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1. Introduction        Archaeological and historical research over the        last three decades has increased our understanding of iron production        and consumption in the early Middle Ages. Excavations of settlements        and burials provide substantial documentation about iron consumption        modalities related to distinct activities: agriculture, weaponry,        craftsmanship, domestic ware… In comparison, the use of metal in early        medieval architecture, and particularly during the Carolingian epoch,        has been characterized far less, despite its fundamental importance.        Indeed, sites that may provide necessary material are scarce. Although        the use of iron is evidenced during Carolingian times, as in the        palatial complex of Aachen (Davis &#38; McCormick, 2008, p. 284),        metallic reinforcements are often inaccessible. Documentary sources,        such as account books, that provide important information about        medieval building yards, are lacking for the Carolingian period.        Consequently, the unearthing in 2005 of two piers of a stone bridge        (Gucker &#38; Legendre, 2006, 2007), built in the late 9th c.1 across the Moselle River (Meurthe-et-Moselle, Lorraine,        France), provides a rare opportunity to study ferrous clamps        implementation modalities in Carolingian monumental architecture.        First, it is important to mention that the facings of the stone piers        are made of architectural blocks scavenged from monuments in the        abandoned Roman town of Scarponna (Boulanger        &#38; Gucker, 2008), located a few hundred meters from the bridge        (Figure 1). These stones are fastened by iron clamps. Since reusing        architectural materials was common in the Middle Ages, it is likely        that iron reinforcements might also have been recovered from the Roman        monuments, sparing the effort of forging new clamps. Nevertheless,        several production centres from this period in central Lorraine have        been the subject of archaeological research conducted over the last        three decades on ancient ironmaking activities. The most iconic        workshop is located 25 kilometres south of the bridge, under the        present village of Ludres (Meurthe-et-Moselle). It operated from the        early 8th c. until the late 10th c. Though the extent of activity is unknown, from        several dozens to hundreds of tons of metal were produced. Such        volumes were probably sufficient to supply numerous regional markets,        and even extra-regional commercial networks. Moreover, activities of        such magnitude were certainly supervised by some political power that        would have controlled and organized both production and distribution        activities. The presumed status of this workshop raises crucial        questions regarding commercial networks established in this part of        Lothringia during Carolingian times. A dozen iron clamps from the        Dieulouard bridge piers were studied to provide information about the        iron supply strategies implemented by an early medieval building yard.        An archaeometric study involving microstructural and chemical        characterization of ferrous alloys and slag inclusions was performed        on this set, allowing provenance and dating studies.        Figure 1: Location of main Roman and medieval        vestiges around Dieulouard-Scarponna / Figure 1 : Localisation des        principaux vestiges antiques et médiévaux aux alentours de Dieulouard        – Scarponne                                        2. Sample set and experimental        methodology        Forty-three iron reinforcements were collected from        the two stone piers. Despite the fact that they were all sealed in        lead, preventing them from corroding, their conservation state is        variable. Some sustained deformations, and some are fragmented due to        the collapsing of the piers. Eleven clamps were selected for the        present study. They are formed by a flat part terminated by two pins        set at a right angle. Their length ranges from 200 to 250 millimetres,        their width from 6 to 8 mm, and their thickness from 33 to 56 mm. The        length of the pins is between 33 and 56 mm. The average weight of an        entire clamp is 359 grams (minimum: 214 g; maximum: 445 g) (Table 1).        Pins were crafted in different ways. Clamps 411A1, 489A1 and 1167A1        were formed by folding the metal into an “S” shape. The other clamps        were made by bending the metal extremities back on themselves. The way        of making the clamps appears relatively consistent at the scale of the        sample set, except for some minor differences observed mainly in the        pins.        Table 1: Measurements made on clamps selected        for archaeometrical study / Tableau 1 : Dimensions des crampons ayant fait l’objet de l’étude        archéométrique                                                            Clamp n°                                                                    Length (mm)                                                                    Max. width (mm)                                                                    Min. width (mm)                                                                    Thicknes (mm)                                                                    Average length of pins (mm)                                                                    Weight (g)                                                                        100A1                                      111 cons.                                      39                                                                             9                                      40                                      145                                                          251A1                                      