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/3302/

Suggested Citation: Lorenson, T.D., Wong, F.L., Leifer, I., Hostettler, F.D., Peters, K.E., Kvenvolden, K.A., Rosenbauer, R.J., and Fong, G., 

2014, Natural offshore hydrocarbon seepage and related tarball accumulation, Offshore of Coal Oil Point map area, California, sheet 

11 in Johnson, S.Y., Dartnell, P., Cochrane, G.R., Golden, N.E., Phillips, E.L., Ritchie, A.C., Kvitek, R.G., Dieter, B.E., Conrad, J.E., 

Lorenson, T.D., Krigsman, L.M., Greene, H.G., Endris, C.A., Seitz, G.G., Finlayson, D.P., Sliter, R.W., Wong, F.L., Erdey, M.D., Gutierrez, 

C.I., Leifer, I., Yoklavich, M.M., Draut, A.E., Hart, P.E., Hostettler, F.D., Peters, K.E., Kvenvolden, K.A., Rosenbauer, R.J., and Fong, G. (S.Y. 

Johnson and S.A. Cochran, eds.), California State Waters Map Series—Offshore of Coal Oil Point, California: U.S. Geological Survey 

Scientific Investigations Map 3302, pamphlet 57 p., 12 sheets, scale 1:24,000, http://dx.doi.org/10.3133/sim3302.

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3302

CALIF.

0 4 8 Nautical Miles

Kilometers 0 5 10

120° 119°40' 119°20' 119°

34°

34°20'

MAP LOCATION

Ventura

Santa Barbara

Anacapa

Island

Santa Cruz Island Santa Rosa Island

Area of

Map

Santa Barbara Channel Limit of California’s

State Waters

Figure 13. View to west of beach at Coal Oil Point, showing substantial tarball stranding in June 2003 

during period of unusual tarball accumulation; tarballs can be seen on several wave strand lines. 

Tarballs result from nearby naturally occurring oil seepage and subsequent stranding on beach; 

previous studies (Del Sontro and others, 2007; Lorenson and others, 2009) showed that significant 

order-of-magnitude seasonal variations of beach tar accumulation can occur. Inset photograph 

shows close-up of nascent tarballs, which are releasing light film of oil; more commonly, tarballs are 

less frequent, more weathered, and do not emit oily sheen. 

Figure 12. Active, small, viscous asphalt mound offshore of Naples (sample no. 09-109). Also shown is 

sea cucumber (sc). Field of view, about 30 × 40 cm.

sc

Figure 11. Flowing asphalt southeast of Coal Oil Point (sample no. 09-115, asphalt mound “Area 1”). 

Field of view, about 20 × 30 cm.

Figure 10. Viscous asphalt, sediment, and shell fragments extruding from small mounds near outfall of 

Goleta sewage line, offshore of Goleta Pier (sample no. 10-159, asphalt mound “Area 3”). Water 

depth, about 40 m; field of view, about 30 × 25 cm.

Figure 9. Gas seep issuing from sediment-covered, invertebrate-colonized asphalt mound just east of 

map area; water depth, 75 m. Here, asphalt mounds coalesce into features as much as 80 m in 

diameter and 3 m in relief. Larger mounds are found elsewhere in Santa Barbara Channel offshore of 

Point Conception (west of map area) and on Mid-Channel high (southeast of map area). Size of 

gorgonian coral and multitude of solitary cup corals implies feature is decades old. Field of view, 

about 50 × 40 cm.

Figure 8. Naturally seeping, oil-coated gas bubbles rising from seafloor at “La Goleta” seep, in area 

next to sample locality 09-113. Anenome- and bryozoan-encrusted rock overlies dark, rubbly 

sediment that contains dark iron sulfides and colonies of white, sulfate-reducing microbes. Field of 

view, about 30 × 40 cm.

Figure 7. Asphalt (tar) sample being retrieved from ROV claw. Inset photograph shows ROV used to 

sample natural seeps; ROV is equipped with 10-megapixel digital still camera and high-definition 

(1,080 × 1,920 pixel resolution) video camera, as well as gas- and oil-sampling equipment.

