Paleogeographic implications of the Permian shallow marine carbonates in the eastern Lake Van region (eastern Turkey): Foraminiferal biostratigraphic and sequence stratigraphic constraints

摘要

The study focuses on the Middle Permian recrystallized limestone succession, previously considered as Triassic, at the eastern parts of Lake Van (eastern Turkey) representing the northern margin of Gondwana. The Middle Permian successions in the region are mainly composed of slightly metamorphosed, recrystallized limestones. The shallow-water depositional settings of the studied units are characterized by the relative dominance of smaller foraminifers and rare occurrence of fusulinids. Middle Permian foraminifers recorded from eastern Anatolia are typically Tethyan assemblages for the Capitanian (Guadalupian) age. Detailed microfacies analysis by textural analysis and faunal assemblages have been undertaken throughout the studied sections. The Capitanian carbonates of the region are mainly characterized by six major microfacies types representing shallow marine environments, ranging from foreshoal environment to shoal and backshoal environments. Within the scope of sequence stratigraphic interpretations, vertical stacking patterns of these microfacies types reflecting different depositional environments reveal the presence of two third-order depositional sequences, each of which consists of a transgressive systems tract and a highstand systems tract. Within the context of sequence stratigraphy, the microfacies changes point out the relative sea-level fall towards the upper part of the sections, coinciding with the onset of a regression recorded worldwide in the Capitanian.