NEW IDEAS ABOUT GULNERI FORMATION (EARLY TURONIAN) IN DOKAN AREA, KURDISTAN REGION, NE IRAQ

H. Karim, Kamal; A. Taha, Zardasht

	NEW IDEAS ABOUT GULNERI FORMATION (EARLY TURONIAN) IN DOKAN AREA, KURDISTAN REGION, NE IRAQ
Iraqi Bulletin of Geology and Mining
Article 1, Volume 5, Issue 2, 2009, Pages 29-39
Authors
Kamal H. Karim; Zardasht A. Taha
Abstract
Gulneri Formation (Early Turonian) consists, mainly as previously described, of shale deposited in euxinic and small relic basin. In the present study, it was found that it consists mainly of marl and marly limestone with no more than 20% of laminated shale. Thin section study showed that the shale is highly deformed, with foliation-like texture. Therefore, most probably the previously described shale is originally marl, which is changed to laminated shale-like rock, by pressure that released insoluble residue and bitumen materials from surrounding rocks. By filtering of these materials, the marl was changed to black shale-like rock. The effect of the pressure is observed by bending of the shale laminae around the spherical limestone bodies and the flattening of planktonic foraminifera to elongated shape. The upper and lower contacts of the Gulneri Formation seem to be conformable; as conglomerates, erosional surfaces and paleosols were not found. But, short duration of possible submarine erosion or slow rate of deposition is not excluded. There are spherical limestone bodies in the formation and near the contacts, but they are not conglomerate; as assumed previously. Field and thin section studies reveled that the bodies are ball and pillow-like structures, which are formed by pressure; this is evidenced by the absence of silt and sand size grains in the ball and pillow-like structures. This formation occurs only in Dokan dam site (Northwest of Sulaimaniyah) and it does not exist in near by surrounding areas, therefore, we suggest its combination with Kometan Formation.

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