Petrographic Approach Research Articles

Petrographic Markers for Archaeometric Identification of Montjuïc Sandstone, the Flagship Stone of Barcelona (NE Spain)

The present study deals with a particular clastic rock from the Montjuïc hill exploited since Roman times in Barcino (present-day Barcelona (NE Spain)). Polarized and cathodoluminescence microscopies have been used to describe the main petrographic features of Montjuïc sandstones. Several characteristic provenance markers have been identified; among them the most specifically restricted to Montjuïc sandstone are the K-feldspar clasts with authigenic overgrowths. A petrographic survey oriented to the detection of such markers has been fruitfully applied to sculptures, architectural elements, mosaics, and pottery. The petrographic approach has demonstrated that some Roman heritage materials had been erroneously assigned to Montjuïc sandstone and the revision of all the pieces macroscopically assigned to this provenance is advised. The use of Montjuïc sandstone in Roman tesserae has been reported for the first time with interesting implications on previously unreported evidence of Roman extraction at the bottom part of the Montjuïc cliff. Finally, Montjuïc crushed sandstone used as pottery temper has been also reported in the productions of a medieval (12–13th century) workshop in Barcelona. This encourages the study of the distribution of pottery with this particular temper.

Provenance reconstructions. Article 1. Mineralogical and petrographic approaches and methods

Research subject.This is the first in the series of four articles, which aims to review existing provenance reconstruction tools.Methods and materials. The data obtained during evaluation of different sandstone allothigenous components was used as a basis for analysis. The data was collected from the Upper Riphean Zilmerdak Formation Bir’yan Member and the Upper Vendian Bassa Formation (Southern Urals); the Upper Devonian Kodinka and Ust’kodinka formations (Middle Urals); the Lower Cretaceous Sortym Formation (Western Siberian sedimentary megabasin, Bolshekhetskaya depression).Results. The sandstone composition patterns of the lithostratigraphic units under study allowed the most common provenance features to be established by means of comparing data obtained by various diagrams.Conclusions. It is established that only the Kodinka, Ust’kodinka and Sortym sandstone compositions can be used as a source for rock reconstruction analysis, while the Bir’yan and Basa sandstone compositions have undergone massive transformations.

Hydrocarbon potential and depositional paleoenvironment of a Middle Jurassic succession in the Falak-21 well, Shushan Basin, Egypt: Integrated palynological, geochemical and organic petrographic approach

The topmost Lower and Middle Jurassic formations of organic-rich clastics with minor carbonate deposits were recognized as very significant source/reservoir rocks in the North Western Desert of Egypt. Although several studies are devoted to their source rock characteristics and petroleum potential, the depositional paleoenvironment and paleoredox conditions are still poorly understood. In the current study, these sediments were assessed in terms of their organic matter richness, hydrocarbon generative potential and thermal maturity, total sulfur (TS) contents and organic petrographic characteristics. Depositional paleoenvironment was investigated using dinoflagellate cysts (dinocysts) and the composition of particulate organic matter along with organic petrographic characteristics. Redox conditions were assessed based on TS- total organic carbon (TOC) relationship and type of kerogen that was derived mainly from palynofacies analysis.TOC contents show fair to excellent generative potential of hydrocarbons mainly of kerogen type III (gas-prone). The thermal maturity, based on Tmax and Rr, indicates mature stage of oil window.Palynological analysis yielded poor to rich intervals of moderately-preserved, biostratigraphically useful dinocysts in the upper part of the Khatatba Formation. An assemblage of 81 species belonging to 54 genera of moderately diverse dinocysts, spores and pollen grains was identified. Freshwater algae, acritarchs and microforaminiferal test linings are sporadically documented within the studied interval. Based on the first downhole appearance (FDA) of the recovered marker dinocyts, the upper part of the Khatatba Formation was palynologically dated as late Bathonian-Callovian.The depositional environment was interpreted and three environments were deduced. The lower interval representing the topmost Ras Qattara and Yakout Red Shale Member was deposited in a fluvial-lacustrine environment, where oxic conditions prevailed as deduced from the color of reddish-brown sandstone and red shale. The middle interval spans Unit IIB, Kabrit and Unit III, which accumulated in a deltaic to shallow marine environment under dysoxic-suboxic settings. The upper interval covers Unit I and Unit IIA that have been deposited in a fluvio-deltaic to shallow marine with high paleoproductivity under suboxic conditions. One sample in the upper interval in Unit IIA reflected anoxic setting.

