Türkiye Jeoloji Bülteni

Abstract: This study is a palynological and stratigraphical investigation of E1 and E10 core samples from thesouthern part of Lake Erçek (Eastern Anatolia, Turkey). Core samples were taken by a gravity corer from differentwater depths. Deposits in the core samples include mostly laminated rhythmic sediments, massive and gradedlayers and a tephra layer from E10 core, representing different time spans because of the faulted ground of thelake. Tentative time scales of the core samples are based on pollen and tephra correlation with Lake Van deposits.According to the palynological investigations, palaeovegetation of Greenlandian is represented by Amaranthaceaedominant halophytic vegetation and semi-arid palaeoclimate conditions based on pollen analysis around Lake Erçek.The Meghalayan stage is mainly characterized by Poaceae-dominated steppe vegetation and increasing humanimpact according to anthropogenic pollen indicators. The Meghalayan palaeoclimate of Lake Erçek was more humidthan Greenlandian and is represented by maximum deciduous Quercus expansion in recent times around the LakeErçek area. 

Abstract: The present study deals with the systematic description of macro and miofloral analysis of Gangamopterisrajaensis and Glossopteris indica from the carbonaceous shale-coal bearing sequences of the Rajmahal Open CastMine, Rajmahal Basin, Jharkhand, India. The floral diversity, age correlation, and the paleoenvironment of the BarakarFormation were well described. Morphological analysis revealed the reticulate venation pattern, anastomosingof veins, and the absence of the midrib in Gangamopteris rajaensis. The recovered megafloral assemblages ofGangamopteris rajaensis and Glossopteris indica suggest a late early Permian (Artiskian-Kungurian) age for theBarakar strata of Rajmahal coal mine and the prevalence of a moderately warm climate during their deposition.Earlier the species was reported from the Barakar Formation of Damodar and Mahanadi Gondwana basins in India.However, this is the first detailed systematic investigation of this species from the Rajmahal Gondwana Basin,Jharkhand, India.

Abstract: The study investigated phosphate-rich sedimentary rocks in the Late Cretaceous Karababa Formation inthe Mardin-Mazıdağ region, which represents the northern part of the Arabian Plate. The stratigraphic successionis divided in three members as i) Karataş: ellipsoidal gray-colored, largely weathered, fossiliferous shelly micriticlimestone, ii) Ekinciler: dolomitic cherty limestone interbedded with marls, and iii) Evciler: argillaceous limestonewith common phosphatic horizons. Large numbers of hand samples, collected from the outcrop successions, werecarefully studied with optic microscopy (OM) and scanning electron microscopy (SEM). They indicate the presenceof optical isotropic pelletic apatite minerals (37% P2O5), bone fragments, fish teeth, and invertebrate fossil fragmentslike brachiopod shells in phosphorite rocks and micritic limestone. The phosphorites in the Karababa Formation areinterpreted to have been deposited in a very shallow, near-shore low energy environment. The X-ray diffraction  (XRD) method confirmed the presence of apatite (carbonate fluorapatite: CFA), calcite, quartz, rare feldspar,dolomite, and clay (smectite, palygorskite, illite, kaolinite, chlorite, sepiolite, mixed layered illite-vermiculite, andchlorite-vermiculite) in phosphatic, silicic and other carbonate rocks. Total trace element concentrations in apatiteminerals range from 2436 ppm to 2456 ppm, with total concentrations normalized to chondrite (ppm) higher thanNorth America Shale Composite (NASC) at 664.98 ppm for P, 208.33 ppm for Sr and 33.66 ppm for Y. Commonoccurences of apatite, palygorskite/sepiolite, and smectite clay minerals in various sections of the KarababaFormation were interpreted as authigenic minerals in the marine environment. However, occurrences of mixedlayered clay minerals were interpreted as a result of neoformation and/or transformation processes. The phosphateoccurences in the Karababa Formation are considered to form due to mineral formation processes occurring viabiogenic and biogeochemical activities that developed with the changes in sea level linked to tectonic movementsassociated with the evolution of the Neotethyan ocean during the Upper Cretaceous period.

