Integrated archaeological and geophysical survey for searching the Roman temple of Augustus in...

8/9/2019 Integrated archaeological and geophysical survey for searching the Roman temple of Augustus in Tarragona, Spain

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Centro Regionale per la Progettazione ed il Restauroe per le Scienze Naturali ed Applicate ai Beni Culturali

Scienza e Patrimonio Culturale nel Mediterraneo

DIAGNOSTICA E CONSERVAZIONE

ESPERIENZE E PROPOSTE PER UNA CARTA DEL RISCHIO

Atti del m convegno internazionale di studiLa materia e i segni della storia

Palermo 18-21 ottobre 2007

REGIONE SICILIANA

Assessorato dei Beni Culturali ed Ambientali e della Pubblica Istruzione

Dipartimento Beni Culturali ed Ambientali ed Educazione Permanente

Palermo


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INDAGINI E DIAGNOSTICA - terza parte

256 Radiologia versus diagnostica per immagini nell'arteG. Salerno

266 La riflenografia infrarossa ad alta risoluzione: un unico processo dalla ripresa alla stampa dei riflettogrammi.C. Perez Garda, P. lneba T'amari/,]. Perez Miralles, L. Pini, G. Valagussa

269 Physical identification of precious artefacts: their sonic imprintP. L. Cosentino, P. Capizzi, G. Fiandaca, R. Martorana, P. Messina, I. Razo Amoroz

277 Integratecl archaeological and geophysical survey for searching the Roman of Augustus tempIe in Tarragona,Spain

A. Casas, P.L. Cosentino, Y Diaz, E. Garcia, M. Himi, M. Lafuente, R. Mar/orana, J.M. Macias, J. Menchn, A.Murnoz, R. Sala, 1, Teixell

284 Indagini archeopalinologiche in Sicily at Taormina, Piazza Armerina and MoziaF Terranova, C. A. Accorsi, M. Bandini Mazzanti, A. M. Mercuri, P. T0171,E. Manicardi, /VI. C. Montecchi, L.Olmi, R. Rinaldi, A. Valenti, F Benassi, P. pensabene, S. Tusa

295 Materia e segni della storia sostanzialmente e formalmente uniti: alcuni casi di studioS. Lorusso, C. Malteucci, A. Na/ali, S. Tumidei

304 Caratterizzazione spettrale e visiva dei materiali antichi per l'ottimizzazione della progettazione iIIuminotecnicaF Gugliermelti, F Bisegna, L. Monti

INDAGINI E DIAGNOSTICA - quarta parte

314 PRErAZIONI di Claudia Sorlini

316 On the efficiency of biocides and cleaning treatments in restoration works of subterranean monumentsE. Aka/ova, M. Roldan, M. Hernandez-Marine, ].M. Gonzalez, C. Saiz-}imenez.

323 A non-invasive approach to the polyphasic study of biodeteriogenic biofilms at St Agatha crypt and catacombsat Rabat, Malta.G. Zammit, F De Leo, C. Urz~ P. Albe1tano

328 Studio della colonizzazione microbica di tessere mosaicali mediante tecniche fisiche e molecolariF. Palla, S. Drago, M. R. Di Pierro, A. Lanza, G. Morici

333 Express-method of estimation of biocide properties of different materials and substances and application ofnanotechnology in biocide treatmentM. Dmitrieva, N. Reb11kova

337 Colonization by actinobacteria in the cave of Dona Trinidad (Malaga, Spain)F Stomeo,J.M. Gonzalez, C. Saiz-jimenez


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INTEGRATED ARCHAEOLOGICAL AND GEO-

PHYSICAL SURVEY FOR SEARCHING THEROMAN TEMPLE OF AUGUSTUS IN TERRAGO-

NA, SPAINA.Casas , PL.Cosenlino, Y Dfaz , G. Fiandaca, E. Garcfa, M. J-limi, M.

