Mineralogical and chemical composition of transport amphorae excavated at Locri Epizephiri (southern Italy)

Journal of Cultural Heritage 2 (2001) 229−239 © 2001 Éditions scientifiques et médicales Elsevier SAS. All rights reserved S1296207401011207/FLA

Mineralogical and chemical composition of transport amphorae excavated at Locri Epizephiri (southern Italy) Marcella Barra Bagnascoa, Antonella Casolib, Giacomo Chiaric, Roberto Compagnonic, Patrizia Davitd,1, Piero Mirtid* a

Dipartimento di Scienze Antropologiche, Archeologiche e Storico-territoriali, Università di Torino, Via Giolitti 21/E, I-10123 Torino, Italy Dipartimento di Chimica Generale e Inorganica, Chimica Analitica, Chimica Fisica, Università di Parma, Parco Area delle Scienze 17A, I-43100 Parma, Italy c Dipartimento di Scienze Mineralogiche e Petrologiche, Università di Torino, Via Valperga Caluso 35, I-10125 Torino, Italy d Dipartimento di Chimica Analitica, Università di Torino, Via P. Giuria 5, I-10125 Torino, Italy b

Received 8 January 2000; accepted 3 May 2001

Abstract – Mineralogical, petrographic and chemical analyses were performed on sherds of transport amphorae (VI–III century B.C.) excavated at Locri Epizephiri, as well as on specimens of local manufacture. Examination of thin sections by the polarizing microscope and of X-ray powder diffraction patterns suggested that most of the amphorae could be assigned to local workshops since fossils and minerals as well as rock fragments are compatible with the crystalline basement of the Calabrian-Peloritanian arc. Chemical analysis, performed by ICP and flame atomic emission spectroscopy followed by multivariate treatment of data, further suggested that three groups of composition may gather most of the amphorae and the local reference products. These results point to a wide local production of transport amphorae in Locri, thus indicating that the ancient town was self-sufficient in producing agricultural foodstuffs, with limited dependence on imported goods. © 2001 Éditions scientifiques et médicales Elsevier SAS Locri Epizephiri / pottery / transport amphorae / provenance / optical microscopy / X-ray diffraction / emission spectroscopy / multivariate analysis

1. Introduction Located on the Ionian coast of Calabria, Locri Epizephiri was founded by inhabitants of the two Greek Locrides; the name of the town descends from Zephirion Cape, where the settlers had initially established [1]. Archaeological excavations carried out at the site of the ancient town unearthed a great quantity of ceramic material, chiefly amphorae and fine, domestic and cooking ware. These products, together with the discovery of kilns and tanks for clay sedimentation and with the presence of clay beds in the neighbourhood of the town, lead to suppose a fervent local ceramic production since the Archaic period.

*Correspondence and reprints. E-mail address: [email protected] (P. Mirti). 1 Present address: US Environmental Protection Agency, National Exposure Research Laboratory, Ecosystem Research Division, 960 College Station Road, Athens, Georgia 30605, USA

Of particular interest is the great amount of transport amphorae (more than a thousand fragments of rims, handles and bottoms) datable from the VI to the III century B.C. Their importance is due to the economic implications of this kind of pottery, which was mainly bought and traded for its content. These amphorae, in fact, were produced as containers of foodstuffs, mainly oil and wine, but also olives and salted products such as fish and capers. Consequently, transport amphorae supply important information about the ancient economy, from trading routes and agricultural resources to the standard of living of a country [2, 3]. To confirm such inferences one has to determine with certainty the centres of production of these containers, mainly conceived for trading. Archaeological examinations of profiles and pastes may not suffice for this purpose; it is therefore necessary to resort to chemical and mineralogical analyses. A common approach for placing sherds into a specific area of production is to compare their chemical

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and mineralogical composition with that of local raw clays. This method, however, may give inaccurate results if tempering material was added to the original clay, or different clays were mixed together; in addition, exhaustion or compositional alteration of a clay bed may represent another severe drawback. To avoid these problems, a diffuse practice consists in comparing the composition of the items of unknown provenance with that of reference groups made up of sherds of known origin. The aim of the present work was the determination of reference groups of transport amphorae produced in Locri Epizephiri. To this purpose, the mineralogical and chemical composition of 31 sherds of amphorae was determined and compared with that of reference objects of local production, such as kiln wastes and common ware.