The cap rocks sealing the reservoir in the Węglówka oil field, sub-Silesian unit, Polish outer Carpathians: Petrographical approach

The Weglowka oil field is located in the outer Carpathians. The outer Carpathians are a region where hydrocarbons were discovered and exploited at the end of the nineteenth century in several dozen oil fields, which are relatively small. The Weglowka oil field is one of the largest in this region. In the 150 yr or so of hydrocarbon exploration in the area, more than 1 million t (>1,237,000 tons [>8,841,000 bbl]) of oil have been produced. Hydrocarbons are concentrated in Lower Cretaceous sandstones (Grodziszcze and Lgota sandstones) that form an anticline sealed by Upper Cretaceous marls called the Weglowka marls. These cap rocks are up to 600 m (2000 ft) thick. Because of the thrust-related exhumation, they were exposed at the surface and represent the youngest deposits in the region. The present work is focused on a detailed petrographic characterization of the Weglowka marls. This study allows petroleum geologists to better understand the evolution of porosity in these cap rocks and can serve as a foundation for the prediction of their sealing properties. The marls appear as a succession of interbedded red and green varieties, which occur in up to 2-m (6-ft)-thick beds. These beds are nonarenaceous, soft, and bioturbated. Grain size corresponds to approximately 80% clay and less than 20% silt fractions. X-ray diffraction (XRD) reveals that the marls contain, on average, 54% clay, 28% calcite, 16% quartz, up to 3% feldspars and, in red marls, 3% hematite. The XRD patterns of clay are typical of mixed-layer illite–smectite ([I–S]; 40% illite in I–S). The clay structures are dioctahedral with similar octahedral Mg and relatively high Fe3+ contents both in the red and green intervals. As revealed by standard petrography combined with high-resolution petrography performed through the use of a field emission scanning electron microscope, the marls have mudstone textures according to Dunham’s (1962) classification and are mostly composed of coccoliths and clay with rare nanoquartz. This rock may be considered an impure chalk. Sealing properties of the Weglowka marls are indicated by the specific surface area, porosity, pore size, and permeability, calculated using N2 gas adsorption, helium, and mercury porosimetry. The sealing potential is postulated to result from a combination of the following: (1) origin of components (i.e., deposition of minute calcareous bioclasts and volcanic material as a source for clay); (2) oxygenated sedimentary environment (as a result of the presence of oxygen in the sediments, burrowing caused the rocks to be homogenized); and (3) tectonic-induced clogging of pore space because of reorganization of clay flakes (the rocks were strongly tectonically deformed, which resulted in reduction of porosity in clay aggregates).

Structurally controlled growth of fibrous amphibole in tectonized metagabbro: constraints on asbestos concentrations in non-serpentinized rocks

The nucleation and concentration of asbestos in rocks are mostly associated with mechanisms of fibre formation, combined with the water-dependent mineralogical alteration produced during the serpentinization of ultramafic masses. Very little is known about the structural settings and tectonic histories that influence and control the occurrence of asbestos in non-serpentinized rocks diffusely embedded within tectonized ophiolitic suites. Focusing on a case history provided by a tectonized metagabbro from the Ligurian Alps (northern Italy), a multiscale structural–petrographic approach is used to investigate the relationships between rock fabric and fibrous amphibole growth within the metagabbro. Meso- to microstructural observations are used to document the role of structurally controlled fluid–rock interactions in localizing the growth of fibrous amphibole during ductile-to-brittle shearing (mylonitic foliation to shear veins). A qualitative structural scenario is provided to illustrate the growth of asbestos amphiboles in shear veins during the progression of shear deformation towards semi-brittle rheological conditions. The mechanisms of the structurally controlled growth of fibrous amphibole in non-serpentinized rocks imply an examination of the tectonic boundary conditions that are at the origin of the concentration of asbestos in ophiolitic rocks involved in orogenic belt construction.

