California State Waters Map Series—Offshore of Santa 

Barbara, California

By Samuel Y. Johnson, Peter Dartnell, Guy R. Cochrane, Nadine E. Golden, Eleyne L. Phillips, Andrew C. Ritchie, 

H. Gary Greene, Lisa M. Krigsman, Rikk G. Kvitek, Bryan E. Dieter, Charles A. Endris, Gordon G. Seitz, Ray W. 

Sliter, Mercedes D. Erdey, Carlos I. Gutierrez, Florence L. Wong, Mary M. Yoklavich, Amy E. Draut, Patrick E. Hart, 

and James E. Conrad

(Samuel Y. Johnson and Susan A. Cochran, editors)

Pamphlet to accompany 

Scientific Investigations Map 3281 

2013

U.S. Department of the Interior 

U.S. Geological Survey 
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

For more information on the USGS—the Federal source for science about the Earth,

its natural and living resources, natural hazards, and the environment—visit 

http://www.usgs.gov or call 1–888–ASK–USGS

For an overview of USGS information products, including maps, imagery, and publications,

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Suggested citation:

Johnson, S.Y., Dartnell, P., Cochrane, G.R., Golden, N.E., Phillips, E.L., Ritchie, A.C., Greene, H.G., Krigsman, 

L.M., Kvitek, R.G., Dieter, B.E., Endris, C.A., Seitz, G.G., Sliter, R.W., Erdey, M.E., Gutierrez, C.I., Wong, F.L., 

Yoklavich, M.M., Draut, A.E., Hart, P.E., and Conrad, J.E. (S.Y. Johnson and S.A. Cochran, eds.), 2013, California 

State Waters Map Series—Offshore of Santa Barbara, California: U.S. Geological Survey Scientific Investigations 

Map 3281, 45 p., 11 sheets, scale 1:24,000, http://dx.doi.org/10.3133/sim3281. 

ISSN 2329-132X (online)

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
iii

Contents

Preface...........................................................................................................................................................................1

Chapter 1. Introduction...................................................................................................................................................3

By Samuel Y. Johnson

Publication Summary..................................................................................................................................................5

Chapter 2. Bathymetry and Backscatter-Intensity Maps of the Offshore of Santa Barbara Map Area (Sheets 1, 2, 

and 3).............................................................................................................................................................................8

By Peter Dartnell and Rikk Kvitek

Chapter 3. Data Integration and Visualization for the Offshore of Santa Barbara Map Area (Sheet 4) ........................11

By Peter Dartnell

Chapter 4. Seafloor-Character Map of the Offshore of Santa Barbara Map Area (Sheet 5).........................................12

By Eleyne L. Phillips, Mercedes D. Erdey, and Guy R. Cochrane

Chapter 5. Ground-Truth Studies for the Offshore of Santa Barbara Map Area (Sheet 6) ...........................................17

By Nadine E. Golden and Guy R. Cochrane

Chapter 6. Potential Marine Benthic Habitat Map of the Offshore of Santa Barbara Map Area (Sheet 7)....................20

By H. Gary Greene, Bryan E. Dieter, and Charles A. Endris

Classifying Potential Marine Benthic Habitats ..........................................................................................................20

Examples of Attribute Coding ...................................................................................................................................23

Map Area Habitats....................................................................................................................................................24

Chapter 7. Subsurface Geology and Structure of the Offshore of Santa Barbara Map Area and the Santa Barbara 

Channel Region (Sheets 8 and 9)................................................................................................................................25

By Samuel Y. Johnson, Eleyne L. Phillips, Andrew C. Ritchie, Florence L. Wong, Ray W. Sliter, Amy 

E. Draut, Patrick E. Hart, and James E. Conrad

Data Acquisition........................................................................................................................................................25

Seismic-Reflection Imaging of the Continental Shelf................................................................................................26

Geologic Structure and Recent Deformation ............................................................................................................26

Thickness and Depth to Base of Uppermost Pleistocene and Holocene Deposits ...................................................27

Chapter 8. Geologic and Geomorphic Map of the Offshore of Santa Barbara Map Area (Sheet 10) ...........................30

By Samuel Y. Johnson, Andrew C. Ritchie, James E. Conrad, Eleyne L. Phillips, Gordon G. Seitz, 

and Carlos I. Gutierrez

Geologic and Geomorphic Summary........................................................................................................................30

Description of Map Units ..........................................................................................................................................32

Offshore Geologic and Geomorphic Units ............................................................................................................32

Onshore Geologic and Geomorphic Units ............................................................................................................33

Chapter 9. Predictive Distribution of Benthic Macro-Invertebrates for the Offshore of Santa Barbara Map Area and 

the Santa Barbara Channel Region (Sheet 11)............................................................................................................37

By Lisa M. Krigsman, Mary M. Yoklavich, Nadine E. Golden, and Guy R. Cochrane

Acknowledgments........................................................................................................................................................39

References Cited .........................................................................................................................................................40

Figures

Figure 1–1. Physiography of Santa Barbara Channel region......................................................................................... 6

Figure 1–2. Coastal geography of Offshore of Santa Barbara map area....................................................................... 7

Figure 4–1. Detailed view of ground-truth data, showing accuracy-assessment methodology.................................... 14

Figure 5–1. Photograph of camera sled used in USGS 2008 ground-truth survey ...................................................... 17
iv

Figure 5–2. Graph showing distribution of primary and secondary substrate determined from video observations in 

Offshore of Santa Barbara map area........................................................................................................ 19

Tables

Table 4–1. Conversion table showing how video observations of primary substrate, secondary substrate, and 

abiotic seafloor complexity are grouped into seafloor-character-map Classes I, II, and III for use in 

supervised classification and accuracy assessment................................................................................. 15

Table 4–2. Accuracy-assessment statistics for seafloor-character-map classifications.............................................. 16

Table 7–1. Area, sediment-thickness, and sediment-volume data for California’s State Waters in Santa Barbara 

Channel region, as well as in Offshore of Santa Barbara map area. ........................................................ 29

Table 8–1. Areas and relative proportions of offshore geologic map units in Offshore of Santa Barbara map area... 31

Map Sheets

Sheet 1. Colored Shaded-Relief Bathymetry, Offshore of Santa Barbara Map Area, California

By Rikk G. Kvitek, Peter Dartnell, Eleyne L. Phillips, and Guy R. Cochrane 

Sheet 2. Shaded-Relief Bathymetry, Offshore of Santa Barbara Map Area, California 

By Rikk G. Kvitek, Peter Dartnell, Eleyne L. Phillips, and Guy R. Cochrane 

Sheet 3. Acoustic Backscatter, Offshore of Santa Barbara Map Area, California 

By Peter Dartnell, Rikk G. Kvitek, Eleyne L. Phillips, and Guy R. Cochrane 

Sheet 4. Data Integration and Visualization, Offshore of Santa Barbara Map Area, California 

By Peter Dartnell 

Sheet 5. Seafloor Character, Offshore of Santa Barbara Map Area, California 

By Eleyne L. Phillips, Mercedes D. Erdey, and Guy R. Cochrane 

Sheet 6. Ground-Truth Studies, Offshore of Santa Barbara Map Area, California 

By Nadine E. Golden, Guy R. Cochrane, and Lisa M. Krigsman 

Sheet 7. Potential Marine Benthic Habitats, Offshore of Santa Barbara Map Area, California 

By Bryan E. Dieter, Charles A. Endris, H. Gary Greene, Nadine E. Golden, and Mercedes D. Erdey 

Sheet 8. Seismic-Reflection Profiles, Offshore of Santa Barbara Map Area, California 

By Samuel Y. Johnson, Ray W. Sliter, Andrew C. Ritchie, Amy E. Draut, Patrick E. Hart, Eleyne L. 

Phillips, and James E. Conrad 

Sheet 9. Local (Offshore of Santa Barbara Map Area) and Regional (Offshore from Refugio Beach to Hueneme 

Canyon) Shallow-Subsurface Geology and Structure, Santa Barbara Channel, California 

By Samuel Y. Johnson, Eleyne L. Phillips, Andrew C. Ritchie, Florence L. Wong, Ray W. Sliter, Amy 

E. Draut, James E. Conrad, and Patrick E. Hart 

Sheet 10. Offshore and Onshore Geology and Geomorphology, Offshore of Santa Barbara Map Area, California 

By Samuel Y. Johnson, Andrew C. Ritchie, Gordon G. Seitz, Carlos I. Gutierrez, James E. Conrad, 

and Eleyne L. Phillips

Sheet 11. Predicted Distribution of Benthic Macro-Invertebrates, Offshore of Santa Barbara Map Area and Santa 

Barbara Channel Region, California

By Lisa M. Krigsman, Mary M. Yoklavich, Guy R. Cochrane, and Nadine E. Golden
1

California State Waters Map Series—Offshore of Santa 

Barbara, California

By Samuel Y. Johnson,1 Peter Dartnell,1 Guy R. Cochrane,1 Nadine E. Golden,1 Eleyne L. Phillips,1 Andrew C. 

Ritchie,1 H. Gary Greene,2 Lisa M. Krigsman,3 Rikk G. Kvitek,4 Bryan E 2 . Dieter, Charles A. Endris,2 Gordon G. 

Seitz,5 Ray W. Sliter,1 Mercedes D. Erdey,1 Carlos I. Gutierrez,5 Florence L. Wong,1 Mary M. Yoklavich,3 Amy E. 

Draut,1 Patrick E. Hart,

1 and James E. Conrad1 

(Samuel Y. Johnson1 and Susan A. Cochran,1 editors)

Preface 

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping 

Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, 

marine benthic habitats, and geology within California’s State Waters. The program supports a large 

number of coastal-zone- and ocean-management issues, including the California Marine Life Protection 

Act (MLPA) (California Department of Fish and Game, 2008), which requires information about the 

distribution of ecosystems as part of the design and proposal process for the establishment of Marine 

Protected Areas. A focus of CSMP is to map California’s State Waters with consistent methods at a 

consistent scale.

The CSMP approach is to create highly detailed seafloor maps through collection, integration, 

interpretation, and visualization of swath sonar bathymetric data (the undersea equivalent of satellite 

remote-sensing data in terrestrial mapping), acoustic backscatter, seafloor video, seafloor photography, 

high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products 

display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both 

the surficial seafloor geology and shallow (to about 100 m) subsurface geology. It is emphasized that the 

more interpretive habitat and geology maps rely on the integration of multiple, new high-resolution 

datasets and that mapping at small scales would not be possible without such data. 

This approach and CSMP planning is based in part on recommendations of the Marine Mapping 

Planning Workshop (Kvitek and others, 2006), attended by coastal and marine managers and scientists 

from around the state. That workshop established geographic priorities for a coastal mapping project and 

identified the need for coverage of “lands” from the shore strand line (defined as Mean Higher High 

Water; MHHW) out to the 3-nautical-mile (5.6-km) limit of California’s State Waters. Unfortunately, 

surveying the zone from MHHW out to 10-m water depth is not consistently possible using ship-based 

surveying methods, owing to sea state (for example, waves, wind, or currents), kelp coverage, and 

shallow rock outcrops. Accordingly, some of the maps presented in this series commonly do not cover 

the zone from the shore out to 10-m depth; these “no data” zones appear pale gray on most maps. 

This map is part of a series of online U.S. Geological Survey (USGS) publications, each of 

which includes several map sheets, some explanatory text, and a descriptive pamphlet. Each map sheet 

 

1 U.S. Geological Survey

2 Moss Landing Marine Laboratories, Center for Habitat Studies 3 National Oceanic and Atmospheric Administration, National Marine Fisheries Service

4 California State University Monterey Bay, Seafloor Mapping Lab

5 California Geological Survey
2

is published as a PDF file. Geographic information system (GIS) files that contain both ESRI6

The California Seafloor Mapping Program (CSMP) is a collaborative venture between numerous 

different federal and state agencies, academia, and the private sector. CSMP partners include the 

California Coastal Conservancy, the California Ocean Protection Council, the California Department of 

Fish and Game, the California Geological Survey, California State University at Monterey Bay’s 

Seafloor Mapping Lab, Moss Landing Marine Laboratories Center for Habitat Studies, Fugro Pelagos, 

Pacific Gas and Electric Company, National Oceanic and Atmospheric Administration (NOAA, 

including National Ocean Service – Office of Coast Surveys, National Marine Sanctuaries, and National 

Marine Fisheries Service), U.S. Army Corps of Engineers, the Bureau of Ocean Energy Management, 

the National Park Service, and the U.S. Geological Survey. 

ArcGIS 

raster grids (for example, bathymetry, seafloor character) and geotiffs (for example, shaded relief) are 

also included for each publication. For those who do not own the full suite of ESRI GIS and mapping 

software, the data can be read using ESRI ArcReader, a free viewer that is available at 

http://www.esri.com/software/arcgis/arcreader/index.html (last accessed March 5, 2013). 

 

6 Environmental Systems Research Institute, Inc.
3

Chapter 1. Introduction

By Samuel Y. Johnson 

The map area offshore of Santa Barbara, California, which is referred to herein as the “Offshore 

of Santa Barbara” map area (figs. 1–1, 1–2), lies within the central Santa Barbara Channel region of the 

Southern California Bight (see, for example, Lee and Normark, 2009). This geologically complex region 

forms a major biogeographic marine transition zone, separating the cold-temperate Oregonian province 

north of Point Conception from the warm-temperate California province to the south (Briggs, 1974). 

The city of Santa Barbara (population, about 92,000) is the main coastal population center, part 

of a contiguous urban area (population, about 220,000) that extends from Carpinteria to Goleta (fig. 

1–1). This urban area was developed south of the east-west-trending Santa Ynez Mountains on 

coalescing alluvial surfaces, uplifted marine terraces, and low (elevations as high as about 130 m), eastwest-trending hills underlain by folded and faulted Miocene bedrock (Minor and others, 2009). The crest 

of the Santa Ynez Mountains, about 1,100 m high, lies about 11 km north of the shoreline. 

