Vitrified Walls in the Iron Age of Western Iberia: New Research from an Archaeometric Perspective

European Journal of Archaeology 22 (2) 2019, 185–209

1 2 1 LUIS BERROCAL-RANGEL ,ROSARIO GARCÍA-GIMÉNEZ ,LUCÍA RUANO 2 AND RAQUEL VIGIL DE LA VILLA 1Department of Prehistory and Archaeology, Universidad Autónoma de Madrid, Spain 2Department of Geology and Geochemistry, Universidad Autónoma de Madrid, Spain

The phenomenon of Iron Age vitrified ramparts has become increasingly recognisable in the last twenty years in the Iberian Peninsula. After the first walls with vitrified stones were discovered in southern Portugal, there have been several findings scattered throughout western Iberia. A chronological sequence from the Late Bronze Age to the Late Iron Age can be established on the basis of the archaeological remains, with reference to different historical and functional conditions. This article reviews the data obtained from the various sites, in order to understand the context in which the stone structures became vitrified. Furthermore, we have analysed samples of stones and mud bricks that have been altered by fire from these sites, which has allowed us to explain the variability in the archaeological record in relation to different historical processes. With all these data, we aim to contribute to our knowledge of a phenomenon that is widespread in Iron Age Europe.

Keywords: vitrification, Iberian Peninsula, archaeometry, ramparts, hillforts, fortifications

INTRODUCTION eighteenth century, the first scientific studies were those of Vere Gordon Childe Throughout the twentieth century, an and Wallace Thorneycroft, whose explana- important number of calcined or vitrified tions related to a strong fire on timber- stones have been documented in ramparts laced walls. They claimed that these fires of protohistoric settlements in Europe. The had temperatures high enough to melt the phenomenon has been widely studied, stone, which would entail a violent given its extensive spread throughout Iron destruction of these settlements (Childe & Age Europe. Causes and possible purposes Thorneycroft, 1938: 55). have been a subject of debate, and often This hypothesis was refuted by other uncertain or inappropriate ideas are used to researchers, who pointed out that the tem- explain it; this has made it difficult to perature needed to melt the stone could understand how and why these stones were not be the result of a simple fire. altered (Youngblood et al., 1978; Scandinavian researchers proposed that Buchsenschutz & Ralston, 1981; Kresten vitrification was instead related to building et al., 1993; Cook et al., 2016). processes. Having analysed data from the Although the first evidence of vitrified Viking village of Broborg, they concluded stones was recorded as early as the that it would have been a gradual and

© European Association of Archaeologists 2018 doi:10.1017/eaa.2018.69 Manuscript received 25 March 2018, accepted 17 September 2018, revised 8 August 2018 Downloaded from https://www.cambridge.org/core. IP address: 2.138.103.252, on 12 Apr 2019 at 17:31:12, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/eaa.2018.69 186 European Journal of Archaeology 22 (2) 2019

intentional process intended to strengthen façade, from northern Scotland to south- the ramparts (Kresten & Ambrosiani, ern France. The war-like character of 1992: 1; Sjöblom et al., 2016). these people is attested by the best collec- In 1980, Professor Ian Ralston repli- tion of warrior stelae that exist; they come cated the vitrification of a timber-laced from this region and this time of change. wall near Aberdeen (Scotland, UK), and These stelae, and the contemporary early his results showed that this process would hillforts (such as Ratinhos or Passo Alto have caused the collapse of the walls, and in eastern Portugal), show Atlantic soci- hence would not have been an effective eties that were opening progressively to improvement in building techniques. Mediterranean taste: weapons, jewellery, Furthermore, it would be very difficult to and tools were changing from Atlantic produce and control such a fire. He con- and northern patterns to eastern cluded that this phenomenon must be Mediterranean models (Harrison, 2004). related to a deliberate destruction of ram- By the end of the eighth century BC, the parts, alongside the abandonment of their first Phoenician colony at Gadir (Cádiz) settlement (Ralston, 1986; 2006). This bears witness to an indigenous western explanation is a new approach, where vitri- cultural complex known as the mythical fication is considered to be a ritual conse- Tartessian kingdom, whose influences quence, as has been suggested for soon grew in Atlantic Europe, more Bernstorf in Bavaria (Germany) (Bähr through commerce and exchange than et al., 2012; Röpke & Dietl 2014). invasions and conquest. Since then, many cases of vitrified forts, But such change did not take place sud- dated from the Late Bronze Age to Early denly, or peacefully. Stratigraphic records, Medieval times have been recorded like those of the hillfort of Ratinhos, show throughout western Europe (Figure 1). that the local warrior societies reacted to Since it appears that these cases are the new system (Berrocal-Rangel & Silva, similar events with different causes, we 2010). They lived in small forts of less analysed several examples of vitrified, red- than a hectare, defended by simple sloping dened or calcined stones from walls ramparts and ditches, and the households belonging to Late Bronze Age and Iron within them consisted of round houses. In Age settlements of Iberia, with the aim of relation to these ramparts, the first ‘vitri- contributing to a better understanding of fied’ walls in Iberia were recognized in a this process in protohistoric Europe. context of destruction and abandonment. By around 500 BC, the Tartessian ‘kingdom’ wasoverandCelticpeoplesfrom THE IRON AGE IN WESTERN IBERIA: northern Spain invaded western Iberia on a TIME FOR A CHANGE massive scale (Berrocal-Rangel, 1992). Large, hierarchically organized hillforts Until the end of the ninth century BC, the emerged; some of them were called oppida, west of the Iberian Peninsula was a terri- such as La Mesa de Miranda in the Sierra tory integrated into the so-called Atlantic de Ávila in central Spain, thought to belong Bronze System and flourishing exchange to the Vettones people (Álvarez-Sanchís, with the Mediterranean civilisations 2000). Significantly, the Tartessian build- (Almagro-Gorbea, 2014). People in ings were burnt before they were abandoned western Iberia shared customs, beliefs, and (Celestino & López-Ruiz, 2016: 235), probably some kind of Indo-European although the use of mud bricks as a building language with a large part of the Atlantic material did not lead to vitrification.

