Detrital Modes of the Ionian Forearc Basin Fill (Oligocene-Quaternary) Reflect the Tectonic Evolution of the Calabria-Peloritani Terrane (Southern Italy)

Abstract

Abstract During Oligocene–Neogene time, the Calabria–Peloritani terrane (CPT), a small block of continental lithosphere, rifted from the southern margin of the Eurasian continent and drifted southeastward to collide with the African continent. Along the leading edge of the CPT, a late Oligocene to Quaternary, mostly siliciclastic succession (> 2,000 meters thick) was deposited in the Ionian forearc basin. The detritus forming the succession was derived directly from the erosion of the nearby CPT, composed of Hercynian plutons intruding metasedimentary host rocks. Contrary to most modern and ancient forearc basins, penecontemporaneous volcanic detritus is virtually absent; this results from rift-related topographic barriers which separated the forearc basin from the associated volcanic arc. In spite of an overall quartzofeldspathic, continental-block provenance, the analysis of a large sandstone and conglomerate petrological dataset (228 samples) points to three discrete detrital inputs of aphanitic lithic fragments in (i) late Oligocene–early Miocene, (ii) late Messinian, and (iii) Quaternary times. These petrological variations can be linked to independently determined tectonic events in the western Mediterranean, which likely modified the lithologic composition of the sediment source terranes. Input (i) documents the progressive, widespread unroofing of the continental basement of the southern European margin, when northwestward subduction of the remnants of the Ligurian ocean began. Input (ii) is related to widespread intra-Messinian tectonism possibly due to out-of-sequence thrusting induced by isostatic readjustments of the perimediterranean orogenic wedges following the Messinian drawdown. Input (iii) reflects the rapid vertical uplift experienced by the CPT since mid-Pleistocene time, possibly the result of slab detachment along the Ionian subduction zone. This study indicates that detailed statistical analysis of the detrital modes of ancient terrigenous deposits can be used to identify the tectonic events affecting somewhat petrologically monotonous sediment source areas within small lithospheric terranes.