Shortening of continental lithosphere: the neotectonics of Eastern Anatolia — a young collision zone

Abstract

Summary We use the tectonics of Eastern Anatolia to exemplify many of the different aspects of collision tectonics, namely the formation of plateaux, thrust belts, foreland flexures, widespread foreland/hinterland deformation zones and orogenic collapse/distension zones. Eastern Anatolia is a 2 km high plateau bounded to the S by the southward-verging Bitlis Thrust Zone and to the N by the Pontide/Minor Caucasus Zone. It has developed as the surface expression of a zone of progressively thickening crust beginning about 12 Ma in the medial Miocene and has resulted from the squeezing and shortening of Eastern Anatolia between the Arabian and European Plates following the Serravallian demise of the last oceanic or quasioceanic tract between Arabia and Eurasia. Thickening of the crust to about 52 km has been accompanied by major strike-slip faulting on the right-lateral N Anatolian Transform Fault (NATF) and the left-lateral E Anatolian Transform Fault (EATF) which approximately bound an Anatolian Wedge that is being driven westwards to override the oceanic lithosphere of the Mediterranean along subduction zones from Cephalonia to Crete, and Rhodes to Cyprus. This neotectonic regime began about 12 Ma in Late Serravallian times with uplift from wide-spread littoral/neritic marine conditions to open seasonal wooded savanna with colluvial, fluvial and limnic environments, and the deposition of the thick Tortonian Kythrean Flysch in the Eastern Mediterranean. Earthquake hypocentres are scattered throughout the region but large earthquakes are concentrated mainly on the major faults and are mostly shallow, supporting the idea of a brittle elastic lid with hypocentres concentrated towards its base with more ductile deformation in the middle and lower crust. Neotectonic magmatic suites are nepheline-hypersthene normative alkali basalts of mantle origin, and silicic/intermediate/mafic calcalkaline suites, both suites occurring in pull-apart basins in strike-slip regimes and along N-S extensional fissures, and both suites showing a strong change to central activity in the Pliocene. Upper-crustal strains appear to be discontinuous in space and time, with zones of strong shortening representing shoaling of crustal detachment zones flattening between 5 and 10 km. Approximately NW- (dextral) and NE- (sinistral) trending lineaments bound less deformed wedges (low relief seismically ‘dead’ areas) and vary from simple strike-slip faults to complicated braided transform-flake boundaries with pull-apart and compressional segments (N and E Anatolian Transform Faults). Volcanoes lie in grabens on N-S ‘cracks’ that extend into the Arabian Foreland and in transcurrent pull-aparts. Major extensional basins lie at plate (Adana) and flake (Karliova) triple junctions and result from compatibility problems.

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

“…However, since the Miocene, no significant crustal thinning is observed in this region that is instead supported by an ~45 km thick crust supporting a 2 km high plateau [Dewey et al, 1986;Şengör et al, 2003]. Suggested on tomographic models, slab break-off below the Bitlis belt and arrival of asthenospheric flow from the Afar hot spot could allow the preservation of a high-elevation plateau and the thermal delamination of the lithospheric mantle below eastern…”

“…In the middle-late Miocene, the ongoing collision of Arabia with Eurasia along the Bitlis belt (figures 8r-w) is associated with the uplift of eastern Anatolia [Dewey et al, 1986;Şengör et al, 2003;Okay et al, 2010b] and the development of a wide magmatic province [Pearce et al, 1990;Keskin, 2003Keskin, , 2007. About 12 Ma ago, the whole Anatolide-Tauride block started to move westward, mostly accommodated by the dextral strike-slip NAF that propagated throughout the Pontides and reached the Dardanelle Strait 6-5 Ma ago (figures 8t-w) [Armijo et al, 1999;Şengör et al, 2005;Melinte-Dobrinescu et al, 2009].…”

Seismotectonics and rupture process of theMW 7.1 2011 Van reverse-faulting earthquake, eastern Turkey, and implications for hazard in regions of distributed shortening

“…Copley & Jackson 2006). Early estimates suggest that the initial collision was at ∼10 Ma (Dewey et al 1986), though palaeoclimate studies suggest it may have begun as early as ∼35 Ma (Allen & Armstrong 2008). Much of the current rate of ArabiaEurasia convergence (23 mm yr −1 ) is accommodated by shortening in the Caucasus, but around ∼10 mm yr −1 is distributed across the Turkish-Iranian Plateau (TIP; Reilinger et al 2006).…”

Different styles of faulting deformation along the Dead Sea Transform and possible consequences for the recurrence of major earthquakes

“…The DST has been active since the middle Miocene with a total displacement of 105 km in the south (Bartov et al, 1980;Eyal et al 1981;Garfunkel et al, 1981) and 70-80 km in the north (e.g. Freund et al, 1970;Dewey et al, 1986). However, the analysis of the structural displacement has been proved controversial (Westaway, 2004;Mart et al, 2005).…”