Detrital Record of the Eastern Himalaya, Assam and Bengal Basin

小行星9419086 最近对喜马拉雅山的研究表明，显著的地壳缩短、变质、隆起和侵蚀早在中新世中期和更年轻的记录之前就开始了，这些记录在西瓦利克和远孟加拉扇中有很好的记载。 本项目拟通过分析始新世晚期碎屑地质年代学和矿物学，通过阿萨姆邦和孟加拉盆地最近暴露和钻探的地层，调查喜马拉雅东部造山作用和构造沉积作用的约束不良的启动和随后的历史。 这些地层代表了一个缺失的环节，在一个活跃的碎屑楔，已被用于造山沉积和碰撞模型的启发，但他们仍然几乎未开发的造山和侵蚀过程的地层信息。 本研究的目标包括：（1）确定喜马拉雅山东部快速去顶的开始和评估快速去顶的时间和/或区域模式，（2）区分孟加拉盆地3个主要河流系统的沉积物输入，（3）评估主要流域沉积物源的变化。 碎屑颗粒的冷却年龄将受到锆石裂变径迹分析的约束，并辅以18 Ma前地层中选定层位的钾长石40 AR/39 Ar定年。 碎屑成分将通过确定砂（石）模式进行分析，特别是侧重于岩屑和重矿物种群，辅以电气石，石榴石和角闪石的微探针分析。 主要河流系统的沉积物输入将使用现实主义的方法进行记录，从恒河、雅鲁藏布江和梅克纳河（及相关）的现代砂开始，并通过新生代层序进行回溯，以评估自喜马拉雅山形成以来源岩的变化。 该项目的意义在于，在喜马拉雅山东部的foredee p，这提供了一个机会，以重建造山作用和表面过程，从西瓦利克和远孟加拉扇研究的数据地层，以及评估沿走向和下游的变化，沉积物成分在新近纪的一部分，这个巨大的碎屑楔。 该项目的最终目标是提高对现代大陆碰撞中构造和表面过程的认识。 拟议的地质年代学和成分分析，辅以改进的地层控制和相关的正在进行的研究，将扩大现有的数据集，通过整个喜马拉雅山的发展，提供必要的地面实况评估模型的碰撞过程。

9419086 Lundberg Recent work on the Himalaya suggest that significant crustal shortening, metamorphism, uplift and erosion began well before the mid-Miocene and younger record that has been well documented in the Siwaliks and distal Bengal fan. This project proposes to investigate the poorly-constrained initiation and ensuing history of orogenesis and tectonic sedimentation in the eastern Himalaya, by analyzing detrital geochronology and mineralogy of late Eocene through Recent strata exposed and drilled in Assam and the Bengal basin. These strata represent a missing link in an active clastic wedge that has been used to exemplify orogenic sedimentation and to inspire collisional models, yet they remain virtually unexploited for stratigraphic information on mountain-building and erosional processes. The objectives of this research include (1) determining the onset of rapid unroofing and evaluating temporal/and or regional patterns in rapid unroofing in the eastern Himalayas, (2) distinguishing sediment input from 3 major river systems that join in the Bengal basin, and (3) evaluating changes in sediment source terranes in the major drainages through time. Cooling ages of detrital grains will be constrained by fission-track analysis of zircon, complemented by 40AR/39Ar dating of potassium feldspar from selected horizons in pre-18 Ma strata. Detrital composition will be analyzed by determining sand (stone) modes, especially focusing on lithic fragments, and heavy-mineral populations, complemented by microprobe analyses of tourmalines, garnets, and amphiboles. Sediment input from the major river systems will be documented using an actualistic approach, beginning with modern sands from the Ganges, Brahmaputra, and Meghna (and related) rivers, and working back through Cenozoic sequences to assess changes in source rocks since inception of the Himalaya. The significance of this project lies in the largely unexploited stratigraphic record accessible onland in the eastern Himalayan foredee p, which provides the opportunity to reconstruct orogenesis and surface processes that pre-data strata studied from the Siwaliks and the distal Bengal fan, as well as to evaluate along-strike and downstream changes in sediment composition in the Neogene part of this immense clastic wedge. The ultimate objective of this project is to improve understanding of tectonic and surface processes in a well-constrained modern continental collision. The proposed geochronologic and compositional analyses, complemented by improved stratigraphic control and related ongoing studies, will extend existing data sets through the entire development of the Himalaya, providing ground truth necessary for evaluating models of collisional processes.