Iraqi National Journal of Earth Science

The present study deals with biostratigraphy, depositional environment and sequence stratigraphy of Kolosh Formation in two sections of Bekher anticline, northeastern Iraq by using the planktonic and benthonic foraminifera. Therefore, (48) species of planktonic foraminifera belonging to (14) genera and (34) species of benthonic foraminifera belonging to (19) genera have been recognized. The detailed planktonic foraminiferal investigation permits the recognition of seven well defined biozones and three subzones; they indicate that Kolosh Formation extends from the Early Paleocene (Danian) to Late Paleocene (Thanetian) age. The depositional environment of the formation was studied throughout relying on the variation in the diversity of planktonic forminifera, as well as throughout the ratio of the planktonic foraminifera to the whole mass of foraminifera, and the ratio of planktonic forminifera to the benthonic formiminifera. The lower part of the formation represents the upper bathyal environment, while the middle part deposited within the outer shelf environment, then deposition basin became within the middle shelf area in the upper parts of the formation.
Sequence stratigraphic analysis for the studied sections of Kolosh Formation  delineated three sequences which is interpreted as 3^rd order sequences, and it is found that the deposition of Kolosh Formation in the Badi section had been occurred in shallower level for most sedimentation intervals compared to the Linwa section which represents a somewhat deeper marine environment.

Thirteen samples of Aaliji Formation from the well (K-116), Kirkuk area, Northern Iraq, are studied on the basis of the stratigraphic ranges of the recorded calcareous nannofossils for sixty species, the studied section reveals five biozones arranged from oldest to youngest as follows:

Fasciculithus tympaniformis Interval Biozone (CP4)
Heliolithus kleinpellii Interval Biozone (CP5)
Discoaster mohleri Interval Biozone (CP6)
Discoaster nobilis Interval Biozone (CP7)

5. Discoaster multiraditus Interval Biozone (CP8)
These biozones are correlated with other calcareous nannofossils biozones from both local and regional sections leading to conclude the age of Middle Paleocene to Early Eocene.

Rock magnetic properties have been investigated across the Paleocene/Eocene boundary in two distally separate sections of Paleogene marine sedimentary rocks from Iraq, namely the Sinjar and the Shaqlawa sections. The sediments at the studied sections belong to the Aaliji and the Kolosh formations respectively, which were previously examined for their biostratigraphy by the authors using planktonic and benthonic foraminifera to delineate the Paleocene/Eocene (P/E) transition. Measured magnetic properties include; bulk magnetic susceptibility, hysteresis cycles, isothermal remnant magnetization (IRM) acquisition, and thermomagnetic curves analysis. Rock-magnetic results (i.e. low magnetic coercivity component) indicate greigite as the main magnetic phase at Aaliji rocks, while a mixture of magnetite and greigite with high magnetic coercivity has been observed at Kolosh clastics. Magnetic susceptibility is induced by related to both biogenic minerals (mainly at Aaliji Formation) and transported terrigenous material sources. Multi varied magnitude phases of high bulk rock magnetic susceptibility observed in both formations along PETM lithosomes are attributed to two sources: greigite or biogenic iron oxides source and increase in terrigenous discharge source as inferred by anoxic to suboxic iron - sulfate-reducing conditions and lithological change respectively. Both sources referred to some of environmental conditions associated with Paleocene - Eocene thermal maximum events such as methane dissociation, water stratification, enhanced hydrological and weathering cycles..

Twenty two ostracoda species belonging to eight genera were described
from Avanah ,Sinjar, Khurmala, Aaliji, Akashat and Jaddala Formations, (Paleocene-Eocene) of North, West and Central Iraq of which four species are new, Abyssocypris zumarensis, sp.inov., Argilloecia heijranensis sp. nov., Argilloecia baajensis sp. nov., Schizocylhere anbarensis sp. nov. The identified species
shows strong affinities to those in India, North Africa and the Middle East (Southern New Tethys).