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://dx.doi.org/10.3133/ofr20151088 or http://pubs.usgs.gov/of/2015/1088/

Suggested Citation: Hartwell, S.R., Johnson, S.Y., and Manson, M.W., 2015, Offshore and onshore geology and geomorphology, Offshore of 

Tomales Point map area, California, sheet 10 in Johnson, S.Y., Dartnell, P., Golden, N.E., Hartwell, S.R., Greene, H.G., Erdey, M.D., Cochrane, 

G.R., Watt, J.T., Kvitek, R.G., Manson, M.W., Endris, C.A., Dieter, B.E., Krigsman, L.M., Sliter, R.W., Lowe, E.N., and Chin, J.L. (S.Y. Johnson and 

S.A. Cochran, eds.), California State Waters Map Series—Offshore of Tomales Point, California: U.S. Geological Survey Open-File Report 

2015–1088, pamphlet 38 p., 10 sheets, scale 1:24,000, http://dx.doi.org/10.3133/ofr20151088.

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20151088

Figure 1. Regional map showing the location of Offshore of Tomales Point 

map area, San Andreas Fault (SAF), and Point Reyes Fault (PRF). Other 

abbreviations: PA, Point Arena; PR, Point Reyes; SF, San Francisco; SFB, 

San Francisco Bay.

123°30' 123° 122°30'

38°30'

38°

37°30'

0 30 60 120

Kilometers

0 15 30 60

Nautical Miles

123°30' 123° 122°30'

38°30'

38°

37°30'

0 30 60 120Kilometers

0 15 30 60

Nautical Miles

Pacific Ocean SFB

SF

map 

area

SAF

PR

PA

PRF

123°20 123°

38°20'

38°

0 5 10 Kilometers

0 5 10 Nautical Miles

Area of

Map

Limit of California’s

State Waters

Point Reyes

Tomales Bay

Bodega

Bay

CALIF.

MAP LOCATION

Bodega

Harbor

alf

Qbs

Tm

Tp

Qa

Qt

Qsc

af

 

ch

ss

Qof

Kgd

Kgr

sp

fsr

KJfss

KJfgs

afem

adf

Qds

Qf

Qed

Qe

Qot

Qods

Tsm

Tl

Qmt

Qls

Twg

Qml

Qobs

Qc

Qmsc

Qms

Qmsf

Qmsd

Qstb

Tu

Kg

Tl

Qsr

Qsw

Qkdtb

Qdtb

REFERENCES CITED

Anima, R.J., Chin, J.L., Finlayson, D.P., McGann, M.L., and Wong, F.L., 2008, Interferometric 

sidescan bathymetry, sediment and foraminiferal analyses; a new look at Tomales Bay, 

California: U.S. Geological Survey Open-File Report 2008–1237, 33 p., available at 

http://pubs.usgs.gov/of/2008/1237.

Brown, R.D., Jr., and Wolfe, E.W., 1972, Map showing recently active breaks along the San 

Andreas Fault between Point Delgada and Bolinas Bay, California: U.S. Geological Survey 

Miscellaneous Investigations Map I-692, scale 1:24,000.

Bryant, W.A., and Lundberg, M.M., compilers, 2002, Fault number 1b, San Andreas fault zone, 

North Coast section, in Quaternary fault and fold database of the United States: U.S. 

Geological Survey website, accessed April 4, 2013 at http://earthquakes.usgs.gov/hazards/

qfaults.

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, 1974, Alquist-Priolo earthquake fault zone map of Tomales and 

Valley Ford quadrangles, scale 1:24,000, available at http://www.quake.ca.gov/gmaps/WH/

regulatory maps.htm.

Clark, J.C., and Brabb, E.E., 1997, Geology of the Point Reyes National Seashore and vicinity, 

California—A digital database: U.S. Geological Survey Open-File Report 97–456, scale 

1:48,000, available at http://pubs.usgs.gov/of/1997/of97-456/.

