Identification of sediment provenance in the South Yellow Sea using detrital amphibole geochemistry

Abstract

Marginal seas are major sinks of fluvial sediments. Identifying the sources and quantifying the contributions of different sources are essential to studying the transport and distribution of terrestrial sediments on the shelves of marginal seas. The South Yellow Sea (SYS) to the east of the Asian continent receives sediment discharged by the Huanghe (Yellow) and Changjiang (Yangtze) rivers, and it is a favorable location for studying the provenance of marginal sea deposits. In this study, we tested the geochemistry of amphibole in different grain-size fractions (very fine sand and coarse silt) of the SYS sediments, and compared this geochemistry with those of fractions in the Huanghe River (HH) and the Changjiang River (CJ) to quantify the terrestrial provenance of the sea. The results show that for the very fine sand fraction, Zr, Be, Ga, Ge, Nb, Cd, and Hf in amphibole can be used as indicators to discriminate between the HH and CJ sediments. For the coarse silt fraction, the trace elements of Ba, Zr, Li, Rb, and Hf in amphibole can be used to distinguish the sediment of the two rivers. The mean contribution of the HH sediment to the very fine sand and coarse silt fractions of SYS is 45.0% ± 6.7% and 57.6% ± 5.9%, respectively, compared with 54.8% ± 6.7% and 42.4% ± 5.9% for the CJ, respectively. Provenance analysis of amphibole reveals spatial variation in the supply of terrigenous sediment to different parts of the SYS: the nearshore area of the Shandong Peninsula and the sea areas adjacent to the abandoned Huanghe River (FHH) estuary are supplied mainly by the HH, whereas the South and eastern parts of the SYS are supplied predominantly by the CJ. In the SYS sediment of very fine sand, a line extending from 34°N, 121°E to 35°N, 123°E demarcates the boundary between areas supplied by the HH (north) and the CJ (south), while coarse silt has a longer transport distance and higher mixing degree compared with very fine sand. This study demonstrates that quantitative analysis of the trace-element geochemistry of detrital amphibole can discriminate terrigenous sediment provenance in the mixed area of the marginal sea.