Stefano Catalano

Pleistocene strike‐slip tectonics in the Lucanian Apennine (southern Italy)

Structural studies carried out in the Lucanian Apennines (Southern Italy) show that strike-slip faulting was the principal mode of deformation of this area during middle-upper Pleistocene time. W-NW to E-SE trending left strike-slip fault systems dissect the entire Apennine mountain belt and affect the preexisting thrust geometry. Strike-slip faults, activated by a roughly E-W shortening, are characterized by different geometries representing the surface response to lateral motion occurring along deep-seated structures. The occurrence of different structural patterns which characterize different segments of strike-slip system is related to (1) the depth of a major decoupling surface which separates the upper tectonic multilayered horizon (Apennines thrust belt system) from the lower rigid horizon (Apulian belt) in which strike-slip structures have originated and (2) the geometric relationships between the strike-slip faults and the thrust belt pattern which characterize the upper horizon. The different segments of the strike-slip system are interpreted as internal deformation developed within a crustal shear zone. This zone, which corresponds to the boundary between the Apulian block and the Apennine chain, is characterized by sinistral movement as a response to the northwesterly convergent motion of the African plate with respect to Europe.

Late Quaternary uplift of northeastern Sicily: relation with the active normal faulting deformation

Abstract The evaluation of the vertical displacement-rate of the Late Quaternary marine terraces along the Ionian coast of northeastern Sicily (southern Italy) has been adopted as a tool to reconstruct the Late Quaternary deformation affecting the aseismic area, intervening between the Calabrian arc and the eastern Sicily seismogenic regions. The methodology adopted, based on computer elaboration of the field data, provided the amount of the uplift recorded since 124 ka, partitioned in the time, with the resolution of the oxygen isotope timescale (OIT) stages. The main result of the analysis is the recognition of a recently deformed sector of the coast, corresponding to the area of underlap between the seismogenic faults of southern Calabria and eastern Sicily. The deformation path of the Late Quaternary shorelines is consistent with the occurrence of an active normal fault in the off-shore of the area. This tectonic feature, that crosses through a main crustal barrier, represents the link between the two sets of seismogenic faults that cut through the weakened sectors of the crust. The resulting picture clearly indicates the influence of crustal properties on the geometry of the active fault belt and on the distribution of the main seismic events along the active “Siculo-Calabrian Rift Zone”.

Morphological evidence of Holocene coseismic deformation in the Taormina region (NE Sicily)

In southern Italy, strongly uplifted coastal regions are located along the footwall of the main seismogenic fault segments which affect the Tyrrhenian side of southern Calabria and the Ionian coast of eastern Sicily. This morphotectonic picture is generally associated with high-level historical seismicity. An anomaly is represented by the Ionian coast of NE Sicily that, located on the footwall of the offshore Taormina Fault, is affected by very low to absent historical seismicity. A detailed levelling survey of dated Holocene marine notches has been carried out along the coast of Taormina and Capo S. Alessio, at the southern termination of the Taormina Fault, where a converging set of Late Quaternary strandlines marks the tip of this offshore structure. The Holocene marine marks, represented by three main notch levels separated by lithophaga bands dated at 5 ka and post-3.2 ka, are severely tilted towards the onshore and show a clear divergence from the southern tip of the Taormina Fault towards the north. Taking into account the slow rate of sea-level rise characterising the Central Mediterranean during the last 5 ka (0.3–1.0 mm/year), the vertical distribution of the Holocene strandlines can be interpreted as the result of short-period variations in the rate of tectonic uplifting. The notches and their related bio-morphological bands developed at low-rate of uplifting and have been displaced by three major seismic events in the past 5 ka, the strongest of which (M∼7) occurred at about 3.2 ka. This confirms the temporary seismic gap for the Taormina Fault and strongly suggests that the seismogenic potential of this sector of Sicily needs to be re-evaluated.

The relationship between Late Quaternary deformation and volcanism of Mt. Etna (eastern Sicily): new evidence from the sedimentary substratum in the Catania region

