkosic silty sandstone. Sand grains subrounded to subangular, 75-80% quartz, 15-20% feldspar, less than 15% mafic minerals (Hall, 1973).
Monterey Formation (upper to middle Miocene)
Cherty shale – Bedded, resistant chert, color varies from white and gray to brown and reddish-brown, weathering to chalky white. Brittle, conchoidal fracturing, commonly sheared, beds ½ to 6-inches thick, commonly laminated, locally interbedded with siltstone (Tms) and diatomite (Hall,1973).
Siltstone – Brown to white siltstone with some claystone.
Siltstone and dolomitic claystone – Tan to yellowish-white siltstone and dolomitic claystone locally tuffaceous or interbedded with chert.
Obispo Formation (lower Miocene) – Coarse-grained tuff with subangular clasts of pumice (5%-50%), perlite (5%-15%), white to dark-gray glass shards (20%) and feldspar (5%) in a vitric ashy matrix; locally zeolitized or silicified (Tor) and commonly altered to montmorillonite (Hall, 1973).
Zeolitized tuff – Resistant, hard, fine-grained, zeolitized or silicied tuff. Forms resistant outcrops.
Rincon Shale (Oligocene to lower Miocene) – Dark brown siltstone that is exposed in a road cut along Highway 101.
Franciscan Complex (Cretaceous to Jurassic)
Mélange – Chaotic mixture of fragmented rock masses embedded in a penetratively sheared matrix. Matrix is not exposed in the Oceano Quadrangle. Resistant blocks are exposed only within the Los Berros Creek area and include:
Greywacke
Chert
Greenstone
Serpentinite
Mélange and slope wash – Areas surrounding resistant blocks interpreted to be mélange matrix largely covered by slope wash.
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DESCRIPTION OF MAP UNITS
QoeQoa
Qm
Holocene
Pleistocene
Pliocene
Miocene
Oligocene
QUATERNARY
TERTIARY
CRETACEOUS
JURASSIC
Tms
Tor
SURFICIAL DEPOSITS
TERTIARY AND OLDER ROCKS
CORRELATION OF MAP UNITS
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Revised: 08/26/2013