Abrupt Terminations and stone artefact reduction potential
Citation: O.J. Macgregor (2005) Abrupt Terminations and stone artefact reduction potential. In Clarkson, C. and L. Lamb (Eds) 2005 Lithics ‘Down Under’: Australian Approaches to Lithic Reduction, Use and Classification. British Archaeological Reports International Monograph Series S1408. Oxford: Archaeopress. (RSS)
What reduction methods help to preserve raw material? What might one look for in the archaeological record to suggest an effort to preserve raw material? In particular, what role do abruptly terminated flake scars play in all of this? If abruptly terminated flake scars are detrimental to an ability to reduce a core, what strategies might be implemented to overcome this? In order to investigate these questions, Macgregor decided to perform experiments aimed at an effort to see what it takes to overcome the flake scar issue.
Macgregor dropped ball bearings onto glass cores that had varying artificial termination scars carved into them in order to determine the effect that platform angles and platform thickness have on overcoming the flake scar issue. He controlled for all other variables. He used eight different categories of cores in order to perform his analysis. Four of the cores had exterior platform angles of 70 degrees, while the other four had angles of 45 degrees. Within each angle category, the cores were divided into categories based on the type of abruptly terminated flake scar that was carved into them. The first category consisted of cores without a flake scar. The second category had a scar 5mm deep and 20mm long. The third category had a scar 10mm deep and 20mm long. The fourth category had a scar 5mm deep and 40mm long. The platform thickness varied from a little over 2mm to almost 14mm.
Macgregor determined two important thresholds, which he defines as the “detachment threshold” and the “scar threshold”. The detachment threshold is defined as the point when the platform became too thick to be able to remove a flake with the force used. The scar threshold is defined as the point at which the platform is thick enough to allow a fracture that fully removed the scar. The range of platform thicknesses between the two thresholds is the important factor as it determines how difficult it is to overcome the issue of the scar. Macgregor found that the range of platform thicknesses was greater for the 45 degree cores. Also, while lengthening the scar on the 70 degree cores significantly reduces the region between the two thresholds, doing so on the 45 degree cores does not decrease the range. He thus concludes that the higher the exterior platform angle, the more issues one would have with abruptly terminated flake scars.
Theoretical and practical relevance:
This article is relevant to theories that relate changes in artifact types to changes in the costs associated with the material used for stone artifacts. It relates what one might look for in the archaeological record to suggest such high costs.
While Magregor’s experiment is quite convincing in its assertion that higher exterior platform angles are more problematic for trying to recover a core from a flake scar, I am not sure that he fully connects this contention to what one might find in the archaeological record. I was a little confused about whether edge angles were the same thing as exterior platform angles, making some of Magregor’s discussion at the end difficult to associate with his experiments. When he spoke of using multiple platforms to overcome the issue of flake scars it seemed unrelated to his experiments and therefore a little distracting. While his points in the discussion at the end may be true, I would have preferred if he had focused more on the direct implications of his own particular experiment and its outcomes. That being said, I do believe that the experiments Macgregor conducted and their results are an important contribution to the understanding of reduction processes and their connection to the cost of raw materials.