Description: This part of DS 781 presents data for the bathymetric contours for several seafloor maps of the Offshore Pigeon Point map area, California. The vector data file is included in "Contours_OffshorePigeonPoint.zip", which is accessible from http://dx.doi.org/10.5066/F7513W80.
10-m interval contours of the Offshore Pigeon Point map area, California, were generated from bathymetry data collected by the U.S. Geological Survey (USGS) and by California State University, Monterey Bay (CSUMB). Mapping was completed between 2006 and 2009 using a combination of a 244-kHz Reson 8101 multibeam echosounder and a 234-kHz SEA SWATHplus bathymetric sidescan-sonar system. The mapping missions collected bathymetry data from about the 10-m isobath to beyond the 3-nautical-mile limit of California’s State Waters.
Bathymetric contours at 10-m intervals were generated from a modified 2-m bathymetric surface. The original surface was smoothed using the Focal Mean tool in ArcGIS and a circular neighborhood with a radius of 20 to 30 meters (depending on the area). The contours were generated from this smoothed surface using the ArcGIS Spatial Analyst Contour tool. The most continuous contour segments were preserved while smaller segments and isolated island polygons were excluded from the final output. The contours were then clipped to the boundary of the map area.
Description: This part of DS 781 presents data for the faults for the geologic and geomorphic map of the Offshore Pigeon Point map area, California. The vector data file is included in "Faults_OffshorePigeonPoint.zip," which is accessible from http://dx.doi.org/10.5066/F7513W80
The offshore Pigeon Point map area lies about 15 to 25 km southwest of the San Andreas Fault, the dominant structure in the distributed transform boundary between the North American and Pacific plates. The map area straddles the right-lateral Pigeon Point Fault zone, a prominent structure west of the San Andreas Fault in the broader San Andreas Fault system. The Pigeon Point Fault zone occurs predominantly in the offshore and extends 400 km from Point Conception on the south to Bolinas and Point Reyes on the north (Dickinson and others, 2005), coming onland at coastal promontories such as Pescadero Point in the map area and Pillar Point, a few km north of Half Moon Bay.
In the offshore, the Pigeon Point Fault system forms a distributed shear zone about 2 to 4 km wide that includes two main diverging fault strands. The western strand (also known as the Frijoles Fault) extends offshore from Pescadero Point. The eastern strand (also known as the Coastways Fault or Seal Cove Fault), is mostly onshore in this map area. Cumulative lateral slip on the Pigeon Point Fault zone is thought to range from 4 to 10 mm/yr in this region (U.S. Geological Survey, 2010). The western strand of the Pigeon Point Fault zone (i.e., Frijoles Fault) forms the eastern boundary of the Pigeon Point high.
Faults were primarily mapped by interpretation of seismic reflection profile data (see OFR 2013-1071). The seismic reflection profiles were collected between 2007 and 2010.
References Cited
Dickinson, W.R., Ducea, M., Rosenberg, L.I., Greene, H.G., Graham, S.A., Clark, J.C., Weber, G.E., Kidder, S., Ernst, W.G., and Brabb, E.E., 2005, Net dextral slip, Neogene Pigeon Point-Hosgri fault zone, coastal California: Geologic evidence and tectonic implications: Geological Society of America Special Paper 391, 43 p.
Description: This part of DS 781 presents data for the folds for the geologic and geomorphic map of the Offshore Pigeon Point map area, California. The vector data file is included in "Folds_OffshorePigeonPoint.zip," which is accessible from http://dx.doi.org/10.5066/F7513W80
The offshore Pigeon Point map area lies about 15 to 25 km southwest of the San Andreas Fault, the dominant structure in the distributed transform boundary between the North American and Pacific plates. The map area straddles the right-lateral Pigeon Point Fault zone, a prominent structure west of the San Andreas Fault in the broader San Andreas Fault system. The Pigeon Point Fault zone occurs predominantly in the offshore and extends 400 km from Point Conception on the south to Bolinas and Point Reyes on the north (Dickinson and others, 2005), coming onland at coastal promontories such as Pescadero Point in the map area and Pillar Point, a few km north of Half Moon Bay.
