Vincenzo Festa

Sinkhole evolution in the Apulian Karst of Southern Italy: a case study, with some considerations on Sinkhole Hazards

Sinkholes are the main karst landforms characterizing the Salento Peninsula, which is the southernmost part of the Apulia region of southern Italy. They occur both as evolving recent phenomena and old or relict features testifying to ancient phases of karst processes acting in the area. Most of the sinkholes were formed by karst processes that may be reactivated, a risk to the anthropogenic structures nearby. To highlight such a subtle hazard, an area located a few kilometers from Lecce, the main town in Salento, was the subject of geological, morphological, and geophysical investigations. Historical analysis of multi-year aerial photographs, in particular, allowed identification of several phases in the recent evolution of a particular sinkhole, and demonstrated the need to carefully evaluate the likely evolution of similar features in Salento.

Time Constraints on the Building of the Serre Batholith: Consequences for the Thermal Evolution of the Hercynian Continental Crust Exposed in Calabria (Southern Italy)

New laser ablation inductively coupled plasma mass spectrometry U-Pb dating on zircon and monazite was performed to estimate the time required for the building of the Serre batholith in Calabria. Age spectra from the bottom and top of the pluton are characterized by two main peaks at 306 and 295 Ma, resulting from a mutual interference between serial intrusive events. On this basis, the emplacement of the top granodiorite layer postdates by about 10 m.yr. emplacement of the lower tonalite layer. These results have been incorporated into a two-dimensional numerical thermal model, assuming overaccretion of a batholith in an extensional tectonic regime. With this approach it was possible to reproduce pressure-temperature paths for various levels of the continental crust and define timing for low-pressure regional and contact metamorphism. In a unique tectonomagmatic scenario the model reproduces regional low-pressure metamorphic effects in the lower to intermediate continental crust and, with a time lag of about 6 m.yr., contact metamorphism in the upper crust. Finally, we propose a conceptual model for the emplacement of the Serre batholith in an extensional tectonic setting. Space for magma can be created by lower crust thinning and rock uplift at the bottom and top of the batholith, respectively.

Late-Hercynian shearing during crystallization of granitoid magmas (Sila massif, southern Italy): regional implications

Shearing of regional extent, involving granitoids and underlying mid-crustal rocks of the Sila massif (Calabria, Italy), is analysed in this paper. The deformed granitoids are affected by a wide NNW-SSE oriented deformation zone, stretching for about 60 km, from the neighbourhood of Cecita Lake to Cropani village. Meso- and micro-structures in granitoids, close to the boundary with underlying migmatitic paragneiss, indicate that deformation developed from melt-present to solid-state conditions. Simultaneous tectonics and magmatism activated a plutonic accretionary process at mid-crustal levels. This took place at about 300 Ma and involved hybrid magmas with a dominat contribution from a mantle source. The deformation regime remained steady for a long time during magma crystallization and cooling in subsolidus conditions. The regional top-to-the-W sense of shear in the present geographic coordinates, recorded in the deformed granitoids, seems geometrically consistent with the coeval direction of maximum extension found in another sector of the southern Hercynian belt, suggesting the original position of the Sila basement in this context. Magmatic ativity ended with the intrusion of mafic and felsic magams affected by a very weak deformation, ongoing during the final strain increments of the late-Hercynian stage.

Time–space relationships among structural and metamorphic aureoles related to granite emplacement: a case study from the Serre Massif (southern Italy)

Tectonic and thermal perturbations, related to emplacement of granodiorite in the upper continental crust, have been investigated in the late-Hercynian basement exposed in southern Calabria (Italy). Here, the structural aureole is marked by the presence of a major rim fold adjacent to the intrusive contact for a length of at least 20 km. Geometrical analysis of the structural aureole and related foliations, lineations and crenulations reveals that the perturbed zone is at least 3000 m wide and characterized by an open synform trending nearly parallel to the intrusive contact. This pattern is compatible with a laccolith-like mode of magma emplacement, related to the accretion of the pluton that shouldered weak phyllitic and slaty wall rocks. The metamorphic aureole, about 1800 m wide, is characterized by biotite, cordierite and andalusite that appear sequentially in spotted schists and hornfelses approaching the intrusive contact. The peak assemblage equilibrated between 535 and 590°C at pressures between 175 and 200 MPa, confirmed by Al-in-hornblende barometry on granodiorite. Microstructural analysis allowed the inference of a time lag between the thermal and tectonic perturbations. With the aid of thermal modelling it was possible to quantify the time required to reach the peak temperature at a distance from the intrusive contact where cordierite spots and andalusite porphyroblasts clearly overprint crenulations. This estimate represents the time limit to accomplish deformation in the inner portion of the aureole and thus indicates a minimum strain rate of 4 × 10 −14 s −1 within the country rocks during granodiorite intrusion.

