琼东南盆地陆坡体系发育特征及其控制因素

琼东南盆地位于南海北部大陆边缘,是发育于前古近系基底之上的裂陷盆地,自中新世以来进入裂后沉降期。10.5Ma以来,随着盆地演化进入加速沉降阶段,盆地水深迅速增大,陆坡体系开始发育。根据陆坡体系的外部形态及其内部沉积构成特征,在空间上自西向东可以将其划分为3段,盆地西部陆坡以快速进积的陆坡楔状体为主要特征;盆地中部陆坡以陡倾的陆坡角度,大量的陆坡峡谷、沟谷和大规模的沉积物重力流等陆坡沉积为特征;盆地东部陆坡以宽缓的陆坡形态为主要特征。研究表明,沉积物供给和断裂活动对陆坡体系的发育都具有重要的控制作用;同时,陆坡发育时期所经历的沉积过程、古地貌形态和相对海平面变化对陆坡体系的发育也具有一定的控制作用。

Depositional Characteristics and Controlling Factors of Continental Slope System in the Qiongdongnan Basin

The Qiongdongnan Basin is a rift basin formed on the Pre-Paleogene basement in the northern continental margin of South China Sea. This study reveals that the continental slope system has been developing since 10.5 Ma, with the accelerating subsidence stage of the basin and the rapid increase of the water depth of the basin. Based on the differences of the external morphology and sedimentary structure features of the slope system in this basin, the continental slope can be classified into three segments from west to east: The west segment is characterized by quick progradation in the continental slope area, while the east segement has the widest gentle angle of the slope system, and the steepest angle, a plenty of slope canyons, gullies and large-scale sediment gravity flow are the characteristics of the center segment. According to this study, sediment supply and activity of intrabasin faults are the main controlling factors of the slope system development. The sediment processes, paleo-morphology and relative sea level are the minor controlling factors.