Search results for "petrography"
showing 10 items of 138 documents
Carbonate stromatolites from a Messinian hypersaline setting in the Caltanissetta Basin, Sicily: petrographic evidence of microbial activity and rela…
2010
Lower Messinian stromatolites of the Calcare di Base Formation at Sutera in Sicily record periods of low sea-level, strong evaporation and elevated salinity, thought to be associated with the onset of the Messinian Salinity Crisis. Overlying aragonitic limestones were precipitated in normal to slightly evaporative conditions, occasionally influenced by an influx of meteoric water. Evidence of bacterial involvement in carbonate formation is recorded in three dolomite-rich stromatolite beds in the lower portion of the section that contain low domes with irregular crinkly millimetre-scale lamination and small fenestrae. The dominant microfabrics are: (i) peloidal and clotted dolomicrite with c…
Microbially-induced Fe and Mn oxides in condensed pelagic sediments (Middle -Upper Jurassic, Western Sicily)
2011
Abstract This article presents a petrographic comparison of the Rosso Ammonitico facies of Western Sicily and the original Rosso Ammonitico Veronese of Northern Italy based on a total of 27 sections. The Rosso Ammonitico has been the subject of numerous controversies that range from bathyal to shallow-water platform sedimentation. Therefore it seemed interesting to verify if the term Rosso Ammonitico has the same geologic connotation from region to region. The Middle-Upper Jurassic Rosso Ammonitico of Western Sicily is a condensed succession formed during a period of extensional synsedimentary tectonics related to the spreading of the Ionian Ocean. Slope-to-basin or pelagic carbonate deposi…
Coarse-grained cryogenic aragonite as end-member of mineral formation in dolomite caves
2018
Abstract Cryogenic carbonate particles (single crystals and aggregates) have recently been recognized as important witnesses of permafrost dynamics, as they can be used to estimate the thickness and timing of development of permafrost. In this study, the petrography and geochemistry of coarse-grained cryogenic aragonite (CGCAr) identified in Zoolithen Cave in NE Bavaria, Germany, are described in detail for the first time. We provide a sequence of carbonate precipitation during freezing, where CGCAr mark the final crystallization phase in freezing water on ice. Our results support the notion that host rock composition, solution chemistry, and cave ventilation play an important role for arag…
Characterization and origin of permeability-porosity heterogeneity in shallow-marine carbonates: from core scale to 3D reservoir dimension (Middle Ju…
2014
21 pages; International audience; Nuclear magnetic resonance (NMR), stable isotope geochemistry of micro-sampled cores, NMR well-logs and 3D modeling are used to investigate the carbonate permeability-porosity heterogeneity along 230 m-thick limestones of the Paris Basin. Despite the global low porosity and permeability of the limestones, two aquifers units with porosity greater than 15% were identified. These two aquifers are very different in terms of pore through radii and NMR signal. The first one (A1: Aquifer 1) is a 7 m-thick mudstone unit, dominated by extended microporosity with pore throat radii of 0.25 μm to 0.3 μm. The second one (A2: Aquifer 2) is a 15 m-thick oolitic grainstone…
Discrimination and provenances of Phoenician red slip ware using both the solid state electrochemistry and petrographic analyses
2020
[EN] Solid state electrochemistry based on the voltammetry of immobilized microparticles (VIMP) methodology is applied to a series of 80 Phoenician Red Slip samples from the archaeological sites of Motya (Sicily, Italy), Mogador (Morocco), Ramat-Rahel (Israel), Sulky (Sardinia, Italy), Tas Silg (Malta), Pantelleria (Italy), and Cadiz (Spain), dated from the 8(th) to the 6(th) century BC. Upon attachment of sub-microsamples to graphite electrodes in contact with aqueous H2SO4 electrolyte, voltammetric features due to the reduction of Fe(III) minerals and the oxidation of Fe(II) ones, complemented with electrocatalytic effects on oxygen reduction and oxygen evolution reactions, provide charac…
The beginning of western greek amphorae production in western Sicily: archaeometric and archaeological studies on 6th–5th centuries BCE amphorae manu…
2020
About 560 western Greek amphorae (6th–5th centuries BCE) re-used in enchytrismos burials were unearthed in the necropolis of the Dorian-Chalcidian colony of Himera in northwestern Sicily. Among the most striking issues is the determination of their geographical provenance. For this purpose, ceramic samples chipped from freshly broken surfaces of all the amphorae were first subdivided into macrofabrics by the use of a hand lens. Thereon, the samples were studied in accordance with standardized methods by the use of reflected light microscopy. Due to the special focus of our project on the characterization of Sicilian productions, a selection of amphorae which showed visible, macroscopic affi…
Archaeometry of Sicilian glazed pottery
2004
Petrographic and chemical analyses of the “ceramic body” of 114 majolica artefacts manufactured in Sicily over a wide time range (16th–-19th century) are presented. All the analysed samples, which belong to museums and private collections, were previously attributed to Sicilian workshops based on stylistic features evaluated by expert historians of art. Unambiguous identification of the production sites of majolica handicrafts in Sicily remains, however, open to question when this relies only on purely stylistic considerations. To this end compositional and/or textural markers have been searched for in the “ceramic body” of the majolica artefacts in order to differentiate between the centre…
Characterisation of clayey raw materials for ceramic manufacture in ancient Sicily
2011
Abstract It is well known that mineralogical, petrographic and chemical analyses can successfully support provenance studies of archaeological ceramics. The characterisation of a ceramic paste, the assessment of its technology of production and its provenance assignment related to a specific production centre or to a geographical and/or compositional space, are all tasks that can be performed even more accurately if the clayey raw materials used in pottery production are also studied. For that reason the identification of the clay deposits exploited in a given ceramic workshop often plays a key role in the archaeometric reconstruction of the production cycle where geology, mineralogy, petro…
A multi-technique, micrometer- to atomic-scale description of a synthetic analogue of chukanovite, Fe-2(CO3)(OH)(2)
2014
International audience; A synthetic analogue of chukanovite Fe-2(CO3)(OH)(2) is formed during experimental work on iron-clay interactions simulating the cooling of containers in radioactive waste repositories. Despite its small size and the mixture with other minerals it is undoubtedly identified by X-Ray Diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy and Transmission Electron Microscopy. For the first time, the structural characterisation of a synthetic chukanovite is carried out thanks to the combination of Automated Diffraction Tomography and Precession Electron Diffraction. Refinement results and comparison with literature data show that the structure…
Physicochemical characteristics of drip waters: Influence on mineralogy and crystal morphology of recent cave carbonate precipitates
2014
Speleothems are one of the most intensively explored continental archives for palaeoclimate variability. The parameters, however, that control speleothem petrography and its changes with time and space, specifically calcite crystal morphology and carbonate mineralogy, are still poorly understood. In order to shed light on processes and their products, precipitation experiments of recent carbonate crystals on watch glasses and glass plates were performed in seven selected caves. Drip water sites were analysed for their fluid Mg/Ca molar ratio, pH, degree of saturation for calcite and aragonite and drip rates. Corresponding precipitates were analysed with respect to their mineralogy, calcite …