tailieunhanh - Biến động các địa hệ trong Holocen ở khu vực đới bờ châu thổ sông Hồng

Địa hệ là một hệ thống điều kiện tự nhiên được tích hợp giữa tướng trầm tích và các hệ sinh thái theo thời gian và không gian trong mối quan hệ với sự thay đổi mực nước biển, biến đổi khí hậu và chuyển động kiến tạo. | VNU Journal of Science: Earth and Environmental Sciences, Vol. 35, No. 1 (2019) 94-111 Original article Variation of Geosystems in Holocene Red River Coastal Zone Tran Nghi1, Tran Thị Thanh Nhan1, Dinh Xuan Thanh1, Tran Ngoc Dien1, Nguyen Thi Huyen Trang1 Tran Thi Dung1, Pham Van Hai2, Nguyen Thi Phuong Thao1 1 VNU University of Science, 334 Nguyen Trai, Hanoi, Vietnam 2 Paleontology - Stratigraphy association of Vietnam Received 04 March 2019 Revised 11 March 2019; Accepted 13 March 2019 Abstract: The geosystem is a natural conditional system that is integrated by the lithofacies and ecosystems in space and in time in relation to sea level change, climate change and tectonic movement. Another way, the geosystem is a natural unit including the causal relation between ecosystem and lithofacies, in which the lithofacies is cause and ecosystem - result. There are 3 phases of sea level changes in Holocene as follows: (1) Flandrian transgression lasted from 10ka BP to 5ka BP.; (2) Middle - late Holocene regressive phase existed from 5kaBP to 1ka BP.; (3) Modern sea level rise have occured from 1 ka BP to present. The depositional process taking play in the coastal zone of the Red River delta according to lithofacies association law in space and in time created 3 geosystem groups and 8 geosystems. Each lithofacies type will correspond with one geosystem and one or more ecosystems. In early - middle Holocene transgressive lithofaciesecosystem group there are typical Geosystems: (1) The Geosystem of coastal swamp clay facies mangrove forest ecosystem; (2) The geosystem of lagoonal greenish grey clay facies- bioaquatic and bottom molussca ecosystems. On the contrary, in middle - late Holocene regressive phase there are two lithofacies - ecosystem groups: (1) The geosystem of middle - late buried submarine deltaiccoastal marine ecosystem ; (2) Modern deltaic geosystem group composed of 4 geosystem: (1) The geosystem of high deltaic plan sand ridge facies - rice field and