Browsing by Author "Gungor Yesilova, Pelin"

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Geochemical and Geostatistical Investigation of Upper Miocene Evaporites in the Polath-Sivrihisar Neogene Basin (Demirci Village, Ne Sivrihisar; Central Anatolia, Turkey)
(Tmmob Jeoloji Muhendisleri Odasi, 2007) Gungor Yesilova, Pelin; Tekin, Erdogan
The gypsum member of the upper Miocene aged Sakarya formation in the Polatli-Sivrihisar Neogene basin is represented by five different sub-lithofacies. These are: a) secondary massive gypsums b) primary laminated anhydrite c) secondary laminated brecciated-nodular gypsum d) clastic gypsum (gypsum arenite) and e) chevron selenitic gypsum. Among these, massive gypsum with iron -manganese bands separated by sparse sulphur crystals and primary laminated anhydrite with algal stromatolithic structures are important in respect of their formation mechanisms. The geochemical and geostatistical evaluation of different minerallization types from gypsum anhydrite samples of these sub-facies provide evidence of their possible source of origin. For this purpose 24 samples of different types including 13 major oxides, 15 trace elements and 13 rare earth elements were analyzed and from these results the correlation coefficient values for couple elements were determined and statistical graphics were prepared. After these geostatistical studies, three main groups of elements were identified. Among these: Group-I comprised SiO2 Al2O3, K2O, Rb, Sigma Fe2O3, MgO, MnO, As, V,TiO2 P2O5, Zr, Zn, Ni, Co and Cu, Group II comprised Ba, Sr, Mo, Pb, W, F, Au and Na2O and Group III comprised CaO and SO3 combinations. These combinations commonly show excessive vug-filling diagenetic clay minerals and/or carbonization within evaporites. On the other hand, the results of geochemical analysis of trace elements show higher values than the chemistry of evaporitic playa lake sedimentary environments. The reasons for these high values are considered to be: the fact that during the evaporation process the upper Miocene paleolake was under the influence of fresh ground water input, variation in climatic conditions for a short period of time (like dryness and wetness), limited reducing environmental conditions in isolated parts of the lake and post depositional hydrothermal dissolutioning. The geochemical and geostatistical evaluation of upper Miocene evaporites of the gypsum member of Sakarya formation have identified that these evaporites were deposited in a playa lake complex with different depositing lithologies (siliciclastics and carbonates) which were affected by paleoclimatic conditions, periodic terrestrial volcanism and syn-sedimentary tectonics.
Petrographic- Mineralogical Examination and Diagenetic History of the Paleogene Evaporites in Bulanik (Mus), Turkey
(Maden Tetkik ve Arama Genel Mudurlugu-mta, 2020) Gungor Yesilova, Pelin
Oligocene aged evaporite formations are observed in shallow sea-sabkha environments that develop in highly restricted conditions from sea in northeastern of the Mus basin. Evaporites are observed as alternated and intercalated with elastics and carbonates that developed under the control of factors such as climate, tectonism, volcanism and diagenesis. Evaporites consist of primary and secondary gypsum and minor anhydrite. In petrographic and minerologic examinations, secondary gypsum textures such as alabastrin, porphyroblastic and satin spar with anhydrite relicts, late diagenetic calcite, bitumen and bioturbation traces were detected. In SEM-EDS studies; celestine crstals, autogenic and detritic clay and quartz grains and euhedral dolomite mineral were observed. As a result of all these studies, the conditions and phases of the evaporites from the sedimentation stage to early diagenesis and late diagenesis processes of the evaporites were illuminated. Secondary gypsum consists of the origin of primary anhydrite and gypsum. From the diagenetic fluids released during the gypsum-anhydrite transformation, the late diagenetic calcite and by the interaction of the ions carried by the hydrothermal solutions to the basin with the groundwater were formed the celestite. Stream activity in the basin was determined by the presence of detritic minerals in gypsum minerals.
Post-Halite Gypsum Pseudomorphs With Evidence of Challenging Climatic Conditions and Diagenetic Replacement: a Study From the Southwest of Kağızman Basin (Eastern Anatolia, Türkiye)
(Maden Tetkik ve Arama Genel Mudurlugu-mta, 2024) Gungor Yesilova, Pelin
The study area is about the evaporitic-dominated Middle Miocene sequence situated in the southwest of the Ka & gbreve;& imath;zman Basin in Eastern Anatolia. The aim of this study is to investigate the formation conditions and diagenetic development of pseudomorph gypsum formed after halite. Pseudomorph gypsum formations are intriguing geological features found in terrestrial deposits. These formations are replaced by primary halite crystals during the very early phases of diagenesis, giving the appearance of halite crystals but being composed of gypsum. The development of these pseudomorphs is indicative of specific paleoenvironmental conditions. The fact that these gypsum pseudomorphs are found in shallow depths of the lake and are well-preserved, smooth-surfaced, and varying in size suggests that they were the result of intense evaporation and rapid fluctuations in the water and pH level. This evaporation likely led to a decrease in the lake level and changes in the concentration of saltwater over time. The correlation coefficient relationships and element concentration values of these gypsums show that these elements are both continental in origin and subject to microbial influence. These pseudomorph gypsum and the clastic materials (transported by fluvial activity) that were interbedded gave important insights into the hot, long-drought, and lowhumidity climate of the era and adapted to the Middle Miocene global warming conditions