(jilenle, R. Mm1orcma,j. M lvlacfas,j. Menehon, A. i\;/1I/10Z, R. Sala,

l. 'f'eLxell

INTRODUCTION

Tarragona's cathedral is located on the highest topographic pIace of the city. Romans occupied this spacesince the III century B.e. and converted it on a militarycamp since the wars against the Carthaginian, com

manded by Hannibal, took pIace in the IberianPeninsula. Subsequently, Tarraco was the pIace wherethe Roman soldiers arrived to conquer Hispania.

Fig. 2 - Front of the Gothic Cathedral of Tarragona.

INDAGINI E DIAGNOSTICA

Fig. 1 - !dealized illustration ofthe Au-gustus tempie in a coinof Tiberian's emperor age.

The evidence of this activity is the Roman wall that hasbeen preserved and stili surrounding the historic centerof Tarragona CAqllilll, 2000),

After getting the rank of provincial capital, Tarraco started a set of urban transformations presided over the hillby a great sacred enclosllre that surrollnded the tempIe

devoted to the emperor Augllst. It is worth noticing that

Fig. 3 - Plant of the Gothic Cathedral overdrawn are assllmed the external structllre of sacred area (dots).


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Il S C I E N Z A E P A T R I M O N I O C U L T U I{ A L E [) E L M E [) I T E R R A N E Othe Roman cult was carried out outsicle of the temples

ancl not insicle.Since the encl of the IV centll1Y A.C. (the Christian religionwas then the official one of the Roman Empire), theemperors ordered a graduai legislative process thatfavored the replacement of the pagan cults with the

Christian ones. At this time, the site undelwent manychanges in urban planning and ideological reassessments.During the V ancl VI centuries, the urban characteristics

of this zone changecl radically with residential spaces

inciuding open-air waste clumps-ancl spaces for offidalrepresenta tions both civil and religious.In this framework also the Meclieval Catheclral was erect

ecl with the Bishopy ancl burial grouncl spaces.

At the beginning of the VIII centll1Ythe Islamic invasion hada period of decline far more than four centuries unti! theclefinitive restoration of the metropolitan bishop and the

starting of the new meclieval cathedral in the micldle of the

XII centll1y. Since this time, the Catheclral has dominated theskyline of Tarragona and probably concealing in the subsoilsome of the answers we need to recognize ancl unclerstancl

the historical evolution of the city (Munoz, 2001).The usefulness of geophysical techniques (e.g., dc current, electromagnetic, ancl magnetic methocls) for archae

ological investigation is well known :mcl has been repoltecl in many papers, for instance Casas et al. (1995), Dabaset al. (1993), Prez-Garcfa (2000), Carrara et al. (2001),Negri ancl Leucci (2006) . Therefore , as the la test archaeo

logical researches from Macfas et al. (2007) assumed thatthere are remains of older builclings uncler the MeclievalSee, related to the Roman emperor, a geophysical surveywas consiclerecl - also taking into account the potential

interest of the remains. The objective was to obtain a firstpicture of the archaeological remains existing in the subsoil without disturbing both the religious cult ancl the cul

turaI visits to the tempie.On the other hancl, the obtained results will be consicl

erecl of interest to clefine some strategies in the futurefourth phase of Director Pian for the Cathedral of

Tarragona (Figuerola et aL, 2002). The aim of the geophysical survey is to get as much information as possibleon the structure and composition of the materials existing

in the subsoil and, particularly to cletect remains of foun

dations of previous builclings. For this reason, a cletaileclgeophysical mapping has been concluctecl.