Figure 6. ROV pilot maneuvering ROV along seafloor. Twin monitors display live images from two video 

cameras mounted on ROV.

Figure 5. ROV being prepared for deployment offshore of Coal Oil Point.

Figure 4. Naturally seeping gas and oil rising to ocean surface above “La Goleta” seep, in Coal Oil 

Point seep field (sample no. 09-413). Large, visible oil sheens are present on water surface on calm 

days, and petroleum odor can be strong. Inset photograph shows close-up of oil on water surface 

above “Trilogy” seep; oil drops and oil-coated natural-gas bubbles rise and burst at surface, then 

spread out on water surface to create dazzling rainbow of colors, which result from refraction of 

light through thin oil film of varying thickness; field of view of inset photograph, about 100 × 80 cm.

Figure 3. Aerial photograph of Coal Oil Point seep field offshore of Coal Oil Point, showing numerous 

comingling, naturally occurring oil slicks and also site of “Trilogy” oil and gas seep (yellow outline). 

Inset photograph “A” shows natural gas bubbling from seafloor vents at “Trilogy” seep, in 50 m 

water depth; orange bottle contains fluorescein dye used in experiments to measure 

water-advection rates created by upward movement of seep-bubble emissions; field of “A” view, 

about 30 × 25 cm. Inset photograph “B” shows localized upwelling (caused by high gas emissions) 

from “Seep Tent” seep, which can be identified by green water (from fluorescein dye) that surrounds 

seep next to light-colored areas of gas reaching surface; field of “B” view, about 30 × 25 cm.

A

B

Coal Oil

Point

97-56

05-10

02-62

05-530

EXPLANATION

Type of sample—Indicated by color of sample-number label

Seep—Surface-oil sample associated with active underlying seepage

Unlocated seep (surface-oil sample)

Oil

Tarball or asphalt

Model groups (oil tribes and families)—Oil families determined by suite of biomarkers. Symbols 

within transparent white boxes have been offset from their collection localities for clarity

Tribe 1 sample localities—Source rock inferred to be clayey, siliceous-rich shale of the 

Monterey Formation, with significant higher plant-organic matter input, deposited under 

suboxic conditions

Family 11

Family 12

Family 13

Family 14

Tribe 2 sample localities—Source rock inferred to be carbonaceous marl, deposited in 

hemipelagic setting under suboxic to anoxic conditions 

Family 211

Family 212

Family 22

Tribe 3 sample localities—Source rock inferred to be clay-poor, calcareous-siliceous carbonate, 

deposited under anoxic conditions and dominated by pelagic organic matter

Family 31

Unclassified group—Too weathered and biodegraded to classify

Family 0

Previously located seeps

Seeps (informally named)—Confirmed by Leifer and others (2010)

Offshore seeps—Unconfirmed (Wilkinson 1971, 1972)

Hydrocarbon fields 

Oil field—From California Division of Oil, Gas, and Geothermal Resources (2001)

Gas field—From California Division of Oil, Gas, and Geothermal Resources (2001)

Gas-vent field—From Hornafius and others (1999)

Asphalt-mound field—Dashed where boundary is uncertain

DISCUSSION

Ongoing natural hydrocarbon seepage in the Offshore of Coal Oil Point map area has fascinated humans 

for centuries. The native Chumash tribe used the asphalt (tar), which is biodegraded and weathered oil, found 

in the map area for a variety of purposes, including waterproofing boats and gluing arrowheads to shafts 

(Galloway, 1998). Hydrocarbon emissions, all sourced from the Miocene Monterey Formation and the Rincon 

Shale, range from viscous biodegraded asphalt or oil drops to methane-rich gas bubbles. Some of these 

emissions impact the shoreline by the deposition of tarballs and the local atmosphere by the release of hydrocarbon gases such as methane and ethane. 