2. Description of the samples Thirty-nine sherds excavated at Locri Epizephiri were studied for determining mineralogical and chemical compositions and building up reference groups of locally produced transport amphorae. Thirty-one were specimens of amphorae, which were selected out of the high number of excavated fragments as highly representative of the various classes found at the site of the ancient town. These were distinguished by their rim shape in three types (figure 1) [4]: a) a cuscinetto rigonfio, that is in the form of a swollen cushion obtained by folding in the terminal portion of the neck such as to create an air space (samples LA10, LA11, LA12, LA13, LA14); b) a mandorla, that is in the form of an almond (samples LA1, LA2, LA3, LA4, LA5, LA6, LA7, LA26, LA27, LA28, LA29, LA30, LA31, LA35, LA36, LA37); c) ad echino, recalling the profile of an architectural echinus (LA19, LA20, LA21, LA22, LA32, LA33, LA34). Cushion amphorae were dated, on stratigraphic evidence and on comparison with similar materials from other sites, from the VI to the V century B.C. Almond amphorae, which account for the highest number of fragments found in every stratigraphic context, were produced for a longer span of time, from the VI to the IV century B.C. Finally, echinus amphorae were dated from the IV to the III century B.C. On visual examination, most of the samples were considered local products, with some exceptions. In fact, samples LA8 and LA9 were considered IV century Corinthian amphorae of A’ type, while LA19 was supposed to be a fragment of a Corinthian B type amphora; furthermore LA22 and LA32, in spite of their echinus rim, were not assigned to local workshops, due to the deep red colour of the paste which is

Figure 1. Types of Locrian amphorae: (a–c) swollen cushion rims; (d–f) almond rims; (g) echinus amphora.

not matched by local products. Similarly, sample LA23, a piece with a triangular section rim and a dark brown colour, was considered a non-local product, even though of uncertain provenance. In addition to the fragments of amphorae, eight pieces were analysed as reference materials of local production. Three of them (LA15, LA16, LA18) were walls of amphorae and one (LA17) a vitrified handle found in a collapsed kiln, together with many other fragmented amphorae, datable from the IV to the III century B.C. The others were a stand for amphorae dated to the IV century B.C. (LA24), a vitrified waste (LA25), a kiln separator (LC1) and a fragment of common ware (LC2), for which a local production was certain. Table I summarizes the archaeological features of the analysed samples, together with the final assignment after the archaeometric investigation.

3. Experimental Sampling for thin sections, X-ray powder diffraction (XRPD) and chemical analysis was carried out

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Table I. Archaeological features of the studied sherds from Locri Epizephiri. Sample

LA1 LA2 LA3 LA4 LA5 LA6 LA7 LA8 LA9 LA10 LA11 LA12 LA13 LA14 LA15 LA16 LA17 LA18 LA19 LA20 LA21 LA22 LA23 LA24 LA25 LA26 LA27 LA28 LA29 LA30 LA31 LA32 LA33 LA34 LA35 LA36 LA37 LC1 LC2

Tipology

amphora with almond rim amphora with almond rim amphora with almond rim amphora with almond rim amphora with almond rim amphora with almond rim amphora with almond rim corinthian A’ amphora corinthian A’ amphora amphora with cushion rim amphora with cushion rim amphora with cushion rim amphora with cushion rim amphora with cushion rim fragment from kiln fragment from kiln fragment from kiln fragment from kiln amphora with echinus rim amphora with echinus rim amphora with echinus rim amphora with echinus rim amphora with triangular section rim stand for amphora waste from a damp amphora with almond rim amphora with almond rim amphora with almond rim amphora with almond rim amphora with almond rim amphora with almond rim amphora with echinus rim amphora with echinus rim amphora with echinus rim amphora with almond rim amphora with almond rim amphora with almond rim kiln separator common ware

Date Final (century assignment B.C.) V–IV V–IV V–IV V–IV V–IV V–IV V–IV IV IV VI VI VI VI VI IV–III IV–III IV–III IV–III IV–III IV–III IV–III IV–III –

local local local local local local local imported local local local local local local local local local local imported local local imported imported

IV – V–IV V–IV V–IV V–IV V–IV V–IV IV–III IV–III IV–III V–IV V–IV V–IV IV–III –

local local local local local local local local imported local local local local? local local local

with the aid of diamond coated cutters to avoid possible contaminations due to the use of metal tools; the superficial layer was removed to elude compositional differences with respect to the body, produced by contamination in the burial environment. For XRPD cut pieces were ground in an agate mortar; for chemical analysis they were reduced to finer powder in a grinding mill (Retsch MM2) using agate jars.

