Sedimentary environment and depositional sequences of the Oligocene Qom Formation in Central Iran based on micro-facies and microtaphofacies analysis

Oligocene deposits of the Qom Formation in central Iran were studied to reconstruct the sedimentary environment and depositional sequences based on microfacies (MF) and micro-taphofacies (MTF) analysis. A total of 310 thin sections (210 and 100 from Vidoje and Neizar respectively) were studied to differentiate eight microfacies (MF) and five microtaphofacies (MTF) types. These MFs are representative of a variety of depositional environments including restricted and semi-restricted lagoons as well as open marine settings. Overall, the distribution of MFs at the two sites suggests an open-shelf setting for the Qom Formation. Three complete third-order depositional sequences together with one incomplete sequence were identified. In the Rupelian stage, sea level changes in the Neizar and Vidoje areas were most likely affected by tectonics controlled by regional faults, whereas regional sea-level fluctuations of the south Tethyan Seaway and the Paratethys Basin controlled sea-level changes in the Chattian stage.