Geochemical characteristics and palaeoenvironmental reconstruction of the sediments from the Gulf of Tonkin, South China Sea

Abstract

AbstractGeochemical investigations of sediments from core GC22 from the Tonkin Gulf, South China Sea, have been carried out in order to reconstruct the palaeoenvironmental evolution of the area during the Holocene. Vertical variations in Al/Ti, K/Al and Mg/Al clearly indicate the degree of chemical weathering in the source area. Zr/Ti and SiO2/Al2O3 recorded the history of current velocity changes, and La/Co v. La/Sc, combined with distribution patterns of rare earth elements, suggested that Hainan Island was the main source of the sediments during the Holocene. Based on the results of the analysis, the evolution of palaeoenvironments in the Tonkin Gulf can be divided into four stages: (1) 10.12–6.46 ka BP, the regional climate got warmer, and the sea level of the gulf rose rapidly, which is indicated by rapid declines in Sr/Ba and CaO. (2) 6.46–4.3 ka BP, the gulf had a stable depositional environment, and the local climate became cold and dry. (3) 4.3–3.55 ka BP, the currents and sedimenary provenance in the gulf were significantly influenced by the opening of the Qiongzhou Strait. (4) 3.55 ka BP–present, the regional sea level remained roughly stable.