Stable Isotope Analysis of Fossil Shark Teeth from the Late Cretaceous Western Interior Seaway

Session: (In-Person) Poster Presentation

The Western Interior Seaway was a Late Cretaceous (100.5-66 mya) inland sea that, at it’s largest, stretched north to south, from the modern-day Arctic Ocean to the Gulf of Mexico. Research concerning the seaway has revealed that there was likely a significant temperature gradient present, with cooler temperate waters to the north and warmer subtropical waters to the south. Using fossilized teeth from two species of sharks collected from an Arkansas site associated with the Western Interior Seaway, I seek to use carbon and oxygen isotopes to interpret the paleoecological conditions present in the southern province of the seaway during the Late Cretaceous. I also seek to identify what conditions made it suitable for these sharks to live in this province. Using stable isotope analysis by way of laser ablation, as well as conducting a literature review on relevant sources, I have found that these sharks likely preferred the subtropical temperatures over cooler temperate waters. Mirroring this is a similar pattern in salinity, wherein these species likely preferred water with a higher salinity than the more brackish water up north. This research is essential in understanding what conditions made the seaway favorable for shark species and how extinct marine vertebrates interacted with and reacted to their environment.