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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Relative geomagnetic paleointensity from the Jaramillo Subchron to the Matuyama/Brunhes boundary as recorded in a Mediterranean piston core
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Relative geomagnetic paleointensity from the Jaramillo Subchron to the Matuyama/Brunhes boundary as recorded in a Mediterranean piston core

机译：地中海活塞岩心中记录的从Jaramillo次纪到Matuyama / Brunhes边界的相对地磁古强度

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摘要

Piston core LC07, located west of the Sicily Strait in the Mediterranean Sea, unambiguously records the Matuyama/Brunhes (M/B) and the upper Jaramillo polarity reversals, with similar average sediment accumulation rates (SARs) for the Brunhes Chron (2.29 cm/kyr) and late Matuyama Chron Clr. 1r (2.19 cm/kyr). We report a relative paleointensity record for the interval spanning the M/B boundary down into the Jaramillo Subchron, which is unique in the Mediterranean because existing records from this basin cover only the last 80 kyr. The average SAR in core LC07 is used to translate the depth-related paleointensity record to the time domain; the ratio of anhysteretic remanent magnetization to low-field magnetic susceptibility is climatically sensitive and is used to tune the age model. This correlation produces a good fit to the global ice volume model derived for summer insolation at 65 °N. With this age model, a paleointensity minimum in association with the M/B boundary has a duration of about 4-5 kyr, while the directional change has a duration of < 3 kyr. A second paleointensity minimum of similar duration is found about 16 kyr below the M/B boundary. This feature (precursor or 'dip' in the literature) has previously been recognized at the same time interval in many marine records, which reinforces the validity of our age model. Other relative paleointensity minima are found within chron Clr. lr, and, within the uncertainties of the respective age models, these minima coincide with those observed from the few published coeval paleointensity records. In particular, there is good correspondence between the ages of minima at about 0.92 and 0.89 Ma, which probably correlate with two geomagnetic excursions (Santa Rosa and Kamikatsura, respectively) that have been recorded in lava flows and dated using the ~(40)Ar/~(39)Ar technique. In contrast, a recently dated excursion at 0.83 Ma from La Palma seems to correspond to a paleointensity maximum. This observation is opposite to that expected and this excursion needs to be confirmed. In contrast to some recently published paleointensity records, spectral analysis of the LC07 record does not reveal identification of significant power at the orbital obliquity frequency.
机译：位于地中海西西里海峡西侧的活塞核心LC07清楚地记录了Matuyama / Brunhes（M / B）和上Jaramillo极性反转，Brunhes Chron（2.29 cm / kyr）和已故的Matuyama Chron Clr。 1r（2.19 cm / kyr）。我们报告了从M / B边界到Jaramillo Subchron的时间间隔的相对古强度记录，这在地中海地区是唯一的，因为该盆地的现有记录仅覆盖了最后80年。 LC07核心中的平均SAR用于将与深度有关的古强度记录转换为时域。迟滞剩磁与低磁场磁化率之比是气候敏感的，用于调整年龄模型。这种相关性非常适合于65°N的夏季日照导出的全球冰量模型。在这个年龄模型中，与M / B边界相关的古强度最小值的持续时间约为4-5 kyr，而方向变化的持续时间小于3 kyr。在M / B边界以下约16 kyr处发现了类似持续时间的第二个古强度最小值。此功能（文献中的“前身”或“浸入式”）先前已在许多海洋记录中以相同的时间间隔被识别，这加强了我们年龄模型的有效性。在chron Clr内发现其他相对古强度最小值。而且，在各个年龄模型的不确定性范围内，这些最小值与从少数已发表的同时期古强度记录中观察到的最小值一致。特别是，最小年龄在约0.92和0.89 Ma之间有很好的对应关系，这可能与熔岩流中记录的并使用〜（40）Ar记录的两个地磁偏移（分别为Santa Rosa和Kamikatsura）相关。 /〜（39）Ar技术。相反，最近从拉帕尔玛（La Palma）到0.83 Ma的偏移似乎与古强度最大值相对应。此观察与预期相反，因此需要确认此偏移。与最近发布的一些古强度记录相反，LC07记录的频谱分析未揭示在轨道倾角频率处的有效功率。

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