Palaeomagnetic study of the Galatean Volcanic Province, north-central Turkey: Neogene deformation at the northern border of the Anatolian Block

A regional palaeomagnetic study is reported from 24 lavas of the (Late Miocene) Galatean Volcanic Province bordering the North Anatolian Fault Zone (NAFZ) in northern Anatolia. Rock magnetic studies show that the lavas have a ferromagnetic content dominated by low-Ti magnetite assemblages which have been subjected to variable degrees of high and low temperature oxidation. Although larger fractions of ferromagnetic grains are multidomain, significant fractions of single domain grains are always present and presumed to be responsible for the stable remanence at all sites. Magnetic remanence is interpreted to be essentially primary because it preserves a record of both polarities which has since been tectonically rotated. Fifteen sites define a coherent dipolar axis with a mean direction of D/I = 16.8/56.5 degrees (alpha(95) = 6.9 degrees). This is related clockwise by 10.2 +/- 7.2 degrees from the Eurasian field at 10 Ma and is interpreted to record block rotation during westward expulsion of lithosphere along the northern margin of the Anatolian region late in the Neotectonic history. Upper Cretaceous rocks from the northern side of this sector of the NAFZ exhibit rotations relative to Eurasia; whilst these may have been imparted partly during Eocene collision of the istanbul and Sakarya zones, consistent counterclockwise motions show that differential block rotations are occurring here with the Galatean region bounded at its northern margin by the NAFZ. Copyright (C) 1999 John Wiley & Sons, Ltd.