Original paper

Depositional environments and trace fossil assemblages in the Pabdeh Formation (Paleogene), Zagros Basin, Iran

Mohseni, Hassan; Behbahani, Reza; Khodabakhsh, Saeed; Atashmard, Zohreh

Abstract

This study focuses on interpreting the depositional environments in the Pabdeh Formation (late Paleocene-early Oligocene) in the Zagros Basin (W-Iran). It is based on field observations and measurements, thin section petrography, trace fossil analysis and organic matter (TOC % and kerogen type) measurements. Seven microfacies assemblages and two ichnoassemblages have been recognized. The Cruziana ichnofacies (Arenicolites, Chondrites, Planolites and Neonereites) formed under moderate energy conditions, the Zoophycos ichnofacies (Zoophycos and Chondrites) under lower energy and in deeper water conditions. Spatial relation ships of microfacies and ichnofacies suggest a distally steepening ramp with reducing conditions in oxygen depleted waters (TOC > 2.5%; kerogens type II, I and few type III) evolved into a middle ramp where marine currents had important impact on sediment reworking.

Keywords

pabdeh formationzagros basindepositional environmentichnofossilcarbonate rampturbidite facies