1. via Stable Isotopes of Fossil Turtles and Fish
Testing Paleoenvironmental Models of the Cretaceous Western Interior Seaway
via Stable Isotopes of Fossil Turtles and Fish
Matthew J. Kohn; University of South Carolina and Boise State University
Past ocean circulation patterns are key for understanding how fossil fuel resources are distributed and preserved. Yet one major source of fossil fuels, the Cretaceous Western Interior Seaway (c. 100 million years old), is as yet poorly characterized with respect to these circulation patterns. To better constrain effects of evaporation and freshwater input, we have calibrated a novel isotopic method, oxygen isotopes in turtle bone phosphate, that can be used in concert with isotope compositions of fossil fish.
Our main results from modern marine turtles shows trends completely commensurate with studies of freshwater turtles. In particular, we readily resolve differences in isotope composition of seawater resulting from relatively small degrees of evaporation (e.g. Cayman) and freshwater input (NC-SC) These results now allow us to determine water compositions from fossil turtles with a high degree of confidence.
Additionally, we have found that oxygen isotope compositions of turtle bone are invariant from bone to bone, indicating effective thermoregulation within their flippers. This result broadens application to multiple fossil elements for paleoceanographic work.