Ocean Chemistry of the Past: Investigating Global and Local Redox Proxies during the Great Ordovician Biodiversification Event
Global and local redox proxies allow for the relationship between deep ocean redox and shallow shelf environments to be explored. The Great Ordovician Biodiversification Event (GOBE) was a time of radiation within the Paleozoic and Modern Fauna and provides an interesting starting point for research as recent studies suggest that the deep ocean was anoxic during the Ordovician (Thompson and Kah, 2012; Marenco et al., 2013). Analysis of sulfur isotope compositions of carbonate associated sulfate (CAS) provide a global signal for deep ocean redox, while concentrations of total sulfur and organic carbon give local signals in association with shallow marine environments. This relationship between the proxies allows the redox conditions of the deep ocean during the Ordovician to be compared to the conditions of the shallow marine environments which have abundant fossil evidence of biodiversification.
Here we propose to explore the relationship between deep-ocean and shallow marine environments during the early Ordovician through CAS, total sulfur, and organic carbon analysis of lower Ordovician rocks found in the Fillmore Formation of the Pogonip Group in Millard County, Utah, USA (C, G, and H Sections of Hintze and Davis, 2003). Samples will be collected at a 10 meter resolution with aid of a Jacob staff. During collection, biostratigraphy of the sections will also be recorded to provide a complete understanding of the depositional environments. Within the Fillmore Formation, there are also several sections of stromatolitic reefs which could act as another local proxy. Stromatolites are layered accretionary structures believed to be formed by microorganisms through binding of sediment. We hope to explore the possible geochemical signals recorded within stromatolites through analysis of total sulfur and abundance of organic carbon throughout the individual layers.