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For X-ray powder diffraction, a SIEMENS D5000 diffractometer, with graphite monochromatized copper radiation (λ = 1.54178 Å), was used. The monochromator was located on the diffracted beam thus reducing the intensity of the background due to fluorescent radiation. The background was further reduced by the use of zero background sample holders, consisting of a quartz single crystal properly cut to exclude Bragg reflections [5]. The patterns were collected in the 2θ range 5–50°. The phase identification was performed using the Diffrac AT set of programs (Socabim 1986, © Siemens 1991). Samples for chemical analysis were dissolved mixing 100 mg of pottery with twice the amount of lithium metaborate, putting the mixture in a graphite crucible and heating at 1 100 °C for 30 min. This led to the formation of a melted globule which did not wet the crucible walls and was dissolved in a polypropylene beaker containing 10% (w/w) nitric acid. After dilution, the obtained solutions were analysed by inductively coupled plasma optical emission spectroscopy (ICPOES) and flame emission spectroscopy (FES). Nine elements (Al, Fe, Ca, Mg, Ti, Mn, Sr, Ba and Cr) were determined by ICPOES and two (Na and K) by FES; in fact, ICPOES data for Na and K had a higher uncertainty due to the matrix complexity and interferences from the argon emission lines. A spectrophotometer Philips PU7450, operating in the sequential multi-elemental mode, was used for the ICPOES analysis, while FES determinations were carried out with a Perkin Elmer 5000 apparatus. Inductively coupled argon plasma provides an effective excitation source for either simultaneous or sequential multi-elemental determination of elements over a wide range of concentration in solution samples; it allows detection limits at the ng mL–1 (ppb) level for many elements with linear response curves over several orders of magnitude; it is a quite convenient method for archaeometric analyses, for its capability to determine a high number of elements, including trace elements, in a relatively short time (apart from sample dissolution) (see, for example [6–18]). Major disadvantages of ICPOES in archaeometric studies are to be found in its being a destructive technique and in the requirement of dissolved samples to achieve the best analytical performances. However, the former is not a great problem as long as the analytical samples may be withdrawn from isolated fragments, which cannot be reassembled into complete items, and 100 mg samples, or even less, are sufficient for the analyses.

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4. Statistical treatment of chemical composition data Data of chemical composition were submitted to a statistical treatment by multivariate chemometric techniques to verify the presence of groups of samples having similar compositional features. Two unsupervised methods were used to show the overall structure of the 39 samples in a multidimensional space: agglomerative Hierarchical Cluster Analysis (HCA), using the Ward’s method for building up dendrograms and Principal Component Analysis (PCA) using the non-linear iterative partial least squares (NIPALS) method to compute principal components. Analytical data were first subjected to a preprocessing procedure by autoscaling; in fact, when pattern recognition methods are applied to data of different order of magnitude, features with the highest absolute values are likely to dominate the classification process. Autoscaling elaborates data to zero mean value and unit variance, thus removing biases in the subsequent classification due to the presence of major, minor and trace elements in the data set. Another possible pre-processing procedure derives from considerations on element distribution in geological samples and consists of transforming data into logarithms [19]. However, while this approach seems to be justified in the case of trace elements [20], it may not be acceptable for major and minor elements [21]. Much of the conflict may be resolved if one takes logarithms for the former and untrasformed data for the latter, but the obvious problem arising from that is which elements are trace and which are major and minor [19]. Moreover, normal or log-normal distribution can only be assessed after the compositional groups have been recognized. The use of logarithms of data, either autoscaled or not, rather than untransformed autoscaled data in the classification of transport amphorae from Locri has been discussed elsewhere [22]. Due to the substantial agreement observed among the various classifications obtained there, in the present paper only untransformed autoscaled data will be taken into consideration. The statistical treatment of these data was performed using the Pirouette 2.03 statistical package by Infometrix Inc. (Woodinville, USA).

sults are summarized in table II, and compared with those obtained from XRPD. Microscopic examination enabled the evaluation of the relative amount of clasts with respect to the matrix and to determine the nature of the clasts, making a distinction among fragments of minerals, rocks and fossils. The clast grain size distribution appeared to be in most samples bimodal, with prevalence of both larger and smaller grains: this indicates the presence of clasts deriving from the original clay (the smaller ones) and from the added temper (the larger ones). Figure 2 shows a typical bimodal clast distribution, while figure 3 illustrates a sample containing only small clasts. In most samples, quartz (always the most abundant mineral), feldspars (both plagioclase and K-feldspar),

Figure 2. Photomicrograph of a thin section of sample LA4, with a typical bimodal distribution of minerals and rock clasts. Plane polarized light. ×30 magnification.

5. Results 5.1. Petrographic study One thin section for each sample was studied using a petrography polarizing microscope. The main re-

Figure 3. Photomicrograph of a thin section of sample LA19, with a typical unimodal fine grained clast distribution. Plane polarized light. ×30 magnification.

