The palaeo-Christian glass mosaic of St. Prosdocimus (Padova,Italy): archaeometric characterisation of tesserae with antimony- or phosphorus-based opacifiers

The present paper reports the results of archaeometric characterisation of the opaque tesserae, intentionally coloured with antimony- or phosphorus-based opacifiers, coming from one of the two only palaeo-Christian glass mosaics known in the Veneto region (Italy), i.e., the mosaic which decorated the votive chapel of St. Prosdocimus in Padova. In particular, 55 tesserae belonging to glass types “White”, “Blue”, “Yellow”, “Green” and “Brown” are examined here. The multi-methodological approach (SEM-EDS, EMPA, XRPD, imaging spectroscopy coupled, in some cases, with XAS) gave valuable insights into the complexities of palaeo-Christian glass mosaic production technologies. Two main groups are identified, one characterised by glassy matrixes and opacifiers (calcium or lead antimonate) typical of the Roman period and comprising all “White”, “Blue”, and “Yellow” tesserae and some “Green” ones, and the other characterised by glassy matrixes and an opacifier (calcium phosphate) typical of the 6th century AD, composed of “Green” and “Brown” tesserae. This suggests that, during that century there was a gradual change from older to “new” production technologies: although new opacifiers such as calcium phosphate started to be used, the frequent use of antimony-based ones (43/55 samples) supports the hypothesis that their systematic use was extended until the 6th century, although re-using old tesserae cannot be completely excluded. In addition, comparisons with compositional groups already identified in the “gold” tesserae of the same mosaic and tesserae from Ravenna demonstrate that both the same “base compositions” of the glass were used to produce transparent and opaque glass. This evidence, coupled with the results of the historical-artistic study, suggests technological connections between Padova and Ravenna, the capital of Byzantine mosaics in Italy. Micro-structural observations and chemical analyses of the Paduan antimony-based opacified glass demonstrate that different processes and raw materials were used in their production. Both in situ and ex situ crystallisation can be identified for calcium and lead antimonate in Paduan tesserae, whereas the production of tesserae opacified with calcium phosphate generally appears to be highly standardised. Although the opacifiers used in the Paduan tesserae support technological transitions, the colouring elements identified here, i.e., iron and manganese for white, yellow, brown and some green tesserae, cobalt for blue, and copper for blue and green, suggest continuity, because their use is widely testified in the production of both transparent and opaque glass artefacts dating from the Bronze Age until Medieval times, from whichever archaeological site the samples come. Peculiar relationships among the oxidation states of colouring elements, their contents in the glassy matrix, the types of opacifiers used, and the final colour of tesserae were identified. In addition, the correlations of cobalt and/or copper with other elements, together with identification of relics of colouring and “metallic” droplets, allow us to speculate on possible sources and production technologies. Lastly, identification of newly formed crystalline inclusions in tesserae also yields information on kiln temperatures, which ranged between 900 and 1150 °C, a range easily reached in the furnaces of the 6th century AD.     

Sedimentological and archaeological fabrics in Palaeolithic levels of the South-Eastern Pyrenees: Cova Gran and Roca dels Bous Sites (Lleida, Spain)

The comparative study of sedimentary fabrics in relation to archaeological fabrics in various levels of the sites of Cova Gran de Santa Linya (Middle and Early Upper Palaeolithic) and the Roca dels Bous (Middle Palaeolithic) has made it possible to analyse the formation dynamics of the deposits and determine the extent of disturbance of the archaeological levels by natural processes. To achieve this, diagrams and two- and three-dimensional indices were calculated from the azimuth and dip angle of natural clasts and artefacts. The results indicate that the sedimentary levels were formed mainly by planar fabric shape gravitational processes (low depositional angles), which differ notably from the archaeological fabrics they contain, characterised by a greater degree of isotropy. This difference in the fabrics would reflect human activity and indicates that the archaeological levels both in Cova Gran and Roca dels Bous have not been subject to significant natural modifications, and are preserved in situ.     

