CHARACTERISTICS AND ORIGIN OF THE TIDAL SAND RIDGES OFF THE MINJIANG RIVER ESTUARY, SOUTHEASTERN CHINA

Tidal currents dominate great part of China's continental shelves. And the tidal depositional morphology, such as sand ridges, sand sheets and sand waves (sand dunes) are widely distributed. However, tidal sand ridges have not been discovered off the Minjiang River Estuary before. This time we found a group of linear sand bodies in different sizes distributed off the Estuary in SW-NE direction. Some of them may join together becoming shallow banks, but there are erosional channels between most of the sand ridges. The southeast flank of the sand ridge is steeper than the northwest, indicating that sand ridges are migrating southeastward. According to the analysis of the topography and geomorphology, sediments and tidal current field of the area, it is concluded that the materials come from the ancient Minjiang River delta, that was formed in the inshore estuaries bay during the Holocene transgression. The current tidal system is the main factor to form the tidal ridge group.