A paleoenvironmental reconstruction of the Elands Bay area using carbon and nitrogen isotopes in tortoise bone
Master Thesis
2017
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University of Cape Town
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Abstract
This study explores the utility of stable light isotopes in Chersina angulata (angulate or bowsprit tortoise) bone collagen as a paleoenvironmental proxy, to augment the limited range of proxies preserved in Southern Africa. δ¹³C and δ¹⁵N were measured in 76 archaeological tortoises from Elands Bay Cave and nearby Tortoise Cave. The samples range in age from the late Holocene to the terminal Pleistocene. δ¹⁵N values are not strongly correlated with δ¹³C, indicating different drivers of variation in the two isotopes. δ¹³C and δ¹⁵N values are lower between 154-487 cal. BP, which spans the Little Ice Age, compared with 744-1 042 cal. BP, which is the period of the Medieval Climate Anomaly (MCA). This implies that conditions were cool and wet during the LIA, and hot and dry during the early MCA. δ¹³C and δ¹⁵N values were higher during the early stages of the MCA (744-1 042 cal. BP), indicating drier conditions than in the late MCA (547-669 cal. BP). In the period prior to the MCA (1180-1357 cal. BP), lower δ¹³C and δ¹⁵N values indicate cooler, moister conditions. Higher δ13C values also indicate a temperature increase at the beginning of the Middle Holocene (4005-5 720 cal. BP). These findings are generally consistent with existing paleoenvironmental records from the Cederberg and Elands Bay region. The paleoenvironmental record generated from the tortoise carapace and plastron bone provides the first evidence from the terrestrial archaeological record for the LIA and MCA at Elands Bay. Hence, the tortoise record is able to provide a more detailed climate record than the charcoal and faunal record at EBC. This study shows that the analysis of stable isotopes in C. angulata from archaeological sites is a viable option for paleoenvironmental reconstruction.
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Naidoo, N. 2017. A paleoenvironmental reconstruction of the Elands Bay area using carbon and nitrogen isotopes in tortoise bone. University of Cape Town.