Microfacies Analysis and Paleoecology of the Oligocene Succession in a Central Tethyan Carbonate Platform, Zagros Basin, SW Iran

Abstract

AbstractTwo stratigraphic sections (Arjooieh and Firoozabad) of the Mymand anticline, located in the Interior Fars sub‐basin of the Zagros Mountains, were measured and sampled, in order to document sedimentological characteristics, microfacies types and paleo‐seagrasses indicators of the Oligocene succession (Asmari Fm.). Planktonic and benthic foraminifera and coralline red algae are the principal fossils from these strata. Foraminifera are represented by the following families: Soritidae, Peneroplidae, Austrotrillinidae, Alveolinidae, Planorbulinidae, Discorbidae, Lepidocyclinidae, Amphisteginidae, Rotaliidae, Nummulitidae and Globigerinidae. Nine microfacies types were recognized, namely planktonic foraminifera‐peloidal packstone (MF1), bioclast nummulitid/Nerorotalia/Amphistegina packstone‐grainstone‐rudstone‐floatstone (MF2), Neorotalia‐echinoid coralline red algae packstone‐grainstone (MF3), coral boundstone (MF4), coral/coralline red algae rudstone‐floatstone‐packstone‐grainstone (MF5), diverse imperforate foraminifera bioclast packstone‐grainstone (MF6), peloid wackestone‐packstone‐grainstone (MF7), fenestrated mudstone and microbial mats (MF8) and anhydrite (MF9). MF1 indicates an outer ramp, MFs 2‐4 represent a mid‐ramp and MFs 5–9 are interpreted as inner ramp environment. Paleo‐seagrass indicators consisting of foraminifera, hooked and tabular forms of coralline red algae and corals. They were identified in MFs 5 and 6, reflecting the presence of vegetated environments within the mid/inner ramp setting. The Mymand anticline was dominated by the outer ramp environment at the start of the Rupelian. Mid to inner ramp environments prevailed during the Rupelian. The Chattian corresponds to the spread of the inner ramp setting over the Mymand anticline.