Proveniências no Neolítico: arqueometria em contextos geológicos distintos

O estudo de proveniências geológicas realizado em 3 áreas com contextos geológicos distintos - Lisboa, Freixo (Redondo) e Monforte, através da aplicação de diferentes metodologias e técnicas analíticas (DRX, ATG, FRX, ICP-MS, LA-ICP-MS, SEM-EDS, TIMS), permitiu verificar que a seleção dos esteios é condicionada pela diversidade e disponibilidade local dos materiais geológicos. O trabalho de campo desenvolvido a par com os dados obtidos (mineralógicos, petrográficos, geoquímicos, isotópicos) em amostras de antas e afloramentos indicam uma proveniência local para a generalidade dos esteios de antas das áreas de Lisboa e Freixo até 800m, aumentando esta distância (1000-1700m) na área de Monforte.

Archaeometric evidence for the authenticity of the Jehoash inscription tablet

A gray, fine-grained arkosic sandstone tablet bearing an inscription in ancient Hebrew from the First Temple Period contains a rich assemblage of particles accumulated in the covering patina. Two types of patina cover the tablet: a thin layer of black to orange iron-oxide-rich layer, a product of micro-biogenic processes, and a light beige patina that contains feldspars, carbonate, iron oxide, subangular quartz grains, carbon ash particles and gold globules (1 to 4 microns [1 micron = 0.001 millimeter] in diameter). The patina covers the rock surface as well as the engraved lettering grooves and blankets and thus post-dates the incised inscription as well as a crack that runs across the stone and several of the engraved letters. Radiocarbon analyses of the carbon particles in the patina yield a calibrated radiocarbon age of 2340 to 2150 Cal BP. The presence of microcolonial fungi and associated pitting in the patina indicates slow growth over many years. The occurrence of pure gold globules and carbon ash particles is evidence of a thermal event in close proximity to the tablet (above 1000 degrees Celsius). This study supports the antiquity of the patina, which in turn, strengthens the contention that the inscription is authentic.

Análise multielementar em peças de ouro antigo utilizando fluorescência de raios X por dispersão em energia

Os métodos de análise não destrutiva vêm sendo largamente empregados na área de Arqueometria. Estes métodos analisam artefatos históricos e obras de arte fornecendo informações da composição, das técnicas utilizadas e do local de manufatura da época. Assim, é possível fazer a datação, estabelecer a autenticidade e avaliar técnicas de conservação e restauração. A Fluorescência de Raios X por Dispersão de Energia (EDXRF) é um método que permite fazer análises quantitativas e qualitativas multielementares dos artefatos de forma não destrutiva. Neste estudo foram analisados artefatos compostos por ouro de diferentes épocas através da técnica de Fluorescência de Raios X por Dispersão em Energia (EDXRF). Dentre os artefatos, encontram-se brincos, pingentes, estatuetas e adornos de roupa cedidos pelo Instituto de Pesquisa Histórica e Arqueológica do Rio de Janeiro (IPHARJ). As análises foram realizadas através do sistema comercial ARTAX 200. Este sistema possui ânodo de Molibdênio. Foi utilizado um filtro de alumínio com 315 μm de espessura e foi operado em 40 kV, 250 μA com 300 s de aquisição. As concentrações de Cu, Au e Ag foram obtidas através da curva de calibração feita com padrões de ouro de 24k, 18k, 16k, 14k, 12k e 10k. Os resultados mostram que todas as peças contêm ligas metálicas e ouro em diferentes concentrações em sua composição. A partir das diferenças nas concentrações de ouro, foi possível classificar as peças quanto à pureza do ouro (quilatagem). Além disso, foi possível estimar a época em que estas peças foram manufaturadas a partir da comparação dos resultados encontrados com aqueles encontrados na literatura.

An R Library for Compositional Data Analysis in Archaeometry

Compositional data naturally arises from the scientific analysis of the chemical composition of archaeological material such as ceramic and glass artefacts. Data of this type can be explored using a variety of techniques, from standard multivariate methods such as principal components analysis and cluster analysis, to methods based upon the use of log-ratios. The general aim is to identify groups of chemically similar artefacts that could potentially be used to answer questions of provenance. This paper will demonstrate work in progress on the development of a documented library of methods, implemented using the statistical package R, for the analysis of compositional data. R is an open source package that makes available very powerful statistical facilities at no cost. We aim to show how, with the aid of statistical software such as R, traditional exploratory multivariate analysis can easily be used alongside, or in combination with, specialist techniques of compositional data analysis. The library has been developed from a core of basic R functionality, together with purpose-written routines arising from our own research (for example that reported at CoDaWork'03). In addition, we have included other appropriate publicly available techniques and libraries that have been implemented in R by other authors. Available functions range from standard multivariate techniques through to various approaches to log-ratio analysis and zero replacement. We also discuss and demonstrate a small selection of relatively new techniques that have hitherto been little-used in archaeometric applications involving compositional data. The application of the library to the analysis of data arising in archaeometry will be demonstrated; results from different analyses will be compared; and the utility of the various methods discussed

