A preliminary study on sediment flux in the Changjiang Delta during the postglacial period

Abstract

The sequence boundary and maximum flooding surface of the postglacial transgressive cycle in the Changjiang Delta have been identified by 265 cores. Based on these data, the sediment amounts and the thickness-isopach maps of postglacial sedimentary cycle, transgressive and regressive successions in the Changjiang Delta have been worked out. The results show that the sediment amounts of the postglacial cycle, transgressive succession and regressive succession are 17742.2×10 8 tons, 9791.9×10 8 tons and 7950.3×10 8 tons, respectively. The postglacial sediments deposited in the incised valley are more than those in the two flanks, and the sediments contained in the transgressive succession are more than those in the regressive succession. The postglacial sediments deposited in the southern flank are more than those in the northern flank, and the sediments in the area seaward from the postglacial transgression maximum (PTM) of each flank are more than those in the area landward from the PTM. Considering both the possible changes of the ratio between the sediment amount remained in the modern Changjiang Delta and the sediment discharge of the Changjiang River in the postglacial period, and the changes of the sediment discharge, the authors believe that in the postglacial period, the sediment discharge of the Changjiang River is (2.36—4.86)×10 8 tons/a on average, totaling to (35400—70800)×10 8 tons, and the sediments delivered to sea and adjacent coasts are (1.18—3.54)×10 8 tons/a on average, totaling to (17700—53100)×10 8 tons.