南海北部陆坡峡谷脊部精细结构、沉积成因及储层发育规律OA

Submarine canyon ridges are critical enrichment zones of gas hydrates in the South China Sea(SCS)and other places of the world.Compared with well-studied submarine canyons,the characteristics of sedimentation and formation processes of canyon ridges remain insufficiently revealed.By focusing on the Baiyun slope canyon in the northern SCS,we studied systematically the sequence stratigraphy and seismic geomorphology of the canyon ridge based on high-resolution 3D seismic data.Through seismic interpretation,five key geological interfaces were identified and dividing the stratigraphic sequence from 10.5 Ma to the present into four evolutionary stages(SU1～SU4).Seismic facies analysis and thickness maps showed two periods of evolution of the canyon ridge:the construction period(10.5～2.6 Ma)and the growth period(2.6 Ma-present).The construction period was mainly characterized by the formation of initial landforms,while the growth period was characterized by continuous vertical sedimentary accumulation.Notably,since the Middle Pleistocene(0.6 Ma present),the sedimentation rate was significantly increased,which may be closely related to the dramatic increase in terrestrial debris flux caused by the climate transition in the Middle Pleistocene.In addition,3D seismic geomorphological analysis demonstrated that the canyon ridge has developed large-scale undulating bedforms(wavelength 0.5～4.0 km,wave height 6.3～12.2 m)since 10.5 Ma.Combined with upslope migration characteristics,irregular circular pit-shaped planar features,and comparative studies among domestic and international research outcomes,interpretations including normal faults,landslides,and creep processes could be excluded.These asymmetric undulations were interpreted as sediment waves formed by supercritical turbidity current hydraulic jumps.Model calculations and seismic attribute extraction revealed coarser sediment grain sizes in trough regions compared to crests or bedform highs,indicating a higher gas hydrate enrichment potential in these trough areas.