Collaborative Research: Basin Evolution and Elevation History of the SE Margin of the Tibetan Plateau: Constraints on the Timing and Mechanisms of Surface Uplift

印度与亚洲的碰撞是板块构造中陆-陆碰撞的原型，并导致了5公里高的青藏高原的发育。高原-S边缘的大部分地区被陡峭的断层控制的地形前锋(如喜马拉雅山脉)所包围，而高原东南部边缘是一个弥漫的边界，主要断裂平行于地形梯度。来自锡拉丘兹大学和罗切斯特大学的一组研究人员将与中国藏族问题研究所的科学家合作，利用保存在青藏高原东南缘的沉积岩，研究位于云南昆明附近的这一地区的区域流域演化史和高地地形的形成。中国说。河流砂岩是来自流域上游侵蚀源区的沉积物的混合物。砂岩中发现的矿物锆石的结晶年龄和热剥离年龄范围提供了被侵蚀地区的指纹。已知沉积时代的砂岩中锆石年龄的变化将被用来追踪河流网络侵蚀不同的基岩物源区时沉积物来源的变化。矿物和植物有机质记录了有关地球-S形成时间的地表条件的信息。大气(降水和地表水)氧同位素组成的变化在一定程度上对海拔高度很敏感。大气降水的同位素组成记录在矿物和植物材料中，可以用来破译植物生长的地表高度和/或形成的矿物。土壤微生物的有机质不同于植物的有机质，键的排列反映了土壤温度，这是另一个对海拔敏感的参数。在垂直序列中，含有适当物质的沉积岩可以用来重建海拔随时间变化的情况。这项研究的一个主要目标是重建青藏高原东南缘4000万年来的高程历史。海拔，一个关键的地球物理参数，是解开地球-S地壳演化过程的关键约束。这项研究将解决大陆构造中的一个重大悬而未决的问题：高原的扩散边缘是如何形成的？青藏高原东南部边缘形成的主要假说之一表明，一个微弱的、塑性变形的下地壳从邻近的高高原向边缘流动。通过揭示沉积物来源和高程历史的变化，将有可能限制这种类型的高原边缘发育的时间、速度和过程，同时检验下地壳流动假说的可行性。这项研究的结果将超越大陆构造的影响，因为它假设青藏高原对全球气候有重大影响。该项目得到了地球科学部的构造计划和美国国家科学基金会国际科学与工程办公室的东亚和太平洋计划的支持。

The collision of India and Asia is the archetype of continent-continent collision in plate tectonics and is responsible for the development of the 5 km high Tibetan Plateau. Most of the Plateau?s margin is bounded by steep, fault-bounded topographic fronts (e.g. the Himalaya), yet the southeastern Plateau margin is a diffuse boundary with major faults that parallel the topographic gradient. A team of researchers from Syracuse University and the University of Rochester, in collaboration with scientists from the Chinese Institute for Tibetan Studies, will utilize sedimentary rocks preserved on the southeastern margin of the Tibetan Plateau to examine the history of regional drainage basin evolution and the formation of high topography in this area, located near Kunming, Yunnan Province, China. River sandstones are a mixture of sediment from erosional source regions upstream in a watershed. The range of crystallization age and thermal exhumation ages of the mineral zircon, found within sandstones, provides a fingerprint of the areas being eroded. Changes in the signature of zircon ages in sandstones of known depositional age will be used to trace the changes in sediment source as river networks eroded distinct bedrock source areas.Minerals and plant organic matter record information about earth?s surface conditions over the time in which they formed. The variation in the oxygen isotopic composition of meteoric (precipitation and surface) water is, in part, sensitive to elevation. The isotopic composition of meteoric water is recorded in mineral and plant material, and can be used to decipher the elevation of the ground surface where the plant grew and/or the minerals formed. The organic matter from soil microbes is distinct from that of plants, and the bond arrangement reflects soil temperature, another parameter sensitive to elevation. Over a vertical succession, sedimentary rocks containing appropriate material can be used to reconstruct how elevations changed over time. A principal goal of this research is to reconstruct the elevation history of the SE margin of the Tibetan Plateau over the past 40 million years. Elevation, a key geophysical parameter, is a critical constraint for unraveling the processes by which the earth?s crust evolves.This research will address a major outstanding question in continental tectonics: how do diffuse margins of plateaus form? One of the leading hypotheses for the formation of the southeastern Tibetan Plateau margin suggests that a weak, plastically deforming lower crust flows from the adjacent high Plateau toward the edges. By unraveling both the change in sediment sources and elevation history it will be possible to constrain the timing, rate and process by which this type of plateau margin develops, while at the same time testing the viability of the lower crustal flow hypothesis. The results of the study will have implications beyond continental tectonics, as it is hypothesized that the Tibetan Plateau has a major influence on global climate.This project is supported by the Tectonics Program in the Earth Sciences Division and the East Asia and Pacific Program in NSF's Office of International Science and Engineering.