Geological evolution of the pasinler-horasan basin (Erzurum)

The convergence and following collision between the Arabian and Eurasian plates led to the formation of numerous compressional basins in the Eastern Anatolian Plateau. One of these, the Pasinler-Horasan Basin, is an E-W-trending basin located east of Erzurum city center, covering approximately 2,500 km². This thesis aims to produce the type, timing of formation, stratigraphy, boundary faults and their characteristics, and the geological evolution of the Pasinler-Horasan Basin. The Pasinler-Horasan Basin is bounded by the Pasinler Fault Zone to the southwest and the Erzurum Fault Zone to the west. The Horasan-Şenkaya Fault Zone, characterized by sinistral strike-slip characteristics, is located in the central part of the basin, separating the Pasinler and Horasan plains. According to field studies, thrust faults bordering the basin from the south and north (the Northern Thrust and the Southern Thrust), E-W-trending thrust faults cutting the basin fill (the Karacaören and Otlukkapı Ardı-Aras thrusts), and two sinistral strike-slip fault zones cutting the basin in a NE-SW direction (the Hızırilyas Fault Zone and the Aliçeyrek Fault Zone) were mapped and named for the first time in this thesis. Paleostress analyses indicate that all of the faults are the product of a compressional regime with a nearly N-S orientation. The seismicity of these strike-slip fault zones and thrust faults in the basin is determined through the existing earthquake records and focal mechanism solutions. The Pasinler-Horasan Basin, formed between two south-dipping thrust faults (the Northern and Southern Thrust) during the Early Miocene, indicates piggyback basin characteristics. Following the collision between the Arabian and Eurasian plates, the basin transitioned from marine to terrestrial environment due to regional uplift. The basin's sedimentary fill is represented by lacustrine sediments and alluviums from the Pliocene to Recent. Lacustrine conditions have been significantly affected by the tectonic activity of the region where the Pasinler-Horasan Basin is located and by volcanism effective since the Late Miocene. Geochemical analysis of the lacustrine sediments known as the Horasan Formation indicates that the lake was so contaminated with heavy metals that it negatively impacts life during the late Pliocene. It has been determined that the sources of As, Pb, Ni and Fe2O3, which are found in very high amounts, are ophiolitic rocks and/or volcanic rocks commonly found in the environment and they transported to the environment through hydrothermal activity along tectonic lines. Keywords: Basin analysis, Eastern Anatolia, Pasinler-Horasan Basin, Sedimentology, Structural geology