Relative geomagnetic paleointensity and δ18O at ODP Site 983 (Gardar Drift, North Atlantic) since 350 ka
Relative geomagnetic paleointensity and δ18O at ODP Site 983 (Gardar Drift, North Atlantic) since 350 ka
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DOI：
10.1016/s0012-821x(97)00164-7
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发表时间：
1997-12
影响因子：
5.3
通讯作者：
J. Channell;D. Hodell;B. Lehman
中科院分区：
文献类型：
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作者：
J. Channell;D. Hodell;B. Lehman
在ODP 983站，获得了35万年以来的相对地磁古强度、南极和海底δ 18 O记录。该区间的平均沉积速率为11.3 cm/kyr。磁性能和磁滞回线表明，准单畴磁铁矿是剩磁载体。体积磁化率（k）、无磁滞（ARM）和等温（EMT）剩磁值变化3-4倍，完全在古强度研究通常引用的标准范围内。利用ARM和BEM对天然反射磁化强度（NRM）进行归一化处理，获得古强度代用指标。在25-45 mT范围内，计算出5个退磁步骤的NRM/ARM和NRM/NRM的算术平均值，构成了相对古强度估计值。一些古强度低（特别是在400，120和188 ka）与磁场的方向偏移有关，特别是188 ka的事件（这里称为冰岛盆地事件），它构成了一个短暂的极性反转。对于过去的200 kyr，记录可以与其他高分辨率的古强度记录，如拉布拉多海，地中海/索马里盆地和苏禄海，这意味着千年尺度的功能是全球同步的。提出了一个标记系统的古强度功能，关系突出的高点和低点的氧同位素阶段。
At ODP Site 983, relative geomagnetic paleointensity and planktic and benthic δ18O records have been acquired for the last 350 kyr. The mean sedimentation rate in this interval is 11.3 cm/kyr. Magnetic properties and hysteresis ratios indicate that pseudo-single domain magnetite is the remanence carrier. Volume susceptibility (k), anhysteretic (ARM) and isothermal (IRM) remanence values vary by a factor of 3–4, well within the criteria usually cited for paleointensity studies. Natural remanent magnetization (NRM) is normalized by ARM and IRM to acquire the paleointensity proxy. Arithmetic means of NRM/ARM and NRM/IRM, calculated for five demagnetization steps in the 25–45 mT range, constitute the relative paleointensity estimates. Some paleointensity lows (particularly those at ∼40, ∼120 and ∼188 ka) are associated with directional excursions of the field, especially the event at ∼188 ka (referred to here as the Iceland Basin Event) that constitutes a short-lived polarity reversal. For the last 200 kyr, the records can be correlated with other high-resolution paleointensity records such as those from the Labrador Sea, Mediterranean/Somali Basin and Sulu Sea, implying that the millennial scale features are globally synchronous. A labeling system for paleointensity features is proposed that ties prominent highs and lows to oxygen isotope stages.