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1 Istituto di Geologia dell’Università ‘Carlo Bo’ di Urbino, Campus Scientifico Località Crocicchia, 61029 Urbino, Italy perrone{at}uniurb.it
2 Departamento de Estratigrafía y Palaeontología de la Universidad de Granada, Campus de Fuentenueva, 18071 Granada, Spain
3 Dipartimento di Scienze della Terra dell’Università della Calabria, Via P. Bucci, 87030 Arcavacata di Rende, Italy
4 Dipartimento di Scienze della Terra dell’Università di Siena, Via Laterina 8, 53100 Siena, Italy
5 Dipartimento di Scienze della Terra dell’Università ‘Federico II’ di Napoli, Largo San Marcellino 10, 80138 Napoli, Italy
6 Departamento de Ciencias de la Tierra y del Medio Ambiente de la Universidad de Alicante, Campus de San Vicente, Apdo. Correos 99, 03080 Alicante, Spain
7 Dipartimento di Scienze della Terra dell’Università di Messina, Salita Sperone 31, 98166 Messina, Italy
8 Dipartimento di Scienze Geologiche dell’Università della Basilicata, 85100 Potenza, Italy
9 Département de Sciences de la Terre et d’Océanologie de l’Université ‘Abdel Maleek Essâadi’ de Tanger, Tangier, Morocco
The Anisian-Carnian Verrucano Group of the Tuscan Metamorphic Units and the Triassic-Hettangian Pseudoverrucano Formation of the homonymous unit are mainly continental redbeds occurring in Tuscany at the base of the Alpine orogenic cycle. A study carried out throughout the Apennine, Maghrebian and Betic Chains emphasized the presence in all these orogenic belts of deposits more or less coeval and similar both to the metamorphic Verrucano and to the unmetamorphosed Pseudoverrucano. Thus, the distinction of Verrucano and Pseudoverrucano successions has a palaeogeographical and geodynamic importance at the scale of the Western Mediterranean. Both successions developed during the continental rift stage of Pangaea, which led to later break-up at the edges of a future microplate, interposed between the Europe, Africa and Adria-Apulia plates, but they are characterized by different tectonometamorphic evolution. Pseudoverrucano-like deposits, devoid of Alpine metamorphism, characterize the highest tectonic units of the nappe stack and they overthrust units bearing Verrucano-like deposits. These latter show an Alpine tectonometamorphic history marked during the Miocene by intense deformation and HP/LT metamorphism (at pressures in the range of 0.8–2 GPa), followed by a retrograde phase associated with decompression, suggesting subduction and subsequent exhumation of continental crust. Intriguing palaeogeographical problems arise from the analysis of Verrucanobearing units, because the same evolution seems to characterize both units considered to belong to a realm similar to that of the north-verging Austroalpine nappe system and some units referred to the south-verging fold-thrust belt derived from the Adria-Apulia palaeomargin.
