10.6092/issn.1973-9494/570
Sicily includes a great variety of lithologies, giving a high complexity to the geologic landscape. Their prevalent lithology is sedimentary. It is well known that rocks of sedimentary origin, compared with metamorphic and volcanic deposits, can be relatively soft and hence fairly easy to model. Nevertheless, this workability advantage is a drawback for Cultural Heritage applications. In fact, these materials show a high porosity, with pore-size distributions that lead to deterioration through absorption of water. In this paper, several sedimentary rocks used in historical Cultural Heritage items of Sicily, from "Magna Graecia" to nowadays, are classified for mineralogical features, chemical composition, and for porosity. Particularly, some samples collected in quarries relevant to the archaeological sites of 41 Agrigento, Segesta and Selinunte will be considered and characterized using integrated techniques (XRD, XRF, NMR and CT). Data on samples obtained in laboratory will be compared with the relevant values measured in situ on monuments of historical-cultural interest of the quoted archaeological places.
application/pdf
1973-9494
570
en
Antonella Maccotta
Conservation Science in Cultural Heritage
Integrated techniques to evaluate the features of sedimentary rocks of archaeological areas of Sicily
Text.Serial.Journal
https://conservation-science.unibo.it/
Articles
2008-02-21
2004-02-28
2015-11-02
25-42
CSCH
Antonella Maccotta
2004
10.6092/issn.1973-9494/570
25
1973-9494
en
42
Integrated techniques to evaluate the features of sedimentary rocks of archaeological areas of Sicily
https://conservation-science.unibo.it/article/download/570/551
I
    NTEGRATED TECHNIQUES TO EVALUATE
    THE FEATURES OF SEDIMENTARY ROCKS
    OF ARCHAEOLOGICAL AREAS OF SICILY

Maria Brai, Antonio Cimino, Giuseppe Raso, Tiziano Schillaci
Dipartimento di Fisica e Tecnologie Relative, Università degli Studi di Palermo
Stefano Bellia
Dipartimento Chimica e Fisica della Terra ed Applicazioni
Università degli Studi di Palermo
Antonio Lo Casto
Dipartimento di Biotecnologie Mediche e Medicina Legale, Università degli Studi di Palermo
Paola Fantazzini
Dipartimento di Fisica, Alma Mater Studiorum Università di Bologna
Antonella Maccotta
Dipartimento di Scienze e Tecnologie Chimiche e dei Biosistemi, Università di Siena




1. Introduction

    This work is addressed to characterize the sedimentary rocks from Sicily used in cul-
tural heritage, classifying them for mineralogical and chemical features as well as for
porosity. Measurements on samples collected in Sicilian quarries will be compared with
data obtained from micro-invasive techniques on monuments of archaeological interest.
    In detail, the chosen techniques were X-Ray Diffractometry (XRD), X-Ray
Fluorescence (XRF), Magnetic Resonance Relaxometry (MRR), Magnetic Resonance                    Quaderni di Scienza della Conservazione
Imaging (MRI).
    Furthermore, adsorption kinetics studies and internal microporosity surveys on sam-
ples, both through X-ray tomography, are performed.
    Many of sedimentary rocks (common limestones, calcarenites, travertines, etc.) have
been used for the building of archaeological-historical items of Sicily, from Magna
Graecia to nowadays.
    The final aim is the understanding of the deterioration processes and the eventual
remedial actions to prevent the decay of the cultural heritage. In particular, our attention
was focused on building materials used for some of the temples of Agrigento, Segesta
and Selinunte. These temples are localized in Western Sicily (fig. 1).

                                                                                               25
M. Brai et al. - Integrated techniques to evaluate the features of sedimentary rocks...




                                                                                                     Figure 1. A map of the archaeological areas of the survey.



                                                                                             The research will be broadened to other cultural heritages belonging to different his-
                                                                                          torical periods, as roman, middle age, baroque and modern era. All the data will be insert-
                                                                                          ed in a relational database to create a knowledge basis to define risk indexes for the mon-
                                                                                          uments [1], including the relevant geological sites, so individuating restoration and/or
                                                                                          preservation actions.

