Geomorphic Characteristics And Genetic Mechanism Of The Baiyun Deepwater Area On The Northern Slope Of The South China Se

The continental slope is the most prominent part of the continental margin and is also a necessary part of the transportation of continental margin sediments from the continental shelf to deep-water basins.The transportation of sediments and various bottom currents can cause erosion and transformation of the continental slope,shaping the complex modern continental slope.Recent studies have shown that both along-slope processes(contour currents)and down-slope processes(gravity flow)dominate continental slopes.A systematic understanding of different types of bottom current actions and their interactions is of great significance for revealing the formation and evolution mechanisms of complex continental slope topography.The Baiyun deep-water area in the northern South China Sea continental slope,as an important area for the transportation of continental shelf sediment to the deep sea,is an ideal area for studying the shaping process of bottom current on the topography of the continental slope canyon area and the sediment transportation process.This study comprehensively uses high-resolution multibeam topography and sub-bottom profile data obtained in recent years,combined with drilling data,to identify and analyze modern erosion and deposition topographic units in the Baiyun deep-water area of the northern South China Sea continental slope,and discusses factors controlling the topographic formation and evolution in the study area.The following understandings were obtained:(1)Geomorphological features are developed in the study area,including contourite drifts,sediment waves,sedimentary undulations,units related to landslides including MTDs and turbidities,erosional features including failure scar,channels,furrows,and contourite channels.(2)Contour currents are indicated by four types of contourite drift deposits identified in the area and including elongated drift,elongated-mounded drift,patchy drift,and sediment waves.(3)The circulation pattern in Baiyun deep-water area since Late Pleistocene can be summarized as follows:when South China Sea Deep Water upward along the contour,it divides into two branches:one branch flows westward to the southern slope along isobaths;one branch turns eastward to the eastern region of northern slope.(4)Down-slope processes and along-slope processes play a dominant role in shaping the northern continental slope of the South China Sea.During low sea-level periods,increasing in terrestrial material can lead to an increase in landslide activity and gravity flow in the area,with down-slope-related deposition and erosion dominating;during high sea-level periods,terrestrial material from rivers decreases,landslides and gravity flow weaken,with bottom current-related isobathic sedimentation and erosion dominating.This study has guiding significance for oil and gas exploration and engineering geological risk assessment in this area and has certain enlightening effects on global research on continental slope topographic feautres and their formation and evolution mechanisms.