Table II. Results of petrographic and X-ray powder diffraction examination of sherds from Locri Epizephiri. L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A C C 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 1 2 × × × × × × × × × × × × × × × + × × × × × × × × × × × × × × × × × × × × × + × × + × × × × × ∼ × × × × × + × + × × × × × × × × × × × + × × × + × × × × × × × × × × ×

∼ ∼ + + + × × ×

× +

+ + + + + + × ∼ ∼ ∼ + ∼ + ∼ ∼ ∼ ∼ × × ∼ ∼ + ∼ ∼ ∼ ∼ + + + ∼ + + + + ∼ + + ∼ + ∼ + + ∼ ∼ + + ∼ ∼

× + + ∼ ∼ + + + ∼ ∼ ∼ ∼

∼ + + × +

∼ ∼ ∼ ∼ ∼ ∼ + × +

+ + × +

∼ × × ×

+ + + × +

∼ + × + ∼ + + ∼ + ∼ ∼ + × + + + ∼ ∼ + ∼ +

+ × × +

+ ∼ +

× + × +

∼ ∼

∼ ∼

∼ + + + + ∼ × + × × + × ∼ × × × × + × ×

∼ × × ×

+ ∼ × +

∼ ∼ + × × ×

∼ × ∼ +

+ ∼ ∼ + + ∼ ∼ + × × ∼ ∼ ∼ ∼ × + × ∼ + + ∼ × + ∼ + + ∼

× ∼ ∼ + +

× ∼ + ∼

× + ∼ + + ∼ ∼ ∼

× + + ∼ ∼ + +

× + + ∼

× ∼ ∼ ∼

× ∼ ∼ + ∼ + + ∼ ∼ +

× + × + ∼ ∼ ∼

× + + + + ∼

× + ∼ × +

× ∼ × + +

× + × ∼

× + ∼ ∼ ∼ + + ∼ ∼

× × × × × ×

× ∼ × +

× × × +

∼

∼

+ ∼ ∼ × + + + × + + + + × + × + + + ∼

+ ∼ ∼ × ∼ ∼ × +

× × × +

+ + + × × ×

+ + + + ∼ + + + + ∼ ∼ + ∼ + + ∼ + ∼ ∼ ∼

+ ∼ + ∼ ∼ + ∼ ∼

×

∼ ∼ × ∼ +

∼ + × +

∼ × ∼ + ∼

∼ ∼ + ∼ × ×

+ + × ×

∼ + × ×

∼ ∼ + + +

∼ + + +

∼ × × ×

∼

+ + + ∼ + + ∼ ∼

+ + ∼ ∼ ∼ + × × ∼ ∼

∼

∼ + × +

+

× ∼ + × +

∼ + ∼ ∼ ∼ ∼ ∼ × ∼ ∼

+ + + +

∼ + × ×

+ + × ×

+ × + × × × ∼ + ×

+ ∼ + + ∼ ∼ + + + + ∼ + ∼ ∼ ∼ ∼ + ∼ + + ∼ ∼ ∼ + ∼ ∼ × ∼ ∼ +

× + + +

× + ∼ + + × × ∼ + ∼ ∼ × ∼

× × × × ∼ × + × ∼ + + + ∼ × × ∼ + ∼ ∼ ×

× + + + × ∼

× + + + × ∼

× + + + ∼ + ∼

× + × × +

× + ∼ + + ∼

× + ∼ + + ∼

× × × × ∼ + + + ∼ ∼ ∼ + ∼ + + ∼ + + ∼ ∼ + +

M. Barra Bagnasco et al. / J. Cult. Heritage 2 (2001) 229–239

Petrography Quartz Feldspars Primary calcite in fossils Secondary calcite in fossils Fossil mould Fresh muscovite Decomposed muscovite Fresh biotite Decomposed biotite Igneous clinopyroxenes Fibrolitic sillimanite Melting of quartz Melting of feldspars Chamotte Vesicles Clast: small Clast: large Metamorphic rock clasts Plutonic rock clasts Carbonatic clasts X-ray powder diffraction Quartz Plagioclase K-Feldspars Calcite Micas Diopside Analcime

