Rifting and shallow-dipping detachments, clues from the Corinth Rift and the Aegean

Abstract

: The Corinth Rift is superimposed on the Hellenic nappe stack that formed at the expense of the Apulian continental crust above the subducting African slab. Extension started in the Pliocene and the major steep normal faults that control the geometry of the present-day rift were born very recently, some 600 Kyrs ago only. They root into a shallowdipping zone of microseismicity recorded near the base of the upper crust. The significance of this seismogenic zone is debated. Considering the northward dip of the zone of microseismicity, the depth of microearthquakes and their focal mechanisms, we observe a strong similarity with the northern Cycladic detachments in terms of expected pressure, temperature conditions and kinematics. We herein show (1) that the formation of the Corinth Rift can be considered a part of a continuum of extension that started some 30-35 Ma in the Aegean and that was recently localised in a more restricted area, (2) that the present-day structure and kinematics of the Corinth Rift can be explained with a series of decollements relayed by steeper ramps that altogether formed a mechanically weak, crustal-scale detachment, and (3) that the deformation, fluid behaviour and metamorphic features seen in the northern Cycladic metamorphic core complexes can be good analogues of the processes at work below the Corinth Rift. 2Introduction.

Kinematic reconstructions and magmatic evolution illuminating crustal and mantle dynamics of the eastern Mediterranean region since the late Cretaceous

“…Finally, additional extensional basins opened in the Peloponnese and along the eastern coast of the Hellenides, within the so-called Central Hellenides Shear Zone [Papanikolaou and Royden, 2007;Royden and Papanikolaou, 2011]. These basins include the Gulf of Corinth, which has accommodated ~15 km of N-S extension since the Pliocene (figure 3) [Armijo et al, 1996;Rohais et al, 2007;Jolivet et al, 2010b].…”

“…Further west, the Gavrovo-Tripolitza and Ionian platforms started to subduct at the same time after the closure of the Pindos basin (figure 9) [Sotiropoulos et al, 2003;van Hinsbergen et al, 2005b]. The external parts of these carbonate platforms were accreted to the Hellenides, remaining at low pressure while their buried internal parts, comprising their basements, recorded HP-LT metamorphism forming the Phyllite-Quartzite and the Plattenkalk units in Crete and the Peloponnese [Bonneau and Kienast, 1982;Seidel et al, 1982;Theye et al, 1992;Trotet et al, 2006;Jolivet et al, 2010b]. These metamorphic units were then exhumed in the footwall of the top-to-the N Cretan detachment since ~25 Ma, following a cold retrograde path [Jolivet et al, 1996[Jolivet et al, , 2010cRing et al, 2001].…”

“…Tectonic map showing the main data used to constrain the kinematic evolution of the eastern Mediterranean region, including the stretching lineations in the MCCs [Rimmelé et al, 2006;Bonev and Beccaletto, 2007;Jolivet et al, 2013], the offset of main structures [Armijo et al, 1999;Jolivet et al, 2004aJolivet et al, , 2010bBrichau et al, 2006Brichau et al, , 2008 and the vertical-axis rotations deduced from paleomagnetic studies [Kissel and Laj, 1988;Kissel et al, 1993Kissel et al, , 2003Pǎtraşcu et al, 1994;Morris and Anderson, 1996;van Hinsbergen et al, 2005avan Hinsbergen et al, , 2008van Hinsbergen et al, , 2010aBrun and Sokoutis, 2007;Bradley et al, 2013]. CW: clockwise rotation.…”

High-angle, not low-angle, normal faults dominate early rift extension in the Corinth Rift, central Greece

“…1A). The western part of the rift has long been used as an example of a setting where low-angle normal faulting plays a key role in strain accommodation (e.g., Jolivet et al, 2010;Sorel, 2000) and is commonly referred to by studies reviewing LANF mechanisms (e.g., Lecomte et al, 2012). The Corinth Rift is amagmatic, and like the central Apennines, it occurs within orogenically thickened crust; however, the Corinth Rift runs orthogonal, not parallel, to the Hellenide orogeny.…”

Active faulting at the western tip of the Gulf of Corinth, Greece, from high-resolution seismic data

“…At depths greater than 5 km, seismological studies have evidenced a fully asymmetrical extensional system, where deformation occurs on a horizontal or low-dipping zone of microseismicity linked to the north-dipping coastal fault system Lyon-Caen et al, 2004). This zone has been interpreted as the brittle-ductile transition , or as a crustalscale detachment (Jolivet et al, 2010), or as a newly formed blind detachment . The present study aims to complete the fault map of the Corinth Rift at its Western tip, west of Aigion (Fig.…”