250                                      40                                      32                                      8                                      43                                      412                                                          256A1                                      175 cons.                                      36                                      31                                      6                                      42                                      201                                                          272A1                                      161 cons.                                      32                                      30                                      6                                      37                                      160                                                          411A1                                      146 cons.                                      38                                      30                                      8                                      33                                      235                                                          489A1                                      225                                      35                                      31                                      8                                      38                                      445                                                          510A1                                      82 cons.                                      37                                      N/A                                      8                                      46                                      N/A                                                          1052A1                                      224                                      37                                      29                                      8                                      56                                      426                                                          1167A1                                      270                                      34                                      28                                      8                                      53                                      214                                                          1219A2                                      196                                      33                                      31                                      8                                      54                                      N/A                                                          HSA3                                      235                                      36                                      30                                      8                                      43                                      297                                                          Moyenne                                      233,33                                      36,09                                      30,22                                      7,73                                      44,09                                      358,80                                                          Ecart-type                                      25,20                                      2,47                                      1,20                                      0,90                                      7,46                                      186,54                                                          Ecart-type relatif                                      10,80%                                      6,84%                                      3,98%                                      11,71%                                      16,93%                                      51,99%                                      Some clamps show slight concavities on their edges,        suggesting hammering to adjust their width to fit the orifices carved        in the stone blocks. Three artefacts (251A1, 510A1, 1219A2) show marks        of welding, indicating that two iron pieces were put together to        produce fastenings of sufficient length.        Several cuttings were performed for each clamp,        either in the longitudinal (251A1, 220A1, 272A1, 411A1, 489A1, 510A1,        1052A1, 1219A2, HSA3) or transverse (100A1, 256A1, 1167A1) axes. The        cross-sections were cold-mounted in epoxy resin, then prepared for        metallographic examination by grinding the surface with SiC papers        (grade 80 to P2400), and finally polishing it using diamond paste (3        and 1 µm). All surfaces were examined after Nital etching (3% HNO3) using an Olympus BX51 optical microscope coupled to        a Qimaging CCD camera. Examining microstructures allows reconstruction        of the chaîne opératoire, and identifies        potential thermic (welding, tempering) or thermochemical (cementation)        treatments. Furthermore, it enables the definition of the most        relevant areas of interest for chemical analyses taking into account        microstructural characteristics of both metallic matrix and slag        inclusions.        These areas of interest were then examined by Field        Emission Gun Scanning Electron Microscopy (FEGSEM), using an        accelerating voltage of 15kV. Semi-quantitative analysis of major        elements contained in non-metallic inclusions was performed by Energy        Dispersive Spectrometry (EDS) using a Silicon Drift Detector (SDD)        with a counting rate of about 80,000 counts per second. From several        dozens to several hundreds of inclusions were analysed per sample,        depending on their cleanliness. The detection limit is estimated at        about 0.5%wt, linked to an accuracy error of 10%. This error is 2% for        elemental amounts above 1%wt (Dillmann &#38; L’Héritier, 2007).        