                                                                                          2. Historical outlines

                                                                                             The Valley of the Temples of Agrigento is one of the most important evidences of the
                                                                                          Greek civilization in Sicily. It is located in the southern part of Agrigento town, on the ruins
                                                                                          of the ancient Akragas.
                                                                                             According to the historical tradition, the city was founded in 582 B.C., by a group of
                                                                                          settlers from Gela.
                                                                                             The building materials used for the temples come from different local quarries, among
                                                                                          which Villaseta and Casa San Filippo. In detail, the Villaseta excavation exhibits at least
                                                                                          two levels of rocks, different in the softness properties and in the clay content.
                                                                                             Segesta is an abandoned ancient town located in the province of Trapani. This large
                                                                                          archaeological zone, with its magnificent Doric temple, is considered as one of the best-
                                                                                          preserved Greek architectural sites. The temple of Segesta was built using travertine

                                                                26
rock. The samples of travertine have been drawn in the territory of Alcamo, a little town
not far from Segesta where some quarries are still active. Beside its typical mechanical
properties, the Alcamo travertine is very important also from a palaeontological point of
view for the presence of several fossil remains, in particular a dwarf mammal (Elephas
falconeri BUSK), and a giant tortoise.
   Selinunte was founded in 651-650 B.C. and represented the western part of the
Greek advance in Sicily. All the used materials are calcarenites and come from the
Quarries of Cusa.
   The quarries of Cusa are approximately 13 km far from Selinunte. They were used to
extract the building materials of the town of Selinunte and of its temples. They were active
from the 600 B.C. until the 409 B.C., when Selinunte was destroyed; since then the quar-
ries remained intact and some cuts in cylindrical blocks are still visible (see more ahead).
A large bank of calcarenite, parallel to the coast and almost 2 km long, forms the quar-
ries. This bank is characterized from different veins of various hardness and mechanical
resistance, and they were used for different applications in buildings. Through the histor-
ical-archaeological research it was possible to reconstruct the various operations for the
quarrying and the transport of the blocks.

3. Geological sketch

   Samples and sites are referred to very different geological environments.
Consequently, sedimentary settings have assigned peculiar mechanical features to
rocks, certainly affecting the relevant hardness and workability characteristics. At this
proposal, it should be very fascinating to dwell upon the ancient methods of cuttings and
extraction of rocks from the quarries, the transport method towards the archaeological
sites and, finally, upon the techniques of monument edification. Unfortunately, this is not         Quaderni di Scienza della Conservazione
the main purpose of the research to which this contribution belongs.

The Agrigento geological sites

   Quarries of “Villaseta” and “Casa San Filippo” localities, that have supplied the
archaeological site of Agrigento, are not far from the all over the world famous “Valle dei
Templi”. Both the arenaceous formation are called Formazione di Agrigento [2] and they
are constituted by more or less rough calcarenites, lower Pleistocene aged, with crossed
stratification and sand interbeddings. This lithology contains common microfossils and
malacofaunas as Arctica Islandica. Temples area remains on the same arenaceous base-
ment and, partially, on marly-clayey and more recent alluvial terraced formations (respec-

                                                                                               27
                                                                                          tively belonging to lower Pleistocene and Holocene ages). Marly-clayey deposits
                                                                                          (Formazione di Monte Narbone), upper-middle Pliocene aged, occur below these forma-
                                                                                          tions, posing serious problems of stability for the Agrigento town and for the same archae-
                                                                                          ological area. The known landslide phenomena, due to the regression of the calcarenite
                                                                                          front, represent an effective risk condition for the whole Agrigento region.

                                                                                          The Alcamo geological site

                                                                                              Travertine quarries are located north of the Alcamo village, relatively far from the
                                                                                          Segesta archaeological area (about 10 km). The importance of this calcareous rock is
                                                                                          testified, besides the notable mechanical properties, by the large occurrence in most of
                                                                                          the territory on which the urban area of Alcamo is largely expanded. This very recent sed-
                                                                                          imentary rock (Holocene), chemically originated, generally presents minute laminations
M. Brai et al. - Integrated techniques to evaluate the features of sedimentary rocks...




                                                                                          and numerous vacuoles, these last ones longed following the bedding trend [3].
                                                                                          Travertine commonly shows fossil forms as algal and vegetable rests, sometimes verte-
                                                                                          brates. In particular, the Alcamo travertines may include eggs of terrestrial turtles.
                                                                                              The geological features of the Segesta archaeological site are fairly different from the
                                                                                          quarry location. Outcrops of limestones, prevalently calcilutites with chert (Scaglia), occur
                                                                                          in most of the mountainous area on which Greeks elevated the temple and the amphithe-
                                                                                          ater.

                                                                                          The Cusa geological site

                                                                                              The Cusa quarries, 13 km west of Selinunte, are about 3 km far from the
                                                                                          Mediterranean Sea. Here geological deposits, belonging to Holocene-Pleistocene age,
                                                                                          occur, formed by calcarenite sediments [4]. The whole arenaceous outcrop is very con-
                                                                                          spicuous, covering a very large area with very different characteristics of hardness.
                                                                                          Instead, the archaeological site rests on a terraced formation, locally named Selinuntiano
                                                                                          (basal level of the Pleistocene), and largely diffused along a continuous coastal belt
                                                                                          extended for many kilometers in South-West Sicily.
                                                                                              Locally, the Cusa arenites present the best mechanical properties of the neighbor-
                                                                                          hoods: the ancient people selected accurately them for the edification of the biggest ele-
                                                                                          ments of the old town, as columns. For minor exigencies of buildings, Greeks used clos-
                                                                                          er quarries (Latomie), where the rock presented worse mechanical properties.
                                                                                          Calcarenite was extracted for 150 years, up to the successive, Carthaginian domination.
                                                                                          As a matter of fact, Punic civilization neglected the quarries, leaving them in the same
                                                                                          conditions as at the time of the sudden abandon by Greek people.

