Structural features of the bayburt region rocks

The study area is located in the north of Bayburt, Aydıntepe, in the Eastern Pontides. The basement rocks are Devonian-early Carboniferous rocks intruded by the Carboniferous granitoids, which metamorphosed under high temperature at the age of 330 Ma during the Hercynian (Variscan) Orogeny. On these basement rocks located on the southern edge of the Laurasia in the Late Paleozoic, volcano-sedimentary rocks and Upper Jurassic-Lower Cretaceous platform limestones, formed as a result of rifting in the İzmir-Ankara-Erzincan Ocean, were deposited unconformably. As a result of the subduction processes that started with the subduction of the Tethys Ocean under the Laurasian Continent in the Late Cretaceous (Albian-Aptian), the Black Sea began to open up as a rifting back-arc basin in the north of the arc. During the Late Cretaceous-Paleogene, the sediments accompanied by rift volcanism were deposited behind the arc and oceanic crust began to form behind the arc from the early Santonian. In the arc, subduction related plutonism during Cretaceous-Paleocene and volcanic activity, which developed simultaneously with sedimentation from Turonian, started and this volcanic activity continued until Maastrichtian. During the Late Cretaceous, both acidic, basic volcanic, sub-volcanic rocks and pyroclastic rocks and sedimentary rocks with similar lithologies were deposited simultaneously in and behind the arc. The subduction processes of the Tethys Ocean continued with the continent-continent collision in the late Paleocene-early Eocene. After the collision, an extensional tectonic regime developed due to orogenic collapse, the mid-Eocene collisional, generally porphyritic, semi-depth rocks intruded into the continent and cut the Cretaceous-Paleocene arc-origin holocrystalline textured plutonic rocks and the Late Cretaceous units formed in the arc. Eocene acidic, basic volcanic, sub-volcanic rocks and pyroclastic rocks of "collisional" and "post-collision" origin and sedimentary rocks deposited simultaneously with pyroclastic rocks unconformably overlain all units. Basalt samples taken from the upper levels of the Eocene cover rocks unconformably overlying the Kaçkar Granitoids, with K/Ar method 35.8±1.4 Ma (Whole rock) (Priabonian-late Eocene), Upper Jurassic-Lower Cretaceous limestones unconformably overlying the cover rocks of basaltic andesites with K/Ar method 44.4±1.7 Ma (Whole rock) ) (Lutetian-middle Eocene), 43.81±0.63 Ma (Lutetian) ages were obtained from the zircons in granite porphyries outcropping in the Karaçam valley by the 206Pb/238U method. During the Late Cretaceous, areas of subduction-related granitoids with holocrystalline texture, which are intrusively embedded in the volcano-sedimentary rocks formed in places within the basement rocks and in the arc rose above sea level in the Paleocene because of fast vertical uplift. These mountains, which rise in the form of NE-SW trending ridges in the arc region, have become positive areas, and as a result of erosion processes, they gave granitic and volcanic pebbles to the conglomerates at the base of the Lower Eocene cover rocks. The vertical uplift of the region, which continued during the Late Cretaceous, continued during the Paleogene and Neogene times. In the south of the study area, the Eocene volcanosedimentary rocks are unconformably overlain by Miocene lacustrine sedimentary rocks and the uppermost Quaternary units. These geological events that continued throughout the Mesozoic-Cenozoic, especially the intra-arc region of the Pontides, are today at about 3500 m. heights. The fact that granitoids formed in the earth's crust 80 My ago, at a depth of about 15-20 km, rose above sea level 61 My ago and are observed today on high mountain peaks, indicate a rapid rise in the Pontides. This uplift was controlled by tectonic processes that resulted in the subduction of the Tethys Ocean under the Laurasian continent during the Late Cretaceous and continental-continental collision at the end of the early Paleocene. We can see the tectonic structures developed under the influence of the compressional tectonic regime in the Eastern Pontides in the south, which can be defined as fore-arc and trench domains with reverse faults, thrust faults and folded structures in the region between the İzmir-Ankara-Erzincan suture, the North Anatolian Fault and Bayburt. However, instead of the structural data showing the compressional tectonic regime in the rocks exposed in the study area, tectonic structures pointing to extensional tectonic regime are observed. This shows that the tectonic forces pointing to the compressional tectonic regime expected to be observed in the Eastern Pontides during the mountain formation movements that developed as a result of the closure of the Tethys Ocean and the continent-continent collision were not effective enough in this area. According to the current GPS data of Turkey, which is located between the Eurasian plate and the African-Arabic plates, it will be seen that there is almost no lateral movement in the Eastern Pontides and that this region does not produce earthquakes at the same time. Considering that the North Anatolian Fault was formed in the last 15-20 Ma and is active today, this compressional tectonic regime is met by the deformation and displacement movements along the North Anatolian Fault, the Northeast Anatolian Fault and the East Anatolian Fault without affecting the Eastern Pontides in the north. After the middle Eocene, the Eastern Pontides continued to rise under the influence of the extensional tectonic regime that developed due to orogenic subsidence. Normal faults, detachment faults and listric faults along NE-SW ridges have resulted in the formation of horst and grabens, half grabens and sag ponds in the Eastern Black Sea Region. Structural data measured in the late Eocene (35.8±1.4 Ma) basaltic andesites show that these rocks were deformed under the influence of the N120° axial (NW-SE) extensional tectonic regime.