Depositional Architecture Characteristics of Deepwater Depositional Systems on the Continental Margins of Northwestern South China Sea

Deepwater reservoir has become one of the major issues in submarine hydrocarbon exploration in China recently. Based on high resolution 2D and 3D seismic data, depositional patterns and architectures of deepwater depositional systems are identified on the northwestern continental margins of the South China Sea. Apart from hemipelagic and pelagic mudstones, a number of gravity flow deposits are extensively developed, including large scale mass transport deposits (MTDs), submarine canyons and sediment waves. Four slope types are identified, including progradational type, slumping type, channelized type, wide and gentle type slopes. Each slope type has different morphological features and depositional architectures. Giant MTDs occur on the slumping and channelized slopes, whereas the sediment waves are only developed on the lower part of wide and gentle slope and the two sides of the Changchang segment of the Central Canyon. Due to special morphological features with an eastward flared shape and increasing water depth in the deepwater area since the Late Miocene, the unique Central Canyon with a trend paralleling to shelf break of northern margins is formed along the axial deepest water-depth line. The fillings in the Central Canyon are composed by not only turbidity channels from the head segment of the canyon in the west, but also the MTDs from the continental slope in the north, particularly from the slumping and channelized slopes. The Central Canyon system could be considered as multiple-sources to sink system for sediment transportation, and also a system containing important reservoirs in the deepwater area on the northwestern continental margin of the South China Sea.