Abstract Stratigraphical and structural analyses have been carried out on the Late Quaternary foredeep succession forming the Etnean substratum in the Catania region (eastern Sicily), in order to investigate in detail the chronology of deformation events that have accompanied a significant period of the eruptive activity of Mt. Etna, i.e. from 240 ka to the Present. This episode was characterised, at about 200 ka, by a main change of the petrochemical features of the emitted products from sub-alkaline to alkaline. This can be related to an evolving mantle diapir located beneath the volcano. The new stratigraphical and structural field data, presented in this paper, constrain the development, from 240 to 125 ka, of NW–SE-trending dextral faults associated with minor E–W- to NE–SW-oriented accommodation thrusts and NNW–SSE-trending normal faults that originated in a dominant transpressive regime. Strike-slip tectonics were active during the earlier emissions of sub-alkaline lavas (320–200 ka old) and part of the ancient alkaline products (180–100 ka old), from scattered eruptive systems which developed in local transtensive zones, distributed throughout the whole Etnean region. A major change in the mode of deformation, since 125 ka BP, was related to the propagation of a normal fault belt along the Ionian coast of the Catania region and the eastern sectors of the Etnean edifice. This process was associated with the growth of open folds that deformed the entire foredeep sequence exposed along the southern boundary of the Etnean edifice. During this period, eruptive activity concentrated along the main extensional features where steady and very efficient feeding systems originated. This resulted in a rapid increase in the volume of emitted alkaline products that gave rise to the construction of the modern stratovolcano during the last 80 ka. The collected data emphasise some main aspects of the relationship between tectonic deformation at a regional scale and volcanism in the Etna area. Firstly, the mode of deformation at the onset of Etnean volcanism seems to be inadequate to explain the emplacement at depth of a mantle diapir related to the occurrence of a hotspot, almost independent from the local crustal dynamics. On the other hand, the Late Quaternary structural assemblages recognised on the surface can be interpreted as direct effects of the Europe–Africa convergence, rather than as the products of deformation induced by the emplacement of the mantle diapir. In the different stages of Etnean evolution a direct relationship exists between the mode of deformation and the distribution as well as the capacity of the feeding systems. In particular, the amounts of emitted products in the different stages depend on the intensity of crustal stretching associated with deformation, rather than the volume of available molten material at depth. These conclusions represent a new perspective for the interpretion of the early stages and subsequent evolution of the volcanic activity of Mt. Etna. The proposed model also represents an useful tool in deciphering the relationship between the deformation path, seismicity and volcanic activity of Mt. Etna.

Geology Of The Urban Area Of Catania(Eastern Sicily)

The geology of the Catania urban area (Eastern Sicily) is the result of three combined processes related to the Late Quaternary sea-level changes, the volcanic and tectonic processes and finally to human activity. The backbone of the urban area is represented by a flight of marine terraces carved on a sedimentary substratum. This is made up of a Lower-Middle Pleistocene succession of marly clays, up to 600 m thick, upwardly evolving to some tens of metres of coastal sands and fluvial-deltaic conglomerates, referred to as the Middle Pleistocene. The unconformably overlying terraced deposits, of both coastal alluvial and marine origin, are characterized by several metres of thick sands, conglomerates and silty clays. They rest on abrasion platforms distributed at different elevations dating to the sea level high-stands between 200 and 40 kyr. These indicate a strong uplift of the area which can be explained as the effect of the deformation at the footwall of the NNW-SSE trending active normal fault system located at the south-eastern lower slope of Mt. Etna that extends offshore into the Ionian sea. The sedimentary substratum is dissected by deeply entrenched valleys filled with thick lava flows, which represent most of the rocks cropping out in the city. These consist of basaltic lavas which, flowing from NW to SE, invaded the urban area in pre-historical and historical times (e.g. A.D. 252, A.D. 1381, A.D. 1669). In the ancient part of the city the uppermost stratigraphic horizons consist of several metres thick levels of ruins derived by the destruction due to the occurrence of the 1693 earthquake.

Knickpoints as geomorphic markers of active tectonics: A case study from northeastern Sicily (southern Italy)

Unsteady base-level fall at river mouths generates knickpoints that migrate as a transient upstream through the drainage network, climbing at the same rate as long as the fluvial erosion process follows a detachment-limited stream power law. Here we demonstrate unsteady and nonuniform rock uplift using knickpoints as geomorphic markers in streams draining the eastern flank of the Peloritani Mountains (northeast Sicily), the footwall of an ∼40-km-long offshore northeast-southwest–oriented normal fault where the uplift is documented by a flight of mapped and dated Pleistocene marine terraces. Using slope-area analysis on the major streams, we project the tops of prominent knickpoints down to the coast, intersecting the marine terraces, thus providing an age for that specific knickpoint and the paleo–longitudinal profile. We model the migration rate of those dated knickpoints to locally solve for the parameters in the detachment-limited stream power law, and apply the results to model the age of other knickpoints with no clear connection to marine terraces. In summary, we demonstrate that the eastern Peloritani Mountains have been nonuniformly uplifted in an along-strike elliptical pattern, consistent with the general model for the footwall of an active normal fault. A calculation of the long-term erosion rate by the volume beneath the dated paleo–longitudinal profiles reveals a tight positive nonlinear relationship with the modeled normalized channel steepness ( k sn). Our analysis provides a method for using knickpoints as geomorphic markers in steep, rapidly eroding landscapes that commonly lack datable river terraces.