In the offshore, the Pigeon Point Fault system forms a distributed shear zone about 2 to 4 km wide that includes two main diverging fault strands. The western strand (also known as the Frijoles Fault) extends offshore from Pescadero Point. The eastern strand (also known as the Coastways Fault or Seal Cove Fault), is mostly onshore in this map area. Cumulative lateral slip on the Pigeon Point Fault zone is thought to range from 4 to 10 mm/yr in this region (U.S. Geological Survey, 2010). The western strand of the Pigeon Point Fault zone (i.e., Frijoles Fault) forms the eastern boundary of the Pigeon Point high.
Folds were primarily mapped by interpretation of seismic reflection profile data (see OFR 2013-1071). The seismic reflection profiles were collected between 2007 and 2010.
References Cited
Dickinson, W.R., Ducea, M., Rosenberg, L.I., Greene, H.G., Graham, S.A., Clark, J.C., Weber, G.E., Kidder, S., Ernst, W.G., and Brabb, E.E., 2005, Net dextral slip, Neogene Pigeon Point-Hosgri fault zone, coastal California: Geologic evidence and tectonic implications: Geological Society of America Special Paper 391, 43 p.
Description: This part of DS 781 presents data for the geologic and geomorphic map of the Offshore Pigeon Point map area, California. The vector data file is included in "Geology_OffshorePigeonPoint.zip," which is accessible from http://dx.doi.org/10.5066/F7513W80
The continental shelf within California's State waters in the Pigeon Point map area is shallow (0 to ~55 m) and flat with a very gentle (less than 0.5 degrees) offshore dip. Shelf morphology and evolution result from the interplay between local tectonics and sedimentation as sea level rose about 125 to 130 m over the last ~ 21,000 years (Lambeck and Chappel, 2001). Shelf deposits are almost exclusively sand (unit Qms) at depths less than 60 m and transition to more fine grained, muddy sediment (unit Qmsf) at greater depths in the southwestern most part of the map area. The boundary between units Qms and Qmsf was determined based on seafloor sediment samples (Reid and others, 2006) and video observations from the Offshore of Pigeon Point and adjacent map area. This boundary likely shifts seaward or landward based on seasonal to decadal changes in sediment supply, sediment transport, and wave climate.
More coarse-grained sands and gravels (units Qmss and Qmsc) are primarily recognized on the basis of high backscatter. Unit Qmsc occurs as a nearshore, shore-parallel bar at typical water depths between 5 and 10 meters. Unit Qmss forms erosional lags in rippled scour depressions (for example, Cacchione and others, 1984) at water depths of about 25 to 35 m, in contact with offshore bedrock uplifts and unit Qms. Although the general areas in which unit Qmsc and unit Qmss occur are not likely to change substantially, the boundaries of the unit(s) are likely ephemeral, changing seasonally and during significant storm events. Unit Qmss deposits are common along this stretch of the California coast where offshore sandy sediment can be relatively thin (thus unable to fill the depressions) due to both lack of river input and to significant sediment erosion and offshore sediment transport during large northwest winter swells.
Areas where shelf sediments form thin (< 2.5 m or less) veneers over low relief, undivided Cretaceous and (or) Tertiary bedrock are mapped as units Qms/TKu and Qms/Tp. These areas are recognized based on the combination of flat relief, continuity with moderate to high relief bedrock outcrops, high-resolution seismic-reflection data, and in some cases moderate backscatter. These units are regarded as ephemeral and dynamic sediment layers that may or may not be present based on storms, seasonal/annual patterns of sediment movement, or climate cycles.
