Age determinations of Cretaceous sequences based on calcareous nannofossils in Zagros Thrust and Folded Zone in Kurdistan Region-Iraq.

Volume 17 , Issue 3 , September 2015 , Pages 185-196

Authors

¹ Geology Department, School of Science, Faculty of Science and educational Science, University of Sulaimani.

² Ludzislawice, PL 66-431 Santok, Poland

The studied area is located in Northern Iraq in the Kurdistan Region, in the North-

Western part of the Zagros Fold belt. This study concentrates on the biostratigraphic

approach using nannofossil analysis to identify the age of the formations that have

deposited during Cretaceous period in Kurdistan Region-Iraq. The sedimentary

sequences in Kurdistan region exhibit many lateral and vertical environmental and facies

changes. Previously most of the works to recognize the age of the formations were

concentrated on the Foraminifera zonation. In the present study, attempts have been

made to review the age of the formations and the contact between them by using

nannofossil analysis technique. Nannofossils assemblage Chia Gara Formations show

that conformable contact situation between Jurassic-Cretaceous. The contact is between

Late Tithonian Chia Gara and Berriasian- Valanginian Balambo formations. In Kurdistan

during Hauterivian-Barremian the outer shelf sediment of Sarmord Formation deposited

that conformably overlay Balambo Formation. The Qamchuqa Formation is a

heterogeneous group of limestone. The lower part is belongs to the Aptian to Albian

periods, while The upper part of the Qamchuqa limestone is generally dolomitized,

therefore, the existed nannofossils even within the locally thin marl layers are destroyed.

The Dokan Formation, which appears along the Dokan dam, is a Cenomanian age. The

Kometan Formation is represented an Early Turonian age. The top of the Kometan

limestone is characterized by a hard ground most possibly indicating a hiatus. The

sequence of marl-Limestone of Shiranish Formation we dated Early to Late Campanian.

Toward north the Early to Late Campanian part of Shiranish Formation can be locally

replaced by the reefal Bekmeh limestone Formation. Very rare nannofossils were found

in the marly intercalations of the Bekmeh limestone indicating at least a Late Cretaceous

age. The Shiranish/Tanjero formations boundary lies within the Upper Campanian. The

age of Tanjero Formation ranges from Late Campanian to Late Maastrichtian.

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