Mineralogical, petrographic and geochemical characterisation of white ...

Eur. J. Mineral. 2011, 23, 857–869 Published online September 2011

IMA 2010, Budapest Mineralogical Sciences and Archaeology

Mineralogical, petrographic and geochemical characterisation of white and coloured Iberian marbles in the context of the provenancing of some artefacts from Thamusida (Kenitra, Morocco) FRANCESCA ORIGLIA1,*, ELISABETTA GLIOZZO1, MARCO MECCHERI1, JORGE E. SPANGENBERG2, ISABELLA TURBANTI MEMMI1 and EMANUELE PAPI3 1

Dipartimento Scienze della Terra, Universita` di Siena, Via Laterina 8, 53100, Siena, Italy *Corresponding author, e-mail: [email protected] 2 Institute of Mineralogy and Geochemistry, University of Lausanne, Anthropole, CH-1015, Lausanne, Switzerland 3 Dipartimento di Archeologia e Storia delle Arti, Universita` di Siena, Via Roma 56, Siena, Italy

Abstract: A multi-analytical study has been carried out on a collection of white and coloured Iberian marbles. A total of 135 marble specimens were collected in Spain and Portugal from the Betic chain (Alhaurin de la Torre, Mijas, Macael), Ossa Morena (Alconera, Almadeń de la Plata and Viana do Alentejo), and the Estremoz Anticline (Bencatel, Borba and Estremoz) areas. X-ray diffractometry and carbon and oxygen stable isotope analysis were carried out on these samples; 38 samples were also investigated by optical and scanning electron microscopy. The results provide a set of diagnostic parameters that allow discriminating the sampled marble quarries. The carbonate minerals composition is distinctive for the Mijas and Alhaurin de la Torre marbles; the isotopic analysis allows discriminating also between these two dolomitic marble quarries. The Ossa Morena and Estremoz Anticline marbles share a similar stable isotope composition; the accessory mineral content, the maximum grain size (MGS) and the fabric are particularly useful in the distinction between them. In the framework of archaeometric provenance studies on Thamusida (Kenitra, Morocco) Roman marble artefacts, a specific comparison between this new Iberian database and archaeological findings has been carried out. The hypothesis of commercial exchanges between the Iberian regions and Roman Morocco is supported by the results of the provenance study, which suggested the Almadeń de la Plata and Mijas quarries as possible sources of raw materials for the production of archaeological artefacts. Key-words: marbles, Spain, Portugal, Thamusida, petrography, mineralogy, carbon and oxygen stable isotopes.

1. Introduction

of ancient marble exploitation is found at the Viana do Alentejo, Alconera and Almadeń de la Plata quarries (Lapuente & Turi, 1995). Recently, Antonelli et al. (2009) carried out a provenance study of marble artefacts found at Volubilis (Meknes, Morocco), the headquarters of the Mauritania Tingitana Roman province. The results obtained on Volubilis site represent the first indication of the employment of Estremoz marbles in an African Roman province. In the context of an ongoing archaeometric research at the Roman site of Thamusida (Kenitra, northern Morocco), the present work is intended to characterise a collection of Iberian marble samples in order to verify this provenance for some marble artefacts discovered during the archaeological excavation. In Thamusida, white or slightly coloured marbles were used for the production of daily objects, architectural elements and inscriptions. A preliminary comparison of Thamusida stone artefacts with published databases on Greek, Turkish and Italian marbles (Coleman & Walker, 1979; Gorgoni et al., 2002; Capedri

Marbles from the Lusitania and Baetica regions of the Iberian Peninsula have been extensively exploited and used in the Roman period since the 1st century AD; they were mainly employed for public or private building or decorative purposes (Cabral et al., 2001; Morbidelli et al., 2007). Among the quarries exploited in the Baetica region during Roman times (1st–3rd century AD), especially those of Mijas and Coin in the Malaga province were used for local building, epigraphy and sculptural purposes (Lapuente et al., 2002). From the same area, Macael marbles of the Filabride Complex (Spain) were exploited since the times of the Flavian dynasty (second half of 1st century AD) for the extraction of white and ‘‘Anasol’’ varieties (Nogales et al., 1995; Morbidelli et al., 2007). Among the Portuguese quarries, those of the Estremoz Anticline supplied easily workable marbles, and their use was attested in Augusta Emerita, capital city of Lusitania, and Italica (Nogales et al., 1995). In the Ossa Morena Zone, evidence eschweizerbart_xxx

0935-1221/11/0023-2145 $ 5.85 DOI: 10.1127/0935-1221/2011/0023-2145

# 2011 E. Schweizerbart’sche Verlagsbuchhandlung, D-70176 Stuttgart

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F. Origlia, E. Gliozzo, M. Meccheri, J.E. Spangenberg, I. Turbanti Memmi, E. Papi

et al., 2004; Attanasio et al., 2008) allowed identifying some provenances, such as Carrara and Marmara (Origlia et al., 2009a). The artefacts were also compared with data obtained from the characterisation of some of the local Moroccan stone materials. The results of the preliminary provenance study suggested that, for a limited number of archaeological objects, Classical Mediterranean and local marble origins can be excluded (Origlia et al., 2009b). In light of the results obtained at Volubilis and considering the widespread use of Iberian stones during Roman times, the present work aims at assessing the Baetic or Lusitanian provenance of some Thamusida artefacts, which would in turn support the hypothesis of commercial exchange between those areas. The multi-methodological approach adopted in this study and the collection of integrated data on both raw and archaeological materials are fundamental to ascertaining the origin of the Thamusida artefacts.

2. Archaeological setting The archaeological site of Thamusida is located about 50 km north from the modern town of Rabat in Morocco, along the oued Sebou (Fig.1). Inhabited from the 7th century BC, the area was occupied by the Roman Army during Fig. 1. The location of the archaeological site of Thamusida, the 1st century AD. The Roman occupation lasted until the Morocco. 3rd century AD and converted the settlement into a military town. Close to Volubilis, i.e. the headquarters of the Mauretania Tingitana Roman province, the geographical limestone (Origlia et al., 2009a). The employment of white position of the site was of outstanding importance both and coloured marbles spread during the Roman occupation (1st- 3rd centuries AD), while in the post Roman period to militarily and economically. Performed by the University of Siena and the Moroccan the Arab migrations there are few marble reuse attestaInstitut National de Sciences de l’Archeólogie et du tions. The Roman marble artefacts found at Thamusida Patrimoine from 1999 to 2006, the archaeological excava- mainly consist of fragments of inscriptions, ornamental tions of Thamusida brought to light stones for decoration, tiles, daily objects and few examples of statuary, all premills, inscriptions and marbles, mortars, plasters and pig- sumably dating back to the 2nd and 3rd centuries AD. The eight archaeological artefacts selected for the prements, bricks, bronzes (Gliozzo et al., 2009, 2011a–c), amphorae and window glasses. The results obtained by sent study testify to the employment of both white and archaeometric investigation on building and ornamental coloured marbles. A whitish marble with yellowish spots stones suggested that Thamusida was built mostly using a was used for both an inscription (T6) and a slab (T28). A calcarenite available nearby (Giorgetti & Gliozzo, 2009); light pink marble, further characterised by reddish or few examples of architectural elements and inscriptions brownish veins, was employed for two inscriptions also testify to the use of a local pinkish fossiliferous (T4, T5; Fig. 2a, b) and for a slab (T30). A coarse-grained,

Fig. 2. Thamusida marble artefacts. (a) T4, inscription; (b) T5, inscription; (c) T20, basin. eschweizerbart_xxx

Characterisation of Iberian marbles for a provenance study

pure white marble was used for the production of daily objects, such as the mortar (T14), the pestle (T18), and the basin (T20, Fig. 2c).

