Microfacies and sequence stratigraphy of the Late Campanian Bekhme Formation in the Dohuk area, north Iraq

Abstract

ABSTRACT The Bekhme Formation represents the lower part of a regional Upper Cretaceous (Campanian - Maastrichtian) succession that was deposited over most of Iraq and adjacent regions. The formation unconformably overlies the Qamchuqa Limestone Formation (Hauterivian-Albian) and is overlain by the Shiranish Formation (Upper Campanian - Maastrichtian). Northeast of the city of Dohuk, an incomplete, but well-exposed, section of the Bekhme Formation crops out in a 75-m-thick section that formed the basis for our study. Twenty-five samples were collected from the section and used for biostratigraphic and microfacies analysis. The study of planktonic foraminifera resulted in the recognition of two Campanian biozones: the Globotruncanita calcarata Zone and the Globotruncanita stuartiformis–Globotruncanita stuarti Zone, both considered to be of Late Campanian age. Three main microfacies were distinguished throughout the formation, which represent middle-shelf, outer-shelf and upper-bathyal environments. Sequence stratigraphic analysis, as calibrated by microfacies, delineated five depositional sequences of probable fourth-order, thus suggesting the studies section was deposited in about 2.0 million years and represents an overall third-order sequence.