Facies Analysis and Depositional Environment of the Mulussa Formation at the Ga'ara Depression, West of Iraq

Abstract

A detailed study on the facies and depositional environment of the Mulussa Formation (Carnian-Norian) at the southern rim of Ga'ara depression, west of Iraq is carried out. The investigation is based on ninety six thin sections collected from five outcrop sections. This formation is dominantly composed of carbonate, marls and subordinate sandstone. Three lithofacies are recognized, depending on field description and microscopic examination, namely: dolomite, dolomitic sandstone and marl. The dolomite lithofacies is divided into four main microfacies, namely: dolomitized lime mudstone (four submicrofacies), dolomitized wackstone (two submicrofacies), dolomitized packstone (three submicrofacies) and dolomitized algal boundstone. Dolomitic sandstone lithofacies is two microfacies, namely: calcarenite and basal conglomerate of sandstone microfacies. By facies analysis, the deposition of Mulussa Formation took place in subtidal, lagoon, tidal flats, tidal ponds, tidal channels and coastal dunes. It generally represents deposition in shallow inner shelf environment with some continental influence in hot, arid to semi-arid climate.

Keywords: facies analyses, depositional environment, carbonate rocks, Mulussa Formation, Ga'ara depression, Iraq.