COLLABORATIVE RESEARCH: Ordovician and Silurian Explosive Volcanism in the Lapetus Region: Tectonomagmatic, Tectonic,Event-Stratigraphic & Biological Implications

这项研究将在奥陶纪和 志留纪爆发形成的火山灰， 北美东部和欧洲西北部， 解决一些关于起源的基本问题， 这些灰床的分布相对于关闭的 土卫八海洋，以及它们对大灭绝的影响 海洋生物群。 地球化学的庞大数据库， 岩石学、地层学和古生物学信息 提供了一个独特的机会，了解构造岩浆 大量长英质俯冲的框架 相关的火山灰被注入平流层， 分布在波罗的海、阿瓦隆尼亚和 劳伦蒂亚 很明显，火山活动的主要中心 沿着土卫八的边缘从奥陶纪到志留纪的时间，但 这些中心的时间和位置还不太清楚。 我们将特别关注我们现在认为是单一的， 在两个大陆上沉积火山灰的超布里尼安喷发事件 土卫八的边缘，可能来自同一个弧 起源于新英格兰南部的阿蒙诺火山。 解决这些问题将提供新的澄清信息 关于影响土卫八边缘的构造事件 此外，我们建议评估事件地层和 这些事件的生物学意义，通过选择，详细的研究 广泛分布的奥陶纪和志留纪钾镁矾 年龄化学指纹和动物群研究 承认 大西洋两岸的一个或多个火山灰床将成为 对促进跨大西洋地层学发展重要贡献 奥陶系与志留系地层对比 最后，在一个 努力提供更多关于尘埃云 全球性的大规模毁灭性武器和轻武器扩散对 生物的主要群体，我们将研究的证据， 生物大规模灭绝可能是由于 这些灾难性的喷发

The study will continue and expand upon work on Ordovician and Silurian explosively formed volcanic ashes which occur both in eastern North America and northwestern Europe for the purpose of resolving some fundamental questions concerning the origin and distribution of these ash beds relative to the closing of the Iapetus Ocean, and the effect they may have had on mass extinction of marine biota. The enormous database of geochemical, petrographic, stratigraphic and paleontological information provides a unique opportunity to understand the tectonomagmatic framework within which large quantities of felsic subduction- related ash was injected into the stratosphere and widely distributed across large portions of Baltica, Avalonia and Laurentia. It is clear that major centers of volcanism changed along the margins of Iapetus from Ordovician to Silurian time, but the timing and location of these centers is not well understood. We will look particularly at what we now believe to be a single, ultraplinian eruptive event which deposited ash on both continental margins of Iapetus and may have been derived from the same arc source as the Ammonoosuc Volcanics of southern New England. Resolving these questions will provide new clarifying information about the tectonic events affecting the margin of Iapetus. Further, we propose to evaluate the event-stratigraphic and biologic implications of these events by selected, detailed studies of widespread Ordovician and Silurian K-bentonites using isotopic ages, chemical fingerprinting, and faunal studies. Recognition of one or more ash beds of both sides of the Atlantic will be an important contribution to furthering trans-Atlantic stratigraphic correlation of Ordovician and Silurian strata. Finally, in an effort to provide more insight into the likelihood that dust clouds of global proportions have deleterious and long-lasting effects on major groups of organisms, we will examine the evidence for biological mass extinctions that may have occurred as a results of these catastrophic eruptions.