Skip Links

USGS - science for a changing world

Scientific Investigations Map 3319

California State Waters Map Series—Offshore of Refugio Beach, California

By Samuel Y. Johnson, Peter Dartnell, Guy R. Cochrane, Nadine E. Golden, Eleyne L. Phillips, Andrew C. Ritchie, Lisa M. Krigsman, Bryan E. Dieter, James E. Conrad, H. Gary Greene, Gordon G. Seitz, Charles A. Endris, Ray W. Sliter, Florence L. Wong, Mercedes D. Erdey, Carlos I. Gutierrez, Mary M. Yoklavich, Amy E. East, and Patrick E. Hart (Samuel Y. Johnson and Susan A. Cochran, editors)

Thumbnail of Sheet 10 Introduction

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 CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, 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.

The Offshore of Refugio Beach map lies within the western Santa Barbara Channel region of the Southern California Bight. This geologically complex region forms a major biogeographic transition zone, separating the cold-temperate Oregonian province north of Point Conception from the warm-temperate California province to the south. The map area is in the southern part of the Western Transverse Ranges geologic province, which is north of the California Continental Borderland. Significant clockwise rotation—at least 90°—since the early Miocene has been proposed for the Western Transverse Ranges province, and geodetic studies indicate that the region is presently undergoing north-south shortening. Uplift rates (as much as 0.5 mm/yr) that are based on studies of onland marine terraces provide further evidence of significant shortening.

The coastal zone of this map area lies at the steep flank of the Santa Ynez Mountains. The crest of the range, which lies about 8 km from the shoreline (north of the map area), has a maximum elevation of about 780 m. This area is largely open space, partly used for livestock grazing, with no significant towns or population centers. Highway 101 crosses the map area, adjacent to and within a few hundred meters of the shoreline. The most significant developments are the recreational state beaches at El Capitan Beach and Refugio Beach. The beaches are subject to erosion each winter during storm-wave attack, and then they undergo gradual recovery or accretion during the more gentle wave climate of the late spring, summer, and fall months.

The Offshore of Refugio Beach map area lies in the west-central part of the Santa Barbara littoral cell, which is characterized by west-to-east transport of sediment from Point Arguello on the northwest to Hueneme and Mugu Canyons on the southeast. Longshore drift rates have been reported to range from about 160,000 to 800,000 tons/yr, averaging 400,000 tons/yr. Sediment supply to the western and central part of the littoral cell, including the map area, is mainly from relatively small coastal watersheds. Within the map area, these coastal watersheds include (from east to west) Cañada del Capitan, Tajiquas Creek, Arroyo Hondo, Cañada del Molino, and several unnamed canyons and creeks. The Santa Ynez and Santa Maria Rivers, the mouths of which are 80 to 120 km northwest of the map area, are not considered significant sediment sources because Point Conception and Point Arguello provide obstacles to downcoast sediment transport and also because much of their sediment load is trapped in dams. The Ventura and Santa Clara Rivers, the mouths of which are about 70 km to the southeast of the map area, are not sediment sources for the map area.

The offshore part of the map area consists of relatively flat and shallow continental shelf, which dips gently seaward (about 0.8° to 1.0°) so that water depths at the shelf break, roughly coincident with the California’s State Waters limit, are about 80 to 100 m. This part of the Santa Barbara Channel 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. The shelf is underlain by variable amounts of upper Quaternary marine and fluvial sediments deposited as sea level fluctuated in the late Pleistocene.

In the map area, the shelf break is at depths of about 90 m and lies about 5.6 to 6.4 km offshore. Beyond the shelf break, the slope is steep (as much as about 7°) and unstable. Several submarine landslides, including the large (130 km2) Goleta landslide complex, have been documented offshore of Goleta, a few kilometers east of the map area. This compound slump complex may have been initiated more than 200,000 year ago, but it also includes three recent failures that may have been generated 8,000 to 10,000 years ago. A local, 10-m-high tsunami may have been generated from these failure events.

Small folds related to local faulting are superimposed on the homocline that makes up the south flank of the Santa Ynez Mountains. One of these superimposed anticlines hosts the Molino gas field, which was discovered in 1962 and subsequently developed through directional drilling from onshore wells. The Oligocene Sespe and Vaqueros Formations are the reservoirs in the Molino gas field, and the map area includes numerous seafloor hydrocarbon seeps.

Seafloor habitats in the broad Santa Barbara Channel region consist of significant amounts of soft, unconsolidated sediment interspersed with isolated areas of rocky habitat that support kelp-forest communities nearshore and rocky-reef communities in deep water. The potential marine benthic habitat types mapped in the Offshore of Refugio Beach map area are directly related to its Quaternary geologic history, geomorphology, and active sedimentary processes. These potential habitats, which lie primarily within the Shelf (continental shelf) but also partly within the Flank (basin flank or continental slope) megahabitats, primarily are composed of soft sediment interrupted by a few carbonate mounds. This homogeneous seafloor of sediment and low-relief bedrock provides promising habitat for groundfish, crabs, shrimp, and other marine benthic organisms.