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The Ossa Morena Zone is a large portion of the Variscan orogenetic system in the central-western pre-Alpine Iberia. It mainly consists of metasediments entrapping metamorphosed ophiolites and minor intrusive bodies of different ages. In Ossa Morena, the sampled marble areas were Alconera and Almadeń de la Plata in Spain, Viana do Alentejo and the Estremoz Anticline in Portugal. Alconera – In the Badajoz province, the marbles crop out along the Sierra Gorda, close to the Alconera village. The rocks belong to the metacarbonates of the early Cambrian sequence (metadolostones, dolomitic marbles and calcschists: Simancas et al., 2001; Expo´sito et al., 2003), which were involved in Variscan fold structures and shear zones generated by two main deformation events under low grade metamorphism (Azor et al., 1994). The 18 samples were collected from both abandoned and active quarries, partly exploited for gravel. The Alconera collection mainly consists of grey to greyish (Fig. 4c), and partly of white, whitish or slightly pinkish marbles. Almadeń de la Plata – The region of Almadeń de la Plata in the Sevilla province is close to the tectonic junction between the Ossa-Morena Zone and the South Portuguese Zone. Along this regional shear structure the marble lenses of Cambrian-Ordovician age mainly crop out along the Sierra de los Covachos, where several quarries offer white, whitish up to grey tones, and pinkish marbles with dark, reddish or brownish veins (Fig. 4d). At Almadeń de la Plata, a total of 16 specimens of marbles was collected for the characterisation study. Viana do Alentejo – The medium to high grade metamorphosed carbonate levels and bodies are interbedded with a series of para- and orthoschists of probable late Neoproterozoic to Cambrian-Ordovician age (Barros et al., 1972), together with ophiolites, orthogneisses, micaschists and blackish quartzites. The metacarbonates are calcitic and dolomitic marbles, locally spread with Ca-silicate layers. Samples of white, pinkish, grey marbles (Fig. 4e), variously veined, layered or banded, were collected from four abandoned quarries close to the SW side of the village. The Estremoz Anticline is represented by an antiformal structure, with a NW-SE length of about 40 km and up to 8.5 km wide. The main Portuguese production centres of ornamental marbles are located in the Estremoz Anticline region. The marble formations belong to the Ordovician Estremoz volcano-sedimentary carbonate complex (Carvalho et al., 2008, and references therein), which rests on the Cambrian Dolomite Formation and is overlain by Silurian black shales with graptolitic lydites. Forty-four samples of white and coloured marbles were collected from the Bencatel, Borba, and Estremoz quarries, located to the SE extremity of the deposit. The marbles from Bencatel are white to whitish, pinkish (Fig. 4f) and greyish in colour, variably veined or spotted. Most of the samples collected at Borba are pinkish with dark veins (Fig. 4g) or fine grained pure white marbles, but a grey variety was also found. The marbles sampled in Estremoz quarries are typically pure white (Fig. 4h) to whitish in colour, with a light pinkish tint due to the presence of reddish or brownish veins.

3. Geological setting and sampling The Betic Chain and the Ossa Morena Zone in the Iberian Massif (general geological information in Lapuente et al., 2000) are important sources for ornamental stones. Within the Ossa Morena Zone, the Estremoz Anticline region (according to Lapuente et al, 2000) can be considered as an independent district as it forms a group of several quarries located in the same Hercynian structure. For the purposes of the present study, a total of 135 marble samples were collected from several quarries in the three aforementioned areas. Sample descriptions are provided in Table 1. The Betic Chain is the northern branch of the Betic-RifMaghreb arcuate orogenetic system, located in the southeastern border region of Spain. The regional tectonic setting of the Betic Chain is a result of the superposition of the Alboran Crustal Domain over the Flysch Units, which in turn are thrust over the external zones of the orogen. The Alboran Domain is formed by three major tectonic units: the Malaguide, the Alpujarride, and the Nevado-Filabride complexes (from top to bottom). The last two units comprise the sampled carbonate rocks, which crop out in the two main quarry districts of the Cordillera, Malaga and Almeria (Fig. 3). Malaga - The Malaga district extends WSW of Malaga. In this area 20 samples were collected from active quarries at Alhaurin de la Torre (9 samples) and Mijas (11 samples). The exploited rocks belong to the Middle-Upper Triassic interval of the Alpujarride Complex succession (Andreo & Sans de Galdeano, 1994, and references therein), which underwent a regional high-pressure (HP), low-temperature (LT) metamorphism. The samples taken from Alhaurin de la Torre and Mijas are massive, characteristically white to whitish (Fig. 4a) and greyish, weakly spotted or banded (Alhaurin de la Torre). Almeria – The Almeria district is located on the Sierra de los Filabres, where Macael is one of the main centres for the ancient and present exploitation. The marbles in this area are of predominant to pure calcitic composition and belong to the Nevado-Filabride Complex, in particular to the late Triassic Mulhacen Group (Lapuente et al., 2000) or the Be´dar-Macael Unit (Alonso-Chaves et al., 2004). All these rocks underwent a syntectonic metamorphic imprint from eclogitic conditions to amphibolite-facies retrogression. The sampling comprised five active quarries in the Macael region. The collected marbles (19 samples) are pure white and coarse grained, or grey. Few samples are of the ‘‘anasol’’ type (sensu Morbidelli et al., 2007), characterised by the presence of thin folded veins or greenish layers on a whitish tint (Fig. 4b). eschweizerbart_xxx

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Table 1. Main mineralogical and petrographic features and stable isotope composition of the analysed marbles from the Betic Chain, Ossa Morena Zone and the Estremoz Anticline. d18O

MGS Quarry

Sample

Alhaurin de la Torre AT1-01 AT1-02 AT1-03 AT2-01 AT2-02 AT2-03* AT3-01* AT3-02* AT3-03 Mijas MJ1-01* MJ1-02 MJ1-03* MJ1-04 MJ1-05 MJ2-01* MJ2-02 MJ3-01 MJ3-02 MJ3-03* MJ3-04 Macael MA1-01 MA1-02 MA1-03 MA2-01 MA2-02 MA2-03* MA2-04 MA3-01 MA3-02 MA3-03* MA3-04 MA3-05 MA4-01* MA4-02 MA4-03 MA4-04 MA5-01 MA5-02* MA5-03 Alconera AC2-01* AC2-02 AC2-03* AC2-04 AC3-01 AC3-02 AC3-03 AC3-04* AC3-05 AC3-06 AC4-01 AC4-02 AC4-03 AC5-01 AC5-02 AC5-03 AC5-04 AC5-05 Almaden de la Plata AM1-01

Variety white grey grey grey white grey whitish white grey white greyish greysh whitish grey whitish pinkish whitish grey whitish greyish grey grey grey white white white whitish whitish whitish white grey whitish white whitish grey grey white white grey light pink whitish light pink light grey white white whitish light grey grey grey grey grey greyish greyish greyish greyish whitish greyish whitish

Cal

Sub Sub Sub

Sub Only Only Only Main Main Sub Only Only Only Sub Main Sub Only Only Only Only Only Only Only Main Main Only Main Main Main Only Main Only Only Only Main Only Only Only Only Main Only Only

Dol Only Only Only Only Only Only Only Main Only Main Main Only Only Only Only Only Only Only Only Main rare

Sub Sub Main

Main Main Sub Main

Non-carbonate fraction

Gr

(mm)

