Geology and geomorphology--Offshore of Bodega Head Map Area, California

Map unit polygons were digitized over underlying 2-meter base layers developed from multibeam bathymetry and backscatter data. Derivatives such as slope and curvature were generated from source rasters. Interpreted rasters include amplitude, hillshaded bathymetry (using various illumination angles and vertical exaggeration), slope, and curvature. Curvature was decomposed into profile and plan curvature for analysis purposes.

The mapped area was extended to the shoreline by using digital orthophotos to interpret the region between the inner edge of the multibeam bathymetry and the approximate shoreline. The approximate shoreline was generated at the NAVD88 +1.46 m contour, defined as the operational MHW shoreline by Weber and others (2005). The resulting boundary was transformed to WGS 84 UTM Zone 10 North in ArcGIS 10 using the NAD83 to WGS84 (ITRF00) transformation algorithm. This boundary was then used to extend and trim both onshore and offshore geology in the print and PDF product. The transformed boundary is contained within the WGS84 "contours" feature class and identified as a water boundary in the associated representation rules. Only data for offshore map units are released digitally in this publication. For onshore geology see Blake and others (2002) and Wagner and Gutierrez (2010, and 2017). Quaternary mapping units are as defined by Witter and others (2006) and Wagner and Gutierrez (2010), with unit contacts modified based on analysis of 2003 LiDAR and 2004 IfSAR and data; and additional unpublished mapping by M.W. Manson. San Andreas Fault traces are from Brown and Wolfe (1972), California Geological Survey (1974) and previously unpublished mapping by M.W. Manson. References Cited: Blake, M.C., Jr., Graymer, R.W., and Stamski, R.E., 2002, Geologic map and map database of western Sonoma, northernmost Marin, and southernmost Mendocino counties, California: U.S. Geological Survey Miscellaneous Field Studies Map 2402, scale 1:100,000. Brown, R.D., Jr., and Wolfe, E.W., 1972, Map showing recently active breaks along the San Andreas Fault between Point Delgada and Bolinas Bay, California: U.S. Geological Survey Miscellaneous Investigations Map I-692, scale 1:24,000. California Geological Survey, 1974, Alquist-Priolo Earthquake Fault Zone Maps of Bodega Head, Duncans Mills and Valley Ford quadrangles, scale 1:24,000. Fuller, M.S., Haydon, W.D., Purcell, M.G., and Custis, K., 2002, Geologic and geomorphic features related to landsliding, Gualala River watershed, Sonoma and Mendocino counties, California: California Geological Survey Watershed Mapping Series, Map Set 5, Plate 1, Sheet 3 of 3, scale 1:24,000. Manson, M.W., Huyette, C.M., Wills, C.J., Huffman, M.E., Smelser, G.G., Fuller, M.E., Domrose, C., and Gutierrez, C., 2006, Landslides in the Highway 1 corridor between Bodega Bay and Fort Ross, Sonoma County, California: California Geological Survey Special Report 196, 26 p., 2 plates, 38 maps, scale 1:12,000. Wagner, D.L., and Gutierrez, C.I., 2010, Preliminary Geologic Map of the Napa 30' x 60' Quadrangle, California: California Geological Survey, scale 1:100,000. Wagner, D.L., and Gutierrez, C.I., 2017, Preliminary Geologic Map of the Bodega Bay 30' x 60' Quadrangle, California: California Geological Survey, scale 1:100,000. Weber, K.M., List, J.H., and Morgan, K.L., 2005, An operational Mean High Water datum for determination of shoreline position from topographic lidar data: U.S. Geological Survey Open-File Report 2005-1027, accessed April 5, 2011, at http://pubs.usgs.gov/of/2005/1027/. Witter, R.C., Knudsen, K.L., Sowers, J.M., Wentworth, C.M., Koehler, R.D., Randolph, C.E., Brooks, S.K., and Gans, K.D., 2006, Maps of Quaternary Deposits and Liquefaction Susceptibility in the Central San Francisco Bay Region, California, U.S. Geological Survey Open-File Report 06-1037, scale 1:24,000.

Added Distribution_Information section to metadata to facilitate data download.

Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog.

Added keywords from Coastal and Marine Ecological Classification Standard (CMECS) to metadata.

Edited metadata to add keywords section with USGS persistent identifier as theme keyword. No data were changed.

Edited metadata to fix validation errors and to bring it up to FGDC CSDGM current standards based on data release policies for USGS Coastal and Marine Hazards and Resources Program (CMHRP). No data were changed. The metadata available from a harvester may supersede metadata bundled within a download file. Users are advised to compare the metadata dates to determine which metadata file is most recent.