宜昌地区第四纪沉积物重矿物特征及其与三峡贯通的关系

水系的变化导致物源区的变化,反映在相关沉积盆地中表现为沉积物中矿物组合的改变,以及特征矿物的出现.通过对三峡出口处宜昌地区第四纪沉积物中重矿物特征的研究,结合区域地质资料、野外沉积特征研究和样品EsR测年资料,认为0.73 Ma以前的冲积扇一扇三角洲沉积中重矿物特征明显不同于之后的阶地沉积及现代河床沉积物.这种重矿物组合的不同反映了0.7 Ma前后物源区的改变,同时也指示长江三峡贯通的时间.

Character of heavy minerals in Quaternary sediments in Yichang area and its relationship with cut-through of the Yangtze Three Gorges, China

The change of drainage can lead to the change of provenance. This shows in the change of minerals assemblage and the appearance of particular minerals in the related sedimentary basin. On the basis of the research for the heavy minerals in Quaternary sediments in Yichang area which lies at the end of the Three Gorges and the research data of regional geology, sedimentary character of sections and ESR dating data, one can find that heavy minerals character in alluvial fan and fan-delta before 0.73 Ma is different from that in the sediments in terrace and present river sands. This difference reflects the provenance change before and after cut through of the Three Gorges and also indicates the cutting through time of the Three Gorges.