Testing various pre-treatments on artificially waterlogged and pitch-contaminated wood for strontium isotope analyses

Strontium isotope ratios (87Sr/86Sr) are commonly used in archeological and forensic studies to assess if humans and fauna are local to the place they were found or not. This approach is largely unexplored for wooden artifacts recovered in archeological contexts, as wood – in the rare instances it does survive – is often poorly preserved. One of the most common ways wood is preserved is through the anoxic conditions found in waterlogged contexts. A more unusual form of preservation is through submergence in natural pitch. These depositional media contribute their own strontium values to the in vivo 87Sr/86Sr wood values, which needs to be removed prior to analysis. Here we test several pre-treatment methods to remove potential strontium contamination from wood samples that were artificially immersed in seawater and pitch from Trinidad’s Pitch Lake. Water rinses and acid-leaching tests were carried out with hydrochloric acid and acetic acid to remove exogenous strontium from experimentally waterlogged wood. These tests removed large amounts of strontium from the samples and did not enable the recovery of the endogenous 87Sr/86Sr signal. For samples artificially immersed in pitch, the pre-treatments tested were based on radiocarbon dating procedures and carried out with and without the aqueous-based acid-base-acid (ABA) step. The use of organic solvents alone (methanol and toluene) removed exogenous strontium originating from the pitch. However, the ABA step eliminates large amounts of in vivo strontium from the samples. These tests show that 87Sr/86Sr values of wood are altered by the presence of pitch and water. With adequate pre-treatment using exclusively organic solvents, it may be possible to remove this contamination for samples immersed in pitch. However, the aqueous-based ABA pre-treatment should be avoided. The removal of contamination from waterlogged samples was unsuccessful with the current pre-treatment protocols and more research is needed. More importantly, and unexpectedly, 87Sr/86Sr values may extend outside of the mixing line between the wood’s endogenous strontium and the water. These results indicate the need for extreme caution when attempting to determine the provenance of waterlogged wood

Dark materials: Pre-Columbian black lithic carvings from St Vincent and the wider Caribbean

A small number of pre-Columbian black lithic carvings have been found at archaeological sites across the Caribbean, as well as in parts of neighbouring mainland South America. The identity of the material used to create these artefacts is often unknown, but suggestions include lignite, wood, petrified wood, manja(c)k, jet (or ‘jet-like’ materials) and hardened asphalt. These identifications are often historical and lacking any scientific basis, and as such can be unreliable. However, identification of the material has the potential to inform on the source of the carving and thereby pre-Columbian trade routes within the circum-Caribbean region. Four analytical techniques (reflectance microscopy, FTIR, Py-GC/MS, x-ray fluorescence) were applied to samples taken from two carvings found on St Vincent and five comparative materials. Both artefacts were found to be most likely carved from cannel coal, indicating that they originated in South America (where cannel coal is found extensively in locations in Colombia and Venezuela), as the material is not found within the Caribbean region

“For there is no rock”: Lucayan stone celts from the Bahamas and Turks and Caicos islands

This paper presents the first systematic study of pre-Columbian imported stone celts recovered from the limestone islands of the Lucayan archipelago, comprising The Bahamas and the Turks and Caicos Islands of the northern Caribbean/West Atlantic. The majority derive from antiquarian collections and early archaeological investigations, prior to the destruction of many sites due to guano mining and development; only a handful have been recovered during archaeological investigations since the 1960s. The corpus includes 224 celts, of which 162 are complete and provide the measurements for a comparison with width/length ratios of celts from the proximate source islands of Cuba and Hispaniola. While the Lucayan archipelago shows a slightly higher proportion of wider celts, consistent with more reworking, overall the corpus suggests that exchange networks were sufficient to meet demand. This conclusion is supported by the absence of any clear diminution in size with distance from sources. The majority of stone celts (71.9 %) have been identified as various forms of “jade,” supplemented with a range of other materials. Despite the higher value often attributed to jade cross-culturally, we find no clear evidence for its differential treatment, though the archipelago's northern islands do have a lower proportion of jade versus non-jade celts. “For there is no rock”: Lucayan stone celts from The Bahamas and Turks and Caicos Islands. “…the occasional discovery of beautifully polished stone implements proves that [the Lucayans] were in communication with distant lands, for there is no rock, except soft coral limestone, anywhere in the archipelago.

Paired Dating of Pith and Outer Edge (Terminus) Samples from Pre-Hispanic Caribbean Wooden Sculptures

Radiocarbon dating of historical and archaeological wood can be complicated, sometimes involving issues of “inbuilt” age in slow-growing woods, and/or the possibility of reuse or long delays between felling and use of the wood. Terminus dates can be provided by dating the sapwood, or the outermost edge of heartwood, while a date from the pith can give an indication of the first years of growth. A sequence of samples from specific points within the bole can be used to determine the growth rate of the tree. Such a combined dating strategy is particularly useful in cross-referencing dates from a single piece, better placing it in its chronological context. This paper reports paired or multiple dates from 11 wooden sculptures dated as part of the Pre-Hispanic Caribbean Sculptural Arts in Wood project, which studied 66 wooden artifacts attributed to the pre-colonial Taíno, the indigenous peoples of the Caribbean’s Greater Antilles. The calibrated ages of the pieces published here range from ~AD 700–1500, indicating that the Taíno were producing elaborate sculptures much earlier than previously thought. The paired or multiple dates from these carvings confirmed the accuracy of the results, and were also used to construct a growth rate model of what was expected to be a slow-growing species (Guaiacum sp.). This model demonstrates that the boles used to create the sculptures grew on average 1 cm every 6–13 yr.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Chronologies in wood and resin: AMS 14C dating of pre-Hispanic Caribbean wood sculpture

This paper establishes a chronological framework for selected pieces of Caribbean wooden sculpture, enabling previously ahistoric artefacts to fit back into the wider corpus of pre-colonial material culture. Seventy-two 14C AMS determinations from 57 artefacts held in museum collections are reported, including 32 ceremonial duhos, or seats. Far from being constrained to the last few centuries prior to contact, the dates for these objects extend back to ca. AD 250, and include the artistic legacies of various cultures. Duhos in both low and high back styles are present from about AD 600, if not earlier, in a distribution that spans the Antillean island chain from Trinidad to Cuba. Complex, drug-related paraphernalia and elaborate ancestral reliquaries are in evidence by AD 1000, as are some distinctive regional styles – such as the unique iconography from the Bahamas and Turks and Caicos islands. This paper explores relevant methodological issues – from the challenges of working with museum pieces (e.g., uncertain provenance, discrete sampling techniques, impact of previous conservation treatments on dating results), to dealing with potential ‘in-built’ age in tropical hardwoods