The Santa Barbara coastal zone is actively utilized. Development of the Santa Barbara Harbor 

began in 1928 (Griggs and others, 2005). The initial breakwater trapped sand, leading to shoaling within 

and west of the harbor, as well as coastal erosion east of the harbor. Annual harbor dredging, which

began in 1959, averages about 400,000 tons/yr, mitigating at least some of the downcoast erosion 

problem. Beach recreation is popular in the Offshore of Santa Barbara map area, at sites such as Arroyo 

Burro Beach Park and Leadbetter Beach, west of the harbor, and East Beach and “Butterfly Beach” east 

of the harbor; “Hammonds Reef” offshore of Montecito is a well-known surfing locale (fig. 1–2).

The Offshore of Santa Barbara map area lies in the central part of the Santa Barbara littoral cell 

(fig. 1–1), which is characterized by west-to-east transport of sediment from Point Arguello on the 

northwest to Hueneme and Mugu Canyons on the southeast (see, for example, Griggs and others, 2005; 

Hapke and others, 2006). On the basis of harbor dredging records, Griggs and others (2005) reported 

east-southeast longshore drift rates that range from about 160,000 to 800,000 tons/yr, averaging 400,000 

tons/yr. At the east end of the littoral cell, eastward-moving sediment is trapped by Hueneme and Mugu 

Canyons (fig. 1–1) and then transported down these canyons into the deep-water Santa Monica Basin 

(Normark and others, 2009). 

Sediment supply to the western and central part of the littoral cell is mainly from relatively small 

coastal watersheds, which have an estimated cumulative annual sediment flux of 640,000 tons/yr 

between Point Arguello and the Ventura River (Warrick and Farnsworth, 2009). Within the Offshore of 

Santa Barbara map area, these coastal watersheds include (from east to west) San Ysidro Creek, Oak 

Creek, Montecito Creek, Sycamore Creek, Mission Creek, Arroyo Burro, and Atascadero Creek (fig. 

1–2). The much larger Ventura and Santa Clara Rivers, the mouths of which are 40 to 50 km southeast 

of Santa Barbara, yield an estimated 3.4 million tons of sediment annually (Warrick and Farnsworth, 

2009), the coarser sediment load generally moving southeast down the coast and the finer sediment load 

moving both upcoast and offshore (Drake, 1972; Warrick and Farnsworth, 2009). Coastal-watershed 

discharge and sediment load are highly variable, characterized by brief large events during major winter 

storms and long periods of low flow and minimal sediment load between storms. In recent history, the 

majority of high-discharge, high-sediment-flux events have been associated with El Niño phases of the 

El Niño–Southern Oscillation (ENSO) climatic pattern (Warrick and Farnsworth, 2009). 

Narrow beaches and cliffs characterize much of the shoreline in the Offshore of Santa Barbara 

map area. Continuing coastal erosion problems in the area are associated with both development and 

natural processes (summarized in Griggs and others, 2005; Barnard and others, 2009); cliff erosion is 

occurring at rates of about 0.1 to 1 m/yr over the period between 1933–1934 and 1998, the largest 

amount (63 m) occurring at Arroyo Burro in the western part of the map area (Hapke and Reid, 2007). 
4

Hapke and others (2006, their fig. 35) suggested that beaches in this area have a mixed erosional to 

accretionary history over the long term (between the mid-1800s and 1998) but an erosional trend over 

the short term (from the mid-1970s to 1998). 

The Offshore of Santa Barbara map area consists of relatively flat and shallow continental shelf. 

The shelf dips gently seaward (about 0.4° to 0.8°), so that water depths at the 3-nautical-mile (5.6-km) 

limit of California’s State Waters range from about 45 m (at the eastern map margin) to about 75 m (at 

the western map margin). The shelf break is about 7 to 12 km south of the shoreline (outside the map 

area), at water depths of about 90 to 100 m. This part of the Southern California Bight is relatively well 

protected from large Pacific swells from the north and northwest by Point Conception and from the 

south and southwest by offshore islands and banks (O’Reilly and Guza, 1993). Fair-weather wave base 

is typically shallower than 20-m water depth, but winter storms are capable of resuspending fine-grained 

sediments in 30 m of water (Xu and Noble, 2009, their table 7), and so shelf sediments in the map area 

probably are remobilized on an annual basis. As with sediment discharge from rivers, the largest wave 

events and the highest sediment transport rates on the shelf are typically associated with ENSO events. 

The shelf is underlain by variable amounts (0 to 14 m) of upper Quaternary shelf, estuarine, and fluvial 

sediments deposited as sea level fluctuated in the late Pleistocene (see sheet 9 of this report; see also, 

Dahlen, 1992; Slater and others, 2002; Draut and others, 2009). 

The Offshore of Santa Barbara map area lies within the Shelf (continental shelf) megahabitat of 

Greene and others (2007). Habitat types range from soft, unconsolidated sediment to hard sedimentary 

bedrock. Some bedrock outcrops are covered by a thin ephemeral sediment layer, producing a mixed 

hard-soft habitat type. This heterogeneous seafloor provides promising habitat for rockfish (Sebastes

spp.), groundfish, crabs, shrimp, and other marine benthic organisms. 

The Offshore of Santa Barbara map area is in the Ventura Basin, in the southern part of the 

Western Transverse Ranges geologic province, which is north of the California Continental Borderland7

Uplift rates that are based on studies of onland marine terraces provide further evidence of 

significant shortening. Trecker and others (1998) and Keller and Gurrola (2000) mapped flights of four 

to five uplifted marine terraces along much of this coast, which range in elevation from 36 to 143 m; 

these terraces are inferred to have formed during the sea-level highstands of marine oxygen-isotopic 

stages 7 (about 160,000 to 250,000 years ago), 5 (about 80,000 to 120,000 years ago), and 3 (about 

35,000 to 70,000 years ago) (Chappell, 1983; Chappell and Shackleton, 1986). The presence of 

emergent stage 3 terraces, which are uncommon along the California coast, requires rapid uplift: 

estimated rates of uplift (based on marine terrace elevations and geochronology) range from 0.7+0.1 

mm/yr at Summerland, a few kilometers east of the map area (fig. 1–1), to 2.2+0.3 mm/yr at More Mesa, 

in the western part of the map area (fig. 1–2). 

(Fisher and others, 2009). Significant clockwise rotation—at least 90°—since the early Miocene has 

been proposed for the Western Transverse Ranges province (Luyendyk and others, 1980; Hornafius and 

others, 1986; Nicholson and others, 1994), and this region is presently undergoing north-south 

shortening (see, for example, Larson and Webb, 1992). In the map area, this shortening is 

accommodated by west- to northwest-striking, north-dipping (for example, Red Mountain Fault) and 

south-dipping (for example, Rincon Creek Fault) blind structures, as well as by fault-related folding. 

Cross sections by Redin (2005) and Redin and others (2005) suggest that these contractional faults 

merge at depth (about 5 to 6 km deep), and they further suggest that these structures have a component 

of left-lateral slip. 

Fault-related structures have controlled the origins of offshore oil fields in the map area 

(Kunitomi and others, 1998; Heck, 1998). The offshore Summerland oil field is in the uplifted block 

 

7 The California Continental Borderland is defined as the complex continental margin that extends from Point Conception 

south into northern Baja California.
5

between the Red Mountain and Rincon Creek Faults. To the south and east of the map area, the Rincon 

Anticline hosts the offshore Rincon, Carpinteria, and Dos Cuadras oil fields. Similarly, to the west of the 

map area, the Coal Oil Point and South Ellwood oil fields lie along anticlines. No hydrocarbon 

development or production has occurred in the map area’s state waters, which are part of the protected 

California Coastal Sanctuary, established in 1955, that extends from Summerland on the east to Goleta 

on the west (fig. 1–1). However, an oil-well drilling accident in 1969 in the newly discovered Dos 

Cuadras oil field, in federal waters about 10 km due south of Santa Barbara, led to the Santa Barbara oil 

spill, a leak of between 7,000 and 70,000 barrels (Galloway, 1998). Public reaction to the spill is 

credited for a host of new environmental laws and regulations (Clarke and Hemphill, 2002). 

Publication Summary 

This publication about the Offshore of Santa Barbara map area includes eleven map sheets that 

contain explanatory text, in addition to this descriptive pamphlet and a data catalog of geographic 

information system (GIS) files. Sheets 1, 2, and 3 combine data from four different sonar surveys to 

generate comprehensive high-resolution bathymetry and acoustic-backscatter coverage of the map area. 

These data reveal a range of physiographic features (highlighted in the perspective views on sheet 4) 

such as the flat, sediment-covered Santa Barbara shelf interspersed with tectonically controlled bedrock 

uplifts, coarse-grained deltas and sediment lobes associated with coastal watersheds, and patches of 

irregular seafloor related to hydrocarbon seeps. To validate the geological and biological interpretations 

of the sonar data shown on sheets 1, 2, and 3, the U.S. Geological Survey towed a camera sled over 

specific offshore locations, collecting both video and photographic imagery; this “ground-truth” 

surveying data is summarized on sheet 6. Sheet 5 is a “seafloor character” map, which classifies the 

seafloor on the basis of depth, slope, rugosity (ruggedness), and backscatter intensity and which is 

further informed by the ground-truth-survey imagery. Sheet 7 is a map of “potential habitats,” which are 

delineated on the basis of substrate type, geomorphology, seafloor process, or other attributes that may 

provide a habitat for a specific species or assemblage of organisms. Sheet 8 compiles representative 

seismic-reflection profiles from the map area, providing information on the subsurface stratigraphy and 

structure of the map area. Sheet 9 shows the distribution and thickness of young sediment (deposited 

over the last about 21,000 years, during the most recent sea-level rise) in both the map area and the 

larger Santa Barbara Channel region (offshore from Refugio Beach to Hueneme Canyon), interpreted on 

the basis of the seismic-reflection data. Sheet 10 is a geologic map that merges onshore geologic 

mapping (compiled from existing maps by the California Geological Survey) and new offshore geologic

mapping that is based on the integration of high-resolution 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). Sheet 11 uses the ground-truth-survey 

imagery to develop a statistical model and maps that predict the distribution of benthic macroinvertebrates for both the Offshore of Santa Barbara map area and the Santa Barbara Channel region. 

The information provided by the map sheets, pamphlet, and data catalog have a broad range of 

applications. High-resolution bathymetry, acoustic backscatter, ground-truth-surveying imagery, habitat 

mapping, and maps of predicted species distribution all contribute to habitat characterization and 

ecosystem-based management by providing essential data for delineation of marine protected areas and 

ecosystem restoration. Many of the maps provide high-resolution baselines that will be critical for 

monitoring environmental change associated with climate change, coastal development, or other 

forcings. High-resolution bathymetry is a critical component for modeling coastal flooding caused by

storms and tsunamis, as well as inundation associated with longer term sea-level rise. Seismic-reflection 

and bathymetric data help characterize earthquake and tsunami sources, critical for natural-hazard 

assessments of coastal zones. Information on sediment distribution and thickness is essential to the 
6

understanding of local and regional sediment transport, as well as the development of regional sedimentmanagement plans. In addition, siting of any new offshore infrastructure (for example, pipelines, cables, 

or renewable-energy facilities) will depend on high-resolution mapping. Finally, this mapping will both 

stimulate and enable new scientific research and also raise public awareness of, and education about, 

coastal environments and issues. 

Figure 1–1. Physiography of Santa Barbara Channel region. Box shows Offshore of Santa Barbara map area. 

Arrows show direction of sediment transport in Santa Barbara littoral cell, which extends from Point Arguello 

(PA) to Hueneme Canyon (HC) and Mugu Canyon (MC). Other abbreviations: C, Carpinteria; CC, Calleguas 

Creek; G, Goleta; O, Oxnard; PC, Point Conception; S, Summerland; SB, Santa Barbara; SBB, Santa Barbara 

Basin; SM, Santa Monica Mountains; SMB, Santa Monica Basin; SR, Santa Clara River; SYM, Santa Ynez 

Mountains; V, Ventura; VR, Ventura River.
7

Figure 1–2. Coastal geography of Offshore of Santa Barbara map area. Abbreviations: AB, Arroyo Burro; ABB, 

Arroyo Burro Beach Park; AC, Atascadero Creek; BB, “Butterfly Beach;” EB, East Beach; FP, Fernald Point; 

HR, “Hammonds Reef;” LB, Leadbetter Beach; MC, Mission Creek; MM, More Mesa; MoC, Montecito Creek; 

OC, Oak Creek; SBH, Santa Barbara Harbor; SC, Sycamore Creek; SYC, San Ysidro Creek. Yellow line is 

3-nautical-mile limit of California’s State Waters.
8

Chapter 2. Bathymetry and Backscatter-Intensity Maps of the Offshore 

of Santa Barbara Map Area (Sheets 1, 2, and 3)

By Peter Dartnell and Rikk Kvitek

The colored shaded-relief bathymetry (sheet 1), the shaded-relief bathymetry (sheet 2), and the 

acoustic-backscatter (sheet 3) maps of the Offshore of Santa Barbara map area in southern California 

were generated from bathymetry and backscatter data collected by California State University, Monterey 

Bay (CSUMB), by the U.S. Geological Survey (USGS), and by Fugro Pelagos for the U.S. Army Corps 

of Engineers (USACE) Joint Lidar Bathymetry Technical Center of Expertise (fig. 1 on sheets 1, 2, 3). 

Most of the offshore area was mapped by CSUMB in the summer of 2007, using a 244-kHz Reson 8101 

multibeam echosounder. Smaller areas in the far-east nearshore, as well as further offshore to the west

and in the southeast outer shelf area, were mapped by the USGS in 2005 and 2006, using a combination 

of 468-kHz (2005) and 117-kHz (2006) SEA (AP) Ltd. SWATHplus-M phase-differencing sidescan 

sonars. The nearshore bathymetry and coastal topography were mapped for USACE by Fugro Pelagos in 

2009, using the SHOALS-1000T bathymetric-lidar and Leica ALS60 topographic-lidar systems. These 

mapping missions combined to collect bathymetry (sheets 1, 2) from the 0-m isobath to beyond the 

3-nautical-mile limit of California’s State Waters, as well as acoustic-backscatter data (sheet 3) from

about the 10-m isobath to beyond the 3-nautical-mile limit.

