On some Bivalvia From Fat'ha Formation (M. Miocene) at Sheikhan Anticline, N. Iraq

Abstract

The present study comprises identification and description of some bivalvia from Fat'ha Formation at the northern limb of Sheikhan anticline, north of Iraq. Six species belonging to six genera and four families have been identified. These are: (Mytilus californianus, Nemocardium hantoniense, Paphia (Paphia) undulata, Clementia papyracea, Mactra (Allomactra) sp. and Clausinella sp.).The first three mentioned species were recorded for the first time in Iraq. The identified species are characterized by having small- to medium- sized shells. The shell size variability is most probably reflects different environmental factors, such as salinity fluctuation, insufficient oxygen and food supply, which maybe due to the lack of current action. These condition refer to shallow marine water. Therefore Fat'ha formation is more likely deposited in shallow water semi-closed Lagoonal environment.