Paleoclimatic and orbital modulation of the geomagnetic field

地磁场的古气候和轨道调制

基本信息

批准号：
16204034
负责人：
YAMAZAKI Toshitsugu
金额：
$ 28.54万
依托单位：
National Institute of Advanced Industrial Science and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

1. We investigated the strength of magnetostatic interaction among magnetic particles in marine sediments. On relative paleointensity estimation, IRM is preferable to ARM for normalizing difference in NRM acquisition efficiency of sediments because ARM acquisition is strongly affected by the magnetostatic interaction.2. We constructed a paleointensity stack during the last 250 kyr in the Northwest Pacific. To obtain reliable relative paleointensity records, it is necessary to exclude horizons that suffer from dissolution of magnetic minerals owing to early diagenesis. The S-ratio, which represents a proportion of low coercivity magnetic minerals, is sensitive to magnetite dissolution, and thus can be used for detecting such horizons.3. We obtained a relative paleointensity record during the last 1.6 m.y. from a sediment core in the North Pacific. The paleointensity and magnetic properties of this core were compared with those from the western equatorial Pacific. Relative paleointensiti … More es of the two areas coincide well, whereas magnetic properties differ greatly. A time-series analysis using a wavelet transform showed that paleointensity records contain variations with a time scale of 100 kyr. Variations of magnetic properties are not synchronous with those of paleointensity, and there is no significant correlation between the two even if they have a common time scale of 100 kyr. We thus conclude that the 100-kyr variations in paleointensity records are of geomagnetic origin, and not caused by magnetic property variations of sediments induced by paleoclimate changes.4. Paleointensity and inclination variations during the last 800 kyr were recovered from cores in the eastern equatorial Indian Ocean (EEI). The area of a large inclination anomaly in the western equatorial Pacific (WEP) does not extend to the Indian Ocean. The model of long-term inclination variations that a weaker dipole field causes a larger relative contribution of persistent non-dipole components is supported. Less

1. 我们研究了海洋沉积物中磁性颗粒之间静磁相互作用的强度，在强相对古强度估计中，IRM 比 ARM 更适合标准化沉积物 NRM 采集效率的差异，因为 ARM 采集受静磁相互作用的影响。2．西北太平洋最近250 kyr的古强度叠加为了获得可靠的相对古强度记录，有必要排除由于磁性矿物溶解而受到影响的地层。 S比代表低矫顽力磁性矿物的比例，对磁铁矿溶解很敏感，因此可以用于检测此类层位。3．我们从沉积物中获得了最近1.6 m.y的相对古强度记录。将该核心的古强度和磁性与西赤道太平洋的相对古强度进行了比较。而利用小波变换进行的时间序列分析表明，古强度记录存在100 kyr时间尺度的变化，磁学性质的变化与古强度的变化并不同步，两者之间不存在显着的相关性。两者即使具有 100 kyr 的共同时间尺度，我们因此得出结论，古强度记录中的 100 kyr 变化是地磁起源，而不是由磁性引起的。古气候变化引起的沉积物变化。4.从赤道东印度洋（EEI）的岩心中恢复了过去800 kyr的古强度和倾角变化。不延伸到印度洋。支持较弱的偶极子场导致持久非偶极子分量的相对贡献较大的长期倾角变化模型。