|Tidal sand ridges on the East China Sea shelf|
Chang-Su, Y.; Jia-Song, S. (1988). Tidal sand ridges on the East China Sea shelf, in: de Boer, P.L. et al. (Ed.) Tide-influenced sedimentary environments and facies. Extended versions of papers presented at the Symposium on Classic Tidal Deposits, held August 1985 in Utrecht, Netherlands. pp. 23-38
In: de Boer, P.L. et al. (Ed.) (1988). Tide-influenced sedimentary environments and facies. Extended versions of papers presented at the Symposium on Classic Tidal Deposits, held August 1985 in Utrecht, Netherlands. D. Reidel Publishing: Dordrecht. ISBN 90-277-2622-1. ix, 530 pp., more
|Authors|| || Top |
- Chang-Su, Y.
- Jia-Song, S.
Widespread investigations have revealed sand ridges on the shelf of the East China Sea. They occur mainly in the submerged palaeovalley of the Changjiang River and the adjacent area. These huge sand ridges are 10 - 60 km long, 2 - 5 km wide and 5 - 20 m high with a spacing of 8 - 14 km. They extend ESE - WNW(about 120° - 300°). They have asymmetrical profiles in transverse sections, with steeper slopes facing SSW. They mainly consist of well-sorted fine sands (grain size of 2.5 - 3.0~ with abundant debris of intertidal to shallow water marine shells. The shallow seismic profiles show an unconformity between the sand ridges and the underlying strata, and the very low-angle inclined layers within the sand ridges. The sand ridges on the shelf of the East China Sea occur mainly in four groups. The depths to the top of these groups are 96 - 115 m, 75 - 90m, 58 - 70 m and 45 - 55 m. This corresponds to the palaeocoastlines of -100 m, -80 m, -60 m and -50 m respectively, reflecting the history of the post-glacial transgression in the East China Sea. The shallow marine fossils and the moribund morphology suggest that the tidal sand ridges on the East China Sea shelf probably developed during the post-glacial transgression when water depths were shallower and tidal currents were stronger than those of the present-day. As the sea level rose and the tidal currents became weaker, the sand ridges gradually ceased growing and became 'relict' sand bodies on the shelf of the East China Sea. When covered by fine-grained sediments of late Holocene age in the nearshore area, they were preserved in the stratigraphical section and became an important type of sand body formed in estuary to shallow shelf tidal environments. Evidence of such buried sand bodies can be found in some shallow seismic profiles from the Bureau of Marine Geological Survey.