MIGRAZIONE NEOGENICA DEL SISTEMA CATENA-AVAMPAESE NELL'APPENNINO MERIDIONALE: PROBLEMATICHE PALEOGEOGRAFICHE E STRUTTURALI

On the base of some tentative geological profiles across the external areas of the Lucanian Apennines (Southern Italy), worked out by means of field and well data, has been possible to restare the generai geometrical framework. The results allow to discuss the possible evolution in time and space of the processes associated with the thrust faulting. Starting from the external zones it's possible to recognize two major structural elements: the Apulian Foreland and the Apenninic Chain. The Apulian Foreland, a very thick from Mesozoic to Pleistocene carbonate sequence, is downfaulted toward SW giving rise to a foredeep: the Bradanic Trough. Internal to this foredeep zone a carbonate platform more or less deformed from Upper Mio­cene onwards, has been recognized. It probably represents the more internal extension of the Apulian plat­form. Thus we distinguish an "Apulian Chain" representing a sector of the foreland, deformed since Late Mio­cene times, from the Apulian Foreland, where extensional regime was predominant

Convective Instability in Intraplate Oceanic Mantle Caused by Amphibolite-Derived Garnet-Pyroxenites—A Xenolith Perspective (Hyblean Plateau, Sicily)

Geochemical characteristics of middle ocean ridge basalts (MORBs) testify partial melting of spinel-peridotite mixed with a few amounts of garnet-pyroxenite. The latter can be considered either autochthonous products of the crystallization of partial melts in the sub-oceanic mantle or allocthonous recycled crustal materials originated in subduction contexts. Here we suggest the “autocthnous recycled” origin for garnet-pyroxenites. Such a hypothesis derives from the study of garnet-bearing pyroxenite xenoliths from the Hyblean Plateau (Sicily). These consist of Al-diopside, pyralspite-series garnet, Al-spinel and Al-rich orthopyroxene. Trace element distribution resembles an enriched MORB but lower chromium. Major-element abundances closely fit in a tschermakitic-horneblende composition. Assuming that a high-Al amphibolite was formed by hydrothermal metasomatism of a troctolitic gabbro in a slow-spreading ridge segment, a transient temperature increasing induced dehydroxilization reaction in amphiboles, giving Al-spinel-pyroxenite and vapor as products. Garnet partially replaced spinel during an isobaric cooling stage. Density measurements at room conditions on representative samples gave values in the range 3290–3380 kg m−3. In general, a density contrast ≥300 kg m−3 can give rise to convective instability, provided a sufficient large size of the heavy masses and adequate rheological conditions of the system. Garnet-pyroxenite lumps can therefore sink in the underlying mantle, imparting the “garnet geochemical signature” to newly forming basaltic magma

Un géomorphosite : les Monts hybléens (sud-est de la Sicile)