METHODOLOGIES

The geophysical methocls used in this stucly area arebased on the cletection of variations in the electric ancl

electromagnetic propelties of the subsoil and the use of

these data for identifying altifacts ancl clistinguishing themfrom the natural variations of the subsoil. EI{T,FDEM ancl

GPR were appliecl.Geophysical investigations play an important role in

defining shallow subsurface structures. In particular,their application is a non-clestructive and cost effective

way to locate buried archaeological structures in the surveyecl areas. Taking into account prececling experiences

in other similar surveys three complementary geophysi

cal methods were plannecl:-Electrical resistivity tomography (EI{T)-Frequency domain electromagnetics (FDEM)-Grouncl probing raclar (G PR)

The first method (ERT) aimecl to recognize the geometrical characteristics of the structures of the subsoil as a

function of the electrical resistivity of the materials that

constituted the subsoi!, which in tum depends on theporosity, ciay content ancl water content.This methocl was carried out using two clifferent multi

channel resistivity meters. An Iris Syscal Plus with 48

channels for recording 2]) sections ancl a MRS256 Systemfrom G F Instruments with 350 channels for 3D moclels. In

both cases, the proceclure for clata acquisition was to

apply a DC electrical current by means of two electroclesand to measure the potential generatecl over two other

electrocles placed along profiles (2D-ERT) or regular gricls

(3D-ERT) spacecl one meter apan over the pavement. Inorder to cany out the bi-dimensional profiles, stainlesssteel flat-base electrocles were used, similar to those useclby Athanasiou et al. (2004), while to clecrease the contactresistances a concluctive gel was placed between the

metallic electrocles ancl the soil pavement; with this strategy the contact resistances were set below 10 kohms.

--....-.-/


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IlSCIENZA E PATRIMONIO CULTURALE DEL MEDITERRANEO

resistances. A good choice was the use 01' disposable Foam

AgiAgCl ECG electrocles (Cosentino et aL, 1999), The largeamount 01' data, produced by multielectrode systems,

requires automated data handling and processing.l'o ohtain a more accurate picture 01' the suhsurt~lCe it is

necessmy to invel1 the apparent resistivity data . The inversion method was based on the smoothness-constrained

least square method. In this method, the subsurface isd ivided into cells 01' fixed dimensions l 'or which the resistivit ies

are adjusted iteratively until an acceptable agreement

between the input data and the mode! responses isachieved. It is based on a non-linea l' optimization techniqueby least-squares fi tting (Loke and Barker, 1996). During the

inversion process the root mean square value 01' the ditTerence between experimental data and updated mode lresponse is used as a criterion to assess the convergence.The second method, EM conductivity mapping, is based on

the application 01' a variable primalY field by means 01' a

loop measuring the resulting fielel in another loop. In spite01' the instrument used, an EM138 l'rom GF Instruments,gave reliable results in the sectors 01' the cathedral elose tothe main door.

ll1is effect has been justified as a result 01' the high electri

cal resistivity 01' the subsoil in most sec tors 01' the cathedralwhich inhibit the elec tromagnetic induction phenomena.For this reason this technique was discarded to concentrate

the effot1s on the other methods which provided more significant result


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INDAGINI E DIAGNOSTICA.

Dopth Ihrlltion 5 Abs. orror : 2.9 t9.9 8.09.1259.676

l . 3 '1

2.152.623.133.69

1f.31

16.0 32.0 '10.9

,..

Unit electrode spllcing 0.500 .

Unit eIectrode spaeing 9.589 .

..19.92.9

Inverse "odel Resistivi ty Section

____.D.~.CO _59.9 811.5 1113 21f1 1f08 689 1165 1969Resistivity in oh.

2.152.623.133.69

If .31

Invor Hodei Reoioti vity Soction_____ D_C __ o _9.9 8'1.5 1'13 2'11 '108 689 1165 1969

Rooiotivity in oh.Depth Iteretion 5 RHS error : 2.1f 7-

0.0 8.9 16.0 21f.00.1250.676

1. 31f

Dopth Iteretion 5 RHS error : 1,16 7-0.0 8.9

0.1250.676

1. 31f

2.152.623.133.69

1f.31

16.0 21f.0 32.9 119.8 ..

