A multiproxy comparison study on the source apportionment of organic matter in core sediments in the East China Sea

Abstract

The contributions from various sources and temporal variations of sedimentary organic matter (OM) in marginal seas are not fully understood due to highly dynamic hydrodynamic conditions and discrepancies among different source indicators. This study conducted a multiproxy analysis based on biomarkers and bulk δ¹³C values to apportion and estimate OM sources in core sediments from the Min-Zhe muddy area of the East China Sea. The goal is to precisely determine the sources and contributions of sedimentary OM, thereby providing new insights into constraining their temporal variations in this highly dynamic region. Multiple biomarkers consistently demonstrate a significant contribution from terrestrial organic matter (TOM). Pearson’s correlation analysis further indicates that long-chain n-alkanols are reasonable biomarkers for tracing TOM, while long-chain n-alkanes reflect the input of other sources. The terrestrial to marine biomarker ratios (TMBR and TMBR_ol) and a binary mixing model with different δ¹³C end-members indicate that TOM is the dominant component. Variations in these contributions can reach up to 18 % and 29 % due to δ¹³C end-member differences and biomarker variations, respectively. Factors affecting these variations include biomarker stability, multiple sources of long-chain n-alkanes, and δ¹³C end-member differences. Despite inherent variability in precise numerical data, the broadly consistent temporal trends of TOM contributions, as inferred from δ¹³C mixing models and TMBR_ol, indicate that these proxies can be effectively used to reconstruct their temporal records. However, more efforts are still needed to accurately determine the contributions of different sedimentary OM sources, particularly to constrain the reasonable δ¹³C end-member values.