Davis, A.C.D., Kvitek, R.G., Mueller, C.B.A., Young, M.A., Storlazzi, C.D., and Phillips, E.L., 

2013, Distribution and abundance of rippled scour depressions along the California coast: 

Continental Shelf Research, v. 69, p. 88–100, doi:10.1016/j.csr.2013.09.010.

Galloway, A.J., 1977, Geology of the Point Reyes Peninsula, Marin County, California: California 

Geological Survey Bulletin 202, 72 p., scale 1:24,000.

Grove, K., and Niemi, T.M., 2005, Late Quaternary deformation and slip rates in the northern San 

Andreas fault zone at Olema Valley, Marin County, California: Tectonophysics, v. 401, p. 

231–250, doi:10.1016/j.tecto.2005.03.014.

Grove, K., Sklar, L.S., Scherer, A.M., Lee, G., and Davis, J., 2010, Accelerating and 

spatially-varying crustal uplift and its geomorphic expression, San Andreas Fault zone north 

of San Francisco, California: Tectonophysics, v. 495, p. 256–268, doi: 10.1016/

j.tecto.2010.09.034.

Heck, R.G., Edwards, E.B., Kronen, J.D., Jr., and Willingham, C.R., 1990, Petroleum potential of 

the offshore outer Santa Cruz and Bodega basins, California, in Garrison, R.E., Greene, H.G., 

Hicks, K.R., Weber, G.E., and Wright, T.L., eds. Geology and tectonics of the central 

California coastal region, San Francisco to Monterey: American Association of Petroleum 

Geologists, Pacific Section, Bulletin GB67, p. 143–164.

Klise, D.H., 1984, Modern sedimentation on the California continental margin adjacent to the 

Russian River: M.S. thesis, San Jose State University, 120 p.

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.

Lawson, A.C., ed., 1908, The California earthquake of April 18, 1906, Report of the State 

Earthquake Investigation Commission: Carnegie Institution of Washington Publication 87, v. 

1, 1,451 p., and atlas.

Lomax, A., 2005, A reanalysis of the hypocentral location and related observations for the Great 

1906 California earthquake: Bulletin of the Seismological Society of America, v. 95, p. 

861–877, doi:10.1785/0120040141.

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.

National Park Service, 2012, Shipwrecks on the Point Reyes Peninsula 1849–1940, in Shipwrecks 

at Point Reyes: National Park Service Web site, available at http://www.nps.gov/pore/

historyculture/upload/map_shipwrecks.pdf.

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/.

Trembanis, A.C., and Hume, T.M., 2011, Sorted bedforms on the inner shelf off northeastern New 

Zealand—Spatiotemporal relationships and potential paleo-environmental implications: 

Geo-Marine Letters, v. 31, p. 203–214, doi:10.1007/s00367-010-0225-8.

Wagner, D.L., and Gutierrez, C.I., 2010, Preliminary geologic map of the Napa 30′ × 60′ 

quadrangle, California: California Geological Survey, scale 1:100,000, available at http://

www.conservation.ca.gov/cgs/rghm/rgm/Pages/preliminary_geologic_maps_1page.aspx.

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/.

EXPLANATION OF MAP SYMBOLS

Contact—Solid where location is certain, dashed where location is approximate, dotted 

where location is concealed

Fault—Long-dashed where location is approximate, short-dashed where location is 

inferred, dotted where location is concealed, queried where uncertain. Arrows show 

direction of relative movement

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

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

Anticline

Syncline

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

North American Vertical Datum of 1988 (NAVD 1988)

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

DISCUSSION

Marine geology and geomorphology were mapped in the Offshore of Tomales Point 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), and high-resolution seismic-reflection profiles (sheet 8). Aerial 

photographs taken in multiple years were used to map the nearshore area (0 to 10 m water depth) 

and to link the offshore and onshore geology.

