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

通过高地沼泽沉积物分析高分辨率重建末次冰期以来的古环境变化

基本信息

批准号：
14380034
负责人：
KATO Shigehiro
金额：
$ 5.31万
依托单位：
Museum of Nature and Human Activities, Hyogo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2005
项目状态：
已结题

项目摘要

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.

在兵库县北部的大沼沼地采集了5个全芯沉积物，其中3个为新开发的非磁芯取样器定向样品。通过对岩心沉积物的岩石学分析、AMS- <14>C测年、花粉和硅藻分析，以及亮度、粒度、燃失率、磁化率和古地磁长期变化（PSV）等物理测量，对末次冰期以来的古环境变化和摩尔的形成过程进行了综合分析。超过65米厚的沉积物在大沼沼泽下面。上部约50 m厚，主要由砂和砾石组成；上部约17 m厚，主要由粘土和泥炭组成，含有6层K-Ah、SUk、MsP、Sh、AT和Nh。根据估计的K-Ah和AT火山喷发年龄和30多个AMS-^<14>C年代以及硅藻分析结果，推断大沼沼地起源于ca.41 ka cal.BP大规模滑坡形成的洼地，在ca.32 ~ 29 ka cal.BP之间和ca.13 ka cal.BP之后发育为泥沼，在ca.32 ka cal.BP之前和ca.29 ~ 13 ka cal.BP之间发育为湿地。在41 ~ 13 ka cal.BP的时间间隔内，所有测量到的物性都表现出小幅度的周期性变化。时间变化可以反映全球气候变化，称为dansgaard - oeschger振荡与海因里希事件。在35 ~ 32 ka cal.BP范围内可以重构出PSV，表明了新采样方法的有效性。但是，由于岩心样品的上、下两部分受到较大的扰动，有必要对其进行改进。