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. 2001 Oct 9;98(21):11891-6.
doi: 10.1073/pnas.211305498. Epub 2001 Sep 25.

Strontium Isotopes Reveal Distant Sources of Architectural Timber in Chaco Canyon, New Mexico

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Strontium Isotopes Reveal Distant Sources of Architectural Timber in Chaco Canyon, New Mexico

N B English et al. Proc Natl Acad Sci U S A. .
Free PMC article

Abstract

Between A.D. 900 and 1150, more than 200,000 conifer trees were used to build the prehistoric great houses of Chaco Canyon, New Mexico, in what is now a treeless landscape. More than one-fifth of these timbers were spruce (Picea) or fir (Abies) that were hand-carried from isolated mountaintops 75-100 km away. Because strontium from local dust, water, and underlying bedrock is incorporated by trees, specific logging sites can be identified by comparing (87)Sr/(86)Sr ratios in construction beams from different ruins and building periods to ratios in living trees from the surrounding mountains. (87)Sr/(86)Sr ratios show that the beams came from both the Chuska and San Mateo (Mount Taylor) mountains, but not from the San Pedro Mountains, which are equally close. Incorporation of logs from two sources in the same room, great house, and year suggest stockpiling and intercommunity collaboration at Chaco Canyon. The use of trees from both the Chuska and San Mateo mountains, but not from the San Pedro Mountains, as early as A.D. 974 suggests that selection of timber sources was driven more by regional socioeconomic ties than by a simple model of resource depletion with distance and time.

Figures

Figure 1
Figure 1
Map of the San Juan Basin. Dark gray shading indicates spatial extent of modern spruce-fir forests, light gray for continuous stands of ponderosa pine. Triangles are sampling sites for modern trees.
Figure 2
Figure 2
87Sr/86Sr ratios of live trees and local waters from sampled sites. Dark shading represents the mean 87Sr/86Sr ratio (95% confidence interval) of live wood samples analyzed without regard to species. Light shading represents full range of modern wood 87Sr/86Sr ratios from each area. Analytical errors are smaller than symbols shown.
Figure 3
Figure 3
87Sr/86Sr ratios of great house architectural timbers compared with means and ranges of live trees from the San Pedro, San Mateo, and Chuska mountains. Other great houses are Wijiji, Hungo Pavi, and Una Vida. Means (dark shading) and ranges (light shading) are from live wood shown in Fig. 2.

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