Facies and depositional environments of the Devonian–Carboniferous succession of Iraq

Abstract

AbstractFacies associations and depositional environments of the Late Devonian–Early Carboniferous succession in Iraq have been studied in several boreholes from north and northwestern Iraq. The >400 m‐thick succession comprises the Kaista, Ora, Harur and Raha formations which are composed generally of mixed siliciclastic‐carbonate facies. The Kaista Formation consists of sandstones intercalated with siltstones and calcareous shale that were deposited in a mixed fluvial‐marine environment. The Ora Formation is composed dominantly of black shale with subordinate sandstone and dolomite deposited in a shallow‐marine, sub‐tidal shelf environment. The Harur Formation is composed mainly of dolomite with subordinate shale and was deposited in a deep sub‐tidal environment. The Raha Formation consists mainly of marine shales intercalated with sandstones and concluded the Kaskaskia megasequence. The depositional setting is considered as a subsiding basin with a wide geographic distribution. It extended from the Ora region in the extreme north of Iraq to west and southwestern Iraq and reflects an epicontinental or epeiric sea setting on a homoclinal ramp inclined to the southeast. Copyright © 2008 John Wiley & Sons, Ltd.