本研究通过对琼东南盆地深水区高分辨率三维地震资料的精细解释,在琼东南盆地东北部陆坡发现了4期(MTC1、MTC2、MTC3和MTC4)块体搬运沉积复合体(MTCs)。其中,MTC 1、MTC 2 和 MTC 4 发育规模较小,内部挤压程度低,平均厚度130-150m；MTC 3发育规模最大,内部变形最为剧烈,平均厚度200m。通过识别和分析MTC 3内部和外部的运动学标志,确定了其向西南方向搬运,并将其发育过程划分为初始边坡失稳阶段、滑移阶段和流体转换阶段。根据本次识别的MTCs形态及内部结构特征,结合研究区的构造与气候演化背景,认为该多期次MTCs的发育主要受地层坡度、多边形断层活动、海平面波动和高沉积速率等因素的综合控制：MTCs下部大量发育的晚中新世以来持续活动的断层对MTCs起了触发作用；中新世晚期(10.5Ma)以后海平面的快速降低和上升,改变沉积物强度和地层压力等参数,进一步促进了MTCs的发育；5.5Ma以来琼东南盆地的快速沉降导致可容纳空间增大、物源进积以及坡度加大等,为多期次MTCs的形成提供了条件。本研究结果可增进对琼东南盆地东北部陆坡第四纪以前MTCs的沉积特征及触发因素的认识,也可为探究南海地区MTCs的发育过程提供参考。

This study identifies four phases (MTC 1, MTC 2, MTC 3, and MTC 4) of mass transport complexes (MTCs) on the northeastern continental slope of the Qiongdongnan Basin, through detailed interpretation of high-resolution 3D seismic data from the deep-water area of the basin, and amplitude-time slice analysis based on 3D seismic data. Among these, MTC 1, MTC 2, and MTC 4 are small in scale with low internal compression, whereas MTC 3 is the largest and exhibits the most intense internal deformation. By identifying and analyzing the kinematic indicators both within and outside MTC 3, the transport direction was determined to be southwest. The development of MTC 3 was divided into three stages: initial slope instability, sliding, and fluid conversion. Based on the identified morphologies and internal structural characteristics of the MTCs, and considering the tectonic and climatic evolution of the study area, it is suggested that the development of these MTCs was primarily controlled by a combination of factors, including slope gradient, polygonal fault activity, sea level fluctuations, and high sedimentation rates: the numerous continuously active faults developed in the lower part of the MTCs since the Late Miocene have acted as triggers for the formation of the MTCs; after the rapid sea-level drop and rise during the Late Miocene (10.5 Ma), changes in sediment strength and stratigraphic pressure parameters further promoted the development of the MTCs: since 5.5 Ma, rapid subsidence in the Qiongdongnan Basin has increased accommodation space, sediment influx, and slope steepening, thus providing favorable conditions for the formation of MTCs. The findings of this study contribute to the understanding of the sedimentary characteristics and triggering factors of pre-Quaternary MTCs on the northeastern continental slope of the Qiongdongnan Basin, and provide a reference for investigating the development of MTCs in the South China Sea region.