As a typical active marginal sea, the northern South China Sea receives substantial terrigenous detrital inputs from adjacent landmasses. Among these, the southwestern offshore area of Taiwan represents a critical node for sediment transport, owing to the island’s exceptionally high erosion rates and frequent extreme precipitation events. Consequently, reconstructing the long-term evolution of sedimentary organic matter (OM) in this region offers valuable insights into paleoclimate variability, land–sea material exchange, and marine carbon sequestration mechanisms.
In this study, we investigated sediment core K11 (22°04′20″N, 119°10′14″E; water depth 1875 m), retrieved from the southwest Taiwan sea margin. A robust age model was established using AMS ¹⁴C dating of planktonic foraminifera, covering the past ~2800 years with a temporal resolution of 6–7 years. High-resolution measurements of total organic carbon (TOC), total nitrogen (TN), stable carbon isotope (δ¹³C_org), and radiocarbon isotope (Δ¹⁴C) were performed, and a three-end-member mixing model was applied to quantitatively apportion the contributions of marine autochthonous OM, terrestrial C₃ plant OM, and petrogenic OM derived from Taiwan.
Our results indicate that sedimentary OC is predominantly composed of petrogenic OC from Taiwan (53.9%–59.9%), followed by marine autochthonous OC (17.9%–32.3%) and terrestrial plant OC (13.5%–22.4%). Notably, the input flux of terrigenous OC, particularly the petrogenic component—exhibited pronounced variability over time, closely tracking regional precipitation changes; specifically, wetter intervals corresponded to enhanced transport of terrestrial OM to the study site. Furthermore, the OM compositional record shows clear responses to canonical Holocene climatic episodes: elevated terrigenous input during the 2.8 ka cold event and the Dark Ages Cold Period, reduced terrigenous supply during the Roman Warm Period and the Medieval Warm Period, and an increased contribution from marine productivity during the Little Ice Age.
Collectively, this study provides a high-resolution, OM-based paleoclimate archive for the western Pacific marginal seas and offers scientific context for understanding the long-term behavior of land–sea carbon cycling under natural climatic forcing.