Facies analysis and depositional environment of the upper jurassic naokelekan formation in two selected outcrop sections from Kurdistan Region, ne Iraq

الملخص EN

The Upper Jurassic Naokelekan Formation is mainly composed of organic calcareous shale with some limestone and dolomite.

According to the lithology of the formation in two selected sections, three units can be identified as follow, from bottom to top: a) soft, black, fissile, and highly bituminous, calcareous shale and thin-medium bedded, dark brown, bituminous limestone and dolomitic limestone, b) hard, fine-grained, highly mottled and stylolitic, fossiliferous, dark grey, medium-thick bedded limestone and dolomitic limestone, c) fissile, soft black, calcareous, medium-grained, fetid shale and dark grey, hard, dolomitic and argillaceous medium grained limestone.

The microfacies include Lime-Mudstone, Lime-Wackestone and Lime-Wackestone/ Packstone.

The Benthic (Miliolid) and pelagic (Globigerina) foraminifera, ammonites, ostracods, pelecypods, gastropods and calcispheres of various sizes are the most common skeletal grains, while peloids are the main non-skeletal grains.

Based on lithology and microfacies analysis, the formation was deposited in two different sedimentary environments including lagoon (subtidal) environment for the lower and upper units and shallow marine environment for the middle unit.

The upper contact with the Barsarin Formation and lower contact with the Sargelu Formation are gradational and conformable