Lake Gaberoun – is one of the most beautiful lakes of the the great sand sea of the Ubari, with magnificent sand dunes, palm trees and ruins of an old village. Anyone coming across this lake after a long relentless walk in this Saharan desert would pounce to drink this water- but the salinity of this lake is five times saltier than saltwater!
Archaeological research revealed the existence of several fresh-water paleolakes, in ancient Fezzan, Libya. Fezzan is a large closed basin with an area of 450,000 sq km, containing a large palaeolake,termed as Lake Mega-Faezzan.
Both archaeological remains and geomorphological evidence in Fazzan indicate that this currently hyper-arid region experienced wetter phases in the past. Evidence show humans and large humid-climate fauna existed in currently inhospitable areas during the Holocene period (11500 Years ago).
Lake sediments and various geochemical crusts demonstrate the existence of open water bodies and a higher groundwater table during several geological phases.
Dune forms in the Edeyen Ubari Sand Sea are dominated by linear dune ridges plus a few seasonal and perennial lakes -which occupy some interdune corridors, attesting to a high water table in places. But the most signiﬁcant geomorphological features in the Edeyen Ubari are duricrust deposits, composed of varying amounts of calcium carbonate, gypsum and silica.
A sharp boundary between the light areas associated with gypsum and darker regions corresponding to the piedmont sandstone, extends along the base of the escarpment of the large palaeolake. Below this shoreline, a full sequence of palaeolake sediments, interpreted as lacustrine sediments, overlain by grey organic lacustrine silts with numerous mollusc shells is evident in the field.
These deposits are usually capped by duricrusts, predominantly calcretes and cal-silcretes overlain by a thin capping of gypsum crust in places.
Six stratigraphic sections were measured in detail in different parts of the Fezzan basin. These sections are composed of cycles that consist of greenish or reddish sandstone at the base that changes laterally into siltstones that exhibit evidence of soil development and other evidence of sub-aerial exposure including root casts, gypsum pseudomorphs, desiccation cracks now filled by silica and calcite. These sediments are abruptly overlain by laminated limestone with evidence of rootlets and bioturbation. At least five of these depositional cycles were identified in a single section, suggesting at least five humid arid cycles.
The current Ubari Lakes are a group of about 20 lakes, set amidst the landscape of towering dunes and palm fringed oases of the Ubari Sand Sea. Among the most picturesque of the lakes are Gaberoun and Umm al-Maa (the Mother of Water).
Findings from the lakes also suggest that the impressive sand dunes of the Ubari Sand Sea are at least 100,000 years old. Numerous lakes were thought to have covered the eastern and southern regions of the sea, some of which still exist today, as in the case of Gaberoun, Umm al-Maa and Maafu, where the land surface intercepts the water table.
The main river systems that fed the giant lake:-Tasilli N’Ajjer and Hamada Mangueni, situated in the proximity of Lake Umm-al-maa probably went dry. The archaeological finds from the area include dark layers of organic matters, shells, hand axes and other Palaeolithic and Neolithic implements and tools which strongly suggested ancient human activity in Fezzan.
Precise dating of the lakes is yet to be confirmed, but current studies, conducted by the Fezzan Project, suggest Pleistocene and Holocene(11,500-11,700 years) human presence. However, results from Wadi al-Ajal’s playas, indicate these lakes to have disappeared around 3000 years ago.
Refenrence- The Palaeohydