GNGTS 2014 - Atti del 33° Convegno Nazionale

GNGTS 2014 S essione 1.1 85 Quaternary marine terraces and fault activity in the northern sector of the Messina Straits (southern Italy C. Monaco, G. Barreca, A. Di Stefano, G. Ristuccia Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Sezione di Scienze della Terra, Università di Catania, Italy Introduction. Starting from Late Pliocene, and more markedly in the Quaternary, concurrently with back-arc extension in the Tyrrhenian Sea, the inner side of the Calabrian Arc, has experienced extensional deformation accommodated by normal faulting (Ghisetti, 1984, 1992; Tortorici et al ., 1995; Monaco and Tortorici, 2000; Jacques et al. , 2001). A prominent normal fault belt runs more or less continuously along the Tyrrhenian side of Calabrian, as far as the Messina Straits area. Extension along this fault system has a WNW-ESE azimuth, as documented by structural, seismological (CMT and RCMT catalogues) and GNSS velocity field (D’Agostino and Selvaggi, 2004; Goes et al ., 2004; Mattia et al ., 2009; D’Agostino et al ., 2011; Palano et al ., 2012) investigations. Since the Middle Pleistocene, the Calabrian Arc has been also affected by strong uplift, which caused to the development of spectacular flights of marine terraces along the coast and, on land, a deep entrenchment of rivers with the consequent deposition of alluvial and/or transitional coarse grained sediments along the major depressions on top of pelagic sequences (����� Dumas et al ., 1982; Ghisetti, 1992; Valensise and Pantosti, 1992; Westaway, 1993; Miyauchi et al ., 1994��). The Late Quaternary tectonics of the Calabrian Arc result from the interplay of distinct geodynamic processes (Westaway, 1993; Palano et al ., 2012). This is reflected by the existence, within the deformation profile of the flights of coastal terraces, of both a long- and a short- wavelength signal, the former related to lower- or sub-crustal processes and the second arising from upper crustal displacements. According to Westaway (1993), 1.7 mm/yr of post-Middle Pleistocene uplift of southern Calabria is subdivided into 1 mm/yr regional (or deep) processes and the residual to distributed displacement on major faults, and mostly results in footwall uplift. In order to determine the uplift rates and the late Quaternary contribution of the outcropping normal faults, a new mapping of the terraced deposits and surfaces, accompanied by measurement of inner-edge elevation, has been carried out on both sides of the northern sector of the Straits. The study is based principally on detailed field mapping on 1:10,000 scale digital topographic maps integrated with analysis of 1:33,000 and 1:10,000 scales aerial photographs and LANDSAT satellite images of the terrace surfaces. Their relative inner and outer edges have been mapped over the whole area with an error margin in the elevation of ±5 m. However, this margin basically depends on erosion and depositional processes following the emergence of the terraces and it is negligible in estimating the long-term Quaternary uplift rates involving time spans of tens to hundreds of thousands of years. This implies that the elevations above sea level (a.s.l.) of the paleo-shorelines reported in this work are to be considered as mean values. The occurrence of a flight of marine terraces represents the result of the interaction between long-term tectonic uplift and Quaternary cyclic sea-level changes (Lajoie, 1986; Bosi et al ., 1996) which are represented in the global eustatic curve derived from the Oxygen Isotope Time (OIT) scale. This curve (Waelbroeck et al ., 2002 and references therein) shows a cyclic trend characterized by peaks corresponding to distinct marine interglacial high-stands, represented by the odd-numbered Marine Isotope Stages (MIS) and marine glacial low-stands, indicated by the even-numbered MIS. ��� ������ ����� ��� ��������� �� ����������� ��� ��������� ����� �� ���� The uplift rates are estimated by subtracting the altimetry value of each terrace from the sea level of the assigned Marine Isotopic Stage (MIS) and then dividing this value by the age assigned to the terrace through literature data (see below). The Calabrian side. Along the Calabrian side, among Villa S. Giovanni and Piano di Matiniti, a complete sequence of ten Late-Quaternary fluvial-coastal terraces (Fig. 1) has been recognized at elevations ranging from 40 to 520 m a.s.l. (Fig. 2). The terraced deposits are