Elucidation of Provenance, Palaeoclimate and Tectonic Setting of the Gondwana Sandstones of Arunachal Himalayas: A Petrographic Approach

The Permian Gondwana sequence of Arunachal Lesser Himalayas provides an excellent setup to study the provenance and associated tectonics during deposition due to its typical positioning at the margin of the Gondwanic Indian continent. Petrographic character of these Gondwana sandstones exposed in parts of East Siang and West Siang districts of Arunachal Pradesh and inferences on source rocks and tectonic setting are presented in this paper.

A petrographic approach to a newly found lignite outcrop from Bilene (Gaza, Mozambique)

A Pleistocene coastal lignite outcropping between the Muândeje Lake (Maputo Province) and Nhachuendezo Lake (Gaza Province) was recognized during geological mapping performed in 2009. However, these outcrops started to be investigated only in 2017 through paleontological fieldwork under the PaleoMoz Project (www.paleomoz.org). Here the chemical and petrographic compositions of a coal sample from this locality are reported. This new occurrence represents the first lignite occurrence from coastal Mozambique. The lignite is a Low Rank C (Lignite C) coal with a huminite reflectance of 0.248%. The results show that the lignite has high ash yield (46.5%, d); volatile matter (65.2%, daf), carbon (57.3%, daf), hydrogen (5.3%, daf) and nitrogen (2.3%, daf) contents are according to the rank of this coal; and, low total sulphur (1.8%, d). The coal is richer in huminite (86%) than liptinite (10%) and inertinite (4%). The maceral analysis indicates that lignite's peat precursor derived mainly from herbaceous plants and Botryococcus algae deposited in a topogenous mire (fen) under mesotrophic anoxic conditions. The water level remained above the paleomire's surface.

Can crystal morphology indicate different generations of dolomites? Evidence from magnesium isotopes

Among various geochemical and petrographic approaches, dolomite crystal morphology and dolostone fabric have been widely applied in the study of ancient dolostones. It is proposed that dolomite crystal morphologies and the rock fabric may reflect the formation temperature, and thus can be used to distinguish different generations of dolomite. However, this scenario has also been challenged by some researchers. In order to test whether the dolomite crystal morphology can be used to differentiate different generations of dolomite, in this study, we measured the Mg isotopic compositions (δ26Mg) of dolomite with different crystal morphologies. δ26Mg of dolomite is controlled by a variety of factors, including temperature, magnesium isotopic composition of dolomitization fluids, and the flow rate of dolomitization fluids. If dolomite with distinct crystal morphologies were derived from different dolomitization processes, it is highly plausible that they would have different δ26Mg. Five types of dolomite with distinct crystal morphologies and rock fabric were recognized from three sampling intervals (S1, S2, and S3) in the middle Ordovician Majiagou Formation in North China. Different types of dolomite in the same sampling interval have similar δ26Mg values, suggesting that these dolomites might have derived during the same dolomitization event. Our study indicates that the crystal morphology alone may not unambiguously differentiate the generations of dolomites. We propose the following reasons: (1) the dolomite crystal morphology might be controlled by various factors rather than the formation temperature alone, or (2) the dolomite crystal morphology might be modified in diagenesis, but δ26Mg remains unchanged.

Pottery Traditions in Northeastern Crete After the Fall of the Minoan Palatial Systems: A Petrographic Approach at Malia and Sissi

Pottery Traditions in Northeastern Crete After the Fall of the Minoan Palatial Systems: A Petrographic Approach at Malia and Sissi

The production cycle of lime‐based plasters in the Late Roman settlement of Scauri, on the island of Pantelleria, Italy

