【摘要】 通过3D地震资料,在琼东南盆地西部陆坡(15°30′00″~16°30′00″N)、早更新世至今的沉积地层中,自下而上依次识别了3套重力流沉积旋回,每套重力流沉积旋回由下部的块体搬运沉积体系和上部的水道-堤岸沉积体系构成.块体搬运沉积体系整体呈现为杂乱、半透明状的地震反射特征,底界面发育侵蚀沟谷,内部发育逆冲断层;水道-堤岸沉积体系整体表现为平行、连续同向轴的地震反射特征,局部半透明,发育弯曲水道、海鸥翼状堤岸、越岸沉积、决口扇和滑塌体.依据海底地形、重力流流动方向和中南半岛的山间河流分布推断越南中部山区是研究区的重力流物源,山间河流是主要的输送途径,指出陆架-陆坡的快速沉积物堆积是形成重力流沉积旋回的基本条件,探讨了海平面变化过程中的孔隙流体压力变化与重力流沉积体系类型之间的对应关系,并在理论上推测重力流旋回周期与更新世偏心率长周期(400~500 ka)的海平面变化一致.更多还原

【Abstract】 Three sediment cycles were identified by 3-D seismic data within early Pleistocene to present strata on the northwestern slope(15°30′00″–16°30′00″E) of the Qiongdongnan Basin. The sediment cycles are characterized by basal mass transport deposits(MTDs) overlain by channel-levee deposits(CLDs). MTDs are characterized by mounded, hummocky, chaotic, low amplitude, and discontinuous seismic reflection, with internal thrusts and basal grooves. CLDs exhibit parallel, continuous, and local translucent seismic reflection, with meandering channels, gull-wing and over-bank levees, crevasse splays, and slumps. Original sources were inferred as the mountains of central Vietnam by analyzing morphology, gravity fluid flow direction, and river distribution in the western region of the study area. The basic condition of sediment cycle formation is the high accumulation rate on the western margin shelf and slope of the Qiongdongnan Basin. Timing and mechanism of the sediment cycles suggest a causal link between pore pressure changes influenced by eccentricity scale(400–500 ka)sea-level change and sequential emplacement of MTDs and CLDs.更多还原