                                                               28
   Selinunte is the most extended archaeological park of the whole Mediterranean
region. Overcoming the same geological interest, this area has been intensely studied
under the seismological point of view. Indeed, besides the tremendous earthquake that
has shaken the Belice valley (1968), archaeo-seismological analyses have interpreted
the collapse of the seven temples as the result of two strong telluric events.

4. Materials and methods

   Samples coming from the different quarries were collected (fig. 1). Table 1 reports
sampling site and lithology as well as the archaeological areas in which the stones were
used to built temples and other dwellings.
   Figs. 2 and 3 show also the stones collected in the quarries of Agrigento. The sam-
ples named Calcarenite 1 and Calcarenite 2 have been collected respectively in the
upper and lower parts of the “Villaseta” quarry (South-West of the actual Agrigento town).
These outcrops correspond to different levels of rock, as indicated in the left picture of fig.
2. The Calcarenite 3 sample has been collected in the “Casa San Filippo” quarry (east-
ern outskirts of town). The materials coming from these quarries were used to built, in the
past, the Agrigento temples and recently for the restoration of columns.
   Figs. 4 and 5 depict the quarries and the sampled stones relevant to Segesta and
Selinunte archaeological areas.
   Several measurements were performed over all the samples, using the methods and
the below described techniques.
   The mineralogical and geochemical characterization [5] was performed through X-
Ray Diffractometry (XRD) and X-Ray Fluorescence (XRF) techniques.

                                                                                                   Quaderni di Scienza della Conservazione

        Table 1. Sampling sites and lithology.

              Sampling site              Lithology             Archaeological area

             Villaseta (AG1)            Calcarenite 1                Agrigento
             Villaseta (AG2)            Calcarenite 2                Agrigento
             Agrigento (AG3)            Calcarenite 3                Agrigento
             Alcamo (TP1)               Travertine 1                 Segesta
             Alcamo (TP2)               Travertine 2                 Segesta
             Cusa (TP3)                 Calcarenite 4                Selinunte



                                                                                                  29
M. Brai et al. - Integrated techniques to evaluate the features of sedimentary rocks...




                                                                                                 Figure 2. The “Villaseta” quarry. Below the samples collected respectively
                                                                                                 on the upper and lower parts of the quarry.


                                                                                             For the XRD and XRF analysis, all the samples were reduced in a powdery form con-
                                                                                          sisting of fine grains of single crystalline material [6].
                                                                                             XRD measurements were carried out with a Philips XPERT diffractometer. A voltage
                                                                                          of 40 KV and a current of 20 mA was applied at the X ray anode mated in Cooper mate-
                                                                                          rial and the slit velocity was 2°/min.
                                                                                             XRF measurements were performed using a X-ray fluorescence instrument Philips
                                                                                          PW 1400. The voltage range was 30-50 KV and the current is 30-50 mA. The X-ray anode
                                                                                          is chromium-made for the light elements and wolfram-made for the heavy ones.
                                                                                             MRI measurements were executed at 30°C by means of ARTOSCAN (Esaote Italy),
                                                                                          a tomograph consisting of a 0.2-T permanent magnet (15 mT/m maximum gradient inten-

                                                                30
Figure 3. The “Casa San Filippo” quarry, on the left. The relevant sample is also shown.




                                                                                                Quaderni di Scienza della Conservazione




          Figure 4. The “Alcamo” quarry. Below the two different samples.
          The sample marked as Travertine 2 was collected performing a
          core drilling.

                                                                                           31
M. Brai et al. - Integrated techniques to evaluate the features of sedimentary rocks...




                                                                                          Figure 5. The “Cusa” quarry on the left will the relevant sample.