Inverse "odel Resistivity Seetion_____ DC~.CD ._59.9 811.5 11f3 21f1 IIG8 689 1165 1969

Resistivity in oh. Unit eleetrode spacing 9.599 .

'"Invorse Hodol Rosioti vi ty SocHon_____ D_~ __ D _

5e.a 811.5 1113 21f1 1198 689 11651969Rooistivity in oh .

Dopth Itoretion 'I Abo. orror : 9.811 t9.9 8.9

9.1259.676

l . 311

2.152.62

3.133.69'1.31

16.9 21f.9 32.e 110.0

Unit oloctrodo opaeing e. 5ee .

Fig. 8- Inverted 2D sections of the electrical resistivity tomographies record ed along the cathedral showing the almost rectan-gular resistive body


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SCIENZA E PATl{IMONIO CULTURALE DEL MEDITERRANEO

Using a GPR analysis, the exisrence 01' an archaeological stratigraphy is asslImed and the analysis 01' the datasuggested clepth alterations or differences between thecentraI ancl the lateral naves, as well as between thecentraI nave ancl the main entrance to the medieval tem

pie.

A generai characteristic al' the surveyecl area is the goodpenetration 01' the electromagnetic energy, 100 ns corresponcling to a depth 01' about 4.0 m when a mean veloc

ity vaille of 0.08 m/ns is lIsed. This is essentially due tothe physical characteristics 01' the materials lIsed far theconstruction 01' the tempie (limestone), which have highresistivity values and therefore dissipate the EM energyonly slightly.In spite of the clarity 01' some of the described structures, it musr be pointecl out that their vertical projections are irregular. This wOlllcl indicate a reuse 01' preex

isting elements for the erection of the bllilcling' ancl an

irregular conclition 01' preservation.

CONCLUSIONS

The effectiveness or the different geophysical methoclsin mapping the archaeological features in Tarragona'sCatheclral has been confirmecl. The 20 ancl 30 moclelsobtainecl uncler the Catheclral 01' Tarragona will play an

important role in archaeological investigations sincethey furnish a synthetic view 01' the location ancl sizes 01'the most important structures in the area.The results indicate that the lise 01' flat-base electrocles

insteacl of standard pointecl electrocles - is a velY gooclalternative in sites where the latter can not be nailed. It

provicles the aclvantage al' fully nonclestructive application and the expansion 01' using geoelectrical methocls inenvironments that otherwise we woulcl never consicler.

The structure of the tempIe basement seems to be

revealecl both using 20 ancl 3D electrical imaging techniques. Furthermore, the anomalous areas cletectecl by

the clifferent geophysical techniques are velY consistent.

ti

resistivity (ohm.m)-y-.,~100 200 300 400 500 600 700 800 900 1000

Fig. 9- 3D image of the high resistive anomaly detected under the centrai paI1 of the Cathedral.


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ACK1\OWLEl)GEME1\TS

The allthors are indebted to jallme Plljol (Archbishop ofTarragona's Cathedral), josep Martl (Diocesan Delegate forHeritage), Francesc Gallart (Dea n of the Bishop's Chapter) andIsabel Rod (Oirector of the Catalan Institllte for ClassicalArchaeology).

REfEI{ENCES

AQUILUI~, X. (2004) Arqllitectllra oficial, Dllpr, X. (ed),'l'arragona. Colonia fulia Urhs 'l'riumphalis 'l'arraeo, Las

