CHARACTERISTIC OF BEACHY UNDERWATER ALLUVIAL FAN FACIES——WITH A PRACTICAL EXAMPLE

Gaoyou Depression is a dustpan like depression steep in north and gentle in south. The properties of sediments from Dainan Formation in the depression are obviously controlled by paleogeographic environment. The sediments on the northern gentle slope belt of the depression mainly are of delta facies and that on the southarn slope belt mainly of beachy underwater alluvial fan facies. The origin of the beachy underwater alluvial fan facies can be either the transport of terrigenous elastics directly into the lake or the extension of the terrigenous pluvial facies into a lake basin, or may be the both. This paper introduces the lithological properties, the rock texture, and the structure of the beachy underwater alluvial fan facies in details, and presents a profile model as well.