Browsing by Author "Ozsayin, Erman"

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Earthquake Induced Sedimentary Structures (Seismites): Geoconservation and Promotion as Geological Heritage (Lake Van-Turkey)
(Springer Heidelberg, 2017) Uner, Serkan; Aliriz, Merve Gizem; Ozsayin, Erman; Selcuk, Azad Saglam; Karabiyikoglu, Mustafa
The Lake Van Basin, located at the collision zone of the Eurasian and Arabian plates, has great potential in terms of geological heritage. The world's largest soda lake which gives its name to the basin contains magnificent geological structures. Lacustrine deposits of the lake represent important clues about seismic activity during the Late Quaternary in addition to its sedimentological and paleontological background. Seismites-deformational structures which are formed during earthquakes in unconsolidated sediments-are very rare geologic phenomena. These structures, formed by earthquakes of magnitude >= 5 under suitable conditions, provide valuable information about the responsible faults and their seismic repetition frequency for the region. Today, rising awareness of geological heritage is a glimmer of hope for the protection and preservation of these rare structures in the Lake Van Basin for the generations to come. Conservation of these structures will also help the protection of other naturally, historically, and culturally significant geological beauties. The responsibility for the promotion and conservation of these geological heritages should be a mission not only for the hosting country but also for the entire geological community.
Evolution of Camlik Fissure-Ridge Travertines in the Baskale Basin (Van, Eastern Anatolia)
(Taylor & Francis Ltd, 2017) Selcuk, Azad Saglam; Erturac, M. Korhan; Uner, Serkan; Ozsayin, Erman; Pons-Branchu, Edwige
Fissure-ridge travertines (FRTs) are of great importance for the determination and comparison of tectonic deformation in a region. The coeval development of these travertines with active fault zones supplies significant information about regional dynamics in terms of deformation pattern and evolution. In this paper, the characteristics of FRTs of the Baskale basin (eastern Turkey) and responsible regional tectonism are discussed for the first time. The Baskale basin is located between the Baskale Fault Zone (BFZ) characterised by Camlik fault and Isikli-Ziranis fault. It is located between dextral Yuksekova Fault Zone and southern end of dextral Guilato-Siahcheshmeh-Khoy Fault system (Iran). Various morphological features indicating recent activity are exposed along the BFZ, including offsetting rivers, fissure-ridge travertine and fault scarps. The Camlik fissure-ridge travertine composing of three different depositions is observed along the eastern edge of the BFZ with approximately parallel orientations. The Famlik fissure-ridge travertine has been formed and developed on fault zone related to strike-slip or oblique movements. We explain how kinematic changes of faults can influence the fissure-ridge development.
Late Quaternary Subsidence Records From the Datca Graben and Cnidus Ancient City (Sw Turkey): Sea-Level Changes Versus Tectonics
(Univ Barcelona, 2021) Ozsayin, Erman; Uner, Serkan; Kahraman, Burcu
The Datca Graben in southwestern Anatolia is a WNW-trending seismically active depression, with tectonic activity since Pliocene time. This tectonic activity is controlled by normal faults, which have effected ancient settlements. The Cnidus city (old and modern) -an ancient mercantile centre during the Hellenistic, Roman and Byzantine periods- is one of the places that has recorded this activity. The ancient harbour walls of Cnidus, lying 2.2-4.0m below sea level, contain important traces about sea-level changes and tectonics over the past 2.6kyr. Palaeostress analysis along boundary faults in the Datca graben yields an almost N-S oriented pure tensional regime, compatible with earthquake focal mechanism solutions located around the Datca peninsula. Additionally, an almost E-W trending surface rupture related to a historical earthquake in modern Cnidus, which shows normal fault characteristics, gives further support to the ongoing extension along the Kizlan, Karakoy and Cnidus fault zones. Previous studies on late Quaternary sea-level changes around the Datca peninsula suggest that 2.6kyr ago sea level was 1.0-1.25m lower than today. From the present-day depth of the old Cnidus harbour remains and regional sea-level records, it can be inferred that tectonics has played a significant role. Our calculations show that the Datca graben is subsiding at rates of 0.36-0.46mm/yr in the central part and 1.05-1.15mm/yr in the southern part. These values match those found in other areas around the Datca peninsula.