Samples were analysed by taking into account all major elements        potentially contained in non-metallic inclusions. Results are        expressed by the following oxides: Na2O, MgO,        Al2O3, SiO2, P2O5, SO3, K2O, CaO, TiO2, Cr2O3, V2O5, MnO and FeO.        The chemical composition of slag inclusions is        analysed by a multivariate statistical treatment following the process        proposed by Disser et al. (2014), which helps        to determine their formation conditions (smelting or forging stages).        Among inclusions interpreted as formed during the smelting stage, a        dozen were submitted to trace element characterization by Laser        Ablation-ICP-Mass Spectrometry (LA-ICP-MS) using an Element XR (Thermo        Scientific) quadrupole analyser. The frequency of the Nd: YAG laser        (wavelength 266 nm) is set at 7Hz. The ablation diameter is set at 80        µm. The following isotopes were quantified: 9Be,        28Si, 45Sc, 47Ti, 51V, 52Cr, 59Co, 60Ni, 63Cu, 66Zn, 69Ga, 72Ge, 75As, 85Rb, 88Sr, 89Y, 90Zr, 93Nb, 95Mo, 108Pd, 118Sn, 121Sb, 133Cs, 137Ba, 139La, 140Ce, 141Pr, 146Nd, 147Sm, 153Eu, 157Gd, 159Tb, 172Yb, 178Hf, 181Ta, 182W, 208Pb, 232Th, 238U. Accuracy errors are        calculated for each analysis sequence, and are estimated between 5 and        20% given the nature of the element and its concentration in the        inclusion (Gratuze, 1999; Gratuze et al.,        2001).        The characteristic chemical signature of inclusions        is defined according to an element list selected by S. Leroy et al. (2012) and Disser et        al. (in press): Mg, Al, Si, Ca, Mn, Y, La, Ce, Pr, Nd, Sm, Eu,        Gd, Th, U. A reference set, composed of 188 ore and smelting slag        analyses, was established for the Lorraine region for provenance        determination.        This study also used radiocarbon dating of ferrous        alloys by accelerator mass spectrometry (AMS). An experimental        methodology has been developed recently to efficiently extract the        carbon from carbides in steel alloy matrices (S. Leroy et al., 2015). About 1 mg of carbon has to be        extracted to proceed with dating, which corresponds to the sampling of        about 250 mg 0.4%wt C hypoeutectoid alloy.              3. Results        Macroscopic-scale observations indicated that some        clamps had been crafted by welding two metal pieces together in order        to obtain a sufficient length. Metallographic examinations and        microanalyses of non-metallic inclusions were done on eleven selected        clamps to determine the microstructural and chemical characteristics        of each part.                  Metallographic examinations          The metal structure of the analysed clamps does          not vary that much. They all consist of a ferritic matrix, except          510A1. Only a few carburized zones are observed locally. Ghost          structures are observed in the ferritic parts of seven artefacts,          indicating a heterogeneous distribution of siderophile elements in          the metal. These structures are generally linked to phosphorus          (Goodway &#38; Fisher, 1988; Neff &#38; Dillmann, 2001; Stewart,          Charles &#38; Wallach, 2000; Vega, Dillmann, &#38; Fluzin, 2002).          This particular element, whose presence in metal is due to the          smelting of phosphoric ores, has often been employed in previous          studies as a criterion for coarsely determining the origin of          metallic products, prior to a more precise determination (Buchwald          &#38; Wivel, 1998; Desaulty et al., 2009; S. Leroy et al., 2012;          Pagès, Dillmann, Fluzin, &#38; Long, 2011; S. Paynter, 2006).          All cross-sections show a metallic matrix          organized in longitudinal bands distinguished by the size of the          ferrite grains, or by the presence or absence of ghost structures          (Figure 2). This organization highlights the forging sequences,          which mainly consist of deforming the iron following the          longitudinal axis to draw the metal bar out. Clamp 510A1 also shows          a banded structure, which is described precisely by Tylecote &#38;          Gilmour (1986), Piaskowski (1987) and Blakelock &#38; McDonnell          (2011). In this case, an alternation of more or less carburized          bands is visible, from 0.1 %wt hypoeutectoid alloy to eutectoid          steel. The main metallographic features of each sample are          summarized in Table 2. Average carbon rates were calculated          following the method defined by Pagès et al.          (2008) and L’Héritier et al. (2013). Visible          surfaces of each carbon content range ([0.02%wt C; 0.1%], [0.1%;          0.3%], [0.3%; 0.5%], [0.5%; 0.7%], [0.7%; 0.9%]) were measured by          image analysis. The proportion of carburized zones was determined,          given as the ratio between surfaces of alloys superior to 0.3%wt C          and the total surface observed.          Figure 2: Micrographic photograph showing the          alternation of ferritic bands distinguishable by the size of grains,          and by the presence of ghost structures / Figure          2 : Cliché micrographique montrant          l’alternance de bandes ferritiques qui se distinguent par la taille          des grains, ainsi que par la présence de structures          fantômes                                          Table 2: Main metallographic features of the          examined clamps / Tableau 2 : Synthèse des          caractéristiques métallographiques des crampons                                          All clamps show low amounts of inclusions, in all          cases lower than 5% of the observed surface. This cleanliness          nevertheless varies considerably with some samples being very clean          (0.1% for part 2 of clamp 251A1), while others contain about 4.5%          inclusions (510A1). It is interesting to notice that clamps 251A1,          510A1 and 1219A2 are each formed by two bars clearly showing          