image/svg+xml31 IX/1/2018 InterdIscIplInarIa archaeologIca natural scIences In archaeology homepage: http://www.iansa.eu Archaeometric study of Roman tesserae from Salamanca (Spain). Archaeology and geochemical analysis Verónica Pérez de Dios a , Mª de los Reyes de Soto García b* , Isabel de Soto García c , Rosario García Giménez d a Department of Prehistory, Ancient History and Archaeology, Faculty of Geography and History, University of Salamanca, Calle de Serranos, 37008 Salamanca, Spain b Institute of Archaeology of Merida (IAM)-Spanish National Research Council- Junta de Extremadura- Plaza de España,15, 06800 Mérida (Badajoz), Spain c Department of Sciences, School of Agricultural Engineering, Public University of Navarre, Los Olivos Building, Campus Arrosadía, 31006 Pamplona, Spain d Departament of Geology and Geochemistry. Faculty of Science. Autonomous University of Madrid, Campus de Campoblanco C, Francisco Tomás y Valiente 7, Módulo 06, 28049 Madrid, Spain 1. Introduction The taste for decorative fooring is not a particular tradition of the Roman Empire: in fact we need to go back in time until Uruk’s period, at the Mesopotamian culture. The people of Uruk were the frst culture to beautify walls and columns with geometric mosaic-based terracotta cones of diferent shades, whose decorative function evinced the extravagance of the place and its owner (Rossi, 1971, pp. 6–34; Bertelli, 1988, pp. 9–44; Fiorentini, 2001, pp. 17–39; Palomar, 2011, p. 54). The musivaria technique has not only become clear in the archaeological remains but also in classical written sources – Vitruvius and Pliny and the Edict of Diocletian itself. Therefore, mosaics are one of the decorative elements used by the Romans to decorate their buildings. It consists of small pieces, called tesserae, whose combination following a model or set pattern were used to decorate pavement. The tesserae are usually cubic in shape and made of diferent materials such as marble, ceramic, stone or glass. The diferent types of colours and sizes allow them to create patterns – from the most simple to more elaborate – all of it can be observed for example in the large villas of the Roman Empire, such as the Roman villa of Casale in Sicily (Italy) or the Roman villa of Noheda in Cuenca (Spain).Traditionally in Spain, mosaic pavements have been studied from an iconographic point of view. However, there are only a few examples of studies of the characterization of tesserae mosaics (Palomar, 2011; Flores et al. , 2011; de Soto et al. , 2014). The last few years, the rise of multidisciplinary analysis has greatly increased interest in the realization of archaeometric studies, although these types of analysis were not very abundant in Spanish science and not implemented widely until the 1980s (Garcia, Olaetxea, 1992, p. 266). These studies, apart from their purely descriptive interest, were intended to identify the petrography, disclose manufacturing techniques of the tesserae, analyse the sources of supply of materials to thus make inferences about trade relations, and alleviate the problems of conservation of pavements Volume IX ● Issue 1/2018 ● Pages 31–42 *Corresponding author. E-mail: reyesdesoto@gmail.com ARTICLE INFO Article history Received: 17 th February 2017Accepted: 4 th June 2018 DOI: http://dx.doi.org/ 10.24916/iansa.2018.1.3 Keywords: tesseraeRoman villaSalamancageo-chemical analysis ABSTRACT In this study an analysis was made of 37 samples of tesserae of diferent shades and colours from Roman archaeological sites in the province of Salamanca (Spain), where pavements of opus tessellatum have been located. The tesserae were characterized by Mass Inductively Coupled Plasma Mass Spectrometry (ICP-MS), X-Ray Difraction (XRD) and Spectrometry, in order to determine their origin, composition and technique of manufacture. Results could reveal to us the local production of certain tesserae and the existence of a commercial network through the Via de la Plata and its main roads in the Iberian Peninsula.