                                                                                          sity) corresponding to 8 MHz for 1H. Many adjacent sections (5 mm thickness) were
                                                                                          acquired at the same time by multislice Spin Echo (SE) sequence with echo time TE = 10
                                                                                          ms and repetition time TR = 900 ms. The voxel size was 0.5x0.5x5 mm3.
                                                                                             NMR Relaxometry measurements were performed at the Larmor frequency of 20
                                                                                          MHz by means of a relaxometer based on a Jeol variable-field electromagnet equipped
                                                                                          with Spinmaster, a NMR data station by Stelar (Mede, Pavia, Italy). Transverse relaxation
                                                                                          decays were acquired by the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence.
                                                                                          Longitudinal relaxation curves were acquired by Inversion Recovery sequences.
                                                                                          Experimental curves were analyzed on the assumption of continuous distributions of
                                                                                          relaxation times by means of UPEN, a uniform penalty inversion algorithm for multiexpo-
                                                                                          nential decay data [7].
                                                                                             For NMR Imaging (MRI) [8] samples of the same rocks were used. In particular, for
                                                                                          the Agrigento samples, cylinders of 10 cm in diameter and 10 cm in height were extract-
                                                                                          ed by core-drilling.
                                                                                             The samples used for imaging were wrapped in plastic film in all cases in order to pre-
                                                                                          vent water evaporation during measurements. In particular, the Travertine 1 sample was
                                                                                          kept into the water during the measurement because of the large and numerous cavities.
                                                                                             For NMR relaxometry [8] small cylindrical plugs (7 mm in diameter and 7 mm in
                                                                                          height) were cored from all the original samples. For both MRI and relaxation analyses,
                                                                                          the samples were completely dried and then saturated under vacuum with distilled water.

                                                                       32
The liquid excess was wiped off the small plugs with filter paper and put into the NMR
tube for the relaxation measurements.
   The interpretation of relaxation data in terms of “pore-size” distributions was done by
a specific methodology described in the literature [9].
   As an alternative method to investigate the structural porosity of rocks and to give fur-
ther pieces of information on the absorption kinetics, Authors propose also the applica-
tion of the X-ray Computerized Tomography (CT).
   The CT imaging were performed by means of a Philips apparatus belonging to the
Brilliance series. The voltage at the anode was setted to 140 kV value, and the current to
600 mAs. The continuous acquisition imaging was performed with the slice widths of 0.67
mm. The collimation of the radiative source was 40 mm x 0.625 mm.
   The samples were cut in blocks 50x50x30 mm3 of size.
   Samples were settled in a plexiglas container, with an interposed filter papers wet with
distilled water. The images were acquired in sequential times after contact with water.

5. Results and discussion

   Table 2 presents the XRD data. The mineralogical characterization shows for all the
samples a prevalence of calcite. Quartz and traces of clay are also present. Quartz
exhibits variability in the different samples [10].
   Table 3 reports the XRF values for each sample. The elemental analysis confirms the
calcium abundance and, in agreement with the mineralogical data illustrated in table 2,
the low levels of Si and Al. Among the other elements, iron is the most abundant. The light
elements cannot be measured [10].
   The phosphorous presence can be explained with the presence of fossils in the bio-
calcarenite.                                                                                        Quaderni di Scienza della Conservazione


                 Table 2. XRD data.

                    Sample          quartz            calcite    clay

                      AG1             ++               +++       traces
                      AG2             ++               +++       traces
                      AG3             +                +++      absent
                      TP1           absent            ++++       traces
                      TP2           absent            ++++      absent
                      TP3             +               ++++       traces


                                                                                               33
                                                                                          Table 3. Content of elements expressed in % of oxides and corrected for L.O.I.

                                                                                            Sample       SiO2    TiO2        Al2O3       P2 O 5   Fe2O3   MgO    MnO      CaO    Na2O    K 2O

                                                                                              AG1       12.86    0.12        2.51        0.33     8.30    1.56   0.14    73.63    0.27   0.29

                                                                                              AG2       24.72    0.16        3.13        0.33     8.74    1.57   0.12    60.52    0.13   0.58

                                                                                              AG3       22.32    0.07        1.77        0.41     8.49    1.20   0.14    65.17    0.09   0.34

                                                                                              TP1        1.22    0.03        0.78        2.32     0.27    0.13   0.13    95.08    0.00   0.04

                                                                                              TP2        2.06    0.03        0.59        0.07     0.23    0.11   0.15    96.68    0.00   0.09

                                                                                              TP3        6.84    0.04        0.75        0.23     1.79    1.35   0.16    88.69    0.05   0.11



                                                                                                                                         MRI was utilized to study the local structure in
                                                                                                                                     internal regions of the stones saturated by water. NMR
M. Brai et al. - Integrated techniques to evaluate the features of sedimentary rocks...