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Figure 1. Vitrified forts in Europe: burnt ramparts from Middle Bronze Age to the Early Middle Ages. Main groups and sites: 1: Moidart-Morar; 2: Lochaber; 3: Inverness; 4: Strathdon; 5: Clyde; 6: Dumfries and Galloway 7: Wincobank; 8: Mayenne; 9: Vienne; 10: Corrèze; 11: Côte d’Or; 12: Meurthe-et-Moselle; 13: Cantal; 14: Loire; 15: Sado-Mira; 16: Saxony; 17: Bukowetz; 18: Hjälmaren Lake; 19: Hesse (Baitinger & Kresten, 2012; Clark et al., 2016; Comte, 2015; Cook, 20136; Friend et al., 2007; Grunwald, 2012; Kresten & Ambrosiani, 1992; Marcille, 1999;O’Brien et al., 2018; Ralston, 1992, 2006; Vilhena & Golçalves, 2012; Wadsworth et al., 2015, 2017).

In the later Iron Age, the vitrified ram- The Romans advanced towards the parts reappeared on sites that were con- Atlantic territory of Hispania, colliding quered by the Romans during the second with the Lusitanian people. This advance century BC. When the Carthaginians were was the cause of the Lusitanian wars, a defeated in the Second Punic War series of resistance conflicts between indi- (Curchin, 2014), Rome focused its imper- genous peoples and the Roman legions ial interests on the wealthy west of Iberia. from 194 to 59 BC (Dobson, 2008).

These conflicts left archaeological traces Spain, as well as Sabugal Velho and other in hillforts or oppida, but evidence of war settlements in the Odemira region in in the middle of the first century BC in southern Portugal (Vilhena & Gonçalves, this territory may also be related to the 2012). Although they do not form a very Roman Civil wars, between 80 and 76 BC large group of sites, they are spread over a and 49 and 45 BC. great area of the western side of the How advances in the building techni- Iberian Peninsula (Figure 2, no. 1). ques used by the Tartessians changed the All sites are located between the lower simple Late Bronze Age walls and how basins of the Guadiana and Douro rivers, timber-laced construction was introduced a land of plentiful oak forests. Although a during the Iron Age are questions that can substantial proportion of the material be answered by analysing cases of vitrified record comes from extensive surveys, stra- walls. tigraphy and radiocarbon samples allow us to argue in favour of the proposed dates, i.e. from the Late Bronze Age to the first VITRIFIED WALLS IN CELTIC IBERIA Roman presence in the area. Our findings belong to different historical contexts and The first vitrified wall to be identified in different purposes, and this picture is the Iberian Peninsula, at Castelos de becoming more complex as research Monte Novo in Portugal, was found by a progresses. British-Portuguese team of the Évora Archaeological Survey Project during the mid-1980s. Colin Burgess, Catriona Gibson, and Virgilio Correia recognized FIRES AT WAR:VITRIFIED RAMPARTS AS this surprising trait on the masonry wall of A TESTIMONY OF ARMED CONFLICTS? the Iron Age settlement of Castelos de Monte Novo in the Évora region, a Celtic None of the known cases is clearly related territory during the Iron Age (Correia, to an armed conflict, according to their 1995: 251–53). The discovery was later remains. Testimonies of war are an excep- confirmed by Ian Ralston (Burgess et al., tion in the archaeological record of Iberian 1999). protohistory. Weapons are usually found Some years later, a distinguished as offerings, funerary belongings, or Portuguese archaeometrist, António without known context; hence, if we Monge Soares, identified vitrified stones propose war-related causes for vitrification, in a small hillfort near the Spanish- we should look for other signs. Portuguese border, at Passo Alto (Soares, Ratinhos (Moura, Portugal) is the best- 1988; Soares et al., 2012). Since then, known example of possible armed conflicts several sites with similar evidence have (Figure 2, no. 3). The site is a fortified been identified in central Spain and settlement occupied from the Late Bronze Portugal; they include the Castro de Age to the beginning of the Early Iron Ratinhos, excavated by the authors of this Age (Silva et al., 2013; Berrocal-Rangel & article, or the doubtful case of the Volcán Silva, 2010: 420; Soares & Martins, del Gasco (Díaz-Martínez & Ormö, a place where there are no signs of archaeological 1 2003) in the Extremadura in western remains. According to the elders of the nearby village of El Gasco, the name of the site, el Pico del Castillo (Castle Peak), must refer to the shape of the slate out- 1 Our recent archaeological survey of this site, in May crops, reminiscent of crenulations. No ancient remains 2018, showed a massive occurrence of vitrified stones in have ever been found during farming activities.

Figure 2. Archaeological sites with vitrified walls in the Iberian Peninsula. 1: Distribution (black circles: Late Bronze Age Early Iron Age; white circles: Late Iron Age). 2: Plans of the sites studied, at the same scale.

2010), located on a major hill on the complex system of walls and ditches was banks of the Guadiana river, at an import- built from the twelfth to the ninth centur- ant natural crossroads. A Late Bronze Age ies BC, and a large area of the surrounding