Capitalesprouineiales de l-fi~pania 3, Roma, 41-53.ATHANASIOU, E., P. TSOURLOS, G. TSOKAS, C. PAPAZACHOSANO G. VARGEMEZIS (2004) Nondestrllctive DC ResistivitySllrveying Using Flat Base Electrodes.Proeeedings 77th NearSlIIfaee Geophysies iHeeting, Palermo (Italy).CARRARA, E., CARROZZO, M.T, FEDI, M., FLORIO, G.,NEGRI, S., PAOLETTI,v., PAOLILLO, G., QUARTA,T, RAPOLLA, A. ANO ROBERTI, N. (200]) Resistivity and Radar sllrveysat the Archaeological site of Ercolano. lournal oIEnuironmenlal and Engineering Geophysies , 6 (3): 123-132.CASAS, A., PINTO,v., RIVERO, L., CAMERLINK, c., DABAS,M. (995) Urban Geophysics: The case of Cathedrals and otherreligiolls monllments. Proeeedings oI the XX EuropeanGeophysieal Soeie(y GeneraI Meeting, Hambllrg (Germany).COSENTINO P., MARTORANA R. ANO TERRANOVA L.M.(999) The resistivity grid to optimize tomographic 3D imaging.Proeeedings oI the 5th Meeting oi EAEG, European Seetion,1311dapest, Hungary, Em12.DABAS, M., STEGEMAN, c., HESSE, A., jOLIVET, A., MOUNIR,A. ANO CASAS, A. (993) Prospection de la Cathdrale deChartres. BuI. Soc. Areh. d'Ellre el Loir, 36, 5-24.FIGUEROLA, j., GAVALOA, j., MENCHON, j., TEIXELL, I.,MUNOZ, A. ANO MACIAS, jM" (2002) La catedral de Tarragona:obres de restauraci6 i treball arqueolgic", Vll CoUoquiConservar i reslaurm:' arqueologia i arquiteetum. Amies delRomnie. Lambard. Estudis d'art medieval XIV, Barcelona, 75-107.GOODMAN, D., NISHIMURA, Y. ANO ROGERS, j.O. (995)

INDAGINI E DIAGNOSTICA

GPR time-sl ices in archaeological prospect ion.ArehaeologiealPro~jJeetion, 2: 85-89.LOKE JVI.H. AND BARKER R.O. (996) Rapid least-sqllaresinversion of apparent resistivity pseudosections by a quasiNewton method. Geophysieal Pro.\jJeeting, 44: 131-152.MACIAS,j.Ma, MENCHON, j.j., MUNOZ, A., TEIXELL, I . (2007)Excavaciones en la Catedral de Tarragona y su entorno:avances y retrocesos en la investigaci6n sobre el culto Imperial,In: Nogales, T, Gonzalez, j. (eds.), Culto Imperial: polftiw ypoder, Proeeedings oI the fnternational Meeting (Mrida 2006),L'Enna di Bretschneider, Roma, 765-787.MUNOZ, A. (200]) El Cristianisme a l'Antiga 'l'arragona. Delsorfgens a la ineursi6 islmiea. Institut superior de cincies religioses Sant Fructu6s., Tarragona.NEGRI, S. ANO LEUCCI G. (2006) GeophysicaJ investigation ofthe TempIe of Apollo (Hierapolis, Turkey).lournal oIArehaeologieal Scienee, 33: 1505-1513.PREZ-GARCfA, v., CANAS, j.A., PUjAOES, L., CLAPS,J.,CASELLES, O., GARCfA, F. ANO OSO RIO, R. (2000) GPR sllrveyto confirm the location of ancient structures llnder theValencian Cathedral (Spain),101mlal C!/Applied Geophysies 43:167-174.

A. CASAS, Y. OfAZ, M. HIMI, Department of Geochemistry,Petrology and Applied Geology - University of BarcelonaSPAINP.L. COSENTINO, G. FIANOACA, R. MARTORANA,Department of Chemistry and Physics of the Earth andApplications - University of Palermo - ITALYE. GAR.cfA, M. LAFUENTE, R. SALA, SOT - Prospecci6Arqueolgica. Sant Cugat del Valls. Barcelona - SPAINj.M" MACfAS, Catalan Institute for Classica I Archaeology.Tarragona - SPAINj. MENCHON, Municipality of Tarragona. Tarragona - SPAINA. MUNOZ, AND I. TEIXELL, Biblical Museum - Archbishopyof Tarragona - SPAIN

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