HOW SEDIMENT MIXING AND TRANSPORT INFLUENCES RECORDED CARBON ISOTOPIC TRENDS: PERMIAN REEF TRAIL, GUADALUPE MOUNTAINS NATIONAL PARK

Carbon isotope geochemistry is a method commonly deployed to help correlate stratigraphic units and to document changes to the global carbon cycle. These applications are based on the assumption that the carbon isotopic value recorded in carbonate sediments reflects the carbon isotopic value of the water at the time of deposition. However, there are possible scenarios where this assumption is not met. For example, allochthonous intraclasts as well as mixing of clasts during deposition could cause recorded values to depart from carbon isotopic values of the water during deposition. In this study we aimed to explore how sediment mixing and transport of clasts influenced carbon isotopic trends by focusing on the Late Permian Yates Formation, Tansil Formation and McKittrick Limestone Member of the Bell Canyon Formation exposed along the Permian Reef Trail in the Guadalupe Mountains National Park. We generated three carbon isotopic records, one for the shallow water shelf crest, one for the slope, and one for the basinal setting. By slabbing samples from the slope, we were able to target and generate carbon isotopic values of various clast types (e.g. intraclasts, transported fossils, micrite). We compared the slope carbon isotopic record to the other settings where mixing and transportation is predicted to be less. From these results, it is clear that transportation and mixing of clasts does impact the generated carbon isotopic trends. This study highlights the importance of choosing what is drilled for carbon isotopic values with care.