A GEOCHEMICAL INVESTIGATION OF REDOX DURING THE GOBE: SEARCHING FOR THE EFFECTS OF DEEP OCEAN EUXINIA ON SHALLOW MARINE ENVIRONMENTS USING CARBONATE ROCKS FROM THE WAH WAH AND JUAB FORMATIONS, UTAH

During the Great Ordovician Biodiversification Event (GOBE) there was a pronounced increase in diversity within the Paleozoic and Modern Evolutionary Faunas, particularly in continental shelf settings (e.g., Servais et al., 2009). Despite the pronounced increase in diversity during this event, recent geochemical studies suggest that deep ocean environments were characterized by euxinic conditions (e.g., Thompson & Kah 2012). However, the relationship between the GOBE and deep ocean euxinia remains unclear.

One way to investigate the relationship between euxinia in deep ocean environments and the GOBE is to explore redox proxies in carbonate rocks deposited in continental shelf settings. To this end, carbonate samples were collected at a 10 m resolution from the Lower to Middle Ordovician Wah Wah and Juab Formations in Millard County, Utah (J Section of Hintze and Davis, 2003). Total organic carbon and total sulfur abundances were measured as redox proxies using an ELTRA Carbon and Sulfur Determinator. Measured total sulfur and total organic carbon abundances were uniformly low. The average total organic carbon for all samples was 0.2 weight percent while total sulfur abundances averaged 0.01 weight percent. Samples from higher in the section yielded higher total organic carbon abundances (average = 0.9 weight %). These preliminary results suggest a lack of anoxia in these shallow marine environments. Ongoing study can further aid in understanding the relationship between the GOBE and deep ocean euxinia.