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Congratulations Dr. Alice Knaf!

Last week, Alice Knaf successfully defended her PhD dissertation 'Back to the Source. A combined trace elemental and multi-isotopic approach to provenance pre-colonial Caribbean jade artefacts'. Congratulations Dr. Knaf!

Back to the Source

To understand the full cultural significance of an archaeological object a comprehensive “material archive” is required. This archive should include information about the raw material(s) that make up an object, their sources and distribution histories, the technological context of object manufacture with respect to the on-going exchange of techniques and methods and their correlation with stylistic or iconographic aspects of the art object. In the Caribbean, lithic artefacts comprise a significant portion of precolonial site assemblages, including formal and expedient implements, and bodily ornaments. For their manufacture, the island communities employed a high diversity of lithologies, including amethyst, carnelian, rock crystal, diorite, jadeite jade, omphacite jade, nephrite jade, calcite, and turquoise. Their sources are heterogeneously distributed or even absent in the Caribbean archipelago suggesting extensive exchange networks between islands and the mainland. There is multiple evidence that in the Ceramic Age (500BC to AD1500) jadeite- and omphacite jade were frequently employed for celt production and complex incised artefacts, like beads, pendants and figurines. Within the Greater Caribbean, jade sources are only known in Guatemala (GM), eastern Cuba (CU) and the northern Dominican Republic (DR), establishing that jade items have been traded over vast distances.

To geochemically fingerprint objects stored in private and public institutions, very sensitive, ideally portable and non-invasive analytical techniques are demanded. This dissertation reports on the further optimization, validation and application of the 532 nm portable laser ablation sampling technique with subsequent low-blank geochemical analyses. The method allows minimally invasive in situ sampling of cultural heritage objects made of various materials, regardless of their mobility, geometry or size. The micro-invasive sampling is leaving cone to cylinder shaped ablation pits with the diameter of a human hair, invisible to the naked eye. Hence the integrity of the archaeological/art object is maintained. Subsequent low-blank geochemical clean lab procedures, trace elemental and strontium (Sr) and neodymium (Nd) analyses using quadrupole ICPMS, and thermal ionisation mass spectrometry (TIMS) produced accurate, precise and reproducible data.

The laser system was applied to collect material from 88 precolonial jadeite and omphacite jade celts and paraphernalia unearthed from Early to Late Ceramic Age (400 BC to AD 1500) sites in Cuba, the Dominican Republic, St. John, St. Thomas, St. Croix, St. Vincent and Grenada. An extensive geochemical jade source rock database (n=101) was created from the only know sources in the Caribbean, Guatemala, Cuba and the Dominican Republic. The geochemical fingerprints of the laser ablated artefacts were interpreted in reference to the jade source rock database using logistic multi-class regression models.

The predicted artefact provenances in Guatemala, Cuba and the Dominican Republic, led to the conclusion that Caribbean pre-colonial indigenous societies were linked with each other in a more complex manner than previously assumed. Vast trade and mobility networks spanning over > 4000 km, connecting Caribbean islands with the Mesoamerican and South American mainland, including linchpin settlements with highly specialised workshops serving as important distribution centres, stimulated and boosted the exchange and mobility of goods, humans, and ideas. This is the first holistic study that combines a comprehensive trace elemental and multi-isotopic database of known circum-Caribbean jadeite and omphacite jade source rocks in combination with geochemical fingerprints of Ceramic Age jade artefacts recovered from several Greater and Lesser Antilles Islands. The verification of widespread trading relations between precolonial groups in GM and Hispaniola, as well as on Lesser Antilles Islands is something that has not previously been determined. The impact of the projects’ results and conclusion for Caribbean archaeology is major, as it contributes to reconstruct the prehistory of the Caribbean.

Sourcing the dissertation

Dr. Knaf's dissertation consists of several published articles. These can be found via the following links: 

Knaf, A.C.S., Koornneef, J.M., Davies, G.R., 2017. “Non-invasive” portable laser ablation sampling of art and archaeological materials with subsequent Sr–Nd isotope analysis by TIMS using 10^13 Ω amplifiers. Journal of Analytical Atomic Spectrometry32(11), pp.2210-2216.

Knaf, A.C.S., Shafie, T., Koornneef, J.M., Hertwig, A., Cárdenas-Párraga, J., García-Casco, A., Harlow, G.E., Schertl, H.P., Maresch, W.V., Belando, A.L., Hofman, C.L., Brandes, U., Davies, G.R., 2021. Trace-elemental and multi-isotopic (Sr-Nd-Pb) discrimination of jade in the circum-Caribbean: Implications for pre-colonial inter-island exchange networksJournal of Archaeological Science135, p.105466.

Knaf, A.C.S., Guzzo Falci, C., Habiba, Toftgaard, C.J., Koornneef, J.M., van Gijn, A., Brandes, U., Hofman, C.L, Davies, G.R., accepted. A holistic provenance and microwear study of pre-colonial jade objects from the Virgin Islands: Unravelling mobility networks in the wider Caribbean. Journal of Archaeological Science: Reports. (link will follow soon!)

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