Comprehensive Sedimentological Study of the Danian Aaliji Formation from the Duhok Area, Northern Iraq

The Danian Aaliji Formation exposed in the Bade section of the Duhok area, north of Iraq, represents a significant lithostratigraphic unit for the early Paleocene deposits in the region. It is 20.9 m thick and is composed of light brown-grey marls, shales, and some thin beds of limestone. Stratigraphically, the Aaliji Formation deposited immediately following the Cretaceous-Paleogene (K-Pg) boundary, separated from the Upper Cretaceous tough blue marlstone of the Shirnaish Formation by thin laminar of the meteoritic ejecta spherules conformably, while its upper limit ends unconformably with the Paleocene green-olive clatsitics of the Kolosh Formation marked with 30 cm tough, recrystallized limestone bed with rich content of glauconite, iron oxides, and Thalassinoides. Detailed microfacies and lithofacies analysis of the Aaliji Formation reveals three main microfacies (Aa3: globular planktic foraminiferal lime wackestone; Aa4: bioclastic-globular planktic foraminiferal packstone; Aa5: bioclastic lime grainstone), in addition to two lithofacies (Aa1: soft shale; Aa2: calcareous shale). The presence of these microfacies within the formation suggests that Aaliji Formation deposited in the middle-outer shelf environment with some extension to the upper bathyal condition. This study contributes to the broader understading of the early Paleocene sediments in northern Iraq.