Early Hauterivian mixed Fe-oxide–phosphate ooids from the Lower Cretaceous condensed succession of the Alpine Provençal Domain are ellipsoidal, 200–2000 µm in diameter, and the main component of a sedimentary body, 0–100 cm thick, that can be traced laterally for tens of kilometers. Cathodoluminescence, EDS microprobe, backscattered electron imaging, epifluorescence, XRD, and micro Raman spectroscopy reveal that ooid cortices consist of variable proportions of Fe-oxide-rich and Ca-phosphate-rich layers. SEM observations show that phosphate-rich layers are composed of a dense matrix of micrometer-size, rod-shaped, commonly curved phosphate grains, whose size and shape strongly suggest a microbial origin. Conversely, Fe-oxide-rich ooid cortical layers consist of aggregates of micrometer-size, plate-like crystals of hematite that point to an inorganic precipitation. We suggest that the ooidal condensed interval records a long sedimentary history in an open shelf environment subject to a background accumulation of organic-rich, fine-grained sediments. It was periodically interrupted by high-energy, storm-related events that resulted in winnowing, reworking, and oxygenation that favored precipitation of Fe-oxides around nuclei of biogenic origin. Such precipitation was not uniform on the outer surface of ooids and influenced their ellipsoidal shape. After the return to background conditions, Fe-ooids were buried and driven from an oxic to a post-oxic subbottom geochemical environment where rod-shaped Fe-reducing bacteria colonized Fe-ooid outer surfaces. Decomposition of organic matter and release of P bound on Fe-oxides increased pore-water concentration of phosphate, which precipitated at the outer surfaces of the ooids, thus preserving the microbial community. The bimineralic composition of these ooids discloses a complex and prolonged history of cyclic alternations of oxic and post-oxic geochemical conditions, which are in turn related to alternating sediment accumulation and winnowing phases with exposure at the seafloor.

The 'Ornamental Stones of Piemonte Region' geo-lithological map at 1:250,000 scale aims at reviewing the ornamental stone heritage of Piemonte at the regional scale. The map derives from a thorough revision of the available literature, integrated with some unpublished original data. The map shows the location of the main quarries of ornamental stones of the region, selected on the basis of their historical, cultural and architectonic relevance. A geo-lithological basemap was produced, deriving it from a basic Geological Map of Piemonte, available at the same scale. The large varieties of lithotypes of Piemonte have been resumed, in the new map, into 21 classes, which all the ornamental stones have been assigned to. The Main Map is enriched by some significant examples of using the ornamental stones in historical buildings, and it is supported by a supplementary data base containing essential information about the quarry sites and the quarried material.

The present article illustrates a straightforward case of hydrothermal dolomitization, affecting Jurassic platform limestones of the Provençal and Subbriançonnais Domains (Maritime Alps, North-Western Italy). Dolomitized bodies are randomly distributed within the host limestone, and are commonly associated with dolomite vein networks and tabular bodies of dolomite-cemented breccias discordant with respect to bedding. Main dolomite types are a finely to medium-crystalline replacive dolomite and a coarsely-crystalline saddle dolomite occurring both as replacive and as cement. Stratigraphic constraints indicate that dolomitization occurred during the Cretaceous, in a shallow burial context, and was due to the circulation of hot fluids (temperature about 200 °C, as indicated by fluid inclusion microthermometry) through faults and related fracture networks. Hydrothermal dolomitization therefore indirectly documents a Cretaceous fault activity in the Maritime Alps segment of the European Tethyan passive margin.