Microbiostratigraphy and Paleoecology of the Abtalkh Formation based on foraminifera at Qareh-Sou section (southwest of Kalat-e-Naderi, NE Iran)

Abtalkh Formation has been chosen for microbiostratigraphy and paleoecology studies in the Qareh Sou section (south flank of Kalat-e-Naderi syncline، NE Iran). The measured thickness of Abtalkh Formation in this section is 1410m and consists mainly of marl and marly limestone. This study led to identification of 15 genus and 40 species of planktonic foraminifera in 5 biozones. Based on these fossils، the age of Abtalkh Formation in the Qareh Sou section is lowermost early Campanian to late Campanian. In addition، using the population variations of planktonic/benthonic foraminifera and epifaunal/infaunal benthonic foraminifera ratio، paleoecology conditions were determined. Based on these data، this formation is divided into 4 parts (P1، P2، P3، P4). During deposition of P1 and P3 sea level and food supply were high but the amount of oxygen was low; while during deposition of P2 and P4، sea level and food supply were low but the amount of oxygen and environmental energy was high.