thumbnail

California State Waters Map Series — Offshore of Bolinas, California

Open-File Report 2015-1135
By: , , , , , , , , , , , , , , , and 
Edited by: Guy R. Cochrane and Susan A. Cochran
https://doi.org/10.3133/ofr20151135

Links

  • Document: Pamphlet (pdf)
  • Sheets:
    • Sheet 1 (pdf) Colored Shaded-Relief Bathymetry, Offshore of Bolinas Map Area, California By Peter Dartnell, Rikk G. Kvitek, and Carrie K. Bretz
    • Sheet 2 (pdf) Shaded-Relief Bathymetry, Offshore of Bolinas Map Area, California By Peter Dartnell, Rikk G. Kvitek, and Carrie K. Bretz
    • Sheet 3 (pdf) Acoustic Backscatter, Offshore of Bolinas Map Area, California By Peter Dartnell, Rikk G. Kvitek, Mercedes D. Erdey, and Carrie K. Bretz
    • Sheet 4 (pdf) Data Integration and Visualization, Offshore of Bolinas Map Area, California By Peter Dartnell
    • Sheet 5 (pdf) Seafloor Character, Offshore of Bolinas Map Area, California By Mercedes D. Erdey and Guy R. Cochrane
    • Sheet 6 (pdf) Ground-Truth Studies, Offshore of Bolinas Map Area, California By Nadine E. Golden, Guy R. Cochrane, and Mercedes D. Erdey
    • Sheet 7 (pdf) Potential Marine Benthic Habitats, Offshore of Bolinas Map Area, California By Bryan E. Dieter, H. Gary Greene, Charles A. Endris, and Mercedes D. Erdey
    • Sheet 8 (pdf) Seismic-Reflection Profiles, Offshore of Bolinas Map Area, California by Samuel Y. Johnson, Ray W. Sliter, Terry R. Bruns, and John L. Chin
    • Sheet 9 (pdf) Local (Offshore of Bolinas Map Area) and Regional (Offshore from Bolinas to Pescadero) Shallow-Subsurface Geology and Structure, California By Samuel Y. Johnson, Stephen R. Hartwell, Ray W. Sliter, Janet T. Watt, Eleyne L. Phillips, Stephanie L. Ross, and John L. Chin
    • Sheet 10 (pdf) Offshore and Onshore Geology and Geomorphology, Offshore of Bolinas Map Area, California By Samuel Y. Johnson, H. Gary Greene, Michael W. Manson, Stephen R. Hartwell, Charles A. Endris, and Janet T. Watt
  • Related Works:
  • Dataset: Data Catalog (html) The GIS data layers for this map are accessible from “Data Catalog—Offshore of Bolinas, 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 (html)
  • NGMDB Index Page: National Geologic Map Database 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 Offshore of Bolinas map area is located in northern California, on the Pacific Coast of Marin County about 10 kilometers north of the Golden Gate. The town of Bolinas, named after a local indigenous tribe, is the largest population center along this section of coast, with a population of approximately 1,600 people. Bolinas is situated at the end of a southeast-trending terrain on the west side of the San Andreas Fault that also protects a natural harbor. The harbor lies in Bolinas Lagoon, which is separated from Bolinas Bay by a spit. The coastal lands within the Offshore of Bolinas map area lie entirely within the Point Reyes National Seashore, which limits development and allows existing ranching and farming to continue.

The Offshore of Bolinas map area lies offshore of the northwest-trending Coast Ranges, which lie east of, and are roughly parallel to, the San Andreas Fault Zone. The western margin of North America is the only continental margin in the world delineated largely by transform faults such as the San Andreas Fault. The coastal geomorphology is controlled by late Pleistocene to Holocene slip along the fault. Bolinas Bay and Lagoon have formed where a regional depression along the fault zone intersects the coast. A northward bend in the San Andreas Fault to the north, combined with right-lateral movement, has caused regional extension and the formation of a sediment basin on the continental shelf in, and southeast of, Bolinas Bay.

With the exception of the area adjacent to Bolinas Bay, the coast in the map area consists of high coastal bluffs and vertical sea cliffs. The uplifted headland upon which the town of Bolinas is situated is part of a larger uplifted area that includes exposed bedrock offshore. Uplift in this map area has resulted in relatively shallow depths within California’s State Waters (0 to 40 m) and, thus, little accommodation space for sediment accumulation. Sediment is found in the extensional basin southeast of Bolinas, as well as on the shelf offshore of uplifted coastal areas, where, within California’s State Waters, depths can exceed 40 m. Wave energy keeps the uplifted bedrock areas clear of sediment, and rippled sediment in the outer shelf indicates some mobility.