During the CSUMB mapping mission, an Applanix position and motion compensation system

(POS/MV) was used to accurately position the vessel during data collection, and it also accounted for 

vessel motion such as heave, pitch, and roll (position accuracy, ±2 m; pitch, roll, and heading accuracy, 

±0.02°; heave accuracy, ±5%, or 5 cm). NavCom 2050 GPS receiver (CNAV) data were used to account 

for tidal-cycle fluctuations, and sound-velocity profiles were collected with an Applied Microsystems 

(AM) SVPlus sound velocimeter. Soundings were corrected for vessel motion using the Applanix 

POS/MV data, for variations in water-column sound velocity using the AM SVPlus data, and for 

variations in water height (tides) using vertical-position data from the CNAV receiver. Backscatter data 

were postprocessed using CARIS7.0/Geocoder software. Geobars were created for each survey line 

using the beam-averaging engine. Intensities were radiometrically corrected (including despeckling and 

angle-varying gain adjustments), and the position of each acoustic sample was geometrically corrected 

for slant range on a line-by-line basis. The contrast and brightness of some geobars were adjusted to 

better match the surrounding geobars. Individual geobars were mosaicked together at 2-m resolution 

using the auto-seam method. The mosaics were then exported from CARIS as georeferenced TIFF 

images, imported into a geographic information system (GIS), and converted to GRIDs. 

During the USGS mapping missions, differential GPS (DGPS) data were combined with 

measurements of vessel motion (heave, pitch, and roll) in a CodaOctopus F180 attitude-and-position 

system to produce a high-precision vessel-attitude packet. This packet was transmitted to the acquisition 

software in real time and combined with instantaneous sound-velocity measurements at the transducer 

head before each ping. The returned samples were projected to the seafloor using a ray-tracing algorithm 

that works with previously measured sound-velocity profiles. Statistical filters were applied to the raw 

samples that discriminate the seafloor returns (soundings) from unintended targets in the water column. 

Finally, the soundings were converted into 2-m-resolution bathymetric-surface-model grids. The 

backscatter data were postprocessed using USGS software (D.P. Finlayson, written commun., 2011) that 

normalizes for time-varying signal loss and beam-directivity differences. Thus, the raw 16-bit 

backscatter data were gain-normalized to enhance the backscatter of the SWATHplus system. The 

resulting normalized-amplitude values were rescaled to 16-bit and gridded into GeoJPEGs using GRID 

Processor Software, then imported into a GIS and converted to GRIDs. 
9

During the Fugro Pelagos mapping mission that was completed as part of the National Coastal 

Mapping Program of USACE, the Leica ALS60 topographic-lidar and the SHOALS-1000T 

bathymetric-lidar systems were mounted on an aircraft that flew survey lines at an altitude of 300 to 400 

m (bathymetry) and 300 to 1,200 m (topography), at speeds of between 135 and 185 knots. The ALS60 

system collected data at a maximum pulse rate of 200 kHz, and the SHOALS system collected data at 1 

kHz. Information on aircraft position, velocity, and acceleration were collected using the Novatel and 

POS A/V 410 systems (SHOALS) and the onboard GPS/IMU system (ALS60). Aircraft-position data 

were processed using POSPac software, and the results were combined with the lidar data to produce 

3-D positions for each lidar shot. Various commercial and proprietary software packages were used to 

clean the data, to convert all valid data from ellipsoid to orthometric heights, and to export the data as a 

series of topography and bathymetry ASCII files. 

Soundings from the different mapping missions were converted into individual 2-m-resolution 

bathymetric-surface-model grids. The individual bathymetric-surface models were then merged into one 

overall bathymetric-surface model and clipped to the boundary of the map area. Difference calculations 

of the overlapping bathymetry grids showed that there is good agreement between surveys, even though 

the surveys were conducted at different times using different mapping equipment. For example, a mean 

difference of 0.12 m (0.12 standard deviation) exists between the 2007 CSUMB multibeam-echosounder 

data and the overlapping 2009 USACE bathymetric-lidar data, even though the overlap is in the 

energetic nearshore region that is highly susceptible to natural change. A mean difference of 0.32 m 

(0.14 standard deviation) also is present between the 2006 USGS nearshore SWATHplus data and the 

overlapping 2007 CSUMB multibeam-echosounder data in the western part of the map area. 

An illumination having an azimuth of 300° and from 45° above the horizon was then applied to 

the bathymetric surface to create the shaded-relief imagery (sheets 1, 2). In addition, a modified 

“rainbow” color ramp was applied to the bathymetry data for sheet 1, using reds and oranges to 

represent shallower depths, and greens to represent greater depths (note that the Offshore of Santa 

Barbara map area requires only the shallower part of the full-rainbow color ramp used on some of the 

other maps in the California State Waters Map Series; see, for example, Kvitek and others, 2012). This 

colored bathymetry surface was draped over the shaded-relief imagery at 60-percent transparency to 

create a colored shaded-relief map (sheet 1).

Bathymetric contours (sheets 1, 2, 3, 7, 10) were generated from a modified bathymetric surface 

of California’s State Waters within the Santa Barbara Channel. This surface was generated by merging 

all of California Seafloor Mapping Program’s bathymetry data for the region into one surface model. 

After merging, the surface model was resampled to 10-m resolution, and then a smooth arithmetic mean 

convolution function that assigns a weight of one-ninth to each cell in a 3-pixel by 3-pixel matrix was 

applied iteratively to the surface ten times. Following smoothing, contour lines were generated at 10-m 

intervals, then the contours were clipped to the boundary of the map area. 

The acoustic-backscatter imagery from each different mapping system and processing method 

were merged into their own individual grids. These individual grids, which cover different areas, were 

displayed in a GIS to create a composite acoustic-backscatter map (sheet 3). On the map, brighter tones 

indicate higher backscatter intensity, and darker tones indicate lower backscatter intensity. The intensity 

represents a complex interaction between the acoustic pulse and the seafloor, as well as characteristics 

within the shallow subsurface, providing a general indication of seafloor texture and sediment type. 

Backscatter intensity depends on the acoustic source level; the frequency used to image the seafloor; the 

grazing angle; the composition and character of the seafloor, including grain size, water content, bulk 

density, and seafloor roughness; and some biological cover. Harder and rougher bottom types such as 

rocky outcrops or coarse sediment typically return stronger intensities (high backscatter, lighter tones), 

whereas softer bottom types such as fine sediment return weaker intensities (low backscatter, darker 
10

tones). The differences in backscatter intensity that are apparent in some areas on sheet 3 are due to the 

different frequencies of mapping systems, as well as different processing techniques. 

The onshore-area image was generated by applying an illumination having an azimuth of 300° 

and from 45° above the horizon to the coastal airborne topographic-lidar data, as well as to publicly 

available, 3-m-resolution, interferometric synthetic aperture radar (ifSAR) data, available from National 

Oceanic and Atmospheric Administration (NOAA) Coastal Service Center’s Digital Coast (National 

Oceanic and Atmospheric Administration, 2011). 
11

Chapter 3. Data Integration and Visualization for the Offshore of Santa 

Barbara Map Area (Sheet 4) 

By Peter Dartnell

Mapping California’s State Waters has produced a vast amount of acoustic and visual data, 

including bathymetry, acoustic backscatter, seismic-reflection profiles, and seafloor video and 

photography. These data are used by researchers to develop maps, reports, and other tools to assist in the 

coastal and marine spatial-planning capability of coastal-zone managers and other stakeholders. For 

example, seafloor-character (sheet 5), habitat (sheet 7), and geologic (sheet 10) maps of the Offshore of 

Santa Barbara map area may assist in the designation of Marine Protected Areas, as well as in their 

monitoring. These maps and reports also help to analyze environmental change owing to sea-level rise 

and coastal development, to model and predict sediment and contaminant budgets and transport, to site 

offshore infrastructure, and to assess tsunami and earthquake hazards. To facilitate this increased 

understanding and to assist in product development, it is helpful to integrate the different datasets and 

then view the results in three-dimensional representations such as those displayed on the data integration 

and visualization sheet for the Offshore of Santa Barbara map area (sheet 4).

The maps and three-dimensional views on sheet 4 were created using a series of geographic 

information systems (GIS) and visualization techniques. Using GIS, the bathymetric and topographic 

data (sheet 1) were converted to ASCIIRASTER format files, and the acoustic-backscatter data (sheet 3) 

were converted to geoTIFF images. The bathymetric and topographic data were imported in the 

Fledermaus software (QPS). The bathymetry was color-coded to closely match the colored shadedrelief bathymetry on sheet 1 in which reds and oranges represent shallower depths and greens represent 

deeper depths. Topographic data were shown in gray shades. The acoustic-backscatter geoTIFF images 

were also draped over the bathymetry data. The colored bathymetry, topography, and draped backscatter 

were then tilted and panned to create the perspective views such as those shown in figures 1, 2, 3, 5, and 

6 on sheet 4. These figures highlight the relatively low relief of seafloor features located offshore of the 

Santa Barbara area. 

Video-mosaic images created from digital seafloor video (for example, figs. 4 and 7 on sheet 4) 

display the geologic complexity (rock, sand, and mud; see sheet 10) and biologic complexity (see sheet 

11) of the seafloor. Whereas photographs capture high-quality snapshots of smaller areas of the seafloor 

(see sheet 6), video mosaics capture larger areas and can show transition zones between seafloor 

environments. Digital seafloor video is collected from a camera sled towed approximately 1 to 2 meters 

over the seafloor, at speeds of less than 1 nautical mile/hour. Using standard video-editing software, as 

well as software developed at the Center for Coastal and Ocean Mapping, University of New 

Hampshire, the digital video is converted to AVI format, cut into 2-minute sections, and desampled to 

every second or third frame. The frames are merged together using pattern-recognition algorithms from 

one frame to the next and converted to a TIFF image. The images are then rectified to the bathymetry 

data using ship navigation recorded with the video and layback estimates. 

Block diagrams that combine the bathymetry with seismic-reflection-profile data help integrate 

surface and subsurface observations, especially stratigraphic and structural relations (for example, fig. 1

on sheet 4). These block diagrams were created by converting digital seismic-reflection-profile data 

(Sliter and others, 2008) into TIFF images, while taking note of the starting and ending coordinates and 

maximum and minimum depths. The images were then imported into the Fledermaus software as 

vertical images and merged with the bathymetry imagery.
12

Chapter 4. Seafloor-Character Map of the Offshore of Santa Barbara 

Map Area (Sheet 5)

By Eleyne L. Phillips, Mercedes D. Erdey, and Guy R. Cochrane

The California State Marine Life Protection Act (MLPA) calls for protecting representative types 

of habitat in different depth zones and environmental conditions. A science team, assembled under the 

auspices of the California Department of Fish and Game (CDFG), has identified seven substrate-defined 

seafloor habitats in California’s State Waters that can be classified using sonar data and seafloor video 

and photography. These habitats include rocky banks, intertidal zones, sandy or soft ocean bottoms, 

underwater pinnacles, kelp forests, submarine canyons, and seagrass beds. The following five depth 

zones, which determine changes in species composition, have been identified: Depth Zone 1, intertidal; 

Depth Zone 2, intertidal to 30 m; Depth Zone 3, 30 to 100 m; Depth Zone 4, 100 to 200 m; and Depth 

Zone 5, deeper than 200 m (California Department of Fish and Game, 2008). The CDFG habitats, with 

the exception of depth zones, can be considered a subset of a broader classification scheme of Greene 

and others (1999) that has been used by the U.S. Geological Survey (USGS) (Cochrane and others, 

2003, 2005). These seafloor-character maps are generalized polygon shapefiles that have attributes 

derived from Greene and others (2007). 

A 2007 Coastal Map Development Workshop, hosted by the USGS in Menlo Park, California, 

identified the need for more detailed (relative to Greene and others’ [1999] attributes) raster products 

that preserve some of the transitional character of the seafloor when substrates are mixed and (or) they 

change gradationally. The seafloor-character map, which delineates a subset of the CDFG habitats, is a 

GIS-derived raster product that can be produced in a consistent manner from data of variable quality 

covering large geographic regions.

The following six substrate classes are identified in the Offshore of Santa Barbara map area:

• Class I: Fine- to medium-grained smooth sediment 

• Class II: Mixed smooth sediment and rock 

• Class III: Rock and boulder, rugose 

• Class IV: Anthropogenic material (rugged) 

• Class V: Anthropogenic material (smooth, hard) 

• Class VI: Medium- to coarse-grained sediment (in scour depressions) 

The seafloor-character map of the Offshore of Santa Barbara map area (sheet 5) was produced 

using video-supervised maximum-likelihood classification of the bathymetry and intensity of return 

from sonar systems, following the method described by Cochrane (2008). The two variants used in this 

classification were backscatter intensity and derivative rugosity, which is a standard calculation 

performed with the National Oceanic and Atmospheric Administration (NOAA) benthic-terrain modeler 

(available at http://www.csc.noaa.gov/digitalcoast/tools/btm/index.html; last accessed March 4, 2013), 

using a 3-pixel by 3-pixel array of bathymetry.

Classes I, II, and III values were delineated using multivariate analysis. Classes IV and V 

(rugged and smooth anthropogenic material, respectively; both related to oil platforms and pipes) values 

were determined on the basis of their visual characteristics and the known location of man-made 

features. Class VI values (medium- to coarse-grained sediment, in scour depressions) were determined 

on the basis of their visual characteristics using both shaded-relief bathymetry and backscatter (slight 

depression in the seafloor, very high backscatter return). The resulting map (gridded at 2 m) was cleaned 

by hand to remove data-collection artifacts (for example, the trackline nadir). 
13

On the seafloor-character map (sheet 5), the six substrate classes have been colored to indicate 

the California MLPA depth zones and the Coastal and Marine Ecological Classification Standard 

(CMECS) slope zones (Madden and others, 2008) in which they belong. The California MLPA depth 

zones are Depth Zone 1 (intertidal), Depth Zone 2 (intertidal to 30 m), Depth Zone 3 (30 to 100 m), 

Depth Zone 4 (100 to 200 m), and Depth Zone 5 (greater than 200 m); in the Offshore of Santa Barbara 

map area, only Depth Zones 2 and 3 are present. The slope classes that represent the CMECS slope 

zones are Slope Class 1 = flat (0° to 5°), Slope Class 2 = sloping (5° to 30°), Slope Class 3 = steeply 

sloping (30° to 60°), Slope Class 4 = vertical (60° to 90°), and Slope Class 5 = overhang (greater than 

90°); in the Offshore of Santa Barbara map area, only Slope Class 1 is present. The final classified 

seafloor-character raster map image is draped over the shaded-relief bathymetry for the area (sheets 1 

and 2) to produce the image shown on the seafloor-character map on sheet 5.

