The Alamo Event: Widespread Devonian Breccia of Probable Cataclysmic Origin, Southeastern Nevada

内华达州东南部Guilmette组的一个神秘的石灰岩角砾岩将被调查。Guilmette组跨越晚泥盆世frasian - fammenian阶段边界。角砾岩暴露在至少5000平方英里的七个范围内，已知厚度从25英尺到435英尺不等；它的体积为100立方英里或更多。角砾岩似乎是一个单一的沉积碳酸盐岩层，不是构造、成岩作用或溶液衍生的。它有一个尖锐的、冲刷过的基底，并含有随意定向的、岩性不均匀的向上细化的碎屑。一些碎片的最长尺寸达到50英尺或更多。角砾岩产于浅水海相环境，根据上、下床的特征判断。它暗示了灾难性的起源，可能与撞击地球的外星物体有关。通过对角砾岩上、下伏层的地层分析，细化其古地理背景，探讨角砾岩及其意义；表征其内部特性，以确定物源、运输和沉积机制，并检验单一事件假说；通过更紧密的生物地层分带缩小其年龄；寻找与可能的地外起源的联系，例如，震荡石英，地球化学异常等。

An enigmatic limestone breccia in the Guilmette Formation of southeastern Nevada will be investigated. The Guilmette Formation spans the Late Devonian Frasnian-Famennian stage boundary. The breccia is exposed in seven ranges over at least 5000 square miles and has known thicknesses ranging from 25 to 435 feet; it encompasses a volume of 100 cubic miles or more. The breccia appears to be a single sedimentary carbonate bed not tectonically, diagenetically, or solution-derived. It has a sharp, scoured base, and contains haphazardly oriented, lithologically heterogeneous clasts that fine-upward. Some clasts reach 50 feet or more in longest dimension. The breccia occurs in a shallow-water marine setting, based on characteristics of overlying and underlying beds. It suggests catastrophic origin, perhaps related to an extraterrestrial object impacting Earth. The breccia and its significance will be investigated through: stratigraphic analysis of overlying and underlying beds to refine its paleogeographic setting; characterization of its internal properties to determine provenance, transporting and depositing mechanisms, and to test the single-event hypothesis; narrowing its age designation through closer biostratigraphic zonation; searching for links to possible extraterrestrial genesis, e.g., shocked quartz, geochemical anomalies, etc.