distinct metallographic characteristics. Inclusions show three main          petrographic features. The first presents a very high proportion of          wüstite (FeO), visible as large globules. These inclusions are          mainly visible in the vicinity of the welding lines, though they may          be found in some cases within the metallic masses (clamp 100A1). The          second feature is dominant within the sample set. It consists of a          fayalitic matrix, generally finely crystallized, but lathes are also          observable. This matrix contains variable amounts of wüstite          globules and dendrites. Some spinels (magnetite Fe3O4, hercynite FeAl2O4) presenting a characteristic          angular shape are locally visible in the fayalitic matrix. A totally          vitreous slag forms the last feature. Most inclusions have an          elongated shape, and are aligned following the longitudinal axis of          the cross-sections, which is consistent with the banded organization          of metallographic structures. More squatty shaped inclusions with          irregular contours are observable locally. Two clamps, 489A1 and          510A1, contain many inclusions of this type, concentrated in          relatively confined areas. Their density, along with the shape of          the inclusions, indicates that the metal of the two clamps is          relatively coarse, and did not benefit from intensive forging          work.          Microscopic observations, particularly the          presence of ghost structures in some cases and the evidence of          welding of two metal pieces in others, reveal a relative          heterogeneity among the clamp set. These differences indicate that          different raw products were used for crafting the artefacts.          Furthermore assembling metal pieces to produce these reinforcements          may seem surprising given their relatively low weight. They would          indeed have been easily obtained from one single bloom. This          statement, along with the reuse of stone blocks mentioned above,          further supports the practice of metal recycling to produce the          clamps. These preliminary conclusions and hypotheses led to the          subsequent chemical characterisation of slag inclusions, as well as          radiocarbon dating of two ferrous reinforcements.                          Chemical characterization of non-metallic          slag inclusions          Energy dispersive spectrometry analyses are          representative of each cross-section observed in terms of the number          of slag inclusions analysed, but also regarding their distribution          and petrographic features. The aim of this analytical step is to          consider all inclusion categories, whether they were formed during          the smelting operation or at later stages (refining or smithing).          Linking each inclusion to one of these operating steps relies on          statistical treatment of their chemical features, using a          multivariate method proposed by Disser et al.          (2014). The data treatment is performed on the main non-reduced          compounds of slag. Its objective is to classify inclusions regarding          elemental ratios implying particularly Mg, Al, Si, K, Ca, and Mn.          These ratios are expressed by the logratio transformation procedure          developed by Aitchison (1982, 1986). Data classification is          performed by Hierarchical Cluster Analysis employing Ward’s method.          In order to evaluate the classification relevance, the inclusion          groups created by the analysis are compared through bivariate plots          using raw elemental ratios. According to statements made by          Charlton et al. (2010) and by Dillmann &#38;          L’Héritier (2007), these plots distinguish inclusions formed by          using fluxes or addings during smithing stages from endogenous          inclusions formed during the smelting stage. The example displayed          in Figure 3 shows results obtained by applying this method to the          case of clamp 251A1. By considering both chemical and petrographic          information, it may be asserted that the red and green groups are          located near a major welding line visible on the median axis of the          cross-section, and are therefore generated during post-smelting          stages. This is confirmed by a high Si/Al ratio, indicating the use          of a sandy flux type. Inclusions attributed to the orange group,          mainly distributed within the two assembled metal pieces, are          probably subject to a phase segregation (Dillmann &#38; L’Héritier,          2007), which in this case seems to result in an aluminium          deficiency. Only inclusions attributed to the blue group are          associated with ore smelting, and carry the specific chemical          information necessary for identifying the origin of the metal.          Figure 3: Interpretation of major element          chemical features of the slag inclusions analysed on the 251A1          cross-section / Figure 3 : Interprétation de la caractérisation chimique en          éléments majeurs des inclusions du crampon 251A                                          Upper part: dendrogram showing the four          classes defined by multivariate analysis; lower part: bivariate          description of inclusion classes; middle: distribution of slag          inclusion classes on the cross-section. / En          haut : dendrogramme montrant les quatre classes d’inclusions          définies par l’analyse multivariée ; en bas : description bivariée          des classes d’inclusions ; au milieu : localisation des classes          d’inclusions sur la section polie.          