In this study, Alka Tripathy-Lang and colleagues address the timing of collision between the Indian and Eurasian lithospheric plates, a process that formed arguably the most spectacular landform on earth -- the Himalayan-Tibetan orogenic system. They demonstrate that the source area for the Basgo Formation, a package of sedimentary rocks in NW India that lies within the zone of collision, includes material derived from both plates. Coarse cobbles came from the north, whereas finer sands came from the south. When presented with a mixed source region, the implication is that Eurasia (northern source) and India (southern source) were close enough to one another to contribute sediment to a common basin. The Indian source area specifically seems to be the paleo-Indian passive margin, which is analogous to the Atlantic margin of North America today. Additional study demonstrates that the Indian continental margin source region for the Basgo Formation had emerged from below sea level and was shedding sediments to the Basgo Formation by 50 million years ago as a consequence of India-Eurasia collision. This precludes collision having occurred at 35 million years. Instead, the data presented here support the hypothesis that collision commenced around 50 million years ago.
Transpressive uplift and exhumation of continental lower crust revealed by synkinematic monazite reactions
>Gregory Dumond, University of Arkansas, Geosciences, Fayetteville, Arkansas 72701, USA; and Michael L. Williams, and Michael J. Jercinovic; http://dx.doi.org/10.1130/L292.1.
Rare exposures of deep contine
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Geological Society of America