territory could be controlled visually from slag or crucibles. We therefore proposed its summit. Probably because of that, an explanation in connection with vitrified Ratinhos was chosen as the site of the walls, which was taken up by Monge oldest oriental shrine known in Iberia Soares himself (Berrocal-Rangel, 2003: (with close parallels in Syria and Jordan), 216‒218; Soares et al., 2012). dated to around the second half of Thanks to his research, we also know the ninth century BC, at the same time of other examples. In Azenha da as the first Phoenicians reached the Misericordia (Serpa, Portugal), a good Mediterranean shores. Along with the archaeometric analysis has been conducted shrine, new ramparts were built, both with on a stretch of a wall with vitrified stones a timber-laced framework―a real innov- (Catanzariti et al., 2008). Again, this wall ation in this period. According to radio- bars the easiest access route to the settle- carbon data and stratigraphy, this new ment. Although Soares related that fact to phase at Ratinhos did not last very long. the presence of Bronze Age furnaces and Around 760 BC, the shrine was aban- metallurgical activities (Soares, 1988; doned, and the main entrance of the Catanzariti et al., 2008: 1401), nothing defensive wall shows signs of a fire, with proves that the unexcavated wall dates to vitrified stones and pieces of burnt clay prehistoric times. It is only the pottery col- (Silva et al., 2013). lected on the surface that suggests a date The site of Passo Alto (Moura, ranging from the Late Bronze Age to the Portugal) is more difficult to understand end of the Later Iron Age, while an arch- because of the limited extent of the exca- aeomagnetic analysis gave two possible vations (Figure 2, no. 2). Nevertheless, dates, 842–652 BC and AD 725–1034 António Monge Soares has been able to (Catanzariti et al., 2008: 1405). Judging obtain good results in archaeometry, by the pottery, Catanzariti and colleagues including geochemistry and radiocarbon took the first of these two periods as the dating (Soares, 1988; Soares et al., 2012). more likely (Catanzariti et al., 2008: Passo Alto is a fortified site occupied from 1506). the Late Bronze Age to the Iron Age, A similar situation existed at Castelos well-known by its upright stone row de Monte Novo (Évora, Portugal), the defences (‘chevaux-de-frise’). Occupying a settlement where vitrification was found surface of three hectares, the settlement is for the first time (Correia, 1995; Burgess naturally very well protected by the ravines et al., 1999). Much pottery was recovered of two small rivers, which converge in a on the surface at Castelos de Monte fork under the southern slope. However, Novo, which dates the site to the Late this type of settlement is usually character- Iron Age (Figure 2, no. 1). Deep and ized by having a very exposed access in the wide ditches are easily visible in front of a tongue of land between the ravines. Hence tall bank, which closes the only accessible large defensive works were built in this side to the interior of the village, to the area, and a wall, 3 m wide and 250 m north. Vitrified stones of medium size long, blocked access on this side (Soares, were found over the bank, over a stretch 1988: 90). There was a, yet unlocated, of more than 300 m. In addition, mud gate, even though a large quantity of vitri- bricks with clear signs of having been fied masonry has been found. At first, exposed to a fire were found. We therefore Monge Soares related the remains of vitri- infer that the rampart was built with a fication to smelting furnaces, but there masonry foundation and a mud brick and was no evidence to support this, such as timber-laced wall, and that both were

burnt (Berrocal-Rangel & Moret, 2007: of a deliberate building technique. 24–26). Vitrification could be related to an unfin- As we can see, Early Iron Age sites ished wall, built to reinforce its founda- such as Ratinhos, Passo Alto, and perhaps tions, because there is no charcoal or wood Azenha have vitrified walls over a specific among the stones and they were burnt in a stretch, whereas sites of the Late Iron Age slow fire in a reducing atmosphere. show vitrified stones over a long stretch of Nevertheless, it seems that this explan- walling, if not over the whole rampart, as ation does not convince the authors, who at Monte Novo, Sabugal Velho, and, prefer to follow the anthropologist Roland probably, at the newly-identified site of Comte and look for a symbolic purpose Fraga de Romualdo (Osório & Pernadas, (Comte, 2015). They speculate about the 2011; Pérez Macías, 2010: 282) (Figure 2, colours produced in the vitrification nos. 5 and 10). In both situations, an acci- process, which vary between pink, green, dental or deliberate fire related to armed blue, or violet, especially the ‘milky’ conflicts could be the most plausible quartz, which is used for obtaining copper explanation. minerals (Vilhena & Gonçalves, 2012: 543). However, Comte’s source is Jean Markale (1969: 180, 276) and his inter- FIRES UNDER BUILDINGS:VITRIFIED pretations of the glass castles found in RAMPARTS AS A TECHNICAL RESOURCE? Arthurian romances. Anyway, scientific evidence that has provides other explana- A recent article by Vilhena and Gonçalves tions, such as the addition of phosphor- (2012) contributes new evidence from the ous-bearing material, for example in region of Odemira in southern Portugal Scotland (Friend et al., 2007: 1701). which includes a study of settlements Ritual or aesthetic meanings may be where vitrification is probably related to attributed to examples from southern possible foundation structures. Portugal such as Castro de Garvâo This is the case with Cerro das (Ourique), a site with a spectacular votive Alminhas (Odemira, Portugal), a small deposit of the Later Iron Age (Figure 2. village of 0.5 ha, which yielded pottery no. 8; Vilhena & Gonçalves, 2012: 526). sherds from the Bronze Age to the Iron A well-built structure with vitrified Age and which, probably, had no defen- squared blocks was found on this site at a sive wall (Figure 2, no. 6). An artificial depth of two metres. Another nearby site, terrace was found, closing access to the Nossa Senhora da Cola (Ourique), has whole settlement. This terrace was strong ritual associations and a similar retained by local greywackes, some of context: many vitrified greywackes were them calcined, and it leads to some kind found in the centre of the fortified area, of floor and an undefined circular structure near the river Mira, where a splendid Late (Vilhena & Gonçalves, 2012: 532–33). Bronze Age sword was found (Vilhena & The interpretation of these remains is Gonçalves, 2012: 526). uncertain, but the site plan seems to indicate that the vitrified remains form part of an access to the settlement (Vilhena & FIRES IN NATURE:VITRIFIED STONES AS Gonçalves, 2012: fig. 12). As the vitrified BUILDING MATERIAL? stones appear to be regularly arranged, Vilhena & Gonçalves (2012: 533–540) There are other, less easily explained inferred that these remains are indicative examples, such as the site of the so-called

