SEQUENCE STRATIGRAPHY OF THE QUATERNARY SEDIMENTS IN THE RED RIVER DELTA AND ITS STRATIGRAPHIC SIGNIFICANCE

Tran Nghi¹, Dinh Xuan Thanh¹, Tran Thi Thanh Nhan¹⁾, Nguyen Thi Huyen Trang¹, Nguyen Thi Tuyen²,

Ngo Quang Toan³, Hoang Anh Khien³, Nguyen Thi Phuong Thao¹, Tran Thi Dung¹_, Tran Ngoc Dien⁴

¹ VNU University of Science, Vietnam

² University of Poitiers, France

³ Vietnam Union of Geological Sciences, Vietnam

⁴Marine Geology and Minerals Division.

Corresponding author: tranhnghi@gmail.com

Abstract: The Red River Delta is one of the largest mega delta within the SE Asia. Quaternary sediments of this delta have been derived from various important resources. However, there are still many scientific and practical issues of the Quaternary sediments that have not been satisfactorily resolved. Especially, the division of this formation is supposed to have no reliable scientific basis, that greatly affects geological mapping and investigation of mineral resources. This article will present new research results on establishment of sedimentary cycle and sequence stratigraphy of the Quaternary sediments within the Red River Delta. Our results show that the Quaternary formation in the study area has been associated with 5 cycles of sea level change. The concept and approaching methods applied in this study are based on lithofacies association according to the sedimentary systems tracts, which are characterized by their typical relationship between petrographic characteristics, quantitative physical sedimentary properties and global sea level change.

The results have allowed us to identify 5 sediment cycles corresponding to 5 sequence cycles: (1) the first sequence (Sq1): Early Pleistocene (Q₁¹); (2) the second sequence (Sq2): early Pleistocene (Q₁^2a); (3) 3rd sequence (Sq3): Late Pleistocene (Q₁^2b); (4) 4^th sequence (Sq4): early late Pleistocene (Q₁^3a) and (5) 5^th sequence (Q₁^3b-Q₂). Each sequence is composed of 3 systems tract (LST, TST, HST). Each systems tract is characterized by a distinctive lithofacies assemblage and is related to global Sea level change. These 5 sequences can be used for comparison and linking stratigraphy from the Red River Delta to adjacent areas.

Keywords: Lithofacies, sequence stratigraphy, sedimentary cycle, systems tract, regression, transgression, glacial, interglacial.

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