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

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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.