The biogeochemistry and paleoecology of late Pleistocene proboscideans from the southern United States

Measurements of the biogeochemistry of mammoths and mastodons were used to reconstruct several aspects of their paleoecology and to examine possible causes of their extinction. Analyses of strontium isotope ratios were used to reconstruct migration patterns. Carbon isotope ratios were used to reconstruct diets. Finally, oxygen isotope ratios were used to examine climatic variability.; Although analysis of the 87Sr/86Sr ratio of fossils can be used to reconstruct habitats and movement patterns, diagenetic contaminants often complicate such reconstructions. Thus, the first study in this work tested the effectiveness of pretreatment methods currently used to remove diagenetic Sr from fossils. It was determined that most (≥95%), if not all, diagenetic Sr can be removed from tooth enamel, but even after treatment bones frequently retain a large percentage (≥50%) of diagenetic Sr.; The remaining studies used biogeochemical analyses of tooth enamel to examine the paleoecology of late Pleistocene mammoths and mastodons. Analysis of animals from Florida revealed that mastodons were primarily browsers that migrated north toward the Appalachian Mountains of Georgia for distances of at least 150 km, but not more than 700 km. Mammoths were primarily grazers that restricted their movements to the coastal plain. The carbon isotope ratios of mastodons did not change significantly between full and late glacial times, suggesting that dietary stress did not contribute to their extinction.; Mammoths from the Great Plains region were also primarily grazers. Mammoths from Texas and New Mexico displayed biogeochemical patterns that differed from those of Colorado mammoths, suggesting that each population was distinct (i.e., mammoths did not migrate between the two regions, a distance equal to ∼600 km). However, mammoths from eastern New Mexico appear to have migrated into the Rocky Mountains, a distance equal to ∼200 km. Finally, the taphonomic settings of mammoth assemblages at several Clovis butcher sites was assessed. It was determined that each Clovis site represented assemblages of unrelated mammoths, suggesting that Paleoindian hunters did not pursue and kill entire mammoth family groups.