The Sylhet Trough, a petroleum province of the Bengal Basin, accommodates a huge thickness of Eocene to Recent sedimentary successions. However, the basin-fill history of the trough is poorly understood; specifically, constrains on timing of deposition of the individual units are yet to be established. Therefore, we aimed at establishing sedimentation and basin-fill history of the Sylhet Trough based on detailed lithofacies analysis of the outcropping Cenozoic succession. We have divided the entire Cenozoic succession into three megasequences which can be further sub-divided into nine lithostratigraphic units based on bounding discontinuities, such as transgressive erosion surface, regressive erosion surface, transgressive surface, marine flooding surface, and incised valley floor. The oldest is the Megasequence 1, comprised of shallow marine shelfal deposits overlain by shallow marine to nearshore deposits. In the middle, the Megasequence 2 is representing tide-dominated marine to coastal (deltaic) depositional systems with evidence of cyclic marine regression and transgression. Repetitive occurrence of incised channel, tidal inlet, tidal ridge/shoal, tidal flat and other tidal deposits are separated by shelfal deposits. The top of the Megasequence 2 is marked by a pronounced erosion surface interpreted as an incised valley floor indicating the final phase of marine regression followed by the gradual establishment of the overlying continental-fluvial depositional systems (i.e., the Megasequence 3). This youngest megasequence is characterized by stacked braided river sand bars that pass up-sequence into meandering river deposits. Based on the Cenozoic eustatic sea level curve, we suggest that the upper boundaries of the Megasequence 1 and Megasequence 2 are approximately at 39.5 Ma and 5.0 Ma, respectively.

孟加拉盆地的一个石油省Sylhet槽，可容纳厚厚的始新世至最近的沉积演替。但是，人们对槽的盆地填充历史知之甚少。具体而言，尚未确定各个单元的沉积时间的限制。因此，我们基于露头新生代的详细岩相分析，旨在建立锡尔赫特海槽的沉积和盆地充填历史。我们已将整个新生代演替过程划分为三个大的层序，根据边界不连续性，可以将其进一步细分为九个岩石地层学单位，例如海侵侵蚀面，海蚀侵蚀面，海侵面，海洋洪水面和切开的谷底。最古老的是Megasequence 1，由浅海陆架沉积物组成，覆盖在浅海相至近岸沉积物上。在中间，Megasequence 2代表了潮汐主导的海洋到海岸（三角洲）沉积系统，并具有周期性海洋退缩和海侵的证据。重复出现的切槽，潮汐入口，潮汐脊/浅滩，潮滩和其他潮汐沉积物被架子沉积物隔开。Megasequence 2的顶部有一个明显的侵蚀面，被解释为一个切开的谷底，表明海洋退缩的最后阶段，随后逐步建立了上覆的大陆河流沉积系统（即Megasequence 3）。这种最年轻的巨型层序的特征是堆积的编织河沙洲，这些河沙洲将上游序列带入蜿蜒的河床。