California State Waters Map Series: offshore of San Francisco, California

Open-File Report 2015-1068
By: , and 
Edited by: Guy R. Cochrane and Susan A. Cochran

Links

  • More information: USGS Index Page
  • Document: Pamphlet (906 kB pdf)
  • Plates:
    • Sheet 1 (28.2 MB pdf) Colored Shaded-Relief Bathymetry, Offshore of San Francisco Map Area, California By Peter Dartnell, Rikk G. Kvitek, and Carrie K. Bretz
    • Sheet 2 (27.1 MB pdf) Shaded-Relief Bathymetry, Offshore of San Francisco Map Area, California By Peter Dartnell, Rikk G. Kvitek, and Carrie K. Bretz
    • Sheet 3 (28.2 MB pdf) Acoustic Backscatter, Offshore of San Francisco Map Area, California By Peter Dartnell, Mercedes D. Erdey, Rikk G. Kvitek, and Carrie K. Bretz
    • Sheet 4 (15.5 MB pdf) Data Integration and Visualization, Offshore of San Francisco Map Area, California By Peter Dartnell
    • Sheet 5 (39.3 MB pdf) Seafloor Character, Offshore of San Francisco Map Area, California By Mercedes D. Erdey and Guy R. Cochrane
    • Sheet 6 (29.6 MB pdf) Ground-Truth Studies, Offshore of San Francisco Map Area, California By Nadine E. Golden and Guy R. Cochrane
    • Sheet 7 (18.1 MB pdf) Potential Marine Benthic Habitats, Offshore of San Francisco Map Area, California By Charles A. Endris, H. Gary Greene, Bryan E. Dieter, and Mercedes D. Erdey
    • Sheet 8 (20.7 MB pdf) Seismic-Reflection Profiles, Offshore of San Francisco Map Area, California by Samuel Y. Johnson, Ray W. Sliter, Terry R. Bruns, Stephanie L. Ross, and John L. Chin
    • Sheet 9 (9.2 MB pdf) Local (Offshore of San Francisco 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 (14.2 MB pdf) Offshore and Onshore Geology and Geomorphology, Offshore of San Francisco Map Area, California By H. Gary Greene, Samuel Y. Johnson, Michael W. Manson, Stephen R. Hartwell, Charles A. Endris, and Terry R. Bruns
  • Metadata: Metadata
  • Spatial Data: Data Catalog: Offshore of San Francisco, California (Data Series 781) Each GIS data file is listed with a brief description, a small image, and links to the metadata files and the downloadable data files.
  • Open Access Version: Publisher Index Page
  • Download citation as: RIS | Dublin Core

Abstract

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 San Francisco map area is centered on the City of San Francisco and the Golden Gate channel, a waterway that connects the Pacific Ocean to the San Francisco Bay between the Marin Headlands and San Francisco Peninsula. The San Francisco Bay Area is the second-largest urban area on the U.S. West Coast with a combined population of over seven million. The bay supports several major cargo ports and the Port of San Francisco’s Fisherman’s Wharf is a major center for Northern California’s commercial and sport fishing fleets. The coastal part of the map area predominantly consists of high bluffs and vertical sea cliffs shaped by uplift and erosion of the Marin Headlands and San Francisco Peninsula east of the San Andreas and San Gregorio Fault Zones.

The seafloor in the map area extends from the shoreline and western end of the Golden Gate channel to water depths of about 30 to 50 m, except for the San Andreas graben area, where water depths reach 75 m. Sea-level rise, tidal currents, and tectonics have shaped bathymetry in the map area. During the Last Glacial Maximum, Sea level was about 125 m lower than present day and the shoreline was more than 45 km west of San Francisco near the Farallon Islands. At that time, the map area was part of a large alluvial plain connected to a drainage basin that included much of California’s Central Valley. A river system flowed westward through the narrows of the Golden Gate channel and an alluvial valley bounded to the north and south by bedrock highlands, including the present-day Pacifica-Pescadero and Bolinas shelves. Rising seas entered the Golden Gate about 11,000 to 10,000 years ago and subsequent marine flooding led to progressive growth of the San Francisco Bay. Strong tidal currents, accelerating through the relatively narrow Golden Gate, have scoured the bedrock channel to a depth of 113 m. East and west of the channel, tidal currents decelerate and form large fields of sand waves. Offshore of the Marin Headlands, eastward transfer of right-lateral fault slip in a complex of faults northwest of the map area has caused extension and the formation of a sediment basin called the San Andreas graben on the continental shelf. The accommodation space created by extension on the shelf and the proximity to sediment transported to the ocean through San Francisco Bay results in a sand-dominated offshore shelf environment.

Seafloor habitats in the Offshore of San Francisco map area comprise significant sand-dominated sediment habitat with sand wave and ripple bedforms indicative of high wave and current energy. North of the Golden Gate, 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. For the first time in 65 years, Pacific Harbor Porpoise returned to San Francisco Bay in 2009. On the coast north of the Golden Gate, the large extent of exposed inner shelf bedrock 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 painted greenling, kelp greenling, lingcod, and several varieties of rockfish.

Circulation over the continental shelf in the Offshore of San Francisco map area is dominated by the southward-flowing California Current, an eastern limb of the North Pacific Gyre that flows from Oregon to Baja California. At its midpoint offshore of central California, the California Current transports subarctic surface waters southeastward, about 150 to 1,300 km from shore. Seasonal northwesterly winds that are, in part, responsible for the California Current, generate coastal upwelling. Ocean temperatures offshore of central California have increased over the past 50 years, driving an ecosystem shift from the productive subarctic regime towards a depopulated subtropical environment.

Study Area

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title California State Waters Map Series: offshore of San Francisco, California
Series title Open-File Report
Series number 2015-1068
DOI 10.3133/ofr20151068
Year Published 2015
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Pacific Coastal and Marine Science Center
Description Pamphlet: iv, 39 p.; 10 Sheets: 52.0 x 36.0 inches or smaller; Metadata; Data catalog
Country United States
State California
City San Francisco
Other Geospatial Golden Gate channel
Projection Universal Transverse Mercator projection, Zone 10N
Scale 24000
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page