Geomagnetic excursions and paleointensities in the Matuyama Chron at Ocean Drilling Program Sites 983 and 984 (Iceland Basin)
Geomagnetic excursions and paleointensities in the Matuyama Chron at Ocean Drilling Program Sites 983 and 984 (Iceland Basin)
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DOI：
10.1029/2001jb000491
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发表时间：
2002-06-01
影响因子：
3.9
通讯作者：
Raymo, ME
中科院分区：
文献类型：
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作者：
Channell, JET;Mazaud, A;Raymo, ME
[1]我们报告的自然反射磁化（NRM）方向和地磁古强度代理的松山时（0.9-2.2马的时间间隔）的一部分，从两个地点位于沉积物漂移在冰岛盆地。在大洋钻探计划983号和984号站点，松山时代晚期的平均沉积速率分别为15.9和11.5 cm kyr（-1）。对于较老的部分记录（>1.2 Ma），氧同位素数据太稀疏，无法提供年龄模型构建的唯一基础。体积磁化率记录和参考δ（18）O记录的相似性使我们将这两个记录进行匹配，从而得出年龄模型。根据983/984号站点的磁化率，这一匹配与983/984号站点的海底三角洲（18）O数据一致。古强度代理来自NRM与无滞后剩磁曲线的斜率，在30-60 mT的峰值磁场范围内的交变磁场退磁。古强度低对应的极性反转的限制，Jaramillo，Olduvai，科布山，留尼汪Subchrons和七个游览NRM组件的方向。在932、1048、1115、1190-1215（科布山亚时）、1255、1472-1480、1567-1575（吉尔萨亚时）和1977 ka观测到磁偏移（此处定义为穿过虚拟地磁赤道的虚拟地磁极纬度）。结果表明，地磁方向漂移，与古强度最小值，是松山时的一个特点，并可能极性时一般。
[1] We report natural remanent magnetization (NRM) directions and geomagnetic paleointensity proxies for part of the Matuyama Chron (0.9-2.2 Ma interval) from two sites located on sediment drifts in the Iceland Basin. At Ocean Drilling Program Sites 983 and 984, mean sedimentation rates in the late Matuyama Chron are 15.9 and 11.5 cm kyr(-1), respectively. For the older part of the record (>1.2 Ma), oxygen isotope data are too sparse to provide the sole basis for age model construction. The resemblance of the volume susceptibility record and a reference delta(18)O record led us to match the two records to derive the age models. This match, based on Site 983/984 susceptibility, is consistent with available Site 983/984 benthic delta(18)O data. Paleointensity proxies were derived from the slope of the NRM versus anhysteretic remanent magnetization plot for alternating field demagnetization in the 30-60 mT peak field range. Paleointensity lows correspond to polarity reversals at the limits of the Jaramillo, Olduvai, Cobb Mountain, and Reunion Subchrons and to seven excursions in NRM component directions. Magnetic excursions (defined here by virtual geomagnetic polar latitudes crossing the virtual geomagnetic equator) are observed at 932, 1048, 1115, 1190-1215 (Cobb Mountain Subchron), 1255, 1472-1480, 1567-1575 (Gilsa Subchron), and 1977 ka. The results indicate that geomagnetic directional excursions, associated with paleointensity minima, are a characteristic of the Matuyama Chron and probably of polarity chrons in general.