image/svg+xmlIANSA 2018 ● IX/1 ● 31–42 Verónica Pérez de Dios, M a de los Reyes de Soto García, Isabel de Soto García, Rosario García Giménez: Archaeometric Study of Roman Tesserae from Salamanca (Spain). Archaeology and Geochemical Analysis 32 (Butzer, 1989, p. 153; James, 2006). In this sense, the main objective of our work is to analyse the petrographic origin of the tesserae from the diferent mosaics known so far in the province of Salamanca, to infer some historical conclusions, and corroborate the existence of certain trade routes linked to mosaic workshops. In this article we will study 37 tesserae samples of diferent colours from seven Roman sites in Salamanca (Spain): Los Villares -LV- (Fresno Alhándiga); Alquería de Azán -AZ- and Aldearrica -AL- (Miranda de Azán); San Julián de la Valmuza -SJ- (San Julián de la Valmuza); San Morales -SM- (Aceña de la Fuente); La Vega -LVE- (Villoruela); and Saelices -SA- (Saelices el Chico).The aim of this work is to study the origin, composition and the technique of manufacture of the tesserae in order to determine local production or the existence of a commercial route connecting mosaic workshops. The samples were analyzed using geochemical techniques such as Inductively Coupled Plasma Mass Spectrometry (ICP- MS) and X-Ray Difraction (XRD). Finally, the results were studied using statistical techniques. 2. Geographic context The Salamanca region is situated in central-western Spain. It is bordered to the north by Zamora and Valladolid, to the east by Ávila, to the south by Caceres and to the west by Portugal (Figure 1). The studied area is geologically situated within the Central Iberian Zone. It has an average altitude around 800 m but there are large variations throughout the province, upward to 2,428 m in the Sierra de Béjar and down to 116 m in the valley of the Salto de Saucelle. From a geographical point of view, the province of Salamanca is divided into three diferent areas (Lucena-Conde, García, 1976): The mountains: located in the south of the region. The altitude ranges between 1,000–2,500 m. Granites, quartzites and slates are present in this area. The soils are acid and siliceous-humid soils are abundant in the mountain areas.The high plateau: located in the centre of the region and in the W and NW. Slates and granites are abundant in this area and thus soils are siliceous.The Duero Basin: materials are sedimentary rocks such as conglomerates, sands, clays and limestone from the Tertiary era. The most productive soils of the Salamanca region are located in this area.Alongside these geographical features, the abundance of waterways and the likely environmental conditions became the central plateau in a favourable area for the proliferation of new settlements in Roman times. 3. Antecedents: Roman villae with mosaic pavements of the province of Salamanca (Spain) Although the urban development of the modern city of Salamanca began in the second half of the frst century AD, the evolution of the Roman rural settlement is unknown. However, we have one important archaeological fact, the creation of the Silver Way, a reference point next to the famous mansios and other rural settlements of various types with productive and residential functions (Roldán, 1971; Martín, Benet, Macarro, 1991; Salinas, 1998; Ariño, Díaz, 1999, pp. 153–192; Menéndez, 2000–2001; Chavarria, 2006, pp. 18–25). A recent archaeological survey carried out in the province has corroborated the existence of numerous agricultural and livestock establishments of the second order, and obviously larger settlements that may be classifed as villae, thanks to the ostentatious archaeological material recovered (Pérez, 2014; de Soto, 2015). Although in the Provincial Archaeological Inventory, most deposits of Roman chronology are identifed as villae , it is necessary to compare information based on ancient archaeological surveys. In order to determine which settlements could safely be ascribed to this category, we have analysed the databases in which it is recorded all the archaeological material from the Roman sites of Salamanca province. The aim was to locate certain ostentatious materials, such as mosaic pavements, in order to corroborate the existence of villae . The search results allowed us to catalogue seven sites with mosaics foors, six of them located in the valley of the Tormes River, and the last one placed on the riverside of the Agueda. 3.1 Mosaic pavements in the West: the village of Saelices Located in the municipality of Saelices el Chico and invading most of the current town, crops and column bases of Roman chronology were discovered when the foundation of a house was made in the 1980s. Subsequent archaeological excavation of the site brought to light several housing structures in which appeared a mosaic of about 13 m 2 with a geometric decoration that highlights Solomon’s knots that form three rows of square lattices of 48.5×48.5 cm in which various geometric motives, vegetable and chequered patterns are inserted. The pavement, very similar to the north gallery of the peristyle of the Roman villa of La Olmeda, used to be part of a corridor of the urban part of the villa (Chamoso, Hernandez, 1997; Chamoso, 2007). 