Eocene rotation of Sardinia, and the paleogeography of the western Mediterranean region

Pressure–temperature–deformation–time of the ductile Alpine shearing in Corsica: From orogenic construction to collapse

“…Finally, our study demonstrates that the extensional collapse of the Alpine orogen in Corsica culminated 7-8 Ma after the last top-tothe-W compressional shear increments along the ETSZ, concurrently with the early Miocene transition from rifting to drifting in the LiguroProvençal basin (Gattacceca et al, 2007;Speranza et al, 2002). The tectono-metamorphic and Rb-Sr geochronological data presented in this study correspond to a time window (early Oligocene-early Miocene) central in reconstruction of the Alps-Apennine relationships, with different geodynamic scenarios proposed so far (e.g., Advokaat et al, 2014;Argnani, 2012;Carminati et al, 2012;Doglioni et al, 1998;Dumont et al, 2011;Faccenna et al, 2001Faccenna et al, , 2004Handy et al, 2010;Lacombe and Jolivet, 2005;Malusà et al, 2011;Molli and Malavieille, 2010;Turco et al, 2012;van Hinsbergen et al, 2014;Vignaroli et al, 2008). On this regard, integration of the results presented in this study with the paleomagnetic evidence presented in Advokaat et al (2014) indicate that the major stages of Alpine orogenic construction and extensional reworking in Corsica occurred concurrently with two major rotation episodes of the Sardinia-Corsica block with respect to Eurasia, during Eocene and early Miocene, respectively.…”

“…This evidence suggests a scenario of late increments of (highpressure) compressional shear during the early Oligocene and, therefore, poses the issue on significance of the early Eocene ages derived from TIMS U-Pb dating of the T5c Acm-Rt-bearing sample from the ETSZ (Maggi et al, 2012). It is worth noting, however, that a prolonged early Eocene to early Oligocene activity of the ETSZ as a compressional shear zone is compatible with post-early Eocene to pre-Oligocene (~50-30 Ma)~45°counterclockwise rotation of Sardinia-Corsica relative to Eurasia (Advokaat et al, 2014). The Eocene rotation of Sardinia-Corsica was synchronous with and likely responsible for documented N-S shortening in the Provence (Lacombe and Jolivet, 2005) and the incorporation of the Briançonnais continental domain, likely connected to Corsica, into the western Alps (Advokaat et al, 2014).…”

“…It is worth noting, however, that a prolonged early Eocene to early Oligocene activity of the ETSZ as a compressional shear zone is compatible with post-early Eocene to pre-Oligocene (~50-30 Ma)~45°counterclockwise rotation of Sardinia-Corsica relative to Eurasia (Advokaat et al, 2014). The Eocene rotation of Sardinia-Corsica was synchronous with and likely responsible for documented N-S shortening in the Provence (Lacombe and Jolivet, 2005) and the incorporation of the Briançonnais continental domain, likely connected to Corsica, into the western Alps (Advokaat et al, 2014). Indeed, an early Eocene age for the ETSZ is in line with the maximum 40 Ar/ 39 Ar phengite ages presented by Brunet et al (2000) for the ETSZ and, more in general, with the Eocene involvement of the European continental margin units (Briançonnais Domain) in the subduction processes of the internal zones of the Alpine chain (Berger and Bousquet, 2008;Handy et al, 2010;Villa et al, 2014).…”

“…The tectono-metamorphic and Rb-Sr geochronological data presented in this study correspond to a time window (early Oligocene-early Miocene) central in reconstruction of the Alps-Apennine relationships, with different geodynamic scenarios proposed so far (e.g., Advokaat et al, 2014;Argnani, 2012;Carminati et al, 2012;Doglioni et al, 1998;Dumont et al, 2011;Faccenna et al, 2001Faccenna et al, , 2004Handy et al, 2010;Lacombe and Jolivet, 2005;Malusà et al, 2011;Molli and Malavieille, 2010;Turco et al, 2012;van Hinsbergen et al, 2014;Vignaroli et al, 2008). On this regard, integration of the results presented in this study with the paleomagnetic evidence presented in Advokaat et al (2014) indicate that the major stages of Alpine orogenic construction and extensional reworking in Corsica occurred concurrently with two major rotation episodes of the Sardinia-Corsica block with respect to Eurasia, during Eocene and early Miocene, respectively. This evidence supports a paleotectonic configuration that places (i) development of the Alpine Corsica orogenic edifice during underthrusting of the European margin (Briançonnais realm) in the frame of the Alpine (east-dipping) subduction during the Eocene, and (ii) the extensional collapse of the orogenic edifice as a consequence of the back-arc extensional regime generated in the upper-plate of the Apennine (west-dipping) subduction.…”

“…The Alpine evolution occurred concurrently with major rigid block rotations that affected the Sardinia-Corsica block relative to Eurasia, first during Eocene times, prior to the Oligocene (at~30 Ma) onset of extension in the Liguro-Provençal back-arc basin (Advokaat et al, 2014) and then during its rifting/drifting history in Miocene times (Gattacceca et al, 2007;Speranza et al, 2002). The kinematics of the two tectonic events in Alpine Corsica is characterized by nearly sub-parallel but opposite sense of tectonic transports, with early, dominantly top-to-the-W compressional (equilibrated under HP/LT, blueschist-to-eclogite facies peak metamorphic conditions) and late top-to-the-E extensional (equilibrated under retrogressive greenschist facies metamorphic conditions) shear senses, respectively (Daniel et al, 1996;Gibbons and Horak, 1984;Jolivet et al, 1990Jolivet et al, , 1998Maggi et al, 2012Maggi et al, , 2014Mattauer et al, 1981;Molli et al, 2006) (Figs.…”