Normal faulting on Sifnos and the South Cycladic Detachment System, Aegean Sea, Greece

Abstract

We constrain the timing and kinematics of normal faulting on Sifnos, Cyclades, Greece. Penetrative top-to-the-NE kinematic indicators associated with a shallow dipping foliation occur in the deepest tectonic unit (Greenschist Unit). Combined P-T analysis and Rb-Sr dating indicates that this deformation was under way by 29.4 AE 3.4 Ma at P-T conditions of c. 16 kbar and c. 550 8C, and continued to operate at least until 22.8 AE 0.2 Ma at P-T conditions of c. 8 kbar and c. 400 8C. The later top-to-the-south directed Sifnos Detachment developed at the top of the Greenschist Unit and cuts the top-to-the-NE structures. Zircon fissiontrack ages suggest that deformation on the Sifnos Detachment was largely terminated by about 13-10 Ma. Subsequent extension was accommodated by high-angle normal faults. Regionally the top-to-the-south detachment phase on Sifnos correlates with top-to-the-south extensional faulting on nearby Serifos, which started there at c. 15-13 Ma. Top-to-the-south extensional shearing on Ios to the SE commenced earlier at c. 19-18 Ma, suggesting that top-to-the-south extension propagated westward from Ios to Sifnos and Serifos, or that extension was partitioned into different top-to-the-south detachment systems that operated at different times. Collectively these top-to-the-south detachments are named here the South Cycladic Detachment System, which played a key role in the opening of the Cretan Sea forearc basin.

The geological signature of a slab tear below the Aegean

“…A top-to-the south detachment has also been described on Ios and Sifnos (Lister et al, 1984;Vandenberg and Lister, 1996;Ring et al, 2011). Huet et al (2009) have however…”

“…(Altherr et al, 1982;Henjes-Kunst et al, 1988;Wijbrans and McDougall, 1988;Schliestedt et al, 1994;Keay et al, 2001;Hejl et al, 2002;Parra et al, 2002;Ring et al, 2003;Bröcker et al, 2004;Jolivet et al, 2004a;Kumerics et al, 2005;Brichau et al, 2006;Bröcker and Franz, 2006;Duchêne et al, 2006;Martin et al, 2006;Brichau et al, 2007;Skarpelis et al, 2008;Baltatzis et al, 2009;Iglseder et al, 2009;Liati et al, 2009;Seward et al, 2009;Bolhar et al, 2010;Brichau et al, 2010;Denèle et al, 2011;Ring et al, 2011;Schneider et al, 2011;Grasemann et al, 2012;Bargnesi et al, 2013;Berger et al, 2013;Bröcker et al, 2013;Soukis and Stockli, 2013;Beaudoin et al, 2014;Huet et al, 2014;Laurent et al, 2015) A C C E P T E D M A N U S C R I P T…”

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

“…Exhumation of these metamorphic units first occurred between 45 and 35-30 Ma in a syn-orogenic context, following a cold retrograde path (figure 5) [Altherr et al, 1979;Bonneau and Kienast, 1982;Avigad and Garfunkel, 1989;Trotet et al, 2001]. These Eocene HP-LT parageneses are particularly well preserved in the Syros and Sifnos islands where syn-orogenic extensional shear zones, such as the Vari detachment in Syros (figure 6), show top-to-the ENE and top-to-the N senses of shear, respectively (figure 3) [Trotet et al, 2001;Keiter et al, 2004;Ring et al, 2011;Roche et al, submitted]. In the Ios island, a coeval top-to-the S structure called the South Cycladic Shear Zone (SCSZ) is observed at the base of the Cycladic Blueschists unit (figure 6).…”

The Tectonostratigraphy of Cycladic Blueschist Unit on Sikinos and Sifnos: Implication for the Mesozoic Tectonic Setting

“…800-900m marbles. It is noted, that the contact between these two subunits is an extensional detachment with limited displacement (Ring et al, 2011), revealing minor disruption of the original stratigraphic succession. On north Sifnos (Cherronisos and Psarobitima areas; Fig.…”

“…During D3 deformation, the early D2 thrust contact was folded by F3 recumbent to gently inclined folds, which are genetically associated with thrust-sense shear zones. On south Sifnos, the contact between Main marble subunit and Greenschist subunit is considered to be a brittle extensional detachment but with limited displacement (Avigad, 1993, Ring et al, 2011.…”