[S-EM16] Geomagnetism, paleomagnetism, and rock magnetism

[SEM16-P03] Sedimentary magnetism of Holocene tidal sediments in Korea with significance of greigite formation: report from a case study

*Hyeon-Seon Ahn^1,2, Sujeong Park¹, Hyun Ho Yoon¹, Jaesoo Lim^1,2, Yuhji Yamamoto³ (1.Korea Institute of Geoscience and Mineral Resources (KIGAM), 2.University of Science and Technology (UST), 3.Marine Core Research Institute (MaCRI), Kochi University)

Keywords:sedimentary magnetism, greigite, tidal sediment, estuary, Holocene, South Korea

We recently recognize that in-situ formation and preservation of greigite may contribute greatly to sedimentary magnetism in many parts of Quaternary sediments with diverse sedimentary settings in Korea. The understanding of greigite-related issues could be critical in obtaining faithful records of not only ancient geomagnetic variations but also paleo-environmental changes in and around a particular region. For the final goal of better understanding of sedimentary magnetism in association with greigite, we started rock magnetic and paleomagnetic investigations, combined with additional information (e.g., geochemical data), on Holocene estuarine sediments in the southwestern coast of South Korea. Here, we report results and interpretation of mineral magnetic characterization from a sediment core. We find a number of high peaks in the ratio of saturation isothermal remanent magnetization to magnetic susceptibility (SIRM/χ), eventually interpreted as greater abundance of authigenic greigite probably of single-domain-like sizes. The high SIRM/χ peaks occur in multidecadal to centennial scales, and are correlated well with strong freshwater input proxy values that could be associated mainly with strong rainfall intensity. It further allows the inference that the greigite formation could be just after or, at most, within tens of years after the sediment deposition.