Geochronology of terraced coastal deposits in Calabria and eastern Sicily: tectonic implications
Calabrian Arc and Eastern Sicily (Southern Italy) are characterized by flights of coastal terraces occurring in various geological domains. These features are formed by interaction between the glacio-eustatic sea level changes and Late Quaternary uplift. Thus, by combining ages and elevations of inner edges with the OIT stages of high sea-level stands, it is possible to accurately evaluate the uplift rates of coastal areas and to discriminate, where possible, the regional and local components of uplift. At this purpose, in this thesis the Optically Stimulated Luminescence (OSL) method has been used, mainly for its applicability to the detrital minerals of the terraced sediment (i.e. quartz) and for its accuracy. The research project is based on interdisciplinary study that involved the PH3DRA (Physics for Dating Diagnostic Dosimetry Research and Applications) laboratories of the Department of Physics and Astronomy of the Catania University, where preparation of geological samples, measurements and analysis of results were carried out, in order to optimize the dating procedure and to obtain OSL age of samples collected from the studied terraced deposits. For each sites the structural and geomorphological issues have been dealt with and then samples of sands have been collected from the studied areas. Four key sites, characterized by different tectonic setting, have been chosen: Amendolara (north-eastern Calabria), Capo Vaticano peninsula (western Calabria), Sant Agata di Militello (north-eastern Sicily), Terreforti Hills (eastern Sicily). For the first site, the OSL dating methodology on quartz grains failed. Quaternary terraced deposits outcropping on the Capo Vaticano peninsula have been investigated in order to obtain new chronological estimates. OSL age determinations correlated with geological and morphological evidences have provided new constraints for correlating the distinct orders of marine terraces with the last seven interglacial stages of the eustatic curve. This correlation indicates that in the Middle-Late Pleistocene this portion of the southern Calabrian Arc was affected by a vigorous uplift characterized by rates up to ~2 mm/yr, accompanied by faulting and tilting of the peninsula towards the northeast. Along the coastal sector of Sant Agata di Militello the geomorphological survey and the analysis of stereo-pairs of aerial photographs allowed to recognize at least five main orders of well-preserved Quaternary surfaces and relative deposits. They are mostly located on the hanging-wall and on the footwall of the Pleistocene northwest-dipping Capo d Orlando normal fault, which controlled the geomorphological evolution of the coastal area. In order to better define the whole terrace chronology, deposit samples were analysed by OSL methodology, a conventional single-aliquot regenerative-dose (SAR) protocol used with sand-sized quartz. New datings, together with the detailed morphostructural analysis, allow to relate the 2nd and 4th order terraces to MIS 5.5 and 8.5, respectively, and to reconstruct the tectonic evolution of this coastal area, constraining the activity of the Capo d Orlando fault. Coastal-alluvial terraces outcropping in the area between Mt. Etna volcano and the Catania Plain, known as the Terreforti Hills , at the front of the Sicilian fold and thrust system, were analyzed. The obtained OSL ages were consistent with the normal evolutionary model of a terraced sequence, moving from the highest to the lowest elevations and the new data allowed us to determine a mean uplift rate of 1.2 mm/yr during the last 330 ka, mostly related to regional uplift processes coeval to Quaternary sea-level changes. Moreover, the two highest order terraces are folded, forming the large Terreforti anticline. According to our analysis, this anticline represent a thrust propagation fold developed at the front of the Sicilian chain between 236 and 197 ka ago.
Coastal terraces, OSL dating, Pleistocene, Calabrian Arc, Eastern Sicily
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