The Culmination of an Oblique Time-Transgressive Arc Continent Collision: The Pollino Massif Between Calabria and the Southern Apennines, Italy

Abstract

The Pollino Massif is the most southeastern outcrop of the Apennine core. It marks the transition between Apenninic shortening and extension, respectively, SE and NW of the massif and is also the cusp of a southeastward plunge that characterizes the submerged Apennines. The SE limit of NE-SW extension merges with the east limit of Tyrrhenian extension in Calabria. This strategic position is expected to transition southeastward in the progressive oblique collision of the Calabrian forearc and Apulia. We test this hypothesis using published results and new field data. The time-transgressive emergence of basins on the Apennine thrust wedge is quantitatively consistent with the ESE rollback of the Calabrian arc. Specifically, a thrust-normal slip reversal on a SW dipping fault is responsible for the tectonic collapse that lead to the Mercure Basin along strike NW of the Pollino Massif and to an east-to-west reversal of drainage. This reversal is timed by an intermediate stage of trapped internal drainage with Mid-Pleistocene lacustrine sedimentation, but it may young to SE as the normal displacement on the border fault decreases gradually to SE and vanishes near the apex of the massif. On the SE side of the massif, contractional tectonics persists at least into the Mid-Pleistocene and likely later, while NE-SW extension is absent. Prominent normal faults in that area accommodate range-parallel extension and are coupled with the thrust faults. The combination of longitudinal extension with a counterclockwise rotation of hanging-wall units and thrust directivity can account for the final setting in the Apennines.