Incision of Submarine Channels Over Pockmark Trains in the South China Sea

The genesis of submarine channels is often controlled by gravity flows, but channels can also be formed by oceanographic processes. Using multibeam bathymetry and two‐dimensional seismic data from the western South China Sea, this study reveals how pockmarks can ultimately form channels under the effect of bottom currents and gravity‐driven sedimentary processes. We demonstrate that alongslope and across‐slope channels were initiated by pockmark trains on the seafloor. Discrete pockmarks were elongated due to the erosion of gravity‐driven sedimentary processes and bottom currents, and later coalesced to form immature channels with irregular thalwegs. These gradually evolved into mature channels with continuous overbanks and smooth thalwegs. Submarine channel evolution was significantly influenced by seafloor topography since the Late Miocene. The evolutionary model documented here is a key to understanding how channels are formed in deep‐water environments. Submarine channels are prominent erosional features on continental slopes and basin floors. They are usually formed by ocean currents flowing alongslope and sediment avalanches flowing downslope. Here, we investigate a system of channels on the western South China Sea using geophysical methods. The channels are formed in a region with widespread seafloor depressions (pockmarks) formed by the seepage of fluid into the water column. Gravity‐driven sedimentary processes and ocean currents reshaped these pockmarks, which were ultimately merged together to form immature and irregular channels. Under continued erosion, the immature channels eventually developed mature channels with continuous overbanks and smooth channel floors. This study reveals that ocean currents and gravity processes can form channels with different orientations by eroding pre‐existing pockmarks. A complex system of channels in the western South China Sea was formed by the erosion of seafloor pockmarksThe evolution from pockmarks to channel comprises three stages: pockmark train, immature, and mature channelThis on‐going system of channels was initiated in the Late Miocene and significantly influenced by seafloor topography A complex system of channels in the western South China Sea was formed by the erosion of seafloor pockmarks The evolution from pockmarks to channel comprises three stages: pockmark train, immature, and mature channel This on‐going system of channels was initiated in the Late Miocene and significantly influenced by seafloor topography