Volcán del Gasco (Las Hurdes, POZO DE LOS MOROS (VILLASRUBIAS, Extremadura, Spain). This geological site SALAMANCA,SPAIN) was discovered in the middle of the twentieth century, when it was identified as a We collected twenty samples of vitrified little volcano (García de Figerola, 1953). slates from Pozo de los Moros, measuring Fifty years later, it was redefined as the between 10 and 25 cm each, some being site of a meteorite impact, a theory that conglomerates with earth and slates was rejected by the same authors some aligned in several bedding planes, showing years later (Díaz-Martínez et al., 2001). different degrees of fire intensity. They Recent research suggests that it was a vit- were only found along the main access in rified fort (Díaz-Martínez & Ormö, the western corner of the site, where there 2003). In 2003, we identified some sherds is a short stretch of an old track for four- as protohistoric pottery that these geolo- wheeled vehicles (Figure 3). Visibility and gists had submitted to us but we do not slope maps, using ArcGIS over a LiDAR know where these fragments were Digital Terrain Model, show that this is collected. the easiest access route (Figure 4). In add- A few kilometres to the north, there is a ition, this area has a terraced shape, and ‘twin’ site, first thought to be the result of large stones and slate outcrops suggest a meteorite impact and later identified as a that they could belong to a wall or a vitrified hillfort by the same authors. This bastion, and pottery fragments indicate site is El Pico del Pozo de los Moros, that the site was occupied in protohistoric near the small village of Villasrubias times. (Salamanca, Spain) (Figure 2, no. 9). It is We identified the mineral composition located on a peak of 1218 m asl and over- of the samples by X-Ray Diffraction looks an area extending over several kilo- (XRD), using a SIEMENS D5000 instru- metres. Slate outcrops delimit the ment with a Cu anode, operating at 30 elongated summit with a natural wall, mA and 40 kV, using divergence and leaving a narrow area for settlement. reception slices of 2 mm and 0.6 mm Recently, we carried out intensive surveys respectively (Figure 5). We used the to confirm the archaeological character of powder method for the bulk samples and thesiteandcollectedasubstantial the oriented slides method for the <2 µm number of pottery fragments, vitrified fraction. The XRD profiles were measured slates and oral testimonies concerning the in 0.04 2θ goniometer steps for 3 seconds. ruins that were destroyed in the 1950s, The method consists of comparing a when a forest ranger station was built on sample of slate from an outcrop on the the summit. Pottery is mainly hand- summit without fire marks (sample made,andappearstodatetotheLate PZ008) to vitrified samples from the outer BronzeAgeandEarlyIronAge.Wedid edge of the terrace, looking for the pres- not find any traces of walls, and hence it ence or absence of minerals and using is possible that the vitrified stones had a them as geothermometers. When the rock geological origin and were later used as showed two different structures, usually building material. with two different colours, we took We therefore decided to use geochem- samples from both zones. The vitrified ical analysis in combination with spatial earth between the rocks of sample PZ001 studies, including LiDAR images, to was also analysed. achieve a better understanding of the site PZ008 is a protolith material from the of Pozo de los Moros. eastern outcrop of the site with a silicate

Figure 3. Pozo de los Moros de Villasrubias (Salamanca, Spain). 1: Plan showing the location of vitrified stones and archaeological finds of pottery. 2: LiDAR image (Instituto Geográfico Nacional de España).

composition made of chlorite (14.05 Å), By contrast, PZ001 has a grey core illite (8.90 Å), phyllosilicates (4,45 Å), (sample 1) made of pumice, with a high quartz (3.33 Å), and K-feldspar (3.18 Å). vesicular textured glass, where only quartz

Figure 4. Pozo de los Moros de Villasrubias (Salamanca, Spain). 1: Slope map; the darkest tones correspond to slopes of less than 9 per cent. 2: Visual control from the top of the site, distance of 250 and 2500 m radius (both calculated with ESRI ArcGIS 10.2).

was identified. This suggests that it was small quantity of maghmenite, but the burnt at a temperature of over 1200° absence of phyllosilicates and K-feldspars C. Its orange surface (sample 2) has a indicates a combustion temperature

Figure 5. Pozo de los Moros de Villasrubias (Salamanca, Spain): 1: Main entrance from the north- west. The arrows indicate where the vitrified stones were collected. 2: Vitrified stones and protolithic rock analysed with X-Ray Diffraction (XRD), with results shown in a diffractogram.

between 1000° C and 1100° C. The same core (sample 4) and surface (sample 5) of results as sample 2 were obtained for the the PZ002. As for PZ005, it retains K- sample of earth (sample 3), and from the feldspars, which indicates that fire

