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

成败——陨石对白垩纪西部内海的影响：沉积学和古生态反应

• 批准号: 217037-2012
• 负责人: SchroderAdams, Claudia
• 金额: $ 1.97万
• 依托单位: Carleton University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=570088
• 关键词: Hit; miss; Meteorite; impacts; Cretaceous

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.

西部内海西边与落基山脉接壤，东边与加拿大地盾接壤，是白垩纪时期覆盖北美西部的动态陆表海，以全球高海平面为标志。在整个白垩纪时期，海道的古地理边界变化很大。海洋群落对由古海洋和古地理变化（动物迁徙路线的开放和关闭）、基质和氧气变化驱动的波动的古生态条件做出反应。在沉积物供应量低的地区，例如盆地的东缘，广泛的页岩包内的粗粒层段通常可以通过形成生物碎屑层的高浓度磷酸盐脊椎动物碎片来识别。这些生物碎屑层或骨床的起源（其中一些在整个盆地范围内得到认可）已被解释为波浪侵蚀面或海侵滞后沉积物。我们假设其中一些骨床是海啸沉积物的结果，这些沉积物是由直接撞击西部内海航道或在附近着陆的两块陨石产生的。它们是公元 91 年阿尔伯塔省的斯廷河陨石坑和公元 99 年位于萨斯喀彻温省的深湾陨石坑。将通过观察几个化石群来研究对灾难性事件的生物反应，包括脊椎动物组合、有孔虫、钙质超微化石和甲藻。方法将包括在寻找陨石撞击指标（冲击石英、玻璃陨石等）时进行详细的岩石学和地球化学分析、脊椎动物遗骸的埋藏学研究以及高分辨率微型动物分析，以便对这些事件进行分类。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序边界，用于电缆测井相关性和更多随机事件层的盆地范围层序边界。最近发生在地球上的海啸事件将被广泛研究其对生态系统的影响。因此，认识古代海啸沉积物、其范围及其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。