High-resolution reconstruction of the paleoenvironmental changes since the Last Glacial by the analyses of highland moor deposits

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Five all-cored sediments were taken at the Ohnuma Moor in the northern part of Hyogo Prefecture, three of which were the oriented samples obtained by newly developed non-magnetic core samplers. Synthetic analyses of the core sediments were performed including petrologic analysis of tephra layers, AMS-^<14>C dating, pollen and diatom analyses, and physical measurements of lightness, grain size, loss on ignition, magnetic susceptibility, and paleomagnetic secular variation (PSV), to clarify the paleoenvironmental changes since the Last Glacial and the formative processes of the moor. More than 65-m thick deposits underlie the Ohnuma Moor. The upper part about 50-m thick is composed mainly of sand and gravels, while the finer sediments about 17-m thick, mainly of clay and peat, comprise the upper part containing six tephra layers of K-Ah, SUk, MsP, Sh, AT, and Nh. Based on the estimated eruption ages of K-Ah and AT and more than 30 AMS-^<14>C dates along with the results of diatom analysis, it is inferred that the Ohnuma Moor originated the depression formed by the large scale landslide at ca.41 ka cal.BP and has been developed as a mire between ca.32 and 29 ka cal.BP and after ca.13 ka cal.BP and as a wetland until ca.32 ka cal.BP and from ca.29 to 13 ka cal.BP. All measured physical properties show the cyclic changes with small amplitude for the time interval from 41 to 13 ka cal.BP without the air fall tephra horizons. The temporal changes are possible to reflect the global climatic changes named the Dansgaadrd-Oeschger Oscillations with Heinrich Events. The PSV can be reconstructed mainly for the period between 35 and 32 ka cal.BP, suggesting the effectiveness of the new sampling method. However, it is necessary to improve it because the core samples were disturbed especially at their uppermost and lowermost parts.