                                                                                                                                     Relaxometry gave information on the pore space
                                                                                                                                     structure at smaller scale than MRI [10,11]. In the fig-
                                                                                                                                     ures relative to results obtained by NMR Relaxometry,
                                                                                                                                     the ordinate is (dS)/(d lnT1), where S is percent of total
                                                                                                                                     signal (proportional to the number of 1H nuclei), in
                                                                                                                                     such a way that areas under the curves are normal-
                                                                                                                                     ized to unit area.
                                                                                                                                         The MRI images of the three samples from
                                                                                                                                     Agrigento are reported in fig. 6.
                                                                                                                                         The relaxation measurements obtained on two
                                                                                                                                     plugs cored from each sample are reported in fig. 7.
                                                                                                                                         The T2 distributions are similar to the T1 distribu-
                                                                                                                                     tions, simply shifted to shorter times. The shape of
                                                                                                                                     the distributions reflects an heterogeneous pore
                                                                                                                                     space, covering tree decades for T1 and four decades
                                                                                                                                     for T2. Even if it is not right to think of sharp bound-
                                                                                                                                     aries, it appears that two fractions of water may
                                                                                                                                     spend their NMR lifetimes confined in not well con-
                                                                                                                                     nected pore spaces, the one with higher and the other
                                                                                                                                     with smaller S/V ratio. In order to better compare the
                                                                                                                                     three samples, all the T1 distributions and the T2 dis-
                                                                                          Figure 6. Inner MRI section of             tributions are collected in Figs. 8a and 8b, respec-
                                                                                          sample a) Calcarenite 1, b)
                                                                                          Calcarenite 2, c) Calcarenite 3.           tively.

                                                                  34
   The shape of the distributions does not show remarkable differences among samples.
It is worth of note that relaxation measurements were obtained from drained plugs, after
they had spontaneously lost water from the large pores connected to the outside. The
distributions therefore describe only the water contained in the pores after the drainage,
only weakly coupled with each other. So, the distributions in Figs. 8a and 8b show a very
similar pore structure in the three samples at the length scale smaller than the sample
                                            scale.
                                               In fig. 9 a MRI section, representative of
                                            all the slices acquired on the Travertine 1
                                            sample, is reported. In this case, in order to
                                            prevent the sample from empting through the




                                                                                                   Quaderni di Scienza della Conservazione




                                               Figure 8. a) Relaxation time distribution
Figure 7. T1 and T2 distributions, for         functions of T1 for all the plugs (two plugs
each pair of two plugs cored from the          for each sample); b) Relaxation time dis-
Agrigento samples. Solid lines are for         tribution functions of T2 for all the plugs
T1, dashed for T2.                             (two plugs for each sample).

                                                                                              35
                                                                                          Figure 9. Inner MRI section of                Figure 10. Relaxation time distribution func-
                                                                                          Travertine 1 sample.                          tions of T1 and T2 (Travertine 1 sample).
M. Brai et al. - Integrated techniques to evaluate the features of sedimentary rocks...




                                                                                          large cavities, it was put into a plastic bag containing water. This sample presents two
                                                                                          parts (see fig. 4): the former (A) has an alabaster appearance and originates from chem-
                                                                                          ical precipitation of calcium carbonate only, the latter (B) is the travertine and originates
                                                                                          from chemical precipitation of calcium carbonate with organic components (algal) that
                                                                                          cause the making of vacuoles. Data in table 2 and 3 are referred to B part. In the image
                                                                                          pixels corresponding to cavities with water appear bright. Water is also present between
                                                                                          layers of the region with alabaster appearance.
                                                                                             NMR Relaxation measurements, reported in fig. 10, were performed on two plugs
                                                                                          cored from Travertine 2, a more compact travertine sample (see again fig. 4), coming
                                                                                          from a region deeper than Travertine 1. The distributions show a single peak, centered
                                                                                          at about 200 ms for T1, standing on a wide pedestal: about 80-90% of the signal is due
                                                                                          to water in a single class of diffusion cells not well connected, or in slow exchange at the
                                                                                          NMR relaxation time scale with the remaining fraction of water confined in higher or lower
                                                                                          S/V pore spaces. The shapes of the distribution functions of T1 and T2 suggest a broad
                                                                                          distribution of pore sizes. There are tails towards short and long times, likely showing
                                                                                          small amounts of water in smaller and larger pores not well connected at the NMR time
                                                                                          scale with the major broad peak.
                                                                                             In fig. 11 a MRI section, representative of all the slices acquired on Calcarenite 4 sam-
                                                                                          ple, is reported.
                                                                                             The sample appears very homogeneous both between slices and inside the same
                                                                                          slice. The pore space structure of the samples can be investigated with a larger resolu-
                                                                                          tion power by means of the spatially-not resolved relaxation measurements.

                                                                   36
Figure 11. Inner section of               Figura 12. Relaxation time distribution func-
Calacarenite 4 sample.                    tions of T1 and T2.



   In fig. 12 T1 and T2 distributions of two small plugs cored from the sample are report-
ed. Both T1 and T2 distributions for the two Calcarenite 4 plugs are wider than for
Travertine 2 plugs. The samples appear to have a quite homogeneous structure, with a
single class of low S/V pore spaces plus a low and wide tail that reveals the presence of
high S/V pore spaces not well connected with the lower S/V pores.
   The internal structure of same samples was also investigate with the CT imaging.




                                                                                                  Quaderni di Scienza della Conservazione




    Figure 13. Photos and CT images of three calcarenite samples.

