Kletetschka Gunther, Ocampo Uria Adriana, Zila Vojtech, Elbra Tiiu
Institute of Geology, Czech Academy of Sciences, Rozvojová 269, Prague 6, 16500, Czech Republic.
Department of Applied Geophysics, Charles University, Albertov 6, Prague 2, 12843, Czech Republic.
Sci Rep. 2020 Jun 3;10(1):9035. doi: 10.1038/s41598-020-65974-2.
Chicxulub impact (66 Ma) event resulted in deposition of spheroids and melt glass, followed by deposition of diamectite and carbonate ejecta represented by large polished striated rounded pebbles and cobbles, henceforth, called Albion Formation Pook's Pebbles, name given from the first site identified in central Belize, Cayo District. Here we report that magnetic analysis of the Pook's Pebbles samples revealed unique electric discharge signatures. Sectioning of Pook's Pebbles from the Chicxulub ejecta from the Albion Formation at Belize showed that different parts of Pook's Pebbles had not only contrasting magnetization directions, but also sharply different level of magnetizations. Such behavior is indicative of electric discharge taking place sometimes during the formation of the Chicxulub ejecta blanket. In addition, some of the Pook's Pebbles' surface had recrystallized down to 0.2 mm depth. This is evidence of localized extreme pressures and temperatures during the fluidized ejecta formation which was imprinted in the outer layer of Pook's Pebbles. Recrystallization caused formation of nanophase iron along the surface, which was revealed by mapping of both natural remanent magnetization and of saturation remanence magnetization signatures. While the spheroids' magnetization orientation is consistent with reversed magnetic field at the time of impact, the study of the Pook's Pebbles provided, in addition, new evidence of electric charging during the vapor plume cloud processes.
希克苏鲁伯撞击（6600万年前）事件导致了球粒和熔融玻璃的沉积，随后是由大型光滑条纹圆形卵石和圆石代表的混积岩和碳酸盐喷出物的沉积，此后，这些被称为阿尔比恩组普克卵石，这个名字来源于在伯利兹中部凯约区首次发现的地点。在此我们报告，对普克卵石样本的磁性分析揭示了独特的放电特征。对来自伯利兹阿尔比恩组希克苏鲁伯喷出物的普克卵石进行切片显示，普克卵石的不同部分不仅具有相反的磁化方向，而且磁化水平也截然不同。这种行为表明在希克苏鲁伯喷出物覆盖层形成过程中的某个时候发生了放电。此外，一些普克卵石的表面已经重结晶至0.2毫米深度。这是流化喷出物形成过程中局部极端压力和温度的证据，这些压力和温度被印记在普克卵石的外层。重结晶导致沿表面形成纳米相铁，这通过天然剩磁和饱和剩磁特征的测绘得以揭示。虽然球粒的磁化方向与撞击时的反向磁场一致，但对普克卵石的研究还提供了蒸汽羽云过程中充电的新证据。