Onshore bedrock mapping is compiled from Galloway (1977), Clark and Brabb (1997) and 

Wagner and Gutierrez (2010). Onshore Quaternary mapping is compiled from Witter and others 

(2006) and Wagner and Gutierrez (2010), with some additional mapping by M.W. Manson (this 

report); in addition, some units are modified by M.W. Manson on the basis of analysis of 2012 lidar 

imagery. Traces of San Andreas Fault are compiled from California Geological Survey (1974). 

The morphology and the geology of the offshore part of the Offshore of Tomales Point map 

area result from the interplay between tectonics, sea-level rise, local sedimentary processes, and 

oceanography. The map area is cut by the northwest-trending San Andreas Fault, a right-lateral 

transform boundary between the North American and Pacific tectonic plates (fig. 1). The San 

Andreas strikes through Tomales Bay, the northern part of a linear valley that extends from Bolinas 

through Olema Valley to Bodega Bay, which separates mainland California from the Point Reyes 

Peninsula. Onshore investigations indicate that this section of the San Andreas Fault has an 

estimated slip rate of about 17 to 25 mm/yr (Bryant and Lundberg, 2002; Grove and Niemi, 2005). 

The devastating great 1906 California earthquake (M7.8, 4/18/1906) is thought to have nucleated 

on the San Andreas Fault about 60 kilometers south of this map area offshore of San Francisco (see, 

for example, Bolt, 1968; Lomax, 2005), with the rupture extending northward through the Offshore 

of Tomales Point map area to the south flank of Cape Mendocino (Lawson, 1908; Brown and 

Wolfe, 1972). 

The Point Reyes Peninsula is bounded to the south and west in the offshore by the north- and 

east-dipping Point Reyes Thrust Fault (fig. 1; McCulloch, 1987; Heck and others, 1990), located 

about 20 km west of Tomales Point. Granitic basement rocks are offset about 1.4 km on this thrust 

fault offshore of Point Reyes (McCulloch, 1987), and this uplift combined with west-side-up offset 

on the San Andreas Fault (Grove and Niemi, 2005) resulted in uplift of the Point Reyes Peninsula, 

including Tomales Point and the adjacent continental shelf. Grove and others (2010) reported uplift 

rates of as much as 1 mm/yr for the south flank of the Point Reyes Peninsula based on marine 

terraces, but reported no datable terrace surfaces that could constrain uplift for the flight of 4–5 

terraces exposed farther north along Tomales Point.

Because of this Quaternary uplift and relative lack of sediment supply from coastal watersheds, there is extensive rugged, rocky seafloor beneath the continental shelf in the Offshore of 

Tomales Point map area. Granitic rocks (unit Kg) on the seafloor are mapped on the basis of 

massive character, roughness, extensive fractures, and high backscatter (sheet 3). Neogene sedimentary rocks (units Tl and Tu) commonly form distinctive “ribs,” created by differential seafloor 

erosion of dipping beds of variable resistance. The more massive offshore outcrops of unit Tu in the 

southern part of the map area are inferred to represent more uniform lithologies. Slopes on the 

granitic seafloor (generally 1° to 1.3°) are greater than those over sedimentary rock (generally about 

0.5° to 0.6°). 

Sediment-covered areas occur in gently sloping (less than about 0.6°) midshelf environments 

west and north of Tomales Point, and at the mouth of Tomales Bay. Sediment supply is local, 

limited to erosion from local coastal bluffs and dunes, small coastal watersheds, and sediment flux 

out of the mouth of Tomales Bay. Shelf morphology and evolution largely result from eustacy; sea 

level has risen about 125 to 130 m over about the last 21,000 years (for example, Lambeck and 

Chappell, 2001), leading to broadening of the continental shelf, progressive eastward migration of 

the shoreline and wave-cut platform, and associated transgressive erosion and deposition. 

Given present exposure to high wave energy, modern nearshore to midshelf sediments are 

mostly sand (unit Qms) and a mix of sand, gravel, and cobbles (units Qmsc and Qmsd). These 

sediments are distributed between rocky outcrops at water depths of as much as 65 m (see below). 

