Abstract
The present study is concerned with lateral and vertical facies changes between Kolosh (Paleocene) and Sinjar (or Khurmala) (Paleocene-Early Eocene) Formations in Sulaimani and Duhok area, Kurdistan Region, NE-Iraq. The latter and former formations are belonging to basinal clastic (turbidite) and reefal carbonate facies respectively. The facies changes are documented in six sections by field studies and evaluation of previous ideas and data which are critically discussed and compared to the result of the present study. The special attention is directed towards the contact between the two Formations in relation to conformity. All the studies achieved before 2002 showed conformable contact between the two formations while the most recent study found large a gap (erosional unconformity) between the two formations which persisted for 5million years. According to latter study, the sea level fall associated with this unconformity assigned to be type one and type two sequence boundaries in the east of Darbandikhan, north of Koya towns and the Bekhme gorge.Conversely, the present study has not recorded gaps in the sedimentation in the studied sections either in Sulaimani or Dohuk area. The contact can be regarded as transgressive system tract which represented by green marl or sandstone, which changes to limestone of Sinjar or Khurmala Formation (HST).The conglomerate beds that are recorded in the previous studies at the contact of the two formations are not proved in the present study. The previously recorded conglomerate is located inside the upper part of the Kolosh Formation not in the contact and it represents submarine fan feeder channel. In contrast to previous studies, neither incised valleys nor erosional unconformity are found at the contact between the two formations in the studied area. The one meter intraformational conglomerate that are found (in some previous studies) in the Bekhme gore is not found in the present study. It is observed that the Kolosh Formation, at Bekhme Gore consists of green marl and sandstone with one bed of Khurmala Formation. The green marl is changes totally to dolomitic limestone of the latter Formation toward northwest at the north of Saru Kani village near Bujeel town. This proves that both formations are deposited in one basin and Khurmala formation has the age of Lower Paleocene to Lower Eocene.
Highlights
The Kolosh Formation was firstly described by Dunnington (1952; in Bellen et al, 1959) in Kalozh area north of Koya town, northern Iraq (Fig.1)
It consists of alternation of medium to thin beds of calcareous shale and sandstone which contain fragments of various grain sizes of igneous, chert and radiolarite. They added that its age extended from Paleocene to lower Eocene, while Al-Omari et al (1993) and Al-Mutwali (2001) reported early Paleocene–Early Eocene age to Kolosh Formation near Shaqlawa town, north Iraq
Lawa (2004) in the page 183 has drawn the stratigraphic column of both Zhalla and Bamo sections and in these sections; he indicated the contact between Kolosh and Sinjar Formations 13 meters below the contact that concluded in the present study (Fig.9 see red arrow)
Summary
The Kolosh Formation was firstly described by Dunnington (1952; in Bellen et al, 1959) in Kalozh area north of Koya town, northern Iraq (Fig.). It consists of alternation of medium to thin beds of calcareous shale and sandstone which contain fragments of various grain sizes of igneous, chert and radiolarite They added that its age extended from Paleocene to lower Eocene, while Al-Omari et al (1993) and Al-Mutwali (2001) reported early Paleocene–Early Eocene age to Kolosh Formation near Shaqlawa town, north Iraq. According to Bellen et al, (1959) and Jassim and Goff, (2006), the Paleocene Kolosh Formation is deposited as flysch facies of sandstones, marls, shales, intraformational conglomerates and thin beds of arenaceous limestone They added that it is deposited in subduction trench, parallel to the suture zone that is formed by closing of the southern Neotethys Ocean and final collision between the Arabian, and Iranian plates. In north Iraq, it is passing to or inter-tongue with www.ccsenet.org/jgg
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