Carlos P. Odriozola

Non-Invasive Analytical Techniques Applied to Characterize the Components of Ancient Golden Medallions

BackgroundThe first stable material used to create a gilded surface was gold. False gold was also found in the form of copper-zinc powders or silver covered with resin. There are various ways to make gold leaf adhere to a large surface area. The identification of the materials and processes to make the gilding and the use of non- invasive techniques for gilding study is still an open problem. The gilding of the medallions from the Mudejar palace of Sevilla Alcazar was investigated, and their components were characterised using non-invasive (in situ and laboratory) techniques such as X-ray fluorescence, μ-Raman, infrared spectroscopy, X-ray diffraction and scanning electron microscopy coupled with energy dispersive X-rays. Cross-sections of golden support were also performed and studied by SEM-EDX.ResultsThe leaf adhered to the surface was primarily a gold alloy. However, copper, silver and zinc were also found. A layer of lead chromate with some lead sulphate was between the alloy and the support. This yellow pigment (lead chromate) and the layers of bole and white lead were characterised in cross-sections prepared from samples taken from the medallions in which the golden layer was missing. The support was composed of gypsum. Another golden layer applied in oldest time period was also found.ConclusionThe non-invasive techniques provided useful information about the characterisation of the components of the golden medallions. However, complete characterisation of the medallions required the use of other techniques such as mass spectrometry and scanning electron microscopy- energy dispersive X-ray. This is the first time that lead chromate has been detected in gildings. The external gilding was applied at the beginning of the 19th century using mordant oil (linseed oil).

A new approach to determine the geological provenance of variscite artifacts using the P/Al atomic ratios

The procurement and exchange of variscite was an important part of Iberian 4th-to-2nd millennia political economy. For decades, archaeologists have sought to chemically characterize variscite deposits. However, these studies have met with limited success due to intrinsic limitations of trace element analyses of compositionally complex minerals such as aluminophosphates. Previous works by the author bring about a new approach to variscite provenance based on P/Al atomic ratio (Odriozola et al., J Archaeol Sci 37(12):3146–3157, 2010b). The goal of this research is to develop a solid technique to track archaeological variscite artifacts procurement areas using energy-dispersive X-ray fluorescence spectrometry (EDX), supported by X-ray diffraction (XRD) mineralogical identification and refined by magic angle spinning-nuclear magnetic resonance (MAS-NMR) structural characterization. The MAS-NMR analysis of the local structure of aluminum and phosphorus in natural aluminophosphates, show that sources and beads have two crystallographic sites for phosphorus and one for aluminum supporting that some Iberian green aluminophosphates may be considered anionic framework aluminophosphate crystals where the presence of phosphate (Q4) and hydroxyl groups linked to phosphorus (Q3) as in H2PO4− anions make P/Al atomic ratio vary from unity. Therefore, the P/Al atomic ratio can be used to characterize variscite deposits, thus allowing us to link variscite artifacts to prehistoric mines. The method is tested for eight variscite mines successfully in defining provenance regions; and 19 artifacts analyzed from eight sites in Iberia fell into several distribution patterns of characterized source regions.

Amber, beads and social interaction in the Late Prehistory of the Iberian Peninsula: an update

The identification of archaeological amber has been used in Iberian prehistory to evidence long-distance exchanges and engage Iberia in networks that connect western Europe with central and northern Europe, the emergence of social complexity, and the consolidation of trade networks. However, until now, no comprehensive analytical study of the Iberian amber has been produced to support any of the interpretive models currently in use. This paper approaches the analysis of Iberian Peninsula amber artefacts by considering their provenance (based on FTIR characterization), chronology, and spatial relationship with other exotica. Our work increases the number of analyzed artefacts to 156 (24%), out of the c. 647 currently known for the Iberian Peninsula. Based on these new data and a review of Murillo-Barroso and Martinón-Torres (2012), this overview outlines amber consumption patterns from the 6th to 2nd millennia BCE and demonstrates long-distance amber exchange connecting Iberia with the Mediterranean region from the Neolithic period onwards.

Middle Guadiana River Basin (Badajoz, Spain and Alentejo, Portugal) Network Interactions: Insights from the Chemical Analysis of Bell Beaker Pottery and the Lead Isotope Analysis of Copper Items from the Third Millennium BC

Several settlement networks from the Iberian Copper Age period are located alongside the Guadiana River (Iberian Peninsula) – i.e. Perdigoes, Reguengos de Monsaraz, Portugal (Dias et al.2005; Valera 2006), or Tierra de Barros, Badajoz, Spain (Hurtado 1995,1999). In this context, a clear relation has been found between the sites in terms of spatial organization (hierarchical, where La Pijotilla could be considered as a central place in a core-periphery system), a restricted stylistic distribution of the so-called Guadiana ‘eyed idol’ figurines (Hurtado 2008), or the distribution of bone based inlayed Bell Beaker pottery (Hurtado and Odriozola 2008; Odriozola in press).