AbstractThis paper deals with the archaeometric study of lime‐based plasters found in the archaeological settlement of Scauri, located in the homonymous bay in the south‐western part of Pantelleria Island. Since 1999, archaeological surveys have led to the recovery of the huge remains of a Late Roman settlement dating back to the fourth–fifth century AD. It is well known that the island of Pantelleria is entirely composed of volcanic rocks. Accordingly, the production of quicklime required calcareous rocks to be imported. Also, the selection criteria of the sandy aggregate are relevant and of interest to this study, to evaluate the achieved technological level. Within this context, a mineralogical and petrographic characterisation of the plasters was carried out using thin‐section petrography, for the classification of the sand aggregate. Moreover, X‐ray diffraction and scanning electron microscopy were performed to investigate the composition of the binder. The analytical results allowed the identification of different recipes for the manufacture of the studied plasters, obtained by the use of different types of aggregate (volcanic rock fragments, pumice, basaltic scoriae, and ceramic fragments) and highlighted the degree of pozzolanic reaction of the binder. Finally, the provenance of the calcareous raw material was inferred using a petrographic approach.

Architecture and reservoir quality of low-permeable Eocene lacustrine turbidite sandstone from the Dongying Depression, East China

Abstract The architecture and quality of lacustrine turbidites that act as petroleum reservoirs are less well documented. Reservoir architecture and multiscale heterogeneity in turbidites represent serious challenges to production performance. Additionally, establishing a hierarchy profile to delineate heterogeneity is a challenging task in lacustrine turbidite deposits. Here, we report on the turbidites in the middle third member of the Eocene Shahejie Formation (Es3), which was deposited during extensive Middle to Late Eocene rifting in the Dongying Depression. Seismic records, wireline log responses, and core observations were integrated to describe the reservoir heterogeneity by delineating the architectural elements, sequence stratigraphic framework and lithofacies assemblage. A petrographic approach was adopted to constrain microscopic heterogeneity using an optical microscope, routine core analyses and X-ray diffraction (XRD) analyses. The Es3m member is interpreted as a sequence set composed of four composite sequences: CS1, CS2, CS3 and CS4. A total of forty-five sequences were identified within these four composite sequences. Sand bodies were mainly deposited as channels, levees, overbank splays, lobes and lobe fringes. The combination of fining-upward and coarsening-upward lithofacies patterns in the architectural elements produces highly complex composite flow units. Microscopic heterogeneity is produced by diagenetic alteration processes (i.e., feldspar dissolution, authigenic clay formation and quartz cementation). The widespread kaolinization of feldspar and mobilization of materials enhanced the quality of the reservoir by producing secondary enlarged pores. In contrast, the formation of pore-filling authigenic illite and illite/smectite clays reduced its permeability. Recovery rates are higher in the axial areas and smaller in the marginal areas of architectural elements. This study represents a significant insight into the reservoir architecture and heterogeneity of lacustrine turbidites, and the understanding of compartmentalization and distribution of high-quality sand reservoirs can be applied to improve primary and secondary production in these fields.

Mineral-petrographic study of greenstone cobbles from Quaternary alluvial deposits and Oligocene conglomerates of the Lemme valley (northwestern Italy): Comparison with analogous Neolithic polished stone implements and archaeometric implications

Rare HP meta-ophiolites of archeologic interest occur in the western Alps, both as small primary outcrops at high altitude located in the Monviso or Voltri massifs and as boulders/pebbles in the derived secondary conglomeratic deposits and/or alluvial beds downhill/downstream, originated after erosion of the former ones. Despite their scarceness, these rocks – in the archaeologic literature still grouped under the term “greenstones” – are of paramount importance for archaeologists, since they were used to produce polished stone tools rediscovered in prehistoric sites spread all over Europe. Tracing the sources of these raw materials is an important issue for reconstructing the migratory fluxes and trade routes of our ancestors. A certain number of “greenstone” geologic samples were retrieved from the alluvial beds of the Lemme valley streams (southeastern Piemonte, Italy) and in the Oligocene conglomerate units of the Tertiary Piemonte Basin, presently exposed in the same valley. Representative samples were analyzed with a classic mineralogical and petrographic approach, which includes XRPD, polarizing microscope and SEM-EDS. These rocks compositions and microstructures were then compared with those of analogous implements found in archaeological sites located nearby and already described in the literature, searching for analogous traits suggesting a common origin. The obtained outcomes show that these secondary deposits of the Lemme valley – originated from the dismantlement of upstream primary outcrops in the Voltri massif (or from a close, analogous palaeo-unit, nowadays completely eroded) – might have represented, during the early-to-middle Neolithic, one of the preferential supply sources of raw “greenstones” for the archaeologic sites of Brignano Frascata, Momperone, Villaromagnano and Rivanazzano.

