Obsidian Research Articles

New Results Concerning Expanded Networks of Obsidian Procurement in San Matías Gulf, Río Negro, Patagonia, Argentina

ABSTRACTIn this article we characterize the obsidian types present along the San Matías Gulf coast through geochemical analyses and we perform a techo-morphological analyses of the recovered artifacts. Also, we present a new obsidian type that has been found for the first time in the Atlantic coast of Patagonia. By this means we hope to better evaluate trends in the circulation and use of this raw material in the San Matías Gulf during the Middle and Late Holocene. As a result, we propose that there is a differential distribution between northern and southern Patagonia and among coastal sites (black and gray obsidians). This disparity could be mainly related to spatial distance, or to different mobility patterns of the human groups or to differential availability of the sources during the year. Growing evidence also suggests different raw material circulation.

Obsidianas en el Tardío-Inka de Antofagasta de la Sierra (Puna meridional argentina): ¿fondo de cuenca versus sectores intermedios?

Fil: Escola, Patricia Susana. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro de Investigaciones y Transferencia de Catamarca. Universidad Nacional de Catamarca. Centro de Investigaciones y Transferencia de Catamarca; Argentina

¿Intercambio O Movilidad?: Una Evaluación Sobre El Uso De Escalas De Análisis Espaciales Y Curvas De Declinación En Patagonia Centro-Meridional (Argentina)

Throughout south-central Patagonia, at the southern tip of South America, artifacts of black obsidian and marine materials are found at sites far from their sources. This distribution is often attributed to the existence of exchange systems among hunter- gatherer groups occupying the region in the late Holocene. In this article, we analyze distance-decay patterns in the frequencies of both items. We explore the use of decay curves for explaining the existence of exchange systems. We also discuss the notion of exchange as a means of obtaining exotic goods. We conclude that there is much intermediate variation that is not explained by the ideal extremes of exchange or mobility (i.e., direct acquisition mode). This variation includes possible visits or other types of social interaction associated with open social formations. We argue that these mechanisms are relevant to understanding the distributional patterns of goods with known source locations recorded in south-central Patagonia.

Raw material circulation at broad scales in southern Patagonia (Argentina): The cases of the Chico and Santa Cruz River basins

The purpose of this paper is to begin to understand human mobility through rock transport at different times in two areas with different environmental characteristics: the Southern Deseado Massif and the basaltic canyons north of the Santa Cruz River. We focus on obsidian, which has a clear geochemical signature and an uneven distribution. Additionally, we use macroscopic information on siliceous rocks, which at present have only been identified in northern areas, although they may also be recovered randomly and in low frequencies in southern ones.During the initial peopling of the Southern Deseado Massif (ca. 10,800 BP), inhabitants were transporting black obsidian as well as translucent chalcedony, probably as part of the individual gear. During the Late Holocene, the number of obsidian artifacts decreased in the Southern Deseado Massif, related to a better knowledge of the high-quality local lithic resources and/or to the existence of higher population densities. Obsidian artifacts are more abundant in the northern Santa Cruz River basin than in the southern Deseado Massif, suggesting the existence of a relationship with areas located to the northwest, close to the obsidian source, as other lines of evidence suggest. In addition, the presence in the basaltic canyons of artifacts made from high-quality siliceous rocks, more abundant and predictable in northern areas, could also be the result of human movements following a north-south direction.

The Selene Obsidian Source (Formerly Sonora Unknown B) of the Upper Río Bavispe Basin, Sonora, Mexico

An energy-dispersive X-ray fluorescence (EDXRF) analysis of nineteen obsidian source rocks from a mid-Tertiary rhyolite/perlite flow in the upper Río Bavispe basin of northeastern Sonora, Mexico solves the location of “Sonora Unknown B” as reported by ) for recent archaeological projects in northeastern Sonora and southeastern Arizona. This newly discovered source, called Selene, is a relatively large marekanite source consisting of a very high-silica rhyolite with regionally distinct high barium (Ba) and strontium (Sr) values, and low zirconium (Zr) elemental concentrations. The Selene nodules are relatively large compared to nodules from other northern Sonoran and Chihuahuan obsidian sources, and have excellent knapping qualities. We believe these attributes contributed to the transport, trade, and use of Selene obsidian hundreds of kilometers from the source. This is in contrast to marekanites from some other sources in northwestern Mexico, which were at most transported and used a few tens of kilometers from their sources (; :77).

