琼东南盆地晚新生代陆架边缘陆坡生长沉积过程与体量计算

The continental shelf clinoforms of Qiongdongnan Basin margin, South China Sea, has grown since 10.5 Ma Late Cenozoic time, which generated more than 4km-thick shelf prism above the T40 surface. As the hub of the continental shelf, the shelf margin clinoform and trajectory show down-flatting and rising patterns where the progradation and aggradation of cross-shelf transits happened. By using the core, well drilling data, and estimation and calculation method based on 2D seismic lines, this study aim to: ① illustrate the clinoform patterns (including the shelf-edge trajectory and toe of slope trajectory) and the clinothem architectures and shapes through the vertical evolution of the delta regime with at least 5 main boundaries (T40, T30, T27, T20, T0) and 15 basic clinothem units; ② demonstrate the geometry morphology of the clinoforms and mechanism of the shelf margin accretion with the sediment flux calculation of each clinothem, which includes the estimation of sediment flux and volumes, and to exam the quantitative results and predicted ratio of the sediment flux across the shelf-edge; ③ reconstruct the source-to-sink system equilibrium from shelf through shelf margin to deepwater slope and basin floor with the discussion of the controls of sand transfer system on the shelf margin clinothem evolution and their interactions; ④ and furthermore, understand the responds of Cenozoic shelf margin sediment processes and flux to global transgressive-regressive events or climate cycles with the considering of factors of tectonic subsidence, accommodations, climate changes, and high frequency sea level changes during ice-house.

本研究围绕中国南海北部琼东南盆地陆架边缘斜坡的沉积过程，以T40界面之上晚新生代（10.5Ma以来）沉积的超过4km厚的海相地层为研究对象，探讨其进积-退积旋回及呈水平到上升趋势变化的陆架边缘轨迹特征。以岩芯、钻井、二维地震剖面为数据基础，通过沉积体系定量化表征方法，研究以下几方面的内容：①以5个主要界面及15个沉积斜坡基础单元为格架，阐明沉积斜坡几何形态与内部构成样式、进积-加积序列、生长演化过程及扩张机制；②计算各基础单元沉积物供给量和陆架/斜坡输砂比，及其定量化表征参数和预测结果；③对陆架边缘陆坡系统进行定量化重建，从而恢复陆架边缘作为系统枢纽的沉积过程，研讨盆地随时间变化的输砂系统对陆架边缘斜坡沉积演化的影响与动态制约关系。④查明外源控制因素（构造沉降、可容纳空间变化、冰期高频高振幅海平面变化、海相盆地古气候变化）对陆坡生长沉积过程与体量变化的影响与控制作用。

本研究围绕中国南海北部琼东南盆地陆架边缘斜坡的沉积过程，以T40界面之上晚新生代（10.5Ma以来）沉积的超过4km厚的海相地层为研究对象，探讨陆架边缘沉积斜坡演化特征及沉积物供给量变化规律。以岩芯、钻井、二维、三维地震为数据基础，通过沉积体系定量化表征方法，研究以下几方面的内容：①以5个主要界面及15个沉积斜坡基础单元为格架，通过研究沉积斜坡进积-退积旋回及呈水平到上升趋势变化的陆架边缘轨迹特征，阐明沉积斜坡几何形态与内部构成样式、进积-加积序列、生长演化过程及扩张机制；②通过定量化表征参数，计算各基础单元沉积物供给量和陆架/斜坡输砂比的预测结果；③对陆架边缘陆坡系统进行定量化重建，从而恢复陆架边缘作为系统枢纽的沉积过程，研讨盆地随时间变化的输砂系统对陆架边缘斜坡沉积演化的影响与动态制约关系。阐明2-4Ma以来增加的沉积物体量与减小的沉积物粒度之间的关联性。研究结果表明增加的沉积速率和明显增加的泥质含量可能与长距离搬运的泥质沿岸流有关，与此同时，横向上，自西向东沉积物供给量有明显减小的趋势，与之伴随的是同样减小的陆架边缘输砂百分率。陆架边缘几何形态由西部的进积-加积型向东部的加积型转变。琼东南盆地陆架边缘晚新生代以来的生长演化反映了在全球冰期海平面和温度呈降低趋势的背景下高频高振幅古气候变化对陆坡生长沉积过程与体量变化的影响与控制作用。