The Role of Bottom Currents on the Morphological Development Around a Drowned Carbonate Platform, NW South China Sea

The seafloor around carbonate platforms is largely shaped and modified by downslope processes. However, the role of alongslope processes, including bottom currents, on the morphological development of carbonate platforms remains poorly understood. Here, we use high-resolution multibeam bathymetric data and two-dimensional seismic profiles to investigate the detailed sea-floor morphology around the Zhongjianbei carbonate platform (ZCP) in the northwest South China Sea. A series of depositional bodies and erosional channels are identified to the south of the ZCP and are interpreted as contourite drifts and channels resulted from the interaction between bottom currents and bathymetric features. In addition, active fluid seepages have led to the formation of wide-spread pockmarks on the seafloor. Importantly, the contourite channels and widespread pockmarks also show a close relationship in their distribution. We propose that the contourite channels around the ZCP are evolved from the coalescence of pockmarks under the persistent erosion of bottom currents. Based on the morphological analysis, we reconstruct the past bottom-current pathways around the ZCP that are parallel to the platform slopes and heading to the south. This study provides new insights into the formation of complex bathymetry and helps understanding how bottom currents and active fluid seepages can influence the morphological development around carbonate platforms.