Folds--Offshore Pigeon Point, California

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.本DS 781数据集的本部分，提供了加利福尼亚州近海皮格恩角（Offshore Pigeon Point）制图区地质与地貌图所需的褶皱相关数据。矢量数据文件已打包至"Folds_OffshorePigeonPoint.zip"，可通过链接http://dx.doi.org/10.5066/F7513W80获取。 近海皮格恩角制图区位于圣安德烈亚斯断层（San Andreas Fault）西南约15至25千米处；该断层是北美板块与太平洋板块之间分布型转换边界的主导构造。本制图区横跨右旋皮格恩角断层带（Pigeon Point Fault zone），该断层带是圣安德烈亚斯断层系统中西部的重要构造。皮格恩角断层带主体分布于近海区域，整体延伸达400千米：南起康塞普申角（Point Conception），北至博利纳斯（Bolinas）与雷耶斯角（Point Reyes）（Dickinson等，2005），并在制图区内的佩斯卡德罗角（Pescadero Point）、半月湾（Half Moon Bay）以北数千米的柱石角（Pillar Point）等海岸岬角处登陆。 在近海区域，皮格恩角断层系统形成了宽约2至4千米的分布型剪切带，包含两条主要的分歧断层分支。西侧分支（亦称弗里霍莱斯断层（Frijoles Fault））从佩斯卡德罗角向近海延伸；东侧分支（亦称海岸断层（Coastways Fault）或海豹湾断层（Seal Cove Fault））在本制图区内主体位于陆上。据推测，本区域内皮格恩角断层带的累积侧向滑移速率为4至10毫米/年（美国地质调查局（U.S. Geological Survey），2010）。皮格恩角断层带的西侧分支（即弗里霍莱斯断层）构成了皮格恩角高地的东部边界。 褶皱的制图工作主要通过地震反射剖面（seismic reflection profile）数据解译完成（详见OFR 2013-1071），该批地震反射剖面数据采集于2007至2010年间。 参考文献 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. 及 Brabb, E.E.，2005年，加利福尼亚沿海新近纪皮格恩角-霍斯格里断层带的净右旋滑移：地质证据与构造意义：美国地质学会特刊391，共43页。