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首页> 外文期刊>Earth, planets and space: EPS >Paleointensity data from Early Cretaceous Ponta Grossa dikes (Brazil) using a multisample method
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Paleointensity data from Early Cretaceous Ponta Grossa dikes (Brazil) using a multisample method

机译：利用多样本方法获得的早白垩世蓬塔格罗萨堤防（巴西）的古强度数据

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摘要

Definition of the long-term variation of the geomagnetic virtual dipole moment requires more reliable paleointensity results. Here, we applied a multisample protocol to the study of the 130.5 Ma Ponta Grossa basaltic dikes (southern Brazil) that carry a very stable dual-polarity magnetic component. The magnetic stability of the samples wits checked using thermomagnetic curves and by monitoring the magnetic Susceptibility evolution through the paleointensity experiments. Twelve sites containing the least alterable samples were chosen for the paleointensity measurements. Although these rocks failed stepwise double-heating experiments, they yielded coherent results in the multisample method for all sites but one. The coherent sites show low to moderate field intensities between 5.7 +/- 0.2 and 26.4 +/- 0.7 mu T (average 13.4 +/- 1.9 mu T). Virtual dipole moments for these sites range from 1.3 +/- 0.04 to 6.0 +/- 0.2 x 10(22) A m(2) (average 2.9 +/- 0.5 x 10(22) A m(2)). Our results agree with the tendency for low dipole moments during the Early Cretaceous, immediately prior to the Cretaceous Normal Superchron (CNS). The available paleointensity database shows a strong variability of the field between 80 and 160 Ma. There seems to be no firm evidence for a Mesozoic Dipole Low, but a long-term tendency does emerge from the data with the highest dipole moments Occurring at the middle of the CNS.
机译：定义地磁虚拟偶极矩的长期变化需要更可靠的古强度结果。在这里，我们采用了多样本方案来研究130.5 Ma Ponta Grossa玄武岩（巴西南部），它们具有非常稳定的双极性磁性成分。使用热磁曲线和通过古强度实验监测磁化率演变来检查样品的磁稳定性。选择十二个包含最少可变样品的位点进行古强度测量。尽管这些岩石未能通过分步两次加热实验，但它们在多样品方法中对除一个以外的所有位置产生了连贯的结果。相干位点显示的中低场强介于5.7 +/- 0.2和26.4 +/- 0.7μT之间（平均13.4 +/- 1.9μT）。这些位置的虚拟偶极矩范围为1.3 +/- 0.04至6.0 +/- 0.2 x 10（22）A m（2）（平均2.9 +/- 0.5 x 10（22）A m（2））。我们的结果与白垩纪早于正白垩纪超同步（CNS）之前白垩纪早期低偶极矩的趋势一致。可用的古强度数据库显示该场在80至160 Ma之间有很强的可变性。似乎没有确凿的证据表明中生代偶极子低，但是从中枢神经系统中部偶极矩最大的数据中确实发现了长期趋势。

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