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 km高的青藏高原的发育。大部分的高原？的边缘是由陡峭的，断层为界的地形锋（如喜马拉雅山），但东南高原边缘是一个扩散的边界与主要断层平行的地形梯度。来自锡拉丘兹大学和罗切斯特大学的一个研究小组与中国藏学研究所的科学家合作，将利用保存在青藏高原东南边缘的沉积岩，研究该地区区域流域演化的历史和高地形的形成，该地区位于中国云南省昆明市附近。河流砂岩是流域上游侵蚀源区沉积物的混合物。砂岩中发现的锆石矿物的结晶年龄和热折返年龄范围提供了被侵蚀地区的指纹。已知沉积时代砂岩中锆石年龄特征的变化将被用来追踪河流网络侵蚀不同基岩源区时沉积物来源的变化。的表面条件随着时间的推移，他们形成。大气（降水和地表）水的氧同位素组成的变化，在一定程度上，对海拔高度敏感。大气降水的同位素组成记录在矿物和植物材料中，可以用来解释植物生长和/或矿物形成的地表高度。来自土壤微生物的有机质与植物的有机质不同，键的排列反映了土壤温度，这是另一个对海拔高度敏感的参数。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的变化。本研究的一个主要目标是重建青藏高原东南缘在过去4000万年的海拔历史。高程是一个关键的地球物理参数，是揭示地球形成过程的关键约束条件。这项研究将解决大陆构造学中一个主要的悬而未决的问题：高原边缘的扩散是如何形成的？青藏高原东南部边缘形成的主要假说之一认为，一个软弱的、塑性变形的下地壳从邻近的高原向边缘流动。通过揭示沉积物来源和海拔历史的变化，将有可能限制这种类型的高原边缘发展的时间，速度和过程，同时测试下地壳流动假说的可行性。该研究的结果将具有超越大陆构造的意义，因为假设青藏高原对全球气候具有重大影响。该项目得到了地球科学部构造项目和NSF国际科学与工程办公室东亚和太平洋项目的支持。

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.