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bs_bs_banner Archaeometry 59, 6 (2017) 1065–1081 doi: 10.1111/arcm.12298 I N T E G R AT E D A N A LY T I C A L T E C H N I Q U E S F O R T H E S T U D Y O F C O L O U R I N G M AT E R I A L S F R O M T W O M E G A L I T H I C BARROWS* C. OLIVEIRA,1,2† A. M. S. BETTENCOURT,3 A. ARAÚJO,1 L. GONÇALVES,4 I. KUŹNIARSKA-BIERNACKA5 and A. L. COST
  INTEGRATED ANALYTICAL TECHNIQUES FOR THE STUDYOF COLOURING MATERIALS FROM TWO MEGALITHICBARROWS* C. OLIVEIRA, 1,2 †  A. M. S. BETTENCOURT, 3 A. ARAÚJO, 1 L. GONÇALVES, 4 I. KU Ź NIARSKA-BIERNACKA 5 and A. L. COSTA 6 1  REQUIMTE/LAQV, Polytechnic of Porto  –   School of Engineering (ISEP), Rua Dr. António Bernardino de Almeida, 431, 4200-072 Porto, Portugal  2  Department of Heritage Studies, University of Porto, Via Panorâmica Edgar Cardoso, S/N, 4150-564 Porto, Portugal  3  Landscape, Heritage and Territory Laboratory (Lab2 PT), Department of History, University of Minho,Campus de Gualtar, 4710-057 Braga, Portugal  4  Earth Sciences Centre, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal  5  REQUIMTE/LAQV, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal  6   Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Terminal deCruzeiros do Porto de Leixões, Avenida General Norton de Matos, S/N, 4450-208 Matosinhos, Portugal We have determined the composition of rock art pigments from two megalithic barrows located in the north of Portugal. The use of XRD, SEM   –   EDS and FT   –   IR spectroscopy con   󿬁 rmed the presence of hematite and kaolinite in the red pigments from the Eireira barrow, and kaolinitein the white pigment from the Leira das Mamas barrow. The organic composition of the pig-ments was studied by GC   –   MS, suggesting that the red sinuous lines and dots from the Eireirabarrow were prepared with cooked or heated algae and/or aquatic plants, with egg as binder,while the white pigment from the Leira das Mamas barrow revealed a mixture of vegetable oils for kaolinite moulding, which could be stabilized by temporary exposure to high temperatures.The multi-analytical approach used on this study of megalithic pigments allowed the recoveryof important data about north-western prehistoric communities, namely the way in which theyexploited existing resources and their ability to transform them.  KEYWORDS:  MEGALITHIC BARROWS, PIGMENTS, COLOURING MATERIALS, GASCHROMATOGRAPHY  –  MASS SPECTROMETRY (GC – MS), CHEMICAL ANALYSISINTRODUCTION Paintings in chambers and corridors of megalithic barrows are well known in Western Europe(Shee 1974; Bueno-Ramírez and de Balbín-Behrmann, 2002; Bueno-Ramirez  et al.  2012).Despite their dissemination throughout Europe, they are mostly found in north-west Iberia, morespeci 󿬁 cally in the Galicia region (Spain), together with the north and centre-north of Portugal(Vasconcelos 1907; Correia 1924; Coelho 1931; Shee 1974, 1981; Jorge 1994, 1997; Carrera1997, 2005, 2011; Silva 1997a,b; Cruz 1998, 2001).This phenomenon has prompted many different studies related to the dating of art and mega-lithic phenomenon (Cruz 1995; Carrera 2002; Carrera and Valcarce 2006, 2008), the *Received 15 April 2016; accepted 25 November 2016 † Corresponding author: email   Archaeometry  59 , 6 (2017) 1065 – 1081 doi: 10.1111/arcm.12298 © 2017 University of Oxford bs_bs_banner  interrelationship between painted and carved motifs (Jorge 1997, 2003; Bradley and Valcarce1999; Bueno-Ramírez and de Balbín-Behrmann, 2002; Carrera 2005; Valcarce and Vázquez2006; Ramírez  et al.  2008; Bueno-Ramírez  et al.  2009), the organization and interpretation of the motifs in their micro-contexts (Sanches 2006a,b, 2008 – 9) and on painting conservationtechniques and methodologies (Carrera 1999, 2003, 2011, 2014; Carrera and Valcarce 2003).However, a systematic research programme aiming to study the chemical composition of colourants and binders used to illustrate the symbolic world of the builders and users of dolmensfrom north-west Iberia is lacking. In fact, this kind of interdisciplinary study is crucial todetermine how the prehistoric communities of north-west Iberia took advantage of the existingresources and to analyse their ability to transform them.The study of cultural heritage material, which is often precious and fragile, calls for non-destructive micro-analytical methods. Some analytical techniques were used for the study of the composition (e.g., hematite, goethite or charcoal) of the pigments, and/or on the methodolo-gies used in their preparation, such as grinding, mixing or heating. Pigments may be mixed withextenders (clay, calcite, bone, talc, potassium feldspar, micas etc.) and with binders (water,vegetable oil or animal fat) (Chalmin  et al.  2003). Additionally, extensive physicochemicalanalysis of ancient paintings can allow the identi 󿬁 cation of the elemental and structural compo-sition of pigments and, sometimes, their possible geographical srcin (Chalmin  et al.  2003).In the context of the project   ‘ Funerary and Ceremonial Practices between the Neolithic to theBronze Age Approached by Archaeometry ’— the ARQUEOM Project, the present study has beenfocused on the characterization of painted art found on two megalithic monuments located indifferent areas of north-western Portugal: (i) the Eireira barrow, on the coast, and (ii) the Leira dasMamas or Lamas barrow, in the hinterland (Fig. 1). It is intended to identify the pigment composi-tion and the preparation method (extenders and/or binders). It is important to state that as pigment and