exceeded 800° C but did not reach 1000° and quartzite stones. Between them, two C. Therefore, as silicate rocks can become large postholes were found, containing vitrified from 850° C (Nisbet, 1982: 29), small wedges of slate and charcoal flecks we deduce that all these rocks were vitri- (Figure 6, no. 2, A1 and A2). Over and fied and, given the slight presence of inside these layers we recovered ‘vitrified’ maghmenite, we can assume that combus- stones and pieces of fired clay, the latter tion was reduced (Kresten & Ambrosiani, retaining the shape of the joists, as clay 1992: 3). It is important to remember that was used as plaster for the timber frame- no traces of metals such as aluminium or work (Figure 7). We deduce from this copper were found, as is usual in melting that the posts formed the central axis of furnaces (Friend et al., 2007: 1699). an internal wooden framework, resembling The range of temperatures between that used in the shrine found on the same 800° C to 1200° C could be related to an site both are techniques that were irregular (accidental or deliberate) fire, but unknown before. not a controlled fire, as would be expected The spread of the remains uncovered if stones were set on fire for a technical or to the south-east of posthole A2 reflects ritual purpose (Clark et al., 2016: 252). the direction of the fall of the burnt post. Therefore, in view of the location of the Larger stones were found on the opposite vitrified rocks and the range of tempera- side,overtheouterslope;theyhada tures at Pozo de los Moros, we suggest glossy patina and a light reddish colour that a fire was lit over a timber construc- on the surface only, unlike the natural tion, possibly the settlement’s main gate. grey-greenish colour of the slates. This It is clear that these vitrified stones were was, however, not a general event that not the product of a natural event, such as affectedtheentirewall.Thevarietyof the impact of a meteorite, and that they effects, in the form of calcined, reddened were not used as vitrified raw material for and vitrified stones, together with the building. spread of ash and charcoal layers and the fired clay pieces, provides evidence of a single fire, located at the easiest point of CASTRO DOS RATINHOS (MOURA, access to the acropolis, perhaps where SOUTHERN PORTUGAL) the main gate was located. In a nearby dwelling (or ‘hut’), P21, a burnt fragment Castro dos Ratinhos is one of the few of a white pine prismatic beam measur- excavated sites that has provided ‘vitrified’ ing 10 cm provided a date of 2490 ± 80 stones in archaeological context. bP (S.A.C.2229; Soares & Martins, A transect, Q1–T1, was cut transversely 2010), or 791–415 cal BC2.Thiswould to excavate the inner rampart (Figure 6). suggest that the dwelling had been aban- Innovative building techniques were found doned from the mid-eighth century BC in this trench: a new outer masonry struc- and, as the entrance of this dwelling was ture with flat stones laid on top, new built over the destroyed foundations of foundations, and remains of a timber- the wall, this abandonment gives a ter- laced framework. minus post quem for the fire of the wall. Fire marks were discovered in thick and At Ratinhos, we found slates with hard layers of reddish fired clay, ash, and charcoal, found deep and widely spread 2 The atmospheric curve IntCal13 (Reimer et al., inside the foundation of the wall, which 2013) and the OxCal v4.3.2. program (Bronk Ramsey, consisted of an irregular line of large slates 2017) were used for calibration.

Figure 6. Ratinhos (Moura, Portugal). 1: Plan with the location of reddened stones and fired clay pieces over the acropolis rampart (transect Q1-T1). 2: Photograph of the transect from the west, with postholes (A1-A2), during the 2007 excavation campaign.

calcinated surfaces and others with a Sample CRAT06/N3/L01 is a proto- reddish colour that we can define as ‘red- lithic sample from an outcrop located to dened’ (Figure 7). the east of the site. It has a silicate

Figure 7. Ratinhos (Moura, Portugal). Samples of a fired clay piece, a reddened slate, and a fragment of the bedrock, with the main components according to X-Ray Diffraction (XRD).

composition, made of pyroxene, K and sample CRAT06/R1/L20 has a grey core CaNa-feldspars, a significant quantity of and an orange-reddish surface. This illite and, mainly, quartz. The absence sample is a small part of a larger stone, a of kaolinite is noteworthy. By contrast, piece of masonry from the fired wall; its

surface has negative impressions of wood SABUGAL VELHO (GUARDA,NORTHERN (Figure 7, C2). PORTUGAL) The grey core of sample CRAT06/R1/ L20 has a similar composition to the pro- At Sabugal Velho, recent excavations have tolithic material: pyroxene, K-feldspars, uncovered many vitrified stones, mainly illite, and quartz, but kaolinite and hema- outside a rampart (Osório & Pernadas, tite are also present. This difference may 2011). The site was occupied in the Late be explained by the natural diversity of the Iron Age (fourth to first century BC) and, lithic substratum (ferric slates). The after having been abandoned for several absence of CaNa-feldspars and the pres- centuries, was reoccupied in the twelfth ence of large amounts of K-feldspar are and thirteenth centuries AD (Osório & more significant; it may indicate that the Pernadas, 2011: 227). A simple masonry core was less affected by fire, because K- wall was built following the plan of a pre- feldspar survives at temperatures of vious one dated to the Late Iron Age between 800° C and 1000° C. The pres- (Figure 8). ence of kaolinite works in this way, since A detailed study of medieval smelting this mineral disappears over 600/650° C furnaces allowed Marcos Osório to reject (Sayanam et al., 1989). K-feldspar had his initial explanation, which linked the indeed disappeared in sample 2 of vitrified stones to metallurgical activities. CRAT06/R1/L20 (from the reddish He was able to demonstrate that the vitri- surface), which is clearly more affected by fication was a protohistoric event, strati- fire. This absence of phyllosilicates and graphically related to the Late Iron Age K-feldspars could mean a combustion layers that spread along the south-western temperature between 1000 and 1100° C, side of the perimeter wall, especially along but the presence of kaolinite suggests that its western corner, where the main temperatures did not exceed 650° C entrance to the settlement was located (Frías et al., 2013). Therefore, despite the (Osório & Pernadas, 2011: 228). differences in colours, the temperature In this area, and towards the south, we wasquitesimilarinsideandoutsidethe photographed vitrified schists and slates stone, between 600 and 650° C, which is that show negative impressions with not enough to vitrify it but sufficient to angular and prismatic shapes, which may redden it. Similar results were obtained represent beam marks (Figure 10, nos. 1– from the fired clay fragment R1/L15, a 2). Beside these, small twin holes with piece retaining the shape of three joists prismatic or pyramidal shapes were that was found beside the stone recorded, most of them measuring CRAT06/R1/L20 (Figure 7): its com- between 1 and 2 cm (Figure 10, no. 5). position was silicate with a large quantity These marks are very similar to others of quartz and a lesser presence of K-feld- found at the site of Castelos de Monte spars and illite. Therefore, it was affected Novo. by temperatures under 1000° C. The slight presence of CaNa-feldspar is also understood in that sense. In the sample CASTELOS DE MONTE NOVO (ÉVORA, from the interior of the fired clay frag- SOUTHERN PORTUGAL) ment,asmallquantityofpyroxenewas detected, which is a natural component of Castelos de Monte Novo is a Late Iron the substratum that would disappear at Age hillfort with three lines of defences, temperatures of over 1000° C. the central circuit being the most

