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.
