Distribution and sources of obsidian in the Rio Grande gravels of New Mexico

Abstract

The obsidian in the gravels deposited by the Rio Grande in New Mexico has interested archaeologists of the region, particularly the use of these gravels by prehistoric populations and the implications for obsidian sourcing studies. Previous investigations of Rio Grande gravel obsidian have focused on obsidian in the archaeological record. This study focuses on the natural occurrence and distribution of obsidian in the gravels and the implications for archaeological investigations. Spatial sampling of the gravels clearly indicate that obsidian, as well as other chipped stone material, is not uniformly distributed across the landscape. Geochemical analysis of the obsidian in the gravels establishes the true source constituents for the obsidian present in the gravels. The main source area for obsidian in the Rio Grande gravels is the Jemez Mountains, although some obsidian comes from Grant's Ridge, Polvadera, and No Aqua sources. Sources south of Mount Taylor, such as Red Hill and Mule Creek, do not occur in the Rio Grande gravels of southern New Mexico. © 2000 John Wiley & Sons, Inc.