Search

Continental-scale drainage reorganization is generally understood to result from landform evolution forced by the coupling between tectonic activity and climate change, attracting worldwide attention. Planation surfaces and river terraces constitute the most direct geomorphological archives for integrating the history of river systems and for reconstructing processes of drainage reorganization based on provenance analysis of the fluvial sediments. The Middle Yellow River has incised into the Ordos Block, which was previously levelled by a planation surface, creating the Jinshaan Gorge and linking the Hetao Basin to the north and the Fenwei Basin to the south. Multiple lines of evidence, from terraces correlation, sedimentary characteristics, and fluvial provenance, suggest that the Middle Yellow River catchment was occupied by fluvio-lacustrine systems before drainage integration, accumulating a sedimentary sequence derived from surrounding Red Clay and bedrocks during the period between 8.3 and 3.7 Ma. The planation surface was uplifted subsequently, forcing reorganization of the fluvio-lacustrine systems. Their integration resulted in the formation of the Jinshaan Gorge prior to 1.2 Ma. Numerous terraces were created during incision by the Middle Yellow River from north to south along the gorge. Our data, obtained from zircon U Pb dating and lithological composition of fluvial gravels, further points to a remarkable discrepancy in provenance between the fluvio-lacustrine systems overlying the planation surface and the terraces sequence formed by the integrated Middle Yellow River, confirming the drainage reorganization process constrained by the geomorphic records. • Fluvio-lacustrine systems occupied the Middle Yellow River before integration. • Yellow River terraces are different from fluvio-lacustrine systems in provenance. • The Middle Yellow River has been excavated and integrated during Plio–Pleistocene. [ABSTRACT FROM AUTHOR]

Strategic studies of gravel deposits, in particular using heavy-mineral analyses, have thrown light on the important unresolved question as to the timing of the initiation of the Yellow River drainage through the Sanmen Gorge, which linked the headwaters of that system in the Fenwei Basin and further upstream with the North China Plain and the Pacific Ocean in the east. Survey of the Sanmen Gorge reach revealed previously unrecognized gravel levels: a higher fifth terrace (T5) and a gravel that formed on a high-level planation surface that is preserved on the flanks of the gorge, below the Xiaoshan upland. This high-level gravel differs markedly from the Yellow River terraces, with a lack of material from the upstream catchment, and would appear to represent a small fluvial catchment that developed in the area during the formation of the planation surface, before the Sanmen Gorge was excavated. Comparison was also made with basin-fill gravels from the endorheic fluvio-lacustrine system that existed immediately upstream of the gorge, and was captured by the Yellow River when the latter was cut, and with the modern bedload gravel of the Yellow River in this reach. The former contains significant quantities of unstable hornblende, which implies more local derivation for the endorheic system, whereas the modern bedload resembles the terrace gravels in showing compositional maturity and long-distance transport from upstream within the catchment. The work reinforces a minimum age of 1.2 Ma for the formation of the Sanmen Gorge. • The gravel layer accumulated on the planation surface along the eastern front of the Xiaoshan represents a local river. • The local river sediments are different from the typical Yellow River gravels and the upper Sanmen Formation. • The Sanmen paleolake within the Fenwei basin was finally disrupted by the westward capture of this local river. • The Sanmen Gorge was excavated by the local river through the Xiaoshan separating the Fenwei basin and North China Plain. • The Yellow River integration may be attributed to the remarkable climatic fluctuation starting in the Mid-Pleistocene. [ABSTRACT FROM AUTHOR]

Fluvial response to allogenic and autogenic controls concerns the understanding of landform evolution related to the interaction between tectonic movements, climate, surface process and human activity. Paleo-channels, as part of geomorphic archives, have been widely employed to study this issue during recent decades. Previous work has however concentrated on the mechanisms driving river migration. A new approach, in which multiple elements are considered, is employed here in the examination of paleo-channel formation in the Jiudong Basin, located at the northeastern margin of the Tibetan Plateau and characterized by active tectonic deformation, a dry climate and ancient human activity. Based on geomorphic and sedimentary analysis, eight paleo-channels formed by the Taolai and Hongshuiba rivers (two tributaries of the Beida River catchment) have been identified. AMS14C dating of the overlying lacustrine sediments defined their respective abandonment at ca. 22.2, 20.9, 15.3, 18.8, 13.9, 11.9, 3.5 and 1.1 cal. Ka BP. The migration histories of the two rivers have been reconstructed, and then well correlated with reference to archives of tectonic, climatic and human influence. Our results suggest that these controlling factors seem to be coupled and have a competitive relationship in driving river migration. In the northeastern margin of the Tibetan Plateau, channel migration can therefore be regarded as a result of fluvial response to the interaction between rapid tectonic activity, climatic fluctuation and human influence. • 8 paleo-channels have been identified in the northeastern margin of the Tibetan Plateau. • These paleo-channels have been constrained by AMS14C dating in the last glacial period. • These paleo-channels are coupled record of climate, tectonics and human influence. [ABSTRACT FROM AUTHOR]

The Jinsha River has attracted considerable attention for nearly a century due to the morphology of its drainage basin. To explain the evolution of the Jinsha drainage basin, most researchers have considered that the present-day Jinsha (the upper reach of the Yangtze) was once a tributary of a single, southward-flowing river system called the Paleo-Red River, which drained into the South China Sea and was captured by the Upper Yangtze River, after which the flow direction changed to eastwards. The sudden disappearance, at 5.5 Ma, of the Red River submarine fan, which was fed primarily by the Paleo-Red River system, provides an important chronological constraint on the drainage reorganization and the capture event. However, until now, no geomorphic evidence has been presented to support this hypothesized age. Considering this problem, nine well-preserved terraces (T9 to T1) at Jinjiangjie in the Middle Jinsha River were evaluated in this study. To establish the chronological framework of these terraces, a combined dating approach was employed, incorporating electron spin resonance dating, cosmogenic nuclide (26Al/10Be) burial dating, and optically stimulated luminescence dating. We obtained a complete chronological sequence for terraces T9–T1, with ages of approximately 1.07 (T9), 0.70 (T8), 0.65 (T7), 0.51 (T6), 0.47(T5), 0.44(T4), 0.30 (T3), 0.18 (T2), and 0.047 (T1) Ma, respectively. Constrained by this framework, we calculated an average long-term fluvial incision rate of ~147 mm/ka. The reconstruction of the paleo-topography and paleo-drainage, based on digital elevation model data for the re-filling of the deeply incised river valley, indicates that the present drainage pattern in the Middle Jinsha system was established after the disruption of the paleo-landscape surface at an elevation of ~2000 m above sea level. The age of the present-day Middle Jinsha drainage was determined at approximately 5.5 Ma by extrapolating the average valley incision rate, suggesting that the present-day Jinsha was formed at about this time. Our results agree with the previously estimated timing of the disappearance of the Red River submarine fan. • A flight of 9 fluvial terraces dated using ESR, 26Al/10Be and OSL dating in Jinsha River (the upper reach of Yangtze) • About 147 mm/ka of average incision rate in Middle Jinsha River since early Pleistocene • First age of Jinsha River achieving its present-day drainage pattern extrapolated from the average valley incision rate [ABSTRACT FROM AUTHOR]