Türkiye Jeoloji Bülteni

Abstract: The hydrocarbon-producing Midyan Basin  is located in northwestern Saudi Arabia and is surroundedby the Proterozoic igneous basement of the Arabian Shield. It includes thick hydrocarbon-producing sedimentarysequences deposited in half-grabens that formed during rifting of the Red Sea and the gulfs of Suez and Aqabain the Early Miocene  (23.3 Ma). The early syn-rift succession consists of arid alluvial fan sediments and playa evaporates followed by shallow marine carbonates. The late syn-rift sequences consist of  progradational deep seaturbidites and Alpine-type glacial deposits indicating strong vertical uplift during the climax of the rifting (19 Ma). The post-rift succession overlies the late syn-rift successions and consist of shallow marine marls and evaporites. The aim of this study is to examine the hydrocarbon potential of the turbidite sandstones and the formation of varioustypes of glacial deposits in the Burqan Formation. This study also encompasses the importance of various geologicprocesses in order to understand their significant influence on the geometry continuity and reservoir quality of oiland gas producing genetically different sandstones in the subsurface of the Burqan Formation in the Midyan Basin. The Alpine-type glacial deposits provide an excellent opportunity to study the presence of continuous vertical and lateral facies variations between true glacial glacio-fluvial and glacio-marine deposits in the direction of sediment transportation.  Unsorted moraines deposited in the deep and U-shaped glacial valleys occupy the northwestern partof the basin. They pass gardually in glacio-fluvial sandstones. that contain large polished and striated boulders.  Inthe southeastern part of the deep basin , the glacio-marine deposits are associated with deep sea turbidites and pelagicshales. Many stratigraphic and sedimentologic sections were measured from well-exposed outcrops in every partof the basin to establish various depositional environments. A large number of sandstone samples was collected toexamine their reservoir quality.

This study determined the geochemical properties of phyllosilicates in the Upper Palaeozoic-Lower Mesozoic metamorphic units outcropping from west to east in the vicinities of Göksun, Afşin and Ekinözü towns in the north of Kahramanmaraş province in the westerly part of the Eastern Taurus mountains. Geochemical examination of phyllosilicates (major and trace elements, stable isotope) was carried out on pure K-micas and illite/K-micas separated from low-medium grade metamorphic samples. According to the main oxide composition of the phyllosilicates, illite/K-micas from the areas of Afşin and Göksun contain higher SiO2 and Al2O3 and lower MgO, Fe2O3, MnO and Na2O compared to those in the area of Ekinözü. The minerals represented by schists in the Ekinözü K-micas are close to having a biotite-celadonite composition while those with phyllites in Afşin and Ekinözü are close to muscovite composition. Chlorites have a trioctahedral composition between chamosite and clinochlor. Illite/K-micas with both trioctahedral and dioctahedral characteristics show a composition between muscovite and biotite (biotite-celadonite, muscovite-phlogopite, muscovite-ferriphengite, muscovite-ferrobiotite, Al-phlogopite-Alannite) in general. In the trace element content of phyllosilicate minerals, transition metals and granitoid elements are at high concentrations while other elements, especially elements with low (LFSE) and high field strength (HFSE), display low concentrations. In the chondrite-normalized trace element content of phyllosilicate minerals, chlorites have higher values compared to K-micas and trioctahedral K-micas show lower values compared to dioctahedral K-micas. Rare earth element (REE) distribution of chlorite and sericite/K-mica minerals is normalised to chondrite and North American Shale Composition (NASC); the dioctahedral K-mica of Afşin region has the highest depletion, while the trioctahedral mica of Ekinözü has the highest enrichment. The oxygen and hydrogen isotope composition of the phyllosilicate minerals show that they are in the hypogene region, which represents high temperature and deep environment conditions. The oxygen and hydrogen isotope values of sericite/K-mica and chlorites indicate that the formation temperatures of these minerals varied between 375 and 500 °C. 40Ar/39Ar radiometric age data for the metamorphic rocks show that the metamorphism developed during the Upper Cretaceous (Santonian-Campanian) in the Afşin and Göksun regions and the Lower-Middle Eocene (Ypresian-Bartonian) periods in the Ekinözü region. 

