Reports the results of the XRF analysis of 132 artifacts from a severely disturbed site on Butte Creek in the Western Cascades of Oregon. We took a look at this particular site because it lay in a geographic area in which almost no previous provenience studies had been undertaken. The trace element analysis of these artifacts not only demonstrated the utility of obsidian studies at disturbed sites, but also provided an example of the serendipitous good luck that sometimes accompanies a geochemical fishing expedition like this one - a new local obsidian source was identified.

Reports the results of XRF analysis of an obsidian biface fragment from the Fort Hill Hopewell Site in Ohio. Obsidian Cliff in Yellowstone National Park proved to be the geologic source of the artifact. The results of this report were the basis for an article that appeared in Archaeology in Eastern North America 26:33-39 (1997 - Bradley Lepper, Craig E. Skinner, and Christopher M. Stevenson).

This report is a bit more complex than our average model but contains the results of some interesting experimental studies that we conducted on the effects of heat on obsidian hydration rim measurements and rim survival. The analyzed artifacts were collected from two sites that had been severely burned in a 1993 forest fire in the Deschutes National Forest of Oregon. For more information on the effects of fire on hydration analysis, see the Other Articles and Report section below.

During the PGT-PG&E Pipeline Expansion Project (PEP) carried out in the early 1990's, over 9,500 obsidian artifacts from 133 Oregon, California, and Idaho archaeological sites were selected for obsidian characterization studies (Table 1). The trace element composition of 9,059 of these items was determined by X-ray (XRF) fluorescence spectrometry and the resultant elemental abundances were used to identify the geochemical sources of the samples (Skinner 1995a). All Oregon and Idaho artifacts were analyzed by Richard E. Hughes (Geochemical Research) who, along with BioSystems Analysis, also characterized the California specimens. After geologic source identification, the majority of the obsidian artifacts were then examined for the presence of obsidian hydration rims. Several chapters, including all of those associated with the obsidian studies, may be downloaded here.

Abstract: The Little Lake biface collection comprises 26 complete biface preforms. The bifaces are believed to have been found in a cache acquired near the vicinity of the town of Little Lake, Inyo County, California. All the complete bifaces have hydration values falling within a very tight range measuring from 3.5 to 3.8 microns and were determined to have come from the West Sugarloaf subfield of the Coso quarry cluster. These rim readings signify a brief single episode of time and would date to the very late Haiwee or the early Marana Periods in the Owens Valley cultural sequence or ca AD 1300. The cache would lend some limited support to the continued use of large biface cores as a means of production and transport of portable units of toolstone significantly later than might be expected in a volume/mass that is surprising.

The Northern Great Basin Prehistory Project is a joint undertaking of the University of Oregon (UO) Archaeological Field School, UO Department of Anthropology, Museum of Natural History, Department of Geography, and Office of Summer Sessions, the Lakeview, Prineville, and Burns District Offices of the Bureau of Land Management, the Deschutes (Bend) and Malheur (John Day) National Forests, and the Sundance Archaeological Research Fund and Department of Anthropology, University of Nevada, Reno (UNR).

If you have an interest in the effects of fire on obsidian artifacts, this is a must-have publication. This volume consists of 14 papers based on presentations given at a 1999 symposium, The Effects of Fire/Heat on Obsidian, that was held at the 33rd Annual Meeting of the Society for California Archaeology (Sacramento, California). To download a short (260K) additional erratum sheet, click HERE

Abstract: Seventeen known and four unknown sources among 90 obsidian artifacts were identified from the Lost Dune and McCoy Creek sites on the east side of Blitzen valley, Harney County, Oregon. Changing distributions and abundances of obsidian sources identified in four prehistoric periods (3,500-2,000 B.P., 2,000-500 B.P., A.D. 1400s and A.D.1500s) suggest eastern Blitzen Valley people used a limited resource area in the middle two periods. For the period from 2,000 to 500 B.P., obsidian was identified only from sources in and adjacent to Harney Basin and in the northern Catlow Valley - the "western Malheur.Catlow area. Then, briefly in the A.D. 1500s, pottery-using visitors brought to Lost Dune ample obsidian from sources well east of Harney Basin in the Owyhee River drainage.

From the Abstract: Nonhydrated obsidians are quenched magmatic liquids that record in their chemical composition details of the tectonic environment of formation and of the differentiation mechanisms that affected their subsequent evolution. This study attempts to analyze, in terms of geologic processes, the compositional variations in the Subalkalic obsidians... New major- and trace-element determinations of 241 samples and a compilation of 130 published major-element analyses are reported and interpreted.

From the Abstract: Peralkaline rocks are one of the characteristic products of non-origenic magmatism, and the development of peralkaline silicic magmas continues to be a problem of special interest to petrologists. The problem is complicated by the fact that crystallization of these highly alkaline melts commonly result in significant chemical changes, such that the study of quenched liquids (glasses) is probably the only reliable approach to magma compositions. In this report, all acceptable analyses of oversaturated peralkaline obsidians are listed and compared in an attempt to provide a sound basis for further studies of peralkaline silicic magmatism.

This piece of research, the first substantial one that we finished under the name of Northwest Research, was completed in 1991. We always felt that this was a nicely done investigation although the final project report susequently disappeared deep into the vast murky reservoir of U. S. Forest Service gray literature.

