Facies analysis and depositional environment of the Geli Khana Formation (Middle Triassic), Northern Iraq

Abstract

The Middle Triassic Geli Khana Formation is one of the important formations for the opportunity to study the Anisian–Ladinian facies and depositional environment in northern Iraq. Two sections (outcrop and subsurface) were selected to study the litho- and microfacies of the Geli Khana succession and to interpret its depositional environment. The formation is divided into five lithofacies (A–E) comprising dolomite, dolomitic, and marly limestones; calcareous shaly and marly limestones; limestone with dolomitic and marly limestones; black shales; and evaporites. Five microfacies were recognized, these include mudstone, silty mudstone, graded mudstone, oyster (bioclastic) wackstone, and laminated silty oyster packstone microfacies. Generally, the studied succession represents shallow reducing marine environment with peritidal carbonate facies in which three environments, supratidal, intertidal, and subtidal, were recognized. The deeper subtidal environment dominates in the northern parts of the basin while the shallower supratidal is common in the southern parts.