The Bailong River, situated at the eastern margin of the Tibetan Plateau, is currently expanding toward the Upper Yellow River through drainage-divide migration and river captures. Quantifying the divide migration rate and the river capture timing is essential for understanding the drainage-basin evolution and the underlying driving forces. In this study, we use cosmogenic nuclide 10Be data to derive average erosion rates of 0.18–0.37 mm/yr for four catchments in the Bailong River headwater region. By combining χ-plot analyses with these erosion rates, we calculated the migration rates of drainage divides and constrained the timing of a river capture between the Bailong River and the Upper Yellow River. Our results indicate that the Bailong River is expanding toward the Upper Yellow River at rates of ~0.03–0.96 mm/yr. The river capture, identified at the location of the highest divide migration rate, occurred ~116 ka (n = 1) or ~ 77 ka (n = 2) ago. Considering both tectonic and climatic contexts, we suggest that this drainage evolution is primarily governed by steady-state elevation difference between adjacent watersheds resulting from differential tectonic uplift. Meanwhile, sinistral strike-slip motion along the Kunlun Fault produces higher migration rates to the south of the fault than to the north. The inferred capture age broadly coincides with the Last Interglacial (MIS 5, ~130–71 ka), implying that warm and humid climatic conditions likely accelerated the expansion of the Bailong River. Moreover, we propose that expansion of the Bailong River over geological timescales has promoted incision and disasters within the river basin.
Landslide-dammed lakes are widespread distributed along the southeastern Tibetan Plateau, shaping the regional landform and expressing tectonic activity. The Taoyuan reach in the middle Jinsha River preserves one of the most extensive and best-exposed sequences of landslide-dammed lake deposits in the region, providing a rare opportunity to investigate the coupling between tectonic activity and fluvial geomorphic evolution. Detailed field investigations and stratigraphic analysis reveal at least three phases of paleolakes deposits in the Taoyuan reach. Chronological constraints from optically stimulated luminescence and 26Al/10Be cosmogenic nuclide burial dating indicate that the two most recent paleolake phases developed during 92–65.7 kyr and 56.8–36.4 kyr, respectively. Both depositional sequences terminate downstream near Zhaizicun, suggesting that landslides repeatedly block the river at the same location. The landslide body is situated directly above the Chenghai Fault, and multiple seismically induced landslides and fracture features have been discovered along this fault zone. The spatial coincidence between landslide-damming sites and the fault displacement zone, with most of them concentrated in the Late Pleistocene epoch, supports a tectonically controlled mechanism. This suggests that strong paleoseismic events associated with the Chenghai Fault triggered recurrent large-scale landslides and river blockage. These findings highlight the critical role of fault-river intersection zones in governing the earthquake-landslide-dammed lake hazard chain and provide new constraints on Late Quaternary tectonic activity and long-term landscape evolution along the Jinsha River.
