Subductions, obduction and collision in the Lesser Caucasus (Armenia, Azerbaijan, Georgia), new insights

Abstract

In the Lesser Caucasus three main domains are distinguished from SW to NE: (1) the autochthonous South Armenian Block (SAB), a Gondwana-derived terrane; (2) the ophiolitic Sevan-Akera suture zone; and (3) the Eurasian plate. Based on our field work, new stratigraphical, petrological, geochemical and geochronological data combined with previous data we present new insights on the subduction, obduction and collision processes recorded in the Lesser Caucasus. Two subductions are clearly identified, one related to the Neotethys subduction beneath the Eurasian margin and one intra-oceanic (SSZ) responsible for the opening of a back-arc basin which corresponds to the ophiolites of the Lesser Caucasus. The obduction occurred during the Late Coniacian to Santonian and is responsible for the widespread ophiolitic nappe outcrop in front of the suture zone. Following the subduction of oceanic lithosphere remnants under Eurasia, the collision of the SAB with Eurasia started during the Paleocene, producing 1) folding of ophiolites, arc and Upper Cretaceous formations (Transcaucasus massif to Karabakh); 2) thrusting toward SW; and 3) a foreland basin in front of the belt. Upper-Middle Eocene series unconformably cover the three domains. From Eocene to Miocene as a result of the Arabian plate collision with the SAB to the South, southward propagation of shortening featured by folding and thrusting occurred all along the belt. These deformations are sealed by a thick sequence of unconformable Miocene to Quaternary clastic and volcanic rocks of debated origin.

Role of the Allahyarlu ophiolite in the tectonic evolution of NW Iran and adjacent areas (Late Carboniferous — Recent)

“…1) (e.g. Berberian et al 1981;Majidi 1981;Sengör 1990;Alavi 1991a;Babakhani and Nazer 1991;Eftekharnejad and Asadian 1992;Golonka 2004;Kazmin and Tikhonova 2006;Galoyan et al 2009;Sosson et al 2010;Rolland et al 2011;Sheikholeslami and Kouhpeyma 2012). Here we discuss the evolution of NW Iran and the Lesser Caucasus using new evidence obtained from studies of the Allahyarlu ophiolite.…”

“…8) and its remnants were covered by Shemshak Formation sediments (Sengör 1984;Glennie 1992;Golonka 2004;Kazmin and Tikhonova 2006;Wilmsen et al Central European Geology 57, 2014 Role of the Allahyarlu ophiolite in the tectonic evolution of NW Iran and adjacent areas 373 2009; Sheikholeslami and Kouhpeyma 2012). The Sevan-Akera Basin, which began northward subduction beneath the North Armenian Block from the early Upper Jurassic, was narrowing at this time Kazmin and Tikhonova 2006;Galoyan et al 2009;Rolland et al 2009;Sosson et al 2010;Rolland et al 2011). The rifting and opening of the South Caspian-Black Sea Basin, which opened in the Middle Jurassic, continued in the Late Jurassic (Berberian 1983;Bazhenov et al 1996;Brunet et al 2003;Nikishin et al 2003;Hinds et al 2004;Kazmin and Tikhonova 2006).…”

“…This basin began opening 165.3 ± 1.7 Ma ago Rolland et al 2011). The Armenian Basin, as a Neotethyan back-arc basin, was an active Andean-type margin during the Middle Jurassic-Lower Cretaceous Kazmin and Tikhonova 2006;Galoyan et al 2009;Rolland et al 2009;Sosson et al 2010;Rolland et al 2011). A tensional basin was formed between the Sanandaj-Sirjan and the Central Iran zones, which later created Neotethys II (Glennie 1992;Alavi 1994;Sengör and Natal'in 1996;Golonka 2004;Shahabpour 2005;Sheikholeslami et al 2008;Arfania and Shahriari 2009;Glennie et al 2011;Kargaranbafghi et al 2012).…”

“…The Araks Fault is a sinistral strike-slip fault (Alavi 1991b;Barka and Reilinger 1997;Allen et al 2005;Galoyan et al 2009;Sosson et al 2010;Adamia et al 2011). This fault, of NE-SW trend and with its sinistral movements, displaced NW Iran lithologies (Didon and Gemain 1976 The Allahyarlu-Kaleybar-Northern Iran Suture Zone, determined by Late Carboniferous to Triassic metamorphic and ophiolitic exposures, was the western continuation of a branch of the Paleotethys Basin in Iran (Alavi 1991b;Ruttner 1993;Alavi 1996;Ghazi et al 2001;Seyed-Emami 2003;Zanchi et al 2006;Ghavidel-Syooki 2008;Zanchetta et al 2009;Omrani and Moazzen 2010;Sheikholeslami and Kouhpeyma 2012;Shafaii Moghadam et al in press).…”

“…However, it should be mentioned that the opening-closing ages of the Allahyarlu-Kaleybar-Northern Iran ophiolites is Late Carboniferous to Triassic, respectively, while the opening-closing ages of the Sevan-Akera ophiolites is Middle Jurassic to Lower Cretaceous, respectively. Since the Sevan-Akera ophiolites were formed by Neotethys subduction and at its back-arc basin Rolland et al 2009;Sosson et al 2010;Rolland et al 2011), it is unreasonable to consider the Allahyarlu-Kaleybar Suture Zone as the western continuation of the Sevan-Akera Suture.…”