Coal-accumulating and coal-forming patterns within sequence stratigraphy framework of Early Cretaceous in Hailar basins

This paper analyzed the basin-filling sequences, sedimentary sequence and coal accumulation pattern. 6 third-order sequences were divided in the Zhalainuoer Group, which respectively correspond to Tongbomiao Formation, the first and second member of Nantun Formation, the first and second member of Damoguaihe Formation and Yimin Formation. The lacustrine transgressive systems tracts in sequence and were developed with major Ⅲ Ⅵ coal. In the sequence, coal seams were developed regularly, from alluvial plain to upper delta plain, lower delta plain and lacustrine environment. Based on the study of the thickness of the main seams, base sandbody and the paleogeographic environment in the coal-forming period, two kinds of coal accumulating modes were summarized in the sequence and. Ⅲ Ⅵ