Carbon Cycle Trends Recorded By Organic Carbon Stable Isotopes In Paleocene Strata, Benton County, Mississippi: Implications For Chronostratigraphy Of The Porters Creek And Naheola Formations
The paleocene-eocene thermal maximum (petm) is one of the most studied carbon isotope excursions in earth\u27s history. The petm occurred 55 million years ago when excess isotopically heavy carbon (c13) was added into earth\u27s carbon cycle, resulting in ecological and environmental changes. The petm is marked by a negative stable carbon isotope excursion (cie) in marine and continental strata around the globe. The paleocene and eocene boundary is contained in the sedimentary fill of the Mississippi embayment so there is high potential to produce new petm stable isotope datasets. The purpose of this project is to analyze the boundary for evidence of the petm and other cies at the flat rock church paleobotanical site and a nearby core from Benton County, Mississippi. Fieldwork at the flat rock church site was conducted in order to observe the stratigraphic and lateral relationships of the paleocene porters creek formation and naheola formation and the eocene meridian sand and to collect samples for preliminary stable carbon isotope analysis. Continuous, high-resolution data were produced from samples from the rollison core, which were decarbonated and analyzed for stable organic carbon isotopes (î”13ctoc), percentage of carbonate, and total organic carbon. The resulting î”13ctoc curve shows an overall increase in î”13ctoc values upsection with five superimposed high-magnitude positive cies. Two of the five are discounted as the result of procedural error and the remaining three are interpreted as representing a combination of increased organic carbon burial and Caribbean volcanism. The upsection trend in î”13ctoc enrichment likely correlates to a segment of a larger, global paleocene trend known as the paleocene carbon isotope maximum. Correlation of the î”13ctoc curves allows the establishment of a more precise chronostratigraphy, revising the previously established depositional range of the porters creek and naheola from 63.8-56 ma to 60.5-56.6 ma
