Geochemistry and petrography of Western Tethys Cretaceous sedimentary covers (Corsica and Northern Apennines): From source areas to configuration of margins

Provenance studies most commonly apply the classical approach based on petrographic\n\nmodal analysis of arenites. In this this is combined to both petrographic study on\n\nconglomerate clasts and to geochemical investigation on major and trace elements of\n\npelites. This work is aimed to: i) understand the nature of the source areas of the\n\nMesozoic sedimentary covers of the Ligure-Piemontese oceanic basin, a branch of\n\nWestern Tethys; these sedimentary successions are preserved as tectonic units in the\n\nAlpine-Apennine belt (Balagne Nappe in Alpine Corsica and Internal and External\n\nLigurian units in Northern Apennines); ii) provide further constraints to the\n\nunderstanding of the Jurassic rifting process. Petrographic and geochemical results\n\nindicate significant differences between Corsica and Internal Ligurian units against\n\nExternal Ligurian units. Petrography of pebbles from rudites and lithic fragments from\n\narenites shows that Corsica and Internal Ligurian units contain a debris of low-grade\n\nmetamorphic rocks and carbonate platform rock fragments, while the External Ligurian\n\nunits are represented by low-, medium- and high-grade metamorphic rocks; mm-sized\n\nCr-spinel probably derived from a mantle-rock source; additionally, both carbonate\n\nplatform and pelagic siliceous/carbonatic rock fragments have been found. Geochemical\n\ndata on pelites show that samples from External Ligurian units suggest a more\n\nmafic/ultramafic character: they are enriched in elements such as Cr, Co, Ni (abundant\n\nin mafic-ultramafic rocks), and the Th/Sc/Cr/V/Ni relationships show a systematic shift\n\ntowards ultramafic contribution. On the whole, petrographic and chemical data collected\n\nin this paper indicate that the source for sediments of Corsica and Internal Ligurian\n\nunits were similar, and made up by the upper part of a continental basement and its\n\ncarbonatic sedimentary cover (the Europe continental margin). On the other hand, the\n\nsedimentary cover of the External Ligurian units was supplied by a source area where a\n\ncomplete lithospheric section was exposed, from the upper mantle up to the deep sea\n\nsedimentary cover (the Adria continental margin).\n\nThese findings are useful to unravel the processes related to the opening mechanisms of\n\nthe Ligure-Piemontese oceanic basin: among the different rifting models existing, our\n\ndata support an asymmetric mechanism dominated by a west-dipping detachment fault,\n\nwith the Adria margin acting as the lower plate.