Biostratigraphy by Calcareous Nannofossils and Paleoecology by Ostracoda of Tanuma Formation, Central Iraq

Abstract

Forty three samples of limestone and shales from Tanuma Formation obtained from East Baghdad well (No. 11) at depths (2067 - 2177 m.) about 110 m. in thickness. Details investigated carried out identify twenty species of calcareous nannofossils, sixteen described from other region and four left open name because of rare and not clear samples. Furthermore, twenty four species of ostracodes belonging to fourteen genera were recorded, these are: Bairdia, Brachycythere, Curfsina, Cythereis, Cytherella, Cytherelloidea, Dolocytheridea, Ovocytheridea, Paracypris, Protocythere, Pterygocythere, Schuleridea, Spinoleberis, Veenia. The recorded calcareous nannofossils assemblages permits to recognized two biozones these are: 2- Micula cf. decussata Interval Biozone (CC14). 1- Marthasterites furcatus Interval Biozone (CC13). On the basis of biocorrelation with previous works Coniacian age confirmed for the Tanuma Formation at the studied section. The analysis of the ostracode fauna led to conclude that the palaeoecology of the Tanuma Formation in this section is shallow marine environment at depth about 200m in the neritic zone with warm water, under normal marine water salinity.