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Wallace Ruin Interim Report
Abstract
Descriptive report on results of excavations and analyses.
Two processes characterize the later precontact history (twelfth-fourteenth centuries) of the northern part of the American Southwest: aggregation of people into large towns and depopulation of large regions. These processes have been explained as the result of environmental, economic, and social factors, including drought and warfare. Using a theoretical perspective based on Pauketat’s “historical processualism,” we argue that aggregation and depopulation are partly the result of historical developments surrounding the expansion and collapse of the Chaco regional system. We present our understanding of the Chaco regional system from the perspective of historical processualism; then, historical developments in the northern San Juan and Cibola regions-northern and southern frontiers of the Chaco world-are compared. The northern San Juan"s historically close ties with Chaco Canyon, the post-Chaco regional center at Aztec, and other factors ultimately resulted in the region’s depopulation. In the Cibola region, ties with Chaco were more tenuous and use of Chacoan ideology appears to have been strongest in the post-Chaco era, though no post-Chaco regional center emerged. Instead, large towns developed. Built on novel combinations of independent histories, ritual, and experience with Chaco, large towns enhanced stability. They were encountered by early Spanish explorers and some persist to the present day.
Paint types on black-on-white pottery in the prehistoric American Southwest have had significance for both chronological and sociocultural interpretations. Visual attributes have formed the basis for distinguishing carbon- and mineral-based paints on ancient black-on-white pottery in the American Southwest for over 60 years. In this study, an SEM-EDS (scanning electron microscope-energy dispersive X-ray spectrometer) system was first used to make an independent objective determination of the mineral or non-mineral paint present on 15 Mesa Verde White Ware sherds. Then, a group of 19 people (including experienced archaeologists and newly trained individuals) examined and classified the paint on these sherds, achieving an overall accuracy of 84.2 percent. This group also ranked in priority order the visual attributes they felt were most useful in determining pottery paint type: nature of edges (fuzzy, sharp), absorption (soaks in, sits on top), luster (shiny, dull), color range (black-gray-blue; black-brown-reddish), flakiness (doesn't flake off, flakes off), thickness (thin, thick), and surface polish (polish striations visible through paint, striations not visible through paint). In each case, the attribute applicable to carbon-based paint is listed first. The most difficult sherds for the group to identify displayed attributes of both carbon and mineral paints. A category for "mixed" paint type, already in use by archaeologists, is a reasonable third category for labeling sherd paint, as long as it does not become a "catch-all" category. For problematic sherds, the SEM-EDS can be used to characterize paint type, then the visual attributes adjusted to improve investigator accuracy in paint type determination.
This article reports on the excavation of a "berm"-an earthen mound that surrounds the Bluff Great House in southeastern Utah. Comparisons are made to Chacoan-era (A.D. 850-1150) great house mounds in Chaco Canyon and to other berms and mounds at great houses throughout the Chacoan region. Great house mounds in Chaco Canyon and berms outside Chaco Canyon are assumed to have been ritual architecture, and continuity in the use of mounded earth and trash as a sacred place of deposit is traced through time from the Pueblo 1 period to modern Pueblos. The Bluff berm does not seem to have been constructed as the result of ceremonial gatherings (as has been suggested for the great house mounds in Chaco Canyon), but there is intriguing evidence that it continued to be used into the post-Chacoan era (A.D. 1150-1300), perhaps as a result of a restructuring or revival of Chacoan ideas in the northern San Juan region. Examination of the spatial distribution of berms suggests that they are most common at great houses south and west of Chaco Canyon; the northern San Juan region, where Bluff is located, has far fewer such features, possibly because the revival of Chacoan ideas in this region was short-lived.
Intensive architectural and dendrochronological analysis of Sand Canyon Pueblo, a large, late 13th-century Anasazi site in sw Colorado, has provided evidence of distinct building patterns. Although the principal pattern seems to be accretionary, there is evidence of planning both at the architectural unit scale and in the site as a whole. Evaluation of construction-labor intensity and spatial analysis have allowed the identification of functional architectural differentiation within the site. Site planning, community-scale building episodes, massive architectural style, and special function buildings and spaces point to the probability that Sand Canyon Pueblo served both as a large-scale dwelling place (e.g., a village) and as an integrative center for an outlying community. This organizational pattern may be a continuation or revival of the specialized Chacoan regional organization seen in the northern Southwest in the late 11th and early 12th centuries, or it may be an expression of more generalized Anasazi settlement aggregation.
Using the occupation histories of 3.176 habitation sites, new estimates of maize-agriculture productivity, and an analysis of over 1,700 construction timbers, we examine the historical ecology of Pueblo peoples during their seven-century occupation (A.D. 600-1300) of a densely settled portion of the Mesa Verde archaeological region. We identify two cycles of population growth and decline, the earlier and smaller peaking in the late-A.D. 800s, the later and larger in the mid-A.D. 1200s. We also identify several episodes of immigration. Formation of aggregated settlements, which we term community centers, is positively correlated with increasing population and the time elapsed in each settlement cycle, and it persists during periods of regional population decline, but it does not correlate with climatic variation averaged over periods. Architectural and land-use practices depleted pinyon-juniper woodlands during the first cycle, but more stable field systems and greater recycling of construction timber resulted in more sustainable management of wood resources during the second cycle, despite much higher population densities. Our estimates for maize production are lower than previous estimates, especially for the A.D. 1200s, when population reached its peak in the study area. Even so, considerable potential agricultural production remained unused in the decades that immediately preceded the complete depopulation of our study area.
Raman and infrared microscopy have been used to characterise the black pigments on prehistoric Southwest American black-on-white pottery. Conclusive spectroscopic evidence for the use of carbon-based paints on these sherds has been provided using the Raman technique. Maghaemite (γ-Fe2O3) and magnetite (Fe3O4), found alternatively or mixed with a carbonaceous pigment, were also identified on some sherds. Infrared measurements indicated that little, if any, organic material from biogenic precursors of the black pigment or from pigment binding agents remained in the paints. These spectroscopic results were obtained rapidly and non-destructively on unprepared samples, and the resulting data complement, and in some instances correct, paint type conclusions drawn from studies involving techniques such as XRD, SEM-EDX, and XPS.
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