The External Ligurian units (Northern Apennine, Italy): from rifting to convergence of a fossil ocean-continent transition zone

The External Ligurian Units of the Northern Apennine are interpreted as derived from the continent-ocean transition domain at the northern thinned conti- nental margin of the Adria microplate, i.e. the External Ligurian domain. The evolution of this paleogeographic realm from pre-orogenic times to the Eo- alpine and Meso-alpine tectonics is presented here, through a review of stratigraphic, petrological and structural data. The tectono-metamorphic evolution started in the Late Carboniferous-Early Permian (about 290 Ma), with the emplacement at deep crustal levels of the gabbroic protholits of mafic granulites. These lower continental crust rocks subsequentely underwent Permo-Triassic tectonic exhumation and were finally exhumed at shallow crustal levels in mid- dle Jurassic. The latter period was characterized by extensive brittle faulting at shallow crustal levels, giving rise to extensional allochtons formed by stretched slices of upper continental crust (mainly granitoids). At deep structural levels high temperature shearing of ophiolitic gabbros took place. Opening of the Lig- urian Tethys is finally testified by the basalt emplacement and radiolarian chert sedimentation in the Late Jurassic. During Late Cretaceous, development of Alpine intraoceanic subduction led to the inversion of the External Ligurian domain: the Eo-alpine deformation is recorded by syn-tectonic sedimentation of the Complessi di Base Auct., by development of very low-grade metamorphism and deformation at about 80 Ma. Middle Eocene deformation related with collision and indentation of the Adria with the Alpine accretionary wedge can be subdivided in two main stages: the first one (Ligurian Phase 1) implies large-scale, westward displacement of the EL Units, whereas the second stage (Ligurian Phase 2) is characterized by east- verging structures probably driven by the thinning of the preexisting nappe pile associated with exumation of underplated HP/LT Alpine units

Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

The switching in deformation mode (from distributed to localized) and mechanisms (viscous versus frictional) represent a relevant issue in the frame of crustal deformation, being also connected with the concept of the brittle–ductile transition and seismogenesis. In a subduction environment, switching in deformation mode and mechanisms and scale of localization may be inferred along the subduction interface, in a transition zone between the highly coupled (seismogenic zone) and decoupled deeper aseismic domain (stable slip). However, the role of brittle precursors in nucleating crystal-plastic shear zones has received more and more consideration being now recognized as fundamental in some cases for the localization of deformation and shear zone development, thus representing a case in which switching deformation mechanisms and scale and style of localization (deformation mode) interact and relate to each other. This contribution analyses an example of a millimetre-scale shear zone localized by brittle precursor formed within a host granitic protomylonite. The studied structures, developed in ambient pressure–temperature (P–T) conditions of low-grade blueschist facies (temperature T of ca. 300 °C and pressure P ≥ 0. 70 GPa) during involvement of Corsican continental crust in the Alpine subduction. We used a multidisciplinary approach by combining detailed microstructural and petrographic analyses, crystallographic preferred orientation by electron backscatter diffraction (EBSD), and palaeopiezometric studies on a selected sample to support an evolutionary model and deformation path for subducted continental crust. We infer that the studied structures, possibly formed by transient instability associated with fluctuations of pore fluid pressure and episodic strain rate variations, may be considered as a small-scale example of fault behaviour associated with a cycle of interseismic creep and coseismic rupture or a new analogue for episodic tremors and slow-slip structures. Our case study represents, therefore, a fossil example of association of fault structures related to stick-slip strain accommodation during subduction of continental crust

Late Palaeozoic tectonics in Central Mediterranean: a reappraisal

A revision of late Palaeozoic tectonics recorded in Tuscany, Calabria and Corsica is here presented. We propose that, in Tuscany, upper Carboniferous-Permian shallow-marine to continental sedimentary basins, characterized by unconformities and abrupt changes in sedimentary facies, coal-measures, red fanglomerate deposits and felsic magmatism, may be related with a transtensional setting where upper-crustal splay faults are linked with a mid-crustal shear zone. The remnants of the latter can be found in the deep-well logs of Pontremoli and Larderello-Travale in northern and southern Tuscany respectively. In Calabria (Sila, Serre and Aspromonte), a continuous pre-Mesozoic crustal section is exposed, where the lower-crustal portion mainly includes granulites and migmatitic paragneisses, together with subordinate marbles and metabasites. The mid-crustal section, up to 13 km-thick, includes granitoids, tonalitic to granitic in composition, emplaced between 306 and 295 Ma. They were progressively deformed during retrograde extensional shearing, with a final magmatic activity, between 295 ± 1 and 277 ± 1 Ma, when shallower dykes were emplaced in a transtensional regime. The section is completed by an upper crustal portion, mainly formed by a Palaeozoic sedimentary succession deformed as a low-grade fold and thrust belt, and locally overlaying mediumgrade paragneiss units. As a whole, these features are reminiscent of the nappe zone domains of the Sardinia Variscan Orogen. In Corsica, besides the well-known effusive and intrusive Permian magmatism of the “Autochthonous” domain, the Alpine Santa Lucia Nappe exposes a kilometer-scale portion of the Permian lower to mid-crust, exhibiting many similarities to the Ivrea Zone. The distinct Mafic and Granitic complexes characterizing this crustal domain are juxtaposed through an oblique-slip shear zone named Santa Lucia Shear Zone. Structural and petrological data witness the interaction between magmatism, metamorphism and retrograde shearing during Permian, in a temperature range of c. 800–400 °C. We frame the outlined paleotectonic domains within a regional-scale, strain–partitioned, tectonic setting controlled by a first-order transcurrent/transtensional fault network that includes a westernmost fault (Santa Lucia Fault) and an easternmost one (East Tuscan Fault), with intervening crustal domains affected by extensional to transtensional deformation. As a whole, our revision allows new suggestions for a better understanding of the tectonic framework and evolution of the Central Mediterranean during the late Palaeozoic

