Facies analysis of the upper cretaceous-tertiary succession in selected sections from Northern Iraq

Abstract EN

This paper includes petrographic and paleontological observations that are used to interpret the carbonate microfaces of the Aqra-Bekhme and Shiranish formations in terms of depositional environment.

These formations show lateral facies variation in the Bekhme Gorge, Mukaba and Zarda Bee sections.

An understanding of the facies change is presented in this study and used in the interpretation of paleogeographic setting during deposition of the Late Cretaceous formations in northern Iraq.

For this purpose, a petrographic examination of about 300 thin sections allowed the recognition of a wide range of the microfacies, that are grouped into four environmentally indicative facies associations including: 1- Back reef, 2- Reef, 3- Fore reef, and 4- Deep marine.

The back reef facies association of the Aqra-Bekhme Formation in the Bekhme Gorge section is characterized by mudstone-dominated microfacies that are rich in benthonic foraminifera.

The reef facies association of the Formation consists of bioclastic packstone and grainsone.

The fore reef facies association of the Aqra-Bekhme Formation includes bioclastic packstone-grainstone microfacies, rich in benthonic foraminifera.

The mud-dominated deep marine microfacies occur in the middle parts of the The Aqra-Bekhma Formation at the Mukaba and Zarda Bee sections and is comprised of mudstone Similar facies are observed in the Shiranish Formation at the Bekhme Gorge section.