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Diversity of Sequence Stratigraphic Patterns and its Formation Mechanism in the Southern Slope Area: Eocene, Fushan Depression, South China Sea


The analysis of sequence stratigraphic patterns will considerably improve our insight into sequence architecture and depositional filling, and ultimately guide hydrocarbon exploration in sedimentary basins. A combined tectonic-stratigraphic interpretation of three-dimensional seismic reflection, well logs and core data is presented in this study focusing on a key oil and gas bearing area in the Fushan Depression, Beibuwan Basin, South China Sea. This paper demonstrates three types of sequence filling patterns in the southern slope area with a width of 50 km including: multi-level step-fault belt, flexure slope belt and gentle slope belt, clearly confirming the complexity and diversity of sequence patterns in continental basins. Comparative analysis of seismic reflection, palaeogeomorphology, fault activity and sedimentary facies distribution between the western and eastern areas indicates that a transfer zone was developed as a coordinated system of deformational features at the intersection of the western and eastern fault systems. The transfer zone had an important effect on the formation of various sequence patterns by dividing the Fushan Depression into two tectonic systems, forming different sequence patterns, and causing the formation of the flexure slope belt in the central area. On this basis, the transfer zone allows a new perspective for sequence analysis in continental basins, especially for the interpretation of the formation mechanism of various sequence patterns. In addition to the distribution of depositional system, these sequence stacking patterns together with the transfer zone also control the accumulation of hydrocarbons, suggesting that the exploration targets in the Fushan Depression may be non-uniform.