Contrasting long-term global and short-term local redox proxies during the Great Ordovician Biodiversification Event: A case study from Fossil Mountain, Utah, USA

摘要: Abstract The Great Ordovician Biodiversification Event (GOBE) was a time of pronounced radiation within the Paleozoic and Modern evolutionary faunas. Despite increases in metazoan diversity during both Cambrian Ordovician, recent geochemical evidence suggests that Early may have experienced recurring deep ocean euxinia. dynamic connections between redox fossil-rich shelf environments remain unclear, but one way to elucidate these relationships is study rocks formed GOBE using long-term global short-term local proxies. Here we report results from Middle Juab Formation Kanosh at Fossil Mountain, Utah. has been interpreted by different workers either as an anoxic restricted basin or well-oxygenated normal marine based on sedimentological paleontological characteristics. employ sulfur isotopic composition carbonate associated sulfate (CAS) proxy for long-term, whole-ocean changes Ordovician. We use abundances organic carbon total proxies short-term, localized deposition Mountain sediments. Organic are low overall (average = 0.7 wt.%, maximum = 1.2 wt.% most conservative estimate), although some units had considerably higher content before burial. Total uniformly low, with average value 0.02 wt.% maximum 0.07 wt.%. abundance suggest anoxia not prevalent depositional environment Formations. Similarly, correlate well those reported time-equivalent strata Newfoundland, suggesting sediments were deposited basin. Even though data anoxic, our support hypothesis likely euxinic