Figure 8. Sabugal Velho (Guarda, Portugal). 1: Plan of the site and location of vitrified stones (after Osório & Pernadas, 2005). 2: View of the wall from the north in 2013.

impressive, with a double line of ramparts no excavations have been conducted there, built with masonry and mud bricks and there is no reliable archaeological or fronted by a broad ditch (Figure 9). But topographical survey. In our visits to the

Figure 9. Castelos de Monte Novo (Évora, Portugal). 1: Plan of the site and location of vitrified stones (after Burgess et al., 1999). 2: View of the ditch, bank, and outer wall from the north.

site, we collected a series of elements, as its western corner, identifying the presence the Évora Archaeological Survey Project of a ‘timber-laced stone wall’ over a dis- team had done along the northern line of tance of more than 300 m. The stones, a the wall (the exterior line of defence), and local schist, show ‘clearly the negative

Figure 10. Samples of vitrified stones from Sabugal Velho (nos. 1–3) and Castelos de Monte Novo (nos. 4–6), and a burnt mud brick from the latter site. The diffractograms refer to no. 6 and the burnt mud brick.

impressions of wood in the vitrified sur- composition, mainly quartz, and Ca-Na faces of the stone’ (Burgess et al., 1999: and K-feldspars. Chlorite, neocalcite, and 143), as has been observed on other sites. ferrihydrite were also present. These ele- The pottery that we have collected or ments, as in the sample from Ratinhos, studied dates the site to the Later Iron suggest temperatures lower than 1000° Age or later (Berrocal-Rangel, 1992: 115, C. The sample from the surface showed an 317). absence of some components, such as the We have analysed one vitrified stone Ca-Na and K-feldspars, and an increase in and a mud brick (Figure 10). The sample chlorite, which is consistent with lower Montenovo/002 is a schist with vesicular exposure to fire, as the structure groups surfaces (Figure 10, no. 4), fusion of sep- OH disappears over a temperature of 600 arate rocks (Figure 10, no. 6), and possible or 700° C in the chlorite3.Thus,aswith impressions of former wooden elements the stone, the surface was less affected by and metal nails (Figure 10, nos. 4 and 5), fire and, although temperatures are consid- all of them the products of vitrification. erably lower in the mud brick, both ranges The X-Ray Diffraction (XRD) analysis are quite similar (600–850° C for the brick; enabled us to determine the mineral com- 900–1100° C for the stone). position of a sample from the surface and of another taken from the core of the rock. CONCLUSIONS The results show both samples to be silicates. The sample from the surface, The purpose of this article is to draw brown in colour, shows illite (9.90 Å), attention to a growing body of evidence amphibole (8.36 Å), quartz (3.33 Å), and about the use of complex building techni- K-feldspar (3.18 Å). On the other hand, ques in late prehistoric Iberia, as well as to the sample from the core, which was dark provide new data which we believe will grey, contains quartz (3.33 Å), pyroxene help us achieve a better understanding of (2.87 Å), and hematite (2.69 Å). These vitrification throughout Iron Age Europe. differences indicate that the brown surface Our preliminary conclusions are that was affected by a lower temperature, since this phenomenon was the result of a con- the illite disappears at a temperature of currence of circumstances with multiples over 900 or 1000° C. Amphibole and K- causes: natural fires, attacks, building tech- feldspars change around 1000° C, while niques, ritual or symbolic actions. the presence of pyroxene in the black core Furthermore, different effects were sample indicates a temperature higher that observed: not only the vitrification of the 1100 °C (García-Giménez et al., 2016). stones, but also calcination (Ralston, 2006: We conclude that the whole rock was vit- 155) and reddening. Burnt ‘ramparts of rified, reaching a temperature of 850° C, earth’, like those found on Irish hillforts, and, although temperatures were more should also be included (O’Brien et al., regular than those at Pozos de los Moros, 2018). they can also be related to an irregular fire, This phenomenon has been identified accidental or deliberate, with an oxidizing in ramparts from the Middle and Late atmosphere. Bronze Age to early medieval times of We analysed the mud brick Montenovo/ 01 using samples from its surface and 3 This range of temperatures corresponds to the replacement of calcite by neo-calcite, which refers to the core (as we did at Ratinhos). The results calcination process of calcite between 600 and 850° C from the core emphasized its silicate (García-Giménez et al., 2016: 64).

western, northern and central Europe not only because the leaves of gates were (Figure 1). Vitrification is not culture-spe- made of wood, but also because the gate cific, although there is a close relationship itself had a timber framework. The incorp- with the spread of timber-laced ‘Celtic’ oration of beams into the main gates was ramparts, i.e. the various types of murus related to their symbolic importance and celticus (Fichtl, 2010). to overcome their defensive weakness. We have studied some Iberian cases This explains the investment in technical and various different explanations. innovations. From what we know about Vitrification as a technical device could be ancient rampart building in Andalucía identified at Cerro das Alminhas, where (Moret, 1996: 189, 194ff., 209; Escacena the main entrance to the settlement Carrasco, 2002: 87ff.), it was the includes a very hard burnt floor made of Phoenicians who brought these new tech- greywackes. This can be interpreted (in niques to the Iberian Peninsula. contrast to the interpretations offered by A second concurrence of elements is Brothwell et al., 1974 or Kresten et al., visible in the after Iron Age, and we 1993) as reflecting the use of a building believe that it could be related to the method to reinforce the foundations. At Roman wars of conquest. At this time, the Pozos de los Moros, despite the theories use of timber-laced walls around the entire involving meteorites or volcano eruptions, settlements could be a regular feature, as the concentration of vitrified stones specif- Monte Novo, Sabugal Velho and Fraga do ically at the only point of access to the Romualdo show. Cases of such vitrified settlement lead us to suspect the presence walls are quite infrequent because it is of a gatehouse made of timber and stones. more difficult to burn a solid wall built The site of Ratinhos, where burning is with stones and mud bricks and probably associated with stratigraphic evidence of crowned with defences (Ralston, 1986: 37; destruction, is a good example of a third 2006: 130; Fichtl, 2010). cause, i.e. the burning of walls as evidence It seems, on current evidence, that the of attacks or violent events on settlements. phenomenon of vitrified walls is exclusive Elsewhere in Europe we cannot identify to the central and south-western Iberian the scale or nature of such violence (Cook, Peninsula. In northern Iberia, cases of 2013: 94). timber-laced ramparts are few and debate- The main result of our comparative able (Moret, 1996: 76.) The testimonies study is that we have been able to differ- of Classical Greek and Latin writers tell us entiate between two main trends in the that throughout the Roman conquest of spread of ‘vitrification’. Most cases of vitri- the Iberian Peninsula there were cases of fied stones in the main access areas of sites walls built with wooden supports, as at are found in Late Bronze Age/Early Iron Pallantia (Palencia, Spain)4 in 74 BC. Age hillforts, as dated by excavations or Before that, wooden structures were only intensive surveys (e.g. Passo Alto, used for specific elements such as gates, Ratinhos, Pozo de los Moros), whereas a palisades, or floors (Moret, 1996: 76), but small group of sites with vitrified remains new approaches and better archaeological along a substantial stretch of the walls date to the later Iron Age. 4 ‘While Pompey was laying siege to Pallantia and As a hypothesis, we propose that the underrunning the walls with wooden supports, Sertorius first cases are evidence of the simplest suddenly appeared on the scene and raised the siege. Pompey hastily set fire to the timbers and retreated to kind of timber framework within the Metellus’. Appian, The Civil Wars, I, 112, ed. Horace walls; they are located mainly on gates, White, Loeb Classical Library.