Primeros avances en la caracterización de vulcanitas de afloramientos de Antofagasta de la Sierra (prov. de Catamarca, Argentina)

En distintos sectores de la microrregión de Antofagasta de la Sierra (Provincia de Catamarca, Puna Meridional Argentina) se registran afloramientos de vulcanitas (rocas volcánicas con proporciones de vidrio menores a 80%, sensu Aschero et al. 2002/2004) macroscópicamente muy similares. Con el objetivo de diferenciarlas y aportar, de esta forma, a su identificación en el registro arqueológico, se aplicaron diversos métodos y técnicas sobre muestras de estas rocas procedentes de los distintos afloramientos. En esta instancia, se exponen los resultados obtenidos a partir de caracterización geoquímica por medio de Fluorescencia de Rayos X de Energía Dispersiva. Las vulcanitas procedentes de los diferentes afloramientos tienden a presentar disímiles concentraciones de ciertos elementos. Estos resultados son prometedores y estimulan a continuar investigando la aplicación de métodos geoquímicos en la diferenciación y determinación de la procedencia de estas rocas volcánicas. Cabe destacar que en el Noroeste Argentino los métodos geoquímicos fueron exclusivamente aplicados sobre una roca volcánica específica, la obsidiana, y aún no habían sido utilizados en otras rocas volcánicas anisótropas, con superficies, texturas y estructuras más irregulares.

MULTIPLE PRIMARY AND SECONDARY SOURCES FOR CHEMICALLY SIMILAR OBSIDIANS FROM THE AREA OF PORTADA COVUNCO, WEST‐CENTRAL NEUQUÉN, ARGENTINA

In west‐central Neuquén Province, Argentina, in the area around Estancia Llamuco, west of Zapala, south of Las Lajas and north‐east of Lago Aluminé, there are multiple primary and secondary sources of obsidian. Primary sources occur within the south‐east extension of the Plio‐Quaternary volcanic chain that runs from Copahue volcano through Pino Hachado. Secondary sources include river‐bed gravels within the valleys of Arroyo Cochicó Grande and Río Kilca as far south as where this river joins with Río Aluminé, and the Quaternary fluvial–glacial sediments cut by the valley of Río Covunco as far east as Portada Covunco. Visually variable obsidians from these two secondary sources include homogeneous black and grey‐translucent types, porphyritic and banded types, and an abundant quantity of oxidized red and black obsidian. However, all these visually distinct obsidians have similar and unique chemistry, with Ba between 220 and 340 ppm, different from any other obsidians previously reported from Neuquén, which all have Ba > 500 ppm, as do obsidians from sources to the north in Mendoza and to the west in Chile. This chemical distinctive obsidian has been exploited and transported over a wide area, beginning prior to 4000 bp, and occurs in local archaeological sites, as well as sites ≥ 300 km to the north‐east in La Pampa Province, ∼430 km to the south in Chubut Province, and >75 km to the west across the Andean drainage divide in Chile.

Direct multielement determination of trace elements in boron carbide powders by direct current arc atomic emission spectrometry using a CCD spectrometer