The effects of metamorphism on iron mineralogy and the iron speciation redox proxy

As the most abundant transition metal in the Earth’s crust, iron is a key player in the planetary redox budget. Observations of iron minerals in the sedimentary record have been used to describe atmospheric and aqueous redox environments over the evolution of our planet; the most common method applied is iron speciation, a geochemical sequential extraction method in which proportions of different iron minerals are compared to calibrations from modern sediments to determine water-column redox state. Less is known about how this proxy records information through post-depositional processes, including diagenesis and metamorphism. To get insight into this, we examined how the iron mineral groups/pools (silicates, oxides, sulfides, etc.) and paleoredox proxy interpretations can be affected by known metamorphic processes. Well-known metamorphic reactions occurring in sub-chlorite to kyanite rocks are able to move iron between different iron pools along a range of proxy vectors, potentially affecting paleoredox results. To quantify the effect strength of these reactions, we examined mineralogical and geochemical data from two classic localities where Silurian-Devonian shales, sandstones, and carbonates deposited in a marine sedimentary basin with oxygenated seawater (based on global and local biological constraints) have been regionally metamorphosed from lower-greenschist facies to granulite facies: Waits River and Gile Mountain Formations, Vermont, USA and the Waterville and Sangerville-Vassalboro Formations, Maine, USA. Plotting iron speciation ratios determined for samples from these localities revealed apparent paleoredox conditions of the depositional water column spanning the entire range from oxic to ferruginous (anoxic) to euxinic (anoxic and sulfidic). Pyrrhotite formation in samples highlighted problems within the proxy as iron pool assignment required assumptions about metamorphic reactions and pyrrhotite’s identification depended on the extraction techniques utilized. The presence of diagenetic iron carbonates in many samples severely affected the proxy even at low grade, engendering an interpretation of ferruginous conditions in all lithologies, but particularly in carbonate-bearing rocks. Increasing metamorphic grades transformed iron in carbonates into iron in silicate minerals, which when combined with a slight increase in the amount of pyrrhotite, drove the proxy toward more oxic and more euxinic conditions. Broad-classes of metamorphic reactions (e.g. decarbonation, silicate formation) occurred at distinct temperatures-pressures in carbonates versus siliciclastics, and could be either abrupt between metamorphic facies or more gradual in nature. Notably, these analyses highlighted the importance of trace iron in phases like calcite, which otherwise might not be included in iron-focused research i.e. ore-system petrogenesis, metamorphic evolution, or normative calculations of mineral abundance. The observations show that iron is mobile and reactive during diagenesis and metamorphism, and these post-depositional processes can readily overprint primary redox information held by iron speciation. However, in principle, additional mineralogical and petrographic approaches can be combined with iron speciation data to help untangle many of these post-depositional processes and arrive at more accurate estimates of paleoenvironmental redox conditions and processes, even for metamorphosed samples.

Oxidatively and thermally altered high-volatile bituminous coals in high-temperature coal fire zone No. 8 of the Wuda Coalfield (North China)

