The regional facies analysis and depositional environments of the Oligocene and Lower Miocene deposits; Zagros Basin, SW of Iran

Abstract

A regional transect is selected to study the paleoenvironment of the Oligocene and Lower Miocene deposits in the Zagros Basin (Persian Gulf Foreland Basin to the High Zagros). This study rebuilds the sedimentary environments and paleogeography of the Zagros basin deposits in the Oligocene and the Lower Miocene. A transect consists of two stratigraphic subsurface sections at the Persian Gulf Foreland Basin, five stratigraphic subsurface sections at the Dezful Embayment, two stratigraphic outcrop sections at the Zagros Simply Folded and one exposure section at the High Zagros. The sediments are included Asmari Formation and the Pabdeh Formation. Lithostratigraphy studies show that the Pabdeh Formation has been composed of an alternation of marls and medium-bedded argillaceous limestone. The Asmari Formation is generally composed of medium- to thick-bedded limestone. Micropaleontology studies offer Early Oligocene for Pabdeh Formation and Early–Late Oligocene to Early Miocene age for Asmari Formation. Variety in fabrics, textures and fauna features has produced 13 microfacies and based on geometry, lateral and vertical facies relationships, the homoclinal ramp is proposed for the Oligocene and Lower Miocene deposits. Hence, corresponding to this research, the Rupelian sedimentation has occurred in the Dezful Embayment and Zagros Simply Folded, so that a systematic progradation suggests from Zagros Simply Folded (N/NE) (Asmari/Pabdeh Formation) to the Dezful Embayment (S/SW) (Asmari carbonate system). Following a regression system during the Late Oligocene to the Early Miocene, continuing sedimentation uniformly has been felt out in the shallow water system throughout the study area.