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Ecuadorian Obsidian Sources Used for Artifact Production and Methods for Provenience Assignments

Published online by Cambridge University Press:  20 January 2017

Frank Asaro ,
Ernesto Salazar ,
Helen V. Michel ,
Richard L. Burger  and
Fred H. Stross
Frank Asaro
Affiliation:
Lawrence Berkeley Laboratory, University of California, 1 Cyclotron Road, Berkeley, CA 94720
Ernesto Salazar
Affiliation:
Departamento de Antropología, Universidad Católica del Ecuador, Quito, Ecuador
Helen V. Michel
Affiliation:
Lawrence Berkeley Laboratory, University of California, 1 Cyclotron Road, Berkeley, CA 94720
Richard L. Burger
Affiliation:
Department of Anthropology, Yale University, P.O. Box 208277, New Haven, CT 06520-8277
Fred H. Stross
Affiliation:
Lawrence Berkeley Laboratory, University of California, 1 Cyclotron Road, Berkeley, CA 94720
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Abstract

A study by neutron activation analysis and X-ray fluorescence measurements of 116 Ecuadorian obsidian artifacts as well as primary and secondary source samples has shown that the material originated from two Andean sources in north-central Ecuador, a flow in the valley of Mullumica, and deposits found on Yanaurco Chico and the nearby Quiscatola crest. The Yanaurco-Quiscatola deposit complex, homogeneous within our ability to measure, is represented by 18 percent of the artifacts. The Mullumica source has variable, apparently linearly related element abundances that may have resulted from the incomplete mixing of two magmas within a magma chamber. Seventy-eight percent of the samples studied are deduced to have originated from that source. Five artifacts from La Chimba cannot be assigned an origin, but four of them have the same provenience. To test the validity of the mixed-magma theory, we present equations to calculate the abundance of any measured element from that of iron. On the average, agreement within about 3 percent is obtained for artifacts.

Un estudio através del análisis de activación de neutrones (NAA) y medidas de fluorescencia de rayos-X (XRF) de 116 artefactos de obsidiana ecuatoriana y de fuentes primarias y secondarias ha determinado que el material proviene mayormente de dos fuentes geológicas andinas ubicadas en la zona norcentral del Ecuador; es decir, un depósito que se extiende del valle de Mullumica, y otro depósito que se encuentra tanto en el cerro de Yanaurco como en la zona cercana de Quiscatola. El complejo de depósitos de Yanaurco-Quiscatola es probablemente homogéneo dentro de nuestra capacidad para medir; 21 de los artefactos estudiados (18 por ciento del total) provienen de esta fuente. La fuente de Mullumica al parecer tiene una abundancia variable de elementos, lo cual hubiera resultado de la mezcla de dos magmas en una cámara magmática antes o durante erupción; 78 por ciento de los artefactos estudiados (90) provienen de esta fuente. Presentamos fórmulas para calcular la abundancia de cualquier elemento en la lava del flujo mezclado utilizando la abundancia de hierro. Acuerdo dentro del 3 por ciento es obtenido del promedio para artefactos. Cinco artefactos de La Chimba no pueden ser asignadas a una fuente conocida, pero cuatro de ellos tienen la misma procedencia geológica.

Type
Articles
Information
Latin American Antiquity , Volume 5 , Issue 3 , September 1994 , pp. 257 - 277
Copyright
Copyright © Society for American Archaeology 1994

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References

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