The seafloor-character classification is also summarized on sheet 5 in table 1. Fine- to mediumgrained smooth sediment (sand and mud) makes up 98.0 percent (110.0 km2

) of the map area: 21.7 

percent (24.3 km2) is in Depth Zone 2, and 76.3 percent (85.7 km2) is in Depth Zone 3. Mixed smooth 

sediment (sand and gravel) and rock (that is, sediment typically forming a veneer over bedrock, or rock 

outcrops having little to no relief) make up 1.7 percent (1.9 km2) of the area mapped: 0.9 percent (1.0 

km2

) is in Depth Zone 2, and 0.8 percent (0.9 km2) is in Depth Zone 3. Rock and boulder, rugose (rock 

outcrops and boulder fields having high surficial complexity) makes up 0.2 percent (0.2 km2) of the map 

area: 0.1 percent (0.1 km2

) is in Depth Zone 2, and 0.1 percent (0.1 km2) is in Depth Zone 3. Rugged 

anthropogenic material (for example, a pipe) makes up 0.1 percent (0.1 km2) of the map area: less than 

0.1 percent (<0.1 km2) is in Depth Zone 2, and less than 0.1 percent (<0.1 km2) is in Depth Zone 3. 

Smooth, hard anthropogenic material (for example, debris surrounding the pipe) makes up less than 0.1 

percent (<0.1 km2) of the area mapped: less than 0.1 percent (<0.1 km2) is in Depth Zone 2, and less 

than 0.1 percent (<0.1 km2) is in Depth Zone 3. Medium- to coarse-grained sediment (in scour 

depressions consisting of material that is coarser than surrounding seafloor), present only in Depth Zone 

2, makes up less than 0.1 percent (<0.1 km2) of the map area.

A small number of video observations were used to supervise the numerical classification of the 

seafloor. All video observations (see sheet 6) are used for accuracy assessment of the seafloor-character 

map after classification. To compare observations to classified pixels, each observation point is assigned 

a class (I, II, or III), according to the visually derived, major or minor geologic component (for example, 

sand or rock) and the abiotic complexity (vertical variability) of the substrate recorded during groundtruth surveys (table 4–1; see also, chapter 5 of this pamphlet). Other classes were assigned on the basis 

of either the observation of anthropogenic features (for example, Classes IV and V) or the observation of 

one or more of a group of features (for example, Class VI) that includes larger scale bedforms (for 

example, sand waves), as well as the sediment-filled scour depressions that resemble “rippled scour 

depressions” of Cacchione and others (1984) and Phillips (2007) and also the “sorted bedforms” of 

Murray and Thieler (2004), Goff and others (2005), and Trembanis and Hume (2011). 

Next, circular buffer areas were created around individual observation points using a 10-m radius 

to account for layback and positional inaccuracies inherent to the towed-camera system. The radius 

length is an average of the distances between the positions of sharp interfaces seen on both the video 

(the position of the ship at the time of observation) and sonar data, plus the distance covered during a 

10-second observation period at an average speed of 1 nautical mile/hour. Each buffer, which covers 

more than 300 m2

, contains approximately 77 pixels. The classified (I, II, III) buffer is used as a mask to 

extract pixels from the seafloor-character map. These pixels are then compared to the class of the buffer. 

For example, if the shipboard-video observation is Class II (mixed smooth sediment and rock), but 12 of 

the 77 pixels within the buffer area are characterized as Class I (fine- to medium-grained smooth 

sediment), and 15 (of the 77) are characterized as Class III (rock and boulder, rugose), then the 

comparison would be “Class I, 12; Class II, 50; Class III, 15” (fig. 4–1). If the video observation of 
14

substrate is Class II, then the classification is accurate because the majority of seafloor pixels in the 

buffer are Class II. The accuracy values in table 4–2 represent the final of several classification 

iterations aimed at achieving the best accuracy, given the variable quality of sonar data (see discussion 

in Cochrane, 2008) and the limited ground-truth information available when compared to the continuous 

coverage provided by swath sonar. Presence/absence values in table 4–2 reflect the percentages of 

observations where the sediment classification of at least one pixel within the buffer zone agreed with 

the observed sediment type at a certain location. 

The seafloor in the Offshore of Santa Barbara map area is mainly flat with small, local 

sedimentary-bedrock exposures (Class III). The seabed is predominantly covered by Class I sediment 

composed of soft, unconsolidated sand and mud. Class II sediment varies from gravel to sedimentcovered tar flows. Differentially eroded sedimentary-bedrock outcrops (Class III) are present mainly in 

the east-southeastern part of the map area, including outcrops near and just outside the 3-nautical-mile 

limit of California’s State Waters; exposed rock is covered intermittently by varying thicknesses of fine- 

(Class I) to coarse-grained (Class II) sediment (coarse sand and gravel). Several anthropogenic features 

associated with oil production are present, including platforms and pipelines, jetties and groins, and shell 

mounds beneath platforms. 

The classification accuracy of Class I (96 percent accurate; table 4–2) is determined by 

comparing the shipboard video observations and the classified map. The weaker agreements in Classes

II and III (27 percent accurate and 12 percent accurate, respectively) likely are due to the distribution of 

small, localized rock outcrops and also to the relatively narrow, intermittent nature of transition zones 

from sediment to rock, as well as the size of the buffer. The bedrock outcrops in this area are composed 

of sedimentary rocks exhibiting differential erosion (Cochrane and Lafferty, 2002). Erosion of softer 

layers produces Class I and II sediments, resulting in patchy rugose rock and boulder habitat on the 

seafloor. A single buffered observation locale of 78 pixels, therefore, is likely to be interspersed with 

other classes of pixels, as well as with Class III. Percentages for presence/absence within a buffer also 

were calculated as a better measure of the accuracy of the classification for patchy rock habitat. The 

presence/absence accuracy was found to be significant for Classes I and II (98 percent for Class I, and 

86 percent for Class II). Only a limited number of observations were made over Class III rugose rock 

and boulder substrate, likely because the rock outcrops in the map area are characterized by linear, 

narrow ridges; therefore, the presence/absence accuracy is somewhat lower (46 percent) for Class III. 

Figure 4–1. Detailed view of ground-truth data, showing accuracy-assessment methodology. A, Dots illustrate 

ground-truth observation points, each of which represents 10-second window of substrate observation plotted 

over seafloor-character grid; circle around dot illustrates area of buffer depicted in B. B, Pixels of seafloorcharacter data within 10-m-radius buffer centered on one individual ground-truth video observation.
15

No video observations were retrieved over the pipe or oil-platform structures (Class IV substrate, rugged 

anthropogenic feature, and Class V substrate, smooth, hard anthropogenic feature, respectively) in the 

map area, nor were they retrieved over Class VI substrate (medium- to coarse-grained sediment);

therefore, no accuracy assessments were performed for these classes.

Table 4–1. Conversion table showing how video observations of primary substrate (more than 50 percent seafloor 

coverage), secondary substrate (more than 20 percent seafloor coverage), and abiotic seafloor complexity (in 

first three columns) are grouped into seafloor-character-map Classes I, II, and III for use in supervised 

classification and accuracy assessment in Offshore of Santa Barbara map area. 

[In areas of low visibility where primary and secondary substrate could not be identified with confidence, recorded 

observations of substrate (in fourth column) were used to assess accuracy]

Primary-substrate component Secondary-substrate component Abiotic seafloor complexity Low-visibility observations

Class I

mud cobbles low

mud sand low

sand mud low

sand sand low

sediment

 ripples

Class II

cobbles sand moderate

gravel sand low

mud boulders low

mud boulders moderate

rock mud low

rock rock low

sand boulders moderate

sand cobbles

sand cobbles low

sand gravel low

sand rock low

sand rock moderate

Class III 

boulders boulders moderate

boulders mud moderate

rock gravel moderate

rock mud moderate

rock rock high

rock rock moderate

rock sand moderate
16

Table 4–2. Accuracy-assessment statistics for seafloor-character-map classifications in Offshore of Santa Barbara 

map area. 

[Accuracy assessments are based on video observations (N/A, no accuracy assessment was conducted)]

Class Number of observations % majority % presence/absence

I—Fine- to medium-grained smooth sediment 398 96.2 98.2

II—Mixed smooth sediment and rock 29 27.3 86.2

III—Rock and boulder, rugose 24 12.3 45.8

IV—Rugged anthropogenic feature 0 N/A N/A

V—Smooth, hard anthropogenic feature 0 N/A N/A

VI—Medium- to coarse-grained sediment (in scour 

depressions) 0 N/A N/A
17

Chapter 5. Ground-Truth Studies for the Offshore of Santa Barbara Map 

Area (Sheet 6)

By Nadine E. Golden and Guy R. Cochrane

To validate the interpretations of sonar data in order to turn it into geologically and biologically 

useful information, the U.S. Geological Survey (USGS) towed a camera sled (fig. 5–1) over specific 

locations throughout the Offshore of Santa Barbara map area to collect video and photographic data that 

would “ground truth” the seafloor. This ground-truth surveying occurred on three separate cruises in 

2005, 2006, and 2008. The camera sled was towed 1 to 2 m over the seafloor, at speeds of between 1 

and 2 nautical miles/hour. Ground-truth surveys in this map area include approximately 16 trackline 

kilometers of video and 335 still photographs, in addition to 829 recorded seafloor observations of 

abiotic and biotic attributes. A visual estimate of slope also was recorded.

During the 2005 and 2006 cruises, a smaller USGS camera sled was used that housed two 

standard-definition (640×480 pixel resolution) video cameras: one was forward looking, and the other 

was downward looking. During the 2008 cruise, a larger camera sled was used that housed the two 

standard-definition video cameras (one forward looking and one downward looking), as well as a highdefinition (1,080×1,920 pixel resolution) video camera and an 8-megapixel digital still camera. During 

this cruise, in addition to recording the seafloor characteristics, a digital still photograph was captured 

once every 30 seconds. 

The camera-sled tracklines (shown by colored dots on the map on sheet 6) are sited in order to 

visually inspect areas representative of the full range of bottom hardness and rugosity in the map area. 

The video is fed in real time to the research vessel, where USGS and National Oceanic and Atmospheric 

Administration (NOAA) scientists record both the geologic and biologic character of the seafloor. While 

Figure 5–1. Photograph of camera sled used in USGS 2008 ground-truth survey.
18

the camera is deployed, several different observations are recorded for a 10-second period once every 

minute, using the protocol of Anderson and others (2007). Observations of primary substrate, secondary 

substrate, slope, abiotic complexity, biotic complexity, and biotic cover are mandatory. Observations of 

key geologic features and the presence of key species also are made. 

Primary and secondary substrate, by definition, constitute greater than 50 and 20 percent of the 

seafloor, respectively, during an observation. The grain-size values that differentiate the substrate 

classes are based on the Wentworth (1922) scale, and the sand, cobble, and boulder sizes are classified 

as in Wentworth (1922). However, the difficulty in distinguishing the finest divisions in the Wentworth 

(1922) scale during video observations made it necessary to aggregate some grain-size classes, as was 

done in the Anderson and others (2007) methodology: the granule and pebble sizes have been grouped 

together into a class called “gravel,” and the clay and silt sizes have been grouped together into a class 

called “mud.” In addition, hard bottom and clasts larger than boulder size are classified as “rock.” 

Benthic-habitat complexity, which is divided into abiotic (geologic) and biotic (biologic) components, 

refers to the visual classification of local geologic features and biota that potentially can provide refuge 

for both juvenile and adult forms of various species (Tissot and others, 2006). 

Sheet 6 contains a smaller, simplified (depth-zone symbology has been removed) version of the 

seafloor-character map on sheet 5. On this simplified map, the camera-sled tracklines used to groundtruth-survey the sonar data are shown by aligned colored dots, each dot representing the location of a 

recorded observation. A combination of the abiotic attributes (primary- and secondary-substrate 

compositions), as well as vertical variability, were used to derive the different classes represented on the 

seafloor-character map (sheet 5); on the simplified map, the derived classes are represented by colored 

dots. Also on this map are locations of the detailed views of seafloor character, shown by boxes (Boxes 

A through E); for each view, the box shows the locations (indicated by colored stars) of representative 

seafloor photographs. For each photograph, an explanation of the observed seafloor characteristics 

recorded by USGS and NOAA scientists is given. Note that individual photographs often show more 

substrate types than are reported as the primary and secondary substrate. Organisms, when present, are 

labeled on the photographs. 

The ground-truth survey is designed to investigate areas that represent the full spectrum of highresolution multibeam bathymetry and backscatter-intensity variation. Figure 5–2 shows that, in the 

Offshore of Santa Barbara map area, the surface is covered predominantly by sediment with some 

differentially eroded bedrock outcroppings offshore of Santa Barbara. The more rugose rock outcrops 

are surrounded by areas of mixed rock and sediment or flat rock outcroppings. 
19

Figure 5–2. Graph showing distribution of primary and secondary substrate determined from video observations in 

Offshore of Santa Barbara map area.
20

Chapter 6. Potential Marine Benthic Habitat Map of the Offshore of 

Santa Barbara Map Area (Sheet 7)

By H. Gary Greene, Bryan E. Dieter, and Charles A. Endris

The map on sheet 7 shows “potential” marine benthic habitats in the Offshore of Santa Barbara 

map area, representing a substrate type, geomorphology, seafloor process, or any other attribute that may 

provide a habitat for a specific species or assemblage of organisms. This map, which is based largely on 

seafloor geology, also integrates information displayed on several other thematic maps of the Offshore 

of Santa Barbara map area. High-resolution sonar bathymetry data, converted to depth grids (seafloor 

DEMs; sheet 1), are essential to development of the potential marine benthic habitat map, as is shadedrelief imagery (sheet 2), which allows visualization of seafloor terrain and provides a foundation for 

interpretation of submarine landforms. 

Backscatter maps (sheet 3) also are essential for developing potential benthic habitat maps. High 

backscatter is further indication of “hard” bottom, consistent with interpretation as rock or coarse 

sediment. Low backscatter, indicative of a “soft” bottom, generally indicates a fine-sediment 

environment. Habitat interpretations are also informed by actual seafloor observations from ground-truth

surveying (sheet 6), by seafloor-character maps that are based on video-supervised maximum-likelihood 

classification (sheet 5), and by seafloor-geology maps (sheet 10). The habitat interpretations on sheet 7 

are further informed by the usSEABED bottom-sampling compilation of Reid and others (2006). 

