When Elephants and Rhinos Roamed Louisiana: Hunting Miocene Fossils on Fort Polk

Article excerpt

It was a great pleasure to have presented the following talk to Phi Kappa Phi Centennial celebrants. The speakers said many wonderful things about the Phi Kappa Phi Fellowships. I will merely reiterate that honors to students for excellence and scholarship are wonderful, but Phi Kappa Phi also gives real resources - money, in other words, which is how our society measures value - to these young people when they need it most in their education, and this is a great encouragement.

Ph.D. research is said to be like digging up old bones and transferring them from one graveyard to another. If you are a vertebrate paleontologist, you have to find real bones, clean them, and study them, and this is a long process. I have worked on Gulf Coast animals of the period from the beginning to the middle of the Age of Mammals (roughly 65 to 11 million years ago), since 1970, based at Louisiana State University since 1976, and have a special interest in paleogeographic and paleoecological differences between northern and southern faunas of ancient animals. I will focus heavily on my research on Miocene terrestrial mammals from western Louisiana in the following discussion, because the sites in that region are the only ones in the state that have yielded large vertebrate faunas older than the Pleistocene (the Ice Ages).

Fossil-hunting in Louisiana is difficult because dense vegetation prevents much outcrop area from being available, but Louisiana still has wonderful fossil sites. I have focused my research on Fort Polk and its Miocene-age sites since 1993. To get oriented to the geology of Louisiana, remember that Louisiana did not always exist. After North and South America broke apart and the Gulf began to form, sediments built out from the southern edge of North America into the Gulf. Bands of younger and younger rocks parallel the Gulf shore as one travels from north to south in the state, and all of Louisiana is relatively young. No dinosaurs ever roamed the state, a fact that disappoints many people. Eocene-age beds, from early in the Age of Mammals, outcrop in the north-central part of the state, and these have yielded some spectacular fossil whales. A band of Miocene-era rocks, yielding fossils from the middle of the Age of Mammals, stretches across the midsection of the state, crossing Fort Polk. Research on Miocene paleontology in western Louisiana began in 1993 when staff members of the Fort Polk Environmental Office contacted Louisiana State University about a fossil found in a newly bulldozed area. It was a partial jaw of a three-toed horse, a fossil find that indicated a Miocene age. In the intervening years, some of the staff in the Environmental Office have become wonderful fossil finders. Figure 1 shows James Grafton indicating a 1997 find, a partial three-toed horse upper jaw.

My research focuses on teeth [ILLUSTRATION FOR FIGURE 2 OMITTED], because they are the hardest, most resistant part of the vertebrate skeleton, most likely to survive weathering, reworking, burial, and processing to recover fossils. They also reveal how the animal processed its food, which tells us something about both the animal and its environment. Remains of small mammals, especially their tiny teeth, rare at most Miocene sites, are the main focus of research in the Louisiana Miocene. They are recovered from scattered layers of conglomerate rock rich in soil-formed nodules. These rocks formed during periods when material eroded from the Miocene soils washed into low areas. This material was cemented after burial to form lenses or layers of hard rock rich in material winnowed from ancient soils, including the teeth and bones of animals.

The resulting rock, which requires a fortunate combination of soil types, erosion, burial, and cementation to form, is a treasure trove of fossils, especially teeth of small mammals. This rock can be located even in small gullies and overgrown areas because it is harder than surrounding mudstone and forms ledges [ILLUSTRATION FOR FIGURE 3 OMITTED]. …