GBS

Texture

Fabric

1 1.8 1

S, C C, E E

Ho Ho/He Ho

G/Po G G

2.8

C, E

Ho

G

1.2

S, C

Ho

G

3

C, E

He

Mo

4.3

E

Ho/He

G, Mo

0.2

E, C

Ho

Or

0.4

E, C

Ho

Or

1.6

C, Su

Ho

G

Qtz, Ms, Pl, Tr, Ap, Ttn

3.7

S, C

Ho

G

Fe–ox Pl Qtz, Chl, Ap Qtz, Ms Qtz, Ms Qtz Qtz Pl, Aug, Fe–ox

2

E, Su

Ho/He

G, Mo

0.8

Su, E

Ho/He

G, wOr

0.2

E

He

Or

Qtz

Qtz Qtz (Ap)

Qtz Qtz Qtz, Kfs, Ms Qtz, Ms Qtz, Ms Qtz Qtz, Ms, Phl,Fe–ox, Ap

Qtz, Ms, Fe–ox, Ap Qtz, Ms Qtz, Ms Ms, Fe–ox

Qtz, Ms

Sub Sub Sub Sub Sub Sub

rare Sub

Sub

Qtz Qtz, Ti–ox Qtz Qtz Qtz Qtz Qtz Qtz Qtz, Ms Qtz

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d13C

(%, VPDB) 2.0 1.9 1.4 3.0 3.3 2.2 0.2 0.2 1.4 2.1 5.0 4.9 3.5 5.6 0.6 0.3 3.5 3.4 2.9 5.8 4.4 4.6 6.1 7.3 7.4 3.8 3.6 6.8 8.8 8.8 7.8 5.2 6.0 4.8 4.6 1.6 2.9 3.3 2.1 12.3 11.6 12.2 11.9 10.6 9.8 9.1 11.4 10.9 10.3 11.5 10.9 11.0 10.1 10.0 10.2 10.5 9.4 7.3

4.3 3.8 4.2 4.0 3.9 4.0 3.8 3.9 4.1 2.4 2.0 2.3 2.9 1.6 3.6 3.6 3.1 3.1 3.7 2.5 2.5 2.7 2.2 2.3 2.2 1.9 2.7 2.6 2.3 2.3 1.3 2.3 2.6 2.6 2.7 2.9 2.6 2.4 2.7 2.8 2.9 2.6 2.7 3.1 3.0 1.4 2.6 2.9 2.9 2.4 2.8 2.7 1.7 3.0 2.6 2.9 1.5 2.0


861

Table 1. Continued. d18O

MGS Quarry

Viana do Alentejo

Bencatel

Borba

Sample

Variety

AM1-02* AM1-03 AM1-04 AM2-01* AM2-02 AM2-03* AM2-04 AM3-01 AM3-02* AM3-03 AM3-04 AM4-01* AM4-02 AM4-03 AM4-04 VA1-01 VA1-02 VA1-03 VA1-04 VA1-05 VA1-06* VA2-01* VA2-04 VA2-05 VA2-06* VA2-07 VA3-01 VA3-02* VA3-03* VA3-04 VA3-05 VA4-01* VA4-02 BE1-01 BE1-02 BE2-01* BE2-02 BE3-01 BE3-02* BE4-01* BE4-02 BE4-03 BE5-01 BE5-02 BE5-03 BE5-04 BE5-05 BE6-01* BE6-02 BO1-01* BO1-02 BO1-03 BO1-04 BO2-01* BO2-02 BO2-03 BO2-04 BO3-01* BO3-02 BO3-03*

white whitish light grey white pink pinkish whitish pinkish whitish pink grey white grey greyish grey grey grey whitish white whitish whitish whitish pinkish pinkish pinkish whitish whitish white grey grey white white greyish grey white pinkish grey-white pinkish white whitish white pinkish whitish white grey grey pinkish white grey pinkish pinkish grey white white pinkish pink grey-white whitish greyish pink

Cal Only Only Only Only Main Sub Main Only Only Only Only Main Sub Only Only Only Only Only Only Only Only Only Only Only Only Only Main Only Only Only Main Only Only Main Only Main Only Only Main Only Only Only Only Only Only Only Only Only Main Only Only Only Only Only Only Only Only Sub Only Only

Dol


Qtz, Ms Main Qtz, Ms Qtz, Ms Qtz, Ms, Fe–ox Sub Qtz Main Qtz, Chl, Ap Sub Qtz Qtz Qtz, Ms, Pl, Fe–ox, Ap Qtz Qtz, Pl Sub Qtz, Pl, Phl, Tr, Ms, Tlc, Fe–ox Main Ms Qtz, Ms Qtz, Ms Qtz, Ms Qtz Qtz, Ms Qtz Phl, Fe–ox, Ap Qtz, Kfs, Ms, Tr, Ap, Ttn

Sub

Sub

Sub Sub

Sub

rare Sub

(mm)

Texture

Fabric

2

C, S, Su He

G,Mo

3.2

E, Su

He

Mo

0.8

E, Su

Ho

G

3

E, Su

He

Mo, G

3.5

E, Su

He

Mo, wOr

3.5 2.6

C, E S, C

He Ho/He

G, Mo G

S, C

He/Ho

G

S, C E

He He

G Mo, Or

4.3

E

He

G, Mo

2

S, C, Su Ho/He

G, wOr

0.8 2.5

S, C, Su Ho/He C, Su, E Ho/He

Or Or

0.8

Go, Su

He

Or

3

S, C

He

G,Or

Qtz Qtz, Kfs, Ms, Tr, Ti–ox, Ap, Ttn 4 Qtz Ms Qtz, Kfs, Ms, Chl, Tr, Tlc, Ap, Ttn 5.5 Qtz, Aug 2.2 Ms Qtz, Pl, Kfs, Aug, Ap, Ttn Aug Qtz Ms Qtz, Chl, Fe–ox Qtz Qtz, Ms Qtz, Pl, Ms, Phl, Chl, Ap Qtz, Kfs Qtz, Ms Qtz, Ms Qtz, Ms Qtz Qtz Qtz Qtz, Ms Qtz, Ms, Ti–ox, Ap Qtz Qtz, Kfs, Ms, Fe–ox, Ap, Ttn Qtz, Ms Phl

GBS

Qtz, Ms, Phl, Fe–su, Ap Qtz, Ms Qtz, Ms Ms Main Qtz, Ms, Ap

1.5

S, C, E

Ho

G

1

E

He

Mo

Qtz, Ms, Chl, Fe–ox, Ap

2

S, C

Ho/He

G/Po

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d13C

(%, VPDB) 6.7 9.0 7.1 6.3 9.2 8.9 8.0 7.1 6.5 5.5 5.8 7.7 8.7 5.6 7.1 8.5 7.1 7.3 7.8 8.5 8.2 7.8 9.5 9.9 6.9 7.7 7.9 7.3 7.4 7.8 7.0 6.0 6.2 6.2 5.7 7.0 5.5 6.4 5.9 5.3 5.3 5.9 5.7 6.2 6.0 5.8 6.8 7.1 7.4 6.7 7.1 7.2 5.9 7.0 8.5 8.4 8.2 7.7 6.3 6.3

2.2 2.5 1.7 3.1 2.0 2.6 2.5 2.7 3.5 2.9 2.7 2.2 2.3 3.3 1.1 0.3 0.2 0.0 0.2 0.7 0.1 2.8 2.1 2.6 3.0 2.3 0.2 0.2 0.2 0.5 0.6 3.1 2.9 1.4 1.8 2.0 1.5 2.5 2.9 2.2 2.2 2.0 2.2 1.7 1.7 2.0 1.5 1.1 0.2 1.8 0.8 0.1 1.7 2.3 2.4 2.6 2.3 1.8 1.7 1.6

