Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the 

U.S. Government

This map was printed on an electronic plotter directly from digital files. Dimensional calibration may vary between electronic plotters 

and between X and Y directions on the same plotter, and paper may change size due to atmospheric conditions; therefore, scale and 

proportions may not be true on plots of this map.

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225, 1–888–ASK–USGS

Digital files available at http://pubs.usgs.gov/sim/3306/

Suggested Citation: Watt, J.T., Greene, H.G., Manson, M.W., Hartwell, S.R., Endris, C.A., Ross, S.L., Phillips, E.L., and Dieter, B.E., 2014, 

Offshore and onshore geology and geomorphology, Offshore of San Gregorio map area, California, sheet 10 in Cochrane, G.R., 

Dartnell, P., Greene, H.G., Watt, J.T., Golden, N.E., Endris, C.A., Phillips, E.L., Hartwell, S.R., Johnson, S.Y., Kvitek, R.G., Erdey, M.D., 

Bretz, C.K., Manson, M.W., Sliter, R.W., Ross, S.L., Dieter, B.E., and Chin, J.L. (G.R. Cochrane and S.A. Cochran, eds.), California State 

Waters Map Series—Offshore of San Gregorio, California: U.S. Geological Survey Scientific Investigations Map 3306, pamphlet 38 p., 

10 sheets, scale 1:24,000, http://dx.doi.org/10.3133/sim3306.

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3306

Figure 1. Schematic map showing structural blocks within Offshore of San Gregorio 

map area. Pigeon Point block and Pigeon Point high (McCulloch, 1987) are separated 

from Santa Cruz Mountains block by Pomponio block, which is bounded by Frijoles 

Fault (to west) and Coastways Fault (to east), two strands of San Gregorio Fault Zone 

(SGFZ). Blue line shows coastline. Modified from Weber (1990).

0 1 2

Frijoles Fault (west strand of SGFZ)

SANTA CRUZ

MOUNTAINS

BLOCK

San Gregorio

State Beach

Pescadero

State Beach

axis of Pigeon Point high

San Gregorio Fault Zone

3 KILOMETERS

PIGEON POINT

BLOCK

POMPONIO

BLOCK

Coastways Fault (east strand of SGFZ)

Kilometers 0 5 10

0 5 10Nautical Miles

122°40' 122°20'

38°

37°40'

37°20'

San

Francisco

Bay

San

Francisco

Area of

Map

Limit of California’s

State Waters

CALIF.

MAP LOCATION

KJv

Kpp

Tb

Tmb

Tuv

Tsc

Tpt

Tpp

Tpsg

Tpl

Tptu

Tp

Qof

Qmt1

Qmt2

Qmt

Qoa

Qot

Qls

Qcl

Qb

Qa

Qed

Qyf

Qc

Qbs

alf

adf

afem

af

ac

Qyf

Kpp

TKu

Tpt

Tp

Qmsf

Qmss

Qmsc

Qms

REFERENCES CITED

Brabb, E.E., 1980, Preliminary geologic map of the La Honda and San Gregorio quadrangles, 

San Mateo County, California: U.S. Geological Survey Open-File Report 80–245, scale 

1:24,000.

Brabb, E.E., Graymer, R.W., and Jones, D.L., 1998, Geology of the onshore part of San Mateo 

County, California—A digital database: U.S. Geological Survey Open-File Report 98–137, 

scale 1:62,500, available at http://pubs.usgs.gov/of/1998/of98-137/.

Cacchione, D.A., Drake, D.E., Grant, W.D., and Tate, G.B., 1984, Rippled scour depressions of 

the inner continental shelf off central California: Journal of Sedimentary Petrology, v. 54, 

p. 1,280–1,291.

California Geological Survey, 1982, Alquist-Priolo earthquake fault zone map of Franklin Point 

quadrangle: California Geological Survey, State of California Special Studies Zone Map, 

scale 1:24,000, available at http://www.quake.ca.gov/gmaps/WH/regulatorymaps.htm.

California Geological Survey, 2002b, Fault evaluation reports prepared under the Alquist-Priolo 

Earthquake Fault Zoning Act, region 1, central California: California Geological Survey, 

CGS CD 2002–01, available at http://www.conservation.ca.gov/cgs/rghm/ap/ap_fer_cd/

Pages/index.aspx. 