Broad, generally smooth areas of seafloor that lack sharp and angular edge characteristics are

mapped as “sediment;” these areas may be further defined by various sedimentary features (for example, 

erosional scours and depressions) and (or) depositional features (for example, dunes, mounds, or sand 

waves). In contrast, many areas of seafloor bedrock exposures are identified by their common sharp 

edges and high relative relief; these may be contiguous outcrops, isolated parts of outcrop protruding 

through sediment cover (pinnacles or knobs), or isolated boulders. In many locations, areas within or 

around a rocky feature appear to be covered by a thin veneer of sediment; these areas are identified on 

the habitat map as “mixed” induration (that is, containing both rock and sediment). The combination of 

remotely observed data (for example, high-resolution bathymetry and backscatter, seismic-reflection 

profiles) and directly observed data (for example, camera transects, sediment samples) translates to 

higher confidence in the ability to interpret broad areas of the seafloor. 

To avoid any possible misunderstanding of the term “habitat,” the term “potential habitat” (as 

defined by Greene and others, 2005) is used herein to describe a set of distinct seafloor conditions that in 

the future may qualify as an “actual habitat.” Once habitat associations of a species are determined, they 

can be used to create maps that depict actual habitats, which then need to be confirmed by in situ

observations, video, and (or) photographic documentation. 

Classifying Potential Marine Benthic Habitats

Potential marine benthic habitats in the Offshore of Santa Barbara map area are mapped using 

the Benthic Marine Potential Habitat Classification Scheme, a mapping-attribute code developed by 

Greene and others (1999, 2007). This code, which has been used previously in other offshore California 

areas (see, for example, Greene and others, 2005, 2007), was developed to easily create categories of 

marine benthic habitats that can then be queried within a GIS or a database. The code contains several 

categories that can be subdivided relative to the spatial scale of the data. The following categories can be 

applied directly to habitat interpretations determined from remote-sensing imagery collected at a scale of 

tens of kilometers to one meter: Megahabitat, Seafloor Induration, Meso/Macrohabitat, Modifier, 

Seafloor Slope, Seafloor Complexity, and Geologic Unit. Additional categories of Macro/Microhabitat, 
21

Seafloor Slope, Seafloor Complexity, and Geologic Attribute can be applied to habitat interpretations 

determined from seafloor samples, video, still photographs, or direct observations at a scale of 10 meters 

to a few centimeters. These two scale-dependent groups of categories can be used together, to define a 

habitat across spatial scales, or separately, to compare large- and small-scale habitat types. 

The six categories and their attribute codes that are used on the Offshore of Santa Barbara map 

are explained in detail below (note, however, that not all categories may be used in a particular map 

area, given the study objectives, data availability, or data quality); attribute codes in each category are 

depicted on the map by the letters and, in some cases, numbers that make up the map-unit symbols: 

Megahabitat—Based on depth and general physiographic boundaries; used to distinguish 

features on a scale of tens of kilometers to kilometers. Depicted on map by capital letter, listed first in 

map-unit symbol; generalized depth ranges are given below. 

F = Flank; continental slope, basin and (or) island flanks (200 to 3,000 m) 

S = Shelf; continental and island shelves (0 to 200 m) 

Seafloor Induration—Refers to substrate hardness. Depicted on map by lower-case letter, listed

second in map-unit symbol; may be further subdivided into distinct sediment types, depicted by lowercase letter(s) in parentheses, listed immediately after substrate hardness; multiple attributes listed in 

general order of relative abundance, separated by slash; queried where inferred.

h = Hard bottom (for example, rock outcrop or sediment pavement) 

m = Mixed hard and soft bottom (for example, local sediment cover of bedrock) 

s = Soft bottom; sediment cover

(g) = Gravel

(s) = Sand

(m) = Mud, silt, and (or) clay

Meso/Macrohabitat—Related to scale of habitat; consists of seafloor features one kilometer to 

one meter in size. Depicted on map by lower-case letter and, in some cases, additional lower-case letter 

in parentheses, listed third in map-unit symbol; multiple attributes separated by slash.

b = Beach, relic (submerged) or shoreline 

(b)/p = Pinnacle indistinguishable from boulder 

c = Canyon

c(b) = Bar within thalweg

c(c) = Curve or meander within thalweg 

c(f) = Fall or chute within thalweg

c(h) = Canyon head

c(m) = Canyon mouth 

c(t) = Thalweg

c(w) = Canyon wall

d = Deformed, tilted and (or) folded bedrock; overhang 

e = Exposure; bedrock 

f = Flat; floor

g = Gully; channel

h = Hole; depression 

l = Landslide; mass movement; rubble 

m = Mound; linear ridge 

o = Overbank deposit; levee 

p = Pinnacle; cone 

r = Rill (linear depression on surface formed by subterranean winnowing of sediment) 

s = Scarp, cliff, fault, or slump scar 

t = Terrace 
22

v = Vegetated (grass- or algae-covered) sediment or rock 

w = Dynamic bedform

w(w) = Sediment wave (amplitude, 10 cm to a meter; wave length, tens of meters) 

w(d) = Sediment dune (amplitude, tens of meters; wave length, hundreds of meters) 

y = Delta; fan

Modifier—Describes texture, bedforms, biology, or lithology of seafloor. Depicted on map by 

lower-case letter, in some cases followed by additional lower-case letter(s) either after hyphen or in 

parentheses (or both), following an underscore; multiple attributes separated by slash.

_a = Anthropogenic (artificial reef, breakwall, shipwreck, disturbance) 

_a-c = Cable

_a-dd = Dredge disturbance

_a-dg = Dredge groove or channel

_a-dp = Dredge potholes 

_a-dm = Dredge mound (disposal) 

_a-dp = Dredge pothole 

_a-f = Ferry (or other vessel) propeller-wash scour or scar 

_a-g = Groin, jetty, rip-rap

_a-m = Marina, harbor 

_a-p = Pipeline

_a-s = Support; dock piling, dolphin 

_a-td = Trawl disturbance 

_a-w = Wreck, ship, barge, or plane 

_b = Bimodal (conglomeratic, mixed [gravel, cobbles, and pebbles]) 

_c = Consolidated sediment (claystone, mudstone, siltstone, sandstone, breccia, or 

conglomerate) 

_d = Differentially eroded

_e = Effusive pit; pockmark 

_f = Fracture, joint; faulted

_g = Granite

_h = Hummocky, irregular relief

_i = Interface; lithologic contact

_k = Kelp

_l = Limestone or carbonate rock or structure 

_l(a) = Alive reef

_l(d) = Dead reef

_l(l) = Linear reef

_l(p) = Patch reef

_l(pr-a) = Aggregated patch reef

_l(pr-i) = Individual patch reef 

_l(r) = Reef rubble 

_l(s-g) = Spur and groove 

_m = Massive sedimentary bedrock

_o = Outwash

_p = Pavement

_r = Ripple (amplitude, greater than 10 cm) 

_s = Scour (current or ice; direction noted) 

_u = Unconsolidated sediment 

_v = Volcanic rock
23

_w = Wall

 Seafloor Slope—Denotes slope, typically calculated from XYZ high-resolution bathymetry 

data. Depicted on map by number, listed after modifier. 

1 = Flat (0o–5o)

2 = Sloping (5o–30o) 

3 = Steeply sloping (30o–45o) 

4 = Vertical or near vertical (45o–90o) 

5 = Overhanging (more than 90o) 

6 = Unknown 

Geologic Attribute—Describes additional geologic features seen in video, still photographs, or 

other types of direct observations. Depicted on map by lower-case letter(s) in parentheses, preceded by 

an asterisk.

*(a) = Anthropogenic (for example, cable, pipeline, disturbance) 

*(a-d) = Dredge track, pit, or mound 

*(b) = Boulder 

*(d) = Deformed, faulted, or folded

*(e) = Exposure, bedrock (sedimentary, igneous, or metamorphic) 

*(e-r) = Rough bedrock surface 

*(f) = Fan or apron 

*(g) = Gravel

*(j) = Joint, crack, crevice, overhang (differentially eroded) 

*(l) = Limestone, carbonate deposit 

*(m) = Mud, silt, or clay 

*(q) = Coquina (shell hash) 

*(r) = Rubble 

*(s) = Sand

*(t) = Flat, terracelike seafloor, including sedimentary pavement

*(u) = Undulating surface, hummocky 

*(u-r) = Ripple 

*(u-s) = Scour 

*(u-w) = Sediment wave

*(y) = Barnacle or plate

Examples of Attribute Coding

To illustrate how these attribute codes can be used to describe remotely sensed data, the 

following examples are given: 

Ssc(h)_u2/4 = Canyon head that indents shelf and has smooth, soft, gently sloping, sedimentary 

walls, locally cropping out as steep (near vertical) scarps (10 to 100 m). 

Ssf_u1 = Flat to gently sloping shelf that has soft, unconsolidated sediment (10 to 150 m). 

Fhe_m/c = Continental slope that has hard sedimentary (sandstone) bedrock exposures locally 

and smooth to moderately irregular relief (less than 1 m to 3 m high); exposures often covered with 

sediment (200 to 2,500 m). 

Ssm_a/u*(q) = Soft, unconsolidated sediment and shell-hash mound, adjacent to oil platform 

(anthropogenic). 
24

Map Area Habitats 

Delineated in the Offshore of Santa Barbara map area are 26 potential marine benthic habitat 

types. These habitat types range from primarily soft, unconsolidated sediment (mud to sand and gravel) 

to hard bedrock exposures (flat carbonate substrate; asphalt (tar) mounds; differentially eroded, wellbedded sedimentary outcrops). Sedimentary-bedrock outcrops (some of which are partly covered with 

sediment to produce a hard-soft mixed habitat type), as well as pockmarks, rills, and possible hummocky 

tar flows, complete the variety of habitats identified in the map area. Significant anthropogenic features 

associated with oil production, such as platforms, pipelines, and shell mounds beneath platforms, as well 

as riprap and a shipwreck, all produce artificial habitats for rockfish (Sebastes spp.). Trawl marks are 

also present as anthropogenic features. 

The soft, unconsolidated sediment habitat, which includes pockmarks and inferred sedimentcovered tar flows, covers 97.41 km2

 of the map area, representing 86.6 percent of all the potential 

habitat types identified. Sediment-covered bedrock, which includes the hard-soft mixed habitat type, 

covers 11.84 km2 (10.5 percent). Hard bedrock exposures cover 3.08 km2 (2.7 percent), whereas 

anthropogenic features cover about 0.17 km2 (<0.15 percent). The mix of potential marine benthic 

habitat types provides the varied relief, in addition to the rugosity and substrate hardness, that contribute 

to the concentration of a diverse ecosystem within an otherwise homogeneous, soft, unconsolidated 

sediment habitat.

Of special interest in the Offshore of Santa Barbara map area is the role of fluid flowing up to the 

seafloor from petroleum reservoirs at depth, which is inferred to have caused the formation of locally 

exposed hard, carbonate-cemented sediment substrate, carbonate mounds, pockmarks, and tar or asphalt 

flows. Notably, an extensive (7.09 km2) area of carbonate hardground (Sme_c/l/u), locally covered with 

sediment, is exposed about 5 km offshore in the southwestern part of the map area, providing potential 

habitat for sessile organisms. In addition, one prominent lobe (Ssl_h/t/u?) in the map area may be a

sediment-covered tar flow. This possible tar flow could have its source in an upslope tar-drain 

depression now covered by sediment (Ss(s/m)h_r/u), 0.37 km2 in area, which is located on the 

northwest flank of a prominent, differentially eroded, east-west-trending bedrock platform (Shd_c/d). 
25

Chapter 7. Subsurface Geology and Structure of the Offshore of Santa 

Barbara Map Area and the Santa Barbara Channel Region (Sheets 8 and 

9)

By Samuel Y. Johnson, Eleyne L. Phillips, Andrew C. Ritchie, Florence L. Wong, Ray W. Sliter, Amy E. Draut, 

Patrick E. Hart, and James E. Conrad 

The seismic-reflection profiles presented on sheet 8 provide a third dimension, depth, to 

complement the surficial seafloor-mapping data already presented (sheets 1 through 7) for the Offshore 

of Santa Barbara map area. These data, which are collected at several resolutions, extend to varying 

depths in the subsurface, depending on the purpose and mode of data acquisition. The seismic-reflection 

profiles (sheet 8) provide information on sediment character, distribution, and thickness, as well as 

potential geologic hazards, including active faults, areas prone to strong ground motion, and 

tsunamigenic slope failures. The information on faults provides essential input to national and state 

earthquake-hazard maps and assessments (for example, Petersen and others, 2008). 

The maps on sheet 9 show the following interpretations, which are based on the seismicreflection profiles on sheet 8: the thickness of the uppermost sediment unit; the depth to base of this 

uppermost unit; and both the local and regional distribution of faults and earthquake epicenters (data 

from Heck, 1998; Minor and others, 2009; Jennings and Bryant, 2010; Southern California Earthquake 

Data Center, 2010). 

Data Acquisition

Most profiles displayed on sheet 8 (figs. 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12) were collected in 2007 on 

U.S. Geological Survey (USGS) cruise Z–3–07–SC (Sliter and others, 2008). Single-channel seismicreflection data were acquired using two different sources, the EdgeTech 512 chirp (figs. 3, 4, 5, 7, 9, 11) 

and the SIG 2Mille minisparker (figs. 1, 2, 6, 8, 12). The EdgeTech 512 chirp subbottom-profiling 

system consists of a source transducer and an array of receiving hydrophones housed in a 500-lb fish 

towed at a depth of several meters below the sea surface. The swept-frequency chirp source signal was 

500 to 4,500 Hz and 50 ms in length, and it was recorded by hydrophones located on the bottom of the 

fish. The SIG minisparker system used a 500-J high-voltage electrical discharge fired 1 to 4 times per 

second, which, at normal survey speed of 4 to 4.5 nautical miles/hour, gives a data trace every 0.5 to 2.0 

m of lateral distance covered. The data were digitally recorded in standard SEG-Y 32-bit floating-point 

format, using Triton Subbottom Logger (SBL) software that merges seismic-reflection data with 

differential GPS-navigation data. After the survey, a short-window (20 ms) automatic gain control 

algorithm was applied to both the chirp and minisparker data, and a 160- to 1,200-Hz bandpass filter 

was applied to the minisparker data. These high-resolution data can resolve geologic features that are a 

few meters thick (small-scale features) to subbottom depths of as much as a few hundred meters. 

