TRACE ELEMENT GEOCHEMISTRY OF THE GIVETIAN-FRASNIAN FRASNES EVENT, NEVADA, USA

The Devonian is punctuated by a large number of global biogeochemical events marked by widespread black shale deposition coeval with positive carbon isotope excursions and mass extinctions. The “Big 5” Frasnian-Famennian and end-Devonian (Hangenberg) events have been the focus of extensive sedimentological, paleobiological, and geochemical studies to understand their signals and mechanisms. For example, whole-rock geochemical data through both the F-F and Hangenberg events shows significant enrichment in redox-sensitive trace elements. This enrichment has been linked to widespread anoxia and recent Hg data suggest a possible volcanic driver. However, the majority of Devonian biogeochemical events have been critically understudied and are consequently poorly understood. The Givetian-Frasnian "Frasnes" event (a second-order mass extinction with widespread black shale deposition) and the associated falsiovalis positive carbon isotope excursion is one such example. This event is recorded in carbonate rocks in the Denay Fm. (Northern Antelope Range, NV). Here we present new ICP-MS bulk-rock geochemical analyses of redox-sensitive trace elements (e.g., Mo, V, Cr, Mo/Al, Fe/Al) from the Denay samples that allows evaluation of the Frasnes as a potential oceanic anoxic event and facilitates comparison to the well-known Late Devonian global biogeochemical events.