Catuneanu, O., 2006, Principles of sequence stratigraphy: Amsterdam, Elsevier, 375 p.

Dickinson, W.R., Ducea, M., Rosenberg, L.I., Greene, H.G., Graham, S.A., Clark, J.C., Weber, 

G.E., Kidder, S., Ernst, W.G., and Brabb, E.E., 2005, Net dextral slip, Neogene San 

Gregorio–Hosgri fault zone, coastal California—Geologic evidence and tectonic 

implications: Geological Society of America Special Paper 391, 43 p. 

Gornitz, V., 2009, Sea level change, post-glacial, in Gornitz, V., ed., Encyclopedia of 

paleoclimatology and ancient environments: Springer, Encyclopedia of Earth Sciences 

Series, p. 887–893.

Hallenbeck, T.R., Kvitek, R.G., and Lindholm, J., 2012, Rippled scour depressions add 

ecologically significant heterogeneity to soft-bottom habitats on the continental shelf: 

Marine Ecology Progress Series, v. 468, p. 119–133.

Lambeck, K., and Chappell, J., 2001, Sea level change through the last glacial cycle: Science, v. 

292, p. 679–686, doi: 10.1126/science.1059549.

McCulloch, D.S., 1987, Regional geology and hydrocarbon potential of offshore Central 

California, in Scholl, D.W., Grantz, A., and Vedder, J.G., eds., Geology and resource 

potential of the continental margin of western North America and adjacent ocean 

basins—Beaufort Sea to Baja California: Circum-Pacific Council for Energy and Mineral 

Resources, Earth Science Series, v. 6, p. 353–401.

McCulloch, D.S., and Chapman, R.H., 1977, Map showing residual magnetic intensity along 

the California coast, latitude 37 degrees 30 minutes N. to latitude 34 degrees 30 minutes 

N.: U.S. Geological Survey Open-File Report 77–79, 14 plates, scale 1:25,000.

Reid, J.A., Reid, J.M., Jenkins, C.J., Zimmerman, M., Williams, S.J., and Field, M.E., 2006, 

usSEABED—Pacific Coast (California, Oregon, Washington) offshore surficial-sediment 

data release: U.S. Geological Survey Data Series 182, available at http://pubs.usgs.gov/ds/

2006/182/.

Storlazzi, C.D., Fregoso, T.A., Golden, N.E., and Finlayson, D.P., 2011, Sediment dynamics and 

the burial and exhumation of bedrock reefs along on emergent coastline as elucidated by 

repetitive sonar surveys, northern Monterey Bay, CA: Marine Geology, v. 289, p. 46–59.

U.S. Geological Survey, 2001, Six aeromagnetic surveys in Nevada and California—A web site 

for distribution of data: U.S. Geological Survey Open-File Report 2001–0145, available at 

http://pubs.usgs.gov/of/2001/ofr-01-0145/.

U.S. Geological Survey and California Geological Survey, 2010, Quaternary fault and fold 

database for the United States: U.S. Geological Survey database, accessed April 5, 2014, at 

http://earthquake.usgs.gov/hazards/qfaults/.

Weber, G.E., 1990, Late Pleistocene slip rates on the San Gregorio fault zone at Point Año 

Nuevo, San Mateo County, California, in Greene, H.G., Weber, G.E., Wright, T.L., and 

Garrison, R.E., eds., Geology and tectonics of the central California coast region—San 

Francisco to Monterey: American Association of Petroleum Geologists, Pacific Section, 

volume and guidebook, v. 67, p. 193–204.

Weber, G.E., and Lajoie, K.R., 1980, Map of Quaternary faulting along the San Gregorio Fault 

Zone, San Mateo and Santa Cruz Counties, California: U.S. Geological Survey Open-File 

Report 80–907, scale 1:24,000.

Weber, K.M., List, J.H., and Morgan, K.L.M., 2005, An operational mean high water datum for 

determination of shoreline position from topographic lidar data: U.S. Geological Survey 

Open-File Report 2005–1027, available at http://pubs.usgs.gov/of/2005/1027/.

