Sürdürülebilir Kalkınma Amaçları
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- MakaleAçık Erişim2025Geochemical evaluation of black limestones in the Early Cretaceous platform carbonates of Gümüşhane (NE Turkey): An insight into petroleum source rock potential and palaeoenvironment conditions
Saydam Eker, Çiğdem; Arı, Uğur Volkan; Alemdağ, Selçuk
This study assesses the organic matter (OM) content, kerogen type, maturity, depositional environment conditions and sedimentation model of Early Cretaceous (Berriasian–Aptian) black limestones in NE Turkey using geochemical analyses, including Rock-Eval/total organic carbon (TOC), gas chromatography–mass spectrometry, gas chromatography, major and trace elements and stable carbon isotope of OM measurements. The investigated black limestones' TOC, hydrogen index and potential yield values range from 0.07 to 2.91 wt%, 76 to 636 mg HC/g TOC and 0.15 to 11.17 mg HC/g rock, respectively. These results indicate that the examined limestones have variable source rock potential, ranging from low to high. Tmax values, calculated saturated biomarkers and aromatic components suggest that the OM contained in the black limestones varies between thermally immature and mature, consistent with the potential index values. The OM found in the black limestone contained kerogen varying between type I and III. It is a composition of marine and terrigenous OM, as shown by the δ13C isotope values, biomarker components and n-alkane distributions and their parameters. This OM was deposited in a salinity water environment with marine–terrigenous (transitional) surroundings under oxic, suboxic to anoxic and arid–hot climate conditions. These findings provide critical insights for assessing the hydrocarbon potential of carbonate platforms in similar geological settings.
- MakaleYalnız künye2023Tor topography in Giresun mountains, Türkiye
Uzun, Ali; Aylar, Faruk; Zeybek, Halil İbrahim; Alemdağ, Selçuk
Tors are mound-like rock landforms, resistant to erosion, that may sometimes reach the size of several storeys of house by volume. They may develop in different climate regions and different rock types, led by granitic rocks. In this study, tors developed in granitic rocks around Yaylalı village linked to Kürtün county in Gümüşhane were investigated. The study area is located in the eastern part of the Giresun mountain range in northeastern Turkey, 2000–2300 m above sea level. The aim of the study is to determine the natural environmental characteristics in tor formation and to reveal the effect of bedrock on tor formation. During field studies, 18 tors were selected by noting location, size and structural features, and dimensions were measured. Thin sections were first made from the rock samples taken from the tors and then the mineralogical composition was investigated by modal analysis method. As a result of this analysis, it was determined that the bedrock forming the tors is granite. During the field observations, it was determined that the intersecting vertical joints supported the formation of castle-like tors, while the horizontal joints supported the formation of pita pile-shaped tors. There are also pseudokarstic shapes resembling kamenitza and karst pavement. In conclusion, joint sets causing local resistance differences directed the formation of tors, while excess slope affected surface erosion and suitability of climate conditions-controlled weathering rate.
- MakaleYalnız künye2023Natural Walls of Anatolia: formation and development of Diş Kayalıkları as a structural landform (Sivas, Türkiye)
Uzun, Ali; Aylar, Faruk; Zeybek, Halil İbrahim; Gürgöze, Serkan; Bahadir, Muhammet; Alemdağ, Selçuk
The Diş Kayalıkları is one of the largest and most striking examples of crests in the world and is located between Eskidere and Boğazören villages of the İmranlı district of the Sivas province in Türkiye. The crests, which resemble castle walls when viewed from afar, have a real wall pattern due to the right-angled crack system of the bedrock when viewed closely. This study aims at investigating the geomorphological features of the Diş Kayalıkları and determining how the geological and geomorphological evolution of the Diş Kayalıkları took place and how the current formation mechanism continues. In the region, the mid-latitude continental climate prevails with cold humid winters and warm dry summers. The bedrock consists of Miocene bedded deposits of different resistance, folded by young tectonic movements. Diş Kayalıkları was formed by selective erosion of less resistant terrain around a pack of resistant rock on the steeper southern slope of an asymmetrical anticline. It has a length of 4750 m in the approximately northwest-southeast direction, a maximum height of 30 m, and a width varying between 5 and 8 m. In the present morphological appearance of the Diş Kayalıkları, it can be stated that the structure formed after the tectonic formation process was eroded under the control of the local climate and crest formation was realized. In the following process, the crest experienced a polycyclic process where different landforms were formed. There are smaller landforms such as karren, cave and rock window on Diş Kayalıkları, and macrofossil beds in some places. This highly attractive geomorphosite, unknown to wider public, should be investigated from various scientific aspects and should be brought to regional tourism by making the necessary infrastructure and promotion studies.
