Luca Barale

Geology of Piemonte region (NW Italy, Alps–Apennines interference zone)

ABSTRACT The geological map of Piemonte Region (Italy) is a graphic representation of the geology of the region, grounded on a large geodatabase, that can be also browsed as an interactive scalable map (GeoPiemonte Map) using a WebGIS application. The Map, produced at 1:250,000 scale, is the first original release of the ‘GeoPiemonte Map’ project. The geological data represented on the map derive from a thorough revision of available geological maps and literature, integrated with unpublished original data. The revision and harmonisation of existing and new data have been based on explicit criteria used for the classification of geologic units and their representation on the Map. These criteria firstly aimed at providing a lithostratigraphic, hierarchic subdivision of Piemonte geologic units and describing them using shared concepts and vocabularies, consistent with IUGS Descriptive Standards for the Geosciences.

Geological setting of the southern termination of Western Alps

A revision of the stratigraphic and tectonic setting of the southern termination of the Western Alps, at the junction of the Maritime Alps with the westernmost Ligurian Alps, is proposed. In response to the Alpine kinematic evolution, a number of tectonic units formed on the deformed palaeo-European continental margin and were arranged in a NW–SE striking anastomosed pattern along the north-eastern boundary of the Argentera Massif. Because these tectonic units often cut across the palaeogeographic subdivision of the Alpine literature and show only partial affinity with their distinctive stratigraphic features, new attributions are proposed. The Subbriançonnais domain is here intended as a “deformation zone”, and its tectonic units have been attributed to Dauphinois and Provençal domains; furthermore, the Eocene Alpine Foreland Basin succession has been interpreted, based on the affinity of its lithologic characters and age, as a single feature resting above all the successions of the different Mesozoic domains. The Cretaceous tectono-sedimentary evolution of the studied domains was characterized by intense tectonic controls on sedimentation inducing lateral variations of stratigraphic features and major hydrothermal phenomena. Since the early Oligocene, transpressional tectonics induced a NE–SW shortening, together with significant left-lateral movements followed by (late Oligocene–middle Miocene) right-lateral movements along E–W to SE–NW striking shear zones. This induced the juxtaposition and/or stacking of Briançonnais, Dauphinois and Ligurian tectonic units characterized by different metamorphic histories, from anchizonal to lower greenschist facies. This evolution resulted in the arrangement of the tectonostratigraphic units in a wide “transfer zone” accommodating the Oligocene WNW-ward movement of portions of the palaeo-European margin placed at the south-western termination of Western Alps and the Miocene dextral shearing along SE striking faults that bound the Argentera Massif on its NE side.

Geology of the Entracque–Colle di Tenda area (Maritime Alps, NW Italy)

The 1:25,000 geological map of the Entracque–Colle di Tenda area covers an area of about 130 km2 in the Italian Maritime Alps, between the Gesso and Vermenagna valleys. The map area is of great relevance since the Alpine units of this region sampled a geological nodal point in the Mesozoic, at the transition between two different sedimentation domains of the Alpine Tethys European palaeomargin (the Dauphinois basin to the NW and the Provençal platform to the SE). During the Cenozoic, this palaeogeographic hinge was progressively incorporated along multiple shear zone systems developed at the southern termination of the Western Alps arc.

The Classification Scheme of the Piemonte Geological Map and the OntoGeonous initiative

The OntoGeonous initiative has the goal of modeling a number of interconnected computational ontologies of geological concepts in order to exploit (i) the expressive power of ontological systems to merge several geological concepts (ii) the reasoning capabilities of the ontological systems to check the consistency of the currently existing knowledge stored in the Data Base of the Piemonte Geological Map at 1:250.000 scale and to infer novel knowledge.The prospect application of this initiative is the intelligent data collection and compilation of geological data base and the provision of sound semantic foundations for a modern cartographic project that provides a basis for a synthesis of geological data at the regional scale.

A Trip Through Deep Time in the Rock Succession of the Marguareis Area (Ligurian Alps, South Western Piemonte)

The multidisciplinary research project “PROGEO-Piemonte” aims to achieve a new conceptual and operational discipline in the management of the geological heritage of the Piemonte Region. To this end, an itinerary is proposed to illustrate the most significant steps in the geological evolution through time of the stratigraphic successions exposed in the Marguareis area (south western Piemonte). Volcanic and sedimentary rocks crop out here representing continental alluvial plain, carbonate tidal flat, and deep sea basin environments, spanning 200 million years from Permian to Eocene times. Together, they record the main stages of the geological evolution of the European margin related to the opening and closure of the Alpine Tethys ocean and consequent genesis of the Alpine chain. The proposed itinerary reveals stratigraphic successions with prolonged discontinuities and ancient faults documented by the geometrical relationships between rock bodies.

The Geodatabase of the Piemonte Geological Map: conceptual design for knowledge encoding

The Geodatabase of the Piemonte Geological Map was designed in a way suitable for linking the geological knowledge of the geological domain at hand to more general levels of knowledge represented in some Earth science ontologies and namely in a dedicated ontology (OntoGeonous). The paper describes how the two different knowledge levels are assimilated in the GeoPiemonte informative system, providing relations between the contents of the geodatabase and theencoded concepts of the reference ontologies.

The Meso–Cenozoic stratigraphic succession of the Col de Braus area (Maritime Alps, SE France)

ABSTRACT The 1:10,000 geological map here presented extends over about 32 km2 around the Col de Braus pass in the Maritime Alps (SE France). This area has attracted the attention of geologists since the late eighteenth century due to superb exposures of the Jurassic–Cretaceous Provençal succession, and has become a classic geological locality continuously studied until the present day. In this area, Early Cretaceous synsedimentary tectonics is evidenced by important lateral thickness and facies variations. This sector is presently placed at the western termination of a large structural domain extending from the westernmost Ligurian Alps into the French–Italian Maritime Alps, thus representing a key-area for understanding the structural setting of this part of the Western Alps.

STRATIGRAPHY, SEDIMENTOLOGY AND SYNDEPOSITIONAL TECTONICS OF THE JURASSIC-CRETACEOUS SUCCESSION AT THE TRANSITION BETWEEN PROVENÇAL AND DAUPHINOIS DOMAINS (MARITIME ALPS, NW ITALY)

The Provencal and Dauphinois Mesozoic successions cropping out at the southeastern margin of the Argentera Massif (Maritime Alps, NW Italy) were deposited at the transition between the Provencal platform and the Dauphinois basin, marked in the study area by a partly preserved Mesozoic palaeoescarpment. These successions show important lateral variations occurring over relatively short distances, probably related to syndepositional tectonics. Different stratigraphic intervals of the pelagic-hemipelagic Dauphinois succession contain resedimented deposits, made up of both intra- and extrabasinal material, which provide a twofold evidence of syndepositional tectonics indicating both tectonically-triggered gravitational processes and a tectonically-driven evolution of the source areas. Two stages of syndepositional tectonics have been recognized: the first in the earliest Cretaceous, which is related to the deposition of carbonate breccias in the Dauphinois succession and to hydrothermal dolomitization of the Middle Triassic-Jurassic Provencal carbonates, and the second in the Late Cretaceous, which triggered the deposition of different detrital lithozones in the Upper Cretaceous Puriac Limestone. The cited evidence indicates that syndepositional tectonics continued to influence the evolution of the Alpine Tethys European passive margin long after the Late Triassic-Early Jurassic syn-rift stage, which caused the differentiation between the Dauphinois basin and the Provencal platform.