Bayburt Yöresi Kayaçlarının Yapısal Özellikleri
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ABSTRACT STRUCTURAL FEATURES OF THE BAYBURT REGION ROCKS Hünkar DEMİRBAĞ Doctor of Philosophy, Department of Geological Engineering Supervisor: Prof. Dr. M. Tekin YÜRÜR January 2023, 93 pages 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 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 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 CretaceousPaleogene, 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. Eocene volcano-sedimentary rocks deposited unconformably overlain all units. After the collision, an extensional tectonic regime developed due to iv 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. 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. 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. 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 NESW 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 Late Eocene (35.8±1.4 Ma) basaltic andesites and middle Eocene (43.81±0.63 Ma) granitoids show that these rocks were deformed under the influence of the approximately N120° axial (NW-SE) extensional tectonic regime. Keywords: Eastern Pontides, Bayburt, Extensional Tectonic Regime, Horst, Graben, Detachment Fault.