GEOCHEMISTRY OF FOSSIL SHARK TEETH AS AGE PROXIES FOR NEOGENE SITES OF FLORIDA

Florida produces some of the most significant paleontological discoveries of the Neogene, a time period marked by changes in vegetation, global climate change, and sea level fluctuations. It also includes many mixed marginal marine and terrestrial sites that allow the integration fo multiple dating techniques. Nevertheless, the ability to apply precise dating techniques to resolve age at relevant sites is complicated due to the lack of appropriate rock used with traditional geochronological methods.

To address this issue, strontium isotope stratigraphy (SIS) is applied using shark tooth enameloid to further resolve age at two latest Hemphillian (Hh4– 5.7 to 4.75 Myr) sites lacking calcium carbonate materials typically used with this method. Fossil shark teeth were tested from both sites producing results (5.67 Ma and 5.13 Ma) that aligned with previously known biochronological data, thus advancing our understanding of age differences between the sites by 500,000 years.

Additional testing to better understand potential taphonomic reworking used rare earth elements (REEs) to discern pattern similarities and differences among marine and terrestrial taxa. These same tests present further evidence of distinct temporal and spatial variation between the Hh4 sites, helping to further elucidate differences in their ecology and biodiversity.

These findings were ground truthed using two additional Florida localities containing both calcium carbonate and shark teeth to compare strontium ratios between them. Though results closely aligned with expected NALMA ages, age correlations between shell and teeth were surprisingly different from one another. Despite the need for further testing to understand these variances, results suggest that shark tooth SIS chemistry is a promising age proxy for localities with similar lithology.