Last glacial emplacement of methane-derived authigenic carbonates in the Sea of Japan constrained by diatom assemblage,carbon-14, and carbonate content |
| |
| Institution: | 1. Laboratoire de Géologie de l''Ecole normale supérieure de Paris, PSL Research University, CNRS UMR 8538, 24 rue Lhomond, 75005 Paris, France;2. Centre for Energy Geoscience, School of Earth and Environment, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia;3. Sorbonne Universités, UPMC Université Paris 6, CNRS, Institut des Sciences de la Terre Paris, 4 place Jussieu, 75005 Paris, France;4. EPOC Université de Bordeaux, UMR 5805, avenue des facultés, 33405 Talence, France |
| |
| Abstract: | We studied diatom assemblages and CaCO3 contents of methane-derived authigenic carbonates from the eastern margin of the Sea of Japan and assessed the formation time of these samples. Radioactive 14C date was determined in selected samples to obtain the maximum age of the time. The results of our study suggest mass formation of carbonate nodules in a glacial period within ～40 ky, consistent with a published U/Th dating result of carbonate nodules in the study area. Diatom assemblages and contents in the carbonate nodules (abundance of ～106/g, dominance of neritic-littoral species, warm/cold water species ratio lower than ～25) differ from the near-seafloor sediments in the study area, which have characteristics of Holocene sediments in the Sea of Japan, and suggest cementation of glacial sediments. Laminated sediments in some nodule samples are glacial sediments because laminations are records of a low sea level period in the semi-enclosed ocean. Similarity of diatom assemblages and contents in all carbonate samples is another evidence of glacial sediments in nodules. Glacial sediments with oceanic cold water species as low as Holocene sediments restricts the sediment age to before 20 cal. ky BP. Carbonate contents higher than 78 wt% suggest the cementation of poorly compacted sediments near the seafloor, and the date of carbonate cementation is, therefore, close to that of the cemented sediments. Most carbonate nodule samples in this study were formed in a glacial period and detection of 14C restricts this period to within ～40 ky. |
| |
| Keywords: | Methane-derived authigenic carbonate Stable carbon isotopic composition Uranium/Thorium dating Radio carbon fourteen Calcium carbonate content Last glacial maximum Diatom assemblage Sea of Japan |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
