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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Secular variation study from non-welded pyroclastic deposits from Montagne Pelee volcano, Martinique (West Indies)
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Secular variation study from non-welded pyroclastic deposits from Montagne Pelee volcano, Martinique (West Indies)

机译：马提尼克岛（西印度群岛）Montagne Pelee火山的非焊接热碎屑沉积的长期变化研究

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摘要

We present palaeomagnetic data obtained from large clasts collected in non-welded pyroclastic deposits from Montagne Pelee volcano (Martinique Island, West Indies). These deposits, dated by the ~(14)C method from 5000 yr BP to the present, comprise block- and ash-flows, ash- and pumice-flows and pumice fallouts. Alternating fields treatment was as a routine chosen to demagnetise large samples for which the magnetisation was measured with a specially designed inductometer. The mean directions obtained from block- and ash-flow deposits of the 1902 and 1929 eruptions are in good agreement with the expected geomagnetic directions at these times in Martinique. The so-called P1 eruption (～1345 AD), which is characterised by a rarely observed transition from a Peleean to a Plinian eruptive style, allows a direct comparison of the palaeomagnetic directions obtained form the three types of pyroclastic deposits. All deposits provide identical mean directions, which further demonstrates the suitability of the non-welded pyroclastic deposits for geomagnetic secular variation study with a very good accuracy and precision. The possibility of using pyroclastic deposits is promising for obtaining a wider distribution of sampling sites, which may better allow us to constrain our knowledge on the geomagnetic secular variation. We find that large geomagnetic changes occurred in Martinique during the last millennium, while the variations appear more limited prior to this period.
机译：我们展示了从蒙塔涅佩里火山（西印度群岛马提尼克岛）的非焊接热碎屑沉积物中收集的大碎屑获得的古地磁数据。这些沉积物是通过〜（14）C方法测得的，从5000 yr BP至今，包括块状和灰分流，灰分和浮石流以及浮石沉淀。常规选择交变磁场处理来对大型样品进行消磁，并使用专门设计的感应仪测量其磁化强度。从1902年和1929年喷发的块状流和灰分流沉积获得的平均方向与这些时期马提尼克岛的预期地磁方向非常一致。所谓的P1喷发（约1345 AD）的特征是很少见到从Peleean到Plinian喷发型转变，它可以直接比较从三种类型的火山碎屑沉积获得的古磁方向。所有沉积物均提供相同的平均方向，这进一步证明了非焊接热碎屑沉积物非常适合地磁长期变化研究。使用火成碎屑沉积物的可能性有望获得更广泛的采样点分布，这可能更好地使我们限制对地磁长期变化的认识。我们发现，在上个千年中，马提尼克岛发生了较大的地磁变化，而在此之前，变化似乎更为有限。

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