Microfacies analysis and Paleoenvironment Interpretation of Upper Oligocene Azkand Formation in Western Iraq

Abstract

This paper deals with the microfacies and paleoenvironment interpretation of the Azkand Formation at the high Euphrates river cliffs in north-western Iraq. In this study, the main components are dominated by the coexistence of large benthic hyaline perforated walls (Nummulitidae, Lepidocyclinidae, Amphisteginidae, Miogypsinidae, and Rotaliidae) and porcelaneous imperforate walls (Miliolidae, Peneroplidae, and Alveolinidae) with minor components of small benthic foraminifera. Other fossils are dominated by coralline algae, corals, bryozoans, mollusks, and shell fragments. These microbiota are considered beneficial in the biofacies analysis and recognition of paleoecology. On the basis of large benthic foraminiferal assemblages and microfacies features, eleven microfacies types have been recognized and interrelated. They indicate two depositional environments interpreted as shallow inner- to middle- ramp environments. The shallowest part in the studied section occurs in the photic zone which is characterized by the association of miliolids, peneroplids, and alveolinids. The middle ramp is classified into two shallow middle ramps characterized by dominant miogypsinis amphisteginids, and rotaliids, while the deeper middle-ramp setting is dominated by coralline algae along with nummulitids and lepidocyclinids.