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Late miocene intensified tectonic uplift and climatic aridification on the northeastern Tibetan plateau : Evidence from clay mineralogical and geochemical records in the Xining Basin

Yang, R. ; Yang, Y. ; Fang, X. ; Ruan, X. ; Galy, A. ; Ye, C. ; Meng, Q. ; Han, W., G-cubed

Late miocene intensified tectonic uplift and climatic aridification on the northeastern Tibetan plateau : Evidence from clay mineralogical and geochemical records in the Xining Basin

Yang, R. ; Yang, Y. ; Fang, X. ; Ruan, X. ; Galy, A. ; Ye, C. ; Meng, Q. ; Han, W.

Geochemistry, Geophysics, Geosystems, 2019, 20

Abstract :

The uplift of the Tibetan Plateau (TP) during the late Cenozoic is thought to be one of crucial factors controlling Asian climate. However, the complex interaction between tectonics and climate change is still unclear. Here we present the first record of clay mineralogy and elemental geochemistry covering 12.7–4.8 Ma in a fluvial‐lacustrine sequence in the Xining Basin. Geochemical provenance proxies (Th/Sc, Zr/Sc, and Cr/Zr) in the <2‐μm fraction show a significant provenance change at 8.8 Ma. Silicate‐based weathering indexes (CIA, CIW, and PIA) displayed coeval changes with provenance but discrepant changes with regional climate. Since the clay mineralogy exhibits significant change at 7.8 Ma uncorrelated with modifications in provenance, it can be employed to reveal regional climate change. The rise in illite and associated decrease in the sum of smectite and illite/smectite mixed layers reflect gradual and slow aridification since 12.7 Ma with intensified drying since 7.8 Ma until approaching the modern climate status. Our results, together with other regional climatic and tectonic records, clearly illustrate that accelerated uplift of the northeastern TP since 8–9 Ma has mainly modulated the regional erosion, weathering, transportation, and sedimentation and amplified the global cooling and drying trend toward the regional climate of modern conditions. Our study suggests that in the tectonically active northeastern TP, a comprehensive mineralogical and geochemical investigation of the fine‐grained fraction of the basin sediments could retrieve the interactions between tectonics and climate behind the complex change in exhumed lithology and sedimentary routing systems.

Voir en ligne : https://doi.org/10.1029/2018GC007917




publié mercredi 13 février 2019