Kayın, Sercan; Hisarlı, Z. Mümtaz; İşseven, Turgay; Dokuz, Abdurrahman; Algur, Bahadırhan Sefa

The study area covers a region oriented north-south from the Black Sea coastline in the north to the Kelkit Basin in the south within the eastern Sakarya Zone in northern Türkiye. The objective of this study is to investigate the paleolatitudinal movements of the eastern Sakarya Zone during the Jurassic-Eocene time interval through paleomagnetism. Various volcanic and sedimentary units (e.g., the Şenköy, Berdiga, Mescitli, Çatak, Kızılkaya, and Çağlayan Formations) spanning the time interval from the Early Jurassic to Middle Eocene were identified. A total of 98 locations belonging to Early/Middle Jurassic to Eocene volcanic and sedimentary units were selected for paleomagnetic core sample collection. The samples were subjected to demagnetization through thermal and alternating field methods. Characteristic remanent magnetization directions (ChRM) were obtained. Isothermal remanent magnetization (IRM) and high temperature susceptibility (HTS) measurements were made to identify the minerals responsible for magnetization. To ascertain whether magnetization was acquired through rock formation or as a consequence of subsequent tectonic processes, conglomerate and fold tests were performed. The results showed that magnetization was acquired before folding, i.e., the rocks have primary magnetization. Polarity tests were also conducted using coeval normal and reverse polarity sites. The results indicate that the mean magnetization direction for the Early-Middle Jurassic is 18.1°/55.2° (D/I) and 3.3°/51.5° (D/I) for sedimentary and volcanic rocks, respectively, and 348.7°/46.7° (D/I) for Late Jurassic/Early Cretaceous sedimentary rocks. In the Late Cretaceous period, the mean magnetization direction is 8.0°/49.3° (D/I) and 9.1°/47.0° (D/I) for sedimentary and volcanic rocks, respectively. In the case of the Early/Middle Eocene, the mean magnetization direction is 348.6°/52.7° (D/I) and 5.9°/48.8° (D/I) for sedimentary and volcanic rocks, respectively. In this study, the E/I correction was applied to the Late Jurassic/Early Cretaceous sedimentary rocks, and paleolatitude data obtained from sedimentary rocks were also utilized. Our paleomagnetic results indicate that the eastern Sakarya Zone was situated at latitudes spanning from 27.9° to 35.7° during the Early Jurassic - Middle Eocene time interval. In consequence, the eastern Sakarya Zone constituted a portion of the southern margin of the Eurasian continent during the Late Jurassic and Middle Eocene periods.

Kayın, Sercan; Aydın, Nedim Gökhan; Apaydın, Orhan; İşseven, Turgay

Kalehisar Archaeological Site, located near Mahmudiye Village in the Alaca district of Çorum, provides important insight into the Anatolian Seljuk period and 13th–14th century settlements in Central Anatolia. The main objective of this study is to determine the location and depth of possible buried archaeological remains within the archaeological site. This approach not only guides future excavations but also contributes to a more comprehensive understanding of settlement patterns and architectural practices during the Seljuk period. To achieve this, a comprehensive geophysical survey was conducted, employing magnetometry, electrical resistivity tomography and ground penetrating radar methods. Spectral analysis was used to interpret magnetic anomalies and identify potential buried features. Ground penetrating radar measurements provided high-resolution subsurface imaging, allowing for the detection of fine-scale stratigraphic variations and potential shallow buried remains. Electrical resistivity tomography helped identifying subsurface structures with contrasting resistivity down to 10-m depth. Integrated geophysical results revealed wall continuations extending from the excavation area, alongside other buried features such as ceramic/pottery kilns and a possible mosque in a few depths from the surface. These findings are consistent with Seljuk-era settlements and can aid future excavations by optimizing resources and preserving archaeological integrity.

Kayın, Sercan; İşseven, Turgay

The Eastern Anatolia is an active tectonic region where the collision between the Arabian and Eurasian plates take place. Due to the subduction of Arabian plate’s oceanic lithosphere under Eurasian plate, widespread volcanism observed in large areas began in Serravallian. There is no consensus in the literature for the tectonic evolution of the region. Therefore, there are many geological and geophysical studies conducted with the intention of explaining the tectonic evolution of Eastern Anatolia by geodynamic models. Our paleomagnetism study aims to reveal the tectonic rotations in order to better understand the development of the prevailing tectonism in the region from the volcanic rocks. Paleomagnetic samples were collected from 86 sites of the Late Miocene–Pleistocene volcanic rocks located at the north of Lake Van. Isothermal remanent magnetization studies show that magnetite is the mineral responsible for magnetization in most rocks, while both magnetite and hematite are responsible for the rest of the rocks. Curie temperatures and alteration degrees of rock samples were also determined by high-temperature susceptibility (HTS) studies. In some samples, titanomagnetite component was observed in the heating phase of the HTS measurements. The absence of this component in the cooling step indicates that Ti-magnetite is transformed into magnetite by alteration. The Pleistocene volcanics show counterclockwise rotation of R ± ΔR = 13.4° ± 3.8°. The Pliocene volcanic rocks were defined in four different groups: south of Erciş Fault, north of Erciş Fault, around Muradiye and north of Van. Also, the remarkable clockwise rotation is observed in the north of Van and near Muradiye R ± ΔR = 24.4° ± 17.0° and R ± ΔR = 6.9° ± 9.4°, respectively. In addition, counterclockwise rotation (R ± ΔR = 14.5° ± 6.1°) is obtained in the southern part of the Erciş Fault, while there is no significant rotation (R ± ΔR = 0.6° ± 7.4°) on the northern side. Late Miocene volcanic rocks show no significant rotation either (R ± ΔR = 1.8° ± 13.7°). Our new paleomagnetic results indicate that the left-lateral strike-slip Çakırbey Fault, located to the east of the Erciş fault and extending roughly in the northeast–southwest direction, may be active.