techniques are radically changing this Complutum 2). Madrid: Editorial picture. Complutense. Berrocal-Rangel, L. 2003. La expansión meridional de los chevaux de frise: los castros célticos del Suroeste. In: N. Alonso ACKNOWLEDGMENTS i Martínez, ed. Chevaux-de frise i fortificació en la Primera Edat del Ferro This work was supported by the Europea. Lleida: Universitat de Lleida, pp. Ministry of Economy, Industry and 209–32. Competitiveness of Spain, under Project Berrocal-Rangel, L. & Moret, P. 2007. Las ‘ fortificaciones protohistóricas de la HAR2016-77739-P Late Prehistory Hispania céltica. Cuestiones a debate. In: Architecture in the Western Spanish L. Berrocal-Rangel & P. Moret, eds. Plateau. Archaeotecture and Archaeometry Paisajes fortificados de la Edad del Hierro about the built heritage of the Vettones (Bibliotheca archaeologica hispana 28). hillforts’. We want to express our gratitude Madrid: Real Academia de la Historia, Casa de Velázquez, pp. 169–330. to Virgilio H. Correia, and to Catriona Berrocal-Rangel, L. & Silva, A.C. 2010. O Gibson and Colin Burgess for their Castro dos Ratinhos. Escavações num advice, dates, and visits to Castelos de povoado proto-histórico do Guadiana (O Monte Novo. António Carlos Silva shared Arqueólogo Português, Suplemento 6,). with us his recent research at Ratinhos, Lisboa: Museu Nacional de Arqueologia. and Marcos Osório and António Monge Bronk Ramsey, C. 2017. Methods for Summarizing Radiocarbon Datasets. Soares showed us materials and structures Radiocarbon, 59: 1809–33. https://doi.org/ from Sabugal Velho and Passo Alto. We 10.1017/RDC.2017.108 owe much to the lessons and master Brothwell, D.R., Bishop, A.C. & Woolley, A. classes of Professor Ralston, who encour- R. 1974. Vitrified Forts in Scotland: A aged us to carry out this research. Problem in Interpretation and Primitive Technology. Journal of Archaeological Science, 1: 101–07. https://doi.org/10. 1016/03054403(74)90020-X REFERENCES Buchsenschutz, O. & Ralston, I. 1981. Les fortifications des âges des métaux. Almagro-Gorbea, M. ed. 2014. Protohistory of Archéologia, 154: 24–36. the Far West of Europe: From Neolithic to Burgess, C., Gibson, C., Correira, V.H. & Roman Conquest. Burgos: Universidad de Ralston, I. 1999. Hillforts, Oppida and Burgos & Fundación Atapuerca. Vitrification in the Évora Area, Central Álvarez‐ Sanchís, J.R. 2000. The Iron Age in Portugal, 1986–1988. A Preliminary Western Spain (800 bc–ad 50): An Report. Northern Archaeology, 17/18: 129– Overview. Oxford Journal of Archaeology, 47. 19: 65–89. https://doi.org/10.1111/ Catanzariti, G., Mcintosh, G., Soares, A.M., 14680092.00100 Díaz, E., Kresten, P. & Osete, M.L. Bähr, V., Krause, R. & Gebhard, R. 2012. 2008. Archaeomagnetic Dating of a Neue Forschungen zu den Befestigungen Vitrified Wall at the Late Bronze Age auf dem Bernstorfer Berg bei Kranzberg, Settlement of Misericorda (Serpa, Landkreis Freising, Oberbayern. Bayerische Portugal). Journal of Archaeological Science, Vorgeschichtliche Blatter, 77: 5–41. 35: 1399–1407. https://doi.org/10.1016/j. Baitinger, H. & Kresten, P. 2012. jas.2007.10.004 Geoarchäologie zweier Hessischer Celestino, S. & López-Ruiz, C. 2016. “Schlackenwälle”: Glauberg und Altköning. Tartessos and the Phoenicians in Iberia. Archäologisches Korrespondenzblatt,42: Oxford: Oxford University Press. 493–507. Childe, V.G. & Thorneycroft, W. 1938. The Berrocal-Rangel, L. 1992. Los pueblos célticos Experimental Production of the del Suroeste de la Península ibérica (Extra Phenomena Distinctive of Vitrified Forts.

