The two-stage Aegean extension, from localized to distributed, a result of slab rollback acceleration

Abstract

Back-arc extension in the Aegean, which was driven by slab rollback since 45 Ma, is described here for the first time in two stages. From Middle Eocene to Middle Miocene, deformation was localized leading to (i) the exhumation of high-pressure metamorphic rocks to crustal depths, (ii) the exhumation of high-temperature metamorphic rocks in core complexes, and (iii) the deposition of sedimentary basins. Since Middle Miocene, extension distributed over the whole Aegean domain controlled the deposition of onshore and offshore Neogene sedimentary basins. We reconstructed this two-stage evolution in 3D and four steps at Aegean scale by using available ages of metamorphic and sedimentary processes, geometry, and kinematics of ductile deformation, paleomagnetic data, and available tomographic models. The restoration model shows that the rate of trench retreat was around 0.6 cm/year during the first 30 My and then accelerated up to 3.2 cm/year during the last 15 My. The sharp transition observed in the mode of extension, localized versus distributed, in Middle Miocene correlates with the acceleration of trench retreat and is likely a consequence of the Hellenic slab tearing documented by mantle tomography. The development of large dextral northeast–southwest strike-slip faults, since Middle Miocene, is illustrated by the 450 km long fault zone, offshore from Myrthes to Ikaria and onshore from Izmir to Balikeshir, in Western Anatolia. Therefore, the interaction between the Hellenic trench retreat and the westward displacement of Anatolia started in Middle Miocene, almost 10 Ma before the propagation of the North Anatolian Fault in the North Aegean

Polycyclic alpine orogeny in the Rhodope metamorphic complex: the record in migmatites from the Nestos shear zone (N. Greece)

“…For the purpose of this paper, the important point is that, ∼100 Myr after the first anatectic event (a time laps that encompasses the period from ∼115 to ∼70 Ma without geochronological record on the regional scale, see Sect. 2.1), the second anatectic event did not occur in a context of delamination-driven extension (Jolivet and Brun, 2010;Burg, 2011;Marchev et al, 2013;Brun et al, 2016) but in a context of crustal-scale thrusting. This attests for polycyclic orogeny in the RMC during Alpine times.…”

“…As for the age of the shear zone, the inference that is was active during the Eocene (Barr et al, 1999) and as late as 37 Ma (Dinter, 1998;Krohe and Mposkos, 2002) relies mainly on a set of K-Ar hornblende ages between 37 and 47 Ma (Liati, 1986). Many authors implicitly consider that these K-Ar data yield only a minimum possible age of shearing, so that the NSZ can be accepted as a major SW-vergent thrust of much older age (Mesozoic or Mesozoic-Paleocene; Ricou et al, 1998;Papanikolaou and Kranis, 2004;Krenn et al, 2010;Burg, 2011;Schenker et al, 2014;Kydonakis et al, 2016;Brun et al, 2016). With regard to the age and tectonic significance of the NSZ, three studies should be considered more closely.…”

“…17). Consequently, the picture of the NSZ representing a Mesozoic or Mesozoic-Paleocene thrust (Ricou et al, 1998;Papanikolaou and Kranis, 2004;Krenn et al, 2010;Burg, 2011;Schenker et al, 2014;Brun et al, 2016) must be abandoned, an inference also supported by the complete lack of Mesozoic-Paleocene ages in the geochronological record of the PU and the UPU.…”

Tsunamigenic potential of a Holocene submarine landslide along the North Anatolian Fault (North Aegean Sea, off Thasos Island): insights from numerical modeling

“…The Aegean domain used to be a mountain belt (Hellenides) during the Early Cenozoic, which collapsed since the Late Eocene-Early Oligocene, in close relationship with the southwards retreat of the Hellenic trench (Jolivet and Faccenna, 2000;Jolivet and Brun, 2010;Jolivet et al, 2013;Brun et al, 2016). Since the Late Miocene, strike-slip tectonics along the North Anatolian Fault system accommodates the lateral escape of the Anatolia (Armijo et al, 1999;Faccenna et al, 2006;Hubert-Ferrari et al, 2009;Le Pichon et al, 2015).…”

Multiphase Boudinage: a case study of Amphibolites in Marble in the Naxos Migmatite core

“…Jolivet et al, 2013;Philippon et al, 2011), or normal faulting in an overall extensional regime (Gautier et al, Solid Earth Discuss., https://doi.org /10.5194/se-2017- Hinsbergen and Schmid, 2012) including vertical axis rotations in the footwall (Malandri et al, 2017). Field evidence is controversial, as there seems neither support for a major detachment (Brun et al, 2016;Jolivet et al, 2015;Philippon et al, 2014), nor is strike-slip faulting observed on Paros, where the Mid Cycladic Lineament might be exposed (Malandri et al, 2017;Walcott and White, 1998a). Additional complexity is added due to interaction of slab roll-back with westward migration of the Anatolian Plate since ~11 Ma (Jolivet et al, 2013;Ring et al, 2010).…”