Systematics and paleoenvironment of the Late Oligocene (Chattian) age ostracods from South Tafresh, Urumieh -Dokhtar Zone

A stratigraphic section was selected in East Garkan in order to study the paleontology of the Qom Formation ostracods in Urumieh -Dokhtar Zone. In this section, Qom Formation is gradually located on the clastic rocks of the Lower Red Formation and with disconformity under the Upper Red Formation. A total of 10 species of 14 ostracods genera were identified. The common stratigraphic range of these ostracods and the presence of accompanying foraminifera confirm the Late Oligocene (Chattin) age for the desired layers. The ostracod and foraminiferal assemblage from the studied section shows that the Qom Formation has accumulated in a warm and oxygen-rich environment. Based on the study of 60 samples found from the studied section, two sedimentary environments of the estuary (including alluvial channels, barrier; central basin and intertidal) and shelf (including inner, middle and outer shelf) were identified. The ostracods are spread in the middle of the side bay and the outer ramp.