The Pontide belt in northern Turkey includes three major tectonic terranes, the Strandja Massif (SjM), and the Istanbul (ISZ) and Sakarya Zones (SZ) (Fig. 1). We present new age and geochemical data from ophiolites and ophiolitic mélanges within the Sakarya Zone and show that these mafic–ultramafic rocks are the remnants of Tethyan oceanic lithosphere formed in different tectonic settings. The main ophiolite occurrences investigated in this study along the Karakaya Suture (KS) are associated with the latest Triassic Cimmeride orogeny, and in the Küre–Yusufeli ophiolite belt are part of the Alpide orogeny. The Karakaya Suture Zone ophiolites in northern west Turkey are comprised mainly of the Denizgoren (Çanakkale) ophiolite, Boğreve;azköy (Bursa), Geyve (Sakarya), Almacık (Düzce) and Çele (Bolu) metaophiolites. The Denizgören ophiolite largely contains upper mantle peridotites, which are equivalents of the Permo–Triassic Lesvos peridotites and mélange units farther SW in the northern Aegean Sea. The Boğreve;azköy ophiolite includes serpentinite and metagabbro, and the Almacık and Geyve ophiolites display an almost complete Penrose–type sequence consisting of serpentinized upper mantle peridotites, cumulate ultramafic–mafic rocks, isotropic gabbros, dolerite and plagiogranite dikes, and extrusive rocks. U–Pb zircon dating of plagiogranite dikes from Çele has revealed an igneous age of 260 Ma, and 255, 235, 227 Ma from Almacık (Bozkurt et al., 2012a, b). Consistent with the previously published Permo–Triassic age, we obtained a 268.4±6.3 Ma U–Pb zircon age from a plagiogranite dike within the Almacik ophiolite to the west. This KS ophiolite belt containing the Çele, Almacık, Geyve ophiolites within the SZ extends westward into the Armutlu Peninsula and then into the Biga Peninsula (i.e. Denizgören ophiolite) and most likely connects with the remnants of the Triassic Meliata–Meliac ocean basin (Stampfli and Borel, 2002) in the Balkan Peninsula. The KS ophiolites also continue eastward within the Pontide Belt into the Elekdağreve; ophiolite (eastern Kastamonu) and then to the Refahiye ophiolite in NE Anatolia. Triassic granites in the SZ represent a magmatic arc that formed as a result of the northward subduction of the Izmir–Ankara–Erzincan oceanic lithosphere existing during the late Paleozoic through Cretaceous (Sarifakioglu et al., 2014) beneath the Pontides. We obtained a U–Pb zircon age of 231±2 Ma from a metagranitic intrusion into the Variscan basement of the SZ in the Kastamonu region of the central Pontides. This metagranite is enriched in LILE (Rb: 63 ppm; Ba:65 ppm; Sr: 200 ppm) and depleted in HFSE (Y: 12.58 ppm; Yb: 1.26 ppm; TiO₂: 0.2 wt.%; Nb: 7.6 ppm; Hf: 3.9 ppm), characterizing it as subduction–related calc‐alkaline pluton. Lead (3.9 ppm), U (1.6 ppm) and Ce (59 ppm) contents are interpreted as evidence for contamination by continental crust. The Küre basin to the north opened during the late Triassic to Liassic, following a backarc rifting episode in the central Pontides. Metabasic dike intrusions in the Devrekani metamorphic massif represent the first magmatic stage of this backarc rifting event. Whole‐rock ⁴⁰Ar‐³⁹Ar dating of the metabasic dikes has yielded cooling ages of 160.5±1.2 Ma. We infer that this age was reset due to thermal heating during the emplacement of the Middle Jurassic granitoids as the Küre oceanic basin was closing. The Küre ophiolite contains upper mantle peridotites and oceanic crustal rocks composed mainly of pillow–massive–breccia basalts, dacitic and rhyolitic lavas–tuffs, diabase dyke swarms, massive gabbros and a limited extent mafic cumulates. We obtained 182.6±1.9 Ma as a whole‐rock ⁴⁰Ar‐³⁹Ar age from a pillow basalt and a U–Pb zircon age of 171±1 Ma from the granitic intrusion cross‐cutting the peridotites. The easternmost representatives of the Küre ophiolite occur in the Yusufeli (Artvin) area in the eastern part of the Pontide belt. Here, oceanic crustal rocks are tectonically related to metamorphic rocks of the Variscan basement of the SZ. The ophiolitic crustal rocks contain isotropic gabbro and mafic and felsic dikes. Serpentinized upper mantle peridotites are scarce. Pillow lava basalts are overlain by a thick metasandstone–metashale association with locally foliated meta–lava and some manganiferous chert and mudstone interlayers. We obtained a U–Pb zircon age of 172.5±1.4 Ma from the granitic intrusion cross‐cutting the Yusufeli ophiolite and of 181.9±0.9 Ma from a felsic dike (plagiogranite) in the Yusufeli ophiolite. The Middle Jurassic granites are related to the closure of the Küre‐Yusufeli marginal ocean basin. The Küre and Yusufeli ophiolites have been previously interpreted as the remnants of the Paleotethys or the Intra‐Pontide Ocean. However, we posit that these ophiolites represent a marginal, short‐lived (∼10 Ma) ocean basin, which opened during the late Triassic through Liassic, and then closed in Dogger. This oceanic lithosphere is similar to the Evros ophiolite in the northeastern Greece in terms of its ages and geochemical characteristics.