Dike magmatism in the Sila Grande (Calabria, southern Italy): Evidence of Pennsylvanian–Early Permian exhumation

A dike network transecting a basement of intrusive and metamorphic rocks related to the Hercynian orogeny is exposed in the Sila Grande (southern Italy). Dike magmatism, similarly to other regions of the western Mediterranean, such as Sardinia, Corsica, and Catalonia, is of calc-alkaline to alkali-calcic affinity. Zircon U-Pb geochronology indicates that dike magmatism took place between 295 ± 1 to 277 ± 1 Ma, after the main late Hercynian emplacement of granitoids (306 ± 1 Ma). Barometry indicates that the basement underwent exhumation of 8 ± 3 km before dike injection. The dike network has a geometrical arrangement consistent with a transtensional stress regime that resulted in ductile thinning of the lower crust during the late stage of the Hercynian orogeny and concurrent fracturing of the upper crust that made possible magma ascent through dikes. The proposed tectonic evolution is related to dismemberment of the southern Hercynian belt in the central Mediterranean area as a result of dextral transtension of Gondwana in relation to Laurasia during the Pennsylvanian–Early Permian.

1:5,000 geological map of the upper Cretaceous intraplatform-basin succession in the Gravina di Matera canyon (Apulia Carbonate Platform, Basilicata, southern Italy)

Along the slopes of the Gravina di Matera canyon, below and in front of the Sassi di Matera, i.e., the old Matera town (Basilicata, southern Italy), an about 200 m thick succession of upper Cretaceous carbonates extensively crops out. These carbonates belong to the Apulia Carbonate Platform and, in the official geological map, are referred to the Calcare di Altamura Fm, a lithostratigraphic unit composed of shallow-marine peritidal limestones. In order to study the whole outcropping succession, a geological survey was performed in the area and an unaspected intraplatform shallow-basin suite of limestones has been recognized within the Calcare di Altamura Fm. On the basis of lithologic characters, the whole succession has been divided into informal lithostratigraphic units a-g. The base of the succession (unit a) is represented by a crudely stratified bioclastic floatstone-rudstone locally interested by in situ brecciation, a phenomenon that often is the precursor of deep changes in a carbonate platform. Unit a sharply passes upward to thinly bedded and finely planar-laminated mudstone interested by slumps (unit b), conformably covered by dolostones (unit c). Dolostone gradually passes to cherty limestones (unit d) that in turn pass to wackestones (unit e) covered by a megabreccia (unit f). All these units (a-f) indicate that this area of the Apulia Platform performed a change from classic platform environments to slope- and to basin-ones, before the restarting of typical facies of shallow-marine carbonate platform environments (unit g). This subdivision in units of the outcropping succession led us to informally define a member, the Matera member (ALT1), within the upper Cretaceous Calcare di Altamura Fm (ALT). Most likely, the Matera member (units a-f) represents a shallow-basin developed within the Apulia Platform during Late Cretaceous, most likely related to extensional tectonics. Other examples of slope-to-basin sedimentary suite were previously observed within the upper Cretaceous succession of the Apulia Platform and the occurrence of another shallow-basin in the interior of the same platform opens a new and still understimated regional tectonic- and paleogeographic-scenario. Moreover, it should be highlighted that the geological surveyed area belongs to a Regional Natural Park since the 1990 (Parco Archeologico Storico Naturale delle Chiese Rupestri del Materano also known as Parco della Murgia Materana) and that Matera, besides being in the Unesco Word Heritage list since the 1993, has been voted European Capital of Culture 2019. Therefore, the obtained 1:5,000 geological map, apart from documenting some lithostratigraphic evidences of the intraplatform basin, represents an essential tool for both (i) future studies regarding the upper Cretaceous tectono-stratigraphic evolution of the Apulia Platform, and (ii) a geological base for many visitors interested in the cultural and geological heritage of Matera and its territory.