× × + + × × × × × × × × × × × × × × × + ×

+ = abundant; × = present; ∼ = in traces. 233

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micas (both muscovite and biotite) and calcite are the main phases. Since these minerals can be modified by thermal treatment, the following observed features are reported in table II: a) evidence, if any, of partial melting of quartz and feldspars; b) presence of preserved (fresh) muscovite and biotite, or pseudomorphical replacement of them by products of thermal breakdown; this observation is especially useful since it evidences the former presence of the minerals even in samples where the thermal treatment caused their disappearance; c) presence of primary calcite (the original biogenic one, making up the microfossil shells, mostly Foraminifera), or secondary calcite (reprecipitated after thermal breakdown); d) presence of fossil moulds left by biogenic calcite destroyed by heating. The occurrence of fibrolitic sillimanite, usually preserved within quartz grains, is also reported in table II, together with the presence of rare and small clinopyroxene grains. It is important to point out that these clinopyroxene grains, yellow to green in colour and sometimes with a marked compositional zoning, are detrital clasts, very likely of volcanic origin. Single grains of garnet (LA16), zircon (LA3), iron-rich epidote (LA27) and tourmaline (LA32) have also been sporadically observed. It is worth noting that in some samples the sheet silicate flakes show a preferred orientation parallel to the outer wall of the sherd, clearly produced by the lathe working process. In most samples, both metamorphic and magmatic rock fragments were identified. The metamorphics are two-mica phyllites and micaschists, whereas the igneous rocks are granitoids, some of them certainly of peraluminous nature, due to the presence of primary white mica and fibrolitic sillimanite. Most single grains of quartz and feldspars seem to derive from the disintegration of granitoid rocks, similar to those just described. Fragments of micritic carbonatic rocks and macrofossil shells also occur in several samples. In only a few cases angular fragments of a dark reddishbrown, highly oxidized material was observed, interpreted as ground pottery (chamotte). In most samples, vesicles are present, which may be subdivided into two types: the first one, spherical in shape, most likely represents bubbles produced by the gas released during firing from dehydration or decarbonation reactions; the second type, consisting of vesicles flattened and elongated parallel to the mica flakes preferred orientation, are most likely original air bubbles trapped during the clay mixing and modified by working. Many samples, especially the most porous ones, show a pervasive permeation of secondary calcite, which may encrust the vesicles and microfossil moulds.

5.2. X-ray powder diffraction study Quartz and feldspars are ubiquitous and the most abundant mineral phases. Diopside was observed in most samples, often in large amounts; it may be of secondary origin, formed during the firing process. Due to the very small crystal dimensions, this secondary clinopyroxene was not identified by optical microscopic examination. Calcite is present in all but three samples, in agreement with microscopy; as for the clay components, the presence of illite is often masked by the co-existing detrital muscovite. It is worth noting that 15 out of 39 samples showed the presence of analcime, a mineral characteristic of diagenetic conditions. 5.3. Chemical composition The chemical composition of the analysed sherds is given in table III. These data indicate that all the samples, with two exceptions, are made of highly calcareous bodies, with CaO and MgO contents in the range 8.4–15.5 and 2.0–3.2 wt%, respectively. The exceptions are represented by sherds LA22 and LA32, where both CaO and MgO do not reach or hardly reach up to 1 wt%. This is in agreement with the absence of calcite both in thin section and in the XRPD pattern. The two samples are also peculiar in their manganese content, which is within the 200–250 µg g–1 range, compared with contents exceeding 700 µg g–1 in the other sherds, except LA19, which is also unique from the petrographic point of view (see below). Figure 4 reports the Ward’s dendrogram obtained from the autoscaled analytical data, and figure 5 the PCA diagram (first three PCs, 73% of total variance). The dendrogram suggests the presence of three main groups of samples, which are labelled as A1 (formed by sherds LA5, LA7, LA9, LA13, LA14, LA15, LA18, LA20, LA35, LA36, LA37 and LC2); A2 (samples LA1, LA2, LA4, LA10, LA11, LA12, LA21, LA24, LA27 and LA34); and A3 (composed of LA3, LA6, LA16, LA17, LA19, LA26, LA28, LA29, LA30 and LA31). In addition, a small group is formed by samples LA25, LA33 and LC1, and another one by the above mentioned non-calcareous sherds LA22 and LA32. Finally, sherds LA8 and LA23 behave as chemical singles. Groups are more difficult to recognize in the PCA diagram, where only a few samples are set apart from the bulk of the others; they are LA8, LA15, LA18, LA22, LA23, LA32 and LA36. As the presence of outliers may bias the classification of the other samples, HCA and PCA were run again after removal of LA8, LA22, LA23 and LA32 (outliers in both classifications). This seems to sup

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Table III. Chemical composition of the analysed sherds from Locri Epizephiri. Sample LA1 LA2 LA3 LA4 LA5 LA6 LA7 LA8 LA9 LA10 LA11 LA12 LA13 LA14 LA15 LA16 LA17 LA18 LA19 LA20 LA21 LA22 LA23 LA24 LA25 LA26 LA27 LA28 LA29 LA30 LA31 LA32 LA33 LA34 LA35 LA36 LA37 LC1 LC2

Al2O3 (wt%)

Fe2O3 (wt%)

CaO (wt%)

MgO (wt%)

K2O (wt%)

Na2O (wt%)

TiO2 (wt%)

