Combined Ostracoda and Foraminiferal Biozonation with Environment of Fatha Formation (Middle Miocene) In Different Oilfields, Southern Iraq

Abstract

The Fatha Formation is a significant stratigraphic unit that was deposited during the Miocene; its sediments covered the basin from the north to the south of Iraq. Six oil wells within four oilfields were chosen for the current study. Both types of samples (core and cutting) were prepared to extract the existing fossils. Forty-two foraminifera species belonging to twenty-one genera and forty ostracods species belonging to thirty genera were identified. On the basis of the biostratigraphic distribution of the foraminifera and ostracoda species, one biozone for foraminifera was plotted which is Elphidium craticulatum taxon range zone, also one biozone of ostracoda was determined which is Schneiderella unispinata Assemblage zone. The age of Fatha Formation is Middle Miocene depending on the index fossils of the ostracods. All genera recorded in the study area belong to benthic foraminifera except one genus (Globigerina quinquelob) belongs to the planktonic foraminifera. The environment of the Fatha Formation in the southern basin is slightly different from the northern basin, but the main environment is still a lagoon but it is accompanied by several other environments such as shallow water, tidal and subtidal. The lagoon was partially closed, and it was affected by marine water, especially in the lower part of the studied formation.