3.2 Roman villas with mosaic pavements in the valley of the Tormes River In the municipality of Miranda de Azan, two settlements have been located with mosaic pavements: Alquería de Azán, the most relevant of these, and Aldearrica. The site of Alquería de Azán was frst recorded by Father César Morán, who documented slate graves and archaeological remains attributable to Roman times (Morán, 2000, p. 58). Later, in the 1980s, Benet and Santonja documented white, black and red tiles of a small size that corroborated the existence of at least one mosaic foor (Benet, Santonja, 1990, p. 286). Meanwhile, at the site of Aldearrica, cited by Morán and Maluquer, a scattering of Roman materials, including various tesserae, were found (Morán, 2000; Maluquer, 1956).North of Miranda de Azán, in the municipality of Doñinos, the frst fgurative mosaic of the province of Salamanca was
image/svg+xmlIANSA 2018 ● IX/1 ● 31–42 Verónica Pérez de Dios, M a de los Reyes de Soto García, Isabel de Soto García, Rosario García Giménez: Archaeometric Study of Roman Tesserae from Salamanca (Spain). Archaeology and Geochemical Analysis 33 discovered in 1801 at San Julián de la Valmuza Roman’s villa. The mosaic foor was published in 1832 by Cean Bermudez in “Summary of Roman Antiquities of Spain” (Cean Bermudez, 1832). In 1984–1985, the villa was partially excavated and a new pavement of opus signinum and opus tesselatum was found (Garcia, Serrano, 1996, pp. 35–38; Regueras, Pérez, 1997, pp. 17–19).On the other bank of the River Tormes, east of the city of Salamanca, remains of mosaic pavement were found at La Aceña de la Fuente, El Cenizal (San Morales) and La Vega (Villoria and Villoruela). The frst settlement has two distinct parts: a residential sector (La Aceña de la Fuente) and a necropolis in the sector where ashen spots are visible (El Cenizal) (Excar, 1991–1992). In the frst of these, Luis Angoso located numerous fragments of Roman pottery, metal elements, mosaic tiles and 16 fragments of slates with textual inscriptions and numerals. In 1985, a few kilometres from this site, between the municipalities of Villoria and Villoruela, a Roman villa called La Vega was discovered. In that year, García Figerola and Angoso conducted an archaeological excavation of 12×12 m in which were discovered three foors of opus tesselatum with a geometric decoration made up of small tesserae of diferent colours (white, black, red and yellow) and an important piece of a mural painting (García Figuerola, Angoso, 1986; Regeras, Pérez, 1997, pp. 51–60).In 2015, the archaeological survey undertaken in the south of the province by Pérez de Dios led to the discovery of a new Roman settlement with a mosaic foor, located in the present municipality of Fresno Alhándiga. The subsequent archaeological excavation revealed the existence of a large settlement next to the Silver Way, where was documented part of a thermal resort with three diferent rooms. The frst room contained a geometric mosaic foor with fsh and dolphins, while the other two rooms of smaller size had opus signinum and one hypocaustum in perfect condition of preservation (Pérez, de Soto, 2017). 4. Materials and methods A selection of 37 tesselatum samples from seven archaeological excavations in Salamanca (Spain) (Figure 1) have been studied in order to diagnose their origin. Tesserae have been sampled from diferent parts of the mosaics with the purpose of creating a colour representative sample set. However, in order to minimize the impact and considering the archaeological importance of the fnd, sampling has been limited to this number of samples.Mosaic tesserae are small parallelepipeds with an irregular structure that could be made of diferent kind of materials such as stone, marble, glass or pottery. Samples of red, green, white, cream and blue have been selected with a rectangular prism shape and average dimensions of 1.0×1.0×1.5 cm. In addition, blue and cream samples usually have conchoidal fractures. A summary description of each sample is included in Table 1. The colour of the samples was studied using the Munsell Soil Color Chart (Munsell, 1975).These samples were characterized according to their mineralogy and chemistry. In all cases, a minimal part of the sample was taken to minimize damage to archaeological objects. The samples were labelled “LV”, “AZ”, “SJ”, “AL”, “SM”, “LVE” and “SA”, to indicate the location of the archaeological site, followed by an identifcation number.