Professor WANG Erqi and his team use thermochronology to measure the cooling histories of rocks exposed in a section that stretches vertically over 3km adjacent to the Sichuan Basin. Their thermal models of exhumation-driven cooling show that these rocks, and hence the plateau margin, were subject to slow, steady exhumation during early Cenozoic time, followed by two pulses of rapid exhumation, one beginning 30-25 million years ago and a second 10-15 million years ago that continues to present.

Their findings imply that significant topographic relief existed adjacent to the Sichuan Basin before the Indo-Asian collision. Furthermore, the onset of Cenozoic mountain building probably pre-dated development of the weak lower crust, implying that early topography was instead formed during thickening of the upper crust along faults. They suggest that episodes of mountain building may reflect distinct geodynamic mechanisms of crustal thickening.

Fig. 1 Geologic map of the southern Longmen Shan range. (Image by WANG)

Fig. 2 Age-elevation relationships for thermochronologic data for the Pengguan Massif. (Image by WANG)

Wang et al. Two-phase growth of high topography in eastern Tibet during the Cenozoic. Nature Geoscience, 2012, doi: 10.1038/ngeo1538, Published online: 05 August 2012 (See More >>)