The architecture of an incipient oceanic basin: a tentative reconstruction of the Jurassic Liguria-Piemonte basin along the Northern Apennines–Alpine Corsica transect

Abstract

In this paper, a scenario for the early evolution of the Jurassic oceanic Liguria-Piemonte basin is sketched. For this purpose, four selected examples of ophiolite sequences from the Northern Apennines and Corsica are described and analyzed. In the External Ligurian units (Northern Apennines), the ocean-continent transition of the Adria plate was characterized by a basement made up of subcontinental mantle and lower continental crust, covered by extensional allochthons of upper crust. Both, the basement rocks and the extensional allochthons are cut by basaltic dikes and covered by basalts and pelagic deposits. The conjugate ocean-continent transition of the Corsica margin, represented by the Balagne nappe (Corsica), was composed of mantle peridotites and gabbros covered by basaltic flows and minor breccias, that in addition include continent-derived clasts. By contrast, the innermost (i.e., closest to the ocean) preserved area observed in the Internal Ligurian (Northern Apennines) and Inzecca (Corsica) units consists of former morphological highs of mantle peridotites and gabbros, bordered by small basins where the basement is covered by a volcano-sedimentary complex, characterized by ophiolitic breccias and cherts interlayered with basaltic flows. The overall picture resulting from our reconstructions suggests an asymmetric architecture for the Liguria-Piemonte basin with a central area bounded by two different transition zones toward the continental margins. This architecture can be interpreted as the result of a rifting process whose development includes a final stage characterized by passive, asymmetric extension of the lithosphere along an east-dipping detachment fault system.

Tectonic significance of different block-in-matrix structures in exhumed convergent plate margins: examples from oceanic and continental HP rocks in Inner Western Alps (northwest Italy)

“…Similar breccias have, in fact, been described in the Ligurian Units of the Northern Apennines and interpreted as the product of submarine erosion of peridotite and gabbro exposed on the seafloor, originated during the opening of the Ligurian Ocean (i.e. the Tethyan Ocean) in the Late Jurassic-Early Cretaceous (Decandia and Elter 1972;Barrett and Spooner 1977;Bortolotti et al 2001;Marroni and Pandolfi 2007). Similar breccias have also been sampled along the slow-spreading mid-ocean ridge/ transform system (e.g.…”

Sulfur geochemistry of peridotite-hosted hydrothermal systems: Comparing the Ligurian ophiolites with oceanic serpentinites

“…Upwelling of the asthenosphere led to thinning of the lithosphere and intrusion of gabbroic melts due to decompression-induced partial melting. Continuous extension of the lithosphere and the formation of a non-volcanic, passive margin dominated the final stages of rifting, which was accompanied by the development of detachment faults (Marroni and Pandolfi, 2007). These faults caused exhumation of large amounts of subcontinental mantle, eventually leading to the exposure of mantle rocks on the ocean floor and to extensive serpentinization in the Late Jurassic (Piccardo et al, 1994(Piccardo et al, , 2009Rampone and Piccardo, 2000;.…”

Recognizing remnants of magma-poor rifted margins in high-pressure orogenic belts: The Alpine case study

“…Dal Piaz, 1974;Beccaluva et al, 1984;Rossi et al, 1994;Lahondère, 1996;Marroni and Pandolfi, 2007;Molli, 2008). The widespread occurrence of siliciclastic deposits in close association with supra-ophiolitic sediments (e.g.…”