Sedimentary characteristics and genetic mechanism of a deep-water channel system in the Zhujiang Formation of Baiyun Sag, Pearl River Mouth Basin

摘要

The external geometry, internal architecture and sedimentary evolution processes of the deep-water channel system in Zhujiang Formation in the Midwest of Baiyun Sag have been revealed in detail according to the integrated analysis of 3D seismic data and a large number of drilling and logging data sets. In addition, the controlling effect of sediment supply, sea level change, shelf break zone and palaeogeomorphology on the deepwater channel system was discussed. Finally, it is concluded that the development and distribution of the deep-water channel system is controlled by both provenance and landform. The deep-water channel system can be subdivided into different sections: the provenance area, the waterway and the sedimentary area. It presents the features of a 'three segment channel' which indicates that the fluid energy of the gravity flow changes from weak to strong and then weak along depositional inclination. Because the processes of internal filling and latter reformation which the channel experienced in different sections during different periods are complex, the inner filling characteristics of the channels are different, mainly high sand-shale ratio superimposed channel (sand-rich deposit) and low sand-shale ratio channel-levee complex (sand-lean deposit). It is clear that the development and spatial distribution characteristics of deep-water channel system in Zhujiang Formation are controlled by the shelf edge delta of Pearl River, forced regression, the shelf break zone and restricted landform collectively. The shelf edge delta at the lower member of Zhujiang Formation in the north of Baiyun Sag provides the large amount of clastic sediments for the development of deep-water channel system. Forced regression drives the continuous transportation of the sediments from shelf edge to deep-water channel system. The shelf break and the fault slope break provide favorable paths and topographic conditions for transportation of the sediments in the deep-water channel system. The fracture systems and the subaqueous low uplifts influenced the spatial distribution of the deep-water channel system together.