Late Pleistocene-Holocene sedimentary evolution in the coastal zone of the Red River Delta

Hoang Phan Hải Yen,Tran Thị Thanh Nhan,Tran Nghi,Ngo Quang Toan,Hoang Anh Khien,Doan Dinh Lam,Hoang Van Long,Dinh Xuân Thanh,Nguyen The Hung,Nguyen Thị Huyen Trang,Tran Ngọc Dien,Nguyen Thị Tuyen,Tran Xuan Truong,Tran Thị Dung,Nguyen Thi Phuong Thao,Vu Quang Lan

doi:10.1016/j.heliyon.2020.e05872

Abstract

The Red River Delta is considered one of the largest megadelta systems in Asia. The formation of this delta has been controlled by the continent-ocean interaction and sea-level fluctuation during the Cenozoic. In this study, we present a new sequence stratigraphic framework of the Red River Delta based on borehole lithofacies analysis and high resolution seismic data. The Late Pleistocene–Holocene sediments in the coastal zone of the Red River Delta were subdivided into three systems tracts: (1) the lowstand systems tract (LST) is characterized by a Late Pleistocene alluvial silty sand facies complex (arLSTQ13b); (2) the transgressive systems tract (TST) is illustrated by the coastal marsh facies complex and the lagoonal greenish-gray clay facies of Early-Middle Holocene (amt, mtTSTQ21−2); and (3) the highstand systems tract (HST) is composed of the Middle-Late Holocene deltaic clayish silt facies complex (amhHSTQ22−3). The boundaries between these three systems tracts are not isochronous, namely: (1) The LST-HST boundary has been associated with the Würm 2 Glaciation, which occurred at ~40-18 Ka.; (2) The TST-LST boundary is identified by a transgressive erosion surface, whose age ranges from ~12-5 Ka.; and (3) the HST-TST boundary is an unconformity between the submarine deltaic facies complex and the Middle Holocene marine flooding plain.

Highlights

The Red River Delta extending over ~15,000 km2 is one of the largest delta systems around the world and the second largest delta in Vietnam after the Mekong River Delta in the South (Figure 1)
The Quaternary sediments of the Red River Delta have evolved for ~1.9 million years of development, which have been controlled by 5 cycles of global sea level change, corresponding to 5 cycles of glacial/interglacial events (Gunz/G-M; Mindel/R–W1; Wurm1/W1–W2; Wurm2/W2- Flandrian Transgression) (Nghi et al, 1991; Nghi and Toan, 1991; Tan et al, 2014)
Our core description showed that this complex is composed of two facies: (1) The lower facies is a fluvial channel, polymineral sand facies with poor sortness and roundness (So 1⁄4 2.5; Ro 1⁄4 0.4) (Figures 4 and 6) and (2) the floodplain silty clay of the upper facies is characterized by poor sortness (Figure 6)

Summary

Introduction

The Red River Delta extending over ~15,000 km is one of the largest delta systems around the world and the second largest delta in Vietnam after the Mekong River Delta in the South (Figure 1). The uppermost section of the delta consists of ~200m-thick unconsolidated overlying Tertiary weakly consolidated sedimentary rocks, which have been deposited during Red River pull-apart basin development in Cenozoic (Since ~34 Ma to present) (Nghi et al, 1991; Vietnam oil and gas Group, 2007). The coastal zone of the Red River Delta is composed of: (1) the onshore land and (2) the nearshore area, extending from the Thai Binh River mouth in the North to the Day River mouth in the South (Figure 1). Shoreline position) while the submerged part is extended to a depth of ~30m of water depth, where is marked by the latest ancient shoreline associated with Flandrian transgression (~13000 Ka.)

Methods

Results

Discussion

Conclusion