RECONSTRUCTING THE EUROPEAN HYPEREXTENDED MARGIN OF THE ALPINE TETHYS IN CALABRIA, SOUTHERN ITALY

It has been long recognized that many of the ophiolites of the Alps, Corsica, and Apennines are not true fragments of oceanic crust; instead they represent fragments of hyperextended continental margin (also referred to as ocean-continent transitions). Based on the presence or absence of continental crust, the degree of extension, and trace element geochemistry, it has been possible to reconstruct transects of hyperextended African and European margins, from continental proximal to true oceanic units.

We propose that similar elements of a hyperextended margin can be recognized in geologic Calabria. These elements in order of paleogeographic (continental to oceanic) setting are: 1) The Sila Unit in the Catena Costiera exposes Variscan lower continental crust, underplated gabbros, and ultramafic rocks, separated by detachment faults. This unit represents continental crust that was thinned during Permo-Triassic pre-Tethyan rifting. 2) Timpa Pietrasasso and Timpa della Murge preserve a section of pillow basalt separated from gabbro and serpentinite by a detachment fault. The serpentinite contains fault-bounded blocks of continental crust linking the section to continental setting; this represents continental crust that was fully extended, exhuming gabbro and subcontinental mantle on the ocean floor. 3) The Monte Reventino-Gimigliano Unit consists of a package of strongly folded sediment, basalt, ophicarbonate, and serpentinite. It preserves an oceanic detachment fault separating basalt from serpentinite, without involvement of continental units.

Together these represent a transect between continental and oceanic units. In this model, the basement exposures of the Sila Unit may be analogous to the continental units of the Ivrea-Verbano and Diorite-Kinzigite Zones; Timpa Pietrasasso and Timpa della Murge are similar to the exposes serpentinite of the Platta Nappe; and the Monte Reventino-Gimigliano Unit would be comparable to distal oceanic units similar to the Chenaillet Ophiolite. Together, these may preserve the southernmost edge of the Italian sector of the rifted European margin.