Oxygen, strontium, and sulfur isotopes in modern deer bone from Virginia, USA: a model for geographic location in east coast North America

Understanding movements of animals and people in modern or historic contexts is hindered by limited animal tissue proxies to indicate regional origins. On North America’s east coast, stable oxygen and hydrogen isoscapes provide broad latitudinal proxies, but more nuanced geographical proxies are lacking. This study examines oxygen, strontium, and sulfur isotopes in deer bone bioapatite and collagen from Virginia, USA, which reflects grazing location, to create the first robust δ34Scollagen distribution in this region, contribute new 87Sr/86Srbone data to a currently small regional dataset, consider δ18Obioapatite values on a more nuanced scale, determine which isotope systems best indicate particular regions, and especially consider the efficacy of δ34Scollagen for geographic location. Random forest models show longitudinal trends in δ18Obioapatite and 87Sr/86Srbone data; δ34Scollagen values were more variable across Virginia with unique values in specific areas. Model results suggest δ18Obioapatite values are most affected by geomorphic and meteorological controls, specifically altitude effects of the Appalachian Mountains, aridity, and mean annual temperature. The 87Sr/86Srbone ratios are controlled largely by underlying bedrock geology, allochthonous dust and sea spray deposition, and surface source mixing. The western coal-bearing formations of the Appalachian Plateau showed relatively low δ34Scollagen values; the eastern Coastal Plains showed relatively high δ34Scollagen resulting from dust and sea spray deposition. Modeled proxies for modern anthropogenic inputs of these elements (e.g. fossil fuels) notably were not strong controlling factors for these isotope systems; therefore, the models produced here are suitable for identification of geographic location using bone isotope values from modern, historic, or paleontological samples. Linear discriminant analysis suggests A multi-isotope approach using δ18Obioapatite, 87Sr/86Srbone, and δ34Scollagen data provides a more nuanced geographic prediction than one isotope system alone in this region. The δ34Scollagen values in particular are emerging as a potential new proxy to indicate broad east–west movements of animals and people.