Tertiary deposits mapped in the offshore include two units of the Purisima Formation (units Tp and Tpt). The Purisima units are characterized by high backscatter and distinct bedding recognized in multibeam imagery and/or seismic-reflection data. These Tertiary rocks are underlain by or in fault contact with Upper Cretaceous basement rocks, including sedimentary rocks of the Pigeon Point Formation (unit Kpp). The Pigeon Point Formation is mapped on the basis of high backscatter, massive and (or) rugged texture on multibeam imagery, and reflection-free character on seismic-reflection data. Offshore outcrops of the Pigeon Point Formation form the offshore Pigeon Point high, a major structural feature that extends ~30 km to the northwest and represents the northeast boundary of the Outer Santa Cruz Basin (McCulloch, 1987). Areas where bedrock is exposed on the seafloor but there is less certainty regarding age are mapped as Cretaceous and Tertiary, undivided (unit TKu).
Map unit polygons were digitized over underlying 2-meter base layers developed from multibeam bathymetry and backscatter data (see "Bathymetry--Offshore of Pigeon Point Map Area, California" and "Backscatter--Offshore of Pigeon Point Map Area, California"). The bathymetry and backscatter data were collected between 2006 and 2010.
References Cited
Cacchione, D.A., Drake, D.E., Grant, W.D., and Tate, G.B., 1984. Rippled scour depressions of the inner continental shelf off central California: Journal of Sedimentary Petrology, v 54, p. 1280-1291.
Lambeck, K., and Chappell, J., 2001, Sea level change through the last glacial cycle: Science, v. 292, p. 679-686.
McCulloch, D.S., 1987, Regional geology and hydrocarbon potential of offshore Central California, in Scholl, D.W., Grantz, A., and Vedder, J.G., eds., Geology and resource potential of the continental margin of Western North America and adjacent ocean basins - Beaufort Sea to Baja California: Circum-Pacific Council for Energy and Mineral Resources Earth Science Series, v. 6, p. 353-401.
Reid, J.A., Reid, J.M., Jenkins, C.J., Zimmerman, M., Williams, S.J., and Field, M.E., 2006, usSEABED: Pacific Coast (California Oregon, Washington) offshore surficial-sediment data release: U.S. Geological Survey Data Series 182, http://pubs.usgs.gov/ds/2006/182/.
Description: This part of DS 781 presents data for the habitat map of the seafloor of the Offshore of Pigeon Point map area, California. The vector data file is included in "Habitat_OffshorePigeonPoint.zip," which is accessible from http://dx.doi.org/10.5066/F7513W80
Using multibeam echosounder (MBES) bathymetry and backscatter data, potential marine benthic habitat maps were constructed. The habitats were based on substrate types and documented or "ground truthed" using underwater video images and seafloor samples obtained by the USGS. These maps display various habitat types that range from flat, soft, unconsolidated sediment-covered seafloor to hard, deformed (folded), or highly rugose and differentially eroded bedrock exposures. Rugged, high-relief, rocky outcrops that have been eroded to form ledges and small caves are ideal habitat for rockfish (Sebastes spp.) and other bottom fish such as lingcod (Ophiodon elongatus). Habitat map is presented in a map format generated in a GIS (ArcMap), and both digital and hard-copy versions will be produced.
Please refer to Greene and others (2007) for more information regarding the Benthic Marine Potential Habitat Classification Scheme and the codes used to represent various seafloor features.
References Cited:
Greene, H.G., Bizzarro, J.J., O'Connell, V.M., and Brylinsky, C.K., 2007, Construction of digital potential marine benthic habitat maps using a coded classification scheme and its application, in Todd, B.J., and Greene, H.G., eds., Mapping the seafloor for habitat characterization: Geological Association of Canada Special Paper 47, p. 141-155.
