Unraveling Environmental Forces Shaping Surface Sediment Geochemical “Isodrapes” in the East Asian Marginal Seas

Sarah Paradis*, Markus Diesing, Hannah Gies, Negar Haghipour, Lena Narman, Clayton Magill, Thomas Wagner, Valier V. Galy, Pengfei Hou, Meixun Zhao, Jung-Hyun Kim, Kyung-Hoon Shin, Baozhi Lin, Zhifei Liu, Martin G. Wiesner, Karl Stattegger, Jianfang Chen, Jingjing Zhang, Timothy I. Eglinton

*Corresponding author for this work

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Abstract

As major sites of carbon burial and remineralization, continental margins are key components of the global carbon cycle. However, heterogeneous sources of organic matter (OM) and depositional environments lead to complex spatial patterns in sedimentary organic carbon (OC) content and composition. To better constrain the processes that control OM cycling, we focus on the East Asian marginal seas as a model system, where we compiled extensive data on the OC content, bulk isotopic composition (δ13C and Δ14C), total nitrogen, and mineral surface area of surficial sediments from previous studies and new measurements. We developed a spatial machine learning modeling framework to predict the spatial distribution of these parameters and identify regions where sediments with similar geochemical signatures drape the seafloor (i.e., “isodrapes”). We demonstrate that both provenance (44%–77%) and hydrodynamic processes (22%–53%) govern the fate of OM in this margin. Hydrodynamic processes can either promote the degradation of OM in mobile mud-belts or preserve it in stable mud-deposits. The distinct isotopic composition of OC sources from marine productivity and individual rivers regulates the age and reactivity of OM deposited on the sea-floor. The East Asian marginal seas can be separated into three main isodrapes: hydrodynamically energetic shelves with coarser-grained sediment depleted in OC, OM-enriched mud deposits, and a deep basin with fine-grained sediments and aged OC affected by long oxygen exposure times and petrogenic input from rivers. This study confirms that both hydrodynamic processes and provenance should be accounted for to understand the fate of OC in continental margins.

Original languageEnglish
Article numbere2023GB007839
JournalGlobal Biogeochemical Cycles
Volume38
Issue number4
Early online date4 Apr 2024
DOIs
Publication statusPublished - Apr 2024

Keywords

  • machine learning
  • organic matter
  • organo-mineral interactions
  • radiocarbon
  • stable isotopes
  • surface sediment

ASJC Scopus subject areas

  • Global and Planetary Change
  • Environmental Chemistry
  • General Environmental Science
  • Atmospheric Science

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