The use of direct current arc atomic emission spectrometry (DC-arc-AES) with a CCD spectrometer for the direct determination of the trace impurities Al, Ca, Cr, Cu, Fe, Mg, Mn, Na, Ni, Si, Ti, and Zr in three well characterized boron carbide powders is described. The detection limits obtained by the procedure were found to be between 0.2 (Mg) and 25 (Na) μg g−1 for the above elements. Three boron carbide powder samples with trace element concentrations between 0.9 (Cu) and 934 (Si) μg g−1 for Al, Ca, Cr, Cu, Fe, Mg, Mn, Na, Ni, Si, Ti, and Zr — including the standard reference material ERM®-ED102 — were analyzed by DC-arc-AES. The relative standard deviations for 9 measurements when using 5.0 ± 0.3 mg of the respective samples were found to vary from 6.2 to 27% for Al and Cu, respectively. The trace elements Al, Ca, Cr, Cu, Fe, Mn, Ni, Si, Ti and Zr could be determined in the standard reference material and their concentrations determined by DC-arc AES were found to be between 89 and 116% of the accepted values. Fe and Ti were determined by DC-arc AES in the three boron carbide samples as well as in Al2O3, BN, SiC, coal fly ash, graphite and obsidian rock. The correlation coefficients of the plots of the net intensities versus the accepted values over the concentration ranges from 18 to 1750 and from 6 to 8000 μg g−1 are 0.999 and 0.990 for Fe and Ti, respectively.

The Lami pyroclastic succession (Lipari, Aeolian Islands): A clue for unravelling the eruptive dynamics of the Monte Pilato rhyolitic pumice cone

The Lami succession piled up during the explosive activity of the Monte Pilato on Lipari Island (Central Aeolian Arc, Italy). It comprises a repetitive alternation of fall and pyroclastic density current beds, which define 13 Units separated by fine ash beds. Despite the homogeneous rhyolitic composition the juveniles fragments show strong textural heterogeneities from highly vesicular pumice to dense black obsidians. The pumice types are termed: i) “tube”, which shows elongated tubular vesicles, ii) “frothy”, highly vesicular with large, sub-rounded vesicles, and iii) agglomerated and welded. Two types of obsidian pyroclasts are recognized: i) aphyric black obsidian, and ii) grey obsidian showing spherulitic texture. All these pyroclastic types occur throughout the stratigraphic succession, and mixed in the same bed. They account for changing physical conditions along the conduit, which is hypothesised to be filled by a melt plug during the eruption of 12 out of 13 Units. The strong textural heterogeneities of the juvenile fragments testify for the existence of differential shear rates, which can be explained though two shear mechanism: i) simple shear, producing horizontal zonation of texture in the conduit with black obsidians along the conduit walls passing to tube and frothy pumice to the centre, and ii) pure shear, producing a vertical zonation in the conduit, with black obsidians at the top overlying frothy pumice. Agglomerated and welded pumice of Unit 13 is thought to represent the portion of magma heated by a batch of hotter melt that entered the magma chamber and triggered the eruption. The deposits of Unit 13 represent a unique case of spatter accretion due to accumulation of hot, low-viscous rhyolitic pumice fragments, emplaced from pyroclastic fountaining.

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Microlite textures and volatile contents of obsidian from the Inyo volcanic chain, California

We test the hypothesis that microlite textures record progressive degassing during magma ascent. We compare microlite number density (NV) and H2O concentrations in pyroclastic and effusive obsidian (OBS) from the Inyo Volcanic Chain, CA. Comparisons reveal a weak correlation between microlite NV and H2O; however, most obsidians (OBSs) of a given volatile content exhibit a wide range of NV. Factors other than degassing must also influence final groundmass texture. We postulate that OBS textures record different ascent rates and residence histories prior to eruption from the conduit. We conclude that microlites do not sensitively indicate the extent of magmatic degassing, rather, they provide qualitative indications of magma ascent and residence time.

SEM-EDS microanalysis of microphenocrysts of Mediterranean obsidians : a preliminary approach to source discrimination

SEM-EDS non-destructive analysis allows the source discrimination of the various microphenocrysts in obsidian rocks of the Mediterranean. Samples of six Mediterranean sources, Monte Arci (Sardinia), Palmarola, Lipari, Pantelleria, Gyali and Melos were studied using SEM-EDS non-destructive techniques in order to obtain a data base of their microphenocryst content. The results demonstrate that provenance of an obsidian can be distinguished on the basis of its petrography, in particular by quantitative analyses of Fe-Mg microphenocrysts; this information is particularly useful when coupled with data obtained by other non-destructive techniques such as glass microanalysis of artefacts (Acquafredda et al. , 1999). Such investigations, carried out by SEM, an analytical technique relatively accessible to geoarchaeologists, are relatively rapid, effective and above all non-destructive.

