California State Waters Map Series—Offshore of Gaviota, California

Open-File Report 2018-1023
By: , and 
Edited by: Samuel Y. Johnson and Susan A. Cochran

Links

  • Document: Pamphlet (1.5 MB pdf)
  • Sheets:
    • Sheet 1 (13.9 MB pdf) Colored Shaded-Relief Bathymetry, Offshore of Gaviota Map Area, California By Peter Dartnell and Rikk G. Kvitek
    • Sheet 2 (17.7 MB pdf) Shaded-Relief Bathymetry, Offshore of Gaviota Map Area, California By Peter Dartnell and Rikk G. Kvitek
    • Sheet 3 (20.5 MB pdf) Acoustic Backscatter, Offshore of Gaviota Map Area, California By Peter Dartnell and Rikk G. Kvitek
    • Sheet 4 (16.7 MB pdf) Data Integration and Visualization, Offshore of Gaviota Map Area, California By Peter Dartnell
    • Sheet 5 (21.1 MB pdf) Seafloor Character, Offshore of Gaviota Map Area, California By Stephen R. Hartwell and Guy R. Cochrane
    • Sheet 6 (13.5 MB pdf) Marine Benthic Habitats from the Coastal and Marine Ecological Classification Standard, Offshore of Gaviota Map Area, California By Guy R. Cochrane, Stephen R. Hartwell, and Samuel Y. Johnson
    • Sheet 7 (12.4 MB pdf) Seismic-Reflection Profiles, Offshore of Gaviota Map Area, California By Samuel Y. Johnson and Stephen R. Hartwell
    • Sheet 8 (9.9 MB pdf) Local (Offshore of Gaviota Map Area) and Regional (Offshore from Point Conception to Hueneme Canyon) Shallow-Subsurface Geology and Structure, Santa Barbara Channel, California By Samuel Y. Johnson and Stephen R. Hartwell
    • Sheet 9 (14.0 MB pdf) Offshore and Onshore Geology and Geomorphology, Offshore of Gaviota Map Area, California By Stephen R. Hartwell, Samuel Y. Johnson, and Clifton W. Davenport
  • Related Works:
  • Dataset: Data Catalog (html) The GIS data layers for this map are accessible from “California State Waters Map Series—Offshore of Gaviota, California” which is part of California State Waters Map Series Data Catalog. Each GIS data file is listed with a brief description, a small image, and links to the metadata files and the downloadable data files.
  • Metadata: Metadata
  • Open Access Version: Publisher Index Page
  • Download citation as: RIS | Dublin Core

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 the 3-nautical-mile limit of 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 subsurface geology.

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 the region is presently undergoing north-south shortening. The offshore part of the map area lies south of the steep south flank of the Santa Ynez Mountains. The crest of the range, which has a maximum elevation of about 760 m in the map area, lies about 4 km north of the shoreline.

Gaviota is an unincorporated community that has a sparse population (less than 100), and the coastal zone is largely open space that is locally used for cattle grazing. The Union Pacific railroad tracks extend westward along the coast through the entire map area, within a few hundred meters of the shoreline. Highway 101 crosses the eastern part of the map area, also along the coast, then turns north (inland) and travels through Cañada de la Gaviota and Gaviota Pass en route to Buellton. Gaviota State Park lies at the mouth of Cañada de la Gaviota. West of Gaviota, the onland coastal zone is occupied by the Hollister Ranch, a privately owned, gated community that has no public access.

The map area has a long history of petroleum exploration and development. Several offshore gas fields were discovered and were developed by onshore directional drilling in the 1950s and 1960s. Three offshore petroleum platforms were installed in adjacent federal waters in 1976 (platform “Honda”) and 1989 (platforms “Heritage” and “Harmony”). Local offshore and onshore operations were serviced for more than a century by the Gaviota marine terminal, which is currently being decommissioned and will be abandoned in an intended transition to public open space.

 The Offshore of Gaviota map area lies within the western Santa Barbara Channel region of the Southern California Bight, and it is somewhat protected from large Pacific swells from the north and northwest by Point Conception and from south and southwest swells by offshore islands and banks. Much of the shoreline in the map area is characterized by narrow beaches that have thin sediment cover, backed by low (10- to 20-m-high) cliffs that are capped by a narrow coastal terrace. Beaches are subject to wave erosion during winter storms, followed by gradual sediment recovery or accretion in the late spring, summer, and fall months during the gentler wave climate.