This map of known hydrocarbon-seepage sites and their oil-source chemical fingerprinting was compiled 

during a 10-year study that linked beach tarballs to their offshore sources. This study was conducted by the 

U.S. Geological Survey, in conjunction with the Bureau of Ocean Energy Management (formerly, the Minerals 

Management Service), the County of Santa Barbara Energy Division, and the University of California, Santa 

Barbara. The approach was to (1) document the locations of naturally occurring seep oils or tar; (2) collect and 

geochemically fingerprint samples from these natural occurrences; (3) geochemically fingerprint (with 

biomarkers) coastal tar residues and potential tar sources in this region, both onshore and offshore; and (4) 

establish chemical correlations between offshore active seeps and coastal residues, thus linking seep sources 

and oil residues. The results of this study can be found in Hostettler and others (2004), Peters and others 

(2008), and Lorenson and others (2009, 2011). Sample numbers displayed on the map are from Lorenson and 

others (2009, 2011).

Using multivariate statistical techniques (Peters and others, 2008), the oil has been divided into three 

“tribes” of 13C-rich oils, inferred to originate from thermally mature equivalents of three types of strata from 

the Monterey Formation: (1) clayey-siliceous shale, (2) carbonaceous marl, and (3) calcareous-siliceous 

carbonate rock. These three tribes have been further subdivided into 13 oil “families.” Seven of these families 

are present in the Offshore of Coal Oil Point map area, with Family 211 being found most frequently, both 

onshore as tarballs and offshore as seep sources. 

Also shown on the map are the onshore and offshore oil (green outline) and gas (red outline) fields in the 

map area (from California Division of Oil, Gas, and Geothermal Resources, 2011), as well as gas-seepage 

areas (orange outline), as mapped by Hornafius and others (1999), and asphalt mounds (pink outline). Figure 1 

shows a resurvey of normalized sonar return of gas-emission intensity as measured by Leifer and others 

(2010); figure 2 is a multibeam-sonar image of the water column above the “Trilogy” seep; and figures 3 and 4 

show the expression of seeps on the water surface.

The shaded-relief seafloor map shows some of the geologic structure underlying the area. Sampling and 

imaging of the seafloor and seeps was undertaken with a remotely operated vehicle (ROV; see figs. 5, 6, 7) on 

three occasions, as guided by seafloor morphology, sea-surface hydrocarbon-seep expression, and dissolved 

methane in seawater. Figures 8 and 9 show gas seeps; figures 10, 11, and 12 show the morphology and structure of asphalt mounds; and figure 13 shows tarballs transported from these seeps to the shoreline. 

REFERENCES CITED

California Division of Oil, Gas, and Geothermal Resources, 2001, Oil, gas, and geothermal fields in California: 

California Division of Oil, Gas, and Geothermal Resources, scale 1:1,500,000, available at 

ftp://ftp.consrv.ca.gov/pub/oil/maps/Map_S-1.pdf.

Del Sontro, T.S., Leifer, I., Luyendyk, B.P., and Broitman, B.R., 2007, Beach tar accumulation, transport 

mechanisms, and sources of variability at Coal Oil Point, California: Marine Pollution Bulletin, v. 54, p. 

1,461–1,471, doi:10.1016/j.marpolbul.2007.04.022.

Galloway, J.M., 1998, Chronology of petroleum exploration and development in the Santa Barbara channel 

area, offshore southern California, in Kunitomi, D.S., Hopps, T.E., and Galloway, J.M., eds., Structure and 

petroleum geology, Santa Barbara Channel, California: American Association of Petroleum Geologists, 

Pacific Section, and Coast Geological Society, Miscellaneous Publication 46, p. 1–12, 1 sheet.

Hornafius, J.S., Quigley, D.C., and Luyendyk, B.P., 1999, The world's most spectacular marine hydrocarbons 

seeps (Coal Oil Point, Santa Barbara Channel, California)—Quantification of emissions: Journal 

Geophysical Research – Oceans, v. 104, p. 20,703–20,711.

