Judges’ Queries and Presenter’s Replies

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Presentation Discussion

  • May 22, 2012 | 05:06 p.m.

    Very interesting presentation and poster. It is definitely not my field but you did a good job with your explanation.

    I guess the question I had is the following. What is the motivation to distinguish origins of the ochre pigments from the three or four sites that you chose? And I am still not sure how much sensitivity was achieved in determining differences between these three sites. Finally, how much more different if you were to obtain ochre from more distant sites, for example, outside the Karonga region?

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Icon for: Andrew Zipkin

ANDREW ZIPKIN

George Washington University
Years in Grad School: 3

Three Geochemical Approaches to Ochre Pigment Provenance in northern Malawi

J. Desmond Clark’s Middle Stone Age excavation at Chaminade 1A, Karonga, Malawi during the 1960s yielded utilized ochre artefacts suggestive of pigment production. Our 2011 survey of regional ochre deposits suggested that many potential sources are difficult-to-characterize, sedimentary rocks containing detrital minerals from diverse parent rocks. Here we report a new comparative study of three approaches to ochre provenance geochemistry. Instrumental Neutron Activation Analysis and two variants of Laser Ablation – Inductively Coupled Plasma Mass Spectrometry (1. Bulk Ochre “Paint Chip” Ablation and 2. Zircon Crystal Ablation) were applied to Malawian ochre source samples in order to test the Provenance Postulate and identify the minimum sample mass required for reliable characterization. While our results indicate that all three techniques are suitable for collecting trace element concentrations, “Paint Chip” Ablation data analyzed with multivariate statistics to highlight inter-group variation is the most effective method of distinguishing between ochre sources. A future sourcing study of the Chaminade 1A ochre assemblage using one or more of these techniques is warranted.