This process was applied to all the clamps          analysed by SEM-EDS. Some of the inclusions interpreted as formed          during ore smelting underwent a trace element chemical          characterization by LA-ICP-MS (Centre Ernest Babelon – UMR 5060          IRAMAT, Orléans). In order to describe as well as compare the          chemical signatures of the clamps, a Principal Component Analysis          was applied. Fifteen log-ratios, involving the following elements:          Mg, Al, Si, K, Ca, Mn, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Th, U, were          employed to describe the 80 inclusions considered. Figure 4 shows          the first two factorial planes (and therefore the three factors          carrying most of the variance), representing 69.8% of total variance          expressed by the chemical data.          Figure 4: (F1-F2) and (F1-F3) factorial          planes of PCA performed on the logratios defining the chemical          signature of the inclusions analysed for each clamp / Figure 4 : Plans (F1-F2) et          (F1-F3) de l’ACP réalisée sur les log-ratios définissant la          signature chimique des inclusions analysées pour les          crampons                                          The description of the inclusion chemical          signature, relying on both major and trace elements, confirms that          the metal used to produce the clamps does not come from a single          source. At least two artefacts (215A1 and 510A1) were produced from          iron pieces showing chemical signatures clearly distinct from the          sample set’s main profile. It is also interesting to recall that, in          addition to its singular chemical characteristics, clamp 510A1 also          shows distinct microstructural features, such as relatively high          carbon-content. Furthermore, the slag inclusions have a low iron          content (about 10%wt Fe) compared to the other clamps (from c. 30%wt          to 60%wt). These features suggest that the metal of 510A1 was formed          in distinct smelting conditions, which favoured a better reducing          rate for the iron oxides. The two clamps presenting distinct          chemical characteristics are also two of the three artefacts showing          evidence of welding. Both microstructural and chemical analyses          point out the specificity of some clamps within the sample set. This          will be further discussed below. Finally, the chemical features of          the clamps indicate that the building yard had acquired metal from          multiple sources, either provided by metal recycling or by primary          distribution networks.          The second alternative will be considered first.          The bridge building yard occurred, as mentioned in the introduction,          amid an active ironworking environment, as several workshops were          producing iron in central Lorraine during Carolingian times.          Furthermore, recent research demonstrates that many areas in eastern          France were involved in iron production in the late Early Middle          Ages (Berranger, 2014; Disser, 2014). These production complexes          constitute potential metal providers for the building yard. A          chemical database managed by the Laboratoire Métallurgies et          Cultures, including especially the PalSid database (Leroy, 1997;          Ploquin, 1994 ; Leroy, Merluzzo, Le Carlier 2015) and the recent          results of a PhD thesis focused on this area, has served as a          repository for provenance determination. More precisely, it          establishes the specific chemical signature of smelting activities          linked to the exploitation of six distinct iron ores within          Lorraine. The chemical domains associated with the smelting of each          of these ores were compared and distinguished from each other. Those          distinct chemical entities, qualified as “production sets”, are          displayed in Figure 5. Potential chemical compatibilities between          the clamps and the production sets will be evaluated to determine          whether any of the local production centres could have provided the          metal.          Figure 5: Localisation of the main          ferriferous deposits surveyed in Lorraine, and of the smelting sites          characterised chemically / Figure 5 : Localisation des principaux gîtes ferrifères connus en          Lorraine et des sites de réduction de minerai caractérisés          chimiquement                                          The colour coding corresponds to the          production sets evidenced by (Disser, 2014). / Le          code couleur correspond aux ensembles de production mis en évidence          dans Disser (2014).          A two-step inferential statistical approach (S.          Leroy et al., 2014) was applied to question          chemical compatibility between the slag inclusions and the          production sets from Lorraine. The first stage relies on combining          PCA and HCA on both the inclusions and the production sets. It is          performed to determine, from among the chemical repository, which          production set(s) appear(s) as the most probable metal provider(s).          An iron product is de facto considered to be          chemically compatible with any of the production sets if they are          attributed to the same cluster by the HCA classification. Then a          second PCA-HCA combination is applied, but on a limited dataset          including exclusively each couple [clamp/potential production set]          defined by the first step of the inference. If the inclusions and          the potential production set are distinguished by this          classification, then the metal was not produced by the corresponding          production centres. Otherwise, the production set can be considered          with good reliability to be the metal provider. Nevertheless, recall          that since some other production sets that are not chemically          surveyed may share the same signature, the origin can only be          asserted by matching several (chemical, archaeological,          historical,…) information sources. The first inferential step shows          that the metal of nine clamps was not produced by any of the          production sets known for early medieval Lorraine (Figure 6). The          metal of clamp 251A1 may have been produced by the production set          linked to the smelting of a siderolithic ore called “fer fort”,          whose deposits are mainly located in the northern part of the          Moselle Valley. Finally, clamp 510A1 proved to be chemically          compatible with the production set related to the smelting of an          oolitic ore called “minette”, whose vast deposit, stretching over          one hundred kilometres, was intensively exploited during medieval          times.          