Abstract
A detailed systematic study of calcareous nannofossils was carried out for the Jaddala Formation in (Aj-10) well, Central Iraq. Seventy one species belong to twenty four genera of calcareous nannofossils were identified including sixty two of them were previously named and nine species were identified for the first time and they would not be given names until more information is obtained in the future to support this identification. It is a recorded of five biostratigraphic zone, which suggested the age of the Jaddala Formation to be of early to late Eocene. The recorded biozone includes the following: Reticulofenestra dictyoda (Deflandre in Deflandre & Fert, 1954) Stradner & Edwards, 1968 Partial Range Biozone (CNE 5); Discoaster sublodoensis Bramlette and Sullivan, 1961 Interval biozone (CNE 6-7); Nannotetrina cristata (Martini, 1958) Perch-Nielsen, 1971 Interval biozone (CNE 8); Nannotetrina alata (Martini in Martini & Stradner, 1960) Haq and Lohmann, 1976 Interval biozone (CNE 9); Chiasmolithus gigas Bramlette & Sullivan, 1961Range Biozone (CNE 10-11).
Highlights
The Jaddala Formation was first described by Henson in 1940 near Jaddala village in north Iraq (Bellen et al, 1959)
Correlation and Discussion: This biozone is correlated to the biozone NP13 which was studied by Martini (1971) aged of the Early Eocene (Ypresian) and to biozone CP11which was studied by Okada and Bukry (1981) aged of the Early Eocene (Y prsian)
This biozone corresponds to biozne CNE 5 which was studied by Agnini et al (2014) aged of the Early Eocene (Y prsian); ; Early Eocene was suggested in this study. (Gradstein et al, 2012) (Diags.1-3)
Summary
The Jaddala Formation was first described by Henson in 1940 near Jaddala village in north Iraq (Bellen et al, 1959). The Jaddala Formation outcrops showed up on narrow area of the Foothill Zone of Sinijar Mountain in the Northwestern of Iraq. It was occupied most of sediments in north areas during Eocene period and observed in most of subsurface sections with different thicknesses. The studied section from Ajeel well No (10) is located 34o 50ʹ 14.8ʺ N. and 43o 53ʹ 59.0ʺ E, North East of Tikrit City, Central Iraq (Map.1), within the Low Folded Zone belonging to Unstable Shelf of the Nubio-Arabian platform (Buday and Jassim, 1987). The sampled stratigraphic succession of the Jaddala Formation in this well (15 samples) consists of marly limestone.
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