Oligocene microfacies and sedimentary environment of the Asmari Formation at northwest of Deris village, west of Fars province: correlation with three other sections in Zagros Basin

In this disquisition, Oligocene (Rupelian-Chattian) microfacies and sedimentary environment of the Asmari Formation at the northwest of Deris village, located in interior Fars zone of the Zagros Basin have been interpreted. The coordinates of such section are N: 29o 41' 59'', E: 51 o 32' 26''. The Asmari Formation deposits in this section are divided into 5 lithological units and consist of 460 m thin, medium, thick and massive bedded, gray and cream to gray limestone, slightly dolomitic with nodular and marly interbedded. By study of hyaline benthic foraminifera genera and non-foraminifera, and also recognition of some properties such as skeletal ingredient associations and sedimentary textures of thin sections, 14 microfacies have been introduced for the Asmari Formation. Gradual perpendicular changes of these microfacies represent that settling the Asmari Formation deposits took place in a homoclinal rapm. This homoclinal ramp consists of middle ramp and inner ramp, that are separated by shoal environment. Middle ramp is recognized by presence and dominition hyaline benthic foraminifera, coralline red algae and echinoids. The most significant skeletal debris of inner ramp are porcelainous foraminifera. To compare the thickness, age and sedimentary environment, zonal correlation of the Asmari Formation done in Deris section with three other sections (Naura anticline, Dill anticline and Dehloran) in the Zagros Basin. This correlation represent that the age of the Asmari Formation gets younger to the deeper parts of the foreland basin of the Zagros.