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Table 1. Continued. d18O

MGS Quarry

Estremoz

Sample BO3-04 BO3-05* EZ1-01 EZ1-02* EZ1-03 EZ1-04* EZ2-01 EZ2-02 EZ2-03 EZ3-01* EZ3-02 EZ3-03 EZ3-04 EZ4-01 EZ4-02 EZ4-03* EZ4-04

Variety whitish whitish whitish white whitish whitish grey grey whitish whitish whitish whitish grey whitish whitish whitish greyish

Cal Sub Main Only Only Only Only Only Only Only Only Only Only Only Only Only Only Only

Dol Main Sub rare

Non-carbonate fraction Qtz, Ms Qtz, Kfs, Phl, Ap Qtz, Ms Qtz, Ms, Ti–ox Qtz, Ms, Chl Qtz, Ms, Fe–ox, Ti–ox, Ms Qtz, Pl, Ms Qtz Qtz, Kfs, Ms, Ap, Ttn Qtz, Ms Qtz, Ms Qtz, Ms Qtz, Ms Qtz Qtz, Ms, Chl

(mm)

GBS

Texture

Fabric

2.3

S,C

Ho

G

2.4

S, C

Ho

G/Po

1.8

S, C

Ho

G/Po

1.7

C, Su

Ho

G

1.8

S, C

Ho

G/Po

d13C

(%, VPDB) 7.9 6.5 5.5 5.4 5.5 5.7 8.2 9.8 6.7 6.6 6.2 7.0 6.3 6.7 6.8 5.7 8.0

1.4 1.0 2.0 2.2 2.1 2.3 1.1 0.6 1.4 1.6 2.0 1.5 2.3 2.7 2.6 2.1 2.6

Notes: Cal, calcite; Dol, dolomite; Sub, subordinate; MGS, maximum grain size; GBS, grain boundary shape, C, curved; E, embayed; S, straight; Su, sutured; He, heteroblastic; Ho, homeoblastic; G, granoblastic; Mo, mortar; Or, oriented; Po, polygonal; wOr, weakly oriented; Aug, augite; Ap, apatite; Chl, chlorite; Fe-ox, iron oxide; Fe-su, iron sulphide; Kfs, K-feldspar; Ms, muscovite; Pl, plagioclase; Phl, phlogopite; Qtz, quartz; Tlc, talc; Ttn, titanite; Ti-ox, titanium oxide; Tr, tremolite (detected by XPRD and/or OM and SEM/EDS analyses). *Samples selected for detailed petrographic investigation.

Fig. 3. Simplified geological sketch of the southern Iberian peninsula (redrawn from Alvarado, 1980).

d18Ocarvalues) of the Spanish and Portuguese marbles as well as of the Thamusida marble artefacts was determined using a Thermo Fisher Scientific (Bremen, Germany) carbonate preparation device and a Gas Bench II connected to a Delta Plus XL isotope ratio mass spectrometer (IRMS) that was operated in the continuous He flow mode. The CO2 was extracted from carbonates with 100% phosphoric acid at 70 C for calcite and 90 C for dolomite. The stable

4. Analytical methods Several techniques have been employed in order to characterise both geological and archaeological materials. All of the samples were submitted to both X-ray powder diffraction (XRPD) using a Philips PW 1710 diffractometer (CuKa, 45 kV and 25 mA) and stable isotope analysis. The carbon and oxygen isotope composition (d13Ccar and eschweizerbart_xxx


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C and O isotope ratios are reported in the delta (d) notation as the per mil (%) deviation, relative to the Vienna Pee Dee belemnite standard (VPDB). The analytical reproducibility estimated from replicate analyses of the laboratory standards Carrara marble and Binn dolomite was better than 0.05 % for d13C and 0.1 % for d18O. A selected group of geological samples and the entire collection of artefacts were further investigated using optical microscopy (OM) and scanning electron microscopy – energy dispersive spectrometry (SEM-EDS). Geological samples have been selected both based on their macroscopic similarity with the archaeological findings and in an attempt to cover the major part of Iberian varieties. The petrographic investigations on thin sections mainly examined the fabric and mineral content, i.e., the features that are considered to be particularly important in these studies (Lazzarini et al., 1980; Moens et al., 1988; Antonelli & Lazzarini, 2004). Scanning electron microscopy was further applied to identify the accessory minerals. The instrument used was a Philips XL30, equipped with an energy dispersive spectrometer (EDS) Philips EDAX DX4. A variety of natural and synthetic materials was used as primary and quality control standards. Operating conditions were as follows: accelerating voltage 20 kV, working distance 10–15 mm. To control the accuracy of the results, the EDS quantitative microanalyses with the theoretical inner pattern were obtained by using the ZAF method of correction.

5. Results

Fig. 4. Photographs of some samples showing the macroscopic features of the studied marbles from Betic chain (4a-b), Ossa Morena Zone (4c-e), Estremoz Anticline (4f-h). (a) AT2-03 from Alhaurin de la Torre, Malaga district; (b) MA2-03 from Macael, Almeria district; (c) AC3-04 from Alconera; (d) AM1-02, from Almadeń de la Plata; (e) VA3-03 from Viana do Alentejo; (f) BE6-0 from Bencatel; (g) BO1-01 from Borba; (h) EZ1-02 from Estremoz.

The results of the mineralogical, petrographic and stable isotope analyses of the Betic Chain, Ossa Morena and Estremoz Anticline geological samples as well as archaeological artefacts from Thamusida are reported in Tables 1 and 2.

Table 2. Main mineralogical and petrographic features, and stable isotope composition of Thamusida marble artefacts.

Sample T4* T5* T6* T14* T18* T20* T28* T30*

Artefact

Variety

Cal

Inscription Inscription Inscription Mortar Pestle Basin Slab Slab

whitish-pink white whitish-pink whitish white white whitish whitish-pink

Main Main Sub Only Only Only Rare Only

Dol Sub Main

Only

d18O


MGS (mm)

GBS

Qtz, Pl, Ms, Ap. Ttn Qtz, Ms, Phl, Tr, Ap, Ttn Ms, Ap Qtz, Ms, Ap, Qtz, Ms, Ap Qtz, Pl, Phl, Ap Ms Qtz, Ms, Ap

2.4 2.2 3.3 3.8 2.6 2.2 3.5 4.4

Su, E E, Su E, Su E, Su C, Su C, Su S, Su S, C, Su

Texture Ho/He Ho/He Ho He He He, Ho/He Ho

Fabric G G G G, wOr G G, wOr G, M G

d13C

(%, VPDB) 5.9 5.7 4.9 5.8 5.9 6.0 3.4 6.0

2.8 1.9 2.2 3.3 2.9 3.5 3.5 3.1

Notes: Cal, calcite; Dol, dolomite; Sub, subordinate; MGS, maximum grain size; GBS, grain boundary shape, C, curved; E, embayed; S, straight; Su, sutured; He, heteroblastic; Ho, homeoblastic; G, granoblastic; Mo, mortar; Or, oriented; Po, polygonal; wOr, weakly oriented; Aug, augite; Ap, apatite; Chl, chlorite; Fe-ox, iron oxide; Fe-su, iron sulphide; Kfs, K-feldspar; Ms, muscovite; Pl, plagioclase; Phl, phlogopite; Qtz, quartz; Tlc, talc; Ttn, titanite; Ti-ox, titanium oxide; Tr, tremolite (detected by XPRD and/or OM and SEM/EDS analyses). *Samples selected for detailed petrographic investigation. eschweizerbart_xxx

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5.1. Mineralogical and petrographic data 5.1.1. Marbles from the Betic Chain 5.1.1.1. XRPD investigations. The Alhaurin de la Torre and Mijas specimens are rather pure dolomitic marbles, with traces of calcite and quartz; Macael marbles belong to two different lithotypes, according to the presence or absence of dolomite. Most of the Macael samples are exclusively calcitic, containing minor amounts of quartz, muscovite and sporadic plagioclase. A smaller group of Macael samples has both dolomite and calcite, generally associated with minor amount of quartz and mica.

