Abstract

This paper deals with the results of the geological survey carried out in the Capo Passero area, located at the southernmost corner of the Hyblean Plateau in southeastern Sicily. The aim of the survey is to gain an insight into the volcanic stratigraphy, the magmatic activity and the paleotectonic framework of the area during the Late Cretaceous. The Capo Passero area belongs to the Hyblean Plateau, a rather stable foreland region which has not experienced large rotations since Late Cretaceous time, whose northern boundary, which forms transition to the Apennine-Maghrebian mountain belt, is marked by the Gela-Catania foredeep. In the eastern offshore, the Hyblean Plateau is terminated by the Malta escarpment, a major physiographic and tectonic feature separating the continental crust of the Plateau from the Ionian oceanic crust (Ben-Avraham et alii, 1995). The Plateau consists of a thick, mainly Mesozoic-Cenozoic, carbonate succession, with interleaved volcanics whose ages range from the Late Triassic to the Quaternary. The detailed study of the Capo Passero area has enabled us to reconstruct its geologic evolution, and to gain an insight into the paleogeographic and structural framework of the area from the Late Cretaceous until the present day. The overall stratigraphic succession is represented by Upper Cretaceous, subaerial volcanic units, and by continental and marine units, ranging in age from the Maastrichtian to the Tyrrhenian (fig. 3). As a major goal of the present work, the volcanic succession was reorganized by identifying new lithostratigraphic units and modifying, when necessary, the already existing ones. Furthermore, several phases in the volcanic activity were recognized: a first, eruptive phase gave rise to subaereal lava flows; a gap in the volcanic activity, demonstrated by the occurrence of conglomerate deposits, separates them from a second eruptive phase, characterized by several subaereal lava flows, associated with the emplacement of subvolcanic bodies, both sills and dykes. The volcanic activity in the Capo Passero area ended abruptly during the Late Cretaceous, as dykes which cut through the entire volcanic succession are truncated by erosion. The marine transgression that flooded the volcanics, in response to a subsidence process, was preceded by a hiatus in volcanic activity recorded by a volcanic conglomerate and a paleosol. We provide new insights into the interpretation of the Late Cretaceous volcanism in the Hyblean Plateau, and recognise the subaerial nature of the succession cropping out in the area. Moreover, we have identified, in the Capo Passero area, the presence of a paleohigh, where post-volcanic sedimentation was condensed and, most likely, took place in a shallow marine environment. Particular attention was devoted, during the survey of the Capo Passero area, to the mapping and study of the dykes emplaced during or slightly after the extrusion of the volcanic products; their physical and geometric characteristics and their time-space distribution pattern provide clues to the tectonic history of the area. In particular, the direction of the dykes indicates that during Late Cretaceous time, the tectonic regime was characterized by a NE-SW oriented maximum horizontal principal stress, as already highlighted by Grasso et alii (1991); such a stress field was probably generated by the onset of the converging motion between Eurasia and Africa, dating back to the Late Cretaceous (Argnani, 2002). Finally, field-based identification of the recent structures in the area, has permitted confirmation of previous interpretations (Grasso et alii, 1991; Grasso et alii, 1992) of the tectonic stress regime still active in the area. In particular, all of these structures are related to a NNW-SSE orientation for SHmax, detected on the Hyblean Plateau (Ragg et alii, 1999), probably originated at the end of the convergent motion between Eurasia and Africa (Grasso et alii, 1986; Ward, 1994; Ragg et alii, 1999).

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