Turhan Ayyildiz

Giant rhinoceros Paraceratherium and other vertebrates from Oligocene and middle Miocene deposits of the Kağızman-Tuzluca Basin, Eastern Turkey

A recent fieldwork in the Kağızman-Tuzluca Basin in northeastern Turkey led us to the discovery of three vertebrate localities which yielded some limb bones of the giant rhino Paraceratherium, a crocodile tooth, and some small mammals, respectively. These discoveries allowed, for the first time to date some parts of the sedimentary units of this basin. This study also shows that the dispersal area of Paraceratherium is wider than it was known before. Eastern Turkey has several Cenozoic sedimentary basins formed during the collision of the Arabian and Eurasian plates. They are poorly documented for vertebrate paleontology. Consequently, the timing of tectonic activities, which led to the formation of the East Anatolian accretionary complex, is not constrained enough with a solid chronological framework. This study provides the first biostratigraphic evidences for the infill under the control of the compressive tectonic regime, which built the East Anatolian Plateau.

Hydrocarbon potential of the Karapinaryaylasi Formation (Paleocene–Eocene) source rock in the Tuz Gölü Basin, central Anatolia, Turkey

In the Tuz Gölü Basin (central Anatolia), the Karapinaryaylasi Formation (Paleocene–Eocene) is represented by shale and sandstone alternation, conglomerates and lensoid limestones. The total organic carbon (TOC) results from most outcrops and the Karapinar-2A well samples show less than 0.50 wt%, and the hydrogen index (HI) and genetic potential values are very low. In the Aktas-1A, Aksaray-1 and Sultanhani-1 wells, the TOC content is generally lower than 0.5 wt% but can reach up to 1.50 wt%. Rock-Eval pyrolysis indicates that some intervals within the Karapinaryaylasi Formation possess good gas potential, with a total yield of up to 4268 ppm. The Paleocene–Eocene rocks are thermally immature to marginally mature with respect to Tmax, ranging from 420°C to 458°C, while vitrinite reflectance and spore colour index values range from 0.50% Ro to 0.88% Ro and 4 to 8(?), respectively. Microscopic investigations and the HI vs. oxygen index (OI) and HI vs. Tmax diagrams show that the samples contain Type III and Type II kerogen, which is often oxidized, together with reworked material. Gas chromatography and gas chromatography–mass spectrometry analysis results support these conclusions. Consideration of all the data indicates that the Karapinaryaylasi Formation (Paleocene–Eocene) could be the source rock for gas production in the Tuz Gölü Basin.

A rare natural gypsum ooide (Gypsolites) in an evaporitic playa lake of late miocene (?) to pliocene age in central Anatlia, Turkey

Gyposolites are found in the western part of Polatli town, Polatli-Sivrihisar basin, about 90 km from Ankara, Turkey. Gypsolites are observed in a transition zone between a siliciclastic marginal lake and an evaporitic inner lake. The ooide-bearing strata have a small to moderate thickness (10 to 50 cm), are laterally restricted, and partially exhibit a sandy appearance, including various amounts of volcanoclastic grain and mud pellets. They sometimes show micro-gradations, parallel or cross-laminations and rippled surfaces, in which macroscopically there are evidences of biogenic activity such as fossil tracks and burrows, but microbial activity is intensively present within the gypsum cortex, yielding micro-moldic porosity. Gypsolites fabrics suggest either (I) they occur under bacterial activity in local salines or short-lived ponds that occupied the low-energy part of the lake or (ii) weak currents or wind activity exert a significant influence on the gypsolites fabric. Some traces of microbial mats within the cortex and micro-gradations, parallel or cross-laminations indicate that the concomitance of bacterial activity and inorganic processes contributed to the construction of gypsum ooide structures in the Neogene evaporitic lake environment.

Water circulation near the mixed-water and microbiologic activity of the mesozoic dolomite sequence, and example from the Central Taurus, Turkey

Jurassic to Lower Cretaceous units, locating Central Taurus composed of thick dolomite with massive limestones beds and thinner dolomite beds with intercalated limestone are described. Various dolomite types include: Type I) dolomite formed as dolomicrite as mimetic replacement, Type II) dolosparite as a cloudy centre and clear rim in vugs, Type III) The planar-e texture dolomites are scattered in a micrite matrix, Type IV) Mottled dolomite present as zones of light colored dolomite crystals in a darker groundmass, Type V) Fracture and void filling dolomite (zoned dolomite, overgrowth and saddle dolomite). The investigated dolomites exhibit 0.1 to −2.0‰ PDB in δ18O values relative to their δ13C values (0.38 to 1.59‰ PDB) in the Middle Jurassic dolomites. The petrographic and isotopic characteristics support that dolomitization fluids were variable mixtures of fresh and marine waters related to changes in sea level. The late dolomitization phase was followed by diagenesis in the presence of meteoric fluids. During this period, calcite cements were precipitated within fractures. These calcites have characteristically low δ18O and δ13C values (−3.0 to −4.9 and −0.8 to −5.7‰ PDB, respectively).Within the Jurassic dolostone facies, traces of bacterial activity were observed. The morphology of the Jurassic dolomite indicates that bacteria were involved in the formation of the dolomite. This bacterial activity is indicated by dolomite surfaces with knobby textures and bumpy structure.