Sand wave deposition in the Taiwan Shoal of China

Abstract

The Taiwan Shoal is the convex terrain in the southern Taiwan Strait, the largest strait in China. In 2006 and 2007, 21 samples and more than 200-km sub-bottom data as well as 80-km near shore side-scan sonar data were gotten, which gave an initial image of the boundaries of the Taiwan Shoal and revealed the internal structure of the sand waves in this area. The results showed that the major component of the sediment samples was sand, and sand waves occurred everywhere in this area, which closely followed the range of the Taiwan Shoal as we know. The western boundary of the Taiwan Shoal thus reaches the 30 m isobaths near the shore, and as a result, its area potentially covers approximately 12 800–14 770 km2. The sand waves have different shapes under the complex ocean dynamics, and the height of sand waves in the near shore is usually smaller than that in the Taiwan Shoal. The number of sand waves ranged from1–5 per kilometer, with more waves in the isobath-intensive area, suggesting the importance of topography for the formation of sand waves. The stratigraphic structure under the seabed has parallel bedding or cross bedding, and large dipping groove bedding can be seen locally in different parts, which may be the result of terrestrial deposition since the Late Pleistocene.