Devitrification of natural rhyolitic obsidian glasses: petrographic and microstructural study (SEM+EDS) of recent (Lipari island) and ancient (Sarrabus, SE Sardinia) samples

Microstructural evolution of devitrification of obsidian glasses is a process not fully understood, especially with reference to preferred nucleation sites and anisotropic development of spherulites. Evidence is commonly hidden in advanced devitrification textures. Two sets of naturally devitrified obsidian rocks, calcoalkaline rhyolitic in composition, have been used to test how this process develops. A petrographic and SEM+EDS comparative study of incipient devitrified recent obsidian (from Lipari island) and advanced devitrified ancient rhyolitic rocks (from Sarrabus region, Sardinia island, Italy) allows following successive stages in the generation of K-feldspar spherulites in natural glasses. Spherulites show a preference for epitaxial nucleation over previous minute idiomorphic crystals and a number of processes including rearrangement of initial mineral fibers and interstitial voids lead to the formation of blade-like crystals and denser spherulites. In some cases bubbles with an inferred origin associated to secondary boiling of magmas also favour spherulitic nucleation.

Early human occupations in Western Santa Cruz Province, Southernmost South America

This paper discusses basic tendencies in the characteristics of the early archaeological record corresponding to human occupation near the eastern flank of the Andean range, at the southern end of South America. Lithic artifacts are analyzed within an organization of technology perspective and are discussed according to Borrero's ecological model of the peopling of Patagonia. The characteristics of the lithic artifacts along with raw material provenience at the oldest levels at sites Cerro Casa de Piedra 7 and Chorrillo Malo 2, match our expectations for an exploration or early colonization phase in the peopling of the space. In addition, the range of variation of tools is similar to that present at early sites located to the east of the area. Some differences at these sites are already evident. Among these are the higher tool deposition rates at sites located close to Pampa del Asador, a known source of black obsidian that was used by early inhabitants of Patagonia. This poses some new questions that should be addressed regionally, taking into account the regional availability of lithic resources.

Determination of minor and trace elements in obsidian rock samples and archaeological artifacts by laser ablation inductively coupled plasma mass spectrometry using synthetic obsidian standards

Accuracy and repeatability of analytical results obtained by laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS) critically depends on the availability of calibration standards, which should ideally have a matrix composition very close to the samples being analyzed. The preparation of synthetic obsidian standards (SOS) is described in this work, their minor and trace element composition (>40 elements), determined by solution nebulization ICP-MS and inductively coupled plasma optical emission spectrometry is presented and their performance in the quantitative and semiquantitative analysis of obsidians by LA-ICP-MS is discussed. Due to matrix matching of SOS and natural obsidians, internal standardization of the analyte intensities by 27Al or 29Si had no significant effect on the final results. Good analytical curves ( r 2>0.995) were obtained with the SOS series, permitting quantitative determination of a large number of trace elements in geological and archaeological samples with repeatabilities typically between 5 and 10% and adequate accuracies, as shown by the generally good agreement between solution nebulization and laser ablation data for the same samples. Results obtained in the fast semiquantitative mode of calibration were in most cases statistically not different from those obtained by the quantitative mode. This, for the routine analysis of a large number of samples attractive feature, was achieved by the use of 47 quantified elements in SOS for updating of the response factors. An example for the application of analytical methodologies introduced in this work is shown in provenance studies of archaeological obsidian artifacts from Ecuador.