The biological and archaeological implications of the beetle Aglenus brunneus (Gyllenhal) in ancient faunas

The distribution and ecology, as far as they are known, of the Colydiid beetle Aglenus brunneus (Gyll.) are summarized and the significance of its records from archaeological sites considered. The supposition that A. brunneus originated in North America (Peyerimhoff, 1945) is questioned in the light of the ancient records. The species is used to illustrate some of the general principles and problems involved in the theoretical reconstruction of past environments from ancient faunas.     

Dietary ecology of extant guanaco (Lama guanicoe) from Southern Patagonia: seasonal leaf browsing and its archaeological implications

The analysis of dietary traits of ungulates through tooth microwear and mesowear has been applied to archaeological sites to investigate seasonal changes in settlements by hunter–gatherers. In this paper we propose to test the hypothesis that tooth microwear (combined to mesowear) is able to indicate seasonality in the diet of extant ungulates in arid habitats (semi-deserts or steppe). The material analyzed comes from six faunal monospecific assemblages of guanaco (Lama guanicoe) resulting from a mass mortality event in winter 2000 near the Cardiel Lake in Southern Patagonia (Province of Santa Cruz, Argentina). Mesowear results indicate that the guanacos from the Cardiel Lake area are mixed feeders, and thus, have a diet that shifts seasonally. Moreover, microwear analysis supports the hypothesis that tooth microwear is able to indicate seasonality in the diet of extant guanaco in arid habitats. The pattern is clear for the winter sample and needs to be confirmed for a summer sample. Consequently, tooth microwear is proposed as a new potential proxy for detecting seasonal occupation in archaeological sites in Patagonia and other arid environments.     

Characterisation of archaeological mortars and plasters from kyme (Turkey)

The present study focuses on the compositional characterisation of Roman, proto-Byzantine and Medieval mortars, sampled in the archaeological site of Kyme (Turkey), an Aeolian city, founded in the middle of the XI century BC by Greek populations. The mortars were studied through elemental (SEM-EDS, XRF), mineralogical (XRPD, De Astis calcimeter) and petrographic (polarised optical microscopy) analysis. The comparison between the samples allowed us to emphasise compositional differences within mortars of the same historical period.In particular, we detected the prevalent use of cocciopesto, which was used as a pozzolanic additive to create hydraulic mortars in the Roman and Byzantine period. The cocciopesto was used to improve the technological properties of an initially slaked lime. Furthermore, compositional similarities allowed us to attribute an unknown sample to the Roman period. Our study also pointed out the fact that the lower quality mortars belonged to the Medieval period. As a matter of fact, the most friable sample belonging to the Middle Ages turned out to be a mixture of clay, lime and volcanic sand.     

New archaeological and epigraphical material from Qana (South Arabia)

Excavations at Qana, the ancient port of the Hadramawt on the Indian Ocean, have been carried out systematically by a Soviet-Yemeni Expedition since 1985. Several houses, a storeroom, and probably a religious building have been excavated in the "Lower City". A rich collection of archaeological material has been obtained, including several hundred bronze coins; painted and inscribed fragments of texts in Greek datable to the fourth century AD; African and Mediterranean pottery. For the first time it is possible to reconstruct the history of a large South Arabian port belonging to the kingdom of Hadramawt. Furthermore, it has been demonstrated that Qana existed until the beginning of the Islamic era.     

The decomposition of starch grains in soils: implications for archaeological residue analyses

Recent research involving starch grains recovered from archaeological contexts has highlighted the need for a review of the mechanisms and consequences of starch degradation specifically relevant to archaeology. This paper presents a review of the plant physiological and soil biochemical literature pertinent to the archaeological investigation of starch grains found as residues on artefacts and in archaeological sediments. Preservative and destructive factors affecting starch survival, including enzymes, clays, metals and soil properties, as well as differential degradation of starches of varying sizes and amylose content, were considered. The synthesis and character of chloroplast-formed ‘transitory’ starch grains, and the differentiation of these from ‘storage’ starches formed in tubers and seeds were also addressed. Findings of the review include the higher susceptibility of small starch grains to biotic degradation, and that protective mechanisms are provided to starch by both soil aggregates and artefact surfaces. These findings suggest that current reasoning which equates higher numbers of starch grains on an artefact than in associated sediments with the use of the artefact for processing starchy plants needs to be reconsidered. It is argued that an increased understanding of starch decomposition processes is necessary to accurately reconstruct both archaeological activities involving starchy plants and environmental change investigated through starch analysis.     

