Heavy Minerals Characteristics of Sediments in Jianghan Plain and Its Indication to the Forming of the Three Gorges

Quaternary sediments in Jianghan Plain,the first large-scale offloading basin of the Yangtze River after the forming of Three Gorges,reflect the characteristics of provenance through which the Yangtze River flows.The heavy mineral samples were collected from the sand layer in the drilling core,with the size fraction ranging from 0.125 mm to 0.063 mm.We find that there is an obvious mutation of the combination and quantitative characteristics of heavy minerals at the depth of 110 m,with the paleomagnetic age of 1.1 Ma,through series of analyses including the change of content,index ATi,index GZi and index ZTR.The combination of characteristic heavy minerals from the sediments above the depth of 110 m is in accordance with the modern Yangtze River.So we conclude that the Three Gorges was formed at around 1.1 Ma when the materials from the upper reaches of the Three Gorges has deposited at Jianghan basin as a result of the transfixion of the Yangtze River.