Figure 6: Dendrogram showing the result of          the hierarchical clustering performed on the chemical signature of          each clamp and on the chemical domains of the production sets          identified in Lorraine / Figure 6 : Dendrogrammes présentant les résultats des          classifications ascendantes hiérarchiques réalisées sur la signature          chimique des onze crampons, ainsi que sur les domaines chimiques des          ensembles de production identifiés au sein de l’espace          lorrain                                          These potential origins are nevertheless          invalidated by the second classification, since inclusions are          clearly distinguished from the potential production sets (Figure 7).          Results obtained at the end of the multivariate process suggest that          none of the analysed metal pieces were produced by any of the          production sets evidenced for Lorraine in the Early Middle Ages. The          hypothesis of a local metal supply appears to be disproven. These          results will be discussed more thoroughly below.          Figure 7: Dendrogram showing the results of          the hierarchical clustering performed to assert the provenance          hypotheses regarding clamps 510A1 and 251A1 / Figure 7 : Dendrogrammes          présentant les résultats des classifications ascendantes          hiérarchiques réalisées sur les inclusions des crampons 251A1 et          510A1, ainsi que sur le domaine chimique des ensembles de production          candidats                                                          Dating of two clamps          Considering macro- and microscopic observations,          the possibility of recycling used metal to produce the clamps was          also considered. Proof of the dismantling of Roman monuments has          been provided by the reuse of lapidary elements coming from the vicus of Scarponna and          surrounding necropolises, suggesting that the metal used by the          bridge building yard could also have been a product of architectural          spolia. Only two clamps (510A1 and 256A1)          contained iron carbides in sufficient amounts to perform radiocarbon          dating. Two measures were performed for each clamp. The results are          shown in Figure 8.          Figure 8: Radiocarbon dating, after          calibration (using IntCal 13), of clamps 510A1 and 256A1 / Figure 8 : Datation          radiocarbone, en âge calibré (d’après IntCal 13), des crampons 510A1          et 256A1                                          The measures obtained from the two samples from          clamp 256A1 are coherent and indicate that the metal is contemporary          with the bridge building, at the end of the 8th          or 9th century. It can thus be assumed that in          this case the metal was in circulation as the building took place.          Measures on clamp 510A1, formed from two assembled metal pieces, are          on the contrary clearly different, and both precede the building.          The first would have been produced during Late Antiquity or the          Early Middle Ages (5th-6th          c.), while the second is dated from Merovingian times (7th-8th c.). These results          indicate that this clamp was indeed formed by assembling “old iron”          obtained by recycling.                      4. Discussion        The study performed on some ferrous reinforcements        unearthed by the excavation of an early medieval bridge at Dieulouard        provided a rare opportunity to explore the metal supply strategies of        monumental building yards during Carolingian times. The fact that        sizeable smelting activities took place at this time in central        Lorraine led to the hypothesis that local and regional exchange        networks provided the supply of metallic materials.        This privileged hypothesis was rejected by the        archaeometrical study. It is unlikely that the metal used to make the        clamps was produced by workshops exploiting local ores, not even the        aalenian oolitic ore deposits (“Minette”) that are located only few        kilometres from the bridge. In general, the chemical features of the        clamps do not correspond to any currently known iron production set        for the Lorraine area. While it cannot be completely ruled out, the        possibility of a metal supply provided by an undiscovered local        ironmaking complex is small, due to the significant number of surveys        and excavations conducted in this sector2. Furthermore several distinct chemical signatures have been        identified among the sample set analysed. This statement leads to the        assumption of a multiplicity of iron sources, as well as more complex        acquisition modalities than expected.        