Witter, R.C., Knudsen, K.L., Sowers, J.M., Wentworth, C.M., Koehler, R.D., Randolph, C.E., 

Brooks, S.K., and Gans, K.D., 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, available at http://pubs.usgs.gov/of/2006/

1037/.

DISCUSSION

Marine geology and geomorphology were mapped in the Offshore of San Gregorio map 

area from approximate Mean High Water (MHW) to the 3-nautical-mile limit of California’s 

State Waters. MHW is defined at an elevation of 1.46 m above the North American Vertical 

Datum of 1988 (NAVD 88) (Weber and others, 2005). Offshore geologic units were delineated 

on the basis of integrated analyses of adjacent onshore geology with multibeam bathymetry and 

backscatter imagery (sheets 1, 2, 3), seafloor-sediment and rock samples (Reid and others, 

2006), digital camera and video imagery (sheet 6), high-resolution seismic-reflection profiles 

(sheet 8), and aeromagnetic data (McCulloch and Chapman, 1977; U.S. Geological Survey, 

2001). 

Onshore geology was compiled from Brabb (1980), Weber and Lajoie (1980), California 

Geological Survey (1982, 2002b), Brabb and others (1998), and Witter and others (2006). 

The continental shelf within California’s State Waters in the Offshore of San Gregorio map 

area is shallow (less than about 55 m) and flat with a very gentle (less than 0.5°) offshore dip. 

Shelf morphology and evolution are the result of the interplay between local tectonics and 

sedimentation as sea level rose about 125 to 130 m over the last about 21,000 years (see, for 

example, Lambeck and Chappell, 2001; Gornitz, 2009), leading to the progressive eastward 

migration (a few tens of kilometers) of the shoreline and wave-cut platform and the associated 

transgressive erosion and deposition (see, for example, Catuneanu, 2006). The Offshore of San 

Gregorio map area is now an open-ocean shelf that is subjected to full, and sometimes severe, 

wave energy and strong currents. Shelf deposits are almost exclusively sand (unit Qms) at 

water depths less than 60 m, but, at greater depths in the southwestern part of the map area, they 

transition to the finer grained, muddy sediments of unit Qmsf. The boundary between units 

Qms and Qmsf is based on observations and extrapolation from sediment sampling (Reid and 

others, 2006) and camera ground-truth surveying (sheet 6). It is important to note that the 

boundary between units Qms and Qmsf should be considered transitional and approximate, as 

it likely shifts seaward or landward as a result of seasonal- to annual- to decadal-scale changes 

in sediment supply, sediment transport, and wave climate. 

Coarser grained deposits (coarse sand and gravel) of units Qmss and Qmsc are recognized primarily on the basis of their high backscatter (see sheet 3). Unit Qmsc is mapped as a 

nearshore, shore-parallel bar at water depths typically between 5 and 10 m. Unit Qmss

typically exists as erosional lags in scour depressions whose contacts with horizontal sand 

sheets of unit Qms usually are relatively sharp but, less commonly, also can be diffuse. These 

scour depressions, which generally form irregular to lenticular exposures that have abrupt 

landward contacts with bedrock, typically are a few tens of centimeters deep and range in size 

from a few tens of meters to more than 1 km2

. Such scour depressions are common along this 

stretch of the California coast (see, for example, Cacchione and others, 1984; Hallenbeck and 

others, 2012), where offshore sandy sediment is relatively thin (and, thus, is unable to fill the 

depressions) owing to low sediment supply and also to erosion and transport of sediment during 

large northwest winter swells. 

Bedrock units mapped in the offshore include two units of the upper Miocene and Pliocene 

Purisima Formation (units Tp and Tpt). Rocks of the Purisima Formation are characterized by 

their high backscatter (sheet 3), as well as their distinct bedding style (caused by differential 

erosion), which is recognized in multibeam imagery and (or) or seismic-reflection data (see 

sheets 1, 2, 8). These Tertiary rocks are underlain by, or in fault contact with, Upper Cretaceous 

basement rocks, including sedimentary rocks of the Pigeon Point Formation (unit Kpp). The 

Pigeon Point Formation is mapped on the basis of its high backscatter, its massive and (or) 

rugged texture on multibeam imagery (sheets 1, 2), and its reflection-free character on seismicreflection profiles (sheet 8). Offshore outcrops of the Pigeon Point Formation expose part of the 

Pigeon Point high (McCulloch, 1987). 

