SUMMARY

The Holocene evolution of the Hậu Giang coastal area

Vũ Trường Sơn, Nguyễn Biểu, Nguyễn Địch Dỹ,
Doãn Đình Lâm, Trịnh Nguyên Tính, Trần Trọng Trịnh

According to data from shallow seismicity - high resolution of river bed, sea floor and drilling cores, the Quaternary sediments have been divided into stratigraphic sequences and parasequences, the Holocene stratigraphic scheme of the Hậu Giang coastal zone has been established, and, at last, the evolution of Holocene has been examined.

Holocene sediments in the study area are composed of 3 sequences, named as Đại Ngãi Formation, where there are rather good seismic data and drilling core samples. The Holocene evolution in the Hậu Giang coastal zone passed through 3 cycles of rise-lowering of sea level, changing the providing source with materials, and activities of the Hậu River. In the first cycle (12-7 thousands years), the depositional process happened on the mainland, in valleys, formed at the end of Pleistocene with fluvial, lacustrine and swampy deposits; the second cycle (7-4 thousands years) was characterized by the highest sea standing level, plunging the Mekong delta into water, during this there were 3 times of gentle rise-lowering of sea level, and when the water went down 7 parasequences were formed; the third cycle (4000 years to present) happened with the development of 9 parasequences in the regime of regression. From 2000 years to present, the sea level has been rising and lowering 9 times in the regime of regression with the recent level rise forming the high sand dune in the sea direction of Trà Vinh. With that tendency, the present sea level rise lies in the rule of the nature together with a part of human impact, leading to higher rate of sea level rise.

Ngày nhận bài: 4/9/2009

Người biên tập: TS. Hoàng Anh Khiển

(Cục Địa chất và Khoáng sản Việt Nam).