COLLABORATIVE RESEARCH: Holocene Evolution of the Ganges-Brahmaputra Delta: Implications of Floodplain/Delta Plain Development for Deltaic Models

Kuehl基金被要求进行为期两年的合作研究，以研究恒河-雅鲁藏布江三角洲的全新世演化。恒河-雅鲁藏布江（G-B）水系每年携带10亿吨沉积物，然而，像世界上大多数河流一样，这些物质经过上游监测站后的命运尚不清楚。这项研究将验证这样一个假设，即至少有一半的河流泥沙负荷被隔离在洪泛区和三角洲平原上，从而导致与经典三角洲模型明显不同的演化和相结构。恒河、雅鲁藏布江以及其他河流系统中如此大规模的沉积物封存，对我们理解河流颗粒向世界海洋的全球通量具有重要意义。本研究的具体目标是：1)建立全新世洪泛平原/三角洲平原的沉积预算；2)详细描述位于雅鲁藏布江前期的大型构造盆地Sylhet的地层结构和填充历史；3)描述孟加拉盆地其他部分（包括小子盆地和bil（湿地）地区）近期洪泛平原沉积的性质和规模；4)确定三角洲平原沉积的地层结构和规模，重点研究恒河的潮汐分流河道；5)将上述1-4的结果与我们之前的近海研究联系起来，建立一个晚全新世G-B三角洲演化的整体概念模型。在旱季，将从洪泛平原和三角洲平原收集深钻孔（~100 m）和岩心，以建立沉积物收支和约束地震观测。在夏季季风期间，当盆地被深度淹没时，将在Sylhet盆地进行基于水的高分辨率地震反射研究，以详细描述晚全新世盆地充填的地层学。对从河漫滩和三角洲平原收集的岩屑进行年代学和沉积学研究，将使我们能够确定G-B体系现存沉积环境的沉积过程速率和地层结构。上述任务的完成将使我们能够构建一个三角洲演化的概念模型，该模型将代表三角洲类型的重要末端成员，其中漫滩/三角洲平原沉积物的隔离可能起主要作用。除了上述的地质和全球影响之外，在这项研究中获得的对最近三角洲演化的理解将有助于为世界上人口最密集的低洼地区之一的发展制定合理的战略

9706274 Kuehl Funds are requested for a two-year collaborative study to examine the Holocene evolution of the Ganges-Brahmaputra delta. The Ganges-Brahmaputra (G-B) river system carries a billion tonnes of sediment annually, yet the fate of this material past the upstream gauging stations, as in most of the world's rivers, is not known. This study will test the hypothesis that at least half of the rivers' sediment load is being sequestered in the floodplain and delta plain, resulting in an evolution and facies architecture significantly different from classic deltaic models. Such magnitude of sediment sequestering, in the Ganges Brahmaputra as well as in other river systems, has important implications for our understanding of the global flux of riverine particulates to the world ocean. The specific objectives of this study are to: 1) Construct a sediment budget for the Holocene floodplain/delta plain: 2) Detail the stratigraphic architecture and history of infilling for the Sylhet, a large tectonic basin located along the previous course of the Brahmaputra: 3) Characterize the nature and magnitude of recent floodplain sedimentation in other portions of the Bengal Basin, including small sub-basins, and bil (wetland) areas; 4) Determine the stratigraphic architecture and magnitude of delta plain sedimentation, focusing on the tidal distributary channels of the Ganges; and 5) Link results from 1-4 above with our previous offshore studies to develop a holistic conceptual model for G-B delta evolution during the Late Holocene. Deep borings (~100 m) and cores will be collected from the floodplain and the delta plain during the dry season in order to construct the sediment budget and to constrain seismic observations. Water-based, high-resolution seismic-reflection studies would be conducted in the Sylhet Basin during the summer monsoon, when the basin is deeply flooded, in order to detail the stratigraphy of the Late Holocene basin fill. Geochronological and sedimentological studies of cor es collected from the floodplain and delta plain will enable us to determine the sediment process rates and stratigraphic architecture of extant sedimentary environments for the G-B system. The completion of the above tasks will enable us to construct a conceptual model of deltaic evolution which will represent an important end-member for deltaic styles, one for which floodplain/delta plain sediment sequestering likely plays a major role. In addition to the aforementioned geological and global implications, the understanding of recent deltaic evolution attained during this study would contribute to a rational strategy for development of one of the most densely populated, low-lying areas of the world