Structure and kinematic evolution of the southern Sivas fold-thrust belt, Sivas Basin, Central Anatolia, Turkey

Abstract

The architecture, kinematics, and timing of fold-and-thrust belt development provide essential first-order constraints onthe structural evolution of continental collision zones. The southern Sivas fold-thrust belt (SSFTB) is a ~300 × 50-km-long, ENEtrending contractional belt located in the Sivas Basin at the western end of the Arabia-Eurasia collision zone, and along the İzmirAnkara-Erzincan and Inner Tauride suture zones. We present new geologic mapping and the first detailed structural characterizationand seismotectonic evidence of active deformation along the western and central segments of the SSFTB that provide new insightsinto the timing and kinematics of deformation associated with collision and escape in Central Anatolia. The SSFTB is a dominantlynorth-vergent contractional belt that initiated during the late Eocene and experienced several punctuated episodes of shortening andexhumation, primarily during the late Oligocene and late Miocene. Structural mapping and balanced cross-sections reveal that minimumcumulative shortening increases from west (29%) to east (34%) along the belt, along with a gradual eastward increase in fold asymmetryand a progressive transition from fold-related to overturned fold-and-thrust-related shortening. The kinematics of the central andeastern SSFTB changed from north-vergent thrusting during the late Eocene and Oligocene to predominantly south-vergent during theMiocene. Contraction in the SSFTB ended by ~7–6 Ma and was followed by a switch to distributed and kinematically linked sinistralstrike-slip and normal faulting along the northeastern segment of the Central Anatolian fault zone. Offset strain markers suggest a totalof at least 1.7–2.4 km of left-lateral slip on the Deliler fault and ~940 m of normal slip on the Hınzır fault. The latest Miocene to Plioceneswitch to intraplate strike-slip deformation marks a regional transition to westward tectonic escape of the Anatolian microplate.