Holocene environmental changes in Red River delta, Vietnam as inferred from the stable carbon isotopes and C/N ratios

• Published in: Journal of Earth System Science Vol. 128; no. 1; pp. 1 - 12
• Main Authors: Tue, Nguyen Tai, Quan, Dang Minh, Nguyen, Pham Thao, Dung, Luu Viet, Quy, Tran Dang, Nhuan, Mai Trong
• Format: Journal Article
• Language: English
• Published: New Delhi Springer India 01.02.2019; Springer Nature B.V
• Subjects: Carbon; Carbon 13; Carbon isotopes; Carbon-nitrogen ratio; Climate change; Coasts; Coring; Earth and Environmental Science; Earth Sciences; Environmental changes; Floodplains; Floods; Grain size; Grain size distribution; Holocene; Isotopes; Lithology; Mangroves; Organic carbon; Phytoplankton; Ratios; Rivers; Sea level; Sea level changes; Sediment; Sedimentary environments; Sedimentation & deposition; Sediments; Shelving; Size distribution; Slopes; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Tidal flats; Total organic carbon; Red River; Vietnam; stable isotopes; Environmental change; Vietnam; Red River delta; C/N ratios
• ISSN: 0253-4126; 0973-774X
• DOI: 10.1007/s12040-018-1041-1

The present study applied stable carbon isotopes, C/N ratios, and sedimentological indicators to reconstruct environmental changes during Holocene and to test the hypothesis that δ 13 C and C/N ratios are accurate proxies of sea level change in the Red River delta (RRD), Vietnam. A 36 m long sediment core was mechanically drilled in the wave-dominated region of the RRD. The covariation of lithological characteristics, sediment grain-size distribution and geochemical proxies (LOI, TOC, C/N, δ 13 C ) suggested that the sediment core could be divided into six depositional environments, consisting of sub- and inter-tidal flats (formed before 8860 cal. year BP), shelf-prodelta, delta front slope (formed from 8860 to 2290 cal. year BP), delta front platform, tidal flat, and flood plain (from 2290 to 0 cal. year BP). Covariation of δ 13 C and C/N ratios in the sediment core allowed for tracing the origin of sedimentary organic carbon, which shifted from the dominance of mangroves and C3 plants at the sub- and inter-tidal flats to marine phytoplankton at the shelf-prodelta and delta front slope. The sedimentary sources of the delta front platform, tidal flat and flood plain were a mixture of phytoplankton and C3 plants, with the later source being dominant.