Folds--Offshore of Monterey Map Area, California

This part of DS 781 presents data for the folds for the geologic and geomorphic map of the Offshore Monterey map area, California. The vector data file is included in "Folds_OffshoreMonterey.zip," which is accessible from http://dx.doi.org/10.5066/F7F47M6T. The shelf north and east of the Monterey Bay Peninsula in the Offshore of Monterey map area is cut by a diffuse zone of northwest striking, steeply dipping to vertical faults comprising the Monterey Bay Fault Zone (MBFZ). This zone, originally mapped by Greene (1977, 1990), extends about 45 km across Monterey Bay (Map E on sheet 9). Fault strands within the MBFZ are mapped with high-resolution seismic-reflection profiles (sheet 8). Seismic-reflection profiles traversing this diffuse zone in the map area cross as many as 5 faults over a width of about 4 to 5 km (see, for example, figs. 3 and 5 on sheet 8). The zone lacks a continuous "master fault," along which deformation is concentrated. Fault length ranges up to about 20 km (based on mapping outside this map area), but most strands are only about 2- to 7-km long. Faults in this diffuse zone cut through Neogene bedrock and locally appear to minimally disrupt overlying inferred Quaternary sediments. The presence of warped reflections along some fault strands suggests that fault offsets may be both vertical and strike-slip. Specific offshore faults within the zone that are continuous with mapped onshore faults include the Navy Fault, Chupines Fault, and Ord Terrace Fault (Clark and others, 1997; Wagner and others, 2002). Carmel Canyon, a relatively straight northwest-trending arm of the Monterey Canyon system, extends through the southwestern part of the Offshore of Monterey map area. Carmel Canyon has three heads (Greene and others, 2002), two of which extend east and northeast into Carmel Bay within the map area; the third head extends southeast along the main canyon trend for about 3 km beyond the confluence with the heads in Carmel Bay. Carmel Canyon is aligned with and structurally controlled by the San Gregorio fault zone (Greene and others, 1991), an important structure in the distributed transform boundary between the North American and Pacific plates (see, for example, Dickinson and others, 2005). This Fault Zone is part of a regional fault system that is present predominantly in the offshore for about 400 km, from Point Conception in the south (where it is known as the Hosgri Fault; Johnson and Watt, 2012) to Bolinas and Point Reyes in the north (Bruns and others, 2002; Ryan and others, 2008). The San Gregorio Fault Zone in the map area is part of a 90-km-long offshore segment that extends northward from Point Sur (about 24 km south of the map area), across outer Monterey Bay to Point Año Nuevo (51 km north of the map area) (see sheet 9; see also, Weber and Lajoie, 1980; Brabb and others, 1998; Wagner and others, 2002). High-resolution seismic-reflection data collected across the canyon do not clearly image the San Gregorio Fault Zone, due largely to significant depth and steep canyon walls. Accordingly, we have mapped the 1,000- 1,300-m-wide fault zone largely on the presence of prominent, lengthy, geomorphic lineaments (sheets 1 and 2) and both geomorphic and lithologic contrasts across the fault. 