In areas where bedrock is exposed on the seafloor but where less certainty exists regarding 

age, the undivided Cretaceous and Tertiary bedrock unit (TKu) is mapped. This undivided 

bedrock unit may include rocks of the Upper Cretaceous Pigeon Point Formation, the Oligocene 

and Miocene unnamed sedimentary and volcanic rocks unit (Tuv) (mapped onland near the 

mouth of Pescadero Creek), or the upper Miocene and Pliocene Purisima Formation. 

In areas where shelf sediments form thin (less than 2.5 m) veneers over low-relief rocks of 

the undivided Cretaceous and Tertiary bedrock unit or the upper Miocene and Pliocene 

Purisima Formation, composite units Qms/TKu and Qms/Tp are mapped. These composite 

units are recognized on the basis of the combination of flat relief, continuity with moderate- to 

high-relief bedrock outcrops, high-resolution seismic-reflection data (sheet 8), and (in some 

cases) moderate to high backscatter. Overlying sediment is interpreted as an ephemeral and 

dynamic sediment layer that may or may not be continuously present, depending on storms, 

seasonal and (or) annual patterns of sediment movement, or longer term climate cycles. 

Storlazzi and others (2011) described the seasonal burial and exhumation of submerged bedrock 

in a similar high-energy setting in northern Monterey Bay, about 40 km south of the map area. 

The Offshore of San Gregorio map area lies about 15 to 25 km southwest of the San 

Andreas Fault, the dominant structure in the distributed transform boundary between the North 

American and Pacific plates. The map area straddles the right-lateral San Gregorio Fault 

system, a prominent structure west of the San Andreas Fault in the broader San Andreas Fault 

system. The San Gregorio Fault system extends for about 400 km from Point Conception on the 

south to Bolinas and Point Reyes on the north (Dickinson and others, 2005), predominantly in 

the offshore but also onshore at coastal promontories such as Pescadero Point in the map area 

and also at Pillar Point, 14 km north of the map area and a few kilometers north of Half Moon 

Bay (see sheet 9, Map E). 

In the Offshore of San Gregorio map area, the San Gregorio Fault system forms a distributed shear zone about 2 to 4 km wide that includes two main diverging fault strands (fig. 1). 

The west strand (also known as the Frijoles Fault), which extends offshore from Pescadero 

Point, forms the boundary between rocks of the upper Miocene and Pliocene Purisima Formation on the east and the undivided Cretaceous and Tertiary rocks (Pigeon Point Formation?) on 

the west. The east strand (also known as the Coastways Fault or Seal Cove Fault) is mostly 

onshore in this map area. Seismic-reflection profiles (see sheet 8) reveal that the offshore 

exposures of the Purisima Formation between the east and west strands of the San Gregorio 

Fault Zone are highly deformed compared to those of the undivided Cretaceous and Tertiary 

rocks west of the Frijoles Fault.

Cumulative lateral slip on the San Gregorio Fault Zone is thought to range from 4 to 10 

mm/yr in this area (U.S. Geological Survey and California Geological Survey, 2010). The entire 

map area lies along strike with the young, high topography of the Santa Cruz Mountains and 

Coast Ranges (see sheet 9). Rates of uplift of nearby marine terraces of as much as 0.44 mm/yr 

near Año Nuevo, 15 km south of the map area, confirms that regional uplift is ongoing and that 

it includes the coastal zone (Weber, 1990).

