MAPPING OF THE MIGHTY KUFRAH PALEORIVER SYSTEM IN THE EASTERN SAHARA

In this study, optical and radar remotely sensed data have been integrated with GIS hydrologic routine to delineate the complete drainage network of the Kufrah Paleoriver and its associated watershed. The study hypothesizes that the Kufrah River is the successor of the master Sahabi River system that was dominating central Libya during the late Tertiary. Detailed geomorphologic investigations, based on satellite data, provide evidences of possible drainage rearrangement in the region, which manifests itself in a barbed-like drainage configuration, the missing of major drainage headwaters, and the presence of deep vertical incisions along the main course of the Kufrah River. These might all testify for the occurrence of a major river rejuvenation in the region. The considerable height difference between the two basins of Sahabi and Kufrah, caused by the continuous subsidence of the latter, had triggered the headwater erosion and stream piracy to the favor of the Kufrah system. This is believed to give rise to the creation of the Kufrah super watershed (~236,000 km²), and to the rerouting of a significant sediment supply from the Sahabi to the Kufrah basin that led to the formation of the vast Kufrah’s fan delta. The N and NW trends of the delta distributary channels indicate that the Kufrah River was draining occasionally to a topographic depression that was periodically occupied by lakes which, when dried-up, were the immediate source of the sands of the Great Sand Sea. The obvious lining-up of the delta channels with the Sahabi Paleochannel of the Sirt Basin, suggests that the Kufrah River was an external drainage that once flowed directly to the Mediterranean Sea. Moreover, the alignment of the southern reach of the Kufrah River with the Al-Kebir elongated trough, suggests that, the Kufrah River was extending further south beyond its present location, where Megalake Chad had sourced it through north-flowing channel systems. If this hypothesis is valid, then the Kufrah River would have been, for some time, the conduit of the Megalake Chad to the Mediterranean Sea. Such a lake-sea linkage is of a prime groundwater significance and will have important implications on our understanding of the paleo-environments of the Eastern Sahara. The Kufrah River Delta and its vicinity could potentially hold vast reservoirs of oil and gas at depth.