Biostratigraphy and paleo-ecological implications in microfacies of the Asmari Formation (Oligocene), Naura anticline (Interior Fars of the Zagros Basin), Iran

In this research, biostratigraphy and paleo-ecological implications related to the carbonates of the Asmari Formation located at the Naura anticline, Interior Fars of the Zagros Basin, Iran, are discussed. The Asmari Formation at the study area is Rupelian–Chattian in age. Age was determined by the occurrence of 22 genera and 41 species which led to identification of four faunal assemblages: (1, Globigerina–Tuborotalia cerroazulensis–Hantkenina; 2, Nummulites vascus–Nummulites fichteli; 3, Lepidocyclina–Operculina–Ditrupa; 4, Archaias asmaricus–Archaias hensoni–Miogypsinoides complanatus). Based on faunal associations and biofacies analysis with emphasize on large benthic foraminifera and coralline red algae communities, the following paleo-ecological factors are defined for deposition of the Asmari Formation at the study area: water salinity of 34 to more than 50 psu, depth zones of 0–35 m of inner and middle part of proximal open shelf, 35–150 m of middle open shelf and more than 200 m of outer open shelf, water temperature of 18–25°C in a tropical to sub-tropical environments, oligophotic to near mesotrophic conditions and grain association communities of foralgal and rhodalgal.