Sequence Hierarchy of Sinian-Cambrian Supersequence in South China and Its Significance for Global Correlation
Taizhong Duan1 and Jian Wang2
1 Marathon Oil Company, Houston, TX
2 Chengdu Institute of Geology and Mineral Resources, Chengdu, China
Sinian-Cambrian Supersequence (SCS) consists of eight third-order sequences (TOS), four of which are formed below the TOS containing the SCS maximum-flooding surface, and three formed above it. Each of these third-order sequences consists of deeper-water black shale and laminated chert beds, fine carbonate, and shallow-water carbonate grainstones and stromatolitic carbonates, usually arranged from bottom to top as a deepening-upward and then shallowing-upward cycle. These TOSes are easily recognizable along carbonate platform margin area, but it is difficult or impossible to recognize them in deep water depositional environment-only area and in very shallow inner carbonate platform area. In deep water depositional environments, lithology is too uniform (all black shale or chert) to indicate any significant change of sequences, while in inner carbonate platform area, regional, these strong dolomitization destroyed most of original depositional indicators. Vertically the deepening-upward and shallowing-upward couple cycles may be indicated by any combination of lithofacies existing. Horizontally, these TOSes expand smaller initial carbonate platforms, fill-up any shallower inter-platform basins earlier or later, and then prograde toward open ocean up to hundreds of kilometers. These TOSes are compatible to Sauk cycles in North America, Middle East, and similar sequences in Australia.