Abstract: Porosity and density information were taken from five well logs scattered in East Baghdad oil field. Newempirical equations (porosity-depth, density-depth) were established for all the geological formations within theTanuma-Ahmadi interval. The correlation coefficient (R) of these equations derived for each formation ranged from0.04 to 0.61 which was attributed to variable lithological effects.The depth information for (126) velocity analysis sites covering the field were used to apply those new equations.After the new empirical equations were applied on the whole field, porosity and density contour maps for theperiod (Tanuma-Ahmadi) were produced. The locations of high porosity zones were identified and related to thecompaction and petroleum distribution in the field.

Abstract: The Tauride fold and thrust belt formed during ~N-S convergence between African and Eurasian platessince Cretaceous time. This movement led to the development of a complex morpho-tectonic structure, so-called‘Isparta Angle’ during the early stage of the Neogene time. In Miocene time, the western and central Tauridesand the inner part of the Isparta Angle became overlain by marine sedimentary basins which are characterized byclastics and carbonates. Aksu Basin which is determined as study area is one of these marine basins and is locatedin the center of the Isparta Angle. Therefore, Aksu Basin contains the geological records of the crustal deformationoccurred during the Neogene period.The sedimentary infill of the Aksu Basin is mainly characterized by marine clastics with more than 1 km thickfrom the Middle Miocene to Pliocene. The pre-Pliocene basin infill was subjected to intense deformation. Sedimentarysequence of the Aksu Basin starts with Burdigalian-Langhian Oymapınar Limestone which unconformably overliesthe basement unit. The lithostratigraphy in the north is different from that of the south of the basin. The youngestMiocene unit in the north of the basin is the Tortonian aged and the units deposited between Tortonian and Pleistoceneis missing in the sequence. On the other hand, the sequence is more complete in the south of the basin. In additionto lithostratigraphic features, the structural elements which are forming the Aksu Basin are also carried out duringthis study. These are the Aksu and Kapıkaya thrusts. Field observations and results obtained from the kinematicmeasurements along the key structural zones show that Aksu Basin developed through four different tectonic phases.While the first phase is ~E-W extensional phase which is related to opening of the basin, the second phase is ~N-Scompressional Lycian phase. The third phase is ~E-W compressional (Aksu) phase, which is the most prominentphase in the basin. N-S extensional phase is determined as the fourth and the last tectonic phase.Under the light of whole data, presence of the E-W shortening which is active between Serravalian and EarlyPliocene in the center of the Isparta Angle is interesting given the plate tectonic setting driven by N-S convergenceof the Africa and Eurasia. The seismic tomography images of the mantle below the Isparta Angle indicates that thereare two separate slab segments (Cyprus and Antalya slabs). Therefore, an important impact of the Antalya slabshould be expected in the Mio-Pliocene and even modern evolution of the Isparta Angle and the uplift of the Taurides.

Abstract: The Permo-Carboniferous depositional sequence of Lower Gondwana in Sikkim Lesser Himalaya wasinvestigated through an integrated approach of lithological, petrological, and geochemical studies. Lithologically,it is characterized by glacial diamictite at the base and shale-sandstone facies at the top of a sequence which isinterpreted as a glaciomarine deposit. Coarser sandstone and massive diamictite composed of quartz, feldspar,muscovite, zircon, and other lithic fragments are observed in thin section. Geochemistry of all studied samples fromthe Rangit Pebble Slate Formation shows the dominance of silicon dioxide compared to other elemental oxides.The tectonic discrimination diagram positively infers passive margin sedimentation from a felsic-rich provenance.Chemical Index of Alteration was used to depict the weathering trends of all studied samples which reflect paleosedimentation under humid to sub-humid climatic conditions.