AN INTERFINGERING OF THE UPPER CRETACEOUS ROCKS FROM CHWARTA – MAWAT REGION, NE IRAQ
The Upper Cretaceous interfingering sequence of Chawrta – Mawat region have been described, and analyzed for their stratigraphy, and paleontology. These results are interrelated with respect to the characteristics of the depositional environment, the faunal variation and paleogeographic setting. The interfingering sequence is represented by the Tanjero Formation and Aqra Formation. This study points out a general variation trend both laterally and vertically from deep-flysch facies to reefal facies, that is from the margin of the carbonate platform to the central part of mobile trough through a transitional zone' between them. Several genera and species of macro and micro fauna are identified, from complete forms and thin sections. The giant Pelecypods (especially Rudist), gastropods with the echinoids, cephalopods, corals, brachiopods are the most common macrofossils, while the dominated large foraminifera are: Loftusia, Omphalocyclus, and Orbitoides. Micro and macro fauna testifies to the Middle and late Maastrichtian age. The Loftusia minor – Loftuisa morgani Zone, used as indictor for the Middle Maastrichtian age, while Loftusia elongate – Lofusia persica Zone, and mostly point to Late Maastrichtian. The Aqra/ Tanjero interfingering interval represents a ridge about 18 Km, in length and extends mostly NW – SE, forming a lentil body of variable thickness 0 – 225 m, within Kurdistan foreland basin. The variation from the flysch clastics is quite gradational laterally and vertically into Aqra reefal facies and most probably formed due to the presence of submerged highs within the rapidly subsiding trough basin, at the end of the Maastrichtian and termination of the paroxysmal phases of the Laramide orogeny.