Hyblean mounts as Geomorphosites (SE Sicily). The southeastern area of Sicily, constituted by the orographic system of the Hyblean Mountains, differs from the remaining reliefs of the island because of some géomorphologie characteristics which are a consequence of a series of cyclic erosion and corrosion processes, acting from the end of the Miocene on those parts of land on the way to emerge. This area which, from a geologic point of view, constitutes the emerged foreland of the most advanced northern African shelf, appears as a wide plateau, rich in carbonates and not much deformed, sloping down from its highest northern peak of basaltic outcrops at Monte Lauro volcano, at about 1 000 m, both eastward toward the Ionian coast and southward toward the Mediterranean coast. The plateau appears extensively dissected by a dendritic network of deep valleys originated mostly through processes of fluvial erosion and karst corrosion types (canyons, gorges, giant potholes, etc.). These erosive and corrosive actions have produced a range of morphologies so various and special to give to the natural relief the most beautiful and charming landscape characteristics among those present in the whole island. Among the most spectacular ones : Cava Grande del Cassibile, Valle dell'Anapo, Valle del Tellesimo, Gole della Stretta, just to mention a few. Another interesting particularity which characterizes the Hyblean landscape is constituted by the surface and hypogeous karst morphologies, originated both in Messinian gypsum outcrops and in the outcropping of Oligocene-Miocene limestone rocks. In the topmost areas or those areas with little slope, where bare rocks outcrop, there is a widespread variety of solution pans, clefts, and karst holes, while on the steepest slopes various sizes of karren and grooves outline the bare rocky surface. Karst springs and spring-caves, in the valleys, feed the streams even during the summer season, while, along escarpments, paleo-grooves, rock shelters, and entrances of wider fossil caves yield evidence for ancient river base levels. In the Hyblean Mountains there are many caves of aesthetic interest, due to the particular morphologies, beauty and variety of the speieothems (Grotta Monello, Genovese, etc.) ; other caves have a remarkable scientific value, due to the geological and hydrogeological aspects (Villasmundo-Alfio karst system, Grotta di Valle Paradiso, Palombara, etc.) ; further caves are important for archaelogic (Riparo di Fontana Nuova, Grotta Chiusazza, Grotta Giovanna, Grotta di Calafarina), biospeleologic (Grotta Monello, Grotta del Conzo, etc.), and paléontologie (Grotta Spinagallo, Grotta Cimillà, and so on) findings. The previously mentioned physical and historical/anthropic characteristics, along with the magic setting of scented Mediterranean brushwood, without any doubt, attribute to the orographic setting of the Hyblean Mountains the denomination of "geomorphosite" of significant scientific and cultural interest in order to establish it as a park with subsequent benefits for the protection and promotion of abiotic and biotic aspects, and its intelligent and guided fruition by the local and foreign communities (geotourism, thematic paths, etc.).Geomorfositi dei Monti Iblei (SE Sicilia). II settore sud-orientale della Sicilia, costituente il sistema orografico dei Monti Iblei, si contraddistingue dal resto dei rilievi dell'isola per alcune particolarità geomorfologiche che sono il risultato di una serie di ciclici processi erosivi e corrosivi agenti sulle aree in via di emersione a partire dalla fine del Miocene. Tale settore, che sotto il profilo geologico, costituisce la zona di avampaese emersa dell'estrema propaggine settentrionale della piattaforma af ricana, si presenta come un esteso altopiano, prevalentemente carbonatico e poco deformato, dégradante dalla sua massima culminazione settentrionale degli affioramenti basaltici di Monte Lauro, sui 1 000 m, sia verso est fino alia costa ionica, che verso sud fino alia costa mediterranea. L'altopiano si presenta diffusamente dissecato da una rete dendritica di profonde valli originatesi prevalentemente per processi tipo erosivo fluviale e corrosivo carsico (canyon, gole, forre, marmitte, ecc.). Le suddette azioni erosive/corrosive hanno prodotto un insieme di morfologie la cui varietà e singolarità è tale da conferire al rilievo naturale connotazioni paesaggistiche fra le più affascinanti e suggestive fra quelle present i in tutta l'isola. Fra queste : Cava Grande del Cassibile, la Valle dell'Anapo, la Valle del Tellesimo, le Gole della Stretta, solo per citarne alcune fra le più spettacolari. Un'altra intéressante peculiarità fisica che caratterizza il paesaggio Ibleo è quella delle morfologie carsiche, sia