LIST OF MAP UNITS

[See Description of Map Units (chapter 8, in pamphlet) for complete map-unit descriptions]

OFFSHORE GEOLOGIC AND GEOMORPHIC UNITS

[Note that composite units (gray-stippled areas) are designated on map by composite label 

indicating both overlying sediment cover and lower (older) unit, separated by slash (for 

example, Qms/Tp indicates that thin sheet of Qms overlies Tp)] 

Marine nearshore and shelf deposits (late Holocene)—Mostly sand; ripples 

common

Coarse-grained marine nearshore and shelf deposits (late Holocene)—

Predominantly coarse sand, gravel, cobbles, and boulders

Marine shelf scour depressions (late Holocene)—Inferred to be coarse sand and 

gravel

Fine-grained marine nearshore and shelf deposits (late Holocene)—Mostly mud, 

very fine sand, and silt

Purisima Formation, undivided (Pliocene and late Miocene)—Marine sandstone, 

siltstone, and mudstone

Tahana Member (Pliocene and late Miocene)—Medium-grained to very 

fine-grained lithic sandstone and siltstone, with some silty mudstone, 

tuffaceous sandstone, and pebble conglomerate

Bedrock, undivided (Tertiary and Cretaceous)—May consist of rocks of the 

Purisima Formation, the unnamed Miocene and Oligocene sedimentary and 

volcanic rocks unit, or the Pigeon Point Formation

Pigeon Point Formation (Late Cretaceous)—Sandstone and conglomerate, 

interbedded with siltstone and mudstone

ONSHORE GEOLOGIC AND GEOMORPHIC UNITS

[Units are compiled from Brabb (1980), Weber and Lajoie (1980), Brabb and others (1998), and 

Witter and others (2006); unit ages, which are from these sources, reflect local stratigraphic 

relations. Locations of some faults are from California Geological Survey (1982, 2002b)]

Artificial stream channel (late Holocene)—Modified, realigned, or straightened 

stream channels

Artificial fill (late Holocene)—Rock, sand, and mud, deposited by humans

Artificial fill over estuarine mud (late Holocene)—Material deposited by humans 

over estuarine sediment

Artificial-dam fill (late Holocene)—Earth- or rock-fill dams, embankments, and 

levees; constructed to impound land-locked water bodies

Artificial-levee fill (late Holocene)—Artificial levees bordering rivers, streams, salt 

ponds, and sloughs; constructed to contain floodwater or tidal waters

Beach-sand deposits (late Holocene)—Active beaches in coastal environment; may 

form veneer over bedrock platform

Stream-channel deposits (late Holocene)—Fluvial deposits within active, natural 

stream channels

Alluvial fan deposits (late Holocene)—Alluvial fan deposits; judged to be late 

Holocene (<1,000 years) in age, on basis of records of historical inundation or 

presence of youthful braid bars and distributary channels. Internal contacts 

delineate individual alluvial fans

Estuarine-delta deposits (Holocene)—Heterogeneous mixture of coarse and fine 

estuarine sediment; deposited in delta at mouths of tidally influenced coastal 

streams, where fresh water mixes with seawater

Alluvial deposits, undivided (Holocene)—Alluvium; deposited in fan, terrace, or 

basin environments

Basin deposits (Holocene)—Fine-grained sediment that accumulates from standing 

or slow-moving water in topographic basins

Colluvium (Holocene)—Loose to firm, unsorted sand, silt, clay, gravel, rock debris, 

and organic material, in varying proportions

Stream-terrace deposits (Holocene)—Relatively smooth, undissected terraces less 

than 8 to 10 m above active channel 

Landslide deposits (Holocene and Pleistocene)—Disintegrated bedrock; 

physically weathered; unit ranges from deep-seated landslides to active 

colluvium. Internal contacts delineate individual landslide masses

Older stream-terrace deposits (late Pleistocene)—Relatively flat, slightly 

dissected stream terraces; late Pleistocene age is indicated by degree of soil 

development and by height of terrace above flood level

Older alluvial deposits, undivided (late Pleistocene)—Alluvial fan or terrace 

surfaces; late Pleistocene age is indicated by depth of stream incision, degree of 

soil development, and lack of historical flooding

Marine-terrace deposits, undivided (Pleistocene)—Sand and gravel, deposited on 

uplifted marine-abrasion platforms along coast. Local relative ages designated 

by numbers from youngest (Qmt2) to oldest (Qmt1) 