                                                                                             37
                                                                                             The fig. 13 shows a photo of the calcarenite samples marked as AG1, AG3 and TP3.
                                                                                          In the same figure the internal views of the same slice, acquired at different time, are also
                                                                                          presented, second column shows the internal view of the dry samples, and third colum
                                                                                          the images of wet samples, acquired after t = 15 min in water adsorption. The images of
                                                                                          the wet samples are more intense.
                                                                                             The system of units represents a transformation from the original linear attenuation
                                                                                          coefficient measurements into one where water assumes a value of zero and air has a
                                                                                          value of –1000, while, for example, bones rich of calcium has H unit of +1000. If µw, µair,
                                                                                          and µ are the linear attenuation coefficients of water, air and a substance of interest, the
                                                                                          CT number of the substance of interest is:

                                                                                                                              H = 1000 µ – µw
                                                                                                                                      µw – µair
M. Brai et al. - Integrated techniques to evaluate the features of sedimentary rocks...




                                                                                             It follows that a measurement of the Hounsfield value of the same portion of different
                                                                                          slices, acquired in different times, can give information about a evaluation of adsorption
                                                                                          kinetics in rocks. Moreover, considered samples of known porosity, from the Hounsfield
                                                                                          value measured, it is possible to evaluate the pore size dimension of the material of inter-
                                                                                          est. Our future working investigation is to compare CT resolution with MRI. The possibil-
                                                                                          ity to investigate the internal structure of porous materials will be also strengthened by
                                                                                          the three dimensional views of the items (see fig. 14).




                                                                                                 Figure 14. a) CT 3D reconstruction; b) Picture of the stone.
                                                                  38
   These preliminary surveys confirm the considerable heterogeneity of sedimentary
rocks for porosity and for ability to trap water, also in the case of very similar mineralog-
ical and chemical features [10]. The data obtained from different techniques can give a
complete insight in order to select not invasive protective treatments. The preliminary
results of the present paper will form the basis for the creation of a relational database
on Sicilian sedimentary rocks of interest to study the health state of cultural heritages for
eventual prevention and therapy.

Acknowledgments

   The authors wish to thank M. Mirabello (Dipartimento di Fisica e Tecnologie Relative,
Università degli Studi di Palermo), C. Garavaglia (Dipartimento di Fisica, Alma Mater
Studiorum Università di Bologna), F. Sorrentino (Dipartimento di Biotecnologie Mediche
e Medicina Legale, Università degli Studi di Palermo) for technical assistance; P. Meli,
Parco Archeologico di Agrigento, and the F.lli Scirè quarries of Villaseta, Agrigento, for
assistance in sampling.

References
[1] CIMINO A., ABBATE R., MANNINO G. 1990, Prime indagini geofisiche per la
    tutela di un’area archeologica del Palermitano. Ambiente, Salute, Territorio, 4, 1,
    20-25.
[2] SERVIZIO GEOLOGICO D’ITALIA 1972, Carta geologica d’Italia a scala 1:50.000,
    Foglio 636 “Agrigento”, Grafica Editoriale Cartografica, Roma.
[3] UNIVERSITÀ DI PALERMO, DIPARTIMENTO DI GEOLOGIA E GEODESIA 1995,
    Carta geologica a scala 1:50.000, Foglio 606 I.G.M. “Alcamo”, Stabilimento L.
    Salomone, Roma.
[4] SERVIZIO GEOLOGICO D’ITALIA 1976, Carta geologica d’Italia a scala 1:500.000,                Quaderni di Scienza della Conservazione
    Foglio 5 “Sicilia”, Stabilimento L. Salomone, Roma.
[5] RIZZO S., BRAI M., BASILE S., BELLIA S., HAUSER S. 2002, Gamma Activity and
    Geochemical Features of Building Materials: Estimation of Gamma Dose Rate and
    Radon Level Indoors in Sicily, Appl. Rad. Isot., 55, 259-265.
[6] BARTOLOTTA A., BELLIA S., BRAI M., CASIERI C., DE LUCA F., FANTAZZINI P.,
    MACCOTTA A., MORREALE F., RASO G., SCHILLACI T. 2004, Caratterizzazione di
    materiali lapidei, in Regione Siciliana (ed.), Il teatro greco-romano di Taormina.
    Progetto pilota. Analisi, studi ed indagini, prima fase, Palermo, 109-112.
[7] BORGIA G.C., BROWN R.J.S., FANTAZZINI P. 1998, Uniform-Penalty Inversion of
    Multiexponential Decay Data, J. Magn. Reson., 132, 65-77.
[8] BORGIA G.C., BORTOLOTTI V., CAMAITI M., CERRI F., FANTAZZINI P., FRATTINI
    F., PIACENTINI F. 2002, Caratterizzazione strutturale di materiali porosi: un nuovo
    approccio mediante tecniche NMR, in Patron Editore Bologna (ed.), ATTI del

