Structure of Paleosecular Variation : Relation to the Core Dynamics

古世变的结构：与核心动力的关系

基本信息

批准号：
13640424
负责人：
TANAKA Hidefumi
金额：
$ 2.37万
依托单位：
Kochi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

Experimental studies with a newly introduced thermal demagnetizer were made on many volcanic rocks from the Unzen Volcano and the Ontake Volcano, Japan. Angular standard deviation(ASD) of the paleosecular variation(PSV) in the Brunhes Chron obtained from Unzen was in the same level as those from other areas of Japan, but it was larger for Older Unzen than Younger Unzen. Paleomagnetic methods were also applied to some volcanostratigrphic problems ; estimation of emplacement temperature of pyroclastic flows and lava identifications. One of the most important results obtained from the paleomagnetic studies of the Ontake Volcano is the establishment of the geomagnetic excursions in the latest Pleistocene in Japan. Reliability of the excursions is very high because they were found from two andesite lava flows, in which stabilities of the remanences are much higher than those from sediments. Paleointensities obtained from one of the two lava flows are abut 1/10 of the present-day value, and the associated virtual geomagnetic poles(VGPs) locate near the central Pacific Ocean. As the VGP positions in the central Pacific were also reported from the Auckland excursion in New Zealand, it was proposed that the equatorial dipole moment becomes dominant during the excursion. To explain the structure of PSV, a new statistical model was developed, in which Gaussian fluctuation was given to an eccentric dipole. This simple model explains most of the structures of PSV ; latitude dependent ASD and the shape of the histograms of the paleointensities.

用新引入的热电器进行了实验研究，是对日本未开除的火山和Ontake火山的许多火山岩进行的。从UNZEN获得的Brunhes Chron中古分子变异（PSV）的角标准偏差（ASD）与来自日本其他地区的角度相同，但对于年龄较大的Unzen比年轻的Unzen更大。古磁方法也适用于某些火山层流问题。估计火山碎屑流和熔岩识别的估计温度。从Ontake火山的古磁研究获得的最重要的结果之一是在日本最新的更新世上建立了地磁游览。游览的可靠性非常高，因为它们是从两个安山岩熔岩流中发现的，其中，不记录的稳定性比沉积物中的稳定性高得多。从两个熔岩流之一获得的古敏度是当今值的1/10，相关的虚拟地磁杆（VGP）位于中部太平洋附近。由于在新西兰的奥克兰游览中也报道了中太平洋中部的VGP位置，因此提出赤道偶极矩在旅行期间占主导地位。为了解释PSV的结构，开发了一种新的统计模型，其中对偏心偶极子进行了高斯波动。这个简单的模型解释了PSV的大多数结构。依赖于纬度的ASD和紫色直方图的形状。