The amount of pure shear and thinning in the Hercynian continental lower crust exposed in the Serre Massif (Calabria, southern Italy): an application of the vorticity analysis to quartz c-axis fabrics

New petrographic and geologic data on the lower continental crust exposed in the Calabrian Arc are reported with the aim to shed some lights on the thinning episode occurred during the late stages of the Hercynian orogeny. Previous petrologic studies provide some constraints for the decompression mechanisms in different levels of the continental crust. However, an integral view of the exhumation mode, which took place during the Late Carboniferous, is still missing.This paper used the method of vorticity analysis, which takes into account new quartz c-axis measurements and microstructural observations on high-grade metasediments to estimate the value of the vorticity number (Wm).In addition, calculation of Wm allowed obtaining: i) the percentage of pure vs. simple shear and ii) the amount of thinning of the Hercynian continental lower crust exposed in Calabria.The final scenario is derived where pure shear played a major role in the thinning of the lower crust, whose original thickness is estimated to be two and half times the present-day value. Comparing this result with the well-known petrologic data, it is concluded that the late-Hercynian thinning preferentially took place in the lower crust and, along with erosion, would be the main responsible for the present-day overall crustal thickness.

From the upper to the lower continental crust exposed in Calabria

Outcrops of the pre-Mesozoic basement, representative of the whole Hercynian continental crust are exposed in Calabria. This is the result of Tertiary geological evolution that brought to the surface different crustal levels. This geological field trip aims to provide a general picture of the continental crust that hopefully may represent a reference frame for geochemical, rheological and geophysical models. The itinerary develops in central and southern parts of Calabria, namely in the Serre massif and in the promontories of Capo Vaticano and Monte Sant’Elia. In three days it is possible to examine compositional and structural features across an entire crust section. Thus rocks affected by very low-grade to granulite facies metamorFrom the upper to the lower continental crust exposed in Calabria A. Caggianelli G. Prosser V. Festa A. Langone R. Spiess geogical feld tips 2013 51.2) DOI: 10.3301/GFT.2013.02 in fo rm a io n 5 phism and distinctive features of granitoids emplaced at different structural levels will be examined. The effects of the intense thermal perturbation produced by granitoid emplacement are visible both in the upper and in the lower crust, in a sharp metamorphic aureole and in a migmatitic border zone, respectively. Finally, some cases of Paleozoic rocks with strongly partitioned deformation, produced by Tertiary tectonics in the brittle and the ductile domains, can be observed.

The tectono-magmatic setting of the Hercynian upper continental crust exposed in Calabria (Italy) as revealed by the 1:10,000 structural-geological map of the Levadio stream area

This study presents a structural-geological map illustrating the tectonic contact between the Stilo-Pazzano Phyllite Unit and the Mammola Paragneiss Unit. Their juxaposition is exposed in the Paleozoic upper continental crust cropping out in the southern Serre Massif. Since the geometry of the contact has never been defined before, a detailed geological survey has been carried out in the Levadio stream area, i.e. one of the most promising areas to constrain the tectono-magmatic setting of the Hercynian upper continental crust exposed in Calabria. A structural-geological map, at a scale 1:10,000, has been constructed, including also Upper Carboniferousgranodiorites, belonging to the Serre batholith, and Lower Permian felsic dykes, both useful time markers to constrain the minimum age for the juxtaposition of the Stilo-Pazzano Phyllite and Mammola Paragneiss units wall rocks. According to petrographic and structural observations, the attempt to discriminate on the geological map the main deformation events has been made also by the use of tracing distinct fold-axial-planes, each referring to the related contractional deformation event. This approach makes the geological map intuitive for the relative timing of the deformational events affecting the Stilo-Pazzano Phyllite and Mammola Paragneiss units. The geological mapping of the Levadio stream area shows that the post-Visean – pre-Upper Carboniferous tectonics was characterized by a main extensional event, that was responsible for the juxtaposition of the Mammola Paragneiss Unit (below) and the Stilo-Pazzano Phyllite Unit (above) under greenschist facies conditions. Three subsequent, progressively weaker contractional deformation events occurred in response to the late Hercynian emplacement and incremental growth of the Serre batholith.

Texture and composition of the Rosa Marina beach sands (Adriatic coast, southern Italy): a sedimentological/ecological approach

Abstract Beach sands from the Rosa Marina locality (Adriatic coast, southern Italy) were analysed mainly microscopically in order to trace the source areas of their lithoclastic and bioclastic components. The main cropping out sedimentary units were also studied with the objective to identify the potential source areas of lithoclasts. This allowed to establish how the various rock units contribute to the formation of beach sands. The analysis of the bioclastic components allows to estimate the actual role of organisms regarding the supply of this material to the beach. Identification of taxa that are present in the beach sands as shell fragments or other remains was carried out at the genus or family level. Ecological investigation of the same beach and the recognition of sub-environments (mainly distinguished on the basis of the nature of the substrate and of the water depth) was the key topic that allowed to establish the actual source areas of bioclasts in the Rosa Marina beach sands. The sedimentological analysis (including a physical study of the beach and the calculation of some statistical parameters concerning the grain-size curves) shows that the Rosa Marina beach is nowadays subject to erosion.