                                                                                                39
                                                                                               Secondo Congresso Nazionale dell’Assoc. Italiana di Archeometria, (Bologna, 29
                                                                                               gennaio - 1 febbraio), 135-150.
                                                                                          [9] BORGIA G.C., BROWN R.J.S., FANTAZZINI P. 2000, Uniform-Penalty Inversion of
                                                                                              Multiexponential Decay Data II: Data Spacing, T2 Data, Systematic Data Errors, and
                                                                                              Diagnostics, J. Magn. Reson., 147, 273-285.
                                                                                          [10] SCHILLACI T., BELLIA S., BRAI M., CAMAITI M., DI STEFANO C., FANTAZZINI P.,
                                                                                               MACCOTTA A. 2005, Integrated techniques to study sedimentary rocks from Sicily
                                                                                               used in cultural heritages, in (ed), “Non-destructive testing and microanalysis for the
                                                                                               diagnostic and conservation of the cultural and environmental heritage” Proceedings
                                                                                               of the 8th International Conference (Lecce, 15-19 May 2005), digital support (article
                                                                                               number 147).
                                                                                          [11] BRAI M., CAMAITI M., CASIERI C., DE LUCA F., FANTAZZINI P., MACCOTTA A.,
                                                                                               MORREALE F., TERENZI C. 2005, From laboratory to in-situ Nuclear Magnetic
                                                                                               Resonance diagnostics: an application to building materials of the Greek-Roman
                                                                                               theatre of Taormina, in (ed.), “Non-destructive testing and microanalysis for the diag-
M. Brai et al. - Integrated techniques to evaluate the features of sedimentary rocks...




                                                                                               nostic and conservation of the cultural and environmental heritage” Proceedings of
                                                                                               the 8th International Conference (Lecce, 15-19 May 2005), digital support (article
                                                                                               number 140).

                                                                                          Riassunto
                                                                                          In Sicilia sono presenti numerose unità geologiche, le quali forniscono al paesaggio una relativa
                                                                                          complessità. L’origine è prevalentemente di tipo sedimentario. È ben noto che le rocce sedimenta-
                                                                                          rie rispetto ai depositi metamorfici e vulcanici, possono presentarsi maggiormente tenere e, quindi,
                                                                                          con una discreta facilità ad essere modellate.
                                                                                          Questa lavorabilità, caratteristica e vantaggio delle rocce sedimentarie, è tuttavia un inconveniente
                                                                                          rispetto alla loro utilizzazione per il patrimonio culturale, poiché questi materiali evidenziano spesso
                                                                                          un’elevata porosità, con distribuzione e dimensione dei pori che portano al loro deterioramento per
                                                                                          assorbimento d’acqua.
                                                                                          In questa nota, si propone una classificazione di più rocce sedimentarie adoperate nei manufatti del
                                                                                          patrimonio storico-culturale della Sicilia, dalla Magna Graecia ai giorni nostri.
                                                                                          La classificazione riguarda le caratteristiche mineralogiche, la composizione chimica e la porosità.
                                                                                          Nel dettaglio, saranno presi in considerazione e caratterizzati, usando tecniche integrate (XRD, XRF,
                                                                                          NMR e CT), campioni raccolti in cave appartenenti ai siti archeologici di Agrigento, Segesta e
                                                                                          Selinunte.
                                                                                          I dati sui campioni ottenuti in laboratorio saranno confrontati con i corrispondenti valori misurati in
                                                                                          situ sui monumenti di interesse storico-culturale ricadenti nelle citate località archeologiche.


                                                                                          Summary
                                                                                          Sicily includes a great variety of lithologies, giving a high complexity to the geologic landscape. Their
                                                                                          prevalent lithology is sedimentary. It is well known that rocks of sedimentary origin, compared with
                                                                                          metamorphic and volcanic deposits, can be relatively soft and hence fairly easy to model.
                                                                                          Nevertheless, this workability advantage is a drawback for Cultural Heritage applications. In fact,
                                                                                          these materials show a high porosity, with pore-size distributions that lead to deterioration through
                                                                                          absorption of water.
                                                                                          In this paper, several sedimentary rocks used in historical Cultural Heritage items of Sicily, from
                                                                                          Magna Graecia to nowadays, are classified for mineralogical features, chemical composition, and
                                                                                          for porosity. Particularly, some samples collected in quarries relevant to the archaeological sites of


                                                        40
Agrigento, Segesta and Selinunte will be considered and characterized using integrated techniques
(XRD, XRF, NMR and CT).
Data on samples obtained in laboratory will be compared with the relevant values measured in situ
on monuments of historical-cultural interest of the quoted archaeological places.