The coarser grained sands and gravels (units Qmsc and Qmsd) are primarily recognized on the 

basis of bathymetry and high backscatter (sheets 1, 2, 3). Unit Qmsd forms erosional lags in 

scoured depressions that are bounded by relatively sharp contacts with bedrock, or sharp to diffuse 

contacts with units Qms and Qmsc. These depressions are typically a few tens of centimeters deep 

and range in area from a few tens of square meters to more than one square kilometer.

Similar unit Qmsd scour depressions are common along this stretch of the California coast 

(see, for example, Cacchione and others, 1984; Davis and others, 2013) where surficial offshore 

sandy sediment is relatively thin (unable to fill the depressions) owing to lack of sediment supply 

and to erosion and transport of sediment during large northwest winter swells. Such features have 

been referred to as “rippled-scour depressions” (see, for example, Cacchione and others, 1984) or 

“sorted bedforms” (see, for example, Trembanis and Hume, 2011). Although the general areas in 

which both unit Qmsd scour depressions and surrounding Qms sand sheets occur are not likely to 

change substantially, the boundaries of the unit(s) likely are ephemeral, changing seasonally and 

during significant storm events. 

Unit Qmsf consists primarily of mud and muddy sand and is commonly extensively bioturbated. The location of the inboard contact at water depths of about 65 m is based on meager 

sediment sampling and photographic data (sheets 5, 6) and the inference that if must lie offshore of 

the outer boundary of coarse-grained units Qmsd and Qmsc. This is notably deeper than the inner 

contact of unit Qmsf offshore of the nearby Russian River (about 50 m; Klise, 1984), which may 

result from both increased wave energy and significantly decreased supply of muddy sediment. 

There are two areas of high-backscatter (sheet 3), rough seafloor at water depths of 65 to 70 m 

west of northern Tomales Point. These areas are notable in that each includes several small (less 

than about 20,000 m2), randomly distributed to northwest-trending, irregular “mounds,” with as 

much as 1 m of positive relief above the seafloor (unit Qsr). Seismic-reflection data (for example, 

sheet 8, fig. 4) reveal this lumpy material rests on several meters of uppermost Pleistocene to 

Holocene sediment and is thus not bedrock outcrop. We interpret this sediment to be marine debris, 

possibly derived from the more than 60 shipwrecks that have occurred offshore of the Point Reyes 

Peninsula between 1849 and 1940 (National Park Service, 2012). It is also conceivable that this 

lumpy terrane consists of biological “hardgrounds” (that is, groups of fauna on the seafloor that 

have rigid, often calcareous, shells that exhibit high reflectivity, similar to lithified rock). 

Units Qsw, Qstb, Qdtb, and Qkdtb comprise sediments in Tomales Bay. Anima and others 

(2008) conducted a high-resolution bathymetric survey of Tomales Bay and noted that strong tidal 

currents at the mouth of the bay had created a large field of sandwaves, dunes, and flats (unit Qsw). 

Unit Qkdtb is a small subaqueous sandy delta deposited at the mouth of Keys Creek, the largest 

coastal watershed draining into this northern part of Tomales Bay. Unit Qstb occurs south of units 

Qsw and Qdtb, and comprises largely flat seafloor underlain by mixed sand and silt. Unit Qdtb

consists of depressions within the sedimentary fill of Tomales Bay. These depressions commonly 

occur directly offshore of coastal promontories, cover as much as 74,000 m2, and are as deep as 9 m. 

