Carlo Bertok

Tectono-sedimentary evolution of the Pliocene to Lower Pleistocene succession of the Apricena-Lesina-Poggio Imperiale quarrying district (western Gargano, southern Italy)

The post-Miocene marine succession of the «Apricena horst» is described with the purpose to verify the chronostratigraphic constraints for the type-locality of the Pirro Nord Faunal Unit. The stratigraphic succession has been subdivided in four units bounded by ubiquitous unconformities with evidence of subaerial exposure. The two basal units (dated late Zanclean to at most early Piacenzian) are formally grouped in the Lago di Varano Fm. that on the whole consists of sediments ranging from lagoonal to circalittoral environments. Within the lowermost unit, a megabreccia is interpreted as the product of a tsunami event. The third unit, Gelasian in age, is informally cited as Calcari a Briozoi Fm. The last unit, the Lower Pleistocene Serracapriola Fm., consists of siliciclastic deltaic sediments and represents the closure of the marine cycle. Conspicuous lateral facies and thickness changes, and the frequency of unconformities are the consequence of an intense synsedimentary tectonic activity developed in the frame of the southern Apulia foredeep closure. In the study area, such activity is documented by two E-W trending normal faults which, during Zanclean and at least the earliest Gelasian, controlled the Pliocene horst-graben system of the Apricena-Poggio Imperiale area.

New data on post-Eocene tectonic evolution of the External Ligurian Briançonnais (Western Ligurian Alps)

A new structural setting for the central part of the External Ligurian Brianconnais (CELB) is proposed. CELB is divided into km-scale tectonic units that still preserve pre-Alpine geological features at several stratigraphic levels. Macro-, meso- and microscale primary features, such as paleoescarpments, unconformities and depositional or diagenetic fabrics are thus well preserved and can be still mapped and studied in detail at many stratigraphic levels. Significant transposition of bedding is recorded only in Upper Cretaceous and Eocene marly limestones and shales and in major km-long shear zones, where intense development of closely spaced tectonic foliations occurred. Several features indicate that the CELB tectonic evolution took place at shallow crustal levels: 1) strong localization of deformation along the weakest stratigraphic levels; 2) absence of diffuse recrystallization of rocks; 3) minor occurrence or absence of transposition of bedding; 4) kinematic evolution of fold axial plane foliations into frictional slip cleavages. A gradual decrease in the intensity of deformation from the Internal Ligurian Brianconnais to CELB and Dauphinois Domain is observed, although the boundaries of these three domains correspond, in the study area, to several Km-long, transpressive shear zones whose kinematic role in the evolution of the southern termination of the Western Alps should be carefully considered.

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.

Stone materials used for monumental buildings in the historical centre of Turin (NW Italy): architectonical survey and petrographic characterization of Via Roma

Abstract One of the peculiarities of Turin (NW Italy) lies on the presence of monumental arcades which mainly consist of stone material. These arcades, characterized by more than 12 km of interconnected paths, represent one of the widest city promenades of Europe and are an architectural, aesthetic and socio-economic example unique in the world. This paper, analysing the urban axis of Via Roma (Rome Street), aims to study the material used in arcade construction. The main stones occurring in Via Roma have been identified and described from a petrographic and mineralogical point of view in order to find out the corresponding geological units and original quarry sites. The minero-petrographic study is accompanied by an architectural survey that was performed applying different methods, as well as the geometric mapping and the perspective rectification of span-types, of block terminations and of other architectonical elements, in plan and in elevation, of the arcades. This allows us to emphasize the merging of cultural and scientific interest for the stone materials used in the historical architecture of a town closely interconnected to the surrounding Western Alps orogenic chain.

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.

Virtual Tours Through Earth’s History and Palaeoclimate: Examples from the Piemonte (Northwestern Italy) Geoheritage (PROGEO-Piemonte Project)

A project developing virtual tours on the geoheritage of Piemonte aims to disseminate geological knowledge to the general public. Two of the most crucial geological themes, geological time and climatic and environmental change, are addressed. People will increase their awareness of Earth’s geodiversity and of the potential of Earth Sciences to improve our everyday lives. The tours will be developed with special attention to educational purposes and in lay language, and will also contribute to preserving vulnerable geoheritage.

The Cretaceous-Eocene succession of the Rocca Busambra (Western Sicily, Italy): a patchy record on a dissected palaeostructural high

A detailed study has been carried out, integrating biostratigraphy, sedimentology and physical stratigraphy, on Albian-Eocene pelagic sediments (Hybla and Amerillo formations) of the western sector of Rocca Busambra (Trapanese Domain, Western Sicily). They mainly consist of pink to greyish mudstones to packstones with abundant planktonic foraminifera and display the same lithofacies as the well known Scaglia formations, typical of the coeval Southern Alps and Apennine successions. These Scaglia-type sediments commonly occur as isolated sedimentary bodies with a marked lenticular geometry and highly variable thicknesses (from few decimetres to tens of metres) and ages (from late Albian to middle Eocene). They uncomformably rest, with onlap relationships, on very steep or low angle surfaces incised within the underlying formations that can be the Middle Jurassic-Lowermost Cretaceous Buccheri and Lattimusa formations or the Lower Jurassic Inici Formation. Steep surfaces, in agreement with previous authors, are considered as palaeofault planes, whereas gently sloping surfaces find a better explanation as slide scars. The occurrence of monomict and polymict breccias and megabreccias, interlayered within the succession, document debris flow and rock fall processes and support the scenario of a highly irregular sea floor topography. Albian-Eocene sediments are also found as infillings of neptunian dykes and sills present within the Buccheri or the Inici formations.Biostratigraphic data evidence the existence of two very long gaps, respectively corresponding to the Berriasian-middle Albian and the late Campanian-late Paleocene intervals, and the time correspondence of sediment preservation as neptunian dyke fills and sea floor accumulation. All these sedimentologic, geometric and biostratigraphic data show that, starting from the late Albian and up to the Eocene, the Rocca Busambra stood as a margin of a submarine plateau dissected by faults in two main distinct episodes of Albian and Paleocene-Eocene age. In such a morphostructural setting, prolonged time intervals characterized by sediment bypass alternated with tectonic events, during which the opening of fractures and fault-related depressions and the generation of slide scars provided suitable settings for trapping and preserving sediments.

Geology of the Colle di Tenda – Monte Marguareis area (Ligurian Alps, NW Italy)

ABSTRACT The 1:25,000 geological map of the Colle di Tenda – Monte Marguareis area covers an area of about 130 km2 in the Italian Ligurian Alps, between the Vermenagna and Tanaro valleys. It is a detailed geological map of a sector of the Ligurian Alps of renewed scientific interest, and represents the eastern continuation of a recently published geological map of the Entracque-Colle di Tenda area. In addition to the increased detail and scale, the more relevant new contents of this map are represented by: a map of all the tectonic elements making up the Limone-Viozene Zone and the Refrey Unit, which represent the south-eastern portion of a major regional transfer zone developed at the southern termination of the Western Alps arc; the representation of km-scale Cretaceous palaeoescarpments previously overlooked or interpreted as Alpine faults; a new interpretation of some dark shales with interbedded sandstones, which were previously mapped as Helminthoides Flysch tectonic remnants, as belonging to the Annot Sandstone unit, the uppermost term of the Alpine Foreland Basin succession; and a map legend designed following the same criteria of the 1:250,000 Map of the Piemonte Region.

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.