Biostratigraphy of early Oligocene-early Miocene benthic foraminifera in Lorestan Zone, south-west Iran

Abstract

This study is about the microbiostratigraphy of the Asmari Formation in the Lorestan Zone, south-west Iran. Six biostratigraphical zones were defined after summarizing the available stratigraphical data and occurrence of the Early Oligocene-Early Miocene benthic foraminifera. The zones are: Nummulites intermedius, N. vascus Assemblage Zone (Ruplian, for the Laneh and Chenareh sections); Lepidocyclina-Operculina-Ditrupa Assemblage Zone (Chattian, for the Laneh section); Archaias asmaricus, Archaias hensoni- Miogypsinoides complanatus Assemblage Zone (Chattian, for Laneh and Chenareh sections); Elphidium sp.14–Miogypsina sp. Assemblage Zone (Aquitanian, for the Laneh, Chenareh and Sar Tang sections); and biozone Borelis melo curdica–Borelis melo melo Assemblage Zone (Burdigalian, for Chenareh, Sarkan and Sar Tang sections). The lower part of Asmari formation in the Sarkan section (from base to 38 m) has no index fossils, so we called it the Indeterminate Zone. The zones were successfully correlated with the biostratigraphical sachems in the Zagros Basin.