Abstract

The Tyrrhenian Coastal Chain of northwestern Calabria is underlain by five tectono-stratigraphic units that represent large thrust sheets originating in the Tyrrhenian area and emplaced in Calabria before late Miocene time. Rocks of these nappe structures were originally Mesozoic-Tertiary platform-type carbonates, Jurassic-Cretaceous oceanic crust, and segments of a Hercynian Paleozoic microcontinent.

Calcareous-dolomitic, metavolcanic, and metasedimentary rocks of the three geometrically lowest units exhibit similar structural successions and comparable meta-morphic patterns. The first deformational event recognized in such terranes generated recumbent, isoclinal, intrafolial folds with an axial-surface schistosity or slaty cleavage virtually parallel to bedding or volcanic layering. This was accompanied by metamorphism in the blueschist and lower greenschist facies and was followed by a second main deformational phase, which formed tight, inclined to recumbent folds with various types of axial-plane crenulation cleavages. Deformation and metamorphism are interpreted to have occurred before nappe emplacement, whereas during overthrusting, previous linear features such as L2 lineations underwent reorientation toward parallelism, with the stretching direction generating a structural pattern that was radial in relation to the Calabrian arc.

The uppermost tectono-stratigraphic units made of Hercynian gneissic terranes display early structures largely obliterated by Alpine cataclasis and retrograde metamorphism. Two minor deformational phases occurred throughout the nappe pile and predated the late Miocene postorogenic transgression. The Pliocene-Quaternary arching of this foldbelt was accompanied by widespread normal faulting, which determined the present outcrop pattern.

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