【摘要】 利用三维地震资料对若开盆地上中新统-上新统深水重力流沉积进行了层序地层划分。以海侵-高位域泥岩连续弱反射顶界以及大套水道侵蚀及朵叶体的底界作为三级层序界面,将上中新统—海底地层划分为3个三级层序,分别对应于上中新统、上新统及更新统-海底。以上中新统-上新统为重点研究对象,根据沉积单元的垂向组合特征,将上中新统划分为3个四级层序,上新统划分为2个四级层序,每个四级层序均表现为向上粒度变细、侵蚀减弱、砂岩减少的正韵律特征。三级层序界面基本上与该地区大规模海退相对应,四级层序界面基本上对应于小规模海退面。层序地层发育主要受海平面变化、构造抬升及气候的影响。海平面的周期性变化影响了沉积作用的变化,构造和气候控制沉积物供给量,供给量的不同造成不同四级层序叠加样式不同。此外,构造抬升对该地区气候产生一定的影响,尤其7~8 Ma,青藏高原的快速隆起增强了南亚季风,并使得剥蚀量增加,沉积物供给量增加,朵叶体及水道发育程度增加。更多还原

【Abstract】 High resolution 3D seismic data were used for the sequence stratigraphy division of the Upper Miocene-Pliocene deepwater gravity flow deposits in Rakhine Basin,Myanmar. Taking the continuous weak reflections of the TST-HST mudstones and the base of the thick channel incision and lobe sandstones as the third-order sequence boundaries,the upper Miocene-seabed deposits were divided into three third-order sequences,corresponding to the Upper Miocene,Pliocene and Pleistocene-seabed respectively. The Upper Miocene and Pliocene were selected as the focus of this study and were subdivided into three and two fourth-order sequences respectively according to the vertical evolution characteristics of the deepwater architectural elements. Each fourth-order sequence shows similar positive rhythm features of upward decreasing grain size,weakening denudation and lowering sand-to-gross ratio. The third-order sequence boundaries were caused by the regional large marine regressions,while the fourth-order sequence boundaries were resulted from the small-scale marine regressions. The development of sequence stratigraphies was mainly controlled by the sea level change,tectonic uplifting and climate. The sea level change influenced the deposition variation. And the tectonic uplifting and the climate controlled the sediment supply volume which affected the stacking styles of the fourth-order sequence. Especially during 7-8 Ma,the rapid uplifting of the Tibetan strengthened the south Asian monsoon,intensified erosion,and thus increased sediment supply. Consequently,the lobe sandstones increased and the channel incision strengthened during 7- 8 Ma.更多还原