Hit or miss - Meteorite impacts in the Cretaceous Western Interior Sea: Sedimentological and paleoecological response

西部内海西临落基山脉，东临加拿大地盾，是白垩纪时期覆盖北美西部的动态陆表海，标志着全球海平面上升。在整个白垩纪，海道的古地理边界发生了显著变化。海洋群落对古海洋学和古地理变化（动物迁徙路线的开启和关闭）、基质和氧气变化驱动的波动的古生态条件做出了响应。在沉积物供应少的地区，如盆地东缘，在广泛的页岩包体中，粒度较粗的层间通常由形成生物碎屑层的磷酸盐脊椎动物碎屑的高浓度来识别。这些生物碎屑层或骨床的起源，其中一些被认为是全盆地的，被解释为波浪侵蚀面或海侵滞后沉积。我们假设，这些骨床中的一些是海啸沉积物的结果，这些沉积物是由两颗陨石产生的，它们要么直接撞击了西部内陆航道，要么就落在了附近。这些是公元前91年在阿尔伯塔省的斯汀河陨石坑和公元前99年在萨斯喀彻温省的后海湾陨石坑。生物对灾难性事件的反应将通过观察几个化石群来研究，包括脊椎动物组合、有孔虫、钙质纳米化石和鞭毛虫。方法将包括详细的岩石学和地球化学分析，以寻找陨石撞击指标（冲击石英，陨石等），脊椎动物遗骸的地面学研究，以及高分辨率的微动物分析，以涵盖这些事件。我们在西部内海的研究将区分那些形成重要海平面相关的层位，盆地范围的层序边界，用于电缆测井相关性和更随机的事件层。地球上最近发生的海啸事件将被广泛研究其对生态系统的影响。因此，识别古代海啸沉积物，其范围和对盆地生态和海洋生物形式的影响成为一项令人兴奋的努力。

The Western Interior Sea bordered by the Rocky Mountains to the West and the Canadian Shield to the East was a dynamic epicontinental sea covering Western North America during the Cretaceous Period marked by global high sea levels. Throughout the Cretaceous the seaway's paleogeographic boundaries varied significantly. Marine communities responded to fluctuating paleoecological conditions that were driven by paleoceanographic and paleogeographic changes (opening and closing of faunal migration routes), substrate and oxygen variations. In areas of low sediment supply such as the eastern margin of the basin coarser grained intervals within extensive shale packages are often recognized by their high concentration of phosphatic vertebrate debris forming bioclastic layers. The origin of these bioclastic horizons or bonebeds, some of them recognized basinwide, has been explained as wave erosional surfaces or transgressive lag deposits. We hypothesize that some of these bonebeds are the result of tsunami deposits that were generated by two meteorites that either directly hit the Western Interior Seaway or landed in close proximity. These are the Steen River Crater in Alberta dated 91 MA and the Deep Bay Crater in Saskatchewan dated 99 MA. Biotic responses to a catastrophic event will be investigated by looking at several fossil groups including vertebrate assemblages, foraminifera, calcareous nannofossils and dinoflagellates. Methods will include detailed petrographic and geochemical analysis in the search of meteorite impact indicators (shocked quartz, tektites etc.), taphonomic studies of vertebrate remains, and high resolution microfaunal analysis in order to bracket these events. Our studies in the Western Interior Sea will distinguish between those horizons that form important sea level related, basin-wide sequence boundaries serving for wireline log correlations and more random event beds. Recent tsunami events on earth will be extensively studied for their impact on ecological systems. Consequently, recognition of ancient tsunami deposits, their extent and impact on basin ecology and marine life forms becomes an exciting endeavor.