Sedimentary characteristics and controlling factors of beach bars in the Upper Submember of the Fourth Member of the Shahejie Formation in the Lijin subasin

Abstract：Based on an analysis of the core, well logs and seismic data and by using sedimentological and sequence stratigraphical theories, the Upper Submember of the Fourth Member of the Shahejie Formation in the Lijin subbasin is divided into one sequence and three systems tracts and subdivided into seven parasequence sets. The sedimentary characteristics of beach-bar sandstone and its distribution in the parasequence sets have been studied. The beach bars of lakeshores and shallow lakes in parasequence sets 1 and 2 are best developed and storm beach bars of parasequence sets 3 and 4 are also best developed. The sandy beach bars in parasequence sets 6 and 7 are poorly developed but carbonate beach bars are well developed. The controlling factors of beach bars are analyzed. The paper presents the concept of controls on beach bars by the system of "paleoclimate-provenance-basin". This concept is an improvement and supplement of the traditional "source-controlled theory" and may more rationally explain the origin and distribution of beach bars.