A REVIEW ON LATE QUATERNARY SEDIMENTARY GEOLOGY OF THE YANGTZE RIVER DELTA

Late Quaternary strata of the Yangtze River delta are divided into three sedimentary areas,namely the incised-valley area, and northern and southern parts of interfluve areas. In these areas, stratigraphic frameworks are quite different,reflecting different processes of the post-glacial transgression. From the viewpoint of sequence stratigraphy, all the late Quaternary strata of the Yangtze River delta belong to a six-order sequence, which stretches across the shelf of the East China Sea. In the Yangtze River delta, different superimposing patterns of lowstand systems tract, transgressive systems tract and highstand systems tract were recognized between land and subaqueous parts of the delta. Sediments formed during the Younger Dryas event and by storm surges and periodic tides in the Yangtze River delta were also been identified by preliminary study on millennial and centennial geological events. Based on the sedimentary geological investigation, the sedimentation pattern of the Yangtze River delta was summarized, implying the late Quaternary development of the Yangtze River delta was controlled by continuous subsidence and sediment supply.
There are still several crucial questions unsolved in the sedimentary geology of the late Quaternary Yangtze River delta. First of all, existence of the Yangtze River delta during last glacial proximal was still a controversy. Secondly, the transition pattern and model of the paleo-Yangtze estuary to the Yangtze delta were not elucidated clearly. Thirdly, the concepts of "source to sink" have not been applied to systematic sedimentary geological research on the Yangtze River delta. At last,the influence of human activity on the Yangtze River delta has just been noticed in recent decades. Further researches on these above key issues are fundamentally based on the sedimentary geological study on the subaqueous part of the Yangtze River delta. Furthermore, the subaqueous part of delta has been less studied compared to the land part of the delta at present. Therefore, emphasis should be placed on the subaqueous part in the future sedimentary geological study on the Yangtze River delta.