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California State Waters map series — Offshore of Pigeon Point, California

Open-File Report 2015-1232
By: , , , , , , , , , , , , , , , , and 
Edited by: Guy R. Cochrane and Susan A. Cochran
https://doi.org/10.3133/ofr20151232

Links

  • Document: Pamphlet (pdf)
  • Sheets:
    • Sheet 1 (pdf) Colored Shaded-Relief Bathymetry, Offshore of Pigeon Point Map Area, California By Peter Dartnell, Rikk G. Kvitek, Andrew C. Ritchie, and David P. Finlayson
    • Sheet 2 (pdf) Shaded-Relief Bathymetry, Offshore of Pigeon Point Map Area, California By Peter Dartnell, Rikk G. Kvitek, Andrew C. Ritchie, and David P. Finlayson
    • Sheet 3 (pdf) Acoustic Backscatter, Offshore of Pigeon Point Map Area, California By Peter Dartnell, Rikk G. Kvitek, Andrew C. Ritchie, and David P. Finlayson
    • Sheet 4 (pdf) Data Integration and Visualization, Offshore of Pigeon Point Map Area, California By Peter Dartnell
    • Sheet 5 (pdf) Seafloor Character, Offshore of Pigeon Point Map Area, California By Mercedes D. Erdey and Guy R. Cochrane
    • Sheet 6 (pdf) Ground-Truth Studies, Offshore of Pigeon Point Map Area, California By Nadine E. Golden, Guy R. Cochrane, and Lisa M. Krigsman
    • Sheet 7 (pdf) Potential Marine Benthic Habitats, Offshore of Pigeon Point Map Area, California By Charles A. Endris, H. Gary Greene, Bryan E. Dieter, and Mercedes D. Erdey
    • Sheet 8 (pdf) Seismic-Reflection Profiles, Offshore of Pigeon Point Map Area, California By Janet T. Watt, Samuel Y. Johnson, and Ray W. Sliter
    • Sheet 9 (pdf) Local (Offshore of Pigeon Point Map Area) and Regional (Offshore from Pigeon Point to Southern Monterey Bay) Shallow-Subsurface Geology and Structure, California By Janet T. Watt, Samuel Y. Johnson, Stephen R. Hartwell, Ray W. Sliter, and Katherine L. Maier
    • Sheet 10 (pdf) Offshore and Onshore Geology and Geomorphology, Offshore of Pigeon Point Map Area, California By Janet T. Watt, Stephen R. Hartwell, and Clifton W. Davenport
  • Related Works:
  • Dataset: Data Catalog (html) The GIS data layers for this map are accessible from “Data Catalog—Offshore Pigeon Point, 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.
  • Data Release: USGS data release - California State Waters Map Series Data Catalog--Offshore of Pigeon Point, California
  • 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 Pigeon Point map area is located in central California, on the Pacific Coast about 50 km south of San Francisco and 25 km northwest of Santa Cruz. The onshore part of the map area is sparsely populated. The nearest significant onshore cultural center is Pescadero, an unincorporated community with a population of well under 1,000. The hilly coastal area is virtually undeveloped, used primarily for agricultural or as grazing land for sheep and cattle. Agriculture is limited to the coastal uplifted Pleistocene marine terraces and upper Pleistocene alluvial fan deposits, which lie between the shoreline and the northwest-trending Santa Cruz Mountains.

The map area is cut by the San Gregorio Fault Zone, and is located a few kilometers southwest of the San Andreas Fault Zone. Coastal uplift and folding in the map area has been attributed to a westward bend in the San Andreas Fault Zone and also to right-lateral movement along the San Gregorio Fault Zone. The irregular coastal geomorphology of this area, which consists of low, rocky cliffs and sparse, small pocket beaches backed by low, terraced hills, is partly attributable to this ongoing deformation.

The shelf in the map area is underlain by variable amounts (0 to 20 m) of upper Quaternary nearshore and shelf sediments deposited as sea level fluctuated in the late Pleistocene. The southern part of the map is characterized by the presence of uplifted bedrock that has been linked to a local zone of transpression in the San Gregorio Fault Zone. This uplift, coupled with high wave energy, has resulted in little or no sediment cover in this area where exposures of bedrock are present at water depths of as much as 45 m. The thickest deposits of sediment are located in the northern part of the map area.

Coastal sediment transport in the map area is characterized by north-to-south littoral transport of sediment that is derived mainly from streams in the Santa Cruz Mountains and also from local coastal erosion. Shoreline-change studies indicate long-term erosion; within the region between San Francisco and Davenport, the highest long- and short-term coastal-erosion rates occur in the map area, just north of Point Año Nuevo. During the last approximately 300 years, as much as 18 million cubic yards (14 million cubic meters) of sand-sized sediment has been eroded from the area between Año Nuevo Island and Point Año Nuevo and transported south. Once widened by this pulse of eroded sediment, beaches south of Point Año Nuevo are now narrowing as the tail end of this mass of sand progresses farther south.

The Offshore of Pigeon Point map area lies within the cold-temperate biogeographic zone that is called 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, the eastern limb of the North Pacific subtropical gyre that flows from southern British Columbia 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 335 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 of central California has experienced a warming over the last 50 years that is driving an ecosystem shift away from the productive subarctic regime towards a depopulated subtropical environment.

Seafloor habitats in the Offshore of Pigeon Point map area lie within the Shelf (continental shelf) megahabitat. Significant rocky outcrops, which support kelp-forest communities in the nearshore and rocky-reef communities in deeper water, dominate the inner shelf waters. 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 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 rockfish and greenling.

Suggested Citation

Cochrane, G.R., Watt, J.T., Dartnell, P., Greene, H.G., Erdey, M.D., Dieter, B.E., Golden, N.E., Johnson, S.Y., Endris, C.A., Hartwell, S.R., Kvitek, R.G., Davenport, C.W., Krigsman, L.M., Ritchie, A.C., Sliter, R.W., Finlayson, D.P., and Maier, K.L. (G.R. Cochrane and S.A. Cochran, eds.), 2015, California State Waters Map Series — Offshore of Pigeon Point, California: U.S. Geological Survey Open-File Report 2015–1232, pamphlet 40 p., 10 sheets, scale 1:24,000, http://dx.doi.org/10.3133/ofr20151232.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Chapter 1. Introduction
  • Chapter 2. Bathymetry and Backscatter-Intensity Maps of the Offshore of Pigeon Point Map Area
  • Chapter 3. Data Integration and Visualization for the Offshore of Pigeon Point Map Area
  • Chapter 4. Seafloor-Character Map of the Offshore of Pigeon Point Map Area
  • Chapter 5. Ground-Truth Studies for the Offshore of Pigeon Point Map Area
  • Chapter 6. Potential Marine Benthic Habitats of the Offshore of Pigeon Point Map Area
  • Chapter 7. Subsurface Geology and Structure of the Offshore of Pigeon Point Map Area and the Pigeon Point to Southern Monterey Bay Region
  • Chapter 8. Geologic and Geomorphic Map of the Offshore of Pigeon Point Map Area

 

Publication type Report
Publication Subtype USGS Numbered Series
Title California State Waters map series — Offshore of Pigeon Point, California
Series title Open-File Report
Series number 2015-1232
DOI 10.3133/ofr20151232
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, 40 p.; 10 Sheets: 50.50 x 36.00 inches or smaller; Data Catalog; Metadata
Country United States
State California
Other Geospatial Pigeon Point
Scale 24000
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details