Stratigraphy and Microfacies Analysis of the Euphrates Formation: Insights from the Duhok Area, Northern Iraq

Abstract

The carbonate successions at Geli Besare, Duhok, northern Iraq, were studied in terms of stratigraphy, microfacies, and age determination. Three rock units were identified as the Euphrates, Dhiban, and Jeribe formations (previously grouped with the Pila Spi Formation). This study focuses on the Euphrates Formation, which unconformably overlain the Pila Spi Formation and conformably underlain the Dhiban and Jeribe Formations. The Euphrates Formation is subdivided into three main parts from the base upward: sub-conglomeratic-brecciated dolostone, chalky dolomitic limestone, and tough dolostone. These successions are notably dolomitized, recrystallized, and contain no macrofossils. The petrographic analysis show four main microfacies: Mudstone, Wackestone, Packstone, and Crystalline Dolomite, in addition to ten submicrofacies: dolomicrite mudstone, dolomitized fenestral mudstone, dolomitized mudstone, intraclastic wackestone, bio-peloidal wackestone, algal wackestone, ooilitic packstone, bio-intraclastic packstone, benthonic foraminifera bioclastic packstone, and peloidal packstone. The biostratigraphic analysis of the three formations reveals the presence of Borelis melo (Fichtel and Moll) var. curdica Reichel at the base of the Jeribe Formation, an indication of a late Early to Middle Miocene age. The field investigation, petrographic, and microfacies analysis collectively indicate that the Euphrates Formation was deposited in a broad tidal flat with a gentle slope, transitioning from a restricted to an open lagoonal marine environment. These findings conclusively confirm that the Early Miocene Euphrates Formation extends laterally across the Duhok area of northern Iraq.