Erosion in northwest Tibet from in-situ-produced cosmogenic Be-10 and Al-26 in bedrock.

• Published in: Earth Surface Processes and Landforms
• Main Authors: Kong, P, Na, CG, Fink, D, Ding, L, Huang, FX
• Format: Article in Journal/Newspaper
• Language: English
• Published: John Wiley & Sons 2007
• Subjects: Erosion; Tibet; Beryllium; Aluminium; Tectonics; In-Situ Processing; Antarc*; Antarctica
• Online Access: http://apo.ansto.gov.au/dspace/handle/10238/1916; https://doi.org/10.1002/esp.1380

Concentrations of in-situ-produced cosmogenic nuclides Be-10 and Al-26 in quartz were measured by accelerator mass spectrometry for bedrock basalts and sandstones located in northwest Tibet. The effective exposure ages range between 23 and 134 ka (Be-10) and erosion rates between 4.0 and 24 mm ka(-1). The erosion rates are significantly higher than those in similarly and Antarctica and Australia, ranging between 0.1 and 1 mm ka(-1), suggesting that precipitation is not the major control of erosion of landforms. Comparison of erosion rates in and regions with contrasting tectonic activities suggests that tectonic activity plays a more important role in controlling long-term erosion rates. The obtained erosion rates are, however, significantly lower than the denudation rate of 3000-6000 mm ka(-1) beginning at c. 53 Ma in the nearby Godwin Austen (K2) determined by apatite fission-track thermochronology. It appears that the difference in erosion rates within different time intervals is indicative of increased tectonic activity at c. 5-3 Ma in northwest Tibet. We explain the low erosion rates determined in this study as reflecting reduced tectonic activity in the last million years. A model of localized thinning of the mantle beneath northwest Tibet may account for the sudden increased tectonic activity at c. 5-3 Ma and the later decrease. © 2006, John Wiley & Sons Ltd.