Sedimentary provenance constraints on drainage evolution models for SE Tibet: Evidence from detrital K‐feldspar

• Published in: Geophysical research letters 2017-05, Vol.44 (9), p.4064-4073
• Main Authors: Zhang, Zengjie, Daly, J. Stephen, Li, Chang'an, Tyrrell, Shane, Sun, Xilin, Yan, Yi
• Format: Article
• Language: English
• Subjects: Age; Archives & records; Cenozoic; Chemical composition; Constraint modelling; Data; Deposits; detrital K‐feldspar; Drainage; drainage evolution; Drainage patterns; Eocene; Evolution; Feldspars; Fluvial deposits; Grains; Isotope composition; Isotopes; Jinsha River; Lake deposits; Light; Pb isotopes; Plateaus; Pleistocene; Pliocene; Provenance; Rivers; Sediment; Sequencing; Studies; Transport; Transportation models; Uplift
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2017GL073185

The unusual drainage pattern of the Jinsha River (upper Yangtze) is closely linked to the uplift of the Tibetan Plateau, but when this pattern became established is controversial. In this study we compare the Pb isotopic composition of detrital K‐feldspars from the modern Jinsha River with those from the Plio‐Pleistocene Xigeda Formation, a sequence of fluvial and lacustrine deposits widely distributed along the major rivers draining the Tibetan Plateau, to investigate their relationship and to constrain the drainage evolution of the region. Our results demonstrate that the Jinsha River had achieved its current sediment‐transport pattern by the late Pliocene, indicating a drainage character similar to that operating at present. Our findings not only suggest an upper age limit for formation of the Jinsha River but also shed new light on the evolution of the whole Yangtze system. K‐feldspar grains from the Jinsha River have less radiogenic Pb than those in the Red, Mekong, and Salween Rivers, providing a key test as to whether the Jinsha River was previously connected to the paleo‐Red River. Comparison with published Pb isotopic data shows that these characteristically unradiogenic feldspars are absent in the onshore Cenozoic archive from the Hanoi Basin, suggesting that there has been no connection between the lower Jinsha River and the Red River since the Eocene. Key Points The sedimentary provenance of modern Jinsha River sands and fluvial and lacustrine sediments from the Plio‐Pleistocene Xigeda Formation have been investigated using Pb isotopic analyses of detrital K‐feldspar The Jinsha River achieved its present drainage character no later than the late Pliocene The lower Jinsha River has not been connected with the Red River since the Eocene