孟加拉湾若开盆地深水沉积体系结构单元类型及演化模式

利用多个地震数据体的地震反射特征,分析了孟加拉湾若开盆地深水沉积体系的不同沉积结构单元类型(峡谷、水道及水道复合体、天然堤—漫溢沉积、朵体以及块体搬运沉积)的典型地震响应特征、及其发育的位置,构建了研究区陆架—陆坡—盆底的沉积结构单元演化模式。研究表明,一个深水沉积体系垂向上自下而上的组合样式为:底部块体搬运沉积及厚层大规模朵体沉积,上覆水道复合体沉积,之后为水道—天然堤复合体沉积、以及一些小规模朵体沉积,顶部为薄层深海泥岩沉积。横向上自陆架向深海盆地的发育模式表现为:陆架/上陆坡峡谷—上陆坡侵蚀型水道—下陆坡侵蚀沉积型水道—沉积型水道—盆地朵体。

Structural Units and Evolution Model of Deepwater Depositional System in Rakhine Basin,Bay of Bengal

Structural units of a deepwater depositional system are canyons, channels or channel complexes, levee-overbank, lobes and mass-transport deposits. By means of the seismic reflection data from different areas in Rakhine Basin, Bay of Bengal, the typical seismic response characteristics and developing locations of different structural units are analyzed to establish a evolution model of the deepwater structural units from the shelf through the slope and the basin. It is indicated that a deepwater sediment system evolves upwards from the base as follows:(1) mass-transport deposits and a large-scaled thick lobe at the base, (2) an overlying channel complex at the lower part, (3) a channel-levee complex or a small-scaled lobe in the middle-upper part, and (4) capping thin abysmal sea mudstone at the top. In lateral, the deepwater sediment system is composed of shelf/upper slope canyon, upper slope erosive channel, lower slope erosive-depositional channel, depositional channel and basin-floor lobes from the shelf to the basin.