Microfacies Analysis and Depositional Environment of the Middle Eocene Avanah Formation in Haibat Sultan Area, Iraqi Kurdistan Region

Abstract

The Avanah Formation (Middle Eocene) was studied in the Haibat sultan section at Bina Bawi Anticline, Northeast of Erbil city within the Iraqi Kurdistan region. The field observation indicated that the formation occurs as Carbonate interbeds within the lower and middle parts of the Gercus Formation, which consists mainly of light yellowish to creamy color, well-bedded, marly, and dolomitic limestone with some intercalations of sandstones and marls reaching about 32 m thick characterized by lateral variations in facies and thicknesses. A petrographic study of 16 thin slices of carbonate rocks indicated that most of the matrix is composed of micrite, with a few microspars. Foraminifers, dasycladacean green alge, and Ostracods make up the skeleton grains. Non-skeletal grains mainly include peloids, intraclasts, and extraclasts. Depending on detailed microfacies analysis in the current study, five main microfacies and fourteen submicrofacies were discovered. The total of all petrographic, facies and textural investigations indicates that the Avanah Formation in the Haibat Sultan area was deposited in the shallow marine inner platform within subtidal, intertidal, and supratidal environments