Figure 10 on sheet 8 shows a deep-penetration, migrated, multichannel seismic-reflection profile 

collected in 1984 by WesternGeco on cruise W–37–84–SC. This profile and other similar data were 

collected in many areas offshore of California in the 1970s and 1980s when these areas were considered 

a frontier for oil and gas exploration. Much of these data have been publicly released and are now 

archived at the U.S. Geological Survey National Archive of Marine Seismic Surveys (U.S. Geological 

Survey, 2009). These data were acquired using a large-volume air-gun source that has a frequency range 

of 3 to 40 Hz and recorded with a multichannel hydrophone streamer about 2 km long. Shot spacing was 

about 30 m. These data can resolve geologic features that are 20 to 30 m thick, down to subbottom 

depths of about 4 km. 
26

Seismic-Reflection Imaging of the Continental Shelf 

Sheet 8 shows seismic-reflection profiles in the Offshore of Santa Barbara map area, which is 

characterized by a relatively flat (less than 1°), moderately deep (75 m or less), wave-cut shelf with local 

relief associated with bedrock uplifts (see sheets 1, 2, 10). This shelf is underlain by variably thick (0 to 

about 14 m) upper Pleistocene and Holocene marine, deltaic, and alluvial sediments (Draut and others, 

2009; Sommerfield and others, 2009) deposited in the last about 21,000 years during the about 125-m 

sea-level rise that followed glaciation and the last major sea-level lowstand. Sea-level rise after the Last 

Glacial Maximum (LGM) was rapid (as much as 15 m per thousand years) until about 7,000 years ago, 

at which time it slowed considerably (to about 1 m per thousand years) (Fairbanks, 1989; Fleming and 

others, 1998; Lambeck and Chappell, 2001; Peltier and Fairbanks, 2006; Stanford and others, 2011).

The sediments deposited during this latest Pleistocene and Holocene sea-level rise are shaded 

blue in the high-resolution seismic-reflection profiles on sheet 8 (figs. 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12), and 

their thickness is shown on sheet 9. In the minisparker profiles (figs. 1, 2, 6, 8, 12 on sheet 8), these 

strata are typically characterized by parallel, low- to moderate-amplitude, low- to high-frequency, 

continuous to moderately continuous reflections (terminology from Mitchum and others, 1977). In the 

chirp seismic-reflection profiles (figs. 3, 4, 5, 7, 9, 11 on sheet 8), this stratigraphic interval commonly is 

“acoustically transparent” (that is, lacking internal reflections). The presence and continuity of seismic 

reflections in this upper unit on many profiles is also obscured by interstitial gas within the sediment. 

This effect has been referred to as “gas blanking,” “acoustic turbidity,” or “acoustic masking” (Hovland 

and Judd, 1988; Fader, 1997). The gas scatters or attenuates the acoustic energy, preventing penetration. 

Not surprisingly, this effect is especially prevalent near the Summerland oil field (see, for example, 

Kunitomi and others, 1998) and near the crests of anticlines. 

Because the shelf was partly emergent during the postglacial period of rising sea level, the lower 

part of the post-LGM unit may, in places, consist of thin marginal marine deposits (especially where the 

unit is thickest). These strata were reworked and then covered by nearshore and shelf sediments as sea 

level rose and the shoreline migrated both landward and upward. The upper part of this unit must consist 

of shelf deposits that are similar to the sediments found on the shelf today (see sheet 6). 

On most profiles on sheet 8, the base of the post-LGM depositional unit is a flat to concave 

angular unconformity, characterized by a high-amplitude reflection. Post-LGM sediment onlapping of 

local uplifts (for example, figs. 3, 9) is common. Sediment-covered wave-cut platforms and risers (see, 

for example, Kern, 1977) are imaged at the base of the unit on some profiles, most commonly at depths 

of about 45 m offshore of Santa Barbara (see, for example, figs. 8, 9) and of about 34 m offshore of 

Montecito (see, for example, figs. 4, 7). Given uplift rates from nearby coastal terraces (Trecker and 

others, 1998; Keller and Gurrola, 2000, their fig. 6), these depths are consistent with formation during 

late oxygen-isotopic stage 3, about 40 to 25 ka. Alternatively, they could also have formed during the 

post-LGM transgression. Post-LGM sea-level rise and landward shoreline migration were not steady 

but, rather, were characterized by periods of relative stability and rapid submergence (see, for example, 

Peltier, 2005; Stanford and others, 2011). For example, sea level rose as much as 15 m per thousand 

years during meltwater pulse 1b, about 10,000 years ago (Stanford and others, 2011). Such pulses 

rapidly submerge wave-cut platforms, shorelines, and shoreline angles (Kern, 1977), thereby increasing 

the potential for their preservation. 

Geologic Structure and Recent Deformation

Seismic-reflection profiles in the Offshore of Santa Barbara map area (sheet 8) show significant 

folding and faulting. The east-west-striking, south-dipping Rincon Creek Fault Zone (figs. 2, 7, 9, 12 on 

sheet 8), which extends into the map area from the east, forms the north edge of a northwest-trending 

uplift of complexly deformed Miocene Monterey Formation, due south of Santa Barbara (see sheet 10); 
27

similarly, it forms the north edge of a bedrock uplift in the Offshore of Carpinteria map area to the east 

(see Johnson and others, 2013). Within the Offshore of Santa Barbara map area, the fault zone is “blind” 

because it does not appear to rupture to the surface or to clearly offset the upper Pleistocene and 

Holocene stratigraphic unit. Instead, it is characterized by a zone of deformation that includes an 

upward-narrowing asymmetric syncline that has a gently south-dipping north limb and a more steeply 

north-dipping south limb (figs. 7, 9, 12 on sheet 8). The steep, north-dipping south limb forms the 

margin of a sedimentary basin inferred to be filled by the Pleistocene Santa Barbara and Casitas 

Formations (Redin, 2005). An interpretation on sheet 8 (fig. 2) shows about 2.0 to 2.5 m of foldingrelated uplift in the latest Pleistocene and Holocene stratigraphic unit, but as much as 12 m of uplift is 

plausible. Onland to the west, the trace of the Rincon Creek Fault Zone probably bends more 

northwestward and merges with the Lavigia Fault, which similarly forms a local boundary between the 

Monterey Formation and the Santa Barbara Formation (Minor and others, 2009). 

The steeply dipping north strand of the Red Mountain Fault Zone also extends westward from 

the Offshore of Carpinteria map area (Johnson and others, 2013) into the Offshore of Santa Barbara map 

area, where it is coincident with the axis of a prominent tight syncline (figs. 7, 11 on sheet 8; see also, 

sheet 10). Although the syncline can be mapped across the entire map area, faulting in the shallow 

subsurface appears to die out about 7 km east of the west edge of the map. The east-west-striking, northdipping south strand of the Red Mountain Fault Zone extends south of the map area, and it appears to 

die out in the shallow subsurface south of Montecito (south of the map area). Farther south, the eastwest-striking, north-dipping Pitas Point–North Channel Fault (fig. 10 on sheet 8) cuts across the slope 

about 2 to 5 km south of the map area. 

Both the Red Mountain and the Rincon Creek Fault Zones in the map area are inferred to have 

complex structure at depth (characterized by numerous splays) on the basis of the irregular character of 

their near-surface folding; closely spaced seismic-reflection profiles document variable fold presence, 

geometry, length, amplitude, continuity, and wavelength (figs. 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12 on sheet 8). 

The cross section of Redin (2005) suggests that the south-dipping Rincon Creek Fault merges at depth 

with splays of the north-dipping Red Mountain Fault to form a zone characterized by both north-south 

contraction and left-lateral displacement.

The regional pattern of faults and earthquakes occurring between 1932 and 2010 that have 

inferred or measured magnitudes greater than 2.0 are shown on Map C on sheet 9. Although locations 

have been provided by the CalTech network since 1932, significantly greater precision began in 1969 

with installation of a USGS seismographic network (see, for example, Lee and Vedder, 1973; Sylvester, 

2001; Southern California Earthquake Data Center, 2010). Epicentral data indicate that seismicity in the 

eastern and central Santa Barbara Channel is characterized by earthquake swarms, relatively frequent 

minor earthquakes, and infrequent major earthquakes. 

Three significant earthquakes affected the Santa Barbara Channel area in 1812, 1857, and 1925, 

prior to the time covered by the Southern California Earthquake Data Center (2010) catalog; however, 

locations in the northern Santa Barbara Channel have been reported (Sylvester and others, 1970) for 

both the 1925 event (M6.3) and the largest earthquake (~M5.5, 7/1/1941), which is shown on Map C 

(sheet 9). In addition, Sylvester and others (1970) documented a swarm of 62 earthquakes (M2.5–M5.2) 

that occurred between 6/26/1968 and 8/3/1968, which also were located 10 to 15 km south (offshore) of 

Santa Barbara. The largest event in the Offshore of Santa Barbara map area (~M4.1) occurred on 

3/10/1986 near the west edge of the map. 

Thickness and Depth to Base of Uppermost Pleistocene and Holocene Deposits

Maps on sheet 9 show the thickness and the depth to base of uppermost Pleistocene and 

Holocene (post-LGM) deposits both for the Offshore of Santa Barbara map area (Maps A, B) and, to 
28

establish regional context, for a larger area (about 115 km of coast) that extends from the vicinity of 

Hueneme Canyon northwest to the Refugio Beach area (Maps D, E). To make these maps, water bottom 

and depth to base of the LGM horizons were mapped from seismic-reflection profiles using Seisworks 

software. The difference between the two horizons was exported from Seisworks for every shot point as 

XY coordinates (UTM zone 11) and two-way travel time (TWT). The thickness of the post-LGM unit 

(Maps B, E) was determined by applying a sound velocity of 1,600 m/sec to the TWT, resulting in 

thicknesses as great as 65 m. The thickness points were interpolated to a preliminary continuous surface, 

overlaid with zero-thickness bedrock outcrops (see sheet 10), and contoured (Wong and others, 2012). 

Data within Hueneme Canyon were excluded from the contouring because the seismic-reflection data 

are too sparse to adequately image the highly variable changes in sediment thickness that characterize 

the canyon (Maps D, E). 

Several factors required manual editing of the preliminary sediment-thickness maps to make the 

final product. The Red Mountain Fault Zone, Pitas Point Fault, and Oak Ridge Fault disrupt the 

sediment sequence in the region (Maps D, E on sheet 9). The data points also are dense along tracklines 

(about 1 m apart) and sparse between tracklines (1–2 km apart), resulting in contouring artifacts. To 

incorporate the effect of the faults, to remove irregularities from interpolation, and to reflect other 

geologic information and complexity, the resulting interpolated contours were modified. Contour 

modifications and regridding were repeated several times to produce the final regional sedimentthickness map (Wong and others, 2012). 

The depth-to-base data available from Seisworks were similarly processed and contoured; 

however, this preliminary data set was set aside in favor of a surface determined by subtracting the 

modified thickness data from multibeam bathymetry collected separately (see sheet 1) and using 1,500 

m/sec for TWT in the water column. The depth of this surface in the Hueneme Canyon to Refugio 

Beach area ranges from 12 to 190 m (Map D on sheet 9; see also, Wong and others, 2012). 

Five different “domains” of sediment thickness, which are bounded either by faults or by 

Hueneme Canyon, are recognized on the regional maps (Maps D, E on sheet 9): (1) north of the south 

strand of the Red Mountain Fault Zone; (2) between the south strand of the Red Mountain Fault Zone 

and the Pitas Point Fault; (3) between the Pitas Point and Oak Ridge Faults; (4) between the Oak Ridge 

Fault and Hueneme Canyon; and (5) south of Hueneme Canyon. Table 7–1 shows the area of these five 

domains, along with estimates of their mean sediment thickness and total sediment volume. These data 

highlight the contrast among three general zones of sediment thickness: (1) the uplifted, sediment-poor 

Santa Barbara shelf (domain 1; mean sediment thickness of 3.5 m); (2) a transitional zone (domain 2; 

mean sediment thickness of 18.0 m); and (3) the subsiding, sediment-rich delta and shelf offshore of the 

Ventura and Santa Clara Rivers and Calleguas Creek (domains 3, 4, and 5; mean sediment thicknesses 

of 39.2, 38.9, and 28.3 m, respectively). 

In the Offshore of Santa Barbara map area, thickness data (Map B on sheet 9) reveal that the 

post-LGM section has a mean thickness of just 3.4 m. Sediment is either notably lacking or it forms only 

a thin veneer over bedrock outcrops on the outer shelf. These outer shelf outcrops are a continuation of 

the east-west-trending uplifts that are present between the north and south strands of the Red Mountain 

Fault (Johnson and others, 2013). The thickness map also reveals a shallow trough north of the Red 

Mountain Fault Zone and south of the uplift associated with the Rincon Creek Fault Zone. This trough 

includes a “bedrock saddle” due south of Santa Barbara, east of which sediment thickens rapidly to more 

than 10 m. West of the saddle, sediment typically is 1 to 5 m thick but increases to more than 10 m in 

the nearshore along the west edge of the map area. Figure 3 on sheet 8 shows that this nearshore 

sediment “thick” has positive seafloor relief and delta-front morphology, including a relatively flat 

(about 0.6°) upper surface and a steeper (about 2.4°) seaward-dipping front. This feature is aligned with, 

and slightly west of, a network of streams (for example, Atascadero Creek; fig. 1–2) that drain into 
29

Goleta Slough (about 2 km west of the map area), and these coastal watersheds are the inferred source of 

the sediments that make up this small “delta-mouth bar.” 

Table 7–1. Area, sediment-thickness, and sediment-volume data for California’s State Waters in Santa Barbara 

Channel region, between Refugio Beach and Hueneme Canyon areas (domains 1– 5), as well as in Offshore of 

Santa Barbara map area. 

