Genesis and Characteristics of Miocene Deep‐water Clastic Rocks in Yinggehai and Qiongdongnan Basins, Northern South China Sea

Abstract

AbstractVarious deep‐water deposits developed in the Yinggehai Basin and Qiongdongnan Basin (Ying‐Qiong Basin) in the northern South China Sea, making the two basins significantly hydrocarbon‐producing areas and ideal for studying the genetic mechanism and sedimentary characteristics of deep‐water clastic rocks. Using cores, image well logging, heavy mineral assemblages, and seismic data, we thoroughly studied the geometry, tectonic background, driving mechanism, and source‐to‐sink process of deep‐water deposits in the study area. The results showed that: (1) there were five genetic mechanisms of deep‐water clastic rock, i.e., slides, slumps, debris flows, turbidity currents, and bottom currents. (2) The sliding deposits were distributed from the delta front to the continental slope toe. The slumping deposits were mainly distributed at the continental slope toe or the basin's central area, far from the delta front. The turbidity deposits were widely developed in the deep‐water area, but with huge differences in thickness. The bottom currents mainly reworked previous deposits far from the slope. (3) Slip and extension along the preexisting fault zone were the main structural factors that drive the axial channel formation at the slope foot. (4) The sand‐rich gravity sediment flows in the Ying‐Qiong basin were primarily caused by the direct supply of terrigenous debris into the marine environment over the slope break.