Plio-Quaternary tectono-stratigraphic evolution of the Paola fore-arc basin (western Calabria continental margin): Insight from high-resolution seismic reflection data

Abstract

We reconstructed the most relevant geologic features across the Paola Basin (offshore western Calabria) and its Pliocene to Recent sedimentary and tectonic evolution using a grid of seismic profiles acquired within the frame of the EU-SINBUS project in the 1995. We used seismostratigraphic analysis to outline the seismic units. The Messinian horizon, as well as regional unconformities recognized in the Plio-Pleistocene geological record of the basins developed within or adjacent to the Calabrian Arc, played a key role to assign ages to the sedimentary units. We identified five seismic units on seismic lines, based on the internal configuration and seismic-stratigraphic character of reflectors (amplitude, reflection continuity, external shape, and frequency). Moving from the Calabria coast-line to the west, the Paola Basin can be partitioned into two sectors characterized by different Plio-Quaternary tectonic deformation separated by a NNW-SSE elongated area that coincides with the basin depocenter. Plio-Quaternary high-angle, reverse faults are widely spread over the western sector of the basin that correspond to an arcuate ridge separating the basin from the Marsili abyssal plain. A high-angle, NNE-trending, normal fault system, on the contrary, developed on the south-west tip of the basin only, where the fault offset deforms the Messinian horizon of ca. 500 m. Data suggest that limited vertical slip occurs along reverse faults detected at the border and inside the sedimentary infilling of the Paola Basin, reaching thickness of more than 3.8s two way travel time. A series of acoustically opaque cone-shaped zones on the western flanks of the basin interrupts the continuity of the sequences. These zones, 2 km-wide, propagate to the surface intruding the lower sequence and folding both the sedimentary layering of the upper sequence and the sea-floor. The features correspond to intruded and erupted mud diapirs that pierce the entire sequence because of the occurrence of overpressured fluids escaping to the surface via any permeable horizons and tectonic structures. The sequences reflection pattern can be interpreted as the result of the infilling of thrust-top basin related to a prograding system located between a growth rampanticline to the west and a culmination of basement-thrust sheets to the East, activated in the context of the Tyrrhenian Sea opening and lateral escape of the Calabrian block. Thus, mechanisms for subsidence affecting this area since the Late Neogene significantly differ from extensional and/or compressional processes responsible for formation of basins along the Sardinia and northern Sicily continental margins. Taking into account the pattern of the sedimentary infilling, the basin shape and its position in the regional context, we propose that the Paola Basin developed near the northern edge of the Ionian slab where tearing of the lithosphere is expected.