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Radiocarbon Dating Wooden Carvings and Skeletal Remains from Pitch Lake, Trinidad

Published online by Cambridge University Press:  31 October 2017

Fiona Brock*
Affiliation:
Cranfield Forensic Institute, Cranfield University, Defence Academy of the United Kingdom, Shrivenham, Oxon, SN6 8LA, United Kingdom
Joanna Ostapkowicz
Affiliation:
World Museum, National Museums Liverpool, William Brown Street, Liverpool, L3 8EN, United Kingdom School of Archaeology, University of Oxford, 36 Beaumont Street, Oxford, OX1 2PG, United Kingdom
Alex C Wiedenhoeft
Affiliation:
Center for Wood Anatomy Research, Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI, 53726USA
Ian D Bull
Affiliation:
Organic Geochemistry Unit, School of Chemistry, University of Bristol, Cantock’s Close, Bristol, BS8 1TS, United Kingdom
*
*Corresponding author. Email: [email protected].

Abstract

Since the mid-19th century, rare prehistoric wooden carvings and human skeletal remains have been dredged from Pitch Lake, Trinidad, during commercial asphalt mining. Establishing a chronology for these objects is challenging, due to both a lack of stratigraphic and contextual information and the necessity to completely remove any pitch to ensure accurate radiocarbon (14C) dates. A range of solvent extraction protocols was tested to identify the most suitable one for pretreating the Pitch Lake artifacts, and then applied to ten wooden objects and a human cranium recovered from the lake. Several of these objects yielded earlier dates than expected, raising concerns that pitch had remained after pretreatment and had affected the dates. Pyrolysis-GC/MS and optical microscopy techniques were applied to material from the human cranium, a weaving tool, and a small bowl. These techniques, as well as routinely applied laboratory quality assurance procedures, indicated that there was no residual pitch within the cranium or the weaving tool after pretreatment, giving confidence to the dates. However, the small bowl was observed to still be contaminated with pitch after extensive pretreatment, indicating that the date is too old and can only be considered as a terminus post quem.

Type
Method Development
Copyright
© 2017 by the Arizona Board of Regents on behalf of the University of Arizona 

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Footnotes

Selected Papers from the 8th Radiocarbon & Archaeology Symposium, Edinburgh, UK, 27 June–1 July 2016

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