Evidence of a Quaternary dammed Lake in the Mawat–Chwarta area, Western Zagros, Kurdistan Region, NE-Iraq

The Mawat–Chwarta valley is located north of the Sulaimania City at Northern Iraq and is surrounded by high mountains on all sides. White laminated sediments with annual varves on a millimetre scale have been recorded at eight localities on the valley gentle slopes. Sedimentological, palaeontological and geomorphological data of these sediments suggest that a lake occupied the valley during the Quaternary. The sediments are of two types, purely fine-grained and fine-grained with coarse interbeds, the two types occur at an elevation difference of about 62 m. The two types are interpreted as representing deep (abyssal) and shoreline deposits, respectively, and indicate the approximate depth of the lake. The sediments contain the fresh water green algae of the genus Botryococcus in addition to a few leaves, scattered plant debris and some pollen grains mainly of herbaceous plants. Contrary to the general south-western drainage pattern in Northern Iraq the Mawat–Chwarta valley is drained to the north, where the Mawat River passes now through deep and narrow gorges along which rock slides and debris plugs are known to have occurred in the past. These mass wasting events are considered here to have blogged the runoff of the valley in the past and eventually led to the formation of a large dammed lake. Numerical chronology work failed, which requires further investigation in the future.