Browsing by Author "Snoeck, Christophe"
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Item Open Access Six centuries of adaptation to a challenging island environment: AMS 14C dating and stable isotopic analysis of pre-Columbian human remains from the Bahamian archipelago reveal dietary trends(Elsevier, 2021-01-29) Schulting, Rick J.; Snoeck, Christophe; Pouncett, John; Brock, Fiona; Bronk Ramsay, Christopher; Higham, Thomas; Devièse, Thibaut; Delancy, Kelly; Pateman, Michael; Keegan, William; Ostapkowicz, JoannaThe limestone islands of the Bahamian archipelago provide a challenging environment for human settlement, one that was not taken up until after AD 700. The analysis of human skeletal remains offers new insights into how this challenge was met. A substantial program of AMS 14C dating on pre-Columbian humans (n = 66) provides a robust chronological framework for the period ca. AD 1000–1600, with the latter date suggesting the possible persistence of an indigenous Lucayan presence on the islands for some decades later than previously thought. Associated stable carbon (δ13C) and nitrogen (δ15N) isotope analyses imply an early focus on near-shore marine resources that seems to have rapidly led to their local over-exploitation, resulting in a shift towards horticulture based mainly on root crops. The Medieval Warm Period is very likely to have been a factor in the initial settlement of the islands; the impact of the Little Ice Age is less clear, with no marked changes in either δ13C or δ15N. Strontium isotope results are consistent with an origin of most individuals within the archipelago, with a limited (but potentially important for maintaining connections) presence of incomers from the Greater Antilles, and perhaps even further afield. Despite the relatively short history of pre-Columbian occupation, Lucayan adaptations to the Bahamian archipelago were dynamic and demonstrate resilience in the face of both human resource depletion and climate change.Item Open Access Testing the effectiveness of protocols for removal of common conservation treatments for radiocarbon dating(University of Arizona / Cambridge University Press, 2017-08-09) Brock, Fiona; Dee, Michael; Hughes, Andrew; Snoeck, Christophe; Staff, Richard; Ramsey, Christopher B.To achieve a reliable radiocarbon date for an object, any contamination that may be of a different age must be removed prior to dating. Samples that have been conserved with treatments such as adhesives, varnishes or consolidants can pose a particular challenge to radiocarbon dating. At the Oxford Radiocarbon Accelerator Unit (ORAU), common examples of such substances encountered include shellac, the acrylic polymers Paraloid B-67 and B-72, and vinyl acetate-derived polymers (e.g. ‘PVA’). Here, a non-carbon containing absorbent substrate called Chromosorb® was deliberately contaminated with a range of varieties or brands of these conservation treatments, as well as two cellulose nitrate lacquers. A selection of chemical pretreatments was tested for their efficiency at removing them. While the varieties of shellac and Paraloid tested were completely removed with some treatments (water/methanol and acetone/methanol/chloroform sequential washes, respectively), no method was found that was capable of completely removing any of the vinyl acetate-derived materials or the cellulose nitrate lacquers. While Chromosorb is not an exact analogue of archaeological wood or bone, for example, this study suggests that it may be possible to remove aged shellac and Paraloid from archaeological specimens with standard organic-solvent-acid-base-acid pretreatments, but it may be significantly more difficult to remove vinyl acetate-derived polymers and cellulose nitrate lacquers sufficiently to provide reliable radiocarbon dates. The four categories of conservation treatment studied demonstrate characteristic FTIR spectra, while highlighting subtle chemical and molecular differences between different varieties of shellac, Paraloid and cellulose nitrate lacquers, and significant differences between the vinyl acetate derivatives.