Description: This part of DS 781 presents the seafloor-character map Offshore of Pigeon Point, California. The raster data file is included in "SeafloorCharacter_OffshorePigeonPoint.zip," which is accessible from http://dx.doi.org/10.5066/F7513W80
This raster-format seafloor character map shows four substrate classes Offshore of Pigeon Point, California. The substrate classes mapped in this area have been further divided into the following California Marine Life Protection Act depth zones and slope classes: Depth Zone 2 (intertidal to 30 m), Depth Zone 3 (30 to 100 m), Slope Class 1 (0 degrees - 5 degrees), and Slope Class 2 (5 degrees - 30 degrees). Depth Zone 1 (intertidal), Depth Zones 4-5 (greater than 100 m), and Slopes Classes 3-4 (greater than 30 degrees) are not present in the region covered by this block. The map is created using a supervised classification method described by Cochrane (2008), available at http://doc.nprb.org/web/research/research%20pubs/615_habitat_mapping_workshop/Individual%20Chapters%20High-Res/Ch13%20Cochrane.pdf.
References Cited:
California Department of Fish and Game, 2008, California Marine Life Protection Act master plan for marine protected areas; Revised draft: California Department of Fish and Game, accessed April 5 2011, at http://www.dfg.ca.gov/mlpa/masterplan.asp.
Cochrane, G.R., 2008, Video-supervised classification of sonar data for mapping seafloor habitat, in Reynolds, J.R., and Greene, H.G., eds., Marine habitat mapping technology for Alaska: Fairbanks, University of Alaska, Alaska Sea Grant College Program, p. 185-194, accessed April 5, 2011, at http://doc.nprb.org/web/research/research%20pubs/615_habitat_mapping_workshop/Individual%20Chapters%20High-Res/Ch13%20Cochrane.pdf.
Sappington, J.M., Longshore, K.M., and Thompson, D.B., 2007, Quantifying landscape ruggedness for animal habitat analysis--A case study using bighorn sheep in the Mojave Desert: Journal of Wildlife Management, v. 71, p. 1419-1426.
Description: This part of DS 781 presents data for the bathymetry and shaded-relief maps of Offshore Pigeon Point, California. The raster data file is included in "BathymetryHS_OffshorePigeonPoint.zip", which is accessible from http://dx.doi.org/10.5066/F7513W80
The bathymetry and shaded-relief maps of Offshore Pigeon Point, California, were generated from bathymetry data collected by California State University, Monterey Bay (CSUMB), by Fugro Pelagos, and by the U.S. Geological Survey (USGS). Mapping was completed between 2006 and 2009, using a combination of 400-kHz Reson 7125 and 244-kHz Reson 8101 multibeam echosounders, as well as a 234-kHz SWATHplus bathymetric sidescan-sonar system. These mapping missions combined to collect bathymetry from about the 10-m isobath to beyond the 3-nautical-mile limit of California’s State Waters.
Description: This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Pigeon Point map area, California. Backscatter data are provided as three separate grids depending on mapping system. The raster data files are included in "BackscatterA_8101_OffshorePigeonPoint.zip," which is accessible from http://dx.doi.org/10.5066/F7513W80
The acoustic-backscatter map of the Offshore of Pigeon Point, California was generated from backscatter data collected by California State University, Monterey Bay (CSUMB), by Fugro Pelagos, and by the U.S. Geological Survey (USGS). Mapping was completed between 2006 and 2009, using a combination of 400-kHz Reson 7125 and 244-kHz Reson 8101 multibeam echosounders, as well as a 234-kHz SWATHplus bathymetric sidescan-sonar system. Within the final imagery, brighter tones indicate higher backscatter intensity, and darker tones indicate lower backscatter intensity. The intensity represents a complex interaction between the acoustic pulse and the seafloor, as well as characteristics within the shallow subsurface, providing a general indication of seafloor texture and composition. Backscatter intensity depends on the acoustic source level; the frequency used to image the seafloor; the grazing angle; the composition and character of the seafloor, including grain size, water content, bulk density, and seafloor roughness; and some biological cover. Harder and rougher bottom types such as rocky outcrops or coarse sediment typically return stronger intensities (high backscatter, lighter tones), whereas softer bottom types such as fine sediment return weaker intensities (low backscatter, darker tones).
