Evidence from central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis
Evidence from central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis
复制标题
DOI：
10.1073/pnas.1110614109
复制
发表时间：
2012-03-27
影响因子：
11.1
通讯作者：
Wolbach, Wendy S.
中科院分区：
文献类型：
--
作者：
Israde-Alcantara, Isabel;Bischoff, James L.;Wolbach, Wendy S.
我们报告在墨西哥中部的屈伊泽奥湖发现了一个黑色的、富含碳的湖相层，其中含有纳米金刚石、微球体和其他不寻常的物质，这些物质可以追溯到新仙女木早期，并被解释为是外星撞击的结果。这些代用品是在一个27米长的岩芯中发现的，这是跨学科努力的一部分，目的是提取前一个间冰期的古气候记录。我们的注意力早期集中在一个异常的，10厘米厚，富碳层在2.8米的深度，可追溯到12.9万年，并符合一套异常的同时代的环境和生物的变化，独立承认在其他区域湖泊序列。总的来说，这些变化产生了最独特的边界层在晚第四纪记录。这一层包含了一个多样化的，丰富的组合的影响相关的标志物，包括纳米金刚石，碳球，并具有快速熔化/淬火纹理的磁性小球，所有达到同步峰值下的一层包含最大的木炭在核心。通过多种方法的分析表明存在三种纳米金刚石的同素异形体：n-金刚石，i-碳和六方纳米金刚石（lonsdaleite），以估计的相对丰度的顺序。这个富含纳米金刚石的层与在北美，格陵兰岛和西欧的许多地点发现的新仙女木边界层一致。我们已经研究了多种假设来解释这些观察结果，发现这些证据不能用任何已知的地球机制来解释。然而，这与新仙女木边界撞击假说相一致，该假说假设在12.9 ka时发生了一次重大的地外撞击，涉及多次空中爆炸和/或地面撞击。
We report the discovery in Lake Cuitzeo in central Mexico of a black, carbon-rich, lacustrine layer, containing nanodiamonds, microspherules, and other unusual materials that date to the early Younger Dryas and are interpreted to result from an extraterrestrial impact. These proxies were found in a 27-m-long core as part of an interdisciplinary effort to extract a paleoclimate record back through the previous interglacial. Our attention focused early on an anomalous, 10-cm-thick, carbon-rich layer at a depth of 2.8 m that dates to 12.9 ka and coincides with a suite of anomalous coeval environmental and biotic changes independently recognized in other regional lake sequences. Collectively, these changes have produced the most distinctive boundary layer in the late Quaternary record. This layer contains a diverse, abundant assemblage of impact-related markers, including nanodiamonds, carbon spherules, and magnetic spherules with rapid melting/quenching textures, all reaching synchronous peaks immediately beneath a layer containing the largest peak of charcoal in the core. Analyses by multiple methods demonstrate the presence of three allotropes of nanodiamond: n-diamond, i-carbon, and hexagonal nanodiamond (lonsdaleite), in order of estimated relative abundance. This nanodiamond-rich layer is consistent with the Younger Dryas boundary layer found at numerous sites across North America, Greenland, and Western Europe. We have examined multiple hypotheses to account for these observations and find the evidence cannot be explained by any known terrestrial mechanism. It is, however, consistent with the Younger Dryas boundary impact hypothesis postulating a major extraterrestrial impact involving multiple airburst(s) and and/or ground impact(s) at 12.9 ka.