PROVENANCE AND DEFORMATION OF SANDSTONE AND THE HISTORY OF TRANSTENSION IN YUNNAN, CHINA

The Indian and Eurasian plates collided about 50 Ma, causing deformation throughout the Tibetan Plateau which continues today. Recent GPS measurements show eastward extension of central Tibet and extrusion towards the Southeastern Tibetan Plateau, where the elevation gradually decreases from the high plateau. Seismic studies and numerical modeling suggest that the middle crust is weak in these regions as well, likely due to the high elevation of the Tibetan Plateau. These observations have led to models of lower crustal flow and extrusion toward the east. Normal faulting in the Tibetan Plateau began at 18 Ma, but the onset of modern transtension in the Southeastern Tibetan Plateau and its relation to extension in the rest of the plateau is unclear. We conducted preliminary field work in Yunnan, China to investigate the deformational history. Here, we examine sandstone samples from western Baoshan, eastern Dehong, and northern Dali for petrographic. Additionally, U-Pb zircon geochronology helps constrain the age and provenance of these rocks and provide a maximum age for their deformation. Combining these methods will help constrain the onset of transtension in Yunnan and its relationship to the extension of Tibet.