Mn (µg g–1)

Sr (µg g–1)

Ba (µg g–1)

Cr (µg g–1)

16.5 16.4 15.6 16.1 16.7 15.9 15.4 13.9 16.7 17.4 16.8 16.0 16.0 16.1 17.3 15.5 15.5 17.1 13.5 16.2 17.2 17.6 19.3 17.3 16.5 14.6 15.7 15.2 15.1 15.7 14.9 16.0 17.1 16.3 15.8 16.0 15.7 17.8 17.2

5.64 5.55 5.22 5.46 5.79 5.54 5.57 6.15 5.65 5.80 5.44 5.76 5.48 5.70 6.44 5.73 5.48 6.20 5.61 5.72 6.40 5.69 10.7 6.16 6.10 5.41 5.86 5.52 5.95 5.86 5.39 6.18 6.26 5.50 5.33 5.21 5.40 7.15 6.34

9.53 10.5 11.5 8.67 10.3 11.7 13.3 14.4 10.6 9.75 9.73 9.68 10.5 10.5 14.4 15.5 11.9 14.3 12.7 12.9 9.28 0.63 7.09 11.5 12.6 10.4 8.95 10.2 10.8 9.24 8.37 1.02 10.0 8.37 11.4 10.0 10.9 13.0 11.3

2.41 2.35 2.62 2.18 2.79 2.83 2.81 3.06 2.46 2.40 2.00 2.00 2.62 2.75 3.23 2.76 2.52 3.03 2.01 2.79 2.80 0.70 3.00 2.54 3.02 2.81 2.52 2.61 2.76 2.59 2.55 0.83 3.21 2.54 2.86 2.84 2.91 3.09 2.97

2.67 2.79 2.91 2.79 1.86 3.01 1.90 2.30 2.52 2.73 3.05 2.98 2.30 2.08 2.03 2.68 2.94 1.84 2.24 2.31 2.61 2.59 2.17 2.87 3.22 2.97 3.03 2.67 2.77 2.94 2.93 2.65 2.93 2.61 1.88 1.38 2.44 2.83 2.17

1.42 1.58 1.95 1.48 2.54 1.76 2.58 0.94 1.88 1.46 1.56 1.57 2.10 2.29 1.85 1.26 1.77 2.08 0.78 2.00 1.42 1.18 1.82 1.35 1.34 1.57 1.67 2.12 1.55 1.43 1.63 1.00 1.41 1.50 2.25 3.51 1.97 1.07 2.29

0.78 0.78 0.72 0.71 0.81 0.79 0.84 0.77 0.77 0.79 0.75 0.79 0.78 0.79 0.84 0.78 0.73 0.81 0.83 0.79 0.85 0.87 0.92 0.82 0.85 0.71 0.79 0.75 0.69 0.68 0.70 0.82 0.86 0.79 0.79 0.76 0.84 0.88 0.84

907 736 791 721 752 760 744 1 225 775 922 837 760 899 891 760 845 1 543 845 574 760 891 209 1 085 837 760 907 1 000 837 1 000 1 085 822 248 822 1 070 705 713 806 798 829

524 498 577 491 601 544 622 636 551 552 580 503 562 631 778 647 657 723 561 696 566 150 198 617 562 644 655 675 676 583 657 404 529 681 659 654 660 569 680

968 1 139 523 859 582 501 507 748 720 1 016 1 103 1 372 648 662 492 694 601 510 473 571 1 152 649 344 876 458 564 725 618 716 720 606 931 575 939 516 556 518 480 729

143 133 128 128 151 139 127 281 142 145 131 123 154 146 166 134 129 169 141 150 153 88 264 162 167 117 128 132 117 117 106 123 157 133 136 123 130 160 139

port a differentiation of sherds LA15 and LA18 from group A1 and leads to a rearrangement of few other sherds among groups A1, A2 and A3. All that does not change substantially the overall distribution of the samples, and, together with the information provided by the mineralogical data, may point to an actual lack of archaeological differentiation among most of these sherds.

6. Discussion The petrographic observations showed in the great majority of the samples, independently of the thermal

treatment received, the presence of fossil remains and mineral or lithic clasts compatible with a local origin. In particular, the presence of fibrolitic sillimanite in some quartz grains of magmatic origin indicates the peraluminous nature of the granitoids. Peraluminous granitoids, rather rare in the plutonic complexes, are particularly common in the crystalline basement of the Calabrian-Peloritanian arc, both in the Sila and in the Serre mountain ranges. Furthermore, in the Serre these granitoids are intruded in low- to medium-grade metamorphics equivalent to phyllites and micaschists found in the lithic clasts contained in the sherds. This association of plutonic and low-grade metamorphic

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Figure 4. Ward’s dendrogram obtained for sherds of transport amphorae from Locri Epizephiri.