The map area lies in the western-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. Sediment supply to the western and central part of the littoral cell is mainly from relatively small coastal watersheds. In the map area, sediment sources include Cañada de la Gaviota (52 km2), as well as Cañada de la Llegua, Arroyo el Bulito, Cañada de Santa Anita, Cañada de Alegria, Cañada del Agua Caliente, Cañada del Barro, Cañada del Leon, Cañada San Onofre, and many others. Coastal-watershed discharge and sediment load are highly variable, characterized by brief large events during major winter storms and long periods of low (or no) flow and minimal sediment load between storms. In recent (recorded) history, the majority of high-discharge, high-sediment-flux events have been associated with El Niño phases of the El Niño–Southern Oscillation climatic pattern.

Shelf width in the Offshore of Gaviota map area ranges from about 4.3 to 4.7 km, and shelf slopes average about 1.0° to 1.2° but are highly variable because of the presence of the large Gaviota sediment bar. This bar extends southwestward for about 9 km from the mouth of Cañada de la Gaviota to the shelf break, is as wide as 2 km, and is by far the largest shore-attached sediment bar in the Santa Barbara Channel. The shelf is underlain by bedrock and variable amounts (0 to as much as 36 m in the Gaviota bar) of upper Quaternary sediments deposited as sea level fluctuated in the late Pleistocene. The trend of the shelf break changes from about 276° to 236° azimuth over a distance of about 12 km, and it ranges in depth from about 91 m to as shallow as 62 to 73 m where significant shelf-break and upper-slope failure and landsliding has apparently occurred. The shelf break in the western part of the map area is notably embayed by the heads of three large (150- to 300-m-wide) channels that have been referred to as “the Gaviota Canyons” or as “Drake Canyon,” “Sacate Canyon,” and “Alegria Canyon.”

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 in the nearshore and rocky-reef communities in deeper water. The potential marine benthic habitat types mapped in the Offshore of Gaviota map area are directly related to its Quaternary geologic history, geomorphology, and active sedimentary processes. These potential habitats lie primarily within the Shelf (continental shelf) but also partly within the Flank (basin flank or continental slope) megahabitats. The fairly homogeneous seafloor of sediment and low-relief bedrock provides characteristic habitat for rockfish, groundfish, crabs, shrimp, and other marine benthic organisms. Several areas of smooth sediment form nearshore terraces that have relatively steep, smooth fronts, which may be attractive to groundfish. Below the steep shelf break, soft, unconsolidated sediment is interrupted by the heads of several submarine canyons and rills, some bedrock exposures, and small carbonate mounds associated with asphalt mounds and pockmarks, also good potential habitat for rockfish. The map area includes the relatively small (5.2 km2) Kashtayit State Marine Conservation Area, which largely occupies the inner part of the Gaviota sediment bar.

Suggested Citation

Johnson, S.Y., Dartnell, P., Cochrane, G.R., Hartwell, S.R., Golden, N.E., Kvitek, R.G., and Davenport, C.W. (S.Y. Johnson and S.A. Cochran, eds.), 2018, California State Waters Map Series—Offshore of Gaviota, California: U.S. Geological Survey Open-File Report 2018–1023, pamphlet 41 p., 9 sheets, scale 1:24,000, https://doi.org/10.3133/ofr20181023.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Chapter 1. Introduction
  • Chapter 2. Bathymetry and Backscatter-Intensity Maps of the Offshore of Gaviota Map Area (Sheets 1, 2, and 3) 
  • Chapter 3. Data Integration and Visualization for the Offshore of Gaviota Map Area (Sheet 4)
  • Chapter 4. Seafloor-Character Map of the Offshore of Gaviota Map Area (Sheet 5)
  • Chapter 5. Marine Benthic Habitats of the Offshore of Gaviota Map Area (Sheet 6).
  • Chapter 6. Subsurface Geology and Structure of the Offshore of Gaviota Map Area and the Santa Barbara Channel Region (Sheets 7 and 8)
  • Chapter 7. Geologic and Geomorphic Map of the Offshore of Gaviota Map Area (Sheet 9)

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title California State Waters Map Series—Offshore of Gaviota, California
Series title Open-File Report
Series number 2018-1023
DOI 10.3133/ofr20181023
Year Published 2018
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Pacific Coastal and Marine Science Center
Description Pamphlet: iv, 41 p.; 9 Sheets: 52.0 x 36.0 inches or smaller; Data Catalog; Metadata
Country United States
State California
City Gaviota
Online Only (Y/N) Y
Additional Online Files (Y/N) Y