5.1.1.2. Optical microscopy and scanning electron microscopy investigations. Alhaurin de la Torre – The analyses performed on samples AT2-03, AT3-01 and AT3-02 confirm that dolomite is the major constituent of marbles with few grains of calcite and quartz (AT302). Graphite is observed as inclusion in dolomite crystals. Marbles are fine grained with homeoblastic texture of granoblastic and polygonal (AT2-03) types, and straight (AT2-03), curved and embayed grain boundary shapes. The maximum grain size (hereafter MGS) ranges from 1 mm (AT2-03 and AT3-02, Fig. 5a) to 1.8 mm (AT3-01). Mijas – The samples selected for petrographic investigation (MJ1-01, MJ1-03, MJ2-01 and MJ3-03) are dolomitic marbles. MJ1-01/03 are characterised by a homeoblastic granoblastic texture, straight, curved or embayed grain boundaries (Fig. 5b), and MGS of 2.8 mm and 1.2 mm, respectively. The other specimens have a heteroblastic mortar texture, characterised by coarse grains (3–4.3 mm at maximum) surrounded by finer fractions (1 mm). Dolomite rims are curved and embayed. Few grains of calcite, apatite and carbonaceous material have also been observed. Macael – In the white marble samples MA4-01 and MA5-02, texture is homeoblastic granoblastic (Fig. 5c) with straight, curved, rarely sutured grain boundaries. The grains are generally twinned, and have a maximum size of 1.6 mm in MA4-01 sample, reaching up to 3.7 mm in MA5-02 sample. Calcite is the major constituent, associated with minor amount of quartz, muscovite and Fe oxides. Plagioclase, tiny crystals of tremolite, very few grains of apatite, titanite and pyrite are observed and identified in MA5-02 sample. The ‘‘anasol’’ type samples (MA2-03 and MA3-03) are equigranular fine grained marbles (MGS reaches 0.4 mm) characterised by homeoblastic granoblastic texture, with curved or locally embayed grain boundaries. Dolomite is the dominant phase, although associated with minor calcite content. The non-carbonate fractions include phyllosilicates (muscovite and phlogopite) and Fe oxides. Dolomite grains are oriented, as well as mica and opaque minerals that may form lepidoblastic layers.

Fig. 5. Polarized light microphotos of thin sections showing textural features of some of the studied marbles and artefacts (scale bar is 1mm). (a) AT3-02, Alhaurin de la Torre: homeoblastic granoblastic texture with embayed grain boundaries; (b) MJ1-01, Mijas: homeoblastic granoblastic texture with curved, embayed grain boundaries; (c) MA5-02, Macael: homeoblastic granoblastic texture with straight and curved grain boundaries; (d) AM3-02, Almadeń de la Plata: heteroblastic mortar texture, embayed and sutured grain boundaries; (e) VA4-01, Viana do Alentejo: heteroblastic mortar texture, embayed grain boundaries; (f) BE4-01, Bencatel: homeoblastic granoblastic texture, oriented microstructure, curved and sutured grain boundaries; (g) BO2-01, Borba: homeoblastic granoblastic texture, straight and curved grain boundaries; (h) EZ3-01, Estremoz: homeoblastic granoblastic texture, straight and curved grain boundaries; (i) T6 artefact: homeoblastic granoblastic texture, embayed grain boundaries; (l) T14 artefact: heteroblastic texture of mortar type, embayed and sutured grain boundaries.

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5.1.2. Marbles from the Ossa Morena Zone 5.1.2.1. XRPD investigations. Calcite is the unique or dominant carbonate mineral in most of the Ossa Morena samples, except for some of the Almadeń de la Plata specimens, where dolomite is prevalent. Among the noncarbonate minerals, quartz is the most frequent. Muscovite is sporadically detected in Almadeń de la Plata, Alconera, and Viana do Alentejo, whereas plagioclase and pyroxene are restricted to VA401 and VA402 samples from Viana do Alentejo.

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embayed boundaries. Quartz is abundant, found as inclusion in calcite as well as in microgranular assemblages. Accessory minerals consist of plagioclase or K-feldspar, muscovite, frequently associated to rare chlorite and talc (VA3-02), crystals of tremolitic amphibole (samples VA201/06 and VA3-02) and augitic pyroxene (VA4-01), scarce grains of apatite and titanite. Phlogopite was only found in VA1-06. 5.1.3. Marbles from the Estremoz Anticline 5.1.3.1. XRPD investigations. Calcite and/or dolomite minerals are always present. Dolomite is dominant in some Borba specimens; the other marbles are mainly composed of calcite, sometimes with a subordinate presence of dolomite. Quartz and muscovite are present in almost all the Estremoz Anticline marbles. Plagioclase has been detected only in EZ2-02 sample.

5.1.2.2. Optical microscopy and scanning electron microscopy investigations. Alconera – Petrographical investigation focuses on AC2-01, AC2-03 and AC3-04 samples. These are characterised by weak to strong lineation (AC3-04) and homeoblastic to heteroblastic texture. All the samples are fine grained (MGS from 0.2 to 0.8 mm) and relics of coarser calcite (2 mm grain size) are present in AC2-01 sample. The grain boundaries are embayed and highly interlocked (sutured type). Calcite is the dominant constituent, associated to a subordinate content of dolomite. The non-carbonate fraction consists of few crystals of quartz and augitic pyroxene (AC3-04), chlorite (AC2-03) as well as opaque minerals (Fe oxides, Ti-oxides). Coarser calcite veins and veinlets of carbonaceous matter are observed. Almadeń de la Plata – Five specimens from Almadeń de la Plata were examined. Among them, AM1-02, AM2-01, AM3-02, and AM4-01 are coarse grained marbles, with MGS ranging from 2 mm to 3.5 mm, while AM2-03 is fine grained (MGS about 0.8 mm). The coarse grained samples show heterogranoblastic (mortar type) texture (Fig. 5d) and embayed, sutured and more rarely curved or straight (AM1-02) rims. Calcite is variously mixed with microgranular quartz in AM4-01 sample, and shows a weak orientation. Calcite is invariably twinned, with twin lamellae interrupted or deformed. Quartz is abundant, commonly found as rounded inclusions in calcite. Muscovite, plagioclase, rare Fe oxides and apatite are observed in the four samples. In AM4-01 sample, dolomite is subordinately present; the accessory minerals include also phlogopite flakes, fibrous talc, and anhedral tremolite crystals. The fine grained marble sample (AM2-03) shows homeoblastic granoblastic texture and sutured grain boundaries. Dolomite is dominant, associated with subordinate calcite; both carbonate minerals are commonly twinned. In AM203 sample the accessory minerals composition is similar to other specimens, except for the presence of chlorites and the absence of muscovite. Viana do Alentejo – The investigated marbles are coarse grained, with MGS ranging from 2.2 mm (sample VA3-03) to 5.5 mm (sample VA3-02). Among them, three samples show a heterogranoblastic texture of the mortar type (Fig. 5e) with crystal orientation in VA3-03 sample; the others are characterized by homeoblastic to heteroblastic texture (samples VA2-01/06 and VA3-02). Calcite is the main constituent, is characterised by straight, curved or

