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首页> 外文期刊>Journal of Asian earth sciences >Geologic, Geomorphic And Hydrologic Framework And Evolution Of The Bengal Basin, India And Bangladesh
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Geologic, Geomorphic And Hydrologic Framework And Evolution Of The Bengal Basin, India And Bangladesh

机译：孟加拉盆地，印度和孟加拉国的地质，地貌和水文框架及其演化

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The Bengal basin, the largest fluvio-deltaic sedimentary system on Earth, is located in Bangladesh and three eastern states of India. Sediment accumulates in the basin from the Ganges, Brahmaputra, and Meghna (GBM) river systems and is dispersed into the Bay of Bengal, forming the largest submarine fan in the world. The basin is located in the Himalayan foreland at the junction of the Indian, Eurasian, and Burmese plates. The basin is bounded by the Indian craton on the west and the Indo-Burmese fold belts on the east. It can be broadly divided into a stable shelf and a foredeep separated by a deep seismic hinge zone. Basin sediments overlie Gondwanan basement and vary in thickness from a few kilometers on the stable shelf to more than 16 km in the foredeep. The basin was initiated at the breakup of Gondwanaland in the late Mesozoic and evolved through the formation of the proto-GBM delta to the present delta starting around 10.5 Ma. The stratigraphy of the different parts of the basin differs considerably, because of contrast in depositional history within the several sub-basins that were produced by intra-plate tectonic activities associated with ongoing Himalayan orogeny. The present-day geomorphology is dominated by the extensive Holocene GBM floodplain and delta. The vertical succession of the deltaic plain can be classified into five units on the basis of differences in grain size, which reflect differing depositional environments. The initiation of the modern GBM delta at the onset of the Pleistocene glacial maximum and its evolution to the present configuration are intricately related to Holocene fluvio-dynamic processes, eustatic sea-level changes, and tectonic movements. The sedimentology and mineralogy of the different parts of the basin reflect differences in sediment provenance. The mineralogy is dominated by detrital quartz, some feldspar, and minor amounts of carbonates; illite and kaolinite are the main clay minerals. The basin has profuse groundwater resources, but the architecture of the aquifers is not yet well resolved. Different classification schemes have been proposed on the basis of lithology. Regional groundwater flow follows a low hydraulic gradient from north to south, but pumping for irrigation during the past several decades appears to have severely distorted regional flow. Recharge occurs primarily during the monsoon season. Groundwater chemistry is dominated by anoxic, Ca-HCO_3-type water with relatively high concentrations of Fe, Mn, and As. Carbonate dissolution, silicate weathering, FeOOH reduction, and mixing with saline water are the primary processes controlling hydrochemistry.
机译：孟加拉盆地是地球上最大的河流-三角洲沉积系统，位于孟加拉国和印度的三个东部州。沉积物从恒河，雅鲁藏布江和梅格纳河（GBM）河系积聚在盆地中，并分散到孟加拉湾，形成了世界上最大的海底扇。盆地位于印度，欧亚和缅甸板块交界的喜马拉雅前陆。该盆地的西部是印度克拉通，东部是印度-缅甸褶皱带。它可以大致分为稳定的架子和由深地震铰链区分开的前深层。盆地沉积物覆盖在冈瓦南基底上，其厚度从稳定架上的几公里到前深处的超过16公里不等。该盆地始于中生代晚期冈瓦纳（Gonwanaland）破裂，并通过原始GBM三角洲的形成演化到大约10.5 Ma左右的三角洲。盆地不同部分的地层差异很大，这是由于与持续的喜马拉雅造山作用有关的板内构造活动所产生的几个次盆地内沉积历史的对比。当今的地貌以全新世GBM泛滥平原和三角洲为主。根据晶粒大小的差异，三角洲平原的垂直演替可以分为五个单位，这反映了不同的沉积环境。现代GBM三角洲在更新世冰川期开始时的萌发及其向当前构造的演变与全新世河流动力学过程，海平面欣喜变化和构造运动错综复杂。盆地不同部分的沉积学和矿物学反映了沉积物来源的差异。矿物学主要由碎屑石英，一些长石和少量碳酸盐组成。伊利石和高岭石是主要的粘土矿物。流域拥有丰富的地下水资源，但含水层的结构尚未得到很好的解决。已经根据岩性提出了不同的分类方案。从北部到南部，区域地下水流量遵循低水力梯度，但是在过去的几十年中，用于灌溉的抽水似乎严重扭曲了区域流量。补给主要发生在季风季节。地下水化学成分主要是缺氧的Ca-HCO_3型水，其中铁，锰和砷的浓度相对较高。碳酸盐溶解，硅酸盐风化，FeOOH还原以及与盐水混合是控制水化学的主要过程。

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