Hostettler, F.D., Rosenbauer, R.J., Lorenson, T.D., and Dougherty, J.A., 2004, Geochemical characterization of 

tarballs on beaches along the California coast, part I—Shallow seepage impacting the Santa Barbara 

Channel Islands, Santa Cruz, Santa Rosa and San Miguel: Organic Geochemistry, v. 35, p. 725–746.

Leifer, I., Kamerling, M., Luyendyk, B.P., and Wilson, D.S., 2010, Geologic control of natural marine 

hydrocarbon seep emissions, Coal Oil Point seep field, California: Geo-Marine Letters, v. 30, p. 331–338, 

doi:10.1007/s00367-010-0188-9.

Lorenson, T.D., Hostettler, F.D., Rosenbauer, R.J., Peters, K.E., Kvenvolden, K.A., Dougherty, J.A., 

Gutmacher, C.E., Wong, F.L., and Normark, W.R., 2009, Natural offshore seepage and related tarball 

accumulation on the California coastline, Santa Barbara Channel and the southern Santa Maria 

Basin—Source identification and inventory: U.S. Geological Survey Open-File Report 2009–1225 [also 

released as Minerals Management Service Report 2009–030], 116 p., available at http://pubs.usgs.gov/of/

2009/1225/.

Lorenson, T.D., Leifer, I., Wong, F.L., Rosenbauer, R.J., Campbell, P.L., Lam, A., Hostettler, F.D., Greinert, J., 

Finlayson, D.P., Bradley, E.S., and Luyendyk, B.P., 2011, Biomarker chemistry and flux quantification 

methods for natural petroleum seeps and produced oils, offshore southern California: U.S. Geological 

Survey Scientific Investigations Report 2011–5210 [also released as Bureau of Ocean Energy 

Management OCS Study BOEM 2011–016], 45 p., available at http://pubs.usgs.gov/sir/2011/5210/. 

Peters, K.E., Hostettler, F.D., Lorenson, T.D., and Rosenbauer, R.R., 2008, Families of Miocene Monterey 

crude oil, seep, and tarball samples, coastal California: American Association of Petroleum Geology 

Bulletin, v. 92, no. 9, p. 1,131–1,152.

Wilkinson, E.R., 1971, California offshore oil and gas seeps, in California oil fields—Summary of operations: 

California Division of Oil and Gas, v. 57, p. 5–28.

Wilkinson, E.R., 1972, California offshore oil and gas seeps: California Division of Oil and Gas,16 p.

1

U.S. Geological Survey;

2

University of California, Santa Barbara, Marine Science Institute;

3

Stanford University;

4

CE2 Corporation

Natural Offshore Hydrocarbon Seepage and Related Tarball Accumulation, Offshore of Coal Oil Point Map Area, California 

By

Thomas D. Lorenson,1 Florence L. Wong,1 Ira Leifer,2 Frances D. Hostettler,1 Kenneth E. Peters,3 Keith A. Kvenvolden,1 Robert J. Rosenbauer,1 and Grace Fong4

