Sa’ad S. Al- Sheikhly and Anhar I. Kamil
Department of Geology, College of Science, Baghdad University. Baghdad, Iraq.
Ostracode assemblages have been utilized for the study of the paleoecology of the Maastrichtian – Upper Eocene succession (Hartha, Shiranish, Aaliji, Kolosh, Jaddala and Avanah formations) in North and Iraq, represented by five sections, including four boreholes, Anah well-2, Mityaha well-1, Makhul well-2, Chemchemal well-2 and Jabel Sinjar outcrop section.
According to the different environmental factors affecting on the ostracode ecology, such as the salinity, depth, temperature, oxygenation, substrate and food supply; and depending on the distribution of ostracode assemblages within the studied sections, nine ecofacies have been recognized indicating shallow brackish or brackish- marine water, neritic marine, inner shelf,
inner to middle shelf, inner to outer shelf, middle shelf, middle to outer shelf, outer shelf, and
outer to upper bathyal environments. So, the depositional palaeoenvironment of the formations of the study area are determined.
The presence of the genera Leptocythere and Callistocythere within the Jaddala Formation in Mityaha well- 1 section indicate to the rising of the Khlesia- Mosul uplift during the Late Eocene, which is separating the basin of deposition into two bio-provinces; the Mediterranean Bio-province in the west and the Indo - Pacific Bio-province to the east – southeast