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The connection between living trees and Trinidad’s prehistory

17 July 2015 by Paula

A medium-sized specimen of Andira sp., growing in the forest reserves of Tamana, Eastern Trinidad. These trees can grow up to 100 feet in height.

Fig 1. A medium-sized specimen of Andira sp. growing in the forest reserves of Tamana, Eastern Trinidad. These trees can grow up to 100 feet in height.

Joanna Ostapkowicz, curator of the Americas collections for World Museum, reports from Trinidad, where she is working on a research project:

“The 4×4 rattled down the dirt road surrounded by the lush vegetation of Tamana, Eastern Trinidad, coming to a stop when forestry officer Harris Soukiel gave the word that one of ‘our’ trees had been sighted: Andira sp. (common name: Angelin).  We scrambled out of the truck to get our samples – two herbarium specimens, consisting of a small branchlet with leaves, fruit and/or flowers (one each for deposit at the National Herbarium of Trinidad and Tobago, and one for National Museums Liverpool) and a small wood sample – the main reason for my journey into Trinidad’s forests.  This piece of wood – essentially a twig about the length and thickness of a finger – was one piece in a complex puzzle, its ultimate aim to build understanding of Trinidad’s indigenous past. In its structure, it carried a strontium ‘signature’ – a key to helping chart where the pre-historic artefacts deposited in Trinidad’s Pitch Lake may have come from – or at least, where the wood selected to carve them may have grown.

Zoomorphic seat recovered from Pitch Lake, Trinidad, carved from Andira sp.

Zoomorphic seat recovered from Pitch Lake, Trinidad, carved from Andira sp.. Radiocarbon dated to AD 427-587. Length: 57cm; W: 27cm; H: 20cm (max.). Peabody Museum of Natural History, New Haven, US (Catalogue number ANT.145145).

During the course of their lives, trees take up their nutrients along with various other elements through the groundwater absorbed by their deep root systems. One of these elements is strontium.  It so happens that there are a number of different isotopes of strontium (versions of the element have the same chemical properties but slightly different atomic weights), and that the proportion of these differs slightly depending largely on the geology on which the trees grow.  While it is not actually needed by the tree, different forms of strontium (Sr) are incidentally incorporated into its structure during growth, dissolved in the water it absorbs.

This unique ‘signature’ is retained in the wood, remaining intact as long as the wood survives. Measuring its value can tell us where the tree grew, providing a provenance: the 10 carvings from Pitch Lake have their own unique signatures which can be compared to the strontium values of living trees, and so help clarify where they may have come from. Were the artefacts made locally at Pitch Lake, as is often assumed, or were they imported to Pitch Lake from other areas of Trinidad (or, indeed, the mainland)?  Building a dataset of strontium values for the island based on living trees will help us explore these questions. This is all part of a wider project entitled Black Pitch, carved histories: Prehistoric wood sculpture from Trinidad’s Pitch Lake, funded by the UK’s Arts and Humanities Research Council.

We first established what trees to concentrate on, based entirely on the woods used to carve the artefacts. Small wood samples taken from the carvings were sent to Dr. Alex Wiedenhoeft, of the USDA Forest Service for identification. The results included Andira sp. (Angelin), Terminalia dichotoma (Olivier), Brosimum sp. (Gatia or Moussara), Carapa sp. (Carapo) and Platymiscium sp. (Roble).  These were the trees that we were on the lookout for in our fieldwork.  And this is how my journey into Trinidad’s forests began, which would take me the length and breadth of the island.”

Processing herbarium samples

From left to right: Yasmin, Harris and Jameel processing herbarium samples

We will be finding out more about Joanna’s trip via a series of blogs over the coming weeks.

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