Facies Analysis and Depositional Environment of the Rus and Jil Formations (l- Eocene) in Najaf and Samawa Areas, Southern Iraq

Abstract

This research deals with study of facies and depositional environment of the lower Eocene Rus and Jil Formations at Najaf and Samawa Governorates, Southern Iraq. Two major lithofacies are recognized in the studied sections, namely carbonate and evaporite lithofacies. The carbonate lithofacies is divided into five microfacies whereas the evaporite lithofacies is divided into three Sublithofacies.From facies analysis the Rus and Jil Formations, in the study area, represent deposition in a shallow carbonate rimmed platform. The Rus Formation consists of two shallowing upward successions each of them represents peritidal environment, i.e., beginning with subtidal followed by intertidal and culminated with supratidal setting. The Jil Formation consists of two shallowing upwards successions representing shelf to peritidal environments. The Jil Formation grades from open marine to sabkha, i.e., beginning open marine followed by shoal, subtidal, intertidal and culminates with supratidal setting. The abundance of evaporites indicates that the climate during their depositions is arid to semi-arid.

Keywords: Facies, depositional environment, Rus Formation, Jil Formation, Sabkha.