Coastal sediment transport in the Offshore of Bolinas map area is characterized by north-to-south littoral transport of sediment that is derived mainly from ephemeral streams and local coastal erosion. Beyond California’s State Waters, canyons that incise the slope have been disconnected from coastal streams by rising sea level, which has risen about 125 m since the lowstand associated with the Last Glacial Maximum about 18,000 to 20,000 years ago. In the map area, no major submarine canyons extend up past the shelf break and into the nearshore to receive littoral drift. The coastline in the map area is characterized as high risk because of its steep cliffs and large-scale landsliding. The sand spit that separates Bolinas Lagoon from Bolinas Bay is highly developed, and its homes are at risk during storms, especially those from the south.

The benthic species observed in the Offshore of Bolinas map area are natives of the cold-temperate biogeographic zone named either the “Oregonian province” or the “northern California ecoregion.” This biogeographic province is maintained by the long-term stability of the southward-flowing California Current, an eastern limb of the North Pacific subtropical gyre that flows from Oregon to Baja California. At its midpoint off central California, the California Current transports subarctic surface (0–500 m deep) waters southward, about 150 to 1,300 km from shore. Seasonal northwesterly winds that are, in part, responsible for the California Current, generate coastal upwelling. The south end of the Oregonian province is at Point Conception (about 425 km south of the map area), although its associated phylogeographic group of marine fauna may extend beyond to the area offshore of Los Angeles in southern California. The ocean off central California has seen a warming over the last 50 years that is driving an ecosystem shift from the productive subarctic regime towards a depopulated subtropical environment.

Seafloor habitats in the Offshore of Bolinas map area, which lies within the Shelf (continental shelf) megahabitat, range from, in the nearshore, sandy seafloor in the southeast and significant rocky outcrops that support kelp-forest communities in the northwest to, in deeper water, rocky-reef communities. Biological productivity resulting from coastal upwelling supports populations of Sooty Shearwater Western Gull, Common Murre, Cassin’s Auklet, and many other less populous bird species. In addition, an observable recovery of Humpback and Blue Whales has occurred in the area; both species are dependent on coastal upwelling to provide nutrients. The large extent of exposed inner shelf bedrock in the northeast supports large forests of “bull kelp,” which is well adapted for high wave-energy environments. Common fish species found in the kelp beds and rocky reefs include lingcod and various species of greenling and rockfish.

Suggested Citation

Cochrane, G.R., Dartnell, P., Johnson, S.Y., Greene, H.G., Erdey, M.D., Golden, N.E., Hartwell, S.R., Manson, M.W., Sliter, R.W., Endris, C.A., Watt, J.T., Ross, S.L., Kvitek, R.G., Phillips, E.L., Bruns, T.R., and Chin, J.L. (G.R. Cochrane and S.A. Cochran, eds.), 2015, California State Waters Map Series — Offshore of Bolinas, California: U.S. Geological Survey Open-File Report 2015–1135, pamphlet 36 p., 10 sheets, http://dx.doi.org/10.3133/ofr20151135.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

Chapters in Pamphlet:
  • Chapter 1. Introduction, By Guy R. Cochrane
  • Chapter 2. Bathymetry and Backscatter-Intensity Maps of the Offshore of Bolinas Map Area (Sheets 1, 2, and 3), By Peter Dartnell and Rikk G. Kvitek
  • Chapter 3. Data Integration and Visualization for the Offshore of Bolinas Map Area (Sheet 4), By Peter Dartnell 
  • Chapter 4. Seafloor-Character Map of the Offshore of Bolinas Map Area (Sheet 5), By Mercedes D. Erdey and Guy R. Cochrane 
  • Chapter 5. Ground-Truth Studies for the Offshore of Bolinas Map Area (Sheet 6), By Nadine E. Golden and Guy R. Cochrane 
  • Chapter 6. Potential Marine Benthic Habitats of the Offshore of Bolinas Map Area (Sheet 7), By H. Gary Greene and Charles A. Endris
  • Chapter 7. Subsurface Geology and Structure of the Offshore of Bolinas Map Area and the Bolinas to Pescadero Region (Sheets 8 and 9), By Samuel Y. Johnson, Stephen R. Hartwell, Ray W. Sliter, Janet T. Watt, and Stephanie L. Ross
  • Chapter 8. Geologic and Geomorphic Map of the Offshore of Bolinas Map Area (Sheet 10), By Samuel Y. Johnson, H. Gary Greene, Michael W. Manson, Charles A. Endris, Stephen R. Hartwell, and Janet T. Watt
Publication type Report
Publication Subtype USGS Numbered Series
Title California State Waters Map Series — Offshore of Bolinas, California
Series title Open-File Report
Series number 2015-1135
DOI 10.3133/ofr20151135
Year Published 2015
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Pacific Coastal and Marine Science Center
Description Report: iv, 36 p.; 10 Sheets: 46 inches x 36 inches or smaller; Data Catalog; Metadata
Country United States
State California
City Bolinas
Scale 24000
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details