THE SEQUENCE STRATIGRAPHY OF HUANGLIU FORMATION AND THE INTERNAL STRUCTURES OF SUBMARINE FAN IN DONGFANG AREA,YINGGEHAI BASIN

A large submarine fan complex was discovered in the Dongfang area of the Yinggehai Basin. Six 4-order sequences in the 1st Member of Huangliu Formation (SQHL1) were recognized. The submarine fan complex was mainly developed in SQHL1¹-SQHL1³ (in LST). High resolution sequence stratigraphic analysis reveals that the submarine fan is consisted of several lobes formed in different times and the sands, which are formed as the 5th-order sequences, exhibit various shapes in a plane view. The lobes can be classified into three kinds, i.e. the simple fan lobes, complex fan lobes and single channels. Simple fan lobes, which are mainly occurred in the Dongfang 29-1 are, are rarely observed. The complex fan lobes are common, which are formed by cutting and stacking within simple fan lobes or curved channels, and could not be divided further. Single channel is the one isolated. Research shows that the simple fan and complex fan lobes in this area are related with channels and branch channels. The internal complicated structures of submarine fan owe their origin to regional tectonics, filling deposits and the development of structural transfer zone nearby. A series of regional tectonic activities occurred while the T31 sequence boundary was formed, which controlled the sedimentation of the time. In addition, the Yingxi Slope to the west of the Dongfang area was located in a structural transfer zone where the deposits from the ancient Lam River were transported through the Kontum Uplif to the Dongfang area. As the result, a huge delta and a large submarine fan complex were formed.