Coal fires have received increasing attention due to their environmental, economic, and social impacts. Their significant influence on coal properties is widely documented by geophysical and geochemical methods.The present paper demonstrates, by means of coal petrological methods, significant changes of microstructure, optical appearance, and optical properties of medium-rank (bituminous) coals affected by an underground coal fire. The studied changes are suggested to result from distinct oxidative and thermal alterations induced by a high-temperature regime (temperatures over 800°C) encountered in the coal fire zone No. 8, Wuda Coalfield. The investigated coal seam No. 9 represents a high volatile A bituminous coal and is dominated by vitrinite, followed by inertinite with minor amounts of liptinite. The microstructure of the coal-fire affected coals facilitate a broad spectrum of characteristic features. The microscopic analyses revealed development of (1) non-tectonic fissures and non-tectonic fractures, (2) distinct micropores, (3) dark oxidations rims, and (4) bright spots interpreted as incipient mesophases. Optical properties were characterised for megasporinite and vitrinite. In the examined megasporinite a noticeable anisotropy and distinct granular appearance was observed. In the investigated coals both a dominant increase as well as a minor decrease in both random and maximum vitrinite reflectances were documented for (1) coal grains and (2) dark-rimmed vitrinite at non-tectonic fissures and non-tectonic fractures. In addition, also a characteristic bimodal vitrinite population was measured. The increase in bireflectance was clearly documented for two sub-zones within the coal fire zone No. 8. The applied Kilby's cross-plots suggested a large overlapping of the data sets of R'max and R'min, indicating marked changes in vitrinite structure. The applied coal petrological approach revealed distinct changes to the coal's microstructure, appearance, as well as to optical properties induced by the underground coal fire. The presented coal petrographic approach may help determine the extent of coal fires in coal mines and the direction of propagation of coal fire front.

Provenance and alteration of pyroclastic rocks from the Romanesque Churches of Logudoro (north Sardinia, Italy) using a petrographic and geochemical statistical approach

The pyroclastic rocks, belonging to the calcalkaline volcanic activity occurred in Sardinia between 32 and 11 Ma ago, were widely used as construction material in several Romanesque Churches of the easternmost Logudoro, as well as in the Sardinia territory. In this work was taken as a case study the Church of Nostra Signora di Otti (12th cent.). There are no historical or archaeological evidences of the ancient quarries. Based on the geochemical, petrographic and volcanological characters of several samples from an extensive field area (approximately 150 kmq), a geographical zoning of the Oligo-Miocenic volcanics has been recognised. Internally to the Oschiri sector, according to TiO2 vs Differentiation Index diagram, there are three different sub-zones with pyroclastics: less fractionated (D.I. ~70 ÷ 78); intermediate fractionated (D.I. ~76 ÷ 79); more fractionated (D.I. ~77 ÷ 82). To identify the origin of the ignimbrites of the Church, two statistical methods have been used: stepwise linear discriminant and canonical analysis. Moreover, to define the geochemical transformation processes induced by the alteration, by XRD analysis and XRF, SEM–EDS data, a comparative study of concentrations of major and trace elements measured between the surface portion and the innermost of the stone has been made.

A diachronic study of pre-Hispanic vessels from the middle basin of Paraná River (South America) using a petrographic approach

This paper presents a petrographic study of pre-Hispanic vessels from archaeological sites located in the middle basin of the Paraná River, a geographical area where this analytical technique still has very limited application in ceramic studies. Within this framework, a first approach to the chronological variability of pottery through the analysis of 58 ceramic thin sections is carried out. The samples correspond to vessels made by complex hunter-gatherer groups between 625±46 and 1.380±100 14C years BP. The pottery was recovered from three archaeological sites: Arroyo Arenal 1, Arroyo Largo I, and La Palmera II (Entre Rios Province, northeastern Argentina), which are linked to an archaeological unit locally called Goya-Malabrigo. The results show, among other chronological variations, an increasing trend in the use of grog temper over time. These data allow the expansion of knowledge about the ceramic technology of human groups who occupied the area of the Paraná River during the Late Holocene.

