Master of Science (MS)


Geology and Geophysics

Document Type



Through a combination of vertebrate paleontology and geochemistry much can be discovered about the environments about the past. Fort Polk’s vertebrate fossil sites are important because they reflect a time when the Antarctic ice cap was just beginning to form during the middle Miocene cooling period just after the middle Miocene Climatic Optimum (~15Ma). This study tested the hypothesis that Miocene seasonality will be preserved in the isotopic geochemistry of terrestrial vertebrate remains at central North American Gulf Coastal sites. Geochemistry was used to understand fossil diagenesis, faunal communities and paleoenvironments. Fort Polk, LA sites range in age from 13.5 to 14Ma based on core data. Middle Miocene data taken from Fort Polk was compared to modern Fort Polk and middle Miocene Panama to show temporal and spatial variations in climate and environment. Sampling for δ13C and δ18O parallel to the growth axis along a tooth has provided data on dietary variation as well as seasonal variation. Bulk samples for δ13C and δ18O along the growth axis of a tooth provided time averaged data important for interpreting resource partitioning and paleoenvironments. Rare earth element (REE) analyses were used to assess the relative diagenetic alteration of specimens as well as provide insight into the environment of deposition. Isotopic samples were chosen based on the relative degree of diagenetic alteration determined from REEs. The isotopic information is significant for synthesizing terrestrial climatic and environmental changes in North America during the middle Miocene.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Schiebout, Judith