40Ar/39Ar mica dating of late Cenozoic sediments in SE Tibet: implications for sediment recycling and drainage evolution

Xilin Sun, KF Kuiper, Yuntao Tian, Zengjie Zhang, L Gemignani, Rujun Guo, HL Vincent, JR Wijbrans

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Abstract

The Indo-Asia collision significantly changed the topography and drainage network of rivers around the Tibetan Plateau. Debate continues as to when and how the current drainage system of the Yangtze River was formed. Here we use 40Ar/39Ar dating of detrital micas (muscovite and biotite) to constrain provenances of the Pliocene sediments from the Jianchuan and Yuanmou basins in SE Tibet. Muscovite and biotite data of the same Pliocene samples from the Jianchuan Basin suggest contrasting distal v. local sources, respectively. Similarly, muscovite data of the Yuanmou Basin suggest a derivation of sediments from the Yalong River, but the characteristics of the Pliocene cobbles (palaeocurrent and subrounded cobbles) suggest that these sediments are locally sourced. Sediment reworking is proposed as an explanation for the different sediment provenance signals in the Jianchuan and Yuanmou basins that have led to the controversy of an either Pleistocene or pre-Miocene age of formation of the current Yangtze. Based on sediment provenance constraints, the evolution of the Jinsha River is reconstructed. The upper Jinsha River lost its connection with the southward flowing Red River upstream from the Jianchuan basin at least before the Pliocene. At the same time a parallel site in the Yuanmou Basin shows that the Yalong River stopped flowing southward into this basin. Detrital mica from early Pleistocene sediments at the Panzhihua site between the Jianchuan and Yuanmou basins is sourced from the current Jinsha and Yalong rivers. These results would suggest that the current upper Yangtze drainage system should have been established before the Pliocene.
Original languageEnglish
Pages (from-to)843-854
Number of pages12
JournalJournal of the Geological Society
Volume177
Issue number4
Early online date17 Feb 2020
DOIs
Publication statusPublished - Jul 2020

Funding

This study was financially supported by the National Natural Science Foundation of China (41671011, 41672355, 41772211 and 41801003), the Guangdong Province Introduced Innovative R&D Team (2016ZT06N331) and the Fundamental Research Funds for the Central Universities (19lgjc03 and 19lgpy72). K.K. is supported by NWO-ALW grant 864.12.005. This work was supported by the argon geochronology laboratory of the Vrije Universiteit Amsterdam.

FundersFunder number
Guangdong Province Introduction of Innovative R&D Team2016ZT06N331
National Natural Science Foundation of China41772211, 41672355, 41801003, 41671011
Nederlandse Organisatie voor Wetenschappelijk Onderzoek864.12.005
Fundamental Research Funds for the Central Universities19lgjc03, 19lgpy72

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