Lower Cretaceous Orbitolinid (Foraminiferida) Record from the Southwest of Iran (Zagros, Shiraz)

Abstract

A biostratigraphic study was carried out in the Lower Creaceous (Aptian - lower Albian) Zagros basin, northeastern Shiraz located at southwestern Iran, allowing the recognition of one lithostratigraphic unit. The Lower Cretaceous shallow-water limestones on the northeast of Shiraz contains abundant and diversified orbitolinid foraminifera. A biostratigraphy, based on the orbitolinid taxa and their distribution, is proposed for the Aptian and Albian deposits in the Lower Creaceous (Aptian - lower Albian) Zagros basin, northeastern Shiraz located at southwestern Iran, allowing the recognition of one lithostratigraphic unit. Three orbitolinid biozones have been recognized: 1) Palorbitolina lenticularis Assemblage Zone in the Lower Aptian; 2) Mesorbitolina parva T otal Range Zone in the Late Aptian; 3) Orbitolina ( Mesorbitolina ) texana Assemblage Zone in the uppermost Aptian - lower Albian, the body of strata being characterized by a distinctive assemblage of Orbitolina ( Mesorbitolina ) texana and O . ( M . ) parva. The following taxa are the most abundant: Mesorbitolina texana , Mesorbitolina parva , Orbitolina sp., Pseudocyclammina lituus , Pseudochrysalidina conica , Pseudochrysalidina cf . arabica , Pseudocyclammina hedbergi , Praechrysalidina infracretacea , Cuneolina pavonia , Dictyocunus arabicus , Iraqia simplex , Vercosella laurentii , Protomarssonella trochus , Nautiloculina oolithica , and calcareous algae such as Salpingoporella dinarica , Trinocladus tripolitanus , Terquemella sp . and Lithocodium aggregatum - Bacinella irregularis.