Biostratigraphy and Paleoecological Study of Pabdeh Formation in Interior Fars, Zagros Basin, Iran

Abstract

The Zagros basin, which trends NW-SE, is covered by a sea during the Paleogene, resulting in deposition of the Pabdeh Formation in the deeper parts of the basin. The thickness of the Pabdeh Formation in Tang-e-Abolhayat is about 221 m and it consists of purple shale at the base, gray shale, marl and marly limestone with a few horizons of nodular limestone toward the top. Seventytwo samples were collected and processed for nannofossil studies. Based on the identified nannofossil zones the age of the formation in Tang-e-Abolhayat is Late Paleocene-Late Oligocene (NP9-NP24). Changes in the abundance of different genera over the studied interval have resulted in identification of three ecozones: Ecozone 1 is characterized by oligotrophic conditions with an abundance of warm water taxa; Ecozone 2 marks when conditions became more eutrophic and the abundance of temperate taxa increased; Ecozone 3 represents a return to oligotrophic conditions with an increase in warm water taxa.

Calcareous nannofossils of the late Eocene to early Oligocene from the Pabdeh and Asmari transition in Dezful Embayment (southwestern Iran): Evidence of a climate cooling event

“…In order to further investigate the EOB, the Eocene–Oligocene interval (including the uppermost part of the Pabdeh Formation and the lowermost part of the Asmari Formation) has been investigated, based on calcareous nannofossil data at the Marun oil field in the Zagros belt, Dezful Embayment, south‐west Iran. These two formations have been investigated from different aspects of palaeontology (Behbahani et al, 2010; Khavari Khorassani et al, 2014, 2015; Mahanipour et al, 2022; Mahanipour & Mutterlose, 2021; Mohseni & Al‐Aasm, 2004; Parvanehnezhad Shirazi et al, 2014; Sadeghi & Hadavandkhani, 2011; Senemari, 2014; Senemari & Sohrabi Molla Usefi, 2013). The main aim of the present study is: (1) to use calcareous nannofossil assemblages to determine the exact age of the strata and to determine the location of the EOB at (Pabdeh and Asmari formations) and (2) to determine the response of the calcareous nannofossil assemblages to the late Eocene–early Oligocene palaeoclimate events in this part of the Zagros Basin in Iran (Eastern Tethys).…”