NEW SEDIMENTOLOGIC AND STRATIGRAPHIC CHARACTERISTICS OF THE UPPER BOUNDARY OF  QAMCHUQA FORMATION (EARLY CRETACEOUS)  IN NE ERBIL, KURDISTAN REGION, NE IRAQ

M.  Ameen, Bakhtiar; H.  Karim, Kamal

	NEW SEDIMENTOLOGIC AND STRATIGRAPHIC CHARACTERISTICS OF THE UPPER BOUNDARY OF QAMCHUQA FORMATION (EARLY CRETACEOUS) IN NE ERBIL, KURDISTAN REGION, NE IRAQ
Iraqi Bulletin of Geology and Mining
Article 1, Volume 4, Issue 2, 2008, Pages 1-13
Authors
Bakhtiar M. Ameen; Kamal H. Karim
Abstract
The contact between Qamchuqa (Early Cretaceous) and Bekhme (Late Cretaceous) formations is studied in the field and laboratory. On lithological basis, the contact is described and analyzed in four different sections. In all four sections, the result of the study showed that the boundary seems to be gradational; two of four sections (Zante gorge and Perse Mountain) are barren of conglomerate, breccias or erosional surfaces, so the contact seems to be conformable in the field. The other two sections (outlet and inlet of Bekhme gorge) contain beds of apparent conglomerate (or conglomerate-like masses), which in the present study are inferred to be not depositional, but diagenetic in origin. They are secondary ball and pillow structures, which formed during burial by lithostatic stress. In the inlet of Bekhme gorge section, there is a mass of breccia (about 1.5 m thick), which is located 10 m above the beds, which include ball and pillow structures. This breccia is not depositional as it consists of extremely angular clasts of limestone. These clasts are believed to be tectonic in origin and derived from younger beds, above the contact, which are not more than 20 m higher from their location. The clasts are transferred to this location, possibly by a reverse fault across Greatyer Zab river. In contrast to previous studies, the contact suffered from deepening relative to the overlying and underlying Bekhme and Qamchuqa formations, respectively. This is manifested by green marl, marly limestone, limestone bearing planktonic forams and breccias. The soft succession at the boundary (about 30 m thick) is most possibly deposited during the previously suggested gap or unconformity.

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