Geolithological Features and Site Response in the Town of Catania

The evaluation of seismic site response in the urban area of Catania was tackled in two test areas potentially favorable to large local amplification of ground motion. The two selected areas are located in the historical downtown and in the northern part of Catania where the presence of a fault is evident. Site response was evaluated using spectral ratios of ambient noise and numerical simulations. Such a method is particularly suitable in urban areas where the nature of the outcropping geological units is masked by city growth and anthropic intervention on the surface geology. A moderate amplification is mainly observed in recent alluvial deposits. Other soft sediments show amplitude spectral peaks smaller than those usually reported in the literature for such soils. Evidence for amplifications of site effects (frequency range 6-8 Hz) were observed in the sampling sites located on the fault, with a rapid decrease of spectral amplitude just a few tens of meters away from the discontinuity. Numerical simulations evidence the importance of knowing the geolithological features at depth greater than 20-30m. Besides this, the results strongly confirm the importance of the subsurface geological conditions in the estimate of seismic hazard at the urban scale.

The effects of a Meso-Alpine collision event on the tectono-metamorphic evolution of the Peloritani mountain belt (eastern Sicily, southern Italy)S. CATALANO AND OTHERSAlpine evolution of the Peloritani Mountains

The Peloritani Mountains, in the southern part of the Calabrian Terranes, southern Italy, have been classically interpreted as the product of the Paleogene brittle deformation of the European continental back-stop of the Neotethyan subduction complex. This reconstruction conflicts with the occurrence of an Alpine metamorphic overprint that affected portions of both the Variscan metamorphic units and part of the Mesozoic sedimentary covers of the mountain belt. New field data, integrated with petrographic, microand meso-structural analyses and stratigraphic investigation of the syn-tectonic terrigenous covers, well constrain a Paleogene collision event along the Africa–Nubia convergent margin that caused the exhumation of the Alpine metamorphic units of the Peloritani Mountains. The syn-collisional exhumation was associated with shearing along two major Africaverging crustal thrusts arising from the positive tectonic inversion of the former European palaeomargin. Early tectonic motions occurred within the mountain belts and produced the exhumation of the external portions of the edifice. Later tectonic motions occurred along the sole-thrust of the entire edifice and caused the definitive exhumation of the entire mountain belt. The whole crustal thrusting lasted for a period of c. 10 Ma, during the entire Oligocene. The definitive southwestward emplacement of the Peloritani Mountain Belt onto the Neotethyan accretionary wedge was followed by two Late Oligocene – Early Miocene NW–SE-oriented right lateral shear zones, replacing the previous crustal thrust. These two strike-slip belts are interpreted as the surface expression of the deep-seated suture zone between the colliding Africa and Europe continental crusts.

Geological map of the Tellaro River Valley (Hyblean Foreland, southeastern Sicily, Italy)

The Geological map of the Tellaro River Valley, at the 1:25.000 scale, portrays the main stratigraphic and structural features that developed in a 300 km2 wide area of the African foreland in southeastern Sicily (Hyblean Foreland). The NW-SE-oriented Tellaro River Valley marks the transition between the eastern (Siracusa Plateau) and western (Ragusa Plateau) domains of the foreland, where a post-Tortonian structural depression, here designated as Tellaro Basin, originated. The map pictures the geometry and kinematics of the border faults and the structure affecting the basin infilling. The mapped structural pattern denounces a poliphase tectonic evolution of the region, suggesting the occurrence of a major NW-SE-oriented crustal discontinuity that, being active during the different periods of the post-Tortonian evolution of the area, could play a primary role also in the present seismotectonic picture.

Late Tortonian–Quaternary tectonic evolution of central Sicily: the major role of the strike-slip deformationS. CATALANO AND OTHERSLate Tortonian–Quaternary tectonic evolution of central Sicily

We here propose a new kinematic picture of central Sicily based on the results of detailed field mapping of the region, combined with structural analyses and the interpretation of the available literature subsurface data. Our study focused on the tectonic boundary of a structural depression, the Caltanissetta Trough, which is now filled with allochthonous terrains resting on the deep-seated inverted African palaeomargin units. Our data refer to the tectonosedimentary evolution of the thrusttop basins, from Late Tortonian to Quaternary times. The study points out the occurrence of regional E–W-oriented dextral shear zones, cutting the NE-oriented trends of the thrust belt. This new evidence would confirm the major role of the E–W trend in the tectonic inversion of the external portions of the Africa palaeomargin in Sicily. Our results could contribute to a better understanding of the location in Sicily of the tectonic lineaments accommodating the hundreds of kilometres of lateral displacement, caused by the Late Miocene–Quaternary Tyrrhenian Basin opening to the north of the island.