Abstract: Fan deltas of the abrupt slope and the gentle slope areas, were developed in the W11 area of 1st Member of the Liushagang Formation in Southwestern Weizhou Depression, Beibuwan Basin. Based on the lithology, logging and seismic data, the different characteristics between these two kinds of fan deltas were analyzed and the main controlling factors of the fan delta were discussed. The fan deltas at abrupt slope area, which were mainly distributed at the steep slope zone of the middle part of 1st Member of the Liushagang Formation in the northern of the study area, were comparatively coarse grain-sized and were mainly thick-layer sandstone rock deposited from the gravity flow, with large depositional thickness and small scale planar distribution. However, the fan deltas at gentle slope, which were widely distributed in the lower part of 1st Member of the Liushagang Formation at Southwestern Weizhou Salient in the southern of the study area, had a mixed gravity flow and tractive current with relatively fine grain-sized, a small depositional thickness and a wide range of planar extension. The development and distribution of these two kinds of fan deltas were mainly controlled by structural framework, paleotopography and basal level change.

Key words: Weixinan Depression, 1st Member of Liushagang Formation, the fan delta at gentle slope area, the fan delta at abrupt slope area, sedimentary characteristic