Little Ice Age drought event reconstructed from isotopic analysis of archaeological springbok (Antidorcas marsupialis) teeth

Abstract

In this paper, we use δ13C and δ15N of serial samples of dentine collagen from archaeological springbok teeth as a novel high-resolution but short-term palaeoenvironmental proxy. Two adult and seven juvenile springbok (Antidorcas marsupialis) teeth from the archaeological site SK400 were analyzed. This site, located in the Namaqualand desert on the west coast of South Africa has yielded a large number of small-medium bovids, likely all springbok. These springbok were killed in a single episode between 1438 and 1641CE, during the Little Ice Age (LIA). The juvenile springbok were significantly more depleted in 13C and enriched in 15N compared with the adults. During the four to six months over which their teeth developed, the juveniles consumed a higher proportion of C3 plants and were exposed to greater aridity than the adults at equivalent ages. Based on dental wear, the adults are estimated to be between 3.5 and 7.5years old at death, so the isotope values in their teeth record diet and environmental conditions several years earlier. In addition, the juveniles (but not the adults) show a trend towards more negative δ13C values and very high δ15N (up to +18.9‰) during the period of tooth formation, truncated by the animals' death. We infer that the animals were killed during an extreme drought. Informed by the archaeological evidence, we surmise that this was probably a herd of springbok on ‘trek’ in search of food and water, as this species is known to do during droughts. Although palaeoenvironmental proxies for the region as a whole suggest that Namaqualand was cool and wet during the Little Ice Age, this study indicates at least one period of drought, contributing to the developing picture of highly variable climates in southern Africa during the Holocene.