Non-Seismic Soft-Sediment Deformation Structures From Late Pleistocene Lacustrine Deposits of Lake Van (Eastern Turkey): Storm and Overloading Effect
(Elsevier Sci Ltd, 2019) Uner, Serkan; Selcuk, Azad Saglam; Ozsayin, Erman
Soft-sediment deformation structures of different types and sizes are frequently observed in the lacustrine deposits of Lake Van. According to sedimentary features and regional factors, these structures are categorized as non-seismic originated and seismically-induced, soft-sediment deformation structures. Well-preserved non-seismic originated, soft-sediment deformation structures were observed in fine-grained sandy and silty deposits at three locations (Catakdibi, Yumrutepe, and Yukanisikli), and occur at different stratigraphic horizons, exhibiting morphological variability as they consist of load, flame, and slump structures. The formation mechanisms of these structures are determined by the characteristics of their sedimentary facies and environmental conditions. Overloading, caused by rapid coarse sediment deposition or underwater landslides, and storm waves are identified as triggering mechanisms, while rapid sediment accumulation and underwater mass movements caused by volcanogenic shakes are the conditions responsible for the formation of non-seismic soft-sediment deformation structures, in terms of regional geodynamics. (C) 2019 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved.
Polyphase Tectonic Evolution of the Aksu Basin, Isparta Angle (Southern Turkey)
(Slovak Acad Sciences Geological inst, 2015) Uner, Serkan; Ozsayin, Erman; Kutluay, Alkor; Dirik, Kadir
The Aksu Basin, within the Isparta Angle, is located to the north of the intersection of the Aegean and Cyprus arcs and has been evolving since the Middle Miocene. Correlation of: (1) kinematic analysis of fault planes that cut the basin fill, (2) the reactivation/inversion of fault planes and (3) sedimentological data indicate that the Aksu Basin has evolved by four alternating compressional and extensional tectonic phases since its formation. The first phase was NW-SE oriented compression caused by the emplacement of the Lycian Nappe units which ended in Langhian. This compressional phase that induced the formation and the initial deformation of the basin was followed by a NW-SE extensional phase. This tectonic phase prevailed between the Langhian and Messinian and was terminated by a NE-SW compressional regime known as the Aksu Phase. The neotectonic period is characterized by NE-SW extension and began in the Late Pliocene. Correlation with the existing tectonic literature shows that the order of deformational phases proposed in this study might also be valid for the entire Isparta Angle area.
Reconstructing the Sedimentary Evolution of the Miocene Aksu Basin Based on Fan Delta Development (Eastern Mediterranean-Turkey)
(Tubitak Scientific & Technological Research Council Turkey, 2018) Uner, Serkan; Ozsayin, Erman; Dirik, Ramazan Kadir; Ciner, Tahsin Attila; Karabiyikoglu, Mustafa
The Aksu Basin in southern Turkey is dominantly represented by an alluvial fan and five fan deltas (FDs) developed along the tectonically controlled margins of the basin during the Miocene. Four alternating compressional and tensional tectonic phases have influenced the basin since its formation. Strong tectonic movements caused high sedimentation rates and progradation of large debris-flow and mass-flow dominated FDs. Here we describe two FDs (the Karadag and Kargi FDs) in detail. The Karadag FD began to develop under the control of a compressional regime and continued the evolution under a tensional regime. The same tensional regime caused the separation of the Karadag FD from its source and the deposition of the Kargi FD into the newly formed accommodation area. The alternating tectonic regimes and sea-level oscillations in the Aksu Basin gave rise to the development of coral colonies on the shallow delta fronts, forming patch reefs despite the large amounts of conglomerates supplied by fan deltaic processes.
