M. Steven Shackley

Sources of Archaeological Obsidian in the Southwest: An Archaeological, Petrological, and Geochemical Study

Comprehensive geochemical studies of archaeological obsidian sources in the Southwest typically have lagged behind other regions of North American and Mesoamerica. Current archaeological and petrological research indicates four previously unreported sources in Arizona, Sonora, and western New Mexico. This initial semiquantitative X-ray fluorescence (XRF) examination of archaeological silicic-glass sources in this region focuses on current technical problems in southwestern obsidian studies. The chemical variability within some regional obsidian sources appears to be relatively extensive and new data from the San Francisco volcanic field in northern Arizona modifies the results of earlier researchers.

An Introduction to X-Ray Fluorescence (XRF) Analysis in Archaeology

As I have discussed in the last chapter, our goal here is not to elucidate XRF for the entire scientific community – this has been done admirably by others – but to translate the physics, mechanics, and art of XRF for those in archaeology and geoarchaeology who use it as one of the many tools to explain the human past in twenty-first century archaeology. While not a simple exercise, it has utility not only for those like us, who have struggled (and enjoyed) the vagaries of XRF applications to archaeological problems, but for a greater archaeology. First, we trace the basic history of X-rays used in science and the development of XRF for geological and archaeological applications, and the role some major research institutions have played in the science. Following this is an explanation of XRF that, in concert with the glossary, illuminates the technology.

X-Ray Fluorescence Spectrometry (XRF) in Geoarchaeology

Introduction: Why XRF in Archaeology?- X-Ray Fluorescence Theory and Method.- Factors Affecting the Energy-Dispersive X-Ray Fluorescence (EDXRF) Analysis of Archaeological Obsidian.- Non-destructive EDXRF analyses of archaeological basalt.- Non-Destructive Applications of Wavelength XRF in Obsidian Studies.- Comparison and contrast between NAA and XRF: trace element analysis of the obsidian sources in central Mexico.- INAA versus XRF in Basalt Studies.- PXRF of archaeological artifacts: potentials and limitations.- Is There a Future for XRF in a 21st Century Archaeology?

Significance of Ecological Factors in the Middle to Upper Paleolithic Transition

For the first time, we have identified evidence that the disappearance of Neanderthals in the Caucasus coincides with a volcanic eruption at about 40,000 BP. Our data support the hypothesis that the Middle to Upper Paleolithic transition in western Eurasia correlates with a global volcanogenic catastrophe. The coeval volcanic eruptions (from a large Campanian Ignimbrite eruption to a smaller eruption in the Central Caucasus) had an unusually sudden and devastating effect on the ecology and forced the fast and extreme climate deterioration (“volcanic winter”) of the Northern Hemisphere in the beginning of Heinrich Event 4. Given the data from Mezmaiskaya Cave and supporting evidence from other sites across the Europe, we guess that the Neanderthal lineage truncated abruptly after this catastrophe in most of its range. We also propose that the most significant advantage of early modern humans over contemporary Neanderthals was geographic localization in the more southern parts of western Eurasia and Africa. Thus, modern humans avoided much of the direct impact of the European volcanic crisis. They may have further benefited from the Neanderthal population vacuum in Europe and major technological and social innovations, whose revolutionary appearance shortly after 40,000 BP documents the beginning of Upper Paleolithic.

Eastern Anatolian obsidians at Çatalhöyük and the reconfiguration of regional interaction in the Early Ceramic Neolithic

A small group of exotic obsidian blades supplied from over 600km distant reached a particular area of the East Mound at Catalhoyuk in the Early Ceramic Neolithic (7000-6300 cal BC). The authors explore a variety of explanations and contexts, including changes in technology, agricultural expansion, gift exchange, bride-wealth and incomers from the east.

Mesoamerican origin for an obsidian scraper from the Precolumbian southeastern United States

EDXRF analysis of an obsidian scraper from the Spiro Mounds, Oklahoma, shows that the source material was from Pachuca, Hidalgo, Mexico. Given the distinctive peralkaline character of the obsidian, the source assignment is considered extremely secure. The artifact was recovered from the east tunnel of Craig Mound, Spiro, immediately after the cessation of commercial digging in 1935, and has been in the Smithsonian’s collections since 1937. Despite more than 150 years of speculation regarding supposed contact with and influence from the region, this represents the first documented example of Mesoamerican material from any Mississippian archaeological context in the Precolumbian southeastern United States.

Classic Period Hohokam Obsidian Studies in Southern Arizona

AbstractDuring the last decade a number of obsidian studies have been conducted on Classic-periodHohokam artifacts from sites in southern Arizona. The geological and cultural settings of this region make it an ideal area for the study of raw material acquisition and distribution networks. The technique of X-ray fluorescence (XRF) spectrometry has been used as an inexpensive means to characterize sources and artifacts. This paper discusses the results of obsidian studies conducted on nine sites or site complexes within the Hohokam area. The dominant pattern of raw material procurement appears to be one of proximity, where the most commonly found obsidian on the site was usually obtained from the closest source. Procurement strategies indicate that obsidian procurement may have been secondary or parallel to the acquisition of other primary resources.

Dynamics of Hohokam obsidian circulation in the North American Southwest

Geochemical analyses of obsidian offer unexpected insights on the size and organization of the Hohokam regional system in the North American Southwest. Networks of obsidian circulation enlarged greatly during the Classic period as community centres with monumental architecture acquired non-local obsidian from a vast territory. This pattern confirms that prior models drastically underestimated the geographic scale of the Classic period regional system.

Clovis paleoecology and lithic technology in the central rio grande rift region, New Mexico

Abstract Clovis sites occur throughout the southwestern United States and northwestern Mexico, but are poorly documented in the central Rio Grande rift region. Here, we present data from two relatively unknown Clovis projectile point assemblages from this region: the first is from the Mockingbird Gap Clovis site and the second is from a survey of the surrounding region. Our goals are to reconstruct general features of the paleoecological adaptation of Clovis populations in the region using raw material sourcing and then to compare the point technology in the region to other Clovis assemblages in the Southwest and across the continent. Our results show that both assemblages were manufactured from similar suites of raw materials that come almost exclusively from the central Rio Grande rift region and the adjacent mountains of New Mexico. Additionally, we show that Clovis projectile points in the study region are significantly smaller than the continental average. Our results suggest that Clovis populations in this region operated within a large, well-known, and relatively high-elevation territory encompassing much of northern and western New Mexico.

X-Ray Fluorescence Spectrometry in Twenty-First Century Archaeology

Edward Hall’s abstract for his 1960 paper entitled “X-ray fluorescent analysis applied to archaeology” in the journal Archaeometry is just as appropriate half a century later. X-ray fluorescence spectrometry (XRF) is even more “well established” now, but is “not suitable for some projects” even though it might seem so, and archaeologists might think XRF is really appropriate. This volume is dedicated to issues in XRF analysis in geoarchaeology in particular. How does XRF work, and more importantly when and where is it appropriate? We have attempted to convey this without using physical science jargon, although it was difficult at many points. I have provided a glossary at the end of the volume to help in this direction.