Obsidian source characterization in the Cordillera Real and eastern piedmont of the north Ecuadorian Andes

Recent research in the Quijos and Cosanga valleys of the eastern piedmont of Ecuador’s Cordillera Real has revealed and substantiated previous knowledge of obsidian sources that are unrelated to obsidian flow systems in the Sierra de Guamaní, Ecuador. Neutron Activation Analysis (NAA) and X-ray Fluorescence (XRF) were carried out on 47 obsidian source samples collected from several contexts in and adjacent to the study area. From samples within the study area three distinct obsidians were characterized: Cosanga A, Cosanga B, and Bermejo. These obsidians originate from a number of obsidian-bearing rhyolitic domes recently identified in the hills west of the Río Cosanga. Extensive survey of these dome localities has identified obsidian cobbles large enough for formal and informal tool manufacture. Beyond the study area, samples were collected and analyzed from the El Tablón source in the Sierra de Guamaní, providing much needed data on this poorly understood source. In addition, a sample from the newly identified Conda Dome source, near the Cotopaxi volcano, was characterized with XRF. All samples were then compared to 57 pre-existing samples from the Mullumica–Callejones, Yanaurco–Quiscatola and Carboncillo sources in the Ecuadoran Cordillera Real, as well as to artifacts from the Sumaco area in the Ecuadorian Amazon. Results of the elemental characterization indicate that the Cosanga Valley, El Tablón and Conda Dome obsidians are chemically distinct. Further, visual characteristics of Cosanga Valley obsidian types are useful in source attribution for the large artifact samples from the region. Finally, obsidian collected from the El Tablón flow suggests that this source may have produced obsidian suitable for tool manufacture.     

Making sense out of cents: compositional variations in European coins as a control model for archaeometallurgy

Archaeometallurgy frequently seeks to correlate between the temporal and spatial distribution of ancient metal objects and their chemical composition. In this study, we examined whether and to what extent local or temporal deviations in the content of modern artifacts can be identified as a proxy for archaeological material that is typically less controlled and therefore more difficult to cluster. For this purpose, Euro coins of 10, 20 and 50 cents from Germany, France, Spain, Italy and Belgium, which are made of copper (Cu) with 5% aluminum (Al), 5% zinc (Zn) and 1% tin (Sn), were analyzed using a simple XRF analyzer. The mass ratios Sn/Cu and Zn/Cu were measured with a relative precision c.a. of 5%. The mean content of the coins from each country was then determined for 20–39 of them. The difference of the mass ratio Sn/Cu observed – from 0.0101 to 0.0111. One coin from Luxemburg shows differences in various areas of its surface of up to a factor of 1.5. Thus, the results of this small pilot research show that even in modern metal artifacts we can detect differences in metal content, which can be correlated to their production and utilization places. Therefore, this study can serve as a model for evaluating compositional variations noted in archaeometallurgical studies where the standard deviations are greater and the differences can be linked more readily to spatial and temporal differences.     

Compositional Analyses of Mortars from the Late Antique Site of Son Peretó (Mallorca,Balearic Islands,Spain): Archaeological Implications

The paper presents the mineralogical, petrographic and chemical analyses of mortars from an Early Christian complex found in Mallorca (Balearic Islands) and dated to between the fifth and the eighth centuries ad . We characterized several mortars found at the site, in order to gather information on the raw materials used, as well as on the technology of production, and similarities among the samples. The analyses were aimed at solving specific archaeological questions regarding the building phases of the site and, in particular, the synchronic or diachronic presence of two baptismal basins in the same Christian complex.     

To Have and to Hold? Recent Research on the State of Preservation of the Roman Fort of Fectio (Municipality of Bunnik), the Netherlands

The transformation of the Roman fort of Fectio was seized upon to gain insight into the factors that determine the degradation of metal finds and the relationship with different forms of land use. The research showed no difference in the preservation of metal finds from different burial contexts, including disturbed contexts. A possible explanation for the good condition of the metal finds is the presence of organic waste and building material that, together with the clayey soil, create an ideal burial environment for non-ferrous metals.     

Geochemical composition of source obsidians from Kenya

Here we provide a reference resource to archaeologists interested in the sources of obsidian in Kenya, through electron microprobe analyses of 194 obsidian samples from 90 localities. Averaged analyses of each sample and eleven published analyses are categorized into 84 compositional groups of which only about 21 are known to have been used to produce artifacts, possibly because studies of artifactual material in the region are lacking. We also provide trace element analyses determined by XRF and LA-ICP-MS for these same obsidians. In northern Kenya 27 distinct compositions of obsidian have been found, including some of Miocene age, but the source of the most abundant obsidian found in archaeological sites in this part of Kenya remains obscure. The Baringo region contains at least 13 varieties of low-silica obsidian. The Naivasha–Nakuru region contains an abundance of obsidian with 38 compositional types recognized, and is the only region in Kenya apart from the Suregei (northern Kenya) that contains rhyolitic obsidian. Nine compositionally distinct types of obsidian are known from southern Kenya. Although Kenyan obsidians span the compositional range from phonolite to rhyolite, low-silica, nepheline-normative obsidians occur only south of 1°N latitude. One obsidian type, the Lukenya Hill Group, appears to have been derived from a regionally extensive ash flow tuff with a distribution of over 8000 km². From previous studies it is known that obsidians of lowest (Mundui) and highest iron content were used for tool manufacture, as were some obsidians (e.g., Kisanana) with the highest alkali content, and obsidians with both high (Njorowa) and low (Kisanana) silica content.     

