The Late Campanian and Maastrichtian attend closure of the Southern Neo-Tethys and formations intraplate extensional and transextensional basin, in addition to deposition of the Shiranish Formation in the foreland basin (Jassim and Buday 2006). The Shiranish Formation (228 m thick) is exposed on the southwestern limb of the Sarah anticline in the Dokan area. Its consists of dark gray marly limestone, soft bluish gray marl rich in planktonic foraminifera, shales, and thin pelecypodal limestone bed on the top of the formation. The lower contact is unconformable with the underlying Turonian Kometan Formation, while the upper contact is conformable with the overlain Tanjero Formation. Six main facies were distinguishable throughout the formation reflecting the middle shelf to middle bathyal depositional environments of the formation. The alternation of these depositional environments used to interpret three depositional sequences containing three maximum flooding surfaces (MFS 165, MFS 170, and MFS 175 of Sharland et al. 2001 andAqrawi et al. 2010) show good correlation with those in Iraq and other part of Arabian plate.
The Kometan Formation is widely distributed in the northern (Kurdistan region) and central Iraq. The studied area is located near the Dokan Dam, about 58 km., to the Northwest of the Sulaymaniyah city, Northeastern Iraq. The Kometan Formation is exposed on the southwest flank of the Sarah anticline. The formation consists of limestone and dolomitic limestone, which have cherts nodules throughout the formation. The Gulneri Formation is recorded below the Kometan Formation with unconformable contact, while at the top is bounded by the Shiranish Formation unconformably too. Three microfacies are identified, these are lime mudstone, planktic foraminiferal lime wackestone-packstone, keeld planktonic foraminiferal lime wackestone-packstone microfacies. All the sedimentary and fossil evidence refer that the sedimentary environment of the formation is the outer shelf to upper bathyal at the lower and upper parts of formation and its extension to the middle bathyal in the middle part of the formation. Based on the stratigraphic ranges of the recorded Calcareous nannofossils biozones, the age of the Kometan Formation at Dokan area is Late Turonian-Early Campanian.
A mineralogical study using X-ray diffraction supported by scanning electron microscopic examination on the Paleocene- Eocene Kolosh and Gercus formations from northern Iraq is conducted to show the distribution of clay minerals and their paleoenvironmental implications. Smectite palygorskite, kaolinite, illite, and chlorite are commonly present in varying proportions within the Kolosh and Gercus formations. Association of smectite and chlorite in the claystone of the Paleocene Kolosh Formation refers to marine environment of this formation, whereas development of palygorskite fibers from smectite precursor may relate to post-depositional diagenesis. In addition, the abundance of illite and kaolinite in the Eocene Gercus Formation suggests a greater influence of terrigenous input in humid conditions, affecting the distribution of these clay minerals. The study shows vertical change in clay minerals distribution when illite and kaolinite dominate in the Eocene Gercus Formation, in comparison to chlorite and smectite abundance in the Paleocene Kolosh Formation which may relate to global warming in the Eocene.
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