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 Bruns, T.R., Cooper, A.K., Carlson, P.R., and McCulloch, D.S., 2002, Structure of the submerged San Andreas and San Gregorio Fault zones in the Gulf of Farallones as inferred from high-resolution seismic-reflection data, in Parsons, T., ed., Crustal structure of the coastal and marine San Francisco Bay region, California: U.S. Geological Survey Professional Paper 1658, p. 77–117, available at http://pubs.usgs.gov/pp/1658/. Brabb, E.E., 1997, Geologic Map of Santa Cruz County, California: A digital database, US Geological Survey Open-File Report 97–489, 1:62,500. Clark, J.C., Dupre, W.R., and Rosenberg, L.L., 1997, Geologic map of the Monterey and Seaside 7.5–minute quadrangles, Monterey County, California–A digital database: U.S. Geological Survey Open-File Report 97-30, 2 sheets, scale 1:24,000, http://pubs.usgs.gov/of/1997/of97-030/ 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 San Gregorio-Hosgri fault zone, coastal California: Geologic evidence and tectonic implications: Geological Society of America Special Paper 391, 43 p. Greene, H.G., Maher, N.M., and Paull, C.K., 2002, Physiography of the Monterey Bay National Marine Sanctuary and implications about continental margin development: Marine Geology, v. 181, p. 55–82. Greene, H.G., Clarke, S.H. and Kennedy, M.P., 1991. Tectonic Evolution of Submarine Canyons Along the California Continental Margin. From Shoreline to Abyss, in Osborne, R.H., ed., Society for Sedimentary Geology, Special Publication No. 46, p. 231–248. Greene, H.G., 1990, Regional tectonics and structural evolution of the Monterey Bay region, central California, in Garrison, R.E., Greene, H.G., Hicks, K.R., Weber, G.E., and Wright, T.L., eds., Geology and tectonics of the central California coastal region, San Francisco to Monterey: American Association of Petroleum Geologists, Pacific Section, Guidebook GB67, p. 31–56. Greene, H.G., 1977, Geology of the Monterey Bay region: U.S. Geological Survey Open-File Report 77–718, 347 p. Greene, H.G., 1990, Regional tectonics and structural evolution of the Monterey Bay region, central California, in Garrison, R.E., Greene, H.G., Hicks, K.R., Weber, G.E., and Wright, T.L., eds., Geology and tectonics of the central California coastal region, San Francisco to Monterey, Pacific Section American Association of Petroleum Geologists, Guidebook GB-67, p. 31–56. Johnson, S.Y., and Watt, J.T., 2012, Influence of fault trend, bends, and convergence on shallow structure and geomorphology of the Hosgri strike-slip fault, offshore Central California: Geosphere, v. 8, p. 1,632–1,656, doi:10.1130/GES00830.1. Ryan, H.F., Parsons, T., and Sliter, R.W., 2008. Vertical tectonic deformation associated with the San Andreas fault zone offshore of San Francisco, California: Tectonophysics, v. 429, p. 209–224, doi:10.1016/j.tecto.2008.06.011. Wagner, D.L., Greene, H.G., Saucedo, G.J., and Pridmore, C.L., 2002, Geologic Map of the Monterey 30' x 60' quadrangle and adjacent areas, California: California Geological Survey Regional Geologic Map Series, scale 1:100,000. Weber, G.E., and Lajoie, K.R., 1980, Map of Quaternary faulting along the San Gregorio fault zone, San Mateo and Santa Cruz Counties, California: U.S. Geological Survey Open-File Report 80–907, 3 sheets, scale 1:24,000, available at http://pubs.er.usgs.gov/publication/ofr80907.本数据集为DS 781的组成部分，提供了加利福尼亚州蒙特雷湾海域制图区地质与地貌图的褶皱相关数据。矢量数据文件包含于"Folds_OffshoreMonterey.zip"压缩包中，可通过http://dx.doi.org/10.5066/F7F47M6T获取。 蒙特雷湾半岛北侧及东侧的陆架，被一组走向北西、倾角陡立至直立的断裂弥散带切割，该带即蒙特雷湾断裂带（Monterey Bay Fault Zone, MBFZ）。该断裂带最初由Greene（1977、1990）完成填绘，延伸跨越蒙特雷湾全长约45千米（见附图9的图E）。蒙特雷湾断裂带内的断裂段通过高分辨率地震反射剖面（附图8）进行填绘。穿过制图区内该弥散带的地震反射剖面，在约4至5千米的宽度范围内可识别至多5条断裂（例如参见附图8中的图3与图5）。该断裂带不存在形变集中的连续“主控断裂”。单条断裂长度最大可达约20千米（基于制图区外的填绘结果），但多数断裂段长度仅约2至7千米。该弥散带内的断裂切割新近纪基岩，局部仅对上覆推断的第四纪沉积物产生微弱扰动。部分断裂段沿线存在反射波弯曲现象，表明断裂位移兼具垂直分量与走滑分量。该带内与陆上填绘断裂连续的近海断裂包括海军断裂（Navy Fault）、丘平斯断裂（Chupines Fault）以及奥德台地断裂（Ord Terrace Fault）（Clark等，1997；Wagner等，2002）。 卡梅尔峡谷（Carmel Canyon）是蒙特雷峡谷系统中一条相对平直的北西向分支，延伸穿过蒙特雷湾海域制图区的西南部。卡梅尔峡谷拥有三处源头（Greene等，2002），其中两处向东、东北延伸至制图区内的卡梅尔湾；第三处源头沿主峡谷走向向东南延伸，在与卡梅尔湾内各源头交汇后继续延伸约3千米。 卡梅尔峡谷与圣格雷戈里奥断裂带（San Gregorio fault zone）走向一致且受其构造控制（Greene等，1991），该断裂带是北美板块与太平洋板块之间弥散型转换边界的重要构造（例如参见Dickinson等，2005）。