superficiali che ipogee, originatesi sia negli affioramenti evaporitici che nelle rocce carbonatiche eo-mioceniche affioranti. Nelle aree sommitali o a debole pendenza, laddove affiora la roccia nuda, è presente una diffusa varietà di vaschette, crepacci e fori carsici, mentre sui più ripidi versanti scannellature e docce di varie dimensioni disegnano la nuda superficie rocciosa. Sui fondovalle sorgenti carsiche e grotte-sorgenti alimentano il deflusso vallivo, anche nel periodo estivo, mentre lungo i pendii paleo-solchi, ripari sotto roccia e ingressi di più estese cavità fossili testimoniano di antichi livelli di base dei fiumi. Diverse le cavità di interesse estetico, per la particolarità delle morfologie e per la bellezza e varietà degli speleotemi (Grotta Monello e Genovese) ; altre di notevole valore scientifico, per gli aspetti geologici e idrogeologici (Complesso Villasmundo-Alfio, Grotta di Valle Paradiso) ; altre ancora per i ritrovamenti archeologici (Riparo di Fontana Nuova, Chiusazza, Grotta di Calafarina), paléontologie i (Grotta Spinagallo, Cimillà) e biospeleologici (Grotta del Conzo, Grotta Monello). Le peculiarità fisiche e storico-antropiche, anzi ri porta te, inserite in un magico scenario di fragrante macchia mediterranea, conferiscono a pieno titolo al contesto orografico dei Monti Iblei, I'attributo di geomorfosito di particolare interesse scientifico e culturale ai fini di una sua auspicata istituzione a Parco con conseguenti benefici sia per la salvaguardia e valorizzazione degli aspetti abiotici e biotici presenti, che per una sua intelligente e guidata fruizione da parte della collettività locale e straniera (geoturismo, sentieri tematici, ecc.).Le sud-est de la Sicile, et plus précisément le système orographique des Monts Hybléens, diffère des autres massifs de l'île en raison de plusieurs caractéristiques géomorphologiques résultant d'une série de cycles d'érosion et de corrosion actifs à partir de la fin du Miocène au fur et à mesure que ces terrains commençaient à émerger. Ce secteur, constitue d'un point de vue géologique la partie émergée la plus septentrionale du plateau continental africain et apparaît comme un vaste plateau à dominante calcaire, peu déformé. Depuis le sommet du volcan du Monte Lauro dont les pointements basaltiques culminent vers 1 000 mètres d'altitude, les versants descendent à l'est vers le littoral ionien et au sud vers la côte méditerranéenne. Le plateau est extrêmement disséqué par un réseau dendritique de profondes vallées issues pour la plupart de processus d'érosion fluviale et de corrosion karstique (canyons, gorges, marmites de géant, etc.). Ces phénomènes d'érosion et de corrosion ont produit une série de morphologies si variées et spécifiques qu'elles ont donné au relief les paysages naturels les plus ravissants et grandioses de toute l'île. Parmi les plus spectaculaires et pour n'en citer que quelques-unes : Cava Grande del Cassibile, Valle dell'Anapo, Valle del Tellesimo, Gole della Stretta. Une autre particularité intéressante des paysages hybléens est liée à leur morphologie de surface et aux formes karstiques souterraines, développées à la fois dans les affleurements de gypse messiniens et dans les affleurements calcaires de l'Oligocène-Miocène. Dans les zones les plus élevées ou dans les secteurs de faible pente, là où le rocher affleure, les kamenitzas sont très répandues, tout comme les lapiaz et les gouffres karstiques, alors que dans les zones abruptes on retrouve de nombreuses dalles rocheuses parcourues de cannelures de taille variable. Les sources karstiques situées dans les vallées alimentent les écoulements de surface, y compris lors de l'étiage estival. La bordure des escarpements abrite des paléo-drains, des abris sous roche, et des entrées de vastes cavités fossiles témoins d'un ancien niveau de base du réseau hydrographique. Les Monts hybléens possèdent de nombreuses cavités ayant un intérêt esthétique, du à leur morphologie particulière, ou la beauté et la variété des spéléothèmes (Grotta Monello, Genovese, etc.) ; d'autres cavités doivent leur intérêt scientifique remarquable à la géologie et à l'hydrogéologie (système karstique de Villasmundo-Alfio, Grotta di Valle Paradiso, Palombara, etc.) ; d'autres ont surtout un intérêt archéologique (Riparo di Fontana Nuova, Grotta Chiusazza, Grotta Giovanna, Grotta di Calafarina), biospéologique (Grotta Monello, Grotta del Conzo, etc.) ou paléontologique (Grotta Spinagallo, Grotta Cimillà).Ruggieri Rosario, Carbone Serafina, Galletti Iolanda. Un géomorphosite : les Monts hybléens (sud-est de la Sicile). In: Karstologia : revue de karstologie et de spéléologie physique, n°54, 2e semestre 2009. La grotte de Kanaan (Liban) et Géomorphosites karstiques. pp. 11-20

