Late Miocene Red River submarine fan,northwestern South China Sea

A huge submarine fan is discovered through the research of the seismic and borehole data in the binding site of Yinggehai basin and Qiongdongnan basin in northwestern South China Sea. The fan, mainly formed during Late Miocene (Huangliu period) has an area over 10000 km² and maximum thickness of over 2000 m. It is characterized by a wedge-shaped oblique progradation configuration on the dip profile and a hummocky bidirectional progradation configuration on the strike profile. The core and Logging data from the well YC35-1-2 located in the front side of the fan indicate that sandy gravity flow deposits are predominant in lower Huangliu Formation and change to interbeds of sand and mud in upper Huangliu Formation. The fan is interpreted as a sand/mud-rich submarine fan in combination with the bathyal geological background of Huangliu period. A preliminary analysis of provenance indicates that neither the Guiren Uplift in the west nor the Hainan Uplift in the north can serve as the major provenance for the submarine fan. The provenance is considered to be from the Red River, based on the sedimentary facies study of the Huangliu Formation in Yinggehai basin. The fan is thus named as “Red River submarine fan”. The Red River depositional system consists of the Red River submarine fan, the Red River delta, and associated submarine canyons. The discovery of the Red River submarine fan provides important information for the research of the uplift of Tibetan Plateau and the evolvement of Red River Fault Zone. Furthermore, it also points out a new direction for the deepwater hydrocarbon exploration in the northern South China Sea.