Compositional data analysis in archaeometry

We shall call an n × p data matrix fully-compositional if the rows sum to a constant, and sub-compositional if the variables are a subset of a fully-compositional data set1. Such data occur widely in archaeometry, where it is common to determine the chemical composition of ceramic, glass, metal or other artefacts using techniques such as neutron activation analysis (NAA), inductively coupled plasma spectroscopy (ICPS), X-ray fluorescence analysis (XRF) etc. Interest often centres on whether there are distinct chemical groups within the data and whether, for example, these can be associated with different origins or manufacturing technologies

Compositional data analysis of archaeological glass: problems and possible solutions

Presentation in CODAWORK'03, session 4: Applications to archeometry

Compositional analysis of archaeological glasses

At CoDaWork'03 we presented work on the analysis of archaeological glass composi- tional data. Such data typically consist of geochemical compositions involving 10-12 variables and approximates completely compositional data if the main component, sil- ica, is included. We suggested that what has been termed `crude' principal component analysis (PCA) of standardized data often identi ed interpretable pattern in the data more readily than analyses based on log-ratio transformed data (LRA). The funda- mental problem is that, in LRA, minor oxides with high relative variation, that may not be structure carrying, can dominate an analysis and obscure pattern associated with variables present at higher absolute levels. We investigate this further using sub- compositional data relating to archaeological glasses found on Israeli sites. A simple model for glass-making is that it is based on a `recipe' consisting of two `ingredients', sand and a source of soda. Our analysis focuses on the sub-composition of components associated with the sand source. A `crude' PCA of standardized data shows two clear compositional groups that can be interpreted in terms of di erent recipes being used at di erent periods, re ected in absolute di erences in the composition. LRA analysis can be undertaken either by normalizing the data or de ning a `residual'. In either case, after some `tuning', these groups are recovered. The results from the normalized LRA are di erently interpreted as showing that the source of sand used to make the glass di ered. These results are complementary. One relates to the recipe used. The other relates to the composition (and presumed sources) of one of the ingredients. It seems to be axiomatic in some expositions of LRA that statistical analysis of compositional data should focus on relative variation via the use of ratios. Our analysis suggests that absolute di erences can also be informative

Grain size analyses in tin-lead glazes based on 2d-sections

A problem in the archaeometric classification of Catalan Renaissance pottery is the fact, that the clay supply of the pottery workshops was centrally organized by guilds, and therefore usually all potters of a single production centre produced chemically similar ceramics. However, analysing the glazes of the ware usually a large number of inclusions in the glaze is found, which reveal technological differences between single workshops. These inclusions have been used by the potters in order to opacify the transparent glaze and to achieve a white background for further decoration. In order to distinguish different technological preparation procedures of the single workshops, at a Scanning Electron Microscope the chemical composition of those inclusions as well as their size in the two-dimensional cut is recorded. Based on the latter, a frequency distribution of the apparent diameters is estimated for each sample and type of inclusion. Following an approach by S.D. Wicksell (1925), it is principally possible to transform the distributions of the apparent 2D-diameters back to those of the true three-dimensional bodies. The applicability of this approach and its practical problems are examined using different ways of kernel density estimation and Monte-Carlo tests of the methodology. Finally, it is tested in how far the obtained frequency distributions can be used to classify the pottery

Revisiting the compositional data. Some fundamental questions and new prospects in Archaeometry and Archaeology

In this paper we examine the problem of compositional data from a different starting point. Chemical compositional data, as used in provenance studies on archaeological materials, will be approached from the measurement theory. The results will show, in a very intuitive way that chemical data can only be treated by using the approach developed for compositional data. It will be shown that compositional data analysis is a particular case in projective geometry, when the projective coordinates are in the positive orthant, and they have the properties of logarithmic interval metrics. Moreover, it will be shown that this approach can be extended to a very large number of applications, including shape analysis. This will be exemplified with a case study in architecture of Early Christian churches dated back to the 5th-7th centuries AD

Estudio de la extracción química del fe en madera arqueológica subacuatica tratada previamente con peg 4000

Debido a la gran cantidad de muestras arqueológicas impregnadas con PEG que se encuentran contaminadas por compuestos insolubles de hierro, se plantea la posible extracción y formación de complejos Fe-L (L=PBTC) y sus efectos en (i) la estructura de la matriz orgánica, (ii) la estructura y propiedades físicas del PEG y (iii) el comportamiento de la muestra en la etapa posterior de almacenamiento. El proyecto analiza la formación de compuestos químicos y posibles modificaciones estructurales en el proceso de extracción del hierro. Consiste en un estudio sistemático de un sistema químico y su influencia en los procesos de precipitación de Fe3+ en medio acuoso. El proyecto se fundamenta en: (1) desarrollar un proceso experimental de optimización para la extracción de las sales contaminantes y (2) encontrar las técnicas analíticas óptimas que permitan apreciar modificaciones estructurales de los diferentes sistemas. Se determina la cantidad de hierro extraído mediante A.A. Las interacciones entre PBTC y PEG se analizan por IR. Las modificaciones de determinadas propiedades físicas se determinan por DSC y las estructurales mediante SEM. En las condiciones termodinámicas óptimas se obtiene una extracción superficial del hierro (30-35%). La disolución del PEG origina modificaciones de la masa y el volumen de la muestra

What is this thing called Historical Archaeology?

