HOW EROSION EFFECTS CARBON ISOTOPIC TRENDS: THE LATE PERMIAN MCKITTRICK LIMESTONE

Carbon isotopic trends are an essential tool for understanding changes in the global carbon cycle over time and correlating rock units (chemostratigraphy). These applications assume that documented trends are primary and reflect an accurate record of changes through time. However, diagenetic processes and erosion can invalidate this assumption. In this project, we focus on the impact of relatively small-scale (<1 meter) erosion on documented carbon isotopic trends. To accomplish this, we targeted the Late Permian McKittrick Limestone of the Bell Canyon Formation in Guadalupe Mountains National Park. This location is ideal for our study because the outcrop is continuous from crest to slope to basin and previous work allows us to correlate from shallow to deep water environments. We identified a small slump or paleochannel in the McKittrick Limestone that forms the basis of this study. By measuring and collecting samples from two sections within the outcrop, we were able to document how erosion impacted the signal. We have also compared our results to the corresponding rocks in the shallow water of the shelf crest to test for any cryptic erosional events that might have impacted the McKittrick Limestone carbon isotopic record at this location.