In Sicily, the progressive imbrication of the Apenninic thrust belt
above the Pelagian-African Foreland is traced by the southward migration
of marine basins that were progressively shortened during the late
Miocene-Pleistocene. The outermost and youngest thrust sheet (Gela
Nappe) displays a peculiar shortening, with Messinian to early Pliocene
E-W folds refolded in the late Pliocene–early Pleistocene by approximately
N-S folds (subparallel to the transport direction of the thrust sheets).
This structural interference is documented in south Sicily within
localized belts of refolding spaced ~5–8 km apart. The significance
of this fold interference pattern is highlighted by our analysis of
the offshore seismic reflection line M23A (CROP Mare Project) that
intersects the Gela Nappe along a trace suborthogonal to the thrust
transport direction. Migration and depth conversion of the line reveal
multiple imbrications and draping of the allochthonous units above
structural highs of the foreland, delimited by inherited N-S faults.
The largest faults bound mid-late Miocene extensional basins but were
reactivated in compression during the late Pliocene–early Pleistocene,
causing (1) superposed folding along discordant N-S structural trends,
(2) compressional extrusion of the whole wedge of the Gela Nappe,
and (3) offset of its sole thrust. The reactivation of faults subparallel
to the transport direction accommodates differential flexure of the
rigid foreland beneath the Apenninic wedge, and these late stage deformations
in the foreland are responsible for the superposition of E-W finite
shortening onto N-S shortening.