Relationships between the Tertiary structural evolution of the Sardinia‐Corsica‐Provençal Domain and the Northern Apennines

Abstract

Based on a revision of stratigraphic and structural data relative to the Balearic basin, the Corsica‐Sardinia massif, the Northern Tyrrhenian Sea and the Northern Apennines the following new hypothesis is proposed for the area located between the Sardinian‐Corsican‐Provençal and Northern Apennines regions: (a) convergence with subduction of oceanic crust under the Iberian plate beginning in the Late Cretaceous; (b) continental collision in the Oligocene‐Aquitanian, with development of the Northern Apennines belt and transpressive deformation in a hinterland that consisted of the Corsica‐Sardinia massif (still attached to the Iberian plate); (c) in the Burdigalian the tectonic regime changed from compressive to extensional. During this period the Corsica‐Sardinia massif migrated contemporaneously with opening of the Balearic basin, the Sardinian rift, and the Northern Tyrrhenian sea; (d) from the Burdigalian to the present, there was contemporaneous compression at the front and extension at the back of the Northern Apennines chain; both these features progressively migrated toward the east. The coeval extension and compression is attributed to lithospheric delamination toward the external part of the belt.

Magma emplacement in a thrust ramp anticline: The Gavorrano Granite (northern Apennines, Italy)

“…A bedding-parallel slaty cleavage (S 1 ) of eastward facing tight folds (F 1 ) with gently westward dipping axial planes is recognizable in the marly and shaly formations (e.g., Marne a Posidonia and Scaglia formations) and in fine-grained laminated turbidites (Macigno Formation). This first folding phase is related to the early Miocene deformation event of northern Apennines [Carmignani et al, 1995].…”

“…This belt consists of northeastward thrusted allochthonous oceanic and continental nappes derived from the Alpine Tethyan Ocean (Ligurian domain) and the Adria plate (Tuscan and Umbro-Marchigian domains). Crustal deformation began in the Eocene in the internal zone (Ligurian domain) and migrated eastward affecting the Tuscan domain in the late Oligocene -early Miocene and the foredeep deposits during the middle-late Miocene [e.g., Boccaletti et al, 1971;Carmignani et al, 1995]. Northeastward facing thrusting and folding resulted in the development of a nappe stack and polyphase deformation accompanied by anchimetamorphic to low-grade metamorphic conditions within the individual tectonic units.…”

Geological map of Tuscany (Italy)

“…Starting from the Early Miocene (Burdigalian), due to slab retreat, the Apennine compressional front migrated eastward, so the tectonic regime progressively changed from compressional to extensional: the earlier Apennine orogenic wedge was therefore affected by widespread exhumation and extensional tectonics, and Neogene rift basins formed (Carmignani et al, 1995;Jolivet et al, 1998). Extension was also accompanied by widespread Late Miocene-Quaternary magmatism deriving from mixing of crustal and mantle sources.…”

Geological map of Pliocene-Pleistocene deposits of the Ambra and Ombrone valleys (Northern Siena Basin, Tuscany, Italy)

“…The Northern Apennines tectonic pile consists of several stacked tectonic units representing different paleogeographical zones, ranging from western (internal) oceanic areas (Ligurian units) to eastern continental domains (Tuscan and Umbria-Marche units), with an intervening area of transitional crust (Subligurides units). The geological history of the Northern Apennines reflects a compressional-extensional orogenic cycle (Barchi, 2010;Brogi, 2008;Carmignani et al, 1994Carmignani et al, , 1995Elter, Giglia, Tongiorgi, & Trevisan, 1975;Liotta, Cernobori, & Nicolich, 1998), with compression dating back to the Late Cretaceous -Paleocene and following the closure of the Ligurian -Piedmont Ocean in the inner Northern Apennines (i.e. southern Tuscany).…”

“…southern Tuscany). The extensional tectonics started in the Early (Tyrrhenian area, Carmignani et al, 1995) -Middle (southern Tuscany, Brogi & Liotta, 2008) Miocene and coexisted with the compressional tectonics in the outer Northern Apennines. These extensional tectonics gave rise to detachment basins, which were successively dissected by high-angle normal faults showing listric geometries (Brogi, 2008(Brogi, , 2011Brogi, Lazzarotto, Liotta, & Ranalli, 2003;Dallmeyer & Liotta, 1998) and leading to the modern 'horst and graben' configuration ( Figure 1b).…”