Reconstruction of Paleoenvironmental Changes using Radionuclides:Uranium and Thorium Isotopes in the Lake Sediments

利用放射性核素重建古环境变化：湖泊沉积物中的铀和钍同位素

基本信息

批准号：
18510008
负责人：
YAMAMOTO Masayoshi
金额：
$ 2.63万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

Investigation on polar ice-sheet and lake sediments of mide-latitude area have made studies on past climatic and environmental conditions in continental areas very important to obtain a more information cu mechanisms of Quaternary environmental changes. In Lake Baikal in southeastern Siberia, the dear signal of changing paleoclimate in the sediments has been found in depth distributions of the diatom frustule numbers, water content and organic carbon content in sediments. Furthermore, microelements, especially, uranium have been also noticed as one of the most important chemical index. Thus, the U (and Th) isotopes in lacustrine sediments serve as good proxies for not only chronology but also indicator of climatic changes. Jake Hovsgol, the largest fresh water lake in Mongolia, promiePa the sensitive response to environmental changes in surrounding catchments. In this study, an attempt was made to get a detail feature of U and Th isotopes distribution in the sediment core of Lake Hovsgol. The obtained data were discussed laying stress on dating using 238U-234U-230Th-232Th system, and compared with those obtained previously in sediments core fit Lake Baikal The final purpose of this study was to elucidate the changes in the depth distribution of U and Th isotopes and their ratios in the sediments ad to obtain insight into their implication for paleoclimatic variation.1. Depth profiles of U and Th isotopes in a 81 m length sediment core (HDP-04) of Lake Hovsgol were measured in details, and U-series isochron techniques were successfully applied to the dating for some layers.2. The depth distribution of authigenic U well correlated with that of bio-marker of primary products, suggesting that the fluctuation of authigenic U well correlates with glacial-interglacial cycle at least about IMa.3. A similar pattern of u depth profiles in sediments was observed in the dated depth from 24 m to surface in Lake Hovsgol and lake Baikal with quite different water qualities.

对米德纬度地区的极性冰盖和湖泊沉积物的调查已经对大陆地区的过去气候和环境条件进行了研究，以获取更多信息，以获取更多信息，以获得第四纪环境变化的CU机制。在西伯利亚东南部的贝加尔湖中，在沉积物的深度分布中发现了变化的沉积物中古气候变化的信号。此外，尤其是微元素，铀也被认为是最重要的化学指数之一。因此，湖间沉积物中的U（和Th）同位素不仅可以作为年代学的良好代理，而且还表明了气候变化的指标。杰克·霍夫斯戈尔（Jake Hovsgol）是蒙古最大的淡水湖，Promiepa对周围集水区环境变化的敏感反应。在这项研究中，试图获得了霍夫斯戈尔湖沉积物核心中U和Th同位素分布的细节特征。讨论了使用238U-234U-230th-232th系统对约会的压力进行讨论，并与先前在沉积物核心核心拟合湖中获得的数据进行了比较。这项研究的最终目的是阐明U和Th同位素的幅度分布的变化以及在沉积物中的比例及其在沉积物中的比例，以启用其对古代杂物的影响。详细测量了Hovsgol湖的81 m长度沉积物核（HDP-04）中的U和Th同位素的深度曲线，并在某些层中成功地应用于U-Series同位技术，并成功地应用于约会。2。身材u的深度分布与主要产品的生物标志物的深度分布相关，这表明身份元素U孔的波动与冰川间 - 冰期循环的波动至少至少关于IMA.3。在霍夫斯戈尔湖（Lake Hovsgol）和贝加尔湖（Lake Baaikal）的日期深度中观察到了相似的沉积物中的U深度剖面模式。