Late Holocene palaeoenvironmental history of Khawr Rawri and Khawr Al Balid (Dhofar, Sultanate of Oman)

The coastal wetlands in Dhofar (Sultanate of Oman) provide a record of Late Holocene palaeoenvironmental history. The age of the surface sediments at some selected sites in the estuaries, locally known as khawrs and qurms, ranges from 750 to 390 calendar years (cal y) BC to Present. Geomorphological data suggest that prior to 270–420 cal y AD these estuaries were open to the sea and received a high input of fresh water from the mountains. At least from 270-420 cal y AD onwards, the physiography of the estuaries changed as a consequence of dwindling fresh water input from the mountains. As a result, the open estuaries changed into barrier dominated estuaries with periodical input of saline and fresh water. Palynological data indicate that the estuaries are mainly filled with (i) pollen and spores from the surrounding vegetation; (ii) a regional input of pollen and spores through surface and subsurface runoff from mountains, coastal plain and, wadis; (iii) pollen and spores from East Africa and the Indian subcontinent brought in by the monsoon. Between 750–390 cal y AD and 270–420 cal y AD the local input of khawr taxa prevailed whereas from 270–420 cal y AD to Present coastal plain and wadi taxa prevail. Both geomorphological and palynological data suggest the ancient centers of trade such as Samhuram at Khawr Rawri (ca. 100 BC–100 AD) and Zafar at Khawr Al Balid (12th–15th centuries AD) were affected by important hydrological changes related to desertification of the region as a consequence of a weakening SW (summer) monsoon.