5.1.3.2. Optical microscopy and scanning electron microscopy investigations. Bencatel – The investigated samples from Bencatel have a heteroblastic texture accompanied by weak to strong iso-orientation (Fig. 5f); grain boundaries are embayed, sutured, sometimes straight and curved. BE3-02 and BE6-01 samples are fine grained (MGS of 0.8 mm), whereas BE3-01 and BE4-01 samples show a coarser grain size (MGS ranges from 2 to 2.5 mm). Calcite is the dominant mineral, sporadically associated to dolomite. Quartz is always observed, variously mixed with other accessory minerals like muscovite and phlogopite (BE3-02), chlorite (samples BE2-01 and BE3-02), rare plagioclase (BE3-02), Fe and Ti oxides. Veins of fine grained calcite are evident in BE3-02 sample. Borba – The petrographic investigation allowed outlining textural and mineralogical differences between the five samples analysed. BO1-01, BO3-03 and BO3-05 samples are coarse grained (MGS range from 2 to 3 mm), characterised by homeoblastic to heteroblastic texture and by a weak orientation of calcite grains in BO1-01 samples. Calcite show straight and curved grain boundaries and generally has rounded inclusions of quartz. K-feldspar (BO1-01 and BO3-05), muscovite, chlorite (BO3-03), phlogopite (BO3-05) and few crystals of apatite, opaque minerals and titanite were identified as accessory minerals. Mica and opaques (presumably pyrite) are mainly observed in veins or thin layers in BO1-01 sample. Conversely, the BO2-01 sample is uniformly fine grained (MGS of 1.5 mm) and characterised by homeoblastic texture of the granoblastic polygonal type, with straight, curved or weakly embayed calcite boundaries (Fig. 5g). The non-carbonate fraction consists of quartz, sporadic muscovite and phlogopite, few grains of Fe sulphide, and apatite. The other specimen (BO3-01) is characterised by heterogranoblastic texture, embayed grain boundaries and MGS of 1 mm. BO3-01 sample mostly consists of dolomite, accompanied by a lower content of calcite, quartz, muscovite and few apatite. eschweizerbart_xxx

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Estremoz – The four specimens analysed (EZ1-02, EZ104, EZ3-01 and EZ4-03) show a pure calcitic composition, homeoblastic texture of granoblastic and polygonal type (Fig. 5h), with straight, curved and rarely sutured (sample EZ3-01) rims. The MGS ranges from 1.7 to 2.4 mm. The non-carbonate fraction is made up of rounded quartz grains, flakes of muscovite (EZ1-02/04 and EZ3-01), frequently observed in veins together with K-feldspar (EZ301), and a small amount of Fe and Ti oxides. A few apatite and titanite crystals have also been detected by SEM-BSE. Dolomite veins were observed in EZ1-02. 5.1.4. Archaeological marbles 5.1.4.1. XRPD investigations. Two different types of marbles were identified on the basis of the dominant calcite or dolomite composition. Two artefacts in particular (samples T6 and T28) are made of dolomitic marble, with a small amount of calcite. The results obtained on the other artefacts highlight the dominant calcitic composition, associated to minor dolomite (sample T4), quartz (samples T4, T5, and T20) and muscovite (sample T5). 5.1.4.2. Optical microscopy and scanning electron microscopy investigations. In the T6 and T28 specimens, dolomite is associated to rare calcite (sample T6), muscovite, apatite and opaque minerals detected only by SEM-BSE. Both samples exhibit a homeoblastic, granoblastic to polygonal (sample T28) fabric, embayed to straight grain boundaries (Fig. 5i) and MGS that can reach up to 3.5 mm. The group of archaeological finds (samples T4, T5, T14, T18, T20, and T30) made of calcitic marbles show similar petrographic features, as they are characterised by homeoblastic/heteroblastic texture of granoblastic and mortar (sample T5) types. T14 and T20 specimens have a coarse grained microstructure with MGS values ranging from 2 to 4.4 mm (sample T14, Fig. 5l) and are characterised by a weak orientation of the grains. Calcite has curved, embayed or, rarely, sutured (sample T18) rims. Calcite always shows polysynthetic twinning, sometimes with curved or deformed lamellae. Subordinate dolomite is found only in T4 and T5 specimens. Among the noncarbonate phases, quartz is common as rounded inclusions in calcite or forming micro-granular aggregates. Flakes of phlogopite or muscovite, isolated anhedral crystals of plagioclase (samples T4 and T20), tremolite (sample T5), rare apatite individuals, pyrite, titanium oxide (samples T4 and T18), titanite (sample T4 and T5), and graphite are identified as accessory minerals.

Fig. 6. d18O-d13C isotopic diagram of (a) Betic chain marbles; (b) Ossa Morena Zone and Estremoz marbles, compared with marble artefacts signatures (*).

been plotted separately. The d13C and d18O values of the Betic chain marbles range from 1.6 to 4.3 % and 8.8 to 0.3 %, respectively. Among the Malaga marbles, Alhaurin de la Torre ones have a uniform and distinctive carbon and oxygen composition. Conversely, the isotopic fields of Mijas and Macael quarries partly overlap (Fig.6a), as the two groups of marbles have rather heterogeneous oxygen isotope composition. The Ossa Morena quarries (Alconera, Almadeń de la Plata, and Viana do Alentejo in Fig. 6b)

5.2. Stable carbon and oxygen isotope composition In order to discriminate samples from different quarry sites and to compare the archaeological artefacts with the raw material, scatter plots d13C vs. d18O were used (Fig. 6). Data pertaining to the Betic Chain marbles (Fig. 6a) and Ossa Morena/Estremoz Anticline marbles (Fig. 6b) have eschweizerbart_xxx


defined fields between 0.7 to 3.5 % d13C values and 12.3 to 5.3 % d18O values. Viana do Alentejo samples cover the broadest ranges, as the d13C range include both positive, up to 3.1 % in VA4-01 sample, and negative values (VA1-01 and VA1-05). The Alconera marbles are characterised by more negative d18O values (lower than 9.1 %), while d13C is similar to other Ossa Morena and Estremoz Anticline samples. The isotopic composition of the Estremoz quarry is quite homogeneous with the exception of few samples that have lower d18O and d13C values (Table 1). The d13C vs. d18O fields defined by the marbles from Almadeń de la Plata, Bencatel, Borba, Estremoz and Viana do Alentejo largely overlap in the region between 9 to 6 % d18O and 0.5–3 % d13C (Fig. 6b). However, Almadeń de la Plata samples show some differences in their carbon isotope composition and are generally characterised by d13C values higher than 2 %, up to 3.3 %, except for two samples (AM1-04 and AM4-04); Viana do Alentejo, Bencatel, Borba and Estremoz have d13C values lower than 2 %. The group of T4, T5, T14, T18, T20, and T30 artefacts exhibit rather uniform stable isotope compositions (Table 2), especially for d18O varying from 6.0 to 5.7 %, while d13C ranges from 1.9 to 3.5 % . The two dolomitic marble artefacts T6 and T28 have 4.9 and 3.4 % d18O, and 1.9 and 3.1 % d13C values, respectively.

