Chronostratigraphy and paleomagnetism of Oligo-Miocene deposits of Corsica (France) : geodynamic implications for the liguro-provençal basin spreading

Abstract

In a context of convergence between Africa and Europe, the western Mediterranean domain is characterized by the opening of the Liguro-Provençal ocean in the early Miocene and of the Tyrrhenian Sea since the middle Miocene. These openings are preceded by an Oligocene rifting episod. New biostratigraphic, geochronologic and paleomagnetic data allow to propose an integrated stratigraphy sketch for the Oligo-Miocene period in Corsica. The continental syn-rift deposits, in the region of Ajaccio, have been dated as late Chattian from the presence of a mammal, Pomelomeryx boulangeri. Their paleomagnetic study indicates an anticlockwise rotation of 44 ±4° with regard to the stable Europe. The early Miocene succession was deposited on a contrasted topography inherited from the Oligocene glyptogenesis period. The lowermost Miocene deposits are represented by 4 pyroclastic flow deposits in southern Corsica. New 40Ar-39Ar datings on plagioclase concentrates give ages between 21.3 and 20.6 Ma (late Aquitanian). Paleomagnetic directions indicates that the rotation of Corsica had probably begun at this time. The Miocene marine sediments of the Bonifacio basin are divided in two formations. At the base, the Cala di Labra formation, that comprises 3 reef formations in coastal onlap (R1, R2, R3), is attributable to the Globigerinoides trilobus zone. In the environment of R1, miogypsin population includes mainly Miogypsina intermedia with a few M. globulina and M. cushmani. The absence of the less evolved forms (10 < V < 35) let us suppose that at least the lower Burdigalian is absent at Bonifacio because the region was emerged. R2 reef has a similar population (42 < V < 70), which suggests a rather short interval of time between the two stages of reef construction. On the other hand the R3 population contains only evolved forms (M. mediterranea) suggesting a late Burdigalian age. The end of the sedimentary succession (Bonifacio formation) is essentially represented by a pile of hydraulic dunes. The absence of Orbulina shows that this upper unit is older than late Langhian (biozone N9). Miocene sediments from Saint-Florent are divided into 3 marine formations bracketed by two continental ones. At the base, the continental formation of Fium’Albinu (equivalent to the Cala di Labra formation) is surmounted by the Torra formation attributed to Late Burdigalian based on the presence of G. trilobus and G. bisphericus. The Sant’Angelo formation (equivalent to the Bonifacio formation) developed from latest Burdigalian to late Langhian. The Farinole formation represents early Serravallian (base of the Globoquadrina altispira altispira zone). Despite the large number of studied sites in this study and others, the only reliable Oligo-Miocene paleomagnetic results in Corsica are the following ones : – the Vazzio formation indicates a rotation of 44 ± 4° after the late Oligocene, – the southern volcanic flows show that the rotation was in progress around 20.7 Ma (late Aquitanian), – the Fium’Albinu formation indicates a rotation of 30 ± 12° after early Burdigalian, – site B from Vigliotti and Kent [1990] gives a rotation of about 11 ± 5° after early Langhian. Our paleomagnetic data, together with the existing ones, associated to the biostratigraphic and geochronologic ages show that the opening of the Ligurian basin coincides with an anticlockwise rotation of 45° of Corsica, which begins between 23 and 21 Ma and ends around 15 Ma. This is in agreement with the idea of Sardinia and Corsica rotating as a single almost rigid block during Miocene times.

Two‐ and three‐dimensional thermal modeling of a low‐angle detachment: Exhumation history of the Simplon Fault Zone, central Alps

“…One possible controlling process for the onset and later decrease of orogen‐parallel extension in the central Alps could be the opening and rotation of the Algero‐Provencal basin (western Mediterranean sea). The rotation of Corsica has been established between 23 and 15 Ma [ Ferrandini et al , 2003] and 16 Ma corresponds to a period of transition, with the shift of the active extension from the western to the central Mediterranean sea, involving a major change in the general stress field [ Carminati et al , 1998]. As also proposed by Champagnac et al [2006] and Sue et al [2007], the opening of the Algero‐Provencal basin could provide a free boundary, which, together with the indentation and anticlockwise rotation of the Adria microplate, could be responsible for the onset of orogen‐parallel extension in the central Alps.…”

Residence time, mineralization processes and groundwater origin within a carbonate coastal aquifer with a thick unsaturated zone

“…Several stratigraphic logs were defined in the area (Ferrandini et al, 2003;Orsini et al, 2010;Reynaud et al, 2012), showing three major sedimentary formations with little differences in the deposit sequences. In this paper, we refer to the stratigraphic log of Reynaud et al (2012).…”

Seep-carbonates in a thrust-related anticline at the leading edge of an orogenic wedge: The case of the middle–late Miocene Salsomaggiore Ridge (Northern Apennines, Italy)

“…A) passes across the Salsomaggiore Structure (SS) and the Cortemaggiore anticline (CA). Ferrandini et al, 2003). At present, the Apenninic orogenic wedge is framed by two superposed structural levels, which, because of different amounts of shortening and exumation, are better preserved in tectonic windows, one of which is the Salsomaggiore Structure ( Fig.…”