extendersometimes comefrom the samenatural mineral or compound, ouruseoftheterm ‘ pig-ment  ’  includes both pigment and extender. Combinations of different techniques were used to iden-tify the crystalline phases of the pigments (XRD), carry out morphological observations (SEM)coupled with an assessment of the elemental composition (EDS), identify the mineralogical and or-ganic components (FT – IR) and identify the composition of the binders (GC – MS). THE ARCHAEOLOGICAL CONTEXTS The Eireira barrow The Eireira barrow is a Neolithic monument located in A 󿬁 fe, Viana do Castelo, in the foothills of the north-western slope of Santa Luzia mount, 400m from the coast and near the valley of theCabanas River. The local geological substrate is composed of medium to  󿬁 ne-grained two-micagranite (Teixeira  et al.  1972; Pereira 1992).The site was excavated by Eduardo Jorge Lopes da Silva, between 1986 and 1989, but only afew papers with architectural features of the monument and some carving descriptions were pub-lished (Silva 1988, 1994, 1997a, 2003). Thus, there is a gap in the knowledge regarding funeraryrites (in which we include the paintings) and the chronology within the  󿬁 fth to fourth millennia or the third millennium  BC , during which the barrow was erected and reused, respectively. Somelithic and ceramic artefacts from this monument, exhibited in the Casa dos Nichos Museum, inViana do Castelo, support these chronologies.The monument has an oval shape tumulus, about 24.50m long from east to west and 19.9mfrom north to south, and an undifferentiated chamber and corridor. The chamber was made with1066  C. Oliveira  et al. © 2017 University of Oxford,  Archaeometry  59 , 6 (2017) 1065 – 1081  local granitic orthostats, many of them polished, engraved and with some remains of paintings.However, after the archaeological excavations, the  in situ  orthostats remained exposed to theelements; consequently, the paintings are in a worrying state of degradation. Fortunately, agranitic orthostat in the form of a pillar had been previously removed to the Museum of Decorative Arts of Viana do Castelo, allowing these paintings to be preserved from theenvironmental degradation and vandalism.This painted pillar was found in 1987 near the head orthostat, during the second archaeologicalintervention on the Eireira barrow (Silva 1988). It is about 1.53m in height, 0.74m wide and0.24m thick (Almeida 2008; Carrera 2005). The engraved surface was previously polished andshows four red-coloured wavy lines, mostly well preserved, arranged horizontally at the bottomof the pillar. Nineteen more traces of paint on the top of the pillar were also identi 󿬁 ed, generallylittle circles and dots, as well as two engraved cup marks. All the motifs were painted in red withthe exception of the engraved cup marks, which are not painted (Fig. 2 (a)). The Leira das mamas barrow The barrow of Leira das Mamas is a Neolithic funerary monument located in Lamas, Braga,on a hill in the valley of the river Ledo or Veiga (Fig. 1). The local geological substrate is Figure 1  The location ofthetwo case studiesinnorth-west Iberia.[Colour   󿬁  gure can be viewedat ] Colouring materials from two megalithic barrows  1067 © 2017 University of Oxford,  Archaeometry  59 , 6 (2017) 1065 – 1081  composed of medium to  󿬁 ne-grained biotitic granite (Teixeira  et al.  1972; Ferreira  et al. 2000). The site was accidentally discovered in February 1993, during the preparation of earthworks for a new housing development. Between 1993 and 1999, three archaeologicalexcavations were carried out at this monument and, in 2000, its reconstruction was completedthrough the initiative of the Lamas village hall authorities together with the Museum of Archaeology D. Diogo de Sousa, in Braga, where the offerings deposited during the funerarypractices are exhibited.The archaeological works concluded that the Leira das Mamas barrow contained a chamber with a short open corridor facing south-east. The barrow is approximately 34m in diameter and was constructed with compacted dark brown soil containing dispersed charcoal elements.The ceramic and lithic offerings (hemispherical containers; polished stone artefacts such as axes,adzes and one gauge; arrowheads; microliths; lamellas;  󿬂 akes etc.) had no indication of use. Thetypology of the deposited objects suggests that the monument was constructed and used duringthe regional Middle to Late Neolithic, between the end of   󿬁 fth and the end of fourth millennia BC . Indicators of its reuse during other moments in prehistory are disappointing and inconclusive(Bettencourt 2013).Two orthostats from this monument present reticular motifs that Silva (2003) describes asbeing composed of white and red paint. However, the presence of these two colours was not con 󿬁 rmed, as we were able to detect only white pigment. Both orthostats, one 1.08m in height,1.10m long and 0.11m wide and the other 1.12m in height, 0.76m long and 0.125m wide,present on their polished surface irregular reticulated  󿬁 gurines of a whitish colour (Fig. 2 (b))(Bettencourt 2013). Fortunately for this study, these two orthostats were not used on thereconstruction of the monument but were deposited in Lamas village hall, which has allowed abetter preservation of the painted motifs. Figure 2  The painted orthostats from (a) Eireira and (b) Leira das Mamas. [Colour   󿬁  gure can be viewed at ] 1068  C. Oliveira  et al. © 2017 University of Oxford,  Archaeometry  59 , 6 (2017) 1065 – 1081
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