TRANS-ATLANTIC REDOX RECORDS THROUGH A MID-SILURIAN EXTINCTION EVENT

The Homerian Stage (upper Wenlock) of the Silurian has become associated with a rapid succession of extinction events that affected both planktic and (nekto)benthic organisms (the ‘Big Crisis’, ‘lundgreni Event’, ‘Mulde Event’). This mid-Silurian extinction interval coincides globally with a distinct positive carbon isotope excursion (CIE) and shifts in lithofacies signaling notable changes in sea level. A variety of interpretations have been brought forward to explain faunal turnover patterns and/or the CIE; sea-level records collectively indicate eustatic influence, and changes in climatic and oceanographic conditions are commonly invoked. Widespread marine anoxia has repeatedly been suggested as an important ‘kill mechanism’. We propose to test this and other scenarios by analyzing a suite of geochemical proxies across the extinction interval. Here we focus on a carbonate section at the Roberts Mountains, Nevada, USA, to pair δ¹³C with I/Ca and δ³⁴S_CAS (carbonate-associated sulfate) analyses in order to gain valuable information about paleoredox conditions. Additionally, we pair δ¹³C records with Fe speciation, trace metals, and δ³⁴S_pyrite analyses from time-equivalent strata of the shale-dominated Priekule drill core from Latvia. High-resolution multi-proxy data sets from two paleocontinents (Baltica & Laurentia) and sedimentary basins, together with distinctive lithologic successions and geochemical tools, will help to disentangle local/regional from global patterns of environmental and paleoredox perturbations.