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Basim Rushdi Hijab, College of Science, Baghdad University (Iraq)
Ezaddin Baban, Suliamaniya University (Iraq)
Emad Al Kharssan, Basraha University (Iraq)
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Limestones rocks of Paleocene-Lower Eocene, Maastrichtian, and Valanginian-Tournian ages at the NE Iraq were all sampled for paleomagnetic investigations with some igneous gabbros intrusions too. Twelve hand samples and 200 oriented drilled cores were collected from these rocks. The NRMs were measured using spinner magnetometer (Baghdad University) and the cryogenic magnetometer (Oklahoma University (USA)). The remnant magnetization in the Aqra limestone formation (Maastrichhtian age) is of a depositional origin and carried by a detrital magnetite grains. It corresponds to the genuine paleomagnetic directions. The samples were taken from two localities (Maukaba and Zardabe) along Azmer fold. Both of these rocks show reverse paleomagnetic directions (Dec=140.7°, Inc=-26.5°, K=31.9, N=20, α95=4.5° and Dec=169.3°, Inc=-26.3°, K=28.5, N=25, α95=6.4°). The overall mean VGPs position of the Maukaba locality is Plat=44.4° S , Plong=279°, and for Zardabe locality Plat=57.1°, Plong=235° with co-latitude (-14°) and (-13.9°) respectively. Accordingly, the paleo-positions of Aqra Limestones basin on Maastrichtian times were 14° Nlat and 13.9° Nlat. This suggests that the Neotethys Ocean was still there to the north and northeast of Iraq during Maastrichtian time. The closure of this ocean occurred between the Maastrichtian and Lower Tertiary. The paleo-position of the Aqra Limestone basin clearly suggests that the north part of Iraq was still in the warm environmental conditions during Maastrichtian times. This means that the oil accumulation can be found in rocks of ages for Maastrichtian and older than Maastrichtian. The paleo-pole positions of Maukaba and Zardabe localities showed clear difference in their longitude values, which reflect the difference in the declinations of the recorded magnetic directions of these rocks. This is probably due to the tectonic movements along transversal faults. These movements are indicated by the divergence (change in the direction) of fold axes. Such case is clear for Azmar fold axis. A reconstruction of this fold axis to its previous lineation resulted in a coincidence of the Maukaba and Zardabe magnetic declinations, which means that the folding and the divergence in the fold axis happened after Aqra Limestones rocks acquired their magnetic directions.
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