Palaeomagnetism of the AND-1B Core, ANDRILL McMurdo Ice Shelf Project, Antarctica
Palaeomagnetism of the AND-1B Core, ANDRILL McMurdo Ice Shelf Project, Antarctica
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AND-1B 核心的古地磁学，ANDRILL 麦克默多冰架项目，南极洲
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
C. Ohneiser
中科院分区：
文献类型：
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作者：
G. Wilson;F. Florindo;L. Sagnotti;C. Ohneiser
给出了AND-1B钻芯的初步古地磁数据。在回收和裂解后立即从钻芯中采集了1309个样品。所有样品的自然剩余磁化(NRM)和块体磁化率数据分别在收集后立即使用MolSpner磁强计和Bartington Instruments磁化率电桥测定。从615个阶梯交变磁场(AF)和热退磁样品中测定了钻芯上部700m的极性，样品的平均间距为~80 cm，样品间距在32~240 Mbsf之间，平均样品间距在240~700 Mbsf之间，平均间距为~2m。在奥塔哥大学和火山研究所的2G Enterprise长芯低温磁强计上测量了逐步退磁的样品。在32.33和700mBsf之间的间隔内构建了磁极分带，其中表示大致相等的正极和反极。在32.33Mbsf以上，疏松的英云闪长岩层阻碍了样品的采集。其余记录被细分为15个磁区(8个正常，7个反转)。磁臭氧边界在相反极性的样品之间的中点处或由过渡极性的样品界定。在正交分量图上不可能分离出特征剩磁(ChRM)方向，因此在岩心的几个~10m间隔内也不可能分离出极性。未来的工作将包括确定钻芯下部585米的极性分区，并将数据间距减半，介于240至700 Mbsf之间。
Preliminary palaeomagnetic data are presented for the AND-1B drill core. A total of 1309 samples were collected from the drill core immediately following recovery and splitting. Natural remanent magnetisation (NRM) and bulk magnetic susceptibility data were determined for all samples using a Molspin spinner magnetometer and Bartington Instruments susceptibility bridge, respectively, immediately after collection. Polarity was determined for the upper 700 m of the drill core from 615 stepwise alternating fi eld (AF) and thermally demagnetized samples with an average sample spacing of ~80 cm between 32 and 240 mbsf and ~2 m between 240 and 700 mbsf. Stepwise demagnetised samples were measured on 2G Enterprises long-core cryogenic magnetometers at the University of Otago and the Istituto di Geofi sica e Vulcanologia. A magnetic polarity zonation was constructed for the interval between 32.33 and 700 mbsf, with roughly equal normal and reversed polarity represented. Above 32.33 mbsf, poorly consolidated diamictite strata prevented sample collection. The remaining record was subdivided into 15 magnetozones (8 normal and 7 reversed). Magnetozone boundaries are defi ned at the midpoint between samples of opposite polarity or by samples with transitional polarity. It was not possible to isolate characteristic remanence (ChRM) directions on orthogonal component plots and hence polarity for several ~10 m intervals in the core. Future work will include determination of a polarity zonation for the lower 585 m of the drill core and halving data spacing between 240 and 700 mbsf.