Oil storage tanks must be designed to withstand dynamic and seismic loads. It is very important to ensure the safety of oil tanks with large volumes under earthquakes. During the earthquake, the land surface moves in all directions and as a result, the tank is exposed to vibrations. Especially the movements parallel to the land surface create vibrations in the tank and cause unexpected deformations on the tank walls. In this study, possible deformations that may occur in oil tanks with three different geometries under seismic conditions are investigated depending on their filling ratios. In the study, a package program based on the finite element method was used. By observing the sample responses such as acceleration and deformation of the tested models, the results were compared and confirmed with previous studies. The results revealed a clear relationship between oil level, tank shape and mode change. The higher oil level offered higher natural frequency in any case. The response spectrum model observed an increase when the oil level increased.

This study’s primary objective is to determine how boron-containing wastes from the stripping areas of the Emet–Bigadiç (Türkiye) boron deposits affect the mechanical performance of cement-based mortars and the effectiveness of weak soil improvement. The Bigadiç samples contain colemanite, calcite, dolomite, and quartz minerals, whereas the Emet samples predominantly comprise calcite. The wastes were incorporated into the cement matrix in two different forms: (i) solid-phase cement replacement and (ii) boron waste solution additive. Experimental findings demonstrated that replacing 10% of cement with a 4% Bigadiç-origin boron waste solution resulted in a compressive strength of 55.37 MPa after 7 days of curing, which is higher than that of the reference mixture. Also, the study revealed that the addition of 15% boron waste to weak soils increased the soil density to 1728 kg/m³ by filling micro-voids and enhancing intergranular interlocking. Due to this physical filling and chemical bridging effect, CBR value increased from an initial 4 to 6, providing a significant improvement in the soil’s deformation modulus and bearing capacity. Consequently, used boron wastes not only provide high mechanical performance in cement-based systems but also offer potential as an alternative additive material for sustainable and cost-effective soil stabilization applications.

Due to the increasing demand for infrastructure associated with rapid population growth, the demand for cement is constantly rising. The increase in cement production raises energy and raw material consumption, leading to environmental degradation, a rise in carbon dioxide and other greenhouse gas emissions. To minimize the environmental impacts caused by cement, industrial wastes such as blast furnace slag (GGBFS), fly ash, bottom ash, etc., agricultural wastes like rice husk ash, and materials like pumice and perlite are used as cement replacement materials in concrete production. In this experimental study, GGBFS was used as a cement replacement material at proportions of 20%, 35%, and 50%, and PP (PP) at proportions of 10% and 15%. Mortar specimens of size 40x40x160 mm were produced, and these specimens were subjected to standard water curing and curing in a curing room (70% humidity, 30 °C temperature) for 3, 7, 28, and 90 days. The compressive and flexural strengths of the hardened mortar specimens were then tested. Furthermore, in the scope of the study, the influence of PP on the internal curing, and thus the mechanical strengths at different ages, was examined as a solution to the curing problem that cementitious composites may face due to decreasing water resources associated with global warming.

A localized landslide that occurred on a specific section of the road to the Uluyazı Campus of Çankırı Karatekin University seriously threatened road safety and disrupted transportation continuity. In this study, the ground conditions of the landslide area were examined in detail. Soil parameters were determined through field observations, drilling, Standard Penetration Test (SPT) data, laboratory experiments, liquefaction potential, bearing capacity, and consolidation behaviour were analysed. The analyses showed that the soil was safe in terms of liquefaction and that the bearing capacity was at a level suitable for road construction and use. However, consolidation settlements and dissolutions in gypsum levels were identified as critical factors that could trigger landslides. To prevent landslides and ensure road safety, double rows of bored piles with a diameter of ∅120 cm, a length of 35 m, and spaced at 1.4 m intervals were connected with a cap beam. This engineering measure cut the landslide surface, limited road deformations, and ensured transportation safety. The study demonstrated the effectiveness of bored pile applications in formations where soil-water interaction was significant and offered an applicable solution for critical areas in highway engineering.