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Wadsworth, F.B., Heap, M.J., Damby, D.E., pozzolanic additions to cement using Hess, K.U., Najorka, J., Vasseur, J., et al. waste, gemology, loess, mineralogy, and 2017. Local Geology Controlled the ceramic materials. She coordinates the Feasibility of Vitrifying Iron Age ‘ Buildings. Nature, Scientific Reports,7: Applied Geochemistry Clays, Cements, 40028. https://doi.org/10.1038/srep40028 and Ceramics’ research group. Youngblood, E., Fredriksson, B.J., Kraut, F. & Frediksson, K. 1978. Celtic Vitrified Address: Rosario García-Giménez, Forts: Implications of a Chemical- Department of Geology and Petrological Study of Glasses and Source Rocks. Journal of Archaeological Science,5: Geochemistry, Universidad Autónoma de 99–121. https://doi.org/10.1016/03054403 Madrid, Carretera de Colmenar Viejo, (78)90027-4 Km. 15, Campus de Cantoblanco, 28049 – Madrid. [email: [email protected]].

BIOGRAPHICAL NOTES Lucía Ruano is a PhD researcher at the Luis Berrocal-Rangel obtained his PhD in Autonomous University of Madrid, spe- 1992 from the Autonomous University of cializing in the Iron Age of the northern Madrid, where he is now Professor of Iberian Peninsula. Her research seeks to European Prehistory. He specializes in use architecture and the use of space to Celtic archaeology, mainly of the Celts in understand long-term processes of change the Iberian Peninsula, and in Late Bronze and continuity, as well as to acquire tools Age and Iron Age architecture. He is from other disciplines, such as ethnog- Principal Researcher of the project ‘Late raphy, to better understand aspects of Prehistory Architecture in the Western daily life. Spanish Plateau.’ He is has been a member of the European Association of Address: Lucía Ruano, Department of Archaeologists since its foundation in Prehistory and Archaeology, Universidad 1993 and became a member of the Real Autónoma de Madrid, Carretera de Academia de la Historia of the Kingdom Colmenar Viejo, Km. 15, Campus de of Spain in 2002. Cantoblanco, 28049 – Madrid. [email: [email protected]]. Address: Department of Prehistory and Archaeology, Universidad Autónoma de Madrid, Carretera de Colmenar Viejo, Raquel Vigil de la Villa has a PhD degree Km. 15, Campus de Cantoblanco, 28049 in Chemistry. She is Professor of – Madrid. [email: [email protected]]. Materials Science and Crystallography at the Autonomous University of Madrid. She specializes in XRD and SEM/EDX. Rosario Garcia-Giménez has PhD degrees Her main research areas are in archaeom- in chemistry, legal history, and physical etry, materials analysis, mineralogy, and geography. She is Professor of Geology ceramic materials. She is a member of the and Director of the Department of Geomaterials group with the Cement Geology and Geochemistry at the Faculty Institute of the Consejo Superior de of Sciences of the Autonomous University Investigaciones Científicas. of Madrid. She specializes in XRD and polarization optical microscopy. Her main Address: Raquel Vigil, Department of research areas are in archaeometry, Geology and Geochemistry, Universidad

Autónoma de Madrid, Carretera de Cantoblanco - 28049 – Madrid [email: Colmenar Viejo, Km. 15. Campus de [email protected]].

Les murs vitrifiés de l’âge du Fer dans l’ouest de l’Ibérie : nouvelles recherches archéométriques

Au cours des vingt dernières années, le phénomène des remparts vitrifiés de l’âge du Fer a été reconnu de plus en plus manifestement dans la pninsule Ibérique. Après la découverte des premiers murs conte- nant des pierres vitrifiées dans le sud du Portugal, plusieurs sites dispersés à travers l’Ibérie occidentale ont été identifiés. Nous avons pu établir une séquence chronologique allant de la fin de l’âge du Bronze àl’âge du Fer récent sur la base des données archéologiques et en nous référant aux différentes circon- stances historiques et fonctionnelles. Notre article utilise les données provenant de divers sites pour mieux comprendre les causes de la vitrification des structures en pierre. De plus, nous avons analysé des échantillons de pierres et de briques crues modifiées par l’action du feu provenant de ces sites, ce qui nous a permis d’évaluer le rapport existant entre les différents processus historiques et les différences observées dans le matériel archéologique. Toutes ces données servent à faire progresser notre compréhension d’un phénomène largement répandu en Europe celtique. Translation by Madeleine Hummler

Mots-clés: vitrification, péninsule ibérique, archéométrie, remparts, sites de hauteur, fortifications

Das Phänomen eisenzeitlicher Schlackenwälle ist auf der Iberischen Halbinsel über die letzten zwanzig Jahre zunehmend deutlich in Erscheinung getreten

Nachdem die ersten verschlackten Steinwälle zunächst im Süden Portugals entdeckt wurden, streuen neuere Entdeckungen quer über das westliche Iberien. Die archäologischen Zeugnisse erlauben es, eine chronologische Abfolge von der Spätbronzezeit bis in die späte Eisenzeit zu erstellen, mit zeitspezifisch unterschiedlichen technischen und historischen Deutungen. Der vorliegende Beitrag nimmt die Daten von verschiedenen Fundstellen in den Blick, mit dem Ziel, den jeweiligen Kontext, in dem die Verschlackung dieser Strukturen erfolgte, besser zu verstehen. Eine Reihe von verschlackten Steinen und Lehmziegeln von den betreffenden Fundstellen wurde analysiert, was es uns gestattet, die im archäologischen Befundbestand vorhandene Variabilität mit Bezug auf unterschiedlichen historischen Prozessen zu erklären. Auf Grundlage dieser Daten ist es unser Ziel, zu einer besseren Kenntnis dieses in Europa weit verbreiteten Phänomens beizutragen.

Schlüsselwörter: Verschlackung, Iberische Halbinsel, Archäometrie, Schlackenwälle, Ringwälle, Befestigungen