PHOSPHORUS SOURCES AND CYCLING DURING OCEANIC ANOXIC EVENT 3 IN THE WESTERN INTERIOR SEAWAY

Oceanic Anoxic Events (OAEs) represent major disturbances to the global carbon cycle, during which increased amounts of carbon are buried in deep ocean sediments. OAE3, unlike the “typical” Cretaceous OAEs, such as OAE2 that lasted ~500-900kr, represents a more prolonged period of carbon burial of around 3 million years during the Coniacian to Santonian (86- 83 Mya). This event has been extensively studied within the Western Interior Seaway (WIS), which was a large inland/epicontinental sea in the middle of North America that lasted throughout the Late Cretaceous (100 Mya) to early Paleocene (66 Mya). The sedimentary record of OAE3 in WIS is found in the Smoky Hill Chalk and Fort Hays Limestone members of the Niobrara Formation. The Niobrara Formation will be studied in two cores, the U.S. Geological Survey (USGS) Portland core and Amoco Rebecca K. Bounds core. These cores represent distal and proximal marine environments from the WIS, respectively. Previous work has suggested that stratification played a significant role in the development of anoxia. Detailed reconstructions of nutrient cycling during this period are limited and its possible role in primary productivity is unclear. Specifically, we aim to investigate whether volcanic activity OAE3 supplied P for increased biological productivity within the WIS during OAE3. We will present phosphorus speciation results from both sites to reconstruct P cycling in the WIS before, during and after OAE3. In addition, to determine the presence of ash in the sediments, Hg will be used as a volcanic ash proxy. Combined, these results will allow us to discern the role of volcanic ash as a nutrient source in the development and longevity of OAE3.