Paleodepth, bedrock and hydrodynamic energy of Oligo-Miocene deposits based on large benthic foraminifers, Eshger anticline, folded Zagros
Authors
1
Geology Department, Earth Sciences Faculty, Lorestan University, Khoram Abad, Iran
2
Department of Geology, Faculty of Science, Lorestan University, Khorramabad, Iran
Abstract
In the present study, a stratigraphic section of Oligo-Miocene deposits (Asmari Formation) in the Eshger anticline of Rostam County (folded Zagros) was selected. The thickness of the Asmari Formation in this section is 291 meters, which is mainly composed of thin, medium, and thick-layered limestones and thin shale-marl interlayers, and the Pabdeh Formation is gradually and continuously located at its lower boundary. Sampling of this section was carried out systematically with a sampling interval of one meter and finally 280 microscopic thin sections of the Asmari Formation were studied. Seven microfacies belonging to the outer ramp, middle ramp (distal and proximal parts) and inner ramp (semi- restricted lagoon and restricted lagoon) environments were identified. MF1, with its planktonic foraminifera, is an indicator of great depths, a soft and stable substrate, and low hydrodynamic energy. MF2 and 3, with their large benthic foraminifera and elongated and thin walls, are an indicator of low energy environments, soft substrate, and depths of 30-150 meters And MF 5, 6, having hyaline and porcelanose foraminifera with thick, lenticular shells, are indicative of shallower depths, higher hydrodynamic energy, and a hard, unstable bed.
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