[Data from within Hueneme Canyon were not included in this analysis]

Regional sediment-thickness domains in Santa Barbara Channel region

Area (km2) Mean sediment 

thickness (m)

Sediment volume 

(106 m3) 

(1) Refugio Beach to south strand of Red 

Mountain Fault Zone 357.8 3.5 1,266

(2) South strand of Red Mountain Fault Zone to 

Pitas Point Fault 67.1 18.0 1,205

(3) Pitas Point Fault to Oak Ridge Fault 68.6 39.2 2,688

(4) Oak Ridge Fault to Hueneme Canyon 75.4 38.9 2,933

(5) South of Hueneme Canyon 53.9 28.3 1,527

Sediment thickness in Offshore of Santa Barbara map area

Offshore of Santa Barbara map area 103.6 3.4 350.2
30

Chapter 8. Geologic and Geomorphic Map of the Offshore of Santa 

Barbara Map Area (Sheet 10) 

By Samuel Y. Johnson, Andrew C. Ritchie, James E. Conrad, Eleyne L. Phillips, Gordon G. Seitz, and Carlos I. 

Gutierrez

Geologic and Geomorphic Summary

Marine geology and geomorphology were mapped in the Offshore of Santa Barbara 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 1.33 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). 

The onshore geology was compiled from Dibblee (1986a,b) and Minor and others (2009). Unit 

ages, which are derived from these sources, reflect local stratigraphic relations.

The offshore part of the map area largely consists of a relatively shallow (less than 75 m deep), 

gently offshore-dipping (less than 1°) shelf underlain by sediments derived primarily from relatively 

small coastal watersheds that drain the Santa Ynez Mountains. Shelf deposits are primarily sand (unit 

Qms) at water depths less than about 35 to 50 m and, at depths greater than about 35 to 50 m, are the 

more fine-grained sediments (very fine sand, silt, and clay) of unit Qmsf. The boundary between units 

Qms and Qmsf is based on observations and extrapolation from sediment sampling (see, for example, 

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

boundary between units Qms and Qmsf should be considered transitional and approximate and is 

expected to shift as a result of seasonal- to annual- to decadal-scale cycles in wave climate, sediment 

supply, and sediment transport. 

Coarser grained deposits (coarse sand to boulders) of unit Qmsc, which are recognized on the 

basis of their high backscatter and, in some cases, their moderate seafloor relief (sheets 1, 2, 3), are 

found most prominently in a large (about 0.75 km2

) lobe that is present from about 1,800 to 3,600 m 

offshore of the mouth of Arroyo Burro, in water depths of about 36 to 65 m. The lobe is inferred to 

consist of coarse-grained sediment (coarse sand to boulders) that is resistant to erosion. Although these 

coarse-grained deposits almost certainly are derived from Arroyo Burro, the lobe could represent either 

the underflow deposits of late Holocene floods or a relict geomorphologic feature, having been 

deposited in shallower marine deltaic (or even alluvial?) environments at lower sea levels in the latest 

Pleistocene and early Holocene. Unit Qmsc also is present in shallower water (depths of about 10 to 20 

m), most notably in a small area (approximately 0.09 km2) that extends offshore from Montecito Creek, 

in the eastern part of the map area. 

The presence of coarser grained sediment (coarse sand and possibly gravel) also is inferred in 

shallower water (depths of 10 to 20 m) offshore from Arroyo Burro, but these deposits are mapped as 

unit Qmss because they are found within arcuate scour depressions that have been referred to as 

“rippled scour depressions” (see, for example, Cacchione and others, 1984; Phillips, 2007) or “sorted 

bedforms” (see, for example, Murray and Thieler, 2004; Goff and others, 2005; Trembanis and Hume, 

2011). Although the general area in which Qmss scour depressions are found is not likely to change 

substantially, the boundaries of the unit(s), as well as the locations of individual depressions and their 

intervening flat sand sheets, likely are ephemeral, changing during significant storm events.

Hydrocarbon-seep-induced topography, which is present most prominently along the axis of 

anticlines, includes many features (described by Keller and others, 2007) along the trend of the Mid-
31

Channel Anticline, about 10 km south of the map area in the Santa Barbara Channel. Geologic map units 

associated with hydrocarbon emissions in the map area include grouped to solitary pockmarks (unit 

Qmp) and asphalt (tar) deposits (unit Qas), as well as areas of undifferentiated hydrocarbon-related 

features (unit Qhfu) that probably include a mix of mounds, mud volcanoes, pockmarks, carbonate mats, 

and other constructional and erosional “seabed forms” (see Keller and others, 2007), all of which are 

superimposed on consolidated, undivided Miocene and Pliocene bedrock (unit Tbu).

Offshore bedrock exposures are assigned to the Miocene Monterey Formation (unit Tm) and to 

the undivided Miocene and Pliocene bedrock unit (Tbu), primarily on the basis of extrapolation from the 

onland geologic mapping of Minor and others (2009), as well as the geologic cross sections of Redin 

(2005). These cross sections, which are constrained by industry seismic-reflection data and petroleum 

well logs, suggest that a considerable part of the undivided bedrock unit may belong to the Pliocene and 

Pleistocene Pico Formation. Bedrock is, in some places, overlain by a thin (less than 1 m?) veneer of 

sediment, recognized on the basis of high backscatter, flat relief, continuity with moderate- to high-relief 

bedrock outcrops, and (in some cases) high-resolution seismic-reflection data; these areas, which are 

mapped as composite units Qms/Tbu or Qms/Tm, are interpreted as ephemeral sediment layers that 

may or may not be continuously present, depending on storms, seasonal and (or) annual patterns of 

sediment movement, or longer term climate cycles. The relative proportions of all offshore map units are 

shown in table 8–1. 

The Santa Barbara Channel region, including the map area, has a long history of petroleum 

production (Barnum, 1998). The Monterey Formation is the primary petroleum-source rock in the Santa 

Barbara Channel, and the Pico Formation is one of the primary petroleum reservoirs. The bedrock units 

typically are exposed in structural highs that include uplifts associated with the partly blind(?), southdipping Rincon Creek Fault Zone and the outer shelf anticlinal uplift that developed above the south 

strand of the Red Mountain Fault in the southwestern part of the map area. 

Table 8–1. Areas and relative proportions of offshore geologic map units in Offshore of Santa Barbara map area.

Map Unit Area (m2) Area (km2) Percent of total area

Artificial fill unit

af 290,044 0.29 0.27

Marine sedimentary units

Qas, Qas? 62,887 0.06 0.06

Qms 58,991,008 58.99 55.22

Qmp 16,765 0.02 0.02

Qmsc 1,645,599 1.65 1.54

Qmsf 31,424,542 31.42 29.41

Qmss 284,552 0.28 0.27

Total, sedimentary units 92,425,352 92.43 86.51

Marine bedrock and (or) shallow bedrock units

Qms/Tbu 7,944,152 7.94 7.44

Qhfu 2,250,609 2.25 2.11

Tbu, Tbu? 3,104 0.00 0.00

Total, undifferentiated bedrock units 10,197,865 10.20 9.55

Qms/Tm 346,412 0.35 0.32

Tm 3,575,796 3.58 3.35

Total, Monterey Formation 3,922,209 3.92 3.67

Total, all bedrock units 14,120,073 14.12 13.22

Total, Offshore of Santa Barbara map area 106,835,469 106.84 100.00
32

The Offshore of Santa Barbara map area is in the Ventura Basin, in the southern part of the 

Western Transverse Ranges geologic province, which is north of the California Continental Borderland 

(Fisher and others, 2009). This province has undergone significant north-south compression since the 

Miocene, and recent GPS data suggest north-south shortening of about 6 mm/yr (Larson and Webb, 

1992). The active, east-west-striking Red Mountain and Rincon Creek Faults and their related folds are 

some of the structures on which this shortening occurs. This fault system, in aggregate, extends for 

about 100 km through the Ventura and Santa Barbara Basins and represents an important earthquake 

hazard (see, for example, Fisher and others, 2009). Very high uplift rates of onland marine terraces from 

More Mesa (2.2 mm/yr), in the western part of the map area, to Summerland (0.7 mm/yr), a few 

kilometers east of the map area, are further indication of rapid shortening in this region (Keller and 

Gurrola, 2000). 

DESCRIPTION OF MAP UNITS

OFFSHORE GEOLOGIC AND GEOMORPHIC UNITS

[Note that, where older units (typically, bedrock) are overlain by thin (<1 m thick) Quaternary deposits, 

composite units are mapped. These composite units, which are shown with gray stipple pattern on older 

unit, are designated by composite label indicating both overlying sediment cover and lower (older) unit, 

separated by slash (for example, Qms/Tm indicates that thin sheet of Qms overlies Tm)]

af Artificial fill (late Holocene)—Rock, sand, and mud; placed and (or) dredged; associated 

with Santa Barbara Harbor. Also includes seafloor substantially modified by human 

activity

Qms Marine nearshore and shelf deposits (late Holocene)—Mostly sand; ripple marks 

common. Found on gently seaward-dipping (less than 1°) surface that extends from 

nearshore to water depths of about 35 to 70 m 

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

sand, gravel, and boulders; forms large, low-relief lobe about 1,800 m offshore of 

mouth of Arroyo Burro, in water depths of about 36 to 65 m. Also found as small 

patches on gently seaward-dipping surface offshore of Montecito Creek, in water 

depths less than about 20 m. Recognized primarily on basis of high backscatter and 

low to moderate relief

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

commonly bioturbated; found on gently seaward-dipping (less than 1°) surface at 

depths that range from about 35 to 70 m 

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

gravel; found as single depressions or in fields of depressions interspersed with 

elevated shelf sediments (unit Qms). Occupies three small fields (0.025 to 0.15 km2

) 

a few hundred meters east of mouth of Arroyo Burro (fig. 1–2) at water depths of 10 

to 20 m. Depressions, which typically are 25 to 50 cm deep, have sharp boundaries on 

shoreward edge that grade to diffuse, low-relief boundaries on offshore edge. In map 

area, backscatter data and direct camera observations show small intensity contrasts 

that suggest that depressions are filled with sand that is coarser than intervening 

elevated sandy shelf deposits. General area in which unit is found is not likely to 

change substantially, but boundaries of unit(s) and locations of individual depressions 

(and intervening flat sheets) likely are ephemeral, changing during significant storm 

events 
33

Qmp Marine pockmarks (late Holocene)—Sand and mud, in circular to elliptical pockmarks. 

Pockmarks, which are solitary or grouped, range in size from 50 to 150 m along their 

long axes, typically are 20 to 40 cm deep, and commonly have central cone that has

raised relief of as much as 150 cm

Qas Asphalt deposits (Holocene)—Asphalt (tar); weathered and biodegraded oil derived from 

underlying or nearby natural hydrocarbon seeps. Most commonly found along or 

adjacent to faults or anticlinal axes. Has local high relief and backscatter

Qhfu Mixed hydrocarbon-seep-related features and marine deposits (Holocene)—

Hydrocarbon-seep-related features (see Keller and others, 2007, their table 1) that 

have irregular seafloor relief and high backscatter; probably includes mixed and 

coalescing mounds, pockmarks, carbonate mats, and mud volcanoes and cones. 

Superimposed on bedrock; most commonly found along or adjacent to faults or 

anticlinal axes

Tbu Bedrock, undivided (Pliocene and Miocene)—Consists of undivided strata of the Pico, 

Sisquoc, and Monterey Formations. Stippled areas (composite unit Qms/Tbu) 

indicate where thin sheets of Qms overlie unit 

Tm Monterey Formation (Miocene)—Predominantly well-bedded siliceous and calcareous 

mudstone and shale. Stippled areas (composite unit Qms/Tm) indicate where thin 

sheets of Qms overlie unit 

ONSHORE GEOLOGIC AND GEOMORPHIC UNITS

[Units are compiled from Dibblee (1986a,b) and Minor and others (2009); unit ages, which are from 

these sources, reflect local stratigraphic relations]

af Artificial fill (late Holocene)—Engineered and (or) nonengineered 

Qb Beach deposits (late Holocene)—Unconsolidated, loose, fine- to coarse-grained sand; well 

sorted. Mapped in coastal band from shoreline to highest elevation of swash zone 

Qes Coastal-estuarine deposits (late Holocene)—Locally organic-rich clay, silt, and 

subordinate sand. Mapped primarily in tidally influenced environments

Qa Channel alluvium (late Holocene)—Unconsolidated sediments, primarily pebble to boulder 

gravel, in floors and banks of modern stream channels. Commonly incised as much as 

5 m into alluvial deposits of associated floodplain (unit Qyf) 

Qas Asphalt deposits (Holocene)—Black asphalt (tar) that represents weathered and 

biodegraded oil derived from nearby natural hydrocarbon seeps. Found along 

shoreline near west edge of map area

Qyf Alluvium and colluvium, undivided (Holocene and late Pleistocene)—Poorly 

consolidated silt, sand, and gravel deposits, in modern drainages and piedmont 

alluvial fans and floodplains 

Qyd Debris-flow deposits (Holocene and late Pleistocene)—Massive, weakly consolidated 

rock-debris breccia; derived from upslope rock units. Mainly located along lower 

flanks of Santa Ynez Mountains 

Qc Colluvium (Holocene and late Pleistocene)—Poorly consolidated, poorly stratified, and 

poorly sorted sediments that mantle gentle to moderate slopes; formed by weathering 

and downslope movement of bedrock debris 

Qls Landslide deposits (Holocene to middle Pleistocene)—Deposits of diverse slopemovement processes; ranges from poorly sorted and disrupted mixtures of rock 

fragments and soil to relatively intact bedrock slump blocks. Thickness of largest 

landslide deposits, as much as 60 m 
34

Qomp Marine-terrace deposits (late Pleistocene)—Weakly to moderately consolidated, variably 

stratified, fossiliferous gravel, sand, and silt; deposited as marine intertidal, beach, 

and estuarine deposits; commonly overlain by nonmarine eolian, alluvial, and 

colluvial deposits. Marine-terrace deposits rest on elevated marine wave-cut 

platforms and form single terraces or flights of terraces that, in Santa Barbara coastal 

area, range in elevation from 10 to 90 m (30–300 ft) and in age from 105,000 

(oxygen-isotope substage 5c) to 45,000 (substage 3a) years old 

Qoa2 Alluvial deposits (late Pleistocene)—Weakly consolidated, stratified silt, sand, and gravel; 

forms low, rounded, moderately dissected terraces and piedmont alluvial fans. Present

at elevations higher than modern coastal-piedmont surface. Thickness, may exceed 20 

m locally

Qoa1 Older alluvial deposits (late and middle Pleistocene)—Moderately consolidated, crudely 

stratified, poorly sorted sand and sandstone, gravel, conglomerate, and breccia, as 

well as rare interbeds of clay, silt, and mudstone; makes up proximal to distal facies 

of alluvial fans shed from Santa Ynez Mountains. Unit forms dissected, gently southsloping, elevated terraces, interfluvial caps, and other erosional remnants. Thickness,

as much as 35 m 

Qca Casitas Formation (late and middle Pleistocene)—Nonmarine, moderately to wellconsolidated siltstone and silt, sandstone and sand, and conglomerate and gravel; 

deposited mainly as alluvium, likely shed from Santa Ynez Mountains. Conglomerate 

and gravel contain greater percentage of Sespe Formation–derived clasts than older 

alluvial deposits (unit Qoa1) mapped nearby. Maximum exposed thickness, 50 m in 

Santa Barbara coastal region

Qbx Shale-clast sedimentary breccia (middle Pleistocene)—Nonmarine breccia and 

conglomerate; mostly composed of clasts of shale and mudstone derived from the 

Monterey Formation. Breccia inferred to be locally derived paleocolluvium. 