LIST OF MAP UNITS

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

OFFSHORE GEOLOGIC AND GEOMORPHIC UNITS

Marine shelf deposits, rough seafloor (late Holocene)—Randomly distributed to 

northwest-trending, irregular “lumps” (as large as 20,000 m2) with as much as 1 m 

of positive relief above the seafloor, interpreted as marine debris 

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

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

gravel, and cobbles

Fine-grained marine shelf deposits (late Holocene)—Mostly mud to muddy sand

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

gravel in low-relief scours

Sediments of central Tomales Bay (late Holocene)—Sand, silt, and clay (Anima and 

others, 2008)

Sand at the mouth of Tomales Bay (late Holocene)—Coarse to medium sand forming 

sand waves, dunes, and flats at mouth of Tomales Bay (Anima and others, 2008)

Subaqueous delta at the mouth of Walker Creek (late Holocene)—Semicircular 

subaqueous delta extending into Tomales Bay from the mouth of Walker Creek

Seafloor depressions in Tomales Bay (late Holocene)—Oval to oblate depressions 

within the sedimentary fill of Tomales Bay

Sedimentary rocks, undivided (late Pliocene to middle Miocene)—Consists of Laird 

Sandstone (unit Tl), Monterey Formation (unit Tm), Santa Margarita Sandstone 

(unit Tsm), and Purisima Formation (unit Tp) 

Laird Sandstone (middle Miocene)—Marine arkosic sandstone, includes basal 

granitic conglomerate

Granitic rocks (Cretaceous)—Offshore equivalent of the Tonalite of Tomales Point 

(unit Kgd) and the Granodiorite and granite of Inverness Ridge (unit Kgr) 

ONSHORE GEOLOGIC AND GEOMORPHIC UNITS

[Units are compiled from Clark and Brabb (1997), Witter and others (2006), and Wagner and 

Gutierrez (2010)]

Artificial fill (late Holocene)—Material placed by humans

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

over estuarine sediments 

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

sloughs and islands for the purpose of containing flood or tidal waters

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

levees; constructed to impound land-locked water bodies

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

stream channels

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

form veneer over bedrock platform

Stream terrace deposits (late Holocene)—Stream terrace deposits judged to be late 

Holocene (less than 1,000 years) based on records of historical inundation or 

identification of youthful meander or braid bars

Stream terrace deposits (Holocene)—Stream terrace sediments deposited in point bar 

and overbank environments

Dune sand (Holocene)—Active dunes and recently stabilized dunes in coastal 

environments

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

sediment deposited in Drakes Estero (southern edge of map) and at Toms Point on 

the east shore of Tomales Bay

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

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

streams where fresh water mixes with seawater

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

environments

Alluvial fan deposits, undivided (Holocene)—Sediment deposited by streams 

emanating from mountain canyons onto alluvial valley floors or alluvial plains

Alluvial fan deposits, undifferentiated (latest Pleistocene to Holocene)—Mapped in 

small valleys where separate fan, basin, and terrace units could not be delineated at 

the scale of this mapping

Colluvium (Holocene and late Pleistocene)—Unsorted clay, silt, sand, gravel, and 

rock debris, in varying proportions

Landslide deposits (Holocene and Pleistocene)—Weathered and disintegrated rocks 

and soil

Older dune sand (late Pleistocene?)—Dunes stabilized by vegetation; forms large 

complex east of the mouth of Tomales Bay

Millerton Formation (late Pleistocene)—Alluvial and estuarine clay, silt, sand, and 

gravel deposited on terraces along the eastern margin of Tomales Bay

Marine-terrace deposits (late Pleistocene)—Marine sediments uplifted to form 

terraces along east coast of Tomales Bay and on southeast coast of Bodega Bay

Beach sand in uplifted marine terraces (late Pleistocene?)—Reddish-brown, friable 

sand and gravel; occurs on west coast of Tomales Point, north of Abbots Lagoon

Purisima Formation (late Pliocene to late Miocene)—Marine siltstone, sandstone, 

and mudstone; locally contains diatomite

Wilson Grove Formation (Pliocene and late Miocene)—Marine sandstone and 

conglomerate

Santa Margarita Sandstone (late Miocene)—Massive marine glauconitic and 

bituminous arkosic sandstone

Monterey Formation (middle to late Miocene)—Marine, thin-bedded chert, 

porcelanite, shale, and sandstone

Laird Sandstone (middle Miocene)—Arkosic sandstone that contains basal 

granitic-boulder conglomerate

Granodiorite and granite of Inverness Ridge (Late Cretaceous)—Granodiorite and 

granite; aplite and alaskite dikes and masses are locally abundant

Tonalite of Tomales Point (Late Cretaceous)—Hornblende-biotite tonalite that 

contains dark diorite inclusions

Franciscan Complex 

Sandstone and shale in the Nicasio Reservoir terrane (Cretaceous and Jurassic)

