关键词: 古云梦泽演化;粒度分析;钻孔沉积物;“河流-湖泊-三角洲”复合沉积模式;江汉平原;晚全新世

Abstract: The paleo-Yunmeng Lakes served as the primary carriers of water and sediment exchange between the Jianghan Plain and the Changjiang River during the Late Holocene.Their formation and evolution were recorded in the sediments, which contained abundant information about the paleoenvironment and paleoclimate.To explore the patterns and mechanisms of sedimentary evolution of the paleo-Yunmeng Lakes, we analyzed physical and chemical indexes, including grain size, total organic carbon, and magnetic susceptibility of borehole sediments collected from the Jianghan Plain from2014to2019.By combining these analyses with Accelerator Mass Spectrometry radiocarbon dating(AMS14C) for accurate dating and grain size frequency curves, the overall sedimentary environment features of the Jianghan Plain during the Late Holocene were obtained.These features enabled an exploration of the patterns and modes of sedimentary evolution within the paleo-Yunmeng Lakes.The results indicated that, according to the boreholes sedimentary facies records, a "river-lake-delta" complex depositional model emerged during the formation and evolution of the paleo-Yunmeng Lakes.A horizontal comparison of the boreholes revealed that deltaic facies deposits first formed in the western part of the Jianghan Plain and gradually expanded eastward, suggesting that this complex depositional model not only influenced the sedimentary sequence of individual boreholes but also spatially regulated the evolution of the entire paleo-Yunmeng Lakes.The research results have revealed the characteristics and laws of natural evolution of river and lake systems in the Jianghan Plain under global changes in historical periods, which has important reference significance for guiding the ecological restoration of the Jianghan Lake Group, and predicting the future trend of river-lake relationship evolution in the middle and lower reaches of the Changjiang River.

Key words: evolution of the paleo-Yunmeng Lakes ; grain size analysis ; borehole sediments ; complex depositional model of "river-lake-delta" ; Jianghan Plain ; Late Holocene