Younger marine-terrace deposits (Pleistocene)—Younger sand and gravel, 

deposited on uplifted marine-abrasion platforms along coast

Older marine-terrace deposits (Pleistocene)—Older sand and gravel, deposited 

on uplifted marine-abrasion platforms along coast

Older alluvial fan deposits (late to early Pleistocene)—Moderately well to deeply 

dissected alluvial deposits; in places, original fan-surface morphology is 

preserved

Purisima Formation, undivided (Pliocene and late Miocene)—Medium-grained 

to very fine-grained, poorly indurated to friable sandstone, siltstone, and 

claystone, with conglomerate lenses and a few beds of white volcanic ash

Tunitas Sandstone Member (Pliocene)—Fine-grained sandstone, siltstone, and 

mudstone; some porcelaneous shale and mudstone, chert, silty mudstone, and 

volcanic ash 

Lobitos Mudstone Member (Pliocene)—Unbedded silty mudstone 

San Gregorio Sandstone Member (Pliocene)—Fine- to coarse-grained 

sandstone that has calcareous concretions

Pomponio Mudstone Member (Pliocene)—Porcelaneous shale and mudstone; in 

places, rhythmically bedded with alternating layers of nonsiliceous mudstone

Tahana Member (Pliocene and late Miocene)—Medium-grained to very 

fine-grained lithic sandstone and siltstone, interbedded with some silty 

mudstone, tuffaceous sandstone, and pebble conglomerate

Santa Cruz Mudstone (late Miocene)—Siliceous mudstone, interbedded with 

nonsiliceous mudstone, siltstone, and minor sandstone

Unnamed sedimentary and volcanic rocks (Miocene and Oligocene)—Mainly 

pebbly, crossbedded, hard arkosic sandstone in Pescadero Point area; grades to 

hard mudstone in Año Nuevo area, 15 km south of map area

Mindego Basalt and related volcanic rocks (Miocene and Oligocene)—Basaltic 

volcanic rocks, both extrusive and intrusive

Butano Sandstone (middle and early Eocene)—Very fine- to very coarse-grained 

arkosic sandstone, interbedded with mudstone and shale; conglomerate is 

present locally in lower part of section

Pigeon Point Formation (Late Cretaceous)—Sandstone and conglomerate, 

interbedded with siltstone and mudstone

Unnamed volcanic rocks (Cretaceous or Jurassic)—Finely crystalline, felsic 

volcanic rock that contains quartz and albite phenocrysts

EXPLANATION OF MAP SYMBOLS

Contact

Fault—Solid where location is certain, long-dashed where location is approximate, 

short-dashed where location is inferred, dotted where location is concealed, 

queried where uncertain

Reverse fault—Solid where location is certain, dashed where location is approximate, dotted where location is concealed, queried where uncertain. Boxes on 

upthrown block

Folds—Solid where location is certain, long-dashed where location is approximate, 

short-dashed where location is inferred, dotted where location is concealed, 

queried where uncertain

Anticline

Syncline

Approximate modern shoreline—Defined as Mean High Water (MHW) (+1.46 

m), North American Vertical Datum of 1988 (NAVD 88)

3-nautical-mile limit of California’s State Waters

Area of “no data”—Areas beyond 3-nautical-mile limit of California’s State Waters 

were not mapped as part of California Seafloor Mapping Program

CORRELATION OF MAP UNITS

TKu

ac af afem adf alf Qbs Qc Qyf Qed Qa Qb Qcl

Qls

Tp

Tsc

Tuv Tmb

Tb

Kpp

KJv

Qmt2

Qmt1

Qmt Qof

Qms Qmsc Qmss Qmsf

ONSHORE GEOLOGIC AND GEOMORPHIC UNITS

OFFSHORE GEOLOGIC AND

GEOMORPHIC UNITS

QUATERNARY

Holocene

TERTIARY

Pliocene

Miocene

Oligocene

Eocene

Cretaceous

Jurassic

MESOZOIC

Tptu

Tpl

Tpsg

Tpp

Kpp

Qyt

Pleistocene

Qot Qoa

Tpt

Tp

Tpt

1

U.S. Geological Survey;

2

Moss Landing Marine Laboratories, Center for Habitat Studies;

3

California Geological Survey

Offshore and Onshore Geology and Geomorphology, Offshore of San Gregorio Map Area, California

By

 Janet T. Watt,1 H. Gary Greene,2 Michael W. Manson,3

 Steven R. Hartwell,1 Charles A. Endris,2 Stephanie L. Ross,1 Eleyne L. Phillips,1 and Bryan E. Dieter2

2014

CALIF.