该断裂带属于区域性断裂系统，主体分布于近海区域，总长约400千米，南起康塞普申角（此处被称为霍斯格里断裂（Hosgri Fault）；Johnson和Watt，2012），北至博利纳斯与雷耶斯角（Bruns等，2002；Ryan等，2008）。制图区内的圣格雷戈里奥断裂带是一段长90千米的近海段的一部分，该段从瑟尔角（位于制图区以南约24千米）向北延伸，穿过蒙特雷湾外海至阿尼奥新角（位于制图区以北51千米）（见附图9；另参见Weber和Lajoie，1980；Brabb等，1998；Wagner等，2002）。由于峡谷水深较大且峡谷壁陡峭，横穿峡谷采集的高分辨率地震反射数据未能清晰成像圣格雷戈里奥断裂带。因此，本次研究主要通过显著、绵长的地貌线性特征（附图1与2）以及断裂两侧的地貌与岩性差异，完成了宽约1000至1300米的断裂带填绘。 褶皱主要通过地震反射剖面数据解译完成填绘（参见美国地质调查局开放文件报告（Open-File Report, OFR）2013-1071）。本次地震反射剖面采集于2007至2010年间。 参考文献 Bruns, T.R., Cooper, A.K., Carlson, P.R., and McCulloch, D.S., 2002, Structure of the submerged San Andreas and San Gregorio Fault zones in the Gulf of Farallones as inferred from high-resolution seismic-reflection data, in Parsons, T., ed., Crustal structure of the coastal and marine San Francisco Bay region, California: U.S. Geological Survey Professional Paper 1658, p. 77–117, available at http://pubs.usgs.gov/pp/1658/. Brabb, E.E., 1997, Geologic Map of Santa Cruz County, California: A digital database, US Geological Survey Open-File Report 97–489, 1:62,500. Clark, J.C., Dupre, W.R., and Rosenberg, L.L., 1997, Geologic map of the Monterey and Seaside 7.5–minute quadrangles, Monterey County, California–A digital database: U.S. Geological Survey Open-File Report 97-30, 2 sheets, scale 1:24,000, http://pubs.usgs.gov/of/1997/of97-030/ 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 San Gregorio-Hosgri fault zone, coastal California: Geologic evidence and tectonic implications: Geological Society of America Special Paper 391, 43 p. Greene, H.G., Maher, N.M., and Paull, C.K., 2002, Physiography of the Monterey Bay National Marine Sanctuary and implications about continental margin development: Marine Geology, v. 181, p. 55–82. Greene, H.G., Clarke, S.H. and Kennedy, M.P., 1991. Tectonic Evolution of Submarine Canyons Along the California Continental Margin. From Shoreline to Abyss, in Osborne, R.H., ed., Society for Sedimentary Geology, Special Publication No. 46, p. 231–248. Greene, H.G., 1990, Regional tectonics and structural evolution of the Monterey Bay region, central California, in Garrison, R.E., Greene, H.G., Hicks, K.R., Weber, G.E., and Wright, T.L., eds., Geology and tectonics of the central California coastal region, San Francisco to Monterey: American Association of Petroleum Geologists, Pacific Section, Guidebook GB67, p. 31–56. Greene, H.G., 1977, Geology of the Monterey Bay region: U.S. Geological Survey Open-File Report 77–718, 347 p. Greene, H.G., 1990, Regional tectonics and structural evolution of the Monterey Bay region, central California, in Garrison, R.E., Greene, H.G., Hicks, K.R., Weber, G.E., and Wright, T.L., eds., Geology and tectonics of the central California coastal region, San Francisco to Monterey, Pacific Section American Association of Petroleum Geologists, Guidebook GB-67, p. 31–56. Johnson, S.Y., and Watt, J.T., 2012, Influence of fault trend, bends, and convergence on shallow structure and geomorphology of the Hosgri strike-slip fault, offshore Central California: Geosphere, v. 8, p. 1,632–1,656, doi:10.1130/GES00830.1. Ryan, H.F., Parsons, T., and Sliter, R.W., 2008. Vertical tectonic deformation associated with the San Andreas fault zone offshore of San Francisco, California: Tectonophysics, v. 429, p. 209–224, doi:10.1016/j.tecto.2008.06.011. Wagner, D.L., Greene, H.G., Saucedo, G.J., and Pridmore, C.L., 2002, Geologic Map of the Monterey 30' x 60' quadrangle and adjacent areas, California: California Geological Survey Regional Geologic Map Series, scale 1:100,000. Weber, G.E., and Lajoie, K.R., 1980, Map of Quaternary faulting along the San Gregorio fault zone, San Mateo and Santa Cruz Counties, California: U.S. Geological Survey Open-File Report 80–907, 3 sheets, scale 1:24,000, available at http://pubs.er.usgs.gov/publication/ofr80907.