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The Japan Sea is the largest marginal sea in the northwestern Pacific Ocean. For a long time, it has been widely believed that the sediments are deposited in strongly reducing environment, which results in extremely weak magnetic signals and then restricts the application of frequently-used magnetic method in this region. To investigate deeply the availability of magnetic indicators in paleoenvironmental and paleoceanographic studiesin the Japan Sea, we conducted systematic rock magnetic analyses, high-resolution accelerator mass spectrometer (AMS) 14C dating, and grain-size analysis on a 626-cm-long sediment core (LV87-2-3, water depth 740 m) recovered from the northern Japan Sea that has been studied in relatively low level. The results indicate that the studied core corresponds to a sedimentary record since approximately 48.3 ka BP. The majority of primary ferrimagnetic minerals, mainly magnetite, in the sediments below 55 cm, had been reduced into pyrite, which caused weakly magnetic intensity. This is associated closely with the intensified stratification of water body and the increase in surface productivity during interstadials in the Dansgaard-Oeschger (D-O) cycles. Nevertheless, there are still four strong magneticlayers characterized by elevated percentages of high-coercivity minerals (i.e., hematite and goethite), which are termed as ‘hard-magnetic abnormal’ layers and correspond well with the Heinrich Events. This indicatesrelatively weak reducing conditions that were resulted from the enhanced East Asian Winter Monsoon (EAWM) and injection of high salinity Tsushima Warm Current (TWC). These changes, however, are not reflected by the grain-size of sediment. Our study therefore not only indicates that the role of magnetic parameters in the paleoenvironmental and palaeoceanographic reconstructions of the Japan Sea during the last glacial, but also provides new perspectives and ideasfor relevant investigations in the future.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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