Türkiye Jeoloji Bülteni

Abstract: Two types of basins developed in the Western Anatolian extensional tectonic system during the MioceneQuaternary interval, supra-detachment and rift basins, in the form of a rolling-hinge mechanism. In this study,stratigraphic and structural data on the presence of a rolling-hinge model in the area between Buharkent-Buldan onthe northern edge of the Büyük Menderes Graben are presented for the first time and the geological evolution of thegraben is discussed. In the light of obtained field data, the Miocene-Quaternary sequences deposited on the northernedge of the Büyük Menderes Graben were evaluated under 4 main sedimentary packages, which are separated fromeach other by angular and/or intrabasinal unconformities. These are the Lower-Middle Miocene (1st Package) and the Middle-Upper Miocene (2nd Package) which were deposited in the supra-detachment basin, and the PlioQuaternary 3rd and 4th packages formed in the rift basin. The structural elements that provide the basin formationand deformation of the region are the Miocene Büyük Menderes Detachment Fault, the Pio-Quaternary GökdereFault, and the Holocene Buharkent Fault Segment that cuts the youngest graben basin-fill located in the most easternpart of the Büyük Menderes Fault System.The main fault contacts of the supra-detachment basins characterizing the Miocene period are represented bya structural boundary of gneisses and schists belonging to the Menderes Massif, which is a relict of the effectivecompressional tectonic products of the Eocene–Oligocene interval.Due to the effectiveness of low-angle faults in the Menderes Massif until the end of Pliocene, a high rate ofextension occurred; because of this, the crust thickness was reduced. As a result of cooling of the crust duringQuaternary, the supra-detachment basin system was replaced by a rift system and the Menderes Massif was dividedinto blocks along the high-angle boundary faults of the rift basin. Field observations and kinematic analysis revealthat tectonic structures on the northern margin of the Büyük Menderes Graben evolved from low-angle to high-anglenormal faulting, and were rejuvenated southward parallel to the basin propagation in a rolling-hinge model. Thus,the basin formation also evolved from being supra-detachment to the rift type.

Abstract: The pre-Jurassic metamorphic rocks of the Biga Peninsula can be evaluated as three maintectonostratigraphic units, which show significant differences from each other in terms of degree of metamorphism,deformation characteristics and tectonic settings. These are: 1) Kazdağ Unit, 2) Kalabak Unit, and 3) KarakayaUnit. The Kazdağ Unit forms the high-grade metamorphic core rocks of the Kazdağ Massif on the visible base of theBiga Peninsula. The Kalabak Unit and the Karakaya Unit are located on this high-grade metamorphic basement ascomposite tectonic slices and form the lower-grade metamorphic outer envelopes.The Kalabak Unit, which is the main subject of this paper, consists of the Dedetepe Formation, the SazakFormation, the Torasan Formation, and Devonian Çamlık metagranodiorite, which cuts all these units. In additionto lithological, stratigraphic and structural similarities of these metamorphic rocks, which are the outer envelopeof the metamorphic core in the Kazdağ Massif and also outcrop in other metamorphic massifs of the region suchas Çamlıca, Karabiga and Karadağ, their U-Pb zircon ages also show that they can be correlated with each other.According to the results obtained from U-Pb zircon dating, the maximum sedimentation ages of the protoliths for themetasedimentary rocks of the Kalabak Unit are in the range of 557-582 Ma. The crystallization age of the protolithfor the metabasites, which has primary relationship to these metasedimentary rocks, is 577 Ma. In addition, protolithcrystallization age of the eclogites, which are tectonic slices in these metasedimentary rocks, is 565 Ma. In additionto similar protolith ages, the fingerprint of a tectonothermal event at about 300-340 Ma is important in terms ofexpressing a common geological history for all samples.Formation environment and age of the metavolcanic rocks of the Kalabak Unit represent consistent andsignificant geotectonic environments. The Dedetepe Formation, which is at the bottom, represents a subductionmélange, the Sazak Formation represents an active continental margin and the Torasan Formation represents acoeval sedimentary sequence. These geotectonic environments developed during the late Precambrian-earlyPaleozoic period while the Proto-Tethys oceanic crust subducted to the south, under the Gondwanaland continent.These oldest rocks of the Sakarya Zone, together with the rocks they were spatially associated with during youngerperiods, were affected by repetitive deformations which resulted in their present position.

