Foraminiferal paleontology and sequence stratigraphy in the upper visean - serpukhovian deposits (Aladağ unit, Eastern Taurides, Turkey)

Demirel, Seda
The aim of this study is to investigate the Upper Visean substages, delineate the Visean - Serpukhovian boundary with calcareous foraminifera and interpret the foraminiferal evolution and sequence stratigraphical framework by using sedimentary cyclicity across the boundary section. For this purpose a 59,61 m thick stratigraphic section consisting of mainly limestone and partly sandstone and shale is measured in the Aziziye Gediği and Oruçoğlu Formations in the Pınarbaşı Region of Eastern Taurides. A detailed micropaleontological study has revealed presence of important foraminiferal groups namely, parathuramminids, earlandiids, endothyroids, archaediscids, biseriamminids, fusulinids, loeblichids, tournayellids and paleotextularids and 145 species and three biozones. The biozones are, in ascending order, Eostaffella ikensis – Vissarionovella tujmasensis Zone (Mikhailovsky; Late Visean), Endothyranopsis cf. sphaerica – Biseriella parva Zone (Venevsky; Late Visean) and Eostaffella pseudostruvei – Archaediscids @ tenuis stage Zone (Taurssk; Early Serpukhovian). A detailed microfacies analysis was carried out in order to understand the depositional history and sedimentary cyclicity and construct the sequence stratigraphic framework of the studied area. Three main depositional environments consisting of open marine, shoal or bank and tidal flat environments were interpreted based on the analysis of 12 major microfacies and 11 sub-microfacies types. Based on the vertical association of microfacies twenty-six cycles, two sequence boundaries and three sequences were recognized in the studied section and these two sequence boundaries, which correspond to the Mikhailovsky and Venevsky horizons, are the records of the global sea level changes during the Late Paleozoic Ice Age. Within this context Visean – Serpukhovian boundary falls in the transgressive system tract of the third sequence. The duration of cycles are calculated as 117 ky and interpreted as orbitally induced glacioeustatic cycles.