Sedimentary provenance perspectives on the evolution of the major rivers draining the eastern Tibetan Plateau

Abstract

The origin and development of the major rivers in the eastern Tibetan Plateau have been a special focus of research because of the close links recognized between river formation, tectonic uplift, and climate change. In this article, we review a number of sedimentary provenance investigations aiming to constrain the drainage evolution of the main rivers draining eastern Tibet, including the Mekong, Red, Pearl, Yangtze, and Yellow rivers. The Mekong River was formed no later than ~17 Ma, likely triggered by a period of enhanced East Asian summer monsoon precipitation during the middle Miocene. A single large paleo-Red River draining the southeastern Tibetan Plateau into the Song Hong - Yinggehai Basin had been proposed to explain the unusual drainage pattern. However, this is not compatible with the distinctive provenance signals in the southeastern Tibetan river sands compared with the Song Hong - Yinggehai Basin, indicating that there has been no large-scale paleo-Red River since the late Eocene. The Pearl River has formed during the late Oligocene, as there was a sharp provenance change in the Pearl River Mouth Basin. Moreover, rivers draining southeast coastal China (e.g., Min River) migrated westward at the same time. These clues highlight that paleo-rivers in southeastern China started to migrate inland during the Late Oligocene. In contrast, the formation timing of the Yangtze River is still under intensively debated, ranging from late Cretaceous to Holocene, mainly due to the complex evolution history of this trans-continental river. The formation of the First Bend of the Yangtze River likely happened during the late Eocene, resulting from changes in the regional topographic gradient triggered by local magmatic activity and/or movement of the Ailao Shan-Red River Fault. Onshore and offshore provenance evidence indicate that incision of the Three Gorges happened no later than the late Miocene. Formation of the Square Bend of the Yellow River occurred prior to the late Pliocene, while incision of the Sanmen Gorge, a key capture point connecting the upper-middle and lower Yellow River likely occurred in the early Pleistocene (~1.2 Ma). Multi-provenance proxies on well-dated and continuous sedimentary records can provide objective information in terms of the origin and evolution of the major rivers flowing from eastern Tibet. Although the evolution of these rivers remains debatable, a comparison among the river evolution, climatic and tectonic events suggests that Eocene local and isolated drainage patterns is likely related to the dry climate condition in the East Asia. Oligocene and late Miocene inlandward expansion and integration of rivers coincides with both the formation of the East Asian Monsoon and the timing of major tectonic events, such as the growth of the Tibetan Plateau and the rifting and opening of the eastern Asian marginal basins, highlighting the importance of climate and tectonics in controlling the evolution of major rivers.