Abstract: In Neogene basins in the Aegean region of Turkey, the association of coal seams with bituminous shalesand/or bituminous marls is common. The association of humic coals consisting of terrestrial organic matter withbituminous shales/marls rich in sapropelic organic material is rather unusual. In order to investigate the causes ofthis unusual association, a lithological section in Seyitömer-Kütahya region was studied for its different properties. Lithological, petrographic, mineralogical and geochemical composition of sediments, chemistry and redox potentialof water-column, amount, type and maturity of organic material in sediments, depositional environment and organicfacies were investigated. The evaluation and interpretation of the analytical data resulted in differentiation oftwo intervals along the coal-bituminous marl transition. The four-meter-thick interval at the base of the section represents a period when fine clastics rich in terrestrial organic matter and even humic coals were deposited in a lowenergy fresh water environment with high redox potential The following section is represented by carbonate-richfine clastics, which were deposited as a result of enhanced chemical sedimentation in brackish to saline water Theseunits are rich in sapropelic organic material, indicating that reducing conditions still continued. Sedimentological and organofacies properties of the coal-bituminous marl transition indicate a lacustrineenvironment with fluctuating water level in general At the beginning the depositional environment was a balancedfill fresh water lake where coal and fine clastics were deposited under temperate and humid conditions suitablefor flourishing flora. The lake was then converted from time to time in a lake  with brackish water due to climatechanging towards drier conditions. Thus, material transport in the lake was reduced and chemical deposition was dominant This paleoclimatic change at the end of the mid-Miocene was the main cause of the transition from humiccoals to bituminous marls in the Seyitömer region.

Abstract: The purpose of the current study was to complete an important gap within the Bouguer map of Iraqimplemented by the Iraq Petroleum Company (IPC). In addition, the collected data were processed with recentgravity concepts and methods to establish a new regional geological image. A total of 868 gravity points weremeasured and corrected.The Bouguer anomaly map of the study area was initially drawn up with the parameters and equations used toconstruct the IPC map. The newly-produced map shows a very strong correlation with the old IPC results. A newBouguer map of the study area was then constructed using modern parameters and equations. A comparison betweenthe old and new maps illustrates the difference between recent and previous techniques.The isostatic residual map shows the presence of over-compensated areas close to Chia Gara and Mateen and spreadsto the Aqra zone with a negative value of up to -20 mGal. In contrast, there is under-compensation in the southernregions with positive isostatic anomalies of about 80 mGal. In the researched area there are zero compensation linesaround the larger structures (Chia Gara, Mateen, Mangesh, Aqra, Piris, and Perat). In order to draw up the crustalthickness map, the Moho discontinuity depth was determined using topographic and Bouguer anomaly grids of thestudy area. In addition, the upper mantle anomalies were calculated by continuing the isostatic residual anomaly to45 km upward and then removing the past isostatic residual anomaly, that was continued upward to 35 km. Severalqualitative approaches were used to isolate the regional and remaining anomalies to analyze the gravity data, with anoptimal upward continuation level of 14 kilometers generated for the large and small maps.

Abstract: The Gölmarmara Basin forms the northern branch of the Gediz Graben, which constitutes a series ofhorst-graben systems controlled by antithetic and synthetic normal fault steps in the Western Anatolia ExtensionalProvince. Although geology of this section is well known, it is not studied enough in terms of active tectonics andgeomorphology. The aim of this study is to reveal fault segments on the basis of Quaternary activity and structuralevolution of the Gölmarmara Fault forming the southern boundary of the basin.The NW-SE trending Gölmarmara Fault, which consists of the 7 km-long İsmetpaşa and 11 km-long Hacıbaştanlarsegments, has 26 drainage basins and 23 triangular facets in its footwall. Morphometric analyses (Smf, Vf, AF,HI, Shp, SL, Slip Rate) based on the digital elevation model were performed for these structures. According tocombined results of our morphometry and field studies, the İsmetpaşa Segment has higher uplift and activity thanthe Hacıbaştanlar Segment, and they are linked by a relay ramp developing during the evolution of a complete faultzone. It can be said that the Gölmarmara Fault, which was found to have passed through 3 phases from its formationto the present day, is an en-echelon fault similar to when it formed. Morphometric indices and field data indicatethat the Gölmarmara Fault is composed of medium-highly-active dip-slip normal fault segments and may causeearthquakes with a magnitude of Mw: 6.4. The Gölmarmara Fault, consisting of 2 geometric and 1 seismic segment,has uplift rate ranging from 0.179 to 0.518 mm/year (increasing at the center, and decreasing at the tips of the fault).These values are similar to uplift rates calculated for other active normal faults in the Gediz Graben.

Abstract: “Cappadocia” is the informal geographic name of a region in central Anatolia, which is knowninternationally due to its cultural and historical past, attracting attention due to well-developed fairy chimneysand tourism activities in and around the towns of Aksaray, Nevşehir, Niğde, Kayseri, Yozgat and Kırşehir. Recently,the term Cappadocia was used in the formation of a new government agency which aims to manage the utilizationand protection of the region. However, there is still no consensus about the boundaries of this region which causesdisagreements, as the name Cappadocia can reflect either a narrow region or cover a very large area. Here wediscuss the Cappadocia region and suggest boundaries based on the distribution of volcanic rocks sourced fromNevşehir-Acıgöl calderas, and Erciyes and Hasandağı stratovolcanoes formed since late Neogene to Quaternary.We propose the name “central Cappadocia” for the area characterized by various erosional features including thefairy chimneys.