Stratigraphy and structural features of gerede (Bolu) and its surroundings

In the study area, located within the Armutlu-Almacık-Arkotdağı zone and the Sakarya zone, the Mesozoic (Middle Jurassic-Lower Cretaceous) Soğukçam formation lies at the base. The Upper Cretaceous Abant formation unconformably overlies this unit. The Kışlaköy formation overlies these units with an angular unconformity. Lower-Middle Miocene Kirazdağı volcanics, Middle Miocene Ilıcadere volcanics, and Deveören volcanics cut these units. Quaternary alluvium, the youngest unit in the study area, overlies these units with an angular unconformity. The rocks in the study area were significantly affected by the Alpine orogeny (Cretaceous-Paleogene) and recent tectonism during the Neotectonic period. During the Alpine Orogeny, the Cretaceous-Eocene rocks were deformed, folded, and acquired fractured structures. The North Anatolian Fault Zone (KAFZ), one of the most well-known and important faults in Turkey and the world, passes through the study area. The NAFZ, an active strike-slip right-lateral fault, extends in an ENE-WSW direction in the study area. The lineaments (Fractures and joints) in the study area are observed to be concentrated mostly in the northern and southeastern parts of the KAFZ. The crack sets generally develop in a NW-SE direction, with a second crack set parallel to the fault. Within the scope of morphotectonic analyses in the study area, the basin shape index (Bs), stream length gradient index (SL), valley floor width to valley height ratio index (Vf), basin asymmetry factor index (Af), mountain front curvature ratio index (Smf), and hypsometric integral (Hi) indices were investigated. Based on these, the relative tectonic activity of the NAFZ in the study area was examined.