Figure 5. Principal component diagram (first three PCs, 73% cumulative variance) obtained for sherds of transport amphorae from Locri Epizephiri.

rocks is typical of the Stilo unit exposed in the Locri hinterland. The XRPD patterns, as already pointed out, confirm the petrographic observations; a few features, though, should be discussed here in detail. The presence of hematite, for example, perhaps poorly crystalline and in small amounts, should be envisaged at least in the red sherds, in spite of the lack of evidence of this mineral in the XRPD patterns. Furthermore, analcime must have formed after firing, most likely during burial, since it should not have survived the firing process. From table II it is evident that the analcime-bearing samples are mostly devoid of fresh micas and primary calcite; on the other hand, for sherds made from calcareous clays but devoid of primary calcite, the presence of gehlenite should be expected. The presence or lack of gehlenite in sherds made from calcareous clays was thoroughly investigated [23–25]. In order to explain the failure to find gehlenite in ancient pottery these authors proposed the following three mechanisms: a) gehlenite did not form because well processed very fine grained clay was used; this is not the case of the amphorae under study, which show mostly a bimodal grain-size distribution which includes large clasts; b) gehlenite was formed initially but was later transformed into anorthite either by exposure to a very high temperature or by very long holding at maximum kiln temperature; this may well be the case for the vitrified waste LA25, which shows signs of high firing temperature but lacks analcime; c) gehlenite was formed initially but was later decomposed during the burial stage; in this case both calcium carbonate and zeolites of the analcime-wairakite series can be formed; both reactions may well explain the absence of gehlenite and the presence of analcime in the sherds from Locri. Notwithstanding the petrographic indication that most samples share a common local origin, the statistical treatment of chemical data suggested classification into three main groups. Inspection of analytical data indicates that this separation is mainly due to different contents of potassium, sodium and barium. In fact, higher sodium and lower potassium distinguish group A1 from groups A2 and A3, while the concentration of barium causes the separation between group A2 (higher content) and A3 (lower content). Even though sodium and potassium may have a fairly high discriminating power in classifying ceramic objects, they may have suffered ion exchange phenomena either in the original raw clay or in the sherd during burial. So, objects made with clays collected in the same place but at different times, or buried in different soils, may show dissimilar concentrations of these elements in spite of sharing the same

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origin. Similarly, barium may often show variability within a clay bed, so that its different content may not necessarily represent a definite proof of different provenance for groups generated by multivariate analysis. Two more sherds analysed as reference of likely local production are found in a small group which may be differentiated from the previous ones in the dendrogram; these are LA25 (the vitrified waste, not found in a kiln) and LC1 (the kiln separator), which cluster together with LA33 (a fragment of an echinus amphora) in figure 4. However, these three sherds still display mineralogical features peculiar to local products, not different from those of most of the other samples and are not separated from the bulk of the other sherds in the PCA diagram. One can observe that group A1 mostly gather amphorae with a creamy paste, while sherds in groups A2 and A3 are mainly characterized by orange bodies. Petrographic examination indicates that micas are well preserved in the latter, while diopside tends to be absent or present in small amounts in the XRPD pattern. On the contrary, in sherds of group A1 micas are altered, quartz and feldspars show signs of melting and the vesicles of round type (due to gas bubbles) are present. All the above suggests that the differentiation between groups A1, A2 and A3 in HCA may not indicate separate provenances but may be due to the use of clays withdrawn from various beds (or from the same bed in successive periods), to the adoption of different technological procedures or to the occurrence of post-depositional phenomena. This is supported by the presence in all three groups of at least one piece analysed as reference of certain local production. Indeed, data of chemical and/or mineralogical composition may lead one to challenge an actual assignment of sherds LA36, LA17 and LA19 to the above mentioned local groups. Fragment LA36 is characterized by a lower content of potassium and a higher content of sodium than the other sherds and is found rather apart in figure 5; this alone, however, may not suffice for supporting a non-local origin of this sample. On the other hand, thin section examination shows the complete absence of fossils, and XRPD pattern evidences the lack of calcite. These mineralogical features are common to LA22 and LA32 but, compared with these two sherds, sample LA36 exhibits definitely higher concentrations of calcium, magnesium and manganese. The high calcium content, in particular, is matched by the occurrence of diopside in the XRPD pattern. All these factors would lead one to suspect that this sherd may not be of local origin;

