Larger benthic and planktonic biostratigraphy and facies of Albian sediments in Coastal Fars Zone (Zagros area, south-west Iran)

A total of 64 samples were collected from the Kazhdumi Formation (Albian) of south Zagros Basin (Coastal Fars Zone) in order to study the biostratigraphy and analyse the lithofacies. Stratigraphic distribution of identified larger benthic and planktonic foraminifers has confirmed the presence of three successive biozones: Mesorbitolina subconcava-Orbitolina discoidea Zone, Favusella washitensis Zone followed by an upper Conicorbitolina conica-Mesorbitolina parva Zone. Generally, orbitolinids are well developed in the Albian succession in the studied section, whereas the stratigraphic distribution of planktonic foraminifers is more restricted, dominating the Favusella washitensis Zone. Nevertheless, microscopic investigation recognizes five microfacies consisting of extraclast-foraminifer packstone, peloid-intraclast Orbitolina wackestone, foraminiferal plankton wackestone, intraclast-Orbitolina grainstone, and coral-rudist wackestone, which indicated a shallow water carbonates palaeoenvironment (intertidal, lagoon, bar) and open marine. The alternation of both planktic and benthic foraminifera through the Kazhdumi Formation confirms a rapid transgression and regression in the studied section during Albian time, which is attributed to Kazerun basement fault behaviour in the mentioned time interval.

Automated summary

The results of the study show that the Albian Kazhdumi Formation in the south Zagros Basin has unique characteristics in terms of biostratigraphy and lithofacies, with three successive biozones and rapid transgression and regression processes. Microfacies analysis revealed the features of shallow water carbonate paleoenvironment and open marine environment.