IDENTIFICATION OF SEQUENCE BOUNDARIES AND ESTABLISHMENT OF SEQUENCE STRATIGRAPHIC FRAMEWORK IN THE CRETACEOUS NANTUN FORMATION IN THE NORTHERN BEIXI SLOPE AREA OF THE HAILAER BASIN

Using the theories and methods of high-resolution sequence stratigraphy in rift lacustrine basins, we analyzed seismic, logging and drilling core data of the Nantun Formation in the northern Beixi Slope area of the Hailaer Basin in order to understand its sequence stratigraphy. We identified third-order sequence boundaries and maximum flooding surfaces and established the sequence stratigraphic framework of the Nantun Formation, which includes two third-order sequences (sequence I and sequence Ⅱ); each can be divided into three systems tracts. Data used in the sequence and systems tract identification include seismic, outcrop, and logging data. Systems tracts in sequence I include N1-HST, N1-TST, and N1-LST. Systems tracts in sequence Ⅱ include N2-HST, N2-TST, and N2-LST. The controlling factors in sequence development are structural rifting, climate condition, lake level change, and sediment supply.