Late Pleistocene-Holocene sequence stratigraphy of the subaqueous Red River delta and adjacent shelf

Abstract

The model of Late Pleistocene-Holocene sequence stratigraphy of the subaqueous Red River delta and the adja­cent shelf is proposed by interpretation of high resolution seismic documentsand comparison with previous research results on Holocene sedimentary evolution on the delta plain. Four units (Ul, U2, U3, and U4) and four sequence stratigraphic surfaces (SBI, TS, TRS and MFS) were determined. The formation of these units and surfaces is related to the global sea-level change in Late Pleistocene-Holocene. SB1, defined as the sequence boundary, was generated by subaerial processes during the Late Pleistocene regression and could be remolded partially or significantly by transgressive ravinement processes subsequently. The basal unit U1 (fluvial formations) within incised valleys is ar­ranged into the lowstand systems tract (LST) formed in the early slow sea-level rise ~19-14.5 cal.kyrBP, the U2 unit is arranged into the early transgressive systems tract (E-TST) deposited mainly within incised-valleys under the tide­influenced river to estuarine conditions in the rapid sea-level rise ~14.5- 9 cal.kyr BP, the U3 unit is arranged into the late transgressive systems tract (L-TST) deposited widely on the continental shelf in the fully marine condition during the late sea-level rise ~ 9-7 cal.kyr BP, and the U4 unit represents for the highstand systems tract (HST) with clino­form structure surrounding the modern delta coast, extending to the wate depth of 25-30 m, developed by sediments from the Red River system in ~ 3-0 cal.kyrBP.