THE CHARACTERISTICS AND DISTRIBUTION OF HOLOCENE SAND BODIES IN CHANCIIANG RIVER DELTA AREA

The Holocene sand bodies in Changjiang River delta area may be classified genetically as river mouth sand, marine sand and river channel-fill sand, which are different in external geometry, internal characteristics, spatial distribution and contact with overlying and underlying beds. Their areal distribution forms a complicated complex that may be considered as a typical sand distribution model of tide-dominated deltas. In Holocene, Changjiang River delta area were subjected to transgression caused by the postglacial rise of sea level, and regression resulting from delta progradation. As a consequence of the alternative transgression and regression sand bodies have the characteristics of two-storeyed beds in vertical sequence. The transgressive sands are overlain by regressive ones, and there is a wedge of marine clay between them.