- MakaleYalnız künye2023Excessive groundwater withdrawal and resultant land subsidence in the Küçük Menderes River Basin, Turkey as estimated from InSAR-SBAS and GNSS measurements
Yalvaç, Sefa; Alemdağ, Selçuk; Zeybek, Halil İbrahim; Yalvaç, Murat
Küçük Menderes River Basin (KMRB) is located in the western part of Turkey in the city of İzmir. The basin hosts about half a million people and 90% of the population makes their living from farming and animal husbandry. Most of the water needs for agricultural irrigation, animal husbandry, and drinking are met from groundwater resources in the basin. Since the water pumped from the aquifers cannot be naturally recharged by surface waters and precipitation, the groundwater level is rapidly receding and a decrease of up to 150 meters has been observed in the historical groundwater level time series since the 1990s. For this reason, land subsidence occurred in the basin and as a result of this, crustal surface cracks have formed and infrastructure and superstructure facilities have been endangered. To prevent loss of life and property that may occur in the future, it has become necessary to estimate the magnitude and the expansion zone of the land subsidence by carrying out geodetic monitoring studies in the region. In this study, the analyzes performed by Interferometric Synthetic Aperture Radar-Small Baseline Subset (InSAR-SBAS) and Global Navigation Satellite System (GNSS) methods to monitor land subsidence in the KMRB are presented. For this purpose, monthly 74 SAR images from 2017 to the end of 2022 were evaluated according to the SBAS procedure in the GMTSAR academic analysis software. In order to, both validate the InSAR-SBAS results and convert the deformation rate in the Line of Sight (LOS) to the ellipsoid normal direction, 3 periods of GNSS campaign were performed between 2021 and 2023 in 5 different GNSS stations and evaluated with the GAMIT/GLOBK software. According to the analyses, the land subsidence rate of up to −165 mm/year has been estimated in the KMRB, especially in the district centers of Bayındır and Ödemiş. In addition, unlike many studies, different rates and propagation of subsidence were determined in different parts of the basin depending on the aquifer type and precipitation. Monthly time series of the deformations were created and the behavior of the deformations and its relationship with the groundwater withdrawal and the lithological structure in the region was scrutinized. Thus, the spatio-temporal behaviour of the land subsidence and the associated geological factors were revealed.
- MakaleAçık Erişim2022Evaluation of potential rock falls with three-dimensional analysis: Example of Oltanbey and Hasanbey districts (Gümüşhane city center)
Alemdağ, Selçuk; Kara, Rasim Taylan; Bostanci, Hasan Tahsin
The central district campus of Gümüşhane, located on the Trabzon-Erzurum Highway, has a steep topography, and because of the effect of climatic and morphological structure, frequent rockfall events can cause loss of life and property from time to time. For these reasons, the slopes in some parts of the Oltanbey and Hasanbey districts of the central district of Gümüşhane, which pose a great threat in terms of rockfall potential, were chosen as the study area. In this study, three-dimensional rockfall analyzes were carried out using the RocPro3D program on the lines determined in the rockfall source zones with a high probability of rockfall. As a result of the analysis, it was determined that the rock blocks rolled from the O1, O2 and H1 source rock lines determined at the upper elevations of the study area threaten the settlements and road networks in Oltanbey and Hasanbey districts. With the 3D rockfall analysis, steel barrier was applied as a precautionary structure in the areas determined to be under the risk of rockfall, and the analyzes were carried out again considering the precautionary structures. By examining the results of the analyzes, the safest and most economical different barrier types have been proposed to eliminate the danger of rockfall.
- MakaleYalnız künye2021The effects of freeze-thaw cycles and block size on the use of the Gümüşhane Granitoid (Gümüşhane/Turkey) as building stone
Dağ, Serhat; Alemdağ, Selçuk; Kaya, Ayberk
The present study aims to examine the usability of the Gümüşhane Granitoid as a building stone taking into consideration the short-term freeze-thaw cycles and mean block volume. A total of 180 specimens were used in the study prepared from the block samples compiled from 10 different areas in the Gümüşhane (NE Turkey) provincial borders. Mean block volume was calculated about 8 dm3 during the discontinuity studies carried out on the Gümüşhane Granitoid; as a result of which, it was determined that the granitoids are suited for obtaining blocks. The annual freeze-thaw cycle map of Turkey was used for determining the number of freeze-thaw cycles to be applied on the rocks in addition to taking into account the weathering of monzogranites. A total of 25 freeze-thaw cycle tests were applied on the rocks with experimental studies repeated at every 5 cycles. It was determined following the freeze-thaw tests that significant changes have occurred especially in the strength and water absorption parameters of the monzogranites and that they have been affected negatively. This indicates that the monzogranites are not suited for outdoor use as building stone in regions such as the Gümüşhane province and regions with similar climate characteristics, but that they can be used in a lot of regions with more moderate climates. As a building stone, monzogranites can be used either as cobblestone, curbstone, or paving stone subject to their mean block volume. It is considered that the widespread of the Gümüşhane Granitoid may provide a substantial economical income to the country.