A thermoanalytical, X-ray diffraction and petrographic approach to the forensic assessment of fire affected concrete in the United Arab Emirates

For most fires, forensic investigation takes place well after building materials have cooled and knowledge of the structural damage due to heat exposure can reveal the temperature reached during an incident. Recently, there have been significant changes in the types and hence characteristics of cementitious materials used in the United Arab Emirates. Few studies focus on the application of thermo-analytical, X-ray diffraction and petrographic techniques on newly developed structures and this work aims to address this deficiency by utilising a series of parametric laboratory-based tests to assess the effects of heat on hardened concrete. Specimens were made with a design mix typically used for low-rise residential homes and storage facilities. The key constituents were: Portland cement (PC), crushed gabbro stone and dune sand with water/cement ratios of 0.4–0.5. Portland cement substitutes included ground granulated blast-furnace slag (GGBS), and silica fume (SF) at replacement percentages of up to 50% and 4%, respectively. The concrete cubes of 100-mm size were produced and standard cured to 28 days and then exposed to heat inside an electric furnace with pre-determined temperature regimes of 150°C, 300°C, 600°C and 900°C. Petrographic examination was utilised to compare the discolouration of the cooled concrete. Data derived from thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) are reported in order to assess the usefulness of these techniques in fire scene investigation to differentiate between these temperature regimes. The results from the TGA indicate that the majority of the percentage weight loss for all the mixtures occurred in the range 650–700°C, which corresponds to the decarbonation of calcium carbonate, mainly from the aggregates. The endothermic DSC peak at 70–120°C relates to the loss of evaporable water. Since both of these reactions are irreversible, this information can help fire investigators estimate the temperature history of concrete after exposure to fire. On the other hand, the portlandite in the cement matrix dehydroxylates at 450–550°C but then reforms as the concrete cools. The onset temperature for the dehydroxylation of the reformed mineral is always lower than in virgin samples and its enthalpy furthermore depends strongly on the thermal history of the portlandite. Thus, this feature can be used to establish the temperature to which the material was exposed to during a fire incident.

Provenance, Tectonic Setting and Climatic Conditions during Lower Permian Barakar Sedimentation in the Mand Gondwana Basin, India - A Petrographic Approach

Provenance, Tectonic Setting and Climatic Conditions during Lower Permian Barakar Sedimentation in the Mand Gondwana Basin, India - A Petrographic Approach

Archaeometric characterization of Roman volcanic millstones from Messina territory (Sicily, Italy)

In this paper we present the results of petrochemical study of Roman cereal millstones and relative elements made of volcanic rocks, found in various archaeological sites of Messina. Fifteen samples dating from the III century AD and one from the second, also dating from the II–III centuries AD, were characterized through archaeological, petrographic, mineralogical and geochemical approach. On the petrochemical point of view the raw materials of the studied millstones are mainlyvolcanic rock characterized by Na-alkaline affinity with intraplate geochemical signature. Only two samples belonging to the K-alkaline seires showing volcanic arc signature. Comparison with literature data of similar volcanic rocks, allowed to constrain the volcanic site of provenance. Most of the intraplate samples are mugearites and benmoreites from Mt. Etna, the other are peralkaline-trachyte from Pantelleria Island and alkaline basalt from Linosa Island. The two arc-type samples derived instead from Islands of the Aeolian Archipelago. The petrochemical study of millstones improve the archaeological research, confirming the ancient communication routes and trade networks in the Mediterranean Region and highlighted the use of volcanic rocks from Sicilian area, during the Roman period, as very important sources of raw materials for millstones.

The adze-heads from Plemięta, Grudziądz district (Poland): Alpine jades, Armorican products and very long-distance exchanges

Discovered in the 19th century, the hoard from Plemieta (Chelmno county, Poland) consisted of three polished adze-heads, of which two are in the Museum in Grudziądz. Until now, this hoard had been assumed to be linked to Danubian farming communities. A petrographic approach coupled with an in-depth, Europe-wide typological study allows us to rethink this cultural attribution. In fact, the Plemieta adze-heads had very probably been made in the Armorican massif (France), produced by specialists directly influenced by the standards of the earliest adze-heads of Alpine jades from Mont Viso in the Italian Alps. This proposition, which is supported by other examples of adze- and axeheads that had probably been imported into southern Scandinavia from France, re-invigorates the hypothesis that there had been western Europeaninfluences on communities of the Eastern TRB Group, pertaining to the circulation of ‘object-signs’ andideas over distances exceeding 1500 km as the crow flies. Key words: Plemieta, Chelmno county, Alpine jades, Begude type adze-head, the Funnel Beaker culture.