Data report: evaluation of shipboard magnetostratigraphy by alternating field demagnetization of discrete samples, Expedition 361, Site U1475

J. Just
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Abstract

The paleomagnetic shipboard data of International Ocean Discovery Program Site U1475, with a record reaching back to approximately 7 Ma, allowed for the identification of major magnetic polarity chrons and subchrons back to ~3.5 Ma. However, the natural remanent magnetization (NRM) was very weak, and transitional intervals with unclear polarity were as thick as several meters. The midpoints of these transitional intervals were reported in the shipboard results without decimal places because of the poor data quality. To evaluate and possibly refine the shipboard magnetostratigraphy, subsampling was performed across the polarity transitions. Detailed alternating field (AF) demagnetization experiments were conducted on these discrete samples and were complemented by anhysteretic remanent magnetization acquisition measurements and subsequent demagnetization. AF demagnetization data of NRM were analyzed using anchored principal component analysis (PCA) to obtain the characteristic remanent magnetization. These PCA results generally confirm the smoothed signal across polarity transitions at Site U1475. However, the midpoint depths of the top of the Keana Subchron, the Gauss-Matuyama and Matuyama-Brunhes boundaries, and the base of the Olduvai Subchron were adjusted.
资料报告:用离散样品的交变磁场消磁评价船上磁地层,361考察队,地点U1475
利用国际海洋发现计划U1475站点的古地磁船载数据,可追溯到约7 Ma的记录,可以确定~3.5 Ma的主要磁极性时线和亚时线。然而,自然剩余磁化(NRM)非常弱,极性不明确的过渡间隔厚达几米。由于数据质量差,这些过渡区间的中点在船上结果中没有小数点。为了评估并可能改进船上磁地层学,在极性转换期间进行了次采样。在这些离散样品上进行了详细的交变磁场(AF)退磁实验,并辅以非滞后剩磁采集测量和随后的退磁。采用锚定主成分分析(PCA)对NRM的AF消磁数据进行分析,得到其特征剩余磁化强度。这些PCA结果一般证实了U1475站点极性转换的平滑信号。然而,Keana subchren顶部、gaas - matuyama和Matuyama-Brunhes边界和Olduvai subchren底部的中点深度进行了调整。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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