Design and performance of a Martian autonomous navigation system based on a smallsat constellation

Deciphering the genesis and evolution of the Martian polar caps can provide crucial understanding of Mars' climate system and will be a big step forward for comparative climatology of the terrestrial planets. The growing scientific interest for the exploration of Mars at high latitudes, together with the need of minimizing the resources onboard landers and rovers, motivates the need for an adequate navigation support from orbit. In the context of the ARES4SC study, we propose a novel concept based on a constellation that can support autonomous navigation of different kind of users devoted to scientific investigations of those regions. We study two constellations, that differ mainly for the semi-major axis and the inclination of the orbits, composed of 5 small satellites (based on the SmallSats design being developed in Argotec), offering dedicated coverage of the Mars polar regions. We focus on the architecture of the inter-satellite links (ISL), the key elements providing both ephemerides and time synchronization for the broadcasting of the navigation message. Our concept is based on suitably configured coherent links, able to suppress the adverse effects of on-board clock instabilities and to provide excellent range-rate accuracies between the constellation's nodes. The data quality allows attaining good positioning performance for both constellations with a largely autonomous system. Indeed, we show that ground support can be heavily reduced by employing an ISL communication architecture. Periodic synchronization of the clocks on-board the constellation nodes with terrestrial time (TT) is enabled through the main spacecraft (the mother-craft), the only element of the constellation enabling radio communication with the Earth. We report on the results of numerical simulations in different operational scenarios and show that a very high-quality orbit reconstruction can be obtained for the constellation nodes using a batch-sequential filter or a batch filter with overlapping arcs, that could be implemented on board the mother-craft, thus enabling a high level of navigation autonomy. The assessment of the achievable positioning accuracy with this concept is fundamental to evaluate the feasibility of a future positioning system providing a global coverage of the red planet

Growth of a sinkhole in a seismic zone of the northern Apennines (Italy)

Sinkhole collapse is a major hazard causing substantial social and economic losses. However, the surface deformations and sinkhole evolution are rarely recorded, as these sites are known mainly after a collapse, making the assessment of sinkhole-related hazard challenging. Furthermore, more than 40% of the sinkholes of Italy are in seismically hazardous zones; it remains unclear whether seismicity may trigger sinkhole collapse. Here we use a multidisciplinary data set of InSAR, surface mapping and historical records of sinkhole activity to show that the Prà di Lama lake is a long-lived sinkhole that was formed in an active fault zone and grew through several events of unrest characterized by episodic subsidence and lake-level changes. Moreover, InSAR shows that continuous aseismic subsidence at rates of up to 7.1mmyr-1occurred during 2003-2008, between events of unrest. Earthquakes on the major faults near the sinkhole do not trigger sinkhole activity but low-magnitude earthquakes at 4-12 km depth occurred during sinkhole unrest in 1996 and 2016. We interpret our observations as evidence of seismic creep at depth causing fracturing and ultimately leading to the formation and growth of the Prà di Lama sinkhole

Reciprocal regulation of PKA and rac signaling

Activated G protein-coupled receptors (GPCRs) and receptor tyrosine kinases relay extracellular signals through spatial and temporal controlled kinase and GTPase entities. These enzymes are coordinated by multifunctional scaffolding proteins for precise intracellular signal processing. The cAMP-dependent protein kinase A (PKA) is the prime example for compartmentalized signal transmission downstream of distinct GPCRs. A-kinase anchoring proteins tether PKA to specific intracellular sites to ensure precision and directionality of PKA phosphorylation events. Here, we show that the Rho-GTPase Rac contains A-kinase anchoring protein properties and forms a dynamic cellular protein complex with PKA. The formation of this transient core complex depends on binary interactions with PKA subunits, cAMP levels and cellular GTP-loading accounting for bidirectional consequences on PKA and Rac downstream signaling. We show that GTP-Rac stabilizes the inactive PKA holoenzyme. However, β-adrenergic receptor-mediated activation of GTP-Rac–bound PKA routes signals to the Raf-Mek-Erk cascade, which is critically implicated in cell proliferation. We describe a further mechanism of how cAMP enhances nuclear Erk1/2 signaling: It emanates from transphosphorylation of p21-activated kinases in their evolutionary conserved kinase-activation loop through GTP-Rac compartmentalized PKA activities. Sole transphosphorylation of p21-activated kinases is not sufficient to activate Erk1/2. It requires complex formation of both kinases with GTP-Rac1 to unleash cAMP-PKA–boosted activation of Raf-Mek-Erk. Consequently GTP-Rac functions as a dual kinase-tuning scaffold that favors the PKA holoenzyme and contributes to potentiate Erk1/2 signaling. Our findings offer additional mechanistic insights how β-adrenergic receptor-controlled PKA activities enhance GTP-Rac–mediated activation of nuclear Erk1/2 signaling

Buone prassi per l'autismo

Perchè dare indicazioni per “Buone prassi per l'autismo”? Nel corso degli anni la ricerca ha migliorato notevolmente la conoscenza della sindrome del disturbo autistico riconoscendone la presenza in una ampia varietà di forme che prima erano classificate in modo diverso (es. autismo, sindrome di Asperger, psicosi infantile…). Raggruppare in una unica classe la varietà delle forme ha comportato l'aumento considerevole del numero di diagnosi di autismo; questo ha motivato e dato impulso alla ricerca sulla etiologia, sui possibili interventi e sulla loro efficacia