MAP LOCATION

ONE MILE = 0.869 NAUTICAL MILES

BATHYMETRIC CONTOUR INTERVAL 10 METERS

1 .5 0 1 KILOMETER

1000 0 1000 2000 3000 4000 5000 6000 7000 FEET

1 1/2 0 1 MILE

14°

SCALE 1:24 000

APPROXIMATE MEAN

DECLINATION, 2014

MAGNETIC 

 NORTH

TRUE NORTH

Offshore geology and geomorphology mapped by Janet T. Watt, H. Gary 

Greene, Stephen R. Hartwell, Charles A. Endris, Stephanie L. Ross, Eleyne 

L. Phillips, and Bryan E. Dieter, 2009-2012. Onshore geology compiled by 

Michael W. Manson from Brabb (1980), Weber and Lajoie (1980), California 

Geological Survey (1982, 2002b), Brabb and others (1998), and Witter and 

others (2006). Bathymetric contours by Peter Dartnell 

GIS database and digital cartography by Janet T. Watt, Stephen R. 

Hartwell, and Eleyne L. Phillips

Edited by Taryn A. Lindquist

Manuscript approved for publication June 30, 2014

Onshore elevation data collected by Photoscience in 2005 for U.S. 

Geological Survey and County of San Mateo. Offshore shadedrelief bathymetry from map on sheet 2, this report. California's 

State Waters limit from NOAA Office of Coast Survey

Universal Transverse Mercator projection, Zone 10N

NOT INTENDED FOR NAVIGATIONAL USE

Tpt

Tp

Tpp

Tpp

Tptu

Tsc

Tpl

Tpt

Tpl

Tpt Tsc

Qmt

Tp

Tp

Kpp

Kpp

Tpl

Tpl

Qmt

Tpsg

Tpl

Tptu

Tp

Tpsg

Qa

Qyf

Qmt2

Tsc

Tpt

Tpp

Tpt

Qyf

Tpsg

Qyf

Qyf

Qls

Qls

Tpp

Qcl

Tpl

Qof

Tpl

Tpl Tpsg

Tptu

Tb

Tpsg

Qmt

Qmt

Qmt

Tpp

Qof

Qls?

Tpsg

Qyf

Qcl

Tpp

Qof

Tpsg

Tmb

Qa

Tpl

Qls

Qcl

Qof

Qcl

Tmb

Tp

Qmt

Qcl

Qb

Qcl

Tp

Qed

Qyf

Qof

Tpsg

Qls

Qb

Tpsg

Tpp

Qls?

Qls

Qls

Qed

Qcl

Qof

Qbs

Tb

Qls?

Qcl

Qof

Qmt

Qmt1

Tp

Tptu

Qcl

Tpp

Qed

Qbs

Qls

Qmt1

Qcl

Qmt

Qc

Qmt

Qof

Qls

Qcl

Tpsg

Qoa

Qcl

Qoa

Qcl

Qof

Qof

Qmt

Qcl

Qmt

Qcl

Qcl

Qls

Qcl

Qcl

Qls

Tpl

Qcl

Qot

Qmt

Tpsg

Qls

Qoa

Qyf

Qb

Tpp

Qcl

Qof

Qls

Qls?

Qmt

Qmt

Qof

Qmt

Qmt

Qls

Qb

Tpl

Qyf

Qcl

Qcl

Qls?

Qb

Qof

Qyf

Qmt

Qcl

Qmt

Qyf

Qls

Qmt

Qls

Qcl

Qyf

Qof

Qls?

