Palaeomagnetic study of the Erciyes sector of the Ecemis Fault Zone: Neotectonic deformation in the southeastern part of the Anatolian Block

Abstract

In the Turkish sector of the Afro-Eurasian collision zone, continuing northward motion of the Arabian promontory is extruding the Anatolian region to the west. Although the East Anatolian Fault Zone (EAFZ) is recognized as the southern boundary of this tectonic escape, distributed deformation is occurring across a broad zone extending for at least 300 km to the northwest, which includes a number of major dextral and sinistral fault lineaments. The longest of these lineaments is the Ecemis Fault Zone, although the long-term significance of deformation, and specifically strike-slip, across this zone is disputed. This zone is also the locus of major volcanic activity in the Kayseri region. The present paper reports a palaeomagnetic study of young (1-2 Ma) lava flows which has aimed to identify recent block rotations resulting from regional deformation in this region. Rock magnetism shows the lavas to be dominated by low-Ti magnetite assemblages of primary cooling related origin. Although grain properties are predominantly multidomain, significant fractions of single domains are always present and responsible for a stable thermoremanence of normal and reversed polarity. Whilst group mean directions show that the blocks in this sector of Anatolia show the typical counterclockwise rotation resulting from tectonic escape, in this case by c. 10°during the last 1 Ma, larger different rotations in both senses are identified across the Sultansazligi Depression. Comparable differential rotations recorded by the 2.8 ± 0.2 Ma Incesu Ignimbrite have resulted from the pull-apart in this sector of the Ecemis Zone which has accommodated emplacement of the Erciyes volcanic centre since the termination of ignimbrite activity. Within the wedge-shaped terrane confined between the EAFZ in the south and the North Anatolian Fault Zone in the north, the degree of counterclockwise rotation during tectonic escape within the last 2-3 Ma has diminished from c. 25°in the east of c. 10°towards the southwest. This corresponds to a transition from highly strained to a less-strained lithosphere as the width of the semi-plastic Anatolian terranes confined between the Arabian-Eurasian pincer broadens out to the west.