Chapters in the Pamphlet

Chapter 1. Introduction, By Samuel Y. Johnson

Chapter 2. Bathymetry and Backscatter-Intensity Maps of the Offshore of Refugio Beach Map Area (Sheets 1, 2, and 3), By Peter Dartnell

Chapter 3. Data Integration and Visualization for the Offshore of Refugio Beach Map Area (Sheet 4), By Peter Dartnell

Chapter 4. Seafloor-Character Map of the Offshore of Refugio Beach Map Area (Sheet 5), By Eleyne L. Phillips, Mercedes D. Erdey, and Guy R. Cochrane

Chapter 5. Ground-Truth Studies for the Offshore of Refugio Beach Map Area (Sheet 6), By Nadine E. Golden and Guy R. Cochrane

Chapter 6. Potential Marine Benthic Habitat Map of the Offshore of Refugio Beach Map Area (Sheet 7), By H. Gary Greene and Charles A. Endris

Chapter 7. Subsurface Geology and Structure of the Offshore of Refugio Beach Map Area and the Santa Barbara Channel Region (Sheets 8 and 9), By Samuel Y. Johnson, James E. Conrad, Eleyne Phillips, Andrew Ritchie, Florence L. Wong, Ray W. Sliter, Amy E. East, and Patrick E. Hart

Chapter 8. Geologic and Geomorphic Map of the Offshore of Refugio Beach Map Area (Sheet 10), By James E. Conrad, Andrew C. Ritchie, Samuel Y. Johnson, Gordon G. Seitz, and Carlos I. Gutierrez

Chapter 9. Predicted Distribution of Benthic Macro-Invertebrates for the Offshore of Refugio Beach Map Area and the Santa Barbara Channel Region (Sheet 11), By Lisa M. Krigsman, Mary M. Yoklavich, Nadine E. Golden, and Guy R. Cochrane

Also of Interest

Scientific Investigations Map 3225California State Waters Map Series—Hueneme Canyon and Vicinity, California, by Samuel Y. Johnson and others.

Scientific Investigations Map 3254California State Waters Map Series—Offshore of Ventura, California, by Samuel Y. Johnson and others.

Scientific Investigations Map 3261California State Waters Map Series—Offshore of Carpinteria, California, by Samuel Y. Johnson and others.

Scientific Investigations Map 3281California State Waters Map Series—Offshore of Santa Barbara, California, by Samuel Y. Johnson and others.

Scientific Investigations Map 3302California State Waters Map Series—Offshore of Coal Oil Point, California, by Samuel Y. Johnson and others

First posted March 18, 2015

  • Sheet 1 PDF Colored Shaded-Relief Bathymetry, Offshore of Refugio Beach Map Area, California (39" x 36"; 20.4 MB)
  • Sheet 2 PDF Shaded-Relief Bathymetry, Offshore of Refugio Beach Map Area, California (39" x 36"; 19.6 MB)
  • Sheet 3 PDF Acoustic Backscatter, Offshore of Refugio Beach Map Area, California (39" x 36"; 24.8 MB)
  • Sheet 4 PDF Data Integration and Visualization, Offshore of Refugio Beach Map Area, California (46" x 36"; 19 MB)
  • Sheet 5 PDF Seafloor Character, Offshore of Refugio Beach Map Area, California (52" x 35"; 23.5 MB)
  • Sheet 6 PDF Ground-Truth Studies, Offshore of Refugio Beach Map Area, California (46" x 36"; 22 MB)
  • Sheet 7 PDF Potential Marine Benthic Habitats, Offshore of Refugio Beach Map Area, California (46" x 36"; 12.8 MB)
  • Sheet 8 PDF Seismic-Reflection Profiles, Offshore of Refugio Beach Map Area, California (46" x 36"; 19.3 MB)
  • Sheet 9 PDF Local (Offshore of Refugio Beach Map Area) and Regional (Offshore from Refugio Beach to Hueneme Canyon) Shallow-Subsurface Geology and Structure, Santa Barbara Channel, California (48" x 36"; 19.7 MB)
  • Sheet 10 PDF Offshore and Onshore Geology and Geomorphology, Offshore of Refugio Beach Map Area, California (49" x 36"; 33.5 MB)
  • Sheet 11 PDF Predicted Distribution of Benthic Macro-Invertebrates, Offshore of Refugio Beach Map Area and Santa Barbara Channel Region, California (53" x 36"; 11.6 MB)

Data:

  • The GIS data layers for this map are accessible from “Data Catalog—Offshore of Refugio Beach, California,” which is part of California State Waters Map Series Data Catalog (Data Series 781). The links below will take you there.
  • Metadata
  • Data Catalog–Offshore of Refugio Beach, California. Each GIS data file is listed with a brief description, a small image, and links to the metadata files and the downloadable data files.

This publication is online only

For additional information, contact:
Contact Information, Pacific Coastal and Marine Science Center
U.S. Geological Survey
Pacific Science Center
400 Natural Bridges Drive
Santa Cruz, CA 95060
http://walrus.wr.usgs.gov/

Part or all of this report is presented in Portable Document Format (PDF). For best results viewing and printing PDF documents, it is recommended that you download the documents to your computer and open them with Adobe Reader. PDF documents opened from your browser may not display or print as intended. Download the latest version of Adobe Reader, free of charge.


Suggested citation:

Johnson, S.Y., Dartnell, P., Cochrane, G.R., Golden, N.E., Phillips, E.L., Ritchie, A.C., Krigsman, L.M., Dieter, B.E., Conrad, J.E., Greene, H.G., Seitz, G.G., Endris, C.A., Sliter, R.W., Wong, F.L., Erdey, M.D., Gutierrez, C.I., Yoklavich, M.M., East, A.E., and Hart, P.E. (S.Y. Johnson and S.A. Cochran, eds.), 2015, California State Waters Map Series—Offshore of Refugio Beach, California: U.S. Geological Survey Scientific Investigations Map 3319, pamphlet 42 p., 11 sheets, scale 1:24,000, https://dx.doi.org/10.3133/sim3319.

ISSN 2329-132X (online)




Accessibility FOIA Privacy Policies and Notices

USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: https://pubs.usgs.gov/sim/3319/
Page Contact Information: Contact USGS
Page Last Modified: Thursday, December 01, 2016, 05:32:29 PM