EXCAVATING LATE PLEISTOCENE MASTODONS FROM FLOODED SITES IN THE NORTHEAST

Integrated multidisciplinary analyses of flooded mastodon sites in the Northeast are providing the kinds of details needed to better understand the paleoecology of this animal and other extinct megafauna. Subphreatic or otherwise flooded sites containing bones in a matrix of fine anoxic sediments with approximately neutral pH can preserve bones and other biomineralized materials while also providing a well-preserved palynological and plant macrofossil record. The methodological challenge is to recover these underwater materials with good vertical and horizontal stratigraphic control. This has been accomplished in an array of megafaunal sites by placing a shallow well in the excavation pit and pumping at the optimum rate for maintaining a temporary cone of depression in the water table that allows subaerial excavation. Careful attention to site hydrology, combined with a large-scale version of the three-dimensional recording techniques of archaeology adapted to wet substrates, allows the excavator to maintain vertical provenance to centimeter-scale resolution. The depressed water table itself can be used as a leveling device. The technique has been demonstrated to work in a wide variety of circumstances throughout the world. In upstate New York, the investigators have used the method successfully to reinvestigate the 19^th-century mastodon excavations at Otisville, as well as such new sites as the Hyde Park mastodon and the Pawelski Cervalces site. The rich paleoecological and geochronological results can then be integrated across the region to aid in the reconstruction of habitats, distribution, and behavior. This work has allowed the evaluation of proposed causes for the end-Pleistocene extinctions by comparing the results with the predictions generated by various hypotheses concerning rates, patterns, and inferred processes of extinction.