Analisi strutturale ed osservazioni morfostratigrafiche mel bacino del Mercure (confine Calabro-Lucano)

Abstract

Geomorphological features and recent brittle deformations of the Mercure Basin at the Calabria-Lucania boundary (Southern Apennines) have been surveyed. Orientation measurements have been performed for both the Mesozoic carbonate bedrock and the Quaternary lacustrine and slope deposits. Two different tectonic stages responsible for the genesis and the evolution of the basin have been identified, predating the deposition of the Middle-Upper Pleistocene lacustrine sediments. If the sedimentary sequences of the Mercure, S. Arcangelo and Castrovillari basins are corralated to ono another the above mentioned tectonic events are to be ascribed to the Emilian and Sicilian stages (Lower Pleistocene). The first tectonic stage occurred in a transcurrent regime related to the kinematics of the Pollino left-lateral strike-slip N120° trending fault zone. It created a transversal half-graben which breaks off the lateral continuity of the chain. The second stage took place in an extensional strain field characterized by a counter-apenninic extension axis rotating clockwise through the time. This stage occurred between the end of the Lower Pleistocene and the beginning of the Middle Pleistocene. It set the conditions for the development of an endoreic basin, because of the uplift of the N110°-120° trending La Fagosa Ridge. Both the tectonic stages are to be interpreted as the consequence of a continuous reorganization of the local stress fields due to a rotational field acting along the Pollino Fault System. A weak tectonic event is also recorded by the lacustrine deposits. The presence of N150° ± 20° trending joint sets, besides N-S and E-W trending fault systems with little normal offset is interpreted as the last effect of the extension axis clockwise rotation. Clays and marls of the lake sequences are affected by synsedimentary listric normal faults as well, which testify the persistence of an extensional tectonic regime during Middle-Upper Pleistocene times.