Gravity Sediment System in the Margin of Middle Miocene Carbonate Slope in Northwest South China Sea

High resolution 3D seismic data revealed the development of dense gullies around ancient carbonate platform in Northwest South China Sea. They exhibit straight linear feature, flooring on the top of Middle Miocene with coalescing features. The length of the largest gully identified in the eastern slope could reach to 33 km, with the width ranging from 300 m to 800 m. The gullies elongate from northwest to southeast, expressing uniform directionality. The architectures of gullies exhibit their unique filling evolution history. This filling feature implies the gullies didn’t accept sediment filling during their evolution history, instead by the later cover by the younger intervals. However, in the longest gullies in the eastern margin of platform, the filling deposit is characterized by high amplitude, medium frequency and continuous seismic bodies, which is similar with the typical deep water channel filling. The distribution of the gullies show close relationship with the development of polygonal fault system (PFS), and the activities of the various currents reworked the architecture of the gullies, making the final framework of the gullies system.