Evolution of Miocene Fluvial Environments in Northern Pakistan

对巴基斯坦北部Potwar高原中新世Siwalik沉积物的研究将继续进行。这包括在盆地的几个不同地区建立详细的沉积学记录，包括Chinji， Magri和Shok Pathan组，这些组有古地磁年龄测定。在每个测量的层序中，几个重要的50至100米厚的地层间隔将在几公里的横向上使用照片马赛克和紧密间隔（100米）的原木进行沉积学和古生物学上的详细记录。古土壤碳酸盐将被取样用于碳同位素分析。这将使我们能够从古河道几何和水力学、古土壤性质、动植物活动和沉积速率等方面重建时空变化的古环境。将特别注意：(1)上肖克-帕坦组（6mpBP），存在主要的气候、植被和动物变化的证据；(2)Chinji-Nagri过渡期（10 m.y.b.p.），存在主要的动物更替、沉积速率增加、河道沉积物比例和粒度增加、河道尺寸增大的证据；但没有气候变化的证据。这样就有可能了解陆地生物与物理和化学环境变化有关的一个重要进化时期。这项研究还将对河流沉积物（及其包含的化石）、构造和气候之间的关系产生更广泛的影响。

Research wil continue on the fluvial, Miocene Siwalik deposits of the Potwar Plateau in northern Pakistan. This involves construction of detailed sedimentological logs through the Chinji, Magri and Shok Pathan formations formations in several different parts of the basin where there is paleomagnetic age dating. Several important 50 to 100 m thick stratigraphic intervals in each measured sequence will be detailed sedimentologically and paleontologically over several km laterally, using photo mosaics and closely-spaced (100 m) logs. Paleosol carbonates will be sampled for Carbon isotope analysis. This will allow us to reconstruct the temporally and spatially varying paleoenvironments in terms of paleochannel geometry and hydraulics, nature of paleosols, animal and plant activity and deposition rates. Particular attention will be paid to: (1) the upper Shok Pathan Formation (6mpBP) where there is evidence for a major climatic, vegetational and faunal change and (2) the Chinji-Nagri transition (10 m.y.B.P.) where there is evidence of a major faunal turnover, increasing depositional rates, increasing proportion and grain size of channel deposits, and increasing channel size, but no evidence of a climatic change. 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. This study will also have more general implications for the relationship between fluvial deposits (and the fossils they contain), tectonism and climate.