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UBC Theses and Dissertations

The toolstone formerly known as green andesite : a geochemical characterization of fine-grained lithic materials from the Burrard Inlet area, Vancouver, B.C. Canada Thomas, Karen Rose


Archaeologists often attempt to identify rock type in the field and laboratory based on generalized visual characteristics. This approach has a great potential to produce incorrect categorizations that would detrimentally impact sourcing studies. This thesis research explores a green toolstone found in the archaeological assemblages of the Burrard Inlet region and surrounding area of North Vancouver, on the southern coast of British Columbia. Previously, this toolstone was called green andesite based solely on visual identification, and the designation has been reproduced in the literature and a handful of circular citations. The goal of this research was to use several geochemical methods, including wavelength dispersive X-ray fluorescence (WD-XRF) and portable energy dispersive X-ray fluorescence (ED-XRF), to answer the question “Is the toolstone known as green andesite actually andesite?” The secondary goal of this project was to compare the toolstone data to publicly available geologic data from the nearby Indian River watershed to see if any locations could be eliminated as geological origins for the toolstone. The general conclusions of this research are that, based on major element concentrations, the material known as green andesite is not actually andesitic. However, if this research looked at trace element concentrations alone, green andesite dykes of the Indian River Valley could not be excluded. Taking time to establish rock type with standard geological and geochemical techniques before attempting to eliminate potential source affinities using only trace elements is an important step often overlooked in archaeological sourcing studies. The material formerly known as green andesite has been incorrectly labeled, and archaeological reports, collections, and catalogues have been reproducing this miscategorization. Through this research, I identified a possible rock type for the toolstone known as green andesite and using the provenience hypothesis (Wilson and Pollard 2001) I identified several geological contexts within the Indian River watershed that cannot be excluded as possible places of origin.

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