SEISMIC FACIES ANALYSIS AND FILLING HISTORY RECONSTRUCTION OF SMALL FAULTED DEPRESSIONS IN NORTHERN SOUTH CHINA SEA——A HISTORICAL CASE ON YACHENG FORMATION IN YANAN DEPRESSION OF THE QIONGDONGNAN BASIN

The Yanan Depression, a depression located in shallower water of the Qiongdongnan Basin, was selected as a case to study the seismic facies and the filling history of a depression contains transitional facies for relatively more logging data are available there. The seismic facies of the Yacheng Formation is carefully studied in an isochronous stratigraphic framework, and the relations between seismic facies and sedimentary facies were established upon the existing stratigraphic framework, classic depositional models and logging data in shallow water. The relations make it possible to predict the distribution of sedimentary facies in the areas without logging data. Referring to the classic model of a faulted basin and using Yanan Depression as the prototype, this paper established the seismic facies and depositional infilling model of a small faulted depression of transitional facies. The results are significant not only for this depression, but also for similar depressions in deep water. The model could be used as a powerful weapon for future exploration in deep water.