Isotopic dating of sheared and unsheared rocks can be important in understanding deformational processes in orogenic belts. This study examines 40 Ar= 39 Ar dating of granitoids and mylonitic rocks to constrain intrusive and deformational events within the northern part of the central Anatolian crystalline complex (CACC). The Kerkenez granitoid within this complex, comprising primarily quartz monzonite and hornblende granite, contains discrete ductile shear zones. These zones are characterized by protomylonite and mylonite formations with metamorphism conditions that reach lower amphibolite facies, mylonitic foliations and lineations, and asymmetric kinematic indicators (e.g., asymmetric porphyroclasts, composite shear bands) with top-to-the-northwest shear senses. Considering the high closure temperatures (∼500°C for hornblende and ∼350°C for K-feldspar), both hornblende quartz monzonite and hornblende granite in the Kerkenez granitoid may have cooled rapidly, suggesting that hornblende quartz monzonite may have been emplaced at around 81:2 ± 0:5 Ma and that it is older than hornblende granite, which has a well-defined plateau age (72:6 ± 0:2 Ma). On the basis of intrusive relations and our 40 Ar= 39 Ar age data, we can constrain the upper age limit (∼81 Ma) on the regional metamorphism in the northern part of the CACC. The 40 Ar= 39 Ar dating of hornblendes in two mylonite samples from a ductile shear zone yields plateau ages of 71:6 ± 0:3 and 71:7 ± 0:2 Ma, respectively. K-feldspars in the same samples yield plateau ages of 71:6 ± 0:2 and 81:3 ± 0:2 Ma. Therefore, we adopt 71:6 ± 0:3 and 71:7 ± 0:2 Ma as the cooling ages of hornblende and K-feldspar, respectively, in the ductile shear zone. On the other hand, an age of 81:3 ± 0:2 Ma for deformed K-feldspar appears to reflect not the age of ductile deformation but rather the age of undeformed hornblende quartz monzonite. These age data suggest that the shear zones formed soon after the emplacement and cooling of hornblende granite. The cooling event of the shear zones is interpreted to be associated with the beginning of extension in the region. Furthermore, these data imply that metamorphism, emplacement, and cooling of the intrusives and ductile shearing of the intrusions were coeval in the region and occurred in the Late Cretaceous.

We present the first detailed geological map of the tectonic units documented in the easternmost branch of the Intra-Pontide suture (IPS) zone in the Tosya-Kastamonu area (Northern Turkey). The Main Map is at 1:50,000 scale and covers an area of about 350 km 2 . It derived from 1:25,000 scale classic field mapping and represents a detailed overview of the complexities documented in the IPS zone, a tectonic nappe stack originating from the closure of the Intra-Pontide Oceanic basin and the subsequent collision between the Istanbul-Zonguldak terrane and the Sakarya composite terrane. The map shows the orientations of superposed foliations, fold axes and mineral lineations on the basis of geometric cross-cutting relationships documented within the five tectonic units of the IPS zone and provides information on its present-day architecture resulting from activity of the North Anatolian Fault. ARTICLE HISTORY