Giorgio De Guidi

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 Morphotectonic map of Mt. Etna

The Morphotectonic Map of Mt. Etna (see attached table) is based on detailed field survey of morphologic and structural features outcropping on the volcanic edifice, supported by detailed analysis of orthophotos, stereo-pair photographs and satellite images. It helps to define more completely and accurately than previously done the structural network of active features that characterizes the volcanic edifice, and the relationships between faulting, fissuring and dyke swarms. Morpho-structural data are drawn on a schematic geological map where the main sedimentary and volcanic units have been reported. Morphotectonic analysis shows that Mt. Etna volcano exhibits active extensional features represented by normal faults and eruptive fissures which are related to shallow low-energy seismicity. These accommodate WNW-ESE striking extension, deduced from structural analysis and seismological data, related to incipient rifting processes at regional scale. The fault segments generally control the present topography and show steep escarpments with very young, mostly Late Pleistocene to Holocene, morphology. The most important structures are located along the eastern base of the volcano (Timpe fault system), where NNW-SSE striking normal faults with dextral-oblique component of motion represent the northern end of the Malta Escarpment system. In the north-eastern slope of the volcano these fault system swings to a NE trend which it keeps northwards along the Ionian Coast to Taormina and as far as Messina Straits. The major fissural eruptions occur along well defined, feeder-dykes and spatter cones belts that cut the upper slopes of the volcano, on the footwall of the Timpe fault system. They form NE trending pure extensional swarms along the NE sector of the volcano and en-echelon systems of N-S to NNE-SSW oriented fractures along NNW-SSE trending oblique-dextral shear-zones in the southern and south-eastern slopes. Such summital eruptive fissuring appears to result from the same ESE-striking regional extensional stress that drives active faulting at the base of the volcano suggesting a common tectonic origin

Geological map of the Corvillo and Mandre Basins (Caltanissetta Basin, Central Sicily): Explanatory notes

In Sicily, the imbrication of the Apenninic thrust belt above the African foreland determined the progressive southward migration of marine basins that were shortened from the Middle Miocene until the Pleistocene. The area studied in detail is located in the Caltanissetta Basin, which was in fact, during Neogene times, a series of thrust-top basins (e.g. Corvillo and Mandre). The relationships between Neogene sedimentation and the synchronous development of fold and thrust structures are recorded by unconformities, lap relationships of strata, hiatuses. The stratigraphy of the substratum is dominated by varicoloured clays and siliciclastic deposits of Cretaceous-Early Miocene age. The thrust-top basin stratigraphy is represented by Tortonian siliciclastic deposits and evaporitic deposits, which are the product of the Messinian lowstand. The Early Pliocene flooding was responsible of deposition of chalks and marls and a later regional uplift produced a regression, during Late Pliocene times, with deposition of marls and sandstones. Compressional deformation acted continuously from Middle Miocene until, at least, Middle Pliocene, amplifying the pre-existing structures and creating differing styles of deformation depending on the lithologies involved.

Landslide Processes and Susceptibility Mapping in NE Sicily, Italy

Many destructive debris flows hit several villages in the Peloritani Mountains area (Sicily, Italy) in October 2009. The collection of several types of spatial data, together with the landslides inventory, allowed the assessment of the landslide susceptibility by the application of two different bivariate techniques.