Palaeomagnetism of the Cappadocian Volcanic Succession, Central Turkey: Major ignimbrite emplacement during two short (Miocene) episodes and Neogene tectonics of the Anatolian collage

Abstract

The Central Anatolian Volcanic Province in Cappadocia includes 13 high volume calc-alkaline ignimbrite sheets emplaced by plinian eruptions within a succession (the Urgup) Formation) after -10 Ma recording the last phase of Neotethyan subduction and accompanying emplacement of the Tauride orogen in southern Turkey. To evaluate magnetostratigraphy in the context of recent revisions of the chronostratigraphy we have extended palaeomagnetic investigation to 32 new sites yielding significant ChRM directions. Integrated rock magnetic and palaeomagnetic investigations identify magnetic remanence residing predominantly in Ti-poor titanomagnetites although secondary processes within the ignimbrite sheets, notably post-emplacement oxidation, have locally produced hematisation expressed by composite IRM spectra and variable reduction in intensity of magnetisation. The ignimbrite sheets possess weak anisotropies of magnetic susceptibility (AMS, mostly <5%) describing tensors with axial distributions close to bedding and minimum axes predominantly perpendicular to this plane; collectively directions show weak imbrication correlating with palaeofiow during emplacement predominantly towards the north and east away from the Erdas Dag, an inferred topographic palaeohigh at the southern margin of the basin. The precise control provided by magnetostratigraphy and radiometric age dating now shows that the bulk of Cappadocian ignimbrite magmatism was concentrated into two short episodes. An older Cardak Centre (Kayak Group and Zelve ignimbrites) produced in excess of 200 km(3) of pyroclastic deposits during polarity chron C4r.1n between 9.31 and 9.43 Ma. Subsequent activity from the Acigol Centre further to the south west (Cemilkoy, Gelveri, Gordeles, and Kizilkaya) produced in excess of 620 km3 of pyroclastic deposits during polarity chrons between 53 and 7.1 Ma. The younger Incesu ignimbrite was sourced in the Sultansazlrgi pull-apart basin to the east during the Gauss Chron (2.58-3.60 Ma). All pre-incesu ignimbrites are rotated uniformly anticlockwise and the overall (reversed) group mean direction of magnetisation is D/I = 170.8/-52.4 degrees (N = 9,R = 8.91, alpha(95) = 5.4 degrees, k = 91). The implied tectonic rotation in this sector of central Anatolia (16 +/- 4 relative to Eurasia) is young and postdates the 5.3-7.1 Ma Acigol Centre whilst largely predating emplacement of the incesu ignimbrite. Whilst rotational deformation within Anatolia is young, it proves to be distributed with a temporal variation from block to block. It is embraced by a complex post-Miocene tectonic regime of strike slip and extension during tectonic escape and suction towards the Hellenic Arc to the west. (C) 2013 Elsevier B.V. All rights reserved.