Atomic-Scale Vacuities and Age of Obsidians

Atomic-Scale Vacuities and Age of Obsidians

A Gigolo's Ghee Gilded William

What I was lacking you brought from beneath a ghat I was building a gimbal and it cracked I was unbraiding a giaour's meditated tuft while you sought surplus purple for a gamay garment Your geyser always shared in prescription store aisles while malevolent Mimes aimed hoses into the ocean with things burning right beside But your eyes and even rinds were sucked yesterday through gills above wavetips and over Mojave-made azure gharries We scaled gagging spires and gutted ourselves Labioratory gone through a gloryhole on Fell That tan transmitter taken from Rose where waning white accordion waves past collapsing places Green grams fanned through air and the irrigation corps dessicates in stations A vaulted sky vulnerable with nimbus symptoms Ambulance tremulates lengthening silences In an opaline shell navigating space you fell at Io and we owe isolate lighthunting faces who overdrew an inventory for an old dosage boat We never broke pelicans or shot at odious offshore ships Cinnamon-colored clinamen obscures that ocean and I oar out We never spat our objections in a speck flask of obsidian We rung orange canalwater from two rags All the ones I dream of are children Now comes Asian flute music and a despicable feeling Seck fractured voices from vaporous places No longer even questions but the sound of questioning I dream of azalea-colored eyes on a warm orb that kisses and a family that builds vessels because it wants to tide water to places of somestic dunes that swallow trauma Your tongues were wild hoes of astral agriculture We tinged until two we began In your midst I had three friends Double Trochee, Dilator, and Flora-Flare The diceholes filled with dew and you swam Filled with lobal foam and you beamed A flea was riding a porpoise and they were in love! Verdant Shunt would take us by the face To the orchid store on the 33 in deranging rays The fluttering inverted comb the softly bouncing snout of a dead September seahorse in a tank with a darting disc and oval pieces Blood does not accrue but moves I pretend there is something in the sand the water wants that the center of the sea is silent that at its ends one hears backwash ramming incoming walls and to the southwest a torquoise blasting ship on glassy resins Cunning things thrive in cummy dungeons No longer our songs but the ache of playing The spider played its needles the cunning thing came and was inverted its pill drained Together we annihilated the spider then fed it to a sparrow We pounded the sparrow to powder We rolled a Hell Bank dollar and brought the sparrow inside We rhymed pearls in advance of the sadness of the Chinese boy who chased a rolling melon - Why is my melon running away from me? …

Obsidian provenancing and magmatic fractionation in central oregon

AbstractIn many instances, geologically distinct obsidian flows located within even a relatively small geographic area can be uniquely identified by their chemical composition. This happens to be true for several obsidian sources from central Oregon. Internally each obsidian locality is chemically homogeneous, but the obsidian rocks from different collection sites exhibit chemical differences. Based on the geochemical variations and on K/ Ar dating of the end members of the chemical differentiation trend, these differences are related to the fractionation of a single Late Miocene magma chamber, dated at 6.5 Ma. By understanding the underlying causes of the chemical differences, constraints are disclosed that will govern the possible chemical variations of other, as yet unidentified but related obsidian flows. These can be useful for identifying the possible natural sources of obsidian artifacts which do not match known obsidian sources, and for suggesting possible geographic areas where these as yet undiscovered obsidian flows may be found. © 1993 John Wiley & Sons, Inc.

The Origin of the Obsidian Artefacts from Mujahiya — A PPNB Site in the Golan Heights

Etude de provenance d'objets d'obsidienne de ce site PPNB (Aswadien), fondee sur l'analyse par activation neutronique et la spectrometrie gamma. Mise en evidence d'une source anatolienne, Golludag

Raw Materials Analysis by XRF in the Cement Industry

AbstractThe sources of raw materials used in the manufacture of Portland cement include pure to argillaceous limestones, shale and clay, plus minor quantities of sand, iron ore, fly ash, coal ash and suitable industrial wastes. To ensure a high quality product, rapid - precise - reproducible and practical analytical techniques are required. Quantitative XRF analysis techniques meet those demands.For this comparative technique, the instrument used is a wavelength dispersive sequential spectrometer. The advantages and the drawbacks of the technique are discussed, along with the procedure of the specimen fused bead preparation. The importance of calibration standards and unknown samples being prepared in an identical manner, and being presented to the instrument under similar conditions, is stressed. International and synthetic standards, concentration ranges for the five major elements, mathematically generated coefficients to correct absorption and enhancement effects, and a summary of the standard error of estimates are examined and discussed.The accuracy of the method is verified by the analysis of known standard reference materials such as obsidian rock, coal fly ash, argillaceous limestone and blastfurnace slag. The values are compared with the known certified values.