California State Waters Map Series — Offshore of Point Conception, California

Open-File Report 2018-1024
By:
Edited by: Samuel Y. Johnsonand Susan A. Cochran

Links

  • Document: Pamphlet (892 KB pdf)
  • Sheets:
    • Sheet 1 (16.3 MB pdf) Colored Shaded-Relief Bathymetry, Offshore of Point Conception Map Area, California By Peter Dartnell and Rikk G. Kvitek
    • Sheet 2 (21.3 MB pdf) Shaded-Relief Bathymetry, Offshore of Point Conception Map Area, California By Peter Dartnell and Rikk G. Kvitek
    • Sheet 3 (21.6 MB pdf) Acoustic Backscatter, Offshore of Point Conception Map Area, California By Peter Dartnell and Rikk G. Kvitek
    • Sheet 4 (16.5 MB pdf) Data Integration and Visualization, Offshore of Point Conception Map Area, California By Peter Dartnell
    • Sheet 5 (21.8 MB pdf) Seafloor Character, Offshore of Point Conception Map Area, California By Stephen R. Hartwell and Guy R. Cochrane
    • Sheet 6 (11.9 MB pdf) Marine Benthic Habitats from the Coastal and Marine Ecological Classification Standard, Offshore of Point Conception Map Area, California By Guy R. Cochrane, Stephen R. Hartwell, and Samuel Y. Johnson
    • Sheet 7 (10.7 MB pdf) Seismic-Reflection Profiles, Offshore of Point Conception Map Area, California By Samuel Y. Johnson and Stephen R. Hartwell
    • Sheet 8 (10.0 MB pdf) Local (Offshore of Point Conception 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 (22.4 MB pdf) Offshore and Onshore Geology and Geomorphology, Offshore of Point Conception Map Area, California By Samuel Y. Johnson, Stephen R. Hartwell, 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 Point Conception, 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.
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  • 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 Offshore of Point Conception map area is in the westernmost 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 this region is presently undergoing north-south shortening. The offshore part of the map area lies south of the steep south and west flanks of the Santa Ynez Mountains. The crest of the range, which has a maximum elevation of about 340 m in the map area, lies about 5 km north and east of the arcuate shoreline.

The onland part of the coastal zone is remote and sparsely populated. The road to Jalama Beach County Park provides the only public coastal access in the entire map area. North of this county park, the coastal zone is part of Vandenberg Air Force Base. South of Jalama Beach County Park, most of the coastal zone is part of the Cojo-Jalama Ranch, purchased by the Nature Conservancy in December 2017. A relatively small part of the coastal zone in the eastern part of the map area lies within the privately owned Hollister Ranch. The nearest significant commercial centers are Lompoc (population, about 42,000), about 10 km north of the map area, and Goleta (population, about 30,000), about 50 km east of the map area. The Union Pacific railroad tracks run west and northwest along the coast through the entire map area, within a few hundred meters of the shoreline. The map area has a long history of petroleum exploration, and the seafloor notably includes large asphalt mounds and pockmarks that result from petroleum seepage. Several offshore gas and oil fields were discovered, and some were developed, in and on the margin of California’s State Waters.

Much of the shoreline in the Offshore of Point Conception map area is characterized by narrow beaches that have thin sediment cover above bedrock platforms, backed by low (10- to 20-m-high) cliffs that are capped by a 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 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. Sediment supply to the map area is mainly from relatively small coastal watersheds, including the Jalama Creek–Espada Creek drainage basin (about 63 km2), as well as Cañada del Jolloru, Black Canyon, Wood Canyon, Cañada del Cojo, and Barranca Honda. 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.

Following the coastline, the shelf bends to the north and northwest around Point Conception, and the trend of the shelf break changes from about 298° to 241° azimuth. Shelf width ranges from about 5 km south of Point Conception to about 11 km northwest of it; the slope ranges from about 1.0° to 1.2° to about 0.7° south and northwest of Point Conception, respectively. Southwest of Point Conception, the shelf break and upper slope are incised by a 600-m-wide, 20- to 30-m-deep, south-facing trough, one of five heads of the informally named Arguello submarine canyon.

The map area is located at a major biogeographic transition zone between the east-west-trending Santa Barbara Channel region of the Southern California Bight and the northwest-trending central California coast. North of Point Conception, the coast is subjected to high wave exposure from the north, west, and south, as well as consistently strong upwelling that brings cold, nutrient-rich waters to the surface. Southeast of Point Conception, the Santa Barbara Channel is largely protected from strong north swells by Point Conception and from south swells by the Channel Islands; surface waters are warmer, and upwelling is weak and seasonal.

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 Point Conception 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 are attractive to groundfish. Below the steep shelf break, soft, unconsolidated sediment is interrupted by the heads of several submarine canyons, gullies, and rills, also good potential habitat for rockfish. The map area includes the large (58.3 km2) Point Conception State Marine Reserve.

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 Point Conception, California: U.S. Geological Survey Open-File Report 2018–1024, pamphlet 36 p., 9 sheets, scale 1:24,000, https://doi.org/10.3133/ofr20181024.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

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

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title California State Waters Map Series — Offshore of Point Conception, California
Series title Open-File Report
Series number 2018-1024
DOI 10.3133/ofr20181024
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, 36 p.; 9 Sheets: 55.0 x 36.0 inches or smaller; Data Catalog; Metadata
Country United States
State California
Other Geospatial Point Conception
Additional Online Files (Y/N) Y