Ostracoda as a paleoecological indicators for the Maastrichtian – Upper Eocene succession in North and Western Iraq

Abstract

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 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.