Evolution of Miocene Fluvial Environments in Northern Pakistan

本文对巴基斯坦北部Potwar高原中新世Siwalik沉积进行了详细的沉积学研究。从古河道和洪泛平原的几何和水力学、湖泊水体的化学、古土壤的性质、动植物活动的分布、河流改道和沉积速率等方面重建时空变化的河流古环境。这些特征的变化将与局部、区域和/或全球控制因素有关，包括气候、构造运动和沉积物供应。这样就有可能了解陆地生物在14到7个B.P.之间的重要演化时期与物理和化学环境变化的关系。Siwalik矿床为实现这些目标提供了无与伦比的机会，因为：1)3000米以上地层的极好三维暴露；2)岩石地层学、脊椎动物古生物学、古地磁测年的前期研究；3)利用现有地质资料对沉积盆地以外地区的气候变化和构造活动进行独立约束。了解河流沉积物（包括它们所含的化石）在构造和气候作用下的演化，对全世界所有时代的岩石都有意义。这些知识具有经济意义，因为河流沉积物通常是水、石油和天然气的储藏库，也是煤、金、铀和建筑材料的来源。

A detailed sedimentological study of the Miocene Siwalik deposits of the Potwar Plateau in northern Pakistan is proposed. Temporally and spatially varying fluvial paleoenvironments will be reconstructed in terms of paleochannel and floodplain geometry and hydraulics, chemistry of lacustrine waters, nature of paleosols, distribution of animal and plant activity, river diversions, and deposition rates. Changes in these characters will be related to local, regional and/or global controls including climate, tectonism, and sediment supply. It will then be possible to understand an important period of evolution of land organisms in relation to changes in the physical and chemical environment over a period between 14 and 7 my B.P. The Siwalik deposits offer an unparalleled opportunity to realise these objectives because of: 1) excellent 3-D exposures of 3000 m + of strata; 2) previous studies of lithostratigraphy, vertebrate paleontology, and paleomagnetic age-dating; 3) independent constraints on climatic change and tectonic activity using geologic data now available for areas outside the depositional basin. Understanding of the evolution of fluival deposits (including the fossils they contain) in response to tectonism and climate has implications for rocks of all ages worldwide. Such knowledge has economic implications because fluival deposits are commonly reservoirs for water, oil, and gas, also are sources of coal, gold, uranium, and building materials.