Abstract: Identifying lithic sources is central to understanding toolstone use by prehistoric hunter-gatherer groups. The distribution of archaeological materials in relation to geologic sources creates a spatial pattern of use that varies through time. These patterns of distribution in conjunction with analysis of technological organization can be used to infer behavior, especially levels of mobility. This thesis presents geochemical data from a wide-scale sourcing study in the Bonneville basin of western Utah and eastern Nevada. Results of this investigation are presented, including discussion of newly identified geologic source groups and further characterization of previously identified sources, outcome of X-ray fluorescence analysis on approximately 600 fine-grained volcanic (FGV) artifacts from a host of open sites in the Old River Bed delta and from caves/rockshelters including Danger Cave, Bonneville Estates Rockshelter, and Camels Back Cave, and a brief look at how the inhabitants of this region varied FGV-toolstone use through time.

Abstract: This research integrates the analysis of obsidian geochemistry with investigation on the effects of forest fires on obsidian artifacts in surface assemblages. The first component of this project investigated the nature of heat altered obsidian at a prehistoric quarry sites following the 1996 Dome Fire in the Jemez Mountains of northern New Mexico. Burned artifacts were examined to discern indicators of heat alteration in obsidian and to measure the impact of fire on obsidian hydration (OH) bands. Descriptive categories developed to encompass a range of fire effects are provided here as a tool for identifying heat-altered obsidian in archaeological contexts. Measurement of obsidian hydration in artifacts collected from across the site demonstrated substantial loss and alteration of OH information, as well as positive correlation of OH loss/alteration with degree of burn severity.

The second component of the project investigated the role of obsidian geochemistry in fire effects, especially obsidian vesiculation. Intrasource and intersource geochemical analyses of obsidian trace element composiiton were integrated with analysis of major/minor elements, and with analysis of the water content as a volatile constituent. Results show elemental homogeneity among the Dome area Obsidian Ridge/Rabbit Mountains obsidians of the Cerro Toledo Rhyolite (CTR), deomstrate a cogenic realtionship among geographically separate CTR deposits, and confirm that these obsidians are chemically distinct from Valles Rhyolite (VR) glasses as Cerro del Medio. Analyses of obsidian water content using loss-on-ignition (LOI) and infrared spectroscopy (FTIR) demonstrate the efficacy o both techniques for archaeological applications. Water contents were found to be low in VR samples, but high and variable in CTR samples. These results accord with the expectation of higher and more variable water contents in glasses from pyroclastic deposits, as compared with lower water contents in glasses from extrusive volcanic contexts This study provides a new example in which obsidian water content is high and variable within a single chemical type. This example provides support for the inclusion of water contents as a compositional variable in the OH dating model and demonstrates the utility of integrating analysis of both elemental and volatile composition into archaeological practices of obsidian geochemical analyses.

From the Abstract: Geochemical characterization methods are commonly used in the reconstruction of prehistoric raw material use and procurement systems. Trace element studies of lithic source materials and artifacts, specifically those made of obsidian, can reveal important information about the environmental and cultural factors which influence the prehistoric distribution of raw material. The current investigation use geochemical characterization methods and data to document and evaluate the distribution of geologic and artifact obsidian that originates from the Silver Lake/Sycan Marsh (SL/SM) obsidian source. This large and prehistorically significant source is located in western Lake County, Oregon. Few source descriptions or artifact distribution studies exist for SL/SM obsidian. However, over the past decade, a significant increase in the use of geochemical characterization methods has generated a wealth of data for Oregon obsidian sources. This thesis synthesizes the results of the geochemical characterization analysis of 392 geologic obsidian specimens collected from the SL/SM source area and 1,938 SL/SM obsidian artifacts recovered from over 200 sites in Oregon, Washington and California. The artifact analytical data were derived from previously characterized artifact collections compiled and archived in an extensive database. A subset of artifacts were characterized for the purpose of this study.

Abstract: Regional studies of obsidian artifacts in the south-central Andes have shown thath over 90% of the analyzed obsidian artifacts from the Lake Titicaca Basin belong to a single geochemical obsidian type. A decade ago researchers identified the geologic origin of this obsidian as the Chivay/Cotallalli source, located 180km west of Lake Titicaca above the Colcaa Valley in Arequipa at 71.5355º S, 15.6423º W (WGS84), and at 4972 meters above sea level. This research project focused on the obsidian source and adjacent lands within one day's travel from the source. The project included a 33km² survey, 8 test units, and in-depth lithic attribute analysis. Mobile GIS (Arcpad) was used extensively during survey. A substantial quarry pit and an obsidian workshop were examined closely, as were consumption sites in nearby areas. The results of this study found that the earliest diagnostic materials at the source date to he Middle Archaic (8000-6000 BCE) and that intensification of obsidian production occurred earlier than previously recognized, at circa 3300 BCE. Increased obsidian production appears to have been focused on the acquisition of large (>20cm) and homogeneous obsidian nodules, although the formal tools produced with obsidian were predominantly small projectile points. It is argued that the acquisition of large, homogeneous nodules was prioritized because the production potential of large nodules was highest, and because obsidian was associated with competitive display among early aggrandizers. The timing and economic associations of obsidian production and circulation suggest that the possession of large obsidian pieces in the Titicaca Basin was a demonstration of social connections to distant resources, and to regional trade networks that emerged with regular camelid caravan transport networks. Obsidian artifacts were not niherently "prestige goods"; rather, it is suggested here that obsidian was the least-perishable of a number of cultural goods distributed by an expanding network of caravans that linked communities in the region. The acquisition and consumption of these cultural goods was a demonstration of economic connections and cultural influence during the dynamic period of incipient social inequity between the Terminal Archaic (3300-2000 BCE) through the Middle Formative (1300-500 BCE).

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