227 / 2024-02-28 12:11:39

The mechanism of ENSO-related palaeoflood drives the evolution of the ancient Yunmeng Lakesevidence from boreholes records in the eastern Jianghan Plain

Late Holocene,Ancient Yunmeng Lakes,Grain size,ENSO-related palaeoflood,Relationship between rivers and lakes

As the main carrier of water and sediment exchange between the Jianghan Plain and the Yangtze River during the Late Holocene, the ancient Yunmeng Lakes has received widespread attention and discussion. At present, there is still controversy over the evolution process and influencing factors of the ancient Yunmeng Lakes, especially the driving mechanism of the monsoon precipitation-induced floods on the evolution of the ancient Yunmeng Lakes, which has become a near-term research hotspot in the river-lake relationship. In the historical period, the evolution characteristics of the ancient Yunmeng Lakes were recorded by the sediments, which contained rich palaeoenvironment and palaeoclimate information. Here, using boreholes in the eastern part of the Jianghan Plain as a case study, we investigated the evolution model of the ancient Yunmeng Lakes by integrating physical and chemical indexes based on grain size with precise AMS¹⁴C dating. The results of boreholes sedimentation showed frequent alternations between fluvial and lacustrine facies, indicating that the evolution of the ancient Yunmeng Lakes was influenced by multiple sedimentary dynamics, resulting in the emergence of a "river-lake-delta" composite sedimentation model that regulated the evolution of the ancient Yunmeng Lakes. Exploration of the natural drivers indicated that ENSO-related palaeoflood was the main driving factor that promoted the emergence of the composite sedimentation model, leading to the expansion of the delta during the evolution of the ancient Yunmeng Lakes. Under this mechanism, ENSO-related palaeoflood would facilitate the development of the ancient Yunmeng Lakes in the short term, but would cause the lake to silt up and shrink over a long time scale, eventually resulting in its demise. These findings have important practical significance for the protection of the Jianghan Lake Group and provide theoretical basis for the study of the natural evolution mechanism of the relationship between rivers and lakes in the context of global change.