Geomagnetic events and relative palaeointensity variations during the past 300 ka as recorded in Kolbeinsey Ridge sediments, Iceland Sea: indication for a strongly variable geomagnetic field
Geomagnetic events and relative palaeointensity variations during the past 300 ka as recorded in Kolbeinsey Ridge sediments, Iceland Sea: indication for a strongly variable geomagnetic field
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DOI：
10.1007/s005310050250
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发表时间：
1999-05
影响因子：
2.3
通讯作者：
N. Nowaczyk;T. Frederichs
中科院分区：
文献类型：
--
作者：
N. Nowaczyk;T. Frederichs
对科尔拜西岭地区5个沉积物岩心的磁地层学分析显示，在过去300 ka内，几个与低相对古强度相关的地磁事件的记录是一致的。对各种岩石磁性参数的解释清楚地排除了记录的非正常极性方向与偏离的磁矿学部分或扭曲的磁性结构有关的可能性。因此，这些方向被解释为地磁场变化的真实记录。磁滞参数和热磁测量结果表明，残余载体矿物为纯伪单畴（PSD）磁铁矿，居里温度580℃。由于岩石磁性参数的均匀性，沉积物也适合于相对古强度的测定。其中两个岩心的氧同位素地层学为估计记录的地磁场变化的年龄范围提供了一个时间框架。在过去300 ka的10次持续时间长达12 ka的事件记录和相关的相对古强度记录表明，地球磁场具有相当动态的特征，这与已发表的极性时间尺度明显相反。
Magnetostratigraphic analyses of five sediment cores recovered from the Kolbeinsey Ridge area revealed consistent records of several geomagnetic events linked with low relative palaeointensities within the past 300 ka. Interpretation of various rock magnetic parameters clearly rule out the possibility that the recorded non-normal polarity directions are linked to a deviating magnetomineralogical fraction or a distorted magnetic fabric. Therefore, these directions are interpreted as true recordings of geomagnetic field variations. Hysteresis parameters and thermomagnetic measurements revealed pure pseudo single-domain (PSD) magnetite with Curie temperatures of 580 °C as the dominant remanence carrier mineral. Due to the homogeneity of the rock magnetic parameters, the sediments are also suitable for relative palaeointensity determinations. Oxygen-isotope stratigraphies for two of the cores provided a time frame to estimate the age ranges for the recorded geomagnetic field variations. The obtained record of ten events of up to 12 ka duration during the past 300 ka and the related record of relative palaeointensity indicate a fairly dynamic character of the Earth's magnetic field, which is in clear contrast to published polarity time scales.