THE SPATIAL DISTRIBUTION OF SEDIMENTATION RATES IN THE DONGSHA SHOAL OF RADIAL SAND RIDGES TO THE NORTH OF JIANGSU COAST

Radial sand ridges are well developed off the Jiangsu Coast. The landforms and their changes of the ridges have been the hot spots of coastal oceanic scientific researches. The Dongsha Shoal remains in a key part of the radial sand ridges system. 18 cores were drilled in the Shoal in 2012 and using ²¹⁰Pb technique, the sedimentation rates for part of these positions are measured. The spatial distribution pattern of sedimentation rates are obvious that the rates in the western edge and central part are low and those in the eastern, northern and southern edges are high. The landform characters and hydrodynamic conditions will certainly affect the spatial distribution pattern of sedimentation rates in the Dongsha Shoal.
The hydrodynamic conditions and depositional landforms are feedbacks to each other. On the one hand, the hydrodynamic conditions are the original fact to make depositional landforms. On the other hand, depositional landforms are the factors to change the hydrodynamic conditions. It is same to the spatial distribution pattern of sedimentation rates and the landform characters in principle.
The Dongsha Shoal is controlled by two different tidal wave systems. Due to the convergence and divergence of the tidal wave systems, the sedimentation rates are increasing from southwest to northeast. In the centre of the radial sand ridges or in the south of the Dongsha Shoal, the hydrodynamic force is weak, in comparison with that in the edge of the Dongsha Shoal. As the results, the sedimentation rates are high there. When the Xiyang tidal channel widens, the western part of the Dongsha Shoal is eroded. In the eastern part which is controlled by the wave and tide from the Pacific,the shoreline has also been eroded. The southeast has unique characteristics,affected by the tidal wave system in Chenjiawu tidal channel. With the widening of the Xiyang tidal channel, the Dongsha Shoal has an obvious tendency moving southeast.