海南岛东部外陆架水下埋藏古三角洲

THE SUBMARINE BURIED PALEO-DELTA IN THE EAST OUTER CONTINENTAL SHELF OF HAINAN ISLAND

海南岛东部外陆架水深 １００～１５０ ｍ处，存在一个大面积的水下埋藏古三角洲。从 浅地层记录中发现，这片水下古三角洲保存有完好的三角洲沉积结构，特别是前积层的倾 斜层理十分清晰。该水下古三角洲的存在是古海岸线的一个证据。

There is a large-scale submarine buried paleo-delta in the east outer continental shelf of Hainan Island, in water depth from 100 to 150 m. The paleo-delta is about 5 000 km^2 in size, sloping downward from northwest to southeast. The comprehensive analysis of the geographical location, topography, sediment and, especially, sub-bottom structure etc., of the paleo-delta shows that the submarine buried paleo-delta has intact foreset beds and bottom set beds as well as destroyed topset beds owing to erosion or slump effects. The ekistence of large-scale oblique bedding of foreset beds in water depth of 135-150 m, which is very clear on sub-bottom profile record, is a very good evidence of the low sea level during the Late Pleistocene. The relict sand exposed directly on seabed above the sub marine buried paleo-delta, which results from erosion of the seabed, is littoral deposit formed during the last stage of Late Pleistocene to early Holocene. The sediment sequence of the sub marine buried Paleo-delta is a transgressive one. It is formed during the transgression Period of the last stage of Late Pleistocene to early Holocene. The geographical location of the paleo-delta discussed in this paper is corresponding to that of the paleo-delta outside the Zhujians River Estuary, which was formed in the same period.