Résumé
En Sicile sont présentes de nombreuses unités géologiques, lesquelles fournissent au paysage une
relative complexité. L’origine est essentiellement de type sédimentaire. C’est bien connu que les
roches sédimentaires, par rapport aux dépôts métamorphiques et volcaniques, peuvent se présen-
ter plus tendres et, donc, avec une discrète facilité à être modelées.
Cette usinabilité, caractéristique et avantage des roches sédimentaires, est toutefois un inconvé-
nient par rapport à leur utilisation pour le patrimoine culturel, étant donné que ces matériaux mettent
en évidence souvent une porosité élevée, avec distribution et dimension des pores qui portent à leur
détérioration par absorption d’eau.
Dans cette note, on propose une classification de plusieurs roches sédimentaires employées dans
les ouvrages du patrimoine historico-culturel de la Sicile, de la Grande Grèce à nos jours.
La classification concerne les caractéristiques minéralogiques, la composition chimique et la porosi-
té.
Dans le détail, seront pris en considération et caractérisés, en employant des techniques intégrées
(XRD, XRF, NMR et CT), des échantillons recueillis dans des carrières appartenant aux sites
archéologiques de Agrigente, Ségeste et Sélinonte.
Les données sur les échantillons obtenus en laboratoire seront confrontées avec les valeurs cor-
respondantes mesurées in situ sur les monuments d’intérêt historico-culturel retombant dans les
localités archéologiques citées.


Zusammenfassung
In Sizilien sind viele geologische Einheiten, die die Landschaft ziemlich komplex machen. Die
Herkunft dieser Einheiten ist hauptsächlich sedimentär. Es ist weit bekannt, dass die sedimentären
Steine im Vergleich mit den metamorphen und vulkanischen Ablagerungen weicher sein können und
deswegen können sie relativ einfach geformt werden.
Dennoch ist die Tatsache, dass diese Steine einfach zu formen sind, nicht nur ein vorteilhafter
Merkmal der sedimentären Steine, sondern auch einen Nachteil, was ihre Verwendung für das
Kulturgut angeht, weil diese Materialien oft sehr porös sind, und die Verteilung und die Größe ver-
ursachen ihr Verderben wegen der Absorption von Wasser.
Hier ist eine Klassifizierung von verschiedenen sedimentären Steinen, die in den Artefakten des                Quaderni di Scienza della Conservazione
Geschichts- und Kulturgutes von Sizilien, von der Magna Graecia bis zur unseren Zeit benutzt wur-
den.
Die Klassifizierung betrifft die mineralogischen Merkmale, die chemische Zusammensetzung und die
Porosität. Insbesondere werden einige Muster betrachtet und charakterisiert, die aus Gruben in den
archäologischen Ausgrabungsstätten von Agrigento, Segesta und Salinunte gewonnen wurden, es
werden dabei integrierte Techniken angewandt (XRD, XRF, NMR und CT).
Die Daten über die Muster im Labor werden mit den entsprechenden Werten verglichen, die vor Ort
aus historisch und kulturell interessanten Denkmälern in den obengenannten Ausgrabungsstätten
gemessen wurden.


Resumen
Sicilia presenta numerosas unidades geológicas, que dan al paisaje una relativa complejidad. El ori-
gen es predominantemente de tipo sedimentario. Es bien sabido que las rocas sedimentarias, con
respecto a los depósitos metamórficos y volcánicos, suelen presentarse blandas y ofrecen, con ello,
una cierta facilidad para ser modeladas.

                                                                                                          41
                                                                                          Esta modelabilidad, característica y ventaja de las rocas sedimentarias, es sin embargo un incon-
                                                                                          veniente en lo que se refiere a su uso para el patrimonio cultural, ya que, en cuanto materiales, a
                                                                                          menudo muestran una elevada porosidad, con poros que, por su tamaño y distribución causan el
                                                                                          deterioro por absorción de agua.
                                                                                          En esta nota se propone una clasificación de diversos tipos de rocas sedimentarias utilizadas en las
                                                                                          obras del patrimonio histórico-cultural de Sicilia, de la Magna Graecia a nuestros días.
                                                                                          La clasificación atiende a las características mineralógicas, la composición química y la porosidad.
                                                                                          En particular, se tomarán en consideración y se caracterizarán, mediante técnicas integradas (XRD,
                                                                                          XRF, NMR y CT), muestras recogidas en canteras pertenecientes a los sitios arqueológicos de
                                                                                          Agrigento, Segesta y Selinunte.
                                                                                          Los datos en las muestras obtenidas en laboratorio se compararán con los valores correspondien-
                                                                                          tes medidos in situ en los monumentos de interés histórico-cultural pertenecientes a las citadas loca-
                                                                                          lidades arqueológicas.
M. Brai et al. - Integrated techniques to evaluate the features of sedimentary rocks...




                                                               42