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characterized by a strong orientation of calcite grains. The Almadeń de la Plata samples are typically coarse grained, and show a heteroblastic mortar texture, while Estremoz marbles are granoblastic with a uniform finer grain size. Borba specimens have a more granoblastic and polygonal texture as the Estremoz marbles. Differences between the two marble groups are observed in the MGS and the oriented structure that may occur in Borba specimens (e.g., sample BO1-01). Even though the new database confirms the main textural and mineralogical features reported in previous studies on similar marbles (Lapuente & Turi, 1995; Lapuente et al., 2000; 2002; Morbidelli et al., 2007), some discrepancies were found with respect to the maximum grain size values and textural description reported by Lapuente & Turi (1995) and Lapuente (2000). The investigated samples of Almadeń de la Plata are predominantly coarse grained with MGS higher than 2 mm, while literature generally reports MGS values less than 2 mm. Regarding Almadeń de la Plata marbles, the structural and textural heterogeneities, even within the same quarry, might be explained by the complex geological history of the area (Espinosa et al., 2002). The existing data on Viana do Alentejo indicate that marbles from the area are fine to medium grained (MGS less than 2 mm) and have homeoblastic polygonal texture; results from this study indicate that MGS may also reach higher values and heteroblastic mortar texture can also be observed. As a general result, the mineralogical database presented in our study shows a greater compositional variability, such as the sporadic presence of dolomitic marbles in the Ossa Morena (Almadeń de la Plata, Borba) and the Betic chain (Macael) collection. The results of isotope analyses are more relevant as they help placing more constrains on the stable isotope ranges of the single quarries. The new data on Mijas, Viana do Alentejo and Estremoz, which are all characterised by some lower d13C and d18O values, led to the enlargement of their geochemical clusters. For what concerns the Alhaurin de la Torre, Alconera, and Macael quarries, isotopic analyses appreciably increased the number of case series.

6. Discussion Samples collected from Alhaurin de la Torre and Mijas are homogeneous from a mineralogical point of view, as they consist almost exclusively of dolomite. However, the maximum grain size and texture are useful parameters for their distinction: Mijas marbles are generally characterised by a coarse grained microstructure (MGS 3 mm), while Alhaurin de la Torre presents finer grained marbles (MGS of 1.8 mm). The stable isotope composition provides an additional element to distinguish them from each other. The textural and accessory mineral content reveal differences between Malaga samples and the other sporadic dolomitic marbles identified among Macael, Almadeń and Borba specimens. The anasol type marbles collected at Macael are characterised by an oriented and fine-grained structure, as well as by the presence of mica and opaque minerals. Chlorite and muscovite, found in Almadeń de la Plata and Borba specimens respectively, are absent in Malaga marbles. Among the calcitic marbles, Viana do Alentejo stands out for the larger content of accessory minerals, the coarser grain size, and a broad range of d13C values, while Alconera has a quite distinctive isotopic composition (Fig. 6b). The isotope analyses alone do not allow for a clear distinction between Ossa Morena and Estremoz Anticline marbles, because they share a similar composition and their isotopic fields partially overlap (Fig. 6b). This issue can be addressed by taking into account their petrographic features. Marbles collected from Bencatel are

6.1. Archaeological artefacts compared to Iberian marbles On the basis of the mineralogical and petrographic investigations, two groups were identified. The first consists of two archaeological finds, a fragment of an inscription (sample T6) and a slab (sample T28), made of dolomitic marbles. These artefacts have been compared both with data from this study and those already published on other dolomitic marbles from Malaga district (Lapuente et al., 2002), which also included the Coin, Monda and Alhaurin el Grande quarries. The T6 and T28 artefacts have a stable isotope signature similar to the Mijas values. The petrographic features, such as the maximum grain size (.2 mm), the granoblastic texture and the shape of dolomite boundaries, strengthen the hypothesis that the marbles originated from this quarry. eschweizerbart_xxx

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The other group is composed of fragments of white and slightly pinkish marbles employed to produce a mortar (sample T14), a pestle (sample T18), a basin (sample T20), and two inscriptions (samples T4 and T5). These materials are macroscopically similar to some of the Ossa Morena and Estremoz Anticline varieties. The stable isotope values of T14, T18, T20 and T30 samples fall in the Almadeń de la Plata d13C vs. d18O field (Fig. 6b), while those of the other artefacts fall into the overlap region of Almadeń de la Plata, Bencatel, Borba, Estremoz and Viana do Alentejo. However, the mineralogical and petrographic features, such as the abundance of quartz, muscovite and sporadic presence of tremolite, the heterogranoblastic fabric, the MGS (2–3 mm), the presence of calcite twins, all seem to indicate an Almadeń de la Plata provenance.

The other archaeological objects are made of white or slightly pinkish marbles. Similar stones can be found in most of the quarries sampled in Ossa Morena Zone and the Estremoz Anticline. The majority of the examined artefacts share a stable-isotope signature similar to Almadeń de la Plata. The petrographic observation (maximum grain size, texture and mineralogical assemblage) point to this origin as well, thus rendering it most probable. The multi-analytical approach adopted here provides a set of diagnostic parameters which can be used to define reference groups. Such an approach has proven fundamental for the archaeometric study described here, and will also be of outstanding importance for future provenance studies of archaeological marble finds in the western Mediterranean region.

7. Conclusions

Acknowledgements: The authors wish to thank Dr. Ulrich Schu¨ßler, and the two anonymous reviewers for the careful revisions and checking of the manuscript. Their comments and suggestions greatly improved the paper.

Nine quarries in Spain and Portugal, known and exploited since Roman times for the extraction of white and coloured marbles, have been considered as possible sources of the stones used in Thamusida, an ancient town of the Mauretania Tingitana province. A total of 135 marble specimens were collected from the Betic Chain (Alhaurin de la Torre, Mijas and Macael), Ossa Morena Zone (Alconera, Almadeń de la Plata, Viana do Alentejo) and Estremoz Anticline (Bencatel, Borba, Estremoz), to be compared with eight Roman marble artefacts found at the Moroccan archaeological site. Mineralogical, petrographic and stable isotope study of the raw materials allowed us to implement the existing database on Iberian marbles. The results of the mineralogical investigation highlights the pure dolomitic composition of the Alhaurin de la Torre and Mijas marbles, which can be distinguished based on textural features (e.g., MGS values) and stable-isotope composition. The same features helped to differentiate them from other sporadic dolomitic marbles identified among Macael, Almadeń de la Plata, and Borba specimens. Among Ossa Morena marbles, those of Viana do Alentejo stand out due to the highest MGS in the entire collection, and for the higher content of noncarbonate fraction. The isotope data allow drawing a clear distinction between the marbles from Alconera and those from the other sites located in Ossa Morena Zone and the Estremoz Anticline, but seem to be less discriminatory for Almadeń de Plata, Bencatel, Borba, Estremoz and Viana do Alentejo. Hypotheses on the origin of the Thamusida marble artefacts can be formulated only by taking into consideration all the mineralogical, petrographic and geochemical features combined together. Both the T6 and T28 archaeological finds are made of dolomitic marbles and exhibit the typical textural features and stable isotope composition of Mijas materials. Such an agreement in the data points toward the Spanish quarry as the most probable source of this stone, used for an inscription dating back to the 2nd and 3rd century AD.