Pre-Solutrean rock art in southernmost Europe: Evidence from Las Ventanas Cave (Andalusia, Spain)

The south of Iberia conserves an important group of Palaeolithic rock art sites. The graphisms have been mostly attributed to the Solutrean and Magdalenian periods, while the possibility that older remains exist has provoked extensive debate. This circumstance has been linked to both the cited periods, until recently, due to the transition from the Middle to Upper Palaeolithic in the extreme southwest of Europe as well as the non-existence of some of the early periods of Palaeolithic art documented in northern Iberia. This study presents the results of interdisciplinary research conducted in Las Ventanas Cave. These results enabled us to identify a new Palaeolithic rock art site. The technical, stylistic and temporal traits point to certain similarities with the range of exterior deep engravings in Cantabrian Palaeolithic rock art. Ventanas appears to corroborate the age attributed to those kinds of graphic expression and points to the early arrival of the Upper Palaeolithic in the south of Iberia. Importantly, the results provide information on the pre-Solutrean date attributed to trilinear hind figures. These findings challenge the supposed Neanderthal survival idea at one of the main late Middle Palaeolithic southern Iberian sites (Carigüela) and, due to the parallels between them and an engraving attributed to this period in Gibraltar, it raises the possibility of interaction between modern humans and Neanderthals in the extreme southwest of Europe.

Circulación de hachas prehistóricas de jade alpino en el centro-occidente de la Península Ibérica. ¿Modelo “directional trade” o “down-the-line/prestige chain”?

espanolEn este articulo se pretende 1) actualizar la base documental de hachas de jade ibericas exponiendo los resultados de la caracterizacion de cinco hachas procedentes de la Meseta Norte Espanola (espectroscopia Raman y UV-VIS-NIR) y 2) contrastar la hipotesis sobre el intercambio direccional entre Bretana (hachas repulidas de jade) y el Occidente de la Peninsula Iberica (adornos de variscita) durante el V y IV milenios a.C Los analisis arqueometricos apuntan a un origen alpino de las hachas en estudio. Sin embargo, distintos argumentos arqueologicos –que incluyen aspectos tipologicos y cronologicos de la distribucion de hachas, adornos de variscita y otros artefactos– asi como un analisis estadistico de correlacion espacial entre la distribucion de las hachas de jade y minas y adornos de variscita, nos facultan a rechazar dicha hipotesis: no consideramos que haya existido un intercambio directo de hachas de jade bretonas por adornos de variscita del occidente peninsular sino, mas bien, una distribucion de tipo “down-the-line/prestige chain”. EnglishThe focus of this paper is to update the Iberian jade axe database with new unpublished data and the archaeometric characterisation (Raman and UV-VIS-NIR spectroscopy) of five jade axes of the Spanish Northern Meseta. This data will be used to test the hypothesis published by other authors which suggests that during the 5th and 4th millennia BCE there was a directional exchange of sociotechnic artefacts between Brittany, France (repolished alpine jade axes), and the Western Iberian Peninsula (ornaments of variscite mined in Zamora and Huelva). Archaeometric data shows a supra-peninsular exchange for axes based on the alpine origin of the jade. Besides this, previously untangled archaeological questions such as 1) Breton and Western Iberian jade axes and variscite ornaments typologies 2) exchange dynamics of other sociotechnic artefacts in Central Iberia and 3) the correlation of the distribution of jade axes, variscite sources and variscite beads, are analysed together. In our opinion, the data available suggest that, instead of a “directional trade” exchange, green sociotechnic objects –jade and variscite- reflect a decentralised “down-the-line/prestige chain” model. EuskaraArtikulu honen helburua da: 1) jade-aizkora iberiarren dokumentu-basea eguneratzea, Espainia Iparraldeko Goi-ordokiko bost aizkoraren ezaugarrien emaitzak azalduz (Raman espektroskopia eta UV-VIS-NIR) eta 2) K.a. V eta IV. milurtekoetan Bretainiaren (jade-aizkora txukunduak) eta Iberiar Penintsulako Mendebaldearen (bariszitazko apaingarriak) arteko norabide-trukeari buruzko hipotesiak alderatzea. Azterketa arkeometrikoen arabera, aztertutako aizkorek jatorri alpetarra dute. Baina zenbait argudio arkeologiko (horien artean aizkoren banaketaren alderdi tipologikoak eta kronologikoak, bariszitazko apaingarriak eta beste gailu batzuk) eta jade-aizkoren eta meatzeen eta bariszitazko apaingarrien banaketaren arteko korrelazio espazialaren azterketa estatistikoak hipotesi hori baztertzera garamatzate. Ez dugu uste zuzeneko trukerik izan denik Bretainiako jade-aizkoren eta penintsulako mendebaldeko bariszitazko apaingarrien artean, baizik eta “down-the-line/prestige chain” motako banaketa bat.