Tpp

Qcl

Tp

Qmt

Qot

Qmt

Qmt

Qyf

Qof

Qa

Qyf

Qyf

af

Qmt

Qcl

Qmt

Qmt

Qmt

Qc

Qc

Qbs

Qcl

Qof

Tpt

Qbs

ac

Qc

Qcl

Qc

Qcl

Qa

Qcl

Qmt

Qcl

Qof

Qof

Qof

af

Qcl

KJv

Tpl

Tpl

Qmt

Qcl

Qb

Tpl

Qcl

Tpt

af

Qa

Qyf

Qcl

Qa

af

Qmt

Qbs

Tptu

Qcl

Qof

Qc

Qc

Qcl

af

Qot

Tpsg

Qyf

af

Qyf

Tpp

Qa

Qc

Qof

Qmt

Qcl

Qls

Qa

Qmt

af

Qcl

af

Qcl

Qbs

Qcl

af

Qcl

Qc

Qcl

alf

Qa

Qed

Qcl

Qyf

Qcl

Qyf

Qot

Qls?

Qmt?

Tuv

af Qcl

af

Qyf

Qof

Tpt

Qcl

Qcl

Qmt

Tpt

Qmt

Qcl

Qcl

Qcl

Qmt

Qmt

Qyf

Qof

Tpp

Qmt

Qcl

Qof

Qcl

Qyf

af

Qof

Qyf

Qof

Qa

Qmt

alf

Qcl

Qcl

Qmt

Qls?

Qyf

Qb

Qof

adf

Qcl

Qmt

Qyf

af

Qmt

Qmt

ac

Qcl

Tp

afem

Tpl

Qcl

Tpt

Qof

Qyf Qbs

adf

Tptu

Qyf

Qcl

Tpl

Qyt

Qcl

Qcl

alf

Qc

Tptu

Qmt

Qmt

Qyf

af

Qmt

Qcl

Qyf

Qmt

Qmt

Qmt

Tpsg

adf

af

Qmt?

Qcl

Qbs

Qcl

Qmt

Qcl

afem

Tpp

Qa

Qa

Qmt

adf

adf

Qof

Qbs

Qmt

Tsc

adf

af

Qyt

Qcl

Qyt

Qmt

Qc

Qof

Qmt

Qa

adf

Qmt

Qbs

Qyf

Qyf

Qa

Tpp

Qmt

Qyt

Tpsg

Qmt

adf

Qmt?

Qmt

Qmt

Qyf

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Qyf

Qyf

Kpp

Qyf

Qmt

Qc

Qmt

af

Qmt Qcl

adf

af

adf

Qmt

Qyt

Qmt

Qmt

af

af

Qyf

Qmt

Qa

adf

Tpl

adf

adf

adf

Qcl

Qmt

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Qmt

Qmt

adf

af

Qbs

adf

af

Qyf

Qyt

adf

Qbs

Qmt

Tpt

adf

Qbs

Qbs

Kpp

Qa

Qyf

Qyf

Qls

Qyt

Qms

Qms/Tp

Qms/TKu

Kpp

Qms/Tp

Kpp?

Qmsc

Tp

Qms

Tp

Kpp

Qmsf

Tp?

Kpp

TKu

Kpp?

Qms

TKu

Tp?

TKu

Tp

Tp

Qmss

Kpp

Qmss

Tp

Kpp?

Tp

Tp

Tp

Tp

TKu

TKu

Kpp?

Tpt

Kpp

Qmss

Tp

Tp

Tp

Qms

Kpp

Tpt

Tp?

Kpp?

Qmsc

Kpp

Kpp

Qmss

Tpt

Tp

Qmsc Qmsc

TKu

Kpp

Tp

Tp

Tp

Kpp

Kpp

Qmss

TKu

Tp

Qmss

Tp

Tp

TKu

Tp

Tp?

Tp

Tp

Tp

Kpp? Kpp

Qmsc

Kpp

Kpp?

Tp

Kpp

Tp?

Kpp

Tpt

TKu

Tp

Kpp

Tp

Kpp?

Tp

TKu

Qmss

Tp

Tp

Tp?

Kpp?

Kpp

Tp

Tp?

Kpp

Tp

Kpp?

Kpp?

Kpp

Kpp?

Kpp

122°25'

122°25'

122°30'

122°30'

37°20'

37°20'

37°15'

37°15'

Qls

Tp

Qls Qls

Qls?

Qls?

Qls?

TKu

Qms/TKu

Tp

Scientific Investigations Map 3306

Sheet 10 of 10

Pamphlet accompanies map

U.S. Department of the Interior

U.S. Geological Survey