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Abstract:

The Red River Delta (RRD) is located in the western coastal zone of the Gulf of Tonkin (Vietnam). The Holocene sedimentary of RRD are influenced by rives, wave and tidal processes and more recently to grain-size distribution. In this study, sediment core (~ 36 m) was collected in the wave-dominated region of RRD. The parameter of sediment used to reconstruct the sedimentation environments of RRD, sediment facies can be classified into silt, sandy silt, and silty sand. Besides, the mean grain-size Md) values show that the sediment in core samples included from fine silt to very fine sand with a dominance of very coarse silt and coarse silt. According to the lithological characteristics, sediment grain-size distribution the sediment core sample can be divided into six deposition environments which consisted of sub-tidal flats and inter-tidal flats (from 36 to 30.1 m); shelf-prodelta (from 30.1 to 18.9 m); delta front slope (from 18.9-11.7 m); delta front platform (from 11.7 to 4.1 m), tidal flat (from 4.1 to 0.5 m) and flood plain (from 0.5 m to surface of sediment). The textural characteristics of the core sample were closely correlated with the core sample from previous study in RRD. In a sediment core from 30.1 to 18.9 m, sediment showed erosion surface during the transgression at 8860 cal. year BP. The textural parameter of the RRD has resulted of the interaction between sea level rise and fluvial inputs. In addition, the dominance of very coarse silt and coarse silt can be indicated the prevalence of comparatively from low to high energy condition in the RRD.