What were the potential metal sources? A first        possibility would be that metal was obtained through a large-scale        market relying on multiple iron production centres characterized by        distinct chemical signatures. Nevertheless, the results obtained        through this study favour the recourse to material salvaging. Whatever        the chronological context, recycling appears to be a means of material        acquisition whose importance should not be underestimated. For        instance, written sources highlight the importance of this phenomenon        during the Late Middle Ages (Dillmann &#38; L’Héritier, 2009;        L’Héritier et al., in press). Bernard (2009)        discussed the salvaging of materials at the end of the Roman Empire        and through succeeding periods. This investigation demonstrates that        the salvaging of architectural metal was a full-fledged activity        practiced in a rational way. The retrieval was sometimes performed        opportunistically on ruined buildings, but in other cases it was        carried out in a planned manner on still-functional buildings,        carefully stripped of their metallic elements. The example of Letôon        in Lycia accurately illustrates this activity (Bernard 2009). The        location of an early Christian church, the temple was initially        stripped of its sole colonnade. Some evidence gathered from lapidary        elements (entablatures and column drums) suggests that metal salvaging        was the main motivation. Meanwhile probe holes were dug into        still-standing walls, at the exact location of fastening elements.        Similar observations have been made in the city of Rome on the        Pantheon, as well as on the temple of Antoninus and Faustina. Of        course profane buildings were not spared either, as evidenced by the        facade of the Colosseum, which is literally riddled with holes. The        latter building can be considered as an actual “mine”, since more than        300 tons of metal would have been implemented in its masonry.        The bridge at Dieulouard accurately illustrates        this phenomenon in Lorraine during the Early Middle Ages, at least        regarding the lapidary elements provided by the dismantling of the        monumental complex of the Roman vicus of Scarponna, as well as the surrounding necropolises        (Boulanger &#38; Gucker, 2008). Given this context, it is conceivable        that some of the metallic elements used by the building yard may have        been obtained in the same way. Although the radiocarbon dating        available for the ferrous reinforcements from Dieulouard does not        currently validate an origin from Late Antiquity, it indicates a        reliance on metal salvaging for supplying the building yard. But was        the metal obtained by stripping architectural elements, or by        recycling “old iron” such as worn-out tools? The first possibility is        preferable in our opinion, given the very distinct “life expectancy”        of ferrous objects according to their function. Architectural iron can        conserve its integrity for centuries, while the expected lifetime of        agricultural tools does not exceed a few years, according to        ethnographical studies led on African communities (Serneels, 2007).        Moreover some of the clamps, including 256A1, appear to be        contemporary with the bridge construction, and could have been        provided by trading networks. This possibility is questionable, since        the chronological resolution of radiocarbon dating is not sufficient        to assert whether the metal would be directly provided by primary        trade, or by salvaging “old iron” still in use. Taking into account        all the observations made on this set of ferrous reinforcements,        recycling nevertheless appears dominant.        Evidence of this activity at Dieulouard contributes        to defining the value attributed to iron during the Early Middle Ages,        reflected by its acquisition modalities. It has to be stressed that        early medieval iron has been traditionally considered a rare material        whose crafting would have been the preserve of few craftsmen due to a        relative technological regress (for example Chapelot &#38; Fossier        [1980, p. 24-25] or Duby [1973, p. 22-25]). This conception, relying        on the assumed perception of a relative material and intellectual        pauperization, has been questioned by more recent research (Arnoux,        1993, p. 16-17). The value accorded to ironmaking activities and        metallic equipment by the Carolingian documentation cannot be invoked        to assert iron rarity in material culture, especially for agricultural        and artisanal spheres. This is moreover supported by recent        archaeological findings, especially excavations of metallurgical        workshops (M. Leroy, 2008; M. Leroy et al.,        2015). They reveal the diversity of ironworking organization forms, as        well as the importance of production volumes. This conveys the        impression that iron was relatively easily acquired, that its        production was carried out with expertise at least equal to that of        Roman craftsmen, and that the means of production met the demands of        the iron market during Carolingian times. What advantage would be        gained, at least in domestic, agricultural and artisanal spheres, from        acquiring long-range-traded iron whose use did not require a priori specific qualities? Furthermore,        relatively easy access to this material would not prevent methodical        metal salvaging from buildings, which were perhaps first and foremost        dismantled for acquiring building stone. Beyond saving by not buying        fresh metal, significant savings in ironmaking and smithing efforts        would also be made. Dismantling of ancient buildings and salvaging of        metallic elements would not be, in this case, the doings of craftsmen        driven to extremes by the rarity of metal. Rather it would have been a        full-fledged activity, contributing to the early medieval economy, and        maybe adapted in this case to a specific use, masonry reinforcement in        monumental architecture. Recall that salvaging Roman ferrous clamps        would have enabled almost immediate reuse by the bridge building yard,        without much smithing work. The value of the work would prevail, in        this case, over the intrinsic value of the material.