References Alonso-Chaves, F.M., Soto, J.I., Orozco, M., Kilias, A.A., Tranos, M.D. (2004): Tectonic Evolution of the Betic Cordillera: An Overview. Bull. Geol. Soc. Greece, 36, 1598–1607. Alvarado, M. (1980): Introduccioń a la Geologıá de Espanã. 26th Int. Geol. Congress, Boletıń Geolo´gico y Minero, XCI-I, 1–65. Andreo, B. & Sans de Galdeano, C. (1994): Structure of the Sierra de Mijas (Alpujarride Complex, Betic Cordillera). Annales Tectonicae, 8, 23–35. Antonelli, F. & Lazzarini, L. (2004): La caratterizzazione mineropetrografica e geochimica delle rocce. in ‘‘ Pietre e marmi antichi: natura, caratterizzazione, origine, storia d’uso, diffusione, collezionismo’’, L. Lazzarini, ed., CEDAM, Padova, 33–45. Antonelli, F., Lazzarini, L., Cancelliere, S., Dessandier, D. (2009): Volubilis (Meknes, Morocco): Archaeometric study of the white and coloured marbles imported in the Roman age. J. Cultu. Herit., 10, 116–123. Attanasio, D., Brilli, M., Bruno, M. (2008): The properties and identification of marble from Proconnesos (Marmara island, Turkey): a new database including isotopic, EPR and petrographic data. Archaeometry, 50, 747–774. Azor, A., Gonza´lez Lodeiro, F., Simancas, J.E. (1994): Tectonic evolution of the boundary between the Central Iberian and Ossa-Morena zones (Variscan belt, southwest Spain). Tectonics, 13, 45–61. Barros, E., Carvalhosa, A., Zbyszewski, G. (1972): Noticia explicative da Folha 40-C ‘‘Viana do Alentejo’’. in ‘‘Carta Geologica de Portugal 1:50.000’’, Direcçao-geral de minas e Serviços geologicos, Lisboa. Cabral, J.M.P., Maciel, M.J., Lopes, L., Lopes, J.M.C., Marques, A.P.V., Mustra, C.O., Carreira, P.M. (2001): Petrographic and isotopic characterization of marbles from the Estremoz Anticline: its application in identifying the sources of Roman works of art. J. Iberian Archaeol., 3, 121–128. eschweizerbart_xxx


869

Lapuente, M.P., Turi, B., Blanc, P. (2000): Marbles from Roman Hispania: stable isotope and cathodoluminescence characterisation. Appl. Geochem., 15, 1469–1493. Lapuente P., Martinez, M.P., Turi, B., Blanc, Ph. (2002): Characterization of dolomitic marbles from the Malaga Province (Spain). in ‘‘ASMOSIA 5, Interdisciplinary studies on ancient stone’’, J.J. Hermann, N. Herz, R. Newman, eds., Archetype, London, 152–162. Lazzarini, L., Moschini, G., Stievano, B.M. (1980): A contribution to the identification of Italian, Greek and Anatolian marbles through a petrological study and the evaluation of Ca/Sr ratio. Archaeometry, 22, 173–183. Moens, L., Roos, P., De Rudder, J., De Paepe, P., Van Hende, J.,Waelkens, M. (1988): A multimethod approach to the identification of white marbles used in antique artefacts. in ‘‘Classical Marble: Geochemistry, Technology, Trade’’ N. Herz and M. Waeklens, eds., Kluwer Academic Publishers, Dordrecht, 243–250. Morbidelli, P., Tucci, P., Imperatori C., Polvorinos, A., Preite Martinez, M., Azzaro, E., Hernandez, M.J. (2007): Roman quarries of the Iberian peninsula: ‘‘Anasol’’ and ‘‘Anasol’’-type. Eur. J. Mineral., 19, 125–135. Nogales, T., De La Barrera, J.L., Lapuente, P. (1995): Marbles and other stones used in Augusta Emerita, Hispania. in ‘‘ASMOSIA 4, Archeomateriaux. Marbres et autres roches’’ M. Schvoere, ed., Presses universitaires de Bordeaux, Talence, 111–116. Origlia, F., Spangenberg, J., Turbanti Memmi, I., Papi, E. (2009a): A provenance study of marbles from the Roman town of Thamusida, Mauretania Tingitana, Morocco. in ‘‘IX ASMOSIA International Conference Abstract Volume’’, Institut Catala` d’Arquelogia Cla`ssica, Tarragona, p. 48. Origlia, F., Spangenberg, J., Turbanti Memmi, I., Papi, E. (2009b): A Provenance study of marbles from the Roman town of Thamusida (Mauretania Tingitana, northern Morocco). Geochim. Cosmochim. Acta, 73, A974. Simancas, J.F., Martinez Poyatos, D., Expo´sito, I., Azor, A., Gonza´lez Lodeiro, F. (2001): The structure of a major suture zone in the SW Iberian Massif: the Ossa-Morena/Central Iberian contact. Tectonophysics, 332, 285–308.

Capedri, S., Venturelli, G., Photiades, A. (2004): Accessory minerals and d18O and d13C of marbles from Mediterranean area. J. Cult. Herit., 5, 27–47. Carvalho, J.F., Henriquesa, P., Faleá, P. (2008): Decision criteria for the exploration of ornamental stone deposits, application to the Portuguese marbles of the Estremoz Anticline. Int. J. Rock Mech. Mining Sci., 45, 1306–1319. Coleman, M. & Walker, S. (1979): Stable isotope identification of Greek and Turkish marbles. Archaeometry, 21, 107–112. Espinosa, J., Villegas, R., Ager, F., Go´mez Tubıó, B. (2002): Estudio Arqueome´trico Mediante Ana´lisis Petrogra´fico y Quı´mico de Dos Esculturas del Museo de Rıó Tinto (Huelva). in ‘‘1 Congreso Grupo Espanõl del Iic: Conservacioń del Patrimonio’’, Valencia, 335–341. Expo´sito, I., Simancas, J.F., Gonza´les Lodeiro, F., Bea, F., Montero, P., Salman, K. (2003): Metamorphic and deformational imprint of Cambrian – Lower Ordovician rifting in the Ossa Morena Zone (Iberian Massif, Spain). J. Struct. Geol., 25, 2077–2087. Giorgetti, G., Gliozzo, E. (2009): I materiali lapidei. in ‘‘Sidi Ali Ben Ahmed, Thamusida 2. L’archeometria’’, Quasar. Roma, 59–72. Gliozzo, E., Dalconi, C., Cruciani, G., Turbanti Memmi, I. (2009): An approach to the investigations of mortars: the application of the Rietveld method. Eur. J. Mineral., 21, 457–465. Gliozzo, E., Damiani, D., Camporeale, S., Memmi, I., Papi, E. (2011a): Building materials from Thamusida (Rabat, Morocco): a diachronic local production from the Roman to the Islamic period. J. Archaeol. Sci., 38, 1026–1036. Gliozzo E., Kockelmann, W., Bartoli, L., Tykot, R.H. (2011b): Roman bronze artefacts from Thamusida (Morocco): Chemical and phase analyses. Nucl. Instrum. Meth. Phys. Res. B., 269, 277–283. Gliozzo, E., Cavari, F., Damiani, D., Memmi, I. (2011c): Pigments and plasters from Thamusida (Rabat, Morocco). Archaeometry doi: 10.1111/j.1475-4754.2011.00617. Gorgoni, C., Lazzarini, L., Pallante, P., Turi, B. (2002): An updated and detailed mineropetrographic and C-O stable isotopic reference database for the main Mediterranean marbles used in antiquity. in: ‘‘ASMOSIA 5, Interdisciplinary studies on ancient stone’’, J.J. Hermann, N. Herz, R. Newman, eds., Archetype, London, 115–131. Lapuente, P. & Turi, B. (1995): Marbles from Portugal: petrographic and isotopic characterization. Sci. Technol. Cultur. Herit., 4, 33–44.

Received 10 February 2011 Modified version received 24 June 2011 Accepted 1 August 2011

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