The chert abundance ratio (CAR): a new parameter for interpreting Palaeolithic raw material procurement

Raw material provenance and procurement studies are an essential research line to infer landscape exploitation, mobility dynamics and territorial management among prehistoric hunter-gatherer groups. This paper proposes an original and intuitive method, the chert abundance ratio, aimed at quantifying lithic resource occurrence in the landscape while considering the geological natural factors of an area (chert-bearing formation extent, thickness, occurrence index, size and chert content). The resource availability can be statistically compared to any archaeological assemblage distribution to define the procurement strategies, whether generalist or selective, and the mobility patterns. The study area, the north-east of the Iberian Peninsula, focused in the Prades Mountains, represents a regional scenario with high chert disposal shared by several Late Upper Palaeolithic occupations. The discrimination of the procurement areas is used as a parameter for outlining the foraging radius and the territorial range, contributing to an understanding of several aspects of the settlement, such as site functions, occupation length or intensity and group size.     

Decorated prehistoric pottery from Castello di Annone (Piedmont,Italy): archaeometric study and pilot comparison with coeval analogous finds

Prehistoric pottery decorated with incisions or impressions filled with white and seldom coloured inlays is well documented in the archaeological literature, but the related in-depth archaeometric studies are sporadic. 43 decorated ceramic shards, dating from the Neolithic to the Bronze Age, and an Iron Age fibula from the archaeological site of Castello di Annone (Piedmont, North-Western Italy) were analysed with FTIR, Raman and XRPD for characterization of the ornamental pigments forming these inlays. Few white components were used as fillers, namely talc and bone ash (hydroxyapatite – Bone White), often as a mixture and seldom accompanied by other pigments (i.e. kaolinite and presumably secondary calcite). Comparison with freshly-heated biogenic hydroxyapatite proved that ancient Bone White pigment was calcined at about 900 °C. Such a process was kept separate from pottery firing as these white mixtures show absence of talc degradation by-products and sporadic presence of kaolinite, implying these ceramics were decorated only after firing in furnace. Actual presence of fluorapatite in bone ash could allow dating with the Fluorine Method, but lack of fluorine detection with SEM-EDS causes such an attempt to be impracticable so far. A pilot comparative study with a restricted but representative group (11) of coeval finds from other sites of Piedmont suggests that while recurrence of talc prevails in Castello di Annone from the Neolithic throughout the Bronze age, massive use of bone ash (Bone White) becomes widespread in the close Iron Age settlements, possibly consequent to a more efficient handling of its production technology.     

First results on thermally induced porosity in chlorite cooking vessels from Merv (Turkmenistan) and implications for the formation and preservation of archaeological lipid residues

Excavations at the ancient city of Merv in Turkmenistan have yielded a significant assemblage of ceramic and stone vessel fragments from contexts dating to the Sasanian and medieval periods (5th–13th centuries AD). Many of the vessel fragments are encrusted with apparent food residue deposits offering scope for organic residue analysis and the potential to compare the use of these two very different vessel types. To enable meaningful comparison we sought to establish whether the vessel stone (a talc-chlorite schist) can absorb and preserve organic residues indicative of past use. This paper reports the first investigation to address this question using standard methods for archaeological residue analysis coupled with study of the properties of the schist fabric and basic absorption experiments. The results demonstrate that heating during cooking, even at relatively low temperatures, modifies the stone microstructure by increasing its porosity. These pores enhance the absorption capacity of the schist fabric such that chlorite cooking pots can absorb and preserve sufficient organic residue to reflect the original processing of foodstuffs, as has been previously demonstrated for ceramic fabrics. Comparison of pore capacity, archaeological residue yield and experimental absorption indicates the significance of pore-size distribution for the relative retention and preservation of organic residues in these fabrics. The results of this study indicate that a wider range of archaeological material may be suitable for absorbed residue analysis than has previously been recognised. The findings also challenge previous assumptions concerning the relationship between the properties of chlorite vessels and their mode of use in Central Asia and Near East in antiquity.     

