AUTHOR=You Chen-Feng , Liao Wei-Lan , Huang Kuo-Fang , Chung Chuan-Hisung , Liu Zhifei 

TITLE=Sediment source variation using REEs, Sr, and Nd isotopic compositions: a case study in MD05-2901, northwestern South China Sea

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 10 - 2023

YEAR=2024

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1292802

DOI=10.3389/fmars.2023.1292802

ISSN=2296-7745

ABSTRACT=The South China Sea (SCS) is the largest marginal sea in the western Pacific, fed by large Asian rivers, characterized by substantial volumes of sediment derived from surrounding Asian continents and islands. This study utilizes the Rare Earth Elements (REEs), Sr isotopes ( 87 Sr/ 86 Sr) and Nd isotopes (ℇNd) in detritus fractions of MD05-2901 sediments in northwestern SCS, to evaluate relative contribution among the Mekong River, the Red River, the Pearl River and rivers in SW Taiwan over the last 32 kyr. This deep sea core is located off the coast of central Vietnam, an upwelling region with only minor continental inputs, and this study is important for a better understand of the main sources of terrigenous material and their temporal variations in the region. In addition, potential particle exchange is examined using the same proxies in the Fe-Mn oxy-hydroxide fractions. The obtained records are systematically compared with the available climatic archives in the region. The REEs in the Fe-Mn oxy-hydroxides support the argument of water mass signature separation in bulk sediments by chemical leaching procedures. These 87 Sr/ 86 Sr in the Fe-Mn oxy-hydroxides phase fall in a range between 0.709262 and 0.709313, deviated significantly from the modern seawater. The ℇNd vary >3ε, more radiogenic in the Fe-Mn oxy-hydroxides, where the lowest value occurred in the Bølling/Allerød (B/A) and higher values during the Younger Dryas (YD). The latter implies increased contribution of loess dusts or Taiwanese rivers under dry/cold climatic conditions, compared with situation in modern time. The Red River and the Mekong River together may have contributed >60% during the Last Glacial Maximum (LGM) and YD. In contrast, the Pearl River components have increased sharply to ~60% during the warm B/A. These results demonstrate that the MD05-2901 sediments record sensitively of changes in weathering intensity on land and transport pathways in the coastal regions in the Holocene.