Depositional Properties of the Middle Miocene Fatha Formation, in K Oilfield, Southern Iraq

Abstract

The Fatha Formation, formerly known as the Lower Fars Formation, was deposited in a shallow basin, southern Iraq during the Middle Miocene. By using the description of the cores, we found large heterogeneity in the lithology; contains a mixing of limestones, mudstone, marl, marly limestone, sandstone, and gypsum, or anhydrite. In this study, the Fatha Formation was divided into three main units according to lithofacies, namely, marl, marl-anhydrite, and limestone, in addition to, the presence of thin evaporitic and sandstone layers along with the formation but thicker with marl. X-ray diffraction and SEM tests which are accurate methods to identify the mineralogy enable inference of a high percent of the dolomite, calcite, and anhydrite; this may be attributed to the formation environment, In addition to the presence of some clay minerals such as illite and palygorskite. The petrographic details, microfacies analysis, and depositional environment studies led to recognition of four main microfacies including mudstone, wackestone, packstone, and grainstone; and nine sub microfacies were deposited in a shallow part of the inner ramp at three zones: peritidal, lagoon, and shoal.