Greenstone in Central belt (Cretaceous and Jurassic)

Mélange in Central belt (Cretaceous and Jurassic)—Sheared argillite, graywacke, 

and minor green tuff matrix enclosing blocks and lenses of sandstone, shale, chert, 

metachert, and serpentinite

Sandstone and shale blocks within mélange

Chert and metachert blocks within mélange 

Serpentinite blocks and lenses within mélange of the Central belt

Metamorphic rocks (Age uncertain, probably Mesozoic or Paleozoic)—Intruded by 

Cretaceous granitic rocks; includes mica schist, quartzite, calc-hornfels, and marble 

(Clark and Brabb, 1997)

af Qsc Qt Qa Qf

Qml

Qls

Qsr Qms Qmsc Qmsf Qmsd

KJfss sp

Pliocene

Pleistocene

Holocene

CRETACEOUS

JURASSIC

QUATERNARY

TERTIARY

OFFSHORE GEOLOGIC AND GEOMORPHIC UNITS ONSHORE GEOLOGIC AND GEOMORPHIC UNITS

CORRELATION OF MAP UNITS

[See Description of Map Units (chapter 8, in pamphlet) for precise unit ages]

Miocene

Twg

Kg

afem Qbs

Qof

KJfqs fsr ss ch

alf adf Qot Qds Qe Qed

Kgr

MESOZOIC

PALEOZOIC

 

Qstb Qsw Qkdtb

Tu

Tl

Kgd

Tp

Tsm

Tm

Qdtb

Qc

Qods Qmt Qobs

Tl

1

U.S. Geological Survey;

2

California Geological Survey

Offshore and Onshore Geology and Geomorphology, Offshore of Tomales Point Map Area, California

 By

Stephen R. Hartwell,1 Samuel Y. Johnson,1 and Michael W. Manson,2

2015

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, 2015

MAGNETIC 

 NORTH

TRUE NORTH

Offshore geology and geomorphology mapped by Stephen R. 

Hartwell and Samuel Y. Johnson, 2012−2013. Onshore geology and 

geomorphology compiled by Michael W. Manson, 2012−2013; from 

California Geological Survey (1974), Galloway (1976), Clark and 

Brabb (1997), Wagner and Gutierrez (2010), and M.W. Manson 

(unpublished). Bathymetric contours by Mercedes D. Erdey, 2013

GIS database and digital cartography by Peter Dartnell and Stephen 

R. Hartwell 

Manuscript approved for publication May 4, 2015

Onshore elevation data from California Coastal Conservancy, 

available at http://www.csc.noaa.gov/digitalcoast/data/coastallidar 

and from U.S. Geological Survey, National Elevation Dataset, 

available at http://ned.usgs.gov/. Offshore shaded-relief 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

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Tomales Point

Tomales Bay

San Andreas Fault Zone

Abbots

Lagoon

Toms

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Bodega Bay

Keys Creek

Tl

Kgr

Kgd fsr

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Twg

fsr

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Qods

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fsr

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fsr

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ch

fsr

Qed

KJfgs

Tp

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ch

Qobs

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Qmt

af

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fsr

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Open-File Report 2015–1088

Sheet 10 of 10

Pamphlet accompanies map

U.S. Department of the Interior

U.S. Geological Survey

123°5' 123° 122°55'

123°5' 123° 122°55'

38°15'

38°10'

38°15'

38°10'