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. The Orbitolinids are well expand in Albian strata (Kazhdumi Formation) which are co‐existed with other agglutinated larger Foraminifera and calcareous algae. The basement faults of the Coastal Fars area affected the studied strata during Albian time. Rapid transgression caused the occurrence of plankton and reappearance of Orbitolinids was function of rapid regression during Late Albian age. Discoidal test of Orbitolinids are well expand in lower portion of the Albian sequence, whereas the conical type are distributed in the upper part of Kazhdumi Formation.