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 δ³⁴S_collagen distribution in this region, contribute new ⁸⁷Sr/⁸⁶Sr_bone data to a currently small regional dataset, consider δ¹⁸O_bioapatite values on a more nuanced scale, determine which isotope systems best indicate particular regions, and especially consider the efficacy of δ³⁴S_collagen for geographic location. Random forest models show longitudinal trends in δ¹⁸O_bioapatite and ⁸⁷Sr/⁸⁶Sr_bone data; δ³⁴S_collagen values were more variable across Virginia with unique values in specific areas. Model results suggest δ¹⁸O_bioapatite values are most affected by geomorphic and meteorological controls, specifically altitude effects of the Appalachian Mountains, aridity, and mean annual temperature. The ⁸⁷Sr/⁸⁶Sr_bone 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 δ³⁴S_collagen values; the eastern Coastal Plains showed relatively high δ³⁴S_collagen 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 δ¹⁸O_bioapatite, ⁸⁷Sr/⁸⁶Sr_bone, and δ³⁴S_collagen data provides a more nuanced geographic prediction than one isotope system alone in this region. The δ³⁴S_collagen values in particular are emerging as a potential new proxy to indicate broad east–west movements of animals and people.