Seismites as an Indicator for Determination of Earthquake Recurrence Interval: a Case Study From Ercis Fault (Eastern Anatolia-Turkey)
(Elsevier, 2019) Uner, Serkan; Ozsayin, Erman; Selcuk, Azad Saglam
The southern part of the Eastern Anatolian Plateau is a key region for understanding the tectonic activity and related deformation patterns of the Arabian-Eurasian collision zone. The geological record of seismic events collected from lacustrine deposits of Lake Van Basin is a critical requirement for seismic hazard assessment and seismic risk reduction. Our paleoseismic investigations revealed well-preserved seismites at five locations in late Pleistocene lacustrine deposits. The seismites were dated using an optically stimulated luminescence dating method and were arranged according to their ages. Their type, such as convolute, dish-and-pillar, flame, and ball-and-pillow structures, as well as their locations, ages, and stratigraphic distribution enable us to identify the responsible fault and the earthquake recurrence interval. On the basis of these properties, the Ercil Fault has been recognized as the structure responsible for creating the seismites. The time span between the seismites indicates an apparent earthquake recurrence interval of 125-250 years for large earthquakes (M >= 5) related to the Ercis Fault. The method applied here enriches our knowledge on the seismic hazards present in the northern Lake Van region.
Tectonic Geomorphology of Bozdo?an and Karacasu Grabens, Western Anatolia
(Univ Barcelona, 2023) Ozsayin, Erman; Dirik, Kadir; Ocakoglu, Faruk; Cartigny, Sanem Acikalin; Selcuk, Azad Saglam
Western Anatolia is one of the most rapidly extending and seismically active regions in the world. The circa N-S extension since the Early Miocene caused the formation of E-W trending major grabens and intervening horsts, having earthquake potentials with magnitude >= 5. The E-W oriented Buyuk Menderes Graben cross-cuts the broadly N-S oriented Bozdogan and Karacasu grabens, of which the boundary faults of the latter are the source of seismic activity. Geomorphic indices, including drainage basin asymmetry, mountain front sinuosity, valley-floor width to valley height ratio, stream length-gradient index and normalized channel steepness index, were used to evaluate the boundary fault segments of the Bozdogan and Karacasu grabens. The results indicate that both grabens are tectonically active and therefore regions of earthquake potential, consistent with the epicenters of earthquakes. Thus, it can be inferred that fault segments of second-order grabens, which are crosscut by the boundary faults of seismically active main depressions, are apparently reactivated by ongoing tectonism and may represent seismic activity. This suggestion applies also for similar basins located in the western Anatolia.
Tectonic Geomorphology of the Hoyran Graben (Western Anatolia, Türkiye): Insights From Geomorphic Indices
(Polish Geological inst, 2024) Cetin, Yaren Sena; Agar, Hasan Salih; Kahraman, Burcu; Bayram, Levent; Kul, Ahmet Ozkan; Ozsayin, Erman; Uner, Serkan
The area be tween West ern Anatolia and Isparta Bend com prises nu mer ous de pres sions and the ac tive faults that bound them. The Hoyran Graben is one of these de pres sions, lo cated at the north ern most part of the Isparta Bend. This NE-SW-ori ented graben is bounded by the Hoyran Fault in the north west and the Uluborlu, Senirkent and Kumdanli faults in the south-east, re spec tively. We eval u ate the seis mic ac tiv ity po ten tial among seg ments of the bound ary faults in the light of field work and morphometric in di ces. These bound ary faults of the Hoyran Graben are di vided into twelve seg ments for the analysis, with indices used including mountain-front sinuosity (Smf: 1.05-2.02), val ley floor width-to-val ley height ra tio (Vf: 0.11-1.34), hypsometric curve and in te gral (Hi: 0.4-0.73), asymmetry factor (Af: 13.76-87.03), stream length-gra di ent (SL: 1.48-9450) and nor mal ized chan nel steep ness (Ksn: 2.38-990.38). The re sults ob tained, to gether with field ob ser va tions, in di cate that the Uluborlu, Senirkent and Kumdanli faults, as well as the west ern seg ments of the Hoyran Fault, rep re sent higher po ten tial in terms of seis mic ac tiv ity with up lift rates >0.5 mm/y, while the cen tral and east ern seg ments show mod erate ac tiv ity with up lift rates be tween 0.05 and 0.5 mm/y. Thus, the bound ary faults of the Hoyran Graben need fur ther at ten tion in terms of re gional seis mic haz ard.