Nguyen Thi Phuong Thao, Tran Nghi, Dinh Xuan Thanh

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The characteristics of late Miocene lithofacies in the southeast region of Hanoi depression have been revealed on the basis of sedimentary evolution in relation to sea level change and tectonic movement. During late Miocene, global sea level change had created one depositional sequence and three sedimentary systems tract. The lowstand systems tract (LST) is characterized by 5 rhythms of alluvial lithofacies. These rhythms were represented by rough and humoc seismic wave fields. This environment was not favorable condition for coal formation. The transgressive systems tract (TST) was characterized by 6 transitional lithofacies rhythms. Each lithofacies rhythm consisted of 4 facies: the tidal flats sand facies of the bay, the mud facies of the river mouth lagoon, the coastal marshy mud facies creating coal and the bay greenish-gray clay facies. The pacing process involved changes in the local sea level caused by tectonic lift. Each tectonic subsidence phase took place at a very slow velocity, so it was compensated for fine-grained sediment creating marshy mud facies to develop mangroves on a large scale. It was a prerequisite to create thick coal seams distributed near the end of each rhythm. A part of highstand systems tract (HST) were eroded due to the improved folding process, creating an angular unconformity boundary with Pliocene-Quaternary sediments. However, after reconstracting of deformated section, it was clear that this system tract had only one rhythm including 2 facies: prodelta mud facies and alluvial fan sandstone facies.

Keywords: Lithofacies-paleogeography, sedimentary systems tract, sedimentary rhythm

Keywords: Lithofacies-paleogeography, sedimentary systems tract, sedimentary rhythm.


[1] Specialized Council of Earth Sciences (editor), Red River Rift Zone, Geodynamic Characteristics, Mineralization and Natural Disaster, Science and Technology Publishing House, Hanoi, 2004 (in Vietnamese).
[2] T. Nghi, Sedimetary geology of Vietnam, Vietnam National Publishing House, Hanoi, 2018 (in Vietnamese).
[3] P.Q. Trung, N.D. Dy, D. Bat, N.Q. An, D.V. Khoi, New polynologic discoveries in Paleogene-Neogene sediments in Northern Song Hong basin, Procedding of Conference on Vietnam Petroleum Institute 20 year development and prospects, Hanoi, 1998, page 171-185 (in Vietnamese).
[4] N.X. Huyen, Zoning of Paleogene-Neogene sedimentary facies in Red River basin, PhD thesis (Russian), 1990.
[5] L.T. Nghinh, N.X. Huyen, N.T. Yem, T.T. Sau,