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however, its vitrified body strongly suggests a local production. Fragment LA17 shows a manganese content which is more than 1.5 times that of the local groups, and its mineralogical composition does not seem to associate it confidently with these groups. Even though sherds from kilns considered here may have a slightly different chemical composition than the other amphorae (consider, for example, sherds LA15 and LA18), their mineralogical composition is consistent with that of the other fragments of the local groups. The fact that this sherd is a fragment of a handle, which was added to the already formed amphora before firing, may lead one to suspect that a differently processed clay may have been used for its production. Mineralogical features of fragment LA19 are significantly different from that of the suspected local products, since it shows unimodal fine-grained homogeneous clast distribution. This may suggest that a completely different temper was added here, even though the clasts are so small that they cannot give any clue about their origin. Furthermore, this sherd shows relatively low contents of aluminium, sodium and manganese. These features suggest assigning the sample to a non-local workshop, and support the previous identification, based on the macroscopic examination, as a specimen of Corinthian B amphora [4]. Finally, sherds LA8, LA22, LA23 and LA32 (outliers in both figures 4 and 5) should not be assigned to local workshops due to their mineralogical or chemical features, or both. Mineralogical analysis of sherd LA8, considered a Corinthian A’ amphora on visual inspection [4], reveals the absence of clasts of metamorphic rocks, typical of the Calabrian arc; high chromium (about twice than in local products) is a peculiar chemical characteristic of this sherd, as it is of Corinthian pottery [26]; this sherd could then derive from an amphora used to import agricultural products from mainland Greece. In contrast, a second sherd, which had been classified as a Corinthian specimen on visual examination (LA9), does not display mineralogical or chemical features which can support such an assignment. These, in fact, are different from those of sample LA8 and do not distinguish LA9 from the sherds of the local groups. Sample LA9 should then represent a local product imitating a Corinthian A’ form, a frequent practice in southern Italy. Sherds LA22 and LA32 are peculiar due to the low content of calcium, magnesium and manganese; their singularity is confirmed by the mineralogical analysis, which reveals, beside the complete absence of microfossils, the presence of a tempering material of volcanic origin, which would exclude a local manufacture,

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as already suggested by visual examination. Probably they represent products from eastern Sicily, with which Locri Epizephiri was in continuous relationship. The last sample (LA23), an imported piece according to its stylistic features, is definitely separated from all the others by multivariate analysis of chemical data, due to a rather high content of aluminium and chromium and relatively low contents of calcium, strontium and barium. Even though the mineralogical analysis does not put into evidence a differentiation from the bulk of the local products, archaeological and chemical features may strongly suggest classifying it as an import.

7. Conclusions Mineralogical and chemical analyses confirm the archaeological inference that a large production of transport amphorae developed in Locri Epizephiri between the VI and the III century B.C. The chemical composition of a control group concerning the production of amphorae in Locri may be obtained from the analytical data presented here (table IV). Only excavated fragments of transport amphorae were considered in calculating mean element concentrations, leaving apart sherds analysed as reference products, as well as sherds LA19 and LA36. As expected, the greatest spread of data was displayed by potassium, sodium and barium, which are the elements responsible for chemical variability within the local products. The results of this paper confirm that a local production of amphorae was active in Locri Epizephiri

Table IV. Mean element concentrations (x) and corresponding standard deviations (s) calculated for transport amphorae probably produced in Locri Epizephiri (25 samples). Element or element oxide Al2O3 (wt%) Fe2O3 (wt%) CaO (wt%) MgO (wt%) K2O (wt%) Na2O (wt%) TiO2 (wt%) Mn (µg g–1) Sr (µg g–1) Ba (µg g–1) Cr (µg g–1)

x

s

s%

16.0 5.65 10.3 2.61 2.63 1.79 0.77 848 597 753 135

0.7 0.28 1.2 0.28 0.38 0.36 0.04 107 64 246 13

4.5 4.9 12.0 10.8 14.3 20.2 6.4 12.6 10.7 32.7 9.8

since Archaic times, either imitating forms circulating across the Mediterranean, or manufacturing peculiar forms such as the items with the almond rim. In Hellenistic times the activity of the local potters continued with the production of a new type, the echinus amphorae. Prevalently used as containers for trade, the amphorae could also be utilized for domestic storing of foodstuffs, as proved by the presence at Locri Epizephiri of numerous clay stands upon which they rested. The very large number of fragments found at Locri Epizephiri cannot be explained by the sole use for the town; one has to suppose that these containers were produced in the town and then transported to the country to come back filled with oil and wine. This implies a good agricultural output, such as to meet the internal demand, with limited recourse to imported products; these are testified by few amphorae coming from mainland Greece and Sicily. In this context, one cannot rule out the possibility that Locrian amphorae, with their content, were sent abroad; in fact items quite similar to those produced at Locri Epizephiri were found in other localities of southern Italy and Sicily [4].

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