Program

The Quaternary’s climate is characterized by tens of glacial-interglacial cycles. These periodic climate oscillations exert a huge impact on a series of geomorphic processes, such as river evolution, delta development, sea level change. Though the responses of these processes have been individually interpreted, how they coupled under glacial-interglacial cycles remains largely unclear. The Yangtze River in China, which flows from the Tibetan Plateau to the East China Sea, provides an excellent opportunity to illustrate these coupled processes. The Jianghan Plain is located in the middle reaches of the Yangtze River, more than 700 km from the sea. High-resolution optically stimulated luminescence (OSL) ages for cores from the Jianghan Plain revealed that the sedimentation rate during the last deglaciation (~20-~10 ka; ~2 m/ka) was far higher than that (0.3 m/ka) in the last glaciation and the Holocene. Thus, a pattern of geomorphic evolution along the middle reaches and deltaic area of the Yangtze River since the last glaciation is hypothesized: during the last glaciation, low sea level in the East China Sea led to high longitudinal gradient and strong erosive ability of the Yangtze River, resulting a deep-cutting landscape from the delta to the Jianghan Basin. Upon the surge of sea level after the last glaciation maximum (LGM), incised valleys in those deep-cutting areas were filled within a short period (~10 ka). When the sea level reached a maximum in the early Holocene, sedimentation rate from the delta to the Jianghan Basin returned to low value again. The Jianghan Plain, which was more than 1200 km away from the coastal area during LGM when the sea level was more than 120 m lower than present, had nearly simultaneous responses to sea level change, which is significantly more widespread and quicker than previously thought. Similar processes may have occurred in other big rivers in the earth.