THE CHANGING ENVIRONMENT AND CLIMATE OF WESTERN LOUISIANA DURING THE MIDDLE MIOCENE

Fort Polk, Louisiana’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). Fork Polk presents a unique opportunity to study changes during the middle Miocene due to multiple sites that vary stratigraphically. Through a combination of vertebrate paleontology and geochemistry much can be discovered about the environments of Miocene Western Louisiana of the past. All sites are early Late Barstovian.

Paleoenvironments and faunal communities were studied by bulk sampling along the growth axis of fossil ungulate teeth for stable isotope analysis of δ13C and δ18O. Rare earth element analysis was also performed to determine the environment of deposition. Isotopic data agrees with palynological and rodent data from the various sites at Fort Polk.

Fort Polk, Louisiana sites range in age from 13.5 to 14Ma. Serial sampling for δ13C and δ18O parallel to the growth axis along a tooth has provided data on dietary variation as well as seasonal variation. 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. Observations reveal that middle Miocene Fort Polk shares more in common with modern Fort Polk rather than Panama from the middle Miocene.