Abstract: The Central Anatolian Crystalline Complex (CACC), consisting of metamorphic rocks, ophiolites, andmagmatic intrusions, is the largest metamorphic complex in Turkey. It is also one of the key areas for reconstructionof the subduction zones, accommodating the Africa-Europe convergence since the Cretaceous in the EasternMediterranean.The Ayhan Basin, chosen as the study area, is a supra-detachment basin that developed on the CACC. Ithas basin infill with an age ranging from Paleocene to Quaternary, interrupted by angular unconformities, and is expected to contain the whole geological record of tectonic mechanisms which have affected the region fromPaleocene to Recent times. Producing a well-defined lithological map showing the structural elements of the basinis very important to understand the geological evolution of the Ayhan Basin and also to determine the spatialand temporal effects of the triggering mechanisms which deform the CACC. For this purpose, optical satelliteimage (Landsat TM and ASTER) processing techniques (pan-sharpening, resampling, principal component analysis,decorrelation stretching, and band combination), which have a widespread application, were used in determinationof the lineaments and lithological units, having different reflectance values. After this, detailed lithostratigraphy andgeological mapping of the Ayhan Basin were created by field verification.Considering the reconstructed stratigraphy and the geological map of the Ayhan Basin based on field observationand remotely sensed data, it has a depositional system that starts with continental deposits before Lutetian, thencontinues with marine sediments during the Eocene, and again ends with continental deposits. When the deformationprocesses are evaluated based on the trigger mechanisms of the Central Anatolian Crystalline Complex’s (CACC)evolution, the northern and southern part of the CACC show clearly different processes. Accordingly, the boundaryof the impact zone of the subduction zones in the north and south of the CACC is located between the Çiçekdağ andAyhan basins.

Abstract: Kuşadası Bay, which is controlled by active normal faults, is located in an evolving graben in the westof the Western Anatolian Extension System. Gümüldür Fault (GF), which restricts Kuşadası Bay to the north, hasapproximately 30 km long, fragmented structure between Ürkmez and Ahmetbeyli. GF, which strikes N (50o-55o)W direction, forms a sharp morphological escarpment between Ürkmez and Ahmetbeyli starting from Paleozoicbasement rocks to Quaternary alluvium units. The dip angle of the fault planes increases to the west (40o-85oSW),and the fault is a dip-slip active normal fault with convex structure and geometry toward the northeast. To unravelthe Quaternary activity of Gümüldür Fault and the evaluation of the regional uplift, morphometric and kinematicanalysis was performed for the first time on the fault that includes well-preserved geomorphological markers.Quantitative measurement of morphometric indices such as mountain front sinuosity (Smf: 1.13-1.56), valley floor  width to height ratio (Vf: 0.10-1.00), percentage faceting Lf/Ls ([L: 4.75-88.35, S: 0.12-9.30]), asymmetry factor (AF:19-78 ), basin shape geometry (Bs: 1.05-5.98), stream length gradient (Hack) index (SL: 25-6094.44), hypsometriccurve and hypsometric integral (HI: 0.16-0.53) and rock strength and climate parameters indicate that the footwallof the GF has been uplifting toward the west with more than 0.5 mm per year. According to kinematic studies ofthe GF, which is geometrically composed of three parts, the region developed under the control of an extensionalregime oriented NNE-SSW. If it is broken in seperate segments, it has the potential to produce earthquakes witha magnitude of 6.12, 6,45 and 5.78, respectively. If considered as a single segment, it has the potential to produceearthquakes with a magnitude of 6.81 in Kuşadası Bay. For this reason, trench-based paleoseismological studies areneeded to reveal the past activity of Gümüldür Fault and to determine the seismic hazard level in the region.