Absence of preferred longitude sectors for poles from volcanic records of geomagnetic reversals
Absence of preferred longitude sectors for poles from volcanic records of geomagnetic reversals
复制标题
地磁反转的火山记录中缺乏极地的首选经度扇区
作者：
M. Prévôt;P. Camps
根据最近对过去1200万年的沉积记录的汇编，反向地磁场显示出明显的长期纵向组织，这似乎与下地幔的热结构有关。然而，至关重要的古地磁观测，中间虚拟地磁极优先限于美洲或对映本sector 2，3的赤道，可能是一个人为造成的失真和平滑的地磁信号的沉积物4 -6。在这里，我们提出了一个汇编的121个火山记录的偏移和逆转不到1600万年的中间极点，采样在不同的纬度和纬度，这并不证实以前的推断1，并加强了怀疑4 -6沉积物的能力，以适当地记录一个快速变化的领域。与偏移产生的虚拟极点不同，反向产生的虚拟极点在经度上均匀分布，这表明反向场是统计轴对称的。因此，我们的结论是，没有证据表明过渡领域的控制下地幔温度分布。
ACCORDING to a recent compilation of sedimentary records from the past 12 Myr, the reversing geomagnetic field displays a marked long-term longitudinal organization which seems to be correlated with the thermal structure of the lower mantle1. However, the crucial palaeomagnetic observation that intermediate virtual geomagnetic poles are preferentially confined to longitudes over the Americas or antipodal to this sector2,3 might be an artefact caused by distortion and smoothing of the geomagnetic signal by sediments4–6. Here we present a compilation of ∼400 intermediate poles from 121 volcanic records of excursions and reversals less than 16 Myr old, sampled at various longitudes and latitudes, which does not confirm previous inferences1 and reinforces doubts4–6 about the ability of sediments to properly record a rapidly varying field. In contrast to virtual poles from excursions, those from reversals are uniformly distributed in longitude, which indicates that the reversing field is statistically axisymmetrical. Thus, we conclude that there is no evidence for control of transitional fields by the temperature distribution in the lowermost mantle.