Thickness, locally exceeds 10 m 

Qsb Santa Barbara Formation (middle and early Pleistocene)—Chiefly marine, friable, 

bioturbated and massive sandstone; pale gray, pale buff, and pale tan; includes 

subordinate interbeds and intervals of shale, siltstone, and silty to clayey sandstone. 

Contains diverse assemblage of marine invertebrate fossils. Rare conglomeratic 

lenses become more common upsection, and uppermost part of unit locally 

interfingers with nonmarine conglomerates of the older alluvial deposits unit (Qoa1) 

or the Casitas Formation (unit Qca) 

Unnamed sedimentary rocks east of Goleta Pier (Pleistocene and Pliocene?)—Marine 

conglomerate, sandstone, siltstone, and mudstone. Mapped as the following three 

distinct units:

Qcg Conglomeratic unit (middle and early Pleistocene)—Conglomerate, sandstone, 

siltstone, and mudstone; probably deposited in ancient submarine canyon eroded into 

underlying Pleistocene and Pliocene rocks (units Qss, Tsq). Contains marine fossils. 

Conglomerate contains clasts derived from the Sisquoc Formation (unit Tsq) and the 

Monterey Formation (units Tmu, Tmm, Tml), as well as older units. Width of paleo–

submarine channel exposed in sea cliff is about 610 m; minimum thickness in channel 

axis, 33 m 

Qss Sandstone-rich unit (early Pleistocene?)—Laminated and bioturbated sandstone, 

siltstone, and subordinate mudstone and conglomerate. Contains marine fossils and 

clasts derived from the Sisquoc Formation (unit Tsq) and the Monterey Formation 

(units Tmu, Tmm, Tml). Exposed thickness, 45 to 60 m 
35

QTst Siltstone unit (early Pleistocene and late Pliocene?)—Massive and extensively 

bioturbated siltstone, mudstone, and silty sandstone. Contains marine fossils. Exposed 

thickness, about 45 m 

Tsq Sisquoc Formation (early Pliocene and late Miocene)—Marine, tan- to white-weathering

diatomaceous mudstone and shale, conglomerate, and subordinate dolomite. 

Distinguished by thick beds of conglomerate containing angular clasts (commonly as 

much as 1 m across; some blocks as large as 10 m) derived from the Monterey 

Formation. Both base and top are erosional unconformities 

Monterey Formation (Miocene)—Marine, predominantly well-bedded, siliceous and 

calcareous mudstone and shale, with subordinate porcelanite and dolomite. Contains 

abundant microfossils. Maximum composite thickness of the Monterey Formation in 

this area estimated to be about 830 m. The Monterey Formation is divided into the 

following three subunits, which are distinguished on basis of stratigraphic position, 

lithology, and age:

Tmu Upper siliceous unit (late Miocene)—Mainly white- to tan-weathering diatomaceous 

mudstone and shale, with subordinate dolomite and porcelanite. Thickness in Santa 

Barbara coastal region ranges from about 50 to 250 m

Tmm Middle shale unit (late and middle Miocene)—White-weathering shale, mudstone, 

dolomite, porcelanite, phosphorite, and subordinate tuff. Thickness in Santa Barbara 

coastal region estimated to range from 70 to 180 m 

Tml Lower calcareous unit (middle and early Miocene)—Calcareous, siliceous, and 

phosphatic, white- to tan-weathering mudstone and shale, with subordinate dolomite, 

porcelanite, breccia, glauconitic sandstone, and tuff. In places, unit exhibits 

intraformational deformation (including breccia) that may have formed by 

gravitational slumping shortly after deposition. Thickness, as much as 250 m 

Tr Rincon Shale (early Miocene)—Marine, primarily massive and thick-bedded, light-brownweathering mudstone, with subordinate dolomite, siliceous shale, sandstone, and tuff. 

Mudstone is bioturbated, massive, and pervasively hackly fractured; locally, contains 

abundant microfossils. Single or multiple white-weathering tuff layers limited to 

upper 10 m of unit. Thickness ranges from about 400 to 460 m 

Tv Vaqueros Formation (late Oligocene)—Shallow-marine, massive, bioturbated, resistant, 

light-tan-weathering sandstone. Uppermost part consists of thinly interbedded 

sandstone, siltstone, and mudstone; base typically marked by 50- to 150-cm-thick, 

thinly bedded, calcareous conglomerate containing abundant fossil-shell fragments. 

Within Santa Barbara coastal region, thickness varies from about 75 to 150 m 

Sespe Formation (Oligocene and late Eocene)—Interbedded nonmarine, fluvial, maroon, 

reddish-brown, and greenish- to pinkish-gray sandstone, siltstone, mudstone, and 

conglomerate. In Santa Barbara coastal region, divided into three subunits that are 

distinguished mainly by differences in stratigraphic position, lithology, provenance, 

and age. Intraformational unconformity, which represents depositional hiatus lasting 

much or all of early Oligocene time, separates lower (Tspl) and middle (Tspm) 

subunits. Composite thickness in Santa Barbara coastal region ranges from about 700 

to more than 1,500 m 

Tspu Upper sandstone and mudstone unit (late Oligocene)—Interbedded sandstone, 

siltstone, and mudstone that weather to various shades of maroon, buff, pale green, 

tan, and gray; proportions of different sedimentary rock types vary both laterally and 

vertically throughout section. Sandstones commonly are broadly lenticular, 

laminated, and thin to thick bedded. Thickens eastward across map area from about 
36

500 to more than 1,000 m 

Tspm Middle conglomerate and sandstone unit (Oligocene)—Interbedded conglomerate, 

sandstone, and mudstone; weathers to various shades of maroon, tan, and palegreenish gray; proportions of different sedimentary rock types vary both laterally and 

vertically throughout section. Polymict conglomerate clasts include abundant chert 

and lithic sandstone, likely derived from Franciscan Complex source terranes. As 

much as 340 m thick in Santa Barbara coastal region

Tspl Lower conglomerate and sandstone unit (early? Oligocene and late Eocene)—

Interbedded conglomerate, conglomeratic sandstone, sandstone, mudstone, and minor 

shale; mostly weathers to various distinctive shades of salmon gray, reddish gray, 

pale-pinkish gray, and tan; proportions of different sedimentary rock types vary both 

laterally and vertically throughout section. Resistant sandstones and conglomerates 

form hogbacks. Sandstones commonly are arkosic, and polymict conglomerates 

contain abundant rounded quartzitic, granitoid, metamorphic, and volcanic clasts, 

likely derived from Mojave Desert source terranes

Tcw Coldwater Sandstone (late? and middle Eocene)—Shallow-marine, thin- to thick-bedded 

sandstone, which weathers to distinctive pale shades of buff, yellow, tan, and brown, 

and subordinate gray, olive-gray, and greenish-gray siltstone, shale, and mudstone 

interbeds and thin intervals; resistant sandstone beds form hogbacks where steeply 

dipping; upper part of unit locally is conglomeratic and rich in fossil oyster shells. 

Within Santa Barbara coastal region, unit is about 750 to 1,000 m thick 

Tcw-sh Shale unit (late? and middle Eocene)—Fine-grained, bedded siltstone and shale, with 

sandstone interbeds. As much as 240 m thick 

Tcd Cozy Dell Shale (Eocene)—Marine, dark- to light-gray, silty micaceous shale and 

sandstone, with interbeds of shale. Thickness, as much as 600 m in Santa Barbara 

coastal region

Tma Matilija Sandstone (Eocene)—Marine, tan arkosic sandstone, with thin partings of gray 

micaceous shale. Thickness, as much as 540 m in Santa Barbara coastal region

Tj Juncal Formation (Eocene)—Marine, dark-gray to gray-white shale and sandstone. 

Thickness, as much as 1,100 m in Santa Barbara coastal region 

Kush Jalama Formation (Late Cretaceous)—Predominantly marine, dark-gray to black, 

micaceous clay shale, with minor hard, tan sandstone interbeds (Dibblee, 1950, 

1981). Thickness, as much as 700 m in Santa Barbara coastal region
37

Chapter 9. Predictive Distribution of Benthic Macro-Invertebrates for 

the Offshore of Santa Barbara Map Area and the Santa Barbara Channel 

Region (Sheet 11)

By Lisa M. Krigsman, Mary M. Yoklavich, Nadine E. Golden, and Guy R. Cochrane 

Modeling the distribution of ecologically and economically important species provides managers 

and conservation planners with information on a broad spatial scale that is useful to coastal 

management, ocean energy, marine protected areas, and marine spatial planning. Sheet 11 displays 

predictive models of occurrence for common benthic macro-invertebrate taxa and maps the probability 

of occurrence of these taxa in the Santa Barbara Channel region (Krigsman and others, 2012). These 

models are based on real-time biological observations of all macro-organisms made during ground-truth 

surveys (sheet 6) conducted in 2008 and 2009; the observations were made during a 10-second interval 

every minute along video transects, which were approximately 1 km in length (sheet 6; see also, chapter 

5 of this pamphlet). These transects produced a total of 923 observations from Refugio Beach (34.5° N., 

120.1° W.) to Hueneme Canyon (34.1° N., 119.2° W.). 

Five invertebrate taxa—cup corals, hydroids, short sea pens, tall sea pens, and brittle stars (which 

protrude out of the sediment)—were selected for modeling purposes because of their frequent 

occurrence in the Santa Barbara Channel; all are structure-forming components of valuable habitat for 

groundfish species (Krigsman and others, 2012). Presence-absence data for the selected invertebrates 

were fit to multiple generalized linear models using a combination of three covariates—geographic 

location, seafloor character (sheet 5), and shaded-relief bathymetry (sheet 2)—as well as relevant 

interaction terms. Geographic locations for the five observed invertebrates were derived from analysis of 

the video data from an area along the mainland coast of the Santa Barbara Channel; the Offshore of 

Carpinteria map area was excluded because of insufficient data. Three statistically different locations 

were identified on the basis of a community-structure analysis: (1) the Hueneme Canyon and Vicinity 

and Offshore of Ventura map areas; (2) the Offshore of Santa Barbara and Offshore of Coal Oil Point 

map areas; and (3) the Offshore of Refugio Beach map area. Best-fit models were selected for each 

invertebrate on the basis of Akaike’s Information Criterion (AIC) (Akaike, 1974), a best-fit model being 

defined as the one that has the fewest parameters within two AIC points of the minimum score.

The seafloor in the Offshore of Santa Barbara map area is predominantly Class I (unconsolidated 

sediment); in addition, a large reef made up of Class II (mixed habitat) and Class III (rugose rock) is 

present beyond the Santa Barbara Harbor (sheet 5; see also, chapter 4 in this pamphlet). Cup corals 

(Map D on sheet 11), a benthic cnidarian typically found on rocky habitat, have a moderate to high 

probability of occurrence in areas where suitable habitat is present. Hydroids (Map C on sheet 11), 

another benthic cnidarian found on rocky habitat, have a low probability of occurrence in the area of the 

large reef beyond Santa Barbara Harbor; however, as depth increases, so does the probability of 

occurrence in areas of mixed sediment and rugose rock. 

Sea pens, also members of the phylum Cnidaria, are divided into two groups—short and tall—on 

the basis of their size. Sea pens less than 60 cm in height are identified as short sea pens (Stylatula spp. 

and Virgularia spp.); those taller than 60 cm are identified as tall sea pens (Halipteris spp.) (Maps B and 

A, respectively, on sheet 11). Sea pens typically are associated with unconsolidated and mixed sediment 

because their rootlike base anchors them to the seafloor. Short sea pens have the highest probability of 

occurrence on unconsolidated sediment at depths of between 30 and 60 m, whereas tall sea pens have 

the highest probability of occurrence at depths greater than 60 m. 

Brittle stars (Map E on sheet 11) can occur in such high densities in the sediment that they create 

a thick carpet on the seafloor. Like sea pens, they typically are associated with unconsolidated and 
38

mixed sediment into which they burrow; however, they also are found in cracks and crevices within 

rugose rock. In the Offshore of Santa Barbara map area, brittle stars have a moderate probability of 

occurrence in unconsolidated sediment at depths between 30 and 60 m; however, at depths less than 30 

m and also greater than 60 m, the probability of occurrence is low. 

These predictive maps are based on data available from the California Seafloor Mapping 

Program (location, habitat type, and bathymetry). Other factors such as ocean currents (Cudaback and 

others, 2005), water temperature (Bingham and others, 1997), larval distribution (Grantham and others, 

2003), and recruitment and mortality (Keough and Downes, 1982) also can significantly influence the 

distribution and abundance of these benthic macro-invertebrate taxa.
39

Acknowledgments

This publication was funded by the California Ocean Protection Council and the U.S. Geological 

Survey (USGS) Coastal and Marine Geology Program. We are very grateful to USGS editor Taryn 

Lindquist for helping us develop the templates and formats for this series of publications, and for 

invaluable editorial review and suggestions. Alan Allwardt, Tom Lorenson, and Scott Starratt (all 

USGS) provided constructive reviews. 
40

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