Il progetto CARG in Basilicata: il Foglio 489 Marsico Nuovo

The stratigraphic and structural features of the Apenninic Chain exposed in the Marsico Nuovo sheet are shortly described. The Apenninic edifice is composed of tectonic units, originated since Oligocene time. It is completely detached and resting onto a deep seated thrust system (the Apulian thrust system), deformed since Tortonian in contemporaneous with the Tyrrhenian opening. The geodynamic evolution of this latter influenced the further movements of the Apenninic Chain. Stratigraphic characters of the sequences outcropping in the studied area are here discussed. The deepest units are the Lagonegrese Mesozoic basinal sequences; these underlie the coeval carbonate platform units. A general decoupling between the Mesozoic sequences and the Tertiary flysch-type terrigenous covers occurs. Oil field traps have been dected in the ramp-anticlines of the buried thrust system and a lots of subsurface data allows to restore the whole geodynamic evolution of this area

Origin of saponite-rich clays in a fossil serpentinite-hosted hydrothermal system in the crustal basement of the Hyblean Plateau (Sicily, Italy)

A diapiric intrusion of clays in the Carlentini Formation (Tortonian) was discovered in a quarry at S. Demetrio High (Hyblean Plateau, Sicily, Italy). Seven clay samples were analyzed by different analytical methods, including X-ray powder diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy, to determine the composition and mechanism of formation (sedimentary vs. hydrothermal) of these clays. Ferric saponite, carbonates (calcite and traces of ankerite), quartz, pyrite, and zeolites (phillipsite and harmotome) were detected using XRD and FTIR. This mineral assemblage, dominated by Fe-rich saponite, and the abundance of light rare-earth elements (LREE), Eu, fluid-mobile elements (FME > 10× primordial mantle: Li, Be, B, As, Sb, Pb, U, Ba, Sr, Cs), and other incompatible elements (Zr = 169 ppm, Nb = 46 ppm, Th = 11 ppm, on average) imply that S. Demetrio clays precipitated from a mixture of hot Si-rich hydrothermal fluids (350-400°C) and cold seawater. The evidence is in accord with the affinity of clays for hydrothermally modified mafic and ultramafic rocks, forming the Hyblean lower crust, based on multi-element comparisons, and on the occurrence of trace amounts of chrysotile 2M and sepiolite. The association of long-chain aliphatic-aromatic hydrocarbons (intensity ratios I /I > 0.5) with hydrothermal clays, the lack of fossils, and the similarity of the IR absorption bands with those of organic compounds detected previously in some metasomatized Hyblean gabbroic xenoliths suggest a possible abiogenic origin of hydrocarbons via a Fischer-Tropsch-type reaction. The S. Demetrio clay diapir was emplaced at shallow crustal levels in the Late Miocene as a consequence of the interaction, at a greater depth, of an uprising basalt magma and the products of an early, serpentinite-hosted hydrothermal system

Tectonic evolution of the Northern Sicanian-Southern Palermo Mountains range in Western Sicily: insight on the exhumation of the thrust involved foreland domains

Geological mapping and structural analysis, coupled with extensive samplings on terrigenous Tertiary covers, enable us to reconstruct the structural setting as well as the tectonic evolution of the northern Sicanian-southern Palermo Mountains range in western Sicily. The analyzed region is a segment of the Apenninic-Maghrebian Orogen characterized by the occurrence of two regional superimposed tectonic edifices; the Apenninic-Maghrebian Chain (AMC) and the Pelagian Sicilian Thrust Belt (PSTB) which constitute the uppermost and lowermost structural level respectively. The different structural associations generally suggest a multiphase tectonic history in which we distinguished three main deformational events. The oldest one is characterized by the development of low-angle foreland-verging large thrust contacts. These usually propagated along Lower-Middle Miocene terrigenous levels and leads to the staking of the AMC. As a whole the AMC structured during Middle Miocene and tectonically overrode the Pelagian foreland since Tortonian time. The subsequent tectonic phase developed as effect of continental collision with the propagation of south verging high-angle thrust faults. These involve mainly the underlying Pelagian foreland giving rise to the imbrications at depth of the PSTB. The more recent tectonic phase starts since Middle Pliocene with the activation of NW-SE oriented right-lateral traspressive shear zones and associated double verging E-W striking thrust contacts. These latter occurred mainly in the overlapping area between major shear zones and are responsible for the final uplift of the previously imbricate PSTB. During this tectonic stage the previously E-W oriented structural features suffered local clockwise rotations in the neighbours of the main right-lateral shear zones. In this newly proposed structural framework, we interpreted the Mt. Kumeta and Rocca Busambra carbonate ridges as a Pliocene push-up type antiformal structures grown and exhumed at restraining stepovers in a contest of regional strike-slip kinematic

Tracking the Serpentinite Feet of the Mediterranean Salt Giant

Interpretation of seismic profiles and results of scientific drillings in the Mediterranean subseafloor provided indication of gigantic salt deposits which rarely crop out on land, such as in Sicily. The salt giants were ascribed to the desiccation, driven by the solar energy, of the entire basin. Nevertheless, the evaporite model hardly explains deep-sea salt deposits. This paper considers a different hypothesis suggesting that seawater reached NaCl saturation during serpentinization of ultramafic rocks. Solid salts and brine pockets were buried within the serpentinite bodies being later (e.g., in the Messinian) released, due to serpentinite breakdown, and discharged at seafloor as hydrothermal heavy brines. Therefore, sea-bottom layers of brine at gypsum and halite saturation were formed. The model is applicable to the Mediterranean area since geophysical data revealed relicts of an aged (hence serpentinized) oceanic lithosphere, of Tethyan affinity, both in its western “Atlantic” extension (Gulf of Cádiz) and in eastern basins, and xenoliths from Hyblean diatremes (Sicily) provided evidence of buried serpentinites in the central area. In addition, the buoyant behavior of muddled serpentinite and salts (and hydrocarbons) gave rise to many composite diapirs throughout the Mediterranean area. Thus, the Mediterranean “salt giant” consists of several independent geobodies of serpentinite and salts