Stratigraphy and Foraminiferal biozonation of upper cretaceous sediments in Southwest Sepid Dasht, Lurestan, Iran

Abstract

2 Abstract: In order to study lithostratigraphy and microbiostratigraphy of Tarbur and Amiran Formations in southwest Sepid Dasht (Lurestan), the stratigraphical section of Cham sangar was selected. Lithostratigraphical studies shows presence of limestone, dolomitic limestone, sandy limestone, shale and marl in this section. The existing index facies in this section include grainstone, packstone and wackstone. Microbiostratigraphical studies done on 67 thin sections from 77.3 m of Tarbur Formation sediments in Cham sangar section indicates the existence of 12 genera and 23 species of benthic foraminifers. Based on assessment of existing set of foraminifera, Omphalocyclus - Loftusia assemblage zone has been proposed for Cham sangar section. Micropaleontological studies suggest middle-Maastrichtian to late-Maastrichtian age for Tarbur Formation in southwest Sepid Dasht. The performed studies for the first time mention that in Lurestan province, Tarbur Formation with index lithology and fauna of Maastrichtian interbeds in clastic-conglomerate deposits of Amiran Formation base in a local tongue manner which indeed introduces age of Amiran Formation basal part as Maastrichtian.