USING TOOTH WEAR AND DECOMPOSITION TO INTERPRET GEOCHEMISTRY IN PALEONTOLOGICAL LOCALITIES

Vertebrate fossil localities inform interpretations of paleobiology, including soft tissue decomposition and bone preservation. The Pig Wallow Site (Pig Dig, Badlands National Park) represents an ancient watering hole and preserves the remains of at least 16 individual Orellan taxa (33.8-32.4 Mya). The site consists of a green bone-bearing mudstone unit, with the green coloration of the bone-bearing layer attributed to anaerobic decomposition of animals at the site. Measures of individual animal ages (age reports), using comparative tooth wear analysis previously conducted on Archaeotherium and Subhyracodon specimens from the site indicate species-specific population differences. The latter group is represented by adults while the former is represented by mixed age groups. However, without age reports for all multi-individual taxa (n=5), the paleoecology, population dynamics, and likely nutrient load during decomposition at the site are unclear. To that end, age reports from three additional taxa will be used to constrain population dynamics, which can then be used to estimate the total mass of organic material (tissues) that decomposed in this watering hole system. Estimates of nutrients (carbon and nitrogen) released from decomposition can then be used to infer the resulting geochemical impact on the site. X-ray fluorescence (XRF) analyses were conducted on bones, teeth, and rocks from the site, and results from these XRF analyses will be used to complement the qualitative tooth wear analyses to better inform the decomposition processes and resulting site geochemistry facilitating bone preservation. This type of approach, combining qualitative measures of populations and quantitative measures of bone geochemistry may be useful at other localities where the collecting site is no longer known, or to provide a new perspective that integrates observations from modern (bio)geochemical processes towards the interpretation of fossil site formation history.