Global Changes and Sedimentation on Continental Shelf
Qin Yunshan (institute of Oceanology. Chinese Academy of Sciences, Qingdao)
Based on the systematic analysis and study made recently of several sedimentarv cores and high resolution geophysical records from the Yellow Sea Shelf, the writer believes that the global-change view must be taken to carry out comprehensive analysis and comparisons in the study of sedimentary characteristics of China Shelf. In the later stage of Late Pleistocene, the palaeoenvironment of China Shelf was different from both North America in which Laurentide Ice Sheet developed and Europe with Scandinavia Ice Sheet oc-cured. Instead of ice sheet, large range of desert and loess distribution area (including most area of China's shelf) occurred in the Asian Continent. At the end of the last glacial period, the ice sheets in North America and Europe Continent began to melt, providing the North American shelf and Europe shelf with sufficient water sources. Local crust oscillations further enhanced the washing power of rivers. When the continental ice sheets melted over, the rivers passing or entering the continental shelf lost their runoff. After the transgression of the Hoiocene, many traces of buried palaeochannels have naturally been left over on the continental shelf areas. As the sedimentary environment of China Continental Shelf was characterized by dry and cold, the shelf was not only bared and without the protection of ice sheet but also eroded by storms in the most prevailing of the ice age. Therefore, eolation was the basic effect, on the China Shelf area in the later stage of Late Pleistocene. As known up to now, major sedimentary types of the shelf desertization are (1) long scale eolation surface. (2) mixing accumulation of large area, (3) sedimentary structure of reposeangle type and (4) typical sediments of buried sand-dunes.