Description: This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Pigeon Point map area, California. Backscatter data are provided as three separate grids depending on mapping system. The raster data files are included in "BackscatterB_7125_OffshorePigeonPoint.zip," which is accessible from http://dx.doi.org/10.5066/F7513W80
The acoustic-backscatter map of the Offshore of Pigeon Point, California was generated from backscatter data collected by California State University, Monterey Bay (CSUMB), by Fugro Pelagos, and by the U.S. Geological Survey (USGS). Mapping was completed between 2006 and 2009, using a combination of 400-kHz Reson 7125 and 244-kHz Reson 8101 multibeam echosounders, as well as a 234-kHz SWATHplus bathymetric sidescan-sonar system. Within the final imagery, brighter tones indicate higher backscatter intensity, and darker tones indicate lower backscatter intensity. The intensity represents a complex interaction between the acoustic pulse and the seafloor, as well as characteristics within the shallow subsurface, providing a general indication of seafloor texture and composition. Backscatter intensity depends on the acoustic source level; the frequency used to image the seafloor; the grazing angle; the composition and character of the seafloor, including grain size, water content, bulk density, and seafloor roughness; and some biological cover. Harder and rougher bottom types such as rocky outcrops or coarse sediment typically return stronger intensities (high backscatter, lighter tones), whereas softer bottom types such as fine sediment return weaker intensities (low backscatter, darker tones).
Description: This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Pigeon Point map area, California. Backscatter data are provided as three separate grids depending on mapping system. The raster data files are included in "BackscatterC_SWATH_OffshorePigeonPoint.zip," which is accessible from http://dx.doi.org/10.5066/F7513W80
The acoustic-backscatter map of the Offshore of Pigeon Point, California was generated from backscatter data collected by California State University, Monterey Bay (CSUMB), by Fugro Pelagos, and by the U.S. Geological Survey (USGS). Mapping was completed between 2006 and 2009, using a combination of 400-kHz Reson 7125 and 244-kHz Reson 8101 multibeam echosounders, as well as a 234-kHz SWATHplus bathymetric sidescan-sonar system. Within the final imagery, brighter tones indicate higher backscatter intensity, and darker tones indicate lower backscatter intensity. The intensity represents a complex interaction between the acoustic pulse and the seafloor, as well as characteristics within the shallow subsurface, providing a general indication of seafloor texture and composition. Backscatter intensity depends on the acoustic source level; the frequency used to image the seafloor; the grazing angle; the composition and character of the seafloor, including grain size, water content, bulk density, and seafloor roughness; and some biological cover. Harder and rougher bottom types such as rocky outcrops or coarse sediment typically return stronger intensities (high backscatter, lighter tones), whereas softer bottom types such as fine sediment return weaker intensities (low backscatter, darker tones).
Description: This part of DS 781 presents data for the bathymetry and shaded-relief maps of Offshore Pigeon Point, California. The raster data file is included in "Bathymetry_OffshorePigeonPoint.zip", which is accessible from http://dx.doi.org/10.5066/F7513W80
The bathymetry and shaded-relief maps of Offshore Pigeon Point, California, were generated from bathymetry data collected by California State University, Monterey Bay (CSUMB), by Fugro Pelagos, and by the U.S. Geological Survey (USGS). Mapping was completed between 2006 and 2009, using a combination of 400-kHz Reson 7125 and 244-kHz Reson 8101 multibeam echosounders, as well as a 234-kHz SWATHplus bathymetric sidescan-sonar system. These mapping missions combined to collect bathymetry from about the 10-m isobath to beyond the 3-nautical-mile limit of California’s State Waters. NOTE: The horizontal datum of this bathymetry data (NAD83) differs from the horizontal datum of other layers in this SIM (WGS84). Some bathymetry grids within this map area were projected horizontally from WGS84 to NAD83 using ESRI tools to be more consistent with the vertical reference of the North American Vertical Datum of 1988 (NAVD88).