Iraqi National Journal of Earth Science

Ostracode biostratigaphy were investigated in detail from three formations (Shiranish, Hartha and Mushorah ) in subsurface sections of four boreholes Northwest and centre of Iraq.
On the basis of the ostracode species distribution, the studied formations were divided into four ostracode biozones as follows:

Biozone 1: Cytherella IRC 22 Interval zone. (Early Campanian).
Biozone 2: Occultocythereis elongata Interval zone. (Late Campanian).
Biozone 3: Krithe sp. M 1113 Interval zone. (Early Maastrichtian).
Biozone 4: Holcopocythere bassiporosa Interval zone. (Late Maastrichtian).

Depending on the above biozones correlated with other previous works from Iraq and the Middle East regions the following ages were proposed for the studied formations:

Shiranish Formation: Late Campanian - Maastrichtian.
Hartha Formation: Late Campanian - Early Maastrichtian.
Mushorah Formation: Early Campanian.

A surface section of Jaddala Formation was studied near Bara Village in the western plunge area of Sinjar anticline northwestern Iraq . The sequences under study consist of marl, marly limestone and limestone beds. Detailed study of planktonic foraminifera revealed (38) species belonging to (14) genera, the stratigraphic distribution of these species permits the regognition of five zones, these are: Morozovella aragonensis Zone, Acarinina pentacamerata Zone, Acarinina bullbrooki Zone, Globigerinatheka subconglobata Zone and Acarinina collactea Zone. These zones indicate that Jaddala Formation is of Early - Middle Eocene age.

Planktonic foraminifera are studied from Shiranish Formation in Kirkuk well No.(306) , north of Iraq between depth interval( 1540-1660 m). Detailed study of the planktonic foraminifera revealed (25) species. The stratigraphic distribution of the Planktonic foraminifera recorded in the section permits the recognition of four zones these are from olderat the:

4- Gansserina gansseri Interval Zone ( Part).
3- Globotruncana aegyptiaca Interval Zone .
2- Globotruncanella havanensis Partial Range Zone.
1- Globotruncanita calcarata Total Range Zone ( Part) .

The zones are correlated with other studies inside and outside Iraq .The present work indicats that Shiranish Formation is of Late Campanian to Early Maastrichtion age.

The litho-and biostratigraphy of Shiranish Formation have been investigated within a well-exposed section at the southern limb of Bekhair anticline, Dohuk area, Northern Iraq. The studied section consists mainly of marl, marly limestone, and limestone. The Formation unconformably overlies Bekhme Formation and it is overlain unconformably by the Kolosh Formation. The samples of the section under investigation yielded rich and well diversified planktonic foraminiferal taxa, where 55 planktonic species belonging to 16 genera have been recognized, the detailed foraminiferal investigation permits the recognition of 8 well defined zones. These are from older at the base:

8. Plummerita hantkeninoides Total range Zone (Part).
7. Pseudoguembelina palpebra Partial range Zone.
6. Pseudoguembelina hariaensis Interval Zone.
5.Racemiguembelina fructicosa Interval Zone.
4. Planoglobulina acervulinoides Partial range Zone.
3. Contusotruncana contusa Interval Zone.
2. Gansserina gansseri Interval Zone.
1. Globotruncana aegyptiaca Interval Zone (Part).

The Planktonic zones were correlated with other zonal schems in and outside Iraq. They are considered to be extending from middle Late Campanian to latest Maastrichtian.

The Balambo Formation (Lower Cretaceous), exposed on Jebel Azmer in Sulaimaniya area northeastern Iraq, consists mainly of well bedded hard limestone. Outcrop of 224 m of the upper part of the Balambo Formation are well exposed on the surface with a steeply dipping angle. Planktonic foraminifera represent the major microfossil assemblage of the Balambo Formation. Nineteen cosmopolitan planktonic foraminiferal species were recorded from 92 samples. The identified planktonic foraminifera are of typical Tethyan character. Biostratigraphically the exposed part of the Balambo Formation is defined by four zones and two subzones, these are in ascending chronological order: Ticinella primula Zone, Biticinella breggiensis Zone which is divided into two subzones (Ticinella praeticinensis and Rotalipora subticinensis Subzones), Rotalipora ticinensis Zone and Rotalipora appenninica Zone. Accordingly the age of the Balambo Formation in Jebel Azmer is Middle–Late Albian. The presence of a major hiatus at the end of the Rotalipora appenninica Zone delineates the upper boundary of the formation in the studied section.

Eighteen plankonic foraminiferal species belonging to five genera have been identified within the studied section of Shiranish Formation in Butmah well no.15; which is divided into four biozones. The first zone represents the Late Campanian age while the other three zones extend within the Early and Middle Maastrichtian age These zones are:
-Gansserina gansseri Zone
-Globotruncana aegyptiaca Zone
- Globotruncanella havanensis Zone
-Globotruncanita calcarata Zone
The age of the studied section in Butmah well no.15 has been fixed as Late Campanian to Middle Maastrichtian while the upper part of the Middle Maastrichtian and the whole Upper Maastrichtian are missing. According to this fact the contact surface between Shiranish and Aaliji Formations is an unconformity surface.

Thirty eight planktonic foraminiferal species were recorded from the Kometan and Gulneri Formations in the subsurface section of Jambur well No. 46, northern Iraq. On the basis of stratigraphic ranges of the recorded foraminifera the studied sequences are attributed to Helvetoglobotruncana helvetica, Marginotruncana sigali, Dicarinella primitiva, D. concavata, Rosita fornicata and Globotruncanita elevata Zones. The Gulneri Formation is Middle to Late Turonian in age, whereas the Kometan Formation ranges from Late Turonian to Early Campanian.
ــــــــــــــــــــــــــــــــــــــــــــــــــــــ

Planktonic foraminifera are studied from Aaliji and Jaddala Formations in East Baghdad Well No.2 between the depth interval 1770-1900 m. Four biostratigraphic zones are recognized in these formations:
Globorotalia (A.) bullbrooki Zone (P.10).
Globorotalia (Morozovella) subbotinae subbotinae Zone (P.7).
Globorotalia (Morozovella) velascoensis Zone (P.5and6).
Globorotalia(Globorotalia)pseudomenardii Zone (P.4).
The results of this study are compared with the work of others inside and outside Iraq. The age of Aaliji in the said well is Late Paleocene - Early Eocene and that of Jaddala is Early – Middle Eocene.