Historical archaeology, in its narrow temporal sense -as an archaeology of the emergence and subsequent evolution of the Modern world- is steadily taking pace in Spanish academia. This paper aims at provoking a more robust debate through understanding how Spanish historical archaeology is placed in the international scene and some of its more relevant particularities. In so doing, the paper also stresses the strong links that have united historical and prehistorical archaeology since its inception, both in relation to the ontological, epistemological and methodological definition of the first as to the influence of socio-political issues in the latter. Such reflection is partly a situated reflection from prehistory as one of the paper’s authors has been a prehistorian for most of her professional life.

Nova variante de cerâmica decorada a “verde e manganês” em Évora

Évora revela, recentemente, noum espólio cerâmico bastante significativo e heterogéneo de cronologia medieval-islâmica. Neste espólio destaca-se uma tigela com uma técnica ornamental até agora nunca documentada na Península Ibérica. Ao expor e discutir os resultados do estudo estilístico e analítico efectuado sobre a peça, revelou-se a originalidade da técnica decorativa, caracterizada por uma cor de base castanho/castanho escuro sobre a qual está desenvolvida uma decoração em verde e branco. Este estudo pretende contribuir para um melhor conhecimento da cerâmica islâmica da Península Ibérica e, subsequentemente, do território português.

Technological characterization of molded islamic pottery from Iberian Peninsula

The thesis examines the technical aspects of unglazed molded ceramics from Mértola, in the context of Islamic archaeology of the Iberian Peninsula (Almohad period, end of 12th and the beginning of 13th century). Ceramics of the time period under discussion (12th – 13th century) are understudied, including in what concern to shaping and firing of ceramic vessels, the origin of raw materials used in ceramics and glazes, and decoration methods such as slip painting and/or colored glazes. Moreover, the use of archaeometry tools is rare. Along with providing a general picture of molded ceramic production in Mértola, this work provides a new dimension to the discipline of Islamic ceramic studies by the analytical tool used and demonstrating the importance of archaeological ceramics of the western peripheries to the understanding the production of ceramics and the transmission of knowledge and cultural traditions within the Islamic caliphate. The chemical and mineralogical characterization of 12th/13th century Almohad unglazed molded ware from Mértola was accomplished through multi – analytical approach combining SEM, Powder/uXRD and LA-ICP-MS methods. In this paper unglazed and glazed samples were analyzed but the attention was given to unglazed specimens, while the glazed samples were used for the comparison with the previous group in order to determine possible similarities or dissimilarities, thus providing enough data to discuss about technical aspects and potential provenance; Resumo: A tese debruça-se sobre os aspetos técnicos de cerâmica de molde não-vidrada de Mértola, no contexto da arqueologia islâmica da Península Ibérica (período Almóada, final de XII e início do século XIII). A cerâmica do período em discussão (séculos XII-XIII) é pouco estudada inclusive no que concerne ao fabrico e à cozedura, à de fonte de matérias-primas, na pasta ou nos esmaltes e aos métodos de decoração, como pintura, presença de engobes ou esmaltes. Além disso, o uso de ferramentas de Arqueometria é raro. Para fornecer uma visão geral da produção de cerâmica moldada em Mértola, este trabalho oferece uma nova dimensão para a disciplina de cerâmica islâmicas pelas ferramentas analíticas utilizadas. Demonstrando a importância da cerâmica arqueológica da periferia ocidental para a compreensão da produção cerâmica e a transmissão de conhecimentos e tradições culturais no califado islâmico. A caracterização mineralógica e química das cerâmicas de molde e não-vidrada, Almóada, dos séculos XII-XIII de Mértola foi realizada através de uma abordagem multi-analítica que combina métodos de SEM-EDS, uXRD e LA-ICP-MS. Neste trabalho, as cerâmicas vidradas e não-vidradas foram analisadas conjuntamente, dando mais atenção aos espécimes não vidrados. As amostras de cerâmicas vidradas foram utilizados para a comparação com o grupo anterior, a fim de determinar as possíveis semelhanças ou diferenças, proporcionando, assim, dados suficientes para discutir os aspetos técnicos e o potencial de proveniência das cerâmicas não vidradas