Guanaco (Lama guanicoe) isotopic ecology in southern South America: spatial and temporal tendencies, and archaeological implications

We synthesize and discuss available isotopic data on Holocene guanaco samples from southern South America, extending from Tierra del Fuego Island to northern Patagonia and the Pampean region. We evaluate temporal and spatial tendencies on the basis of 91 samples (mainly based on δ¹³C_collagen values), presenting implications for paleodietary research in archaeology. We conclude that there are no strong correlations with latitude in the macro-spatial scale, while there is a set of interesting patterns at smaller regional scales. These patterns lead us to evaluate the role of ecologic and topographic variables (e.g. canopy effect, variations in altitude, ecotones) in structuring isotopic variability. Finally, on the basis of the present analysis we suggest a number of hypotheses and perspectives for the use of stable isotopes as geographic tracers of guanaco distribution in the past, and specific implications for the paleodietary study of human samples.     

Alkaline cooking and stable isotope tissue-diet spacing in swine: archaeological implications

In this study we examine the effects of alkaline cooking on carbon and oxygen stable isotopic ratios of mineralized tissues from nine pigs raised on monotonous mixed C3/C4 vegetarian diets. Two sources of collagen (humerus and mandible) and two sources of apatite (humerus and enamel) were analyzed. Within each diet group, humerus and mandible collagens were found to record equivalent δ¹³C and δ¹⁸O ratios; however, enamel apatite was found to be enriched over bone apatite by 2.3‰ in carbon and 1.7‰ in oxygen. Alkaline cooking was found to slightly, but significantly increase the Δ¹³C_{collagen-diet} and Δ¹⁸O_{collagen-diet} of bone collagen. A similar trend towards enrichment was observed in bone and enamel Δ¹³C_apatite-diet and Δ¹⁸O _apatite-diet, but the differences were not significant. Observed isotopic shifts were consistent with increased nutrient utilization of the alkaline-cooked maize as compared to raw maize. In addition, a reexamination of the relationship between diet and tissue carbon isotopic values suggests that species and alimentary type should be considered when interpreting ancient diets.     

Weakening processes in thrust faults: insights from the Monte Perdido thrust fault (southern Pyrenees,Spain)

The Monte Perdido thrust fault (southern Pyrenees) consists of a 6‐m‐thick interval of intensely deformed clay‐bearing rocks. The fault zone is affected by a pervasive pressure solution seam and numerous shear surfaces. Calcite extensional‐shear veins are present along the shear surfaces. The angular relationships between the two structures indicate that shear surfaces developed at a high angle (70°) to the local principal maximum stress axis σ₁. Two main stages of deformation are present. The first stage corresponds to the development of calcite shear veins by a combination of shear surface reactivation and extensional mode I rupture. The second stage of deformation corresponds to chlorite precipitation along the previously reactivated shear surfaces. The pore fluid factor λ computed for the two deformation episodes indicates high fluid pressures during the Monte Perdido thrust activity. During the first stage of deformation, the reactivation of the shear surface was facilitated by a suprahydrostatic fluid pressure with a pore fluid factor λ equal to 0.89. For the second stage, the fluid pressure remained still high (with a λ value ranging between 0.77 and 0.84) even with the presence of weak chlorite along the shear surfaces. Furthermore, evidence of hydrostatic fluid pressure during calcite cement precipitation supports that incremental shear surface reactivations are correlated with cyclic fluid pressure fluctuations consistent with a fault‐valve model.     

