SUMMARY
We report a survey carried out on basalt flows from Amsterdam Island (Southeastern Indian Ocean) in order to check the presence of intermediate directions interpreted to belong to a geomagnetic field excursion within the Brunhes epoch (Watkins & Nougier, 1973), completing this paleomagnetic reco...
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| Format: | Text |
| Language: | English |
| Published: |
2003
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.262.3703 http://arxiv.org/pdf/physics/0304061v1.pdf |
| Summary: | We report a survey carried out on basalt flows from Amsterdam Island (Southeastern Indian Ocean) in order to check the presence of intermediate directions interpreted to belong to a geomagnetic field excursion within the Brunhes epoch (Watkins & Nougier, 1973), completing this paleomagnetic record with paleointensity determinations and radiometric dating. Because the paleomagnetic sampling was done in few hours during the resupply of the French scientific base Martin du Viviers by the Marion Dufresne vessel, we could collected only 29 samples from 4 lava flows. The directional results corroborate the findings by Watkins & Nougier (1973) : normal polarity is found for two units and an intermediate direction, with associated Virtual Geomagnetic Poles (VGPs) close to the equator, for the other two units. A notable result is that these volcanic rocks are well suited for absolute paleointensity determinations. Fifty percent of the samples yields reliable intensity values with high quality factors. An original element of this study is that we made use of the thermomagnetic criterion PTRM-tail test of Shcherbakova et2 Carvallo et al. al. (2000) to help in the interpretation of the paleointensity measurements. Doing thus, only the high temperature intervals, beyond 400◦C, were retained to obtain the most |
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