LI Pan1, XIAO Dongsheng2, SHI Xiaofei2, MA Qiang2, LIN Tong1, YANG Runze1
1 Research Institute of Petroleum Exploration and Development,PetroChina,Beijing 100083,China; 2 Research Institute of Petroleum Exploration and Development,Tuha Oilfield,PetroChina,Xinjiang Hami 839009,China
Abstract：Megabed is a widely used term in the English literature,but has not been reported in official Chinese publications. Megabeds refer to giant event beds formed by sediment gravity flows. They can reach tens of meters to hundreds of meters in thickness and hundreds of cubic kilometers in volume,that is,approximately 1-2orders of magnitude larger than their surrounding normal deepwater intervals. Megabeds tend to be distinct from enclosing strata in terms of their thickness,grain size,composition,and commonly show multi-layer vertical structures that may record gravity flow transformation,differentiation and other deepwater transport and depositional processes. They are of great significance to geological events and basin analysis,provenance/paleogeography restoration,geohazard mitigation,and oil and gas exploration. In this paper,the conceptual connotation of megabed and related terms is firstly reviewed,and then the sedimentary characteristics of megabeds are analyzed and summarized,including their scale,composition,vertical structure and sequence. On this basis,the transport and depositional processes,as well as the initiation mechanisms of megabeds are discussed. Finally,existing problems and future research directions are discussed. The aim is to arouse extensive attention and in-depth research on megabeds across China.
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