The use of white marbles for sculpture in Roman Gortyn (Crete) as revealed by archaeometric analyses

Gortyn was an important Cretan town from the late Archaic to the Hellenistic period and then became one of the provincial capitals of the Roman Empire. It controlled the whole of Crete and Cyrenaica and was a flourishing centre of trade and agricultural products in the first centuries of our era. In more than 100 years, many portions of the Greek and Roman town were unearthed under the supervision of the Italian Archaeological School of Athens and a considerable number of stone artefacts found, many of them made of imported marble since the local variety was grey and of poor quality. Statuary and other prestigious marble sculpted artefacts found in Gortyn were sampled and subjected to archaeometric examination (by way of optical microscopy in thin section, powder X-Ray diffraction and mass spectometry for the determination of the C and O isotopic ratio) in order to identify the quarries they came from. The results obtained from the analysis of several dozen white marble objects have indicated the use of a quite wide variety of species including Parian (from Lakkoi), Pentelic, Thasian (dolomitic and calcitic) and (occasionally) Proconnesian marbles. The first three, especially Pentelic, were used for most of the statuary.     

The differential survival of native starch during cooking and implications for archaeological analyses: a review

Cooking makes foods more palatable and digestible, less toxic and suitable for longer-term storage. Starch granules usually undergo gelatinisation during cooking, resulting in the loss of native structure and morphology. Once fully gelatinised, starch is very difficult to recognise microscopically and to classify taxonomically, impeding identification of cooked starch in archaeological food residues. Gelatinisation involves a complex interplay between temperature, moisture content and the presence of solutes, lipids and proteins, as well as species-specific starch physicochemical properties. Understanding the influence of these factors, particularly moisture, on the degree and extent of starch conversion during heat treatment enables predictive models of native starch survival in archaeological samples based on cooking method and food type. The findings of this review indicate that differential native starch survival may significantly influence archaeobotanical reconstructions and interpretations of artefact function.     

The volcanic millstones from the archaeological site of Morgantina (Sicily): provenance and evolution of the milling techniques in the Mediterranean area*

The Morgantina archaeological area, inhabited from the Early Bronze Age, had its widest expansion from the fifth to the first century bc . The volcanic millstones found at Morgantina fall into three different groups on the basis of the milling technique: (i) saddle querns (known from the Middle–Late Bronze Age and Iron Age); (ii) rectangular hopper‐rubbers (Olynthian) millstones, the invention of which dates to the fifth century bc ; and finally (iii) Morgantina‐type rotary millstones (starting to be used from the fourth to the third century bc ). In order to determine the provenance of the raw materials (lavas) used for all these millstone types, we collected 38 very small rock samples for thin‐section modal mineralogy, petrography and major trace element composition. The results have contributed to classifying different lithotypes and distinguishing between provenance from Etna and the Hyblean Mountains, the two volcanic areas respectively north‐east and south‐east of Morgantina. Saddle querns are made of tholeiitic basaltic andesites from the Hyblean Mountains and transitional basalts, mugearites and hawaiites from Etna. The variety of sources of portable saddle querns, mostly used in households, indicate that there was no general preference for specific quarrying sites. By contrast, the rectangular hopper‐rubber and the Morgantina‐type millstones, which document the period of Morgantina's greatest prosperity, are almost completely made of hawaiites from Etna. The use of a specific lithotype (i.e., Etna hawaiite) for the more efficient rectangular hopper‐rubber and rotary millstones could be linked to the fact that these mills may have been operated in business establishments. It is worth noting that the Gornalunga river was, in antiquity, a waterway joining Morgantina to the final stretch of the Simeto river and then the Ionian coast. The best candidate areas for the millstone hawaiite quarrying sites from Etna are the far south‐western sectors of the volcano, along the Simeto Valley (i.e., the ‘Piano Provenzana’ Formation) or the inner suburb of present‐day Catania (i.e., the ‘Pietracannone’ Formation). The very efficient Morgantina‐type rotary millstones spread during the reign of Hieron II of Syracuse (275–215 bc ) in eastern Sicily and met the need for grinding large quantities of cereals during a relatively peaceful time and a period of agricultural development.