陆坡重力流沉积地貌单元三维地震表征及其成因-以琼东南盆地陵水凹陷为例

3D seismic characterization and origination of gravity flow geomorphic units on continental slope: A case study of Lingshui Sag, Qiongdongnan Basin

海底地貌一直是国内外学者关注的重点领域。基于琼东南盆地陵水凹陷1 000 km^(2)高分辨率三维地震资料,利用GeoFrame综合解释平台、Surfer三维成图等技术,对琼东南盆地陵水凹陷现今海底地貌进行精细刻画。研究结果表明:(1)琼东南盆地下陆坡带主要发育水道(大型水道C1和冲沟-朵体复合体G1—G3)、周期阶坎以及滑坡体系3类典型地貌单元。(2)水道C1宽深比31.5~232,主要由陆坡水道运输的碎屑物质冲刷而成,冲沟-朵体复合体G1—G3末端可见明显朵体发育;同时,可在水道和滑坡体系内识别到周期阶坎;研究区处于陆坡滑塌的体部-趾部区域,广泛发育挤压脊、舌状体等沉积构造。(3)推测认为研究区海底地貌主要由上陆坡滑坡引起,在物源与海平面升降的加持下,形成如今的综合型地貌。

Seafloor topography has always been the key of scientific study. Based on 1 000 km^(2) high-resolution 3D seismic data of Lingshui Sag in Qiongdongnan Basin, South China Sea, the GeoFrame platform, Surfer 3D mapping, and other technologies were applied to characterize the current submarine landform of Lingshui Sag. Results show that the lower slope of Qiongdongnan Basin presented mainly three types of geomorphic units: channels(including large channel C1 and gully-lobe complexes G1-G3), cyclic steps, and submarine landslides. The widthdepth ratio of channel C1 that was mainly scoured by debris transported via continental slope channels, is between 31.5 and 232. At the ends of G1-G3 of gully-lobe complex developed obvious lobes. The cyclic steps could be identified in the channel and submarine landslides. Squeeze ridges and underwater tongues were developed widely in the main body and the toes of slumps on continental slope. We speculate that the seafloor topography in the Lingshui Sag was mainly caused by submarine landsliding on the upper continental slope, which was intensified by deposit overload and sea level fluctuation, and finally the modern landform was formed.