2014

ONE MILE = 0.869 NAUTICAL MILES

BATHYMETRIC CONTOUR INTERVALS 10 AND 50 METERS

1 .5 0 1 KILOMETER

1000 0 1000 2000 3000 4000 5000 6000 7000 FEET

1 1/2 0 1 MILE

SCALE 1:24 000

APPROXIMATE MEAN

DECLINATION, 2014

MAGNETIC NORTH

12 / ° 1 2

TRUE NORTH

Hydrocarbon seepages and tarball accumulations mapped 

by Thomas D. Lorenson and others, 2001-2011. Bathymetric 

contours by Andrew C. Ritchie, 2011 

GIS database and digital cartography by Florence L. Wong

Edited by Taryn A. Lindquist

Manuscript approved for publication June 2, 2014

Onshore elevation data from NOAA Coastal Services Center (data collected by 

EarthData International in 2002-2003) and from U.S. Army Corps of Engineers 

(data collected by Fugro Pelagos in 2009). California's State Waters limit from 

NOAA Office of Coast Survey

Universal Transverse Mercator projection, Zone 11N

NOT INTENDED FOR NAVIGATIONAL USE

10

20

30

40

50

60

70

80

100

90

150

200

250

250

Goleta Point

Coal Oil Point

Isla Vista

Goleta

Naples

04-274B

04-274A

04-272

04-271

04-268

05-88

04-273

04-270

04-269

09-104

08-236

08-235

06-63

06-62

05-341

05-340

05-339

05-91

02-86

02-85

04-35

05-95

05-96

05-351

04-3

04-2

05-347

06-67

06-66

06-69

06-68

05-342

05-338

05-337

02-176

02-175

02-174

02-173

02-177

02-172

00-201

03-92

03-129

02-261

02-155

03-172

06-65

05-94

06-71

06-70

06-64

03-192 03-145

03-144

03-141

03-128

02-235

02-31

02-33

02-141

03-130

03-27

03-131

02-200

02-32

03-55

09-103

08-237

02-100

03-132

03-89

02-271

02-98

02-152

06-78

98-138

03-91

06-73

06-72

08-234

03-195 05-350

04-1

98-79/108

08-231

08-232 09-115

08-233 09-116

02-99

03-90

06-85

06-84

06-83

06-82

06-81

06-80

06-79

06-77

06-76

06-75

06-74

98-136

98-135

10-159

09-113

05-345

05-92

99-129

98-132

98-131

98-130

05-90

98-134

05-93

09-114

03-193

97-15

09-109

La Goleta

Glen Annie

(Abandoned)

Naples Offshore

(Abandoned)

Naples Offshore

(Abandoned)

Las Varas Canyon 

(Abandoned)

Goleta

(Abandoned)

Ellwood

Glen Annie

 (Abandoned)

Ellwood,

Offshore Area

Ellwood,

Offshore Area

Ellwood,

South Offshore

Goleta Pier

Depressions Brian

Storke

Cliffhouse

Sands

Farrar

Ira

Patch

La Goleta

HolOil

CDOG

Shane

IV Super Tonya

Horseshoe

Trilogy

Seep

Tent

Jackpot

Area 1

Area 2

Area 3

Area 4

Platform

Holly

Figure 1. Water-column, bottom-bounce, normalized-sonar-return amplitude map of seep-bubble plumes (blue asterisks) in Coal Oil Point seep field, Santa Barbara 

Channel, California. Logarithmic color scale indicates normalized values for sonar-return of gas-emission intensity of plumes. From Leifer and others (2010).

Ira CDOG

Brian

Sands Shane

Tonya

Patch

Storke

Farrar

HolOil

Jackpot

Trilogy

IV Super

Horseshoe

Seep Tent

La Goleta

Cliffhouse

Goleta Pier

Depressions

Platform 

Holly

k

k

k

119°54' 119°52' 119°50'

34°24' 34°22'

Logarithmic color scale, 

σ

0.010

0.020

0.035

0.050

0.100

0.150

0 0.5 1 2 KILOMETERS

Figure 2. Composite water-column image from several multibeam-sonar passes over “Trilogy” seep, 

showing gas plumes rising from seafloor (at about 50 m water depth) to sea surface. Amplitude of 

plumes corresponds qualitatively to bubble density; geometry of seep emissions corresponds to 

geology of seafloor; shapes of plumes in water column show downcurrent deflection to northwest. 

Quantitative gas-emission rates can be determined if calibration of sonar response to bubble size, 

bubble density, and three-dimensional volume of seep plume in water column is known. Dimensions 

of block, 600 × 300 × 50 m. Image provided by David P. Finlayson (USGS).

Trilogy Seep, Coal Oil Point, Santa Barbara

June 18, 2010

USGS

Reson, Inc. 7125 Multibeam

Amplitude

1

126

251

375

500

Northing (m)

200

300

400

100

200

300

400

500

Easting (m)

120° 119°55' 119°50'

34°30'

34°25'

120° 119°55' 119°50'

34°25'

Scientific Investigations Map 3302

Sheet 11 of 12

Pamphlet accompanies map

U.S. Department of the Interior

U.S. Geological Survey