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Denudation outpaced by crustal thickening in the eastern Tianshan

Charreau, J. et al., EPSL

Denudation outpaced by crustal thickening in the eastern Tianshan

Charreau, J. ; Saint-Carlier, D. ; Dominguez, S. ; Lavé, J. ; Blard, P.H. ; Avouac, J.P. ; Jolivet, M. ; Chen, Y. ; Wang, S. ; Brown, N.D. ; Malatesta, L.C. ; Rhodes, E. ; ASTER Team

Earth and Planetary Science Letters, 2017, 479, 179-191

Abstract :

The modern high topography of the Tianshan resulted from the reactivation of a Paleozoic orogenic belt by the India/Asia collision. Today, the range exhibits tectonically active forelands and intermontane basins. Based on quantitative morphotectonic observations and age constraints derived from cosmogenic 10Be dating, single-grain post-infrared infrared stimulated luminescence (p-IR IRSL) dating and modeling of fault scarp degradation, we quantify the deformation in the Nalati and Bayanbulak intermontane basins in the central Eastern Tianshan. Our results indicate that at least 1.4mm/yr of horizontal crustal shortening is accommodated within these two basins. This shortening represents over 15% of the 8.5 ±0.5mm/yr total shortening rate across the entire range at this longitude. This shortening rate implies that the Eastern Central Tianshan is thickening at a mean rate of ∼1.4mm/yr, a rate that is significantly higher than the average denudation rate of 0.14mm/yr derived from our cosmogenic analysis. This discrepancy suggests that the Tianshan range has not yet reached a steady-state topography and remains in a transient state of topographic growth, most likely due to limited denudation rates driven by the arid climate of Central Asia.




publié vendredi 8 décembre 2017