FISSION-TRACK ANALYSIS AND PROVENANCE STUDIES IN CALABRIAN ARC SEDIMENTARY-ROCKS, SOUTHERN ITALY

Fission track analysis has been applied to the Stilo-Capo d'Orlando Fo rmation of southern Italy. This is a terrigenous syn-orogenic sediment ary deposit of Oligo-Miocene age that accumulated during a phase of ac celerated denudation that affected the nearby crystalline basement roc ks of the Calabrian Arc between c. 30 and 15 Ma. Seven conglomerate cl asts and two sandstone samples from the base of the formation have pro duced eight apatite fission-track ages, nine zircon fission-track ages and six apatite confined-track length analyses. The zircon fission-tr ack data confirm that detritus was derived from local Hercynian igneou s and metamorphic rocks. In addition, apatite fission-track results fr om the two sandstone samples reveal that the basal part of the Stilo-C apo d'Orlando Formation was exposed to maximum palaeotemperatures in e xcess of 70-degrees-C after deposition. Despite this, apatite fission track ages much older than those obtained from the in situ crystalline basement source rocks of the Calabrian Arc have been acquired. These ages are interpreted as being derived from 'lost cover', that is, rock s originating from the structurally highest levels of the basement com plex that have now been completely removed by erosion. Fission track a nalysis demonstrates that erosion, in addition to previously identifie d extensional tectonism, was a major factor during accelerated denudat ion of the Calabrian Arc basement rocks during the late Oligocene and early Miocene.