- MakaleAçık Erişim2020Assessment of acid mine drainage formation using geochemical and static tests in mutki (Bitlis, se Turkey) mineralization area
Gücer, Mehmet Ali; Alemdağ, Selçuk; Akaryali, Enver
In this study, geochemical analyses, as well as short-term contact leaching and acid-base accounting tests, were carried out to determine the occurrence of acid mine drainage (AMD) by static tests in the ore stockpile areas at the Mutki Cu-Fe-Cr deposit (Bitlis, SE Turkey). According to the short-term contact leaching tests, the high enrichment in trace element concentrations in ore-bearing samples, especially in potentially toxic metals such as Cr, Cu, Mn, and Zn, were directly related to sulphide and oxide mineralizations. The pH (3.27–4.05) values of water samples, together with the classification of the intracontinental water resources, indicated that the water quality is the fourth class. Leaching tests, paste pH (3.42–4.46) and sulphide-sulphur (3.9–13.4 wt%) values also suggested that there was AMD production potential in the mineralization area. The AMD production potential was supported by the high mobility of several elements, such as Fe, Mg, Cr, As, Cu, S, and Zn. In ore samples, net neutralization potential (NNP) and net potential ratio (NPR) values were less than –20 kg CaCO3 /t and 1, respectively. The basalts forming the basement rock of the stockpile area were characterized by permeable to slightly permeable properties that potentially increase the contamination risk of the groundwater due to seepage in the stockpile area. In order to prevent seepage in the stock area, geomembrane (synthetic waterproofing covers) should be laid at the base to ensure impermeability. The improvements planned in the stock area were modeled by the finite element method and seepage discharges at a depth of 5 m were determined as 1.34 × 10–17m3/s. Thanks to these planned applications, surface and groundwater pollution can be efficiently prevented.
- MakaleYalnız künye2020Medium scale earthflow susceptibility modelling by remote sensing and geographical information systems based multivariate statistics approach: an example from Northeastern Turkey
Dağ, Serhat; Akgün, Aykut; Kaya, Ayberk; Alemdağ, Selçuk; Bostancı, Hasan Tahsin
The aim of the present study was to produce an earthflow susceptibility map for the city center and environs of the province of Rize located at the Northeastern part of Turkey. The study area is the rainiest region of Turkey, and due to the triggering effect of precipitation earthflows are frequently observed in and around the study area. Besides this point, weathered rock units and steep topography accompany with precipitation for the occurrence of earthflow cases. Considering this point, an earthflow susceptibility mapping was inferred to be a necessity for the area. Parameters, such as lithology, slope gradient, slope aspect, topographical wetness index (TWI), stream power index (SPI), slope curvature, and sediment capacity index (LS) were considered to be earthflow conditioning parameters. A multi-temporal earthflow inventory map for a period of 4 years (2011–2015) was initially generated by way of remote sensing approach and field surveys. Earthflow susceptibility map was produced using the logistic regression method after which the produced susceptibility map was validated. The mapped earthflows were separated into two groups prior to modelling and validation. The first group was for training and the second group was for validation steps. The accuracy of the model was measured by fitting them to a validation set of mapped earthflows. Area under curvature (AUC) approach was applied for validation purposes. The prediction capability of the earthflow susceptibility map produced can be regarded as acceptable in accordance with the AUC values of 0.62 for the logistic regression model. Based on these results, the obtained earthflow susceptibility map can be used to mitigate hazards related to landslides and to aid in land-use planning for the Rize city center.
- MakaleAçık Erişim2016Stability assessment of high-steep cut slope debris on a landslide (Gumushane, NE Turkey)
Kaya, Ayberk; Alemdağ, Selçuk; Dağ, Serhat; Gürocak, Zülfü
The objective of this study was to examine the effects on the stability of slope debris of planned slope excavations around the vicinity of Gumushane Imam-Hatip High School in NE Turkey. To assess the geotechnical properties of slope debris along the determined cross-sections, four exploration boreholes with a total length of 100 m were drilled and undisturbed soil samples were collected. Slope debris is composed of two soil zones and its depth varies between 15 m and 21 m. It was determined from the experimental results that the soil class of the upper zone is CL (low plasticity clay) and CH (high plasticity clay) whereas the soil class of the lower zone is SC (clayey sand) and GC (clayey gravel). Peak cohesions of the upper and lower zones were 26.3 kPa and 10.2 kPa, and their peak internal friction angles were 16° and 24°, respectively. Limit equilibrium (LE) analyses for the slopes were evaluated using Slide v5.0 software for the pre-excavation, post-excavation, and supported cases. The results of LE analyses showed the existence of a landslide along the SW direction; the landslide would extend to cover the whole region if the excavation were to be performed without applying engineering measures. Finally, the precautions to be taken were determined and stability analyses for the supported case were evaluated. These analyses showed that the active lateral forces applied by the proposed retaining walls to the cut slope should be 8325 and 3103 kN, respectively.