Characterization of Mass-Transport Deposits on a Pliocene Siliciclastic Continental Slope, Northwestern South China Sea
Published:January 01, 2011
Mangzheng Zhu, Stephan Graham, Tim McHargue, 2011. "Characterization of Mass-Transport Deposits on a Pliocene Siliciclastic Continental Slope, Northwestern South China Sea", Mass-Transport Deposits in Deepwater Settings, R. Craig Shipp, Paul Weimer, Henry W. Posamentier
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Abstract: The characteristics, evolutionary history, and triggering mechanisms of successive siliciclastic mass-transport deposits (MTDs) of late Cenozoic age on the northwestern South China Sea margin were studied using borehole and 2D/3D reflection seismic data. Multiple mass-transport deposits of various scales and morphologies formed from Pliocene to Holocene time in high-slope-gradient and high-sedimentation-rate parts of the Qiongdongnan and Yinggehai basins. In plan view, MTDs documented by 3D seismic data, deposited between 3 and 2 Ma, are 1 to 11 km wide and 4 to 29 km long. Two seismic geomorphologic characteristics of a typical MTD comprise a basal surface and displaced masses of sediments. Internal seismic facies of the displaced mass consist of extensional wedge facies in upslope areas, thrusted facies in intermediate areas, and chaotic or mounded facies in distal downslope areas. These MTDs likely were triggered by a combination of mechanisms. Seafloor oversteepening, rapid accumulation of thick sedimentary deposits, overpressure, and a tectonically active basin setting provide a background favoring formation of MTDs. Additionally, seismicity, abrupt increase of sedimentation rates, rapid slope progradation, and release of gas contributed to triggering mass-transport deposition in the study area.
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Mass-Transport Deposits in Deepwater Settings
Historically, submarine-mass failures or mass-transport deposits have been a focus of increasingly intense investigation by academic institutions particularly during the last decade, though they received much less attention by geoscientists in the energy industry. With recent interest in expanding petroleum exploration and production into deeper water depths globally and more widespread availability of high-quality data sets, mass-transport deposits are now recognized as a major component of most deep-water settings. This recognition has lead to the realization that many aspects of these deposits are still unknown or poorly understood. This volume contains twenty-three papers that address a number of topics critical to further understanding mass-transport deposits. These topics include general overviews of these deposits, depositional settings on the seafloor and in the near-subsurface interval, geohazard concerns, descriptive outcrops, integrated outcrop and seismic data/seismic forward modeling, petroleum reservoirs, and case studies on several associated topics. This volume will appeal to a broad cross section of geoscientists and geotechnical engineers, who are interested in this rapidly expanding field. The selection of papers in this volume reflects a growing trend towards a more diverse blend of disciplines and topics, covered in the study of mass-transport deposits.