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The Jurassic ophiolites in the Northern Apennines and the Western Alps represent fossil mid-ocean ridge (MOR) oceanic lithosphere that formed in the Mesozoic Ligurian-Piedmont Ocean Basin (LPOB). Their sedimentary covers include chaotic rock units containing ophiolite-derived material. The processes of formation and the lithostratigraphic position of these chaotic units in the Western Alps remain a matter of debate, unlike their counterparts in the Northern Apennines. This is because of pervasive tectonic deformation and high-pressure metamorphism that affected their internal structure during collisional tectonics. A comparative analysis of these chaotic units in both mountain belts reveals the nature of processes involved in their formation. Chaotic deposits of gravitational origin occur both below and above the extrusive sequences in the ophiolites. They represent synextensional, hyperconcentrated deposits associated with the seafloor-spreading evolution of the LPOB lithosphere during Middle and Late Jurassic times. Mass transport deposits (MTDs) occur as intercalations within turbiditic sequences above the ophiolites. They represent syncontractional submarine slides that occurred on frontal accretionary prism slopes during the Late Cretaceous-Paleocene closure of the LPOB. The results of our comparative analysis imply that (1) the structure-stratigraphy of the chaotic deposits and MTDs of the Northern Apennines can be used as a proxy to better identify their metamorphosed and highly deformed counterparts in the Western Alps, (2) sedi-mentological processes associated with slow-spreading MOR tectonics and accretionary prism development in convergent-margin tectonics contributed to the sediment budgets of the cover sequences, and (3) magmatic, tectonic, and sedimen-tological processes that occurred during the formation of the Jurassic oceanic lithosphere and its sedimentary cover in the LPOB were remarkably uniform and synchronous.

In order to promote geosite conservation in the project entitled 'PROactive management of GEOlogical heritage in the PIEMONTE Region', we propose a comprehensive study involving the Monviso Massif (MM) geothematic area, one of the most outstanding symbols of the Alps and particularly of the Cottian Alps. Specifically, at the MM, the inventory of a number of different geosites whose conservation and development require different geologic and some additional non-geological expertise is considered: (1) some of the best preserved ophiolites in the Alps and the associated Cu-Fe mineralizations; (2) the lithostructural units in the Germanasca Valley; (3) the first primary source of jade in the Alps at the MM and its importance in terms of Neolithic to Bronze Age-polished stone implements; (4) the world-famous minerals such as coesite and giant pyrope, as well as type localities for new minerals (including carlosturanite); (5) the area, now buried under a debris flow, where Hannibal is thought to have regrouped his army while crossing the Alps; and (6) the biodiversity of lichens, microfungi and cyanobacteria colonizing the ophiolites, which can give additional value for the environmental assessment and evaluation of the MM outcrops. Following geodiversity identification, further stages will be devoted to develop appropriate plans for geodiversity conservation in this area.

Iso-Kinematic maps have been derived from spatial statistics (Hot Spot and geostatistical analysis) of Permanent Scatterers Interferometric Synthetic Aperture Radar (PS-InSAR) data, and compared with geological, geomorphological, seismological and GPS data in order to analyse the current tectonics and the crustal mobility, at the boundary between the Cottian Alps and the Western Po Plain. This area corresponds to the subsurface junction between the Western Alpine chain and the Northern Apennines. PS data show that the Western Alps are currently uplifting with respect to the adjoining Western Po Plain, as confirmed by the GPS data. The Iso-Kinematic Boundary between these two sectors partly coincides with a regional N–S fault system developed along the inner seismogenic border of the Cottian Alps. Focal mechanisms indicate transpressive movements along this Iso-Kinematic Boundary, which separates two domains characterized by different fault geometry and kinematics, namely: (a) the Cottian Alps, where N–S transtensive/normal faults have developed, and (b) the subsurface Western Po Plain, where NW–SE transpressive/reverse faults are dominant. This articulated tectonic setting results from the complex strain partitioning of the oblique convergence between the European and Adria plates, which is still ongoing, as indicated by seismotectonic and geodetic data.

The 1:5000 scale Geological Map of the Fontane talc mineralization (FTM) aims to give new information about the origin and geological structure of an important talc mineralization occurring in the axial sector of the Italian Western Alps. The FTM is hosted within a pre-Carboniferous polymetamorphic complex which was deformed and metamorphosed during both Variscan and Alpine orogenesis, and is part of the Dora-Maira continental crust. Field mapping and underground investigations highlight that the talc bodies (i) never crop out but occur at depth along a well-defined lithostratigraphic association between micaschist, marble and gneiss and (ii) were deformed during different Alpine-related deformation phases (i.e. D1, D2 and D3 syn-metamorphic phases and post-metamorphic extensional faulting). The here defined lithostratigraphic and structural characterization of talc bodies, is an input for further research into the geodynamic context of where talc forms and for new mineral exploration outside the mapped area.

Chaotic rock units with block-in-matrix structure, commonly known as mélanges and broken formations, are one of the hallmarks of the Alpine orogenic system and of many exhumed convergent plate margins throughout the world. They commonly form in different tectonic settings and structural levels during the evolution of convergent plate margins, reflecting a close relationship between the active processes (tectonic, sedimentary and diapiric), and the physical and mechanical conditions experienced by rocks. Hence, systematic and process-oriented, inter-disciplinary studies of these units may provide much-needed information about the evolution of the Alpine orogenic system and convergent plate margins in general. The relationships between the final block-in-matrix structure and the processes of their formation commonly are, however, obscure and controversial, because of the complex and seemingly chaotic nature. The overlap of shearing, tectonic mixing, and metamorphic recrystallization lead to the reworking and change of the initial block-in-matrix structures formed by different processes (e.g., sedimentary or diapiric), and to the formation of polygenetic mélange. In this framework, block-in-matrix units formed by sedimentary processes may result very difficult-to non-distinguishable when placed in settings such as, for example, accretionary wedges or in a subduction channels or after a complete cycle from subduction to collision, exhumation and intra-continental deformation. We present here different examples of block-in-matrix bodies from the Alpine orogenic system, showing that at shallower structural levels, mélange-forming processes commonly operate in complex and mutual interactions, hence in partial superposition and rarely in isolation. In the geological record of mélanges we commonly observe as the best preserved evidence the artifacts of the last and/or more pervasive process. In most cases, the latter is consistent with tectonics, although sedimentary and/or diapiric-derived structures still characterize notably examples. We show here a comparative analysis of on-land exhumed examples of mélanges and tectonic environments where mélange-forming processes are currently operating. Main types of deformational mode leading to mélange formation include extensional, strike-slip, convergent margin/collisional tectonics, and intra-continental deformation. We discuss: (1) possible relationships between various mélange types and their tectonic setting of formation; (2) contribution of mass-transport versus contractional tectonic deformation processes at the onset of mélange formation (3) nature of the “continuum” and transition from broken formations to true tectonic mélanges.