New evidence of early use of artificial pozzolanic material in mortars

Hydraulic building composites, such as mortars and plasters, produced with artificial pozzolanic materials, became widely popular thanks to the Romans. Reports on earlier uses of such composites can also be found, mainly in archaeological and historic documents. These date back as far as the time of Minoan and Mycenaean civilizations. Here, we present a holistic analytical investigation of Late Bronze Age mortars from various archaeological sites of Cyprus. We focus on petrographic observations of thin sections, scanning electron microscopy and energy dispersive X-ray microanalyses and we investigate the microstructure and texture of the samples and the chemical composition and interface of their binders. Results of powder X-ray diffraction analyses are also presented, alongside a series of measurements using mercury intrusion porosimetry and vacuum saturation, aiming to estimate the pore size distribution and the physical properties (i.e. open porosity and bulk density) of the specimens under investigation. We also report on tests carried out to assess the drilling resistance of the mortars using a novel, portable system. The results thoroughly confirm, for the first time, the earliest intentional use of crushed brick as an artificial hydraulic additive in lime mortars in Cyprus, in order to enhance their performance and longevity in the absence of natural pozzolanas.     

Micro-XRF analysis of silver decorations on Archaic helmets from Olympia

Quantitative micro-X-ray fluorescence (XRF) analyses were performed on 19 silver decorations of six Archaic bronze helmets from the archaeological site of Olympia, Greece. The principal aim of the study was to investigate technological aspects of the smelting process that influence the composition of Ag, reveal possible elemental correlations and shed light on its source, assigning a likely provenance. The XRF results revealed that all decorations contain high amounts of Ag > 95%. The quantitative determination of several fingerprint minor elements, such as Au, Pb and Bi, provided interesting insights related to the efficiency of the cupellation process, the ore type used for the silver extraction and the geological origin of the ores.     

THE ANALYSIS OF DYESTUFFS FROM FIRST‐ TO SECOND‐CENTURY TEXTILE ARTEFACTS FOUND IN THE MARTRES‐DE‐VEYRE (FRANCE) EXCAVATIONS*

A series of Gallo‐Roman clothes and miscellaneous textile fragments from the first and second centuries from the Martres‐de‐Veyre necropolis (Puy‐de‐Dôme, France) was investigated. The objects studied were excavated between 1851 and 1923, during successive rounds of archaeological work. Since that time, they have been conserved in the Barguin Museum at Clermont‐Ferrand. The target of our research was dye identification, as it gives very interesting and useful information regarding the ancient technology. This approach has until now not been considered to be relevant and, unfortunately, is not systematic. The analysis was carried out by high‐performance liquid chromatography with photodiode array detection (HPLC–PDA). The small samples (threads up to 0.6 mg, less than 1 cm long) of coloured textile fibres were submitted to this technique. In one case, X‐ray fluorescence (XRF) analysis was applied. According to the analysis, the dyeing sources proposed are the Rubiaceae family for red, a luteolin ‘base’ for yellow, ellagitannins for brown and indigo for blue colours. Several samples did not seem to contain any dye. We point out possible factors for the partial dye source determination: instrumental limits, sample size, low dyestuff content in analysed samples and the dyes’ decomposition during ageing. Some improvements of dye analysis in archaeological samples by separation techniques based on recent analytical instrumentation and combined approaches are proposed.     

COOKING AND PAINTED WARE FROM SAN GIUSTO (LUCERA,FOGGIA): THE PRODUCTION CYCLE,FROM THE SUPPLY OF RAW MATERIALS TO THE COMMERCIALIZATION OF PRODUCTS*

Archaeological excavation at the San Giusto site (Lucera, Italy) has unearthed a Late Antique kiln that was most certainly dedicated to the production of cooking ware. An archaeometric study of numerous specimens of cooking and painted ware found at this site was carried out using optical microscopy, scanning electron microscopy, micro‐Raman spectroscopy, X‐ray diffraction, X‐ray fluorescence, inductively coupled plasma mass and optical emission spectrometry and instrumental neutron activation analysis. The integration of historical–archaeological data with archaeometric data has revealed that these specimens can be attributed to the San Giusto site. Furthermore, the production cycle of this ware can thus be reconstructed: from the diversified supply of raw materials (fluvial and marine sediments), to the relatively complex preparation of the paste, to firing at variable temperatures (600–750°C for cooking ware; 850–1050°C for painted ware).     

GEOCHEMICAL PROVENANCE OF OBSIDIAN ARTEFACTS FROM THE MSA SITE OF PORC EPIC,ETHIOPIA*

Obsidian geochemical analysis has become an indispensable tool in archaeological research and has wide applications. However, in spite of the abundance of geological and archaeological obsidian, there has been virtually no such investigation in Ethiopia. Recent instrumental characterization of 31 obsidian artefacts from the Middle Stone Age site of Porc Epic and numerous obsidian geological sources show that artefacts were being transported from as far as 250 km away. We believe this has relevance to the understanding of the emergence of modern human behaviour.