Relative paleointensity stack during the last 250 kyr in the northwest Pacific
Relative paleointensity stack during the last 250 kyr in the northwest Pacific
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DOI：
10.1029/2006jb004477
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发表时间：
2007
影响因子：
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通讯作者：
Y. Yamamoto;T. Yamazaki;T. Kanamatsu;Noboru Ioka;T. Mishima
中科院分区：
文献类型：
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作者：
Y. Yamamoto;T. Yamazaki;T. Kanamatsu;Noboru Ioka;T. Mishima
[1] 我们对从西北太平洋回收的 10 个沉积岩芯进行了古地磁研究。目的是建立过去 250 公里的区域古强度堆栈 (NOPAPIS-250)，以覆盖全球古强度数据，并为古强度辅助地层学提供区域参考。在所研究的岩心中，磁铁矿的还原溶解似乎主要发生在冰期。这样的水平伴随着 S 比率 (S−0.3T = (1 − IRM−0.3T/SIRM)/2) 的大幅下降，低至 0.90。沉积物中还夹杂着频繁的火山灰层。在这些层位上，无法满足可靠的相对古强度估计的先决条件。我们通过基于 S 比和饱和等温剩磁 (SIRM) 的定量标准拒绝了不合适的数据，并根据剩余数据构建了 NOPAPIS-250 曲线。在构建曲线时，我们选择 IRM 作为归一化器，因为非磁滞剩磁 (ARM) 的获取被认为受到西北太平洋沉积物中磁性颗粒之间磁相互作用的影响。如果假设呈正态分布，NOPAPIS-250 的相对强度变化给出的标准偏差为平均值的 33%。与其他地区报告的其他高分辨率记录相比，NOPAPIS-250 曲线通常显示出相似的变化模式：许多古强度低点被认为是共同的。九个低点中有六个可以与文献中报道的偏差相关。
[1] We have conducted a paleomagnetic study of 10 sediment cores recovered from the northwest Pacific. The purpose is to establish a regional paleointensity stack during the last 250 kyrs (NOPAPIS-250) for global coverage of paleointensity data as well as a regional reference for paleointensity-assisted stratigraphy. In the studied cores, reductive dissolution of magnetite appears to have occurred mainly in glacial periods. Such horizons accompany large decreases in S-ratio (S−0.3T = (1 − IRM−0.3T/SIRM)/2) as low as 0.90. The sediments are also intercalated by frequent volcanic ash layers. Prerequisites for reliable relative paleointensity estimation are not satisfied at these horizons. We rejected unsuitable data by quantitative criteria based on S-ratio and saturation isothermal remanent magnetization (SIRM) and constructed the NOPAPIS-250 curve from the remaining data. In the construction of the curve, we chose IRM as a normalizer because acquisitions of anhysteretic remanent magnetization (ARM) are considered to be influenced by magnetic interactions among magnetic grains in the northwest Pacific sediments. Relative intensity variation of the NOPAPIS-250 gives a standard deviation that is 33% of the average, if the normal distribution is assumed. The NOPAPIS-250 curve generally shows similar variation patterns compared with other high-resolution records reported from other regions: many paleointensity lows are recognized in common. Six out of the nine lows can be correlated with reported excursions in literature.