The Mesopotamian Sedimentology researches..

The studied Cretaceous-Tertiary succession from north Iraq comprising two formations which are composed of carbonate and clastic deposition. These are; Shiranish Formation (Late Campanian-Maastrichtian) and Kolosh Formation (Late Paleocene-Early Eocene). The Shiranish Formation is composed of blue marl in the upper part and thin bedded limestone in the lower and represents deposition in outer shelf basinal setting. The Kolosh Formation comprises dark grey to black shale, green sandstones, marlstones, and rare conglomerates alternating with thin sandy limestone beds and is deposited in marginal marine depositional environment in a narrow rapidly subsiding trough. Clay mineral investigation using X-ray diffraction and scanning electron microscopy proved the presence of smectite, palygorskite, illite, smectite-chlorite mixed layers, chlorite, and kaolinite. Smectite and palygorskite found to be formed authigenically in the marl of the Shiranish Formation, whereas, other minerals are detrital in origin especially in the Kolosh Formation. The mineral variation reflects the environmental changes from Cretaceous to Tertiary times.