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

这项研究将继续并扩大对奥陶纪和志留纪爆炸形成的火山灰的研究，这些火山灰发生在北美东部和欧洲西北部，目的是解决有关这些火山灰床的起源和分布与Iapetus海洋关闭有关的一些基本问题，以及它们可能对海洋生物的大规模灭绝产生的影响。庞大的地球化学、岩石学、地层学和古生物学信息数据库为了解构造岩浆框架提供了一个独特的机会，在这个框架中，大量与长英质俯冲有关的火山灰被注入平流层，并广泛分布在波罗的海、阿瓦洛尼亚和劳伦西亚的大部分地区。很明显，从奥陶纪到志留纪，沿Iapetus边缘的主要火山活动中心发生了变化，但这些中心的时间和位置尚不清楚。我们将特别关注我们现在认为是单一的、多隆起的喷发事件，它在土卫八的两个大陆边缘沉积了火山灰，可能与新英格兰南部的阿莫努苏火山来自同一个弧源。解决这些问题将为了解影响土卫八边缘的构造事件提供新的澄清信息。此外，我们建议通过对广泛分布的奥陶系和志留系k -膨润土进行同位素年龄、化学指纹和动物区系研究，以评估这些事件的事件地层学和生物学意义。识别大西洋两岸的一个或多个灰层，将对进一步开展奥陶系和志留系跨大西洋地层对比具有重要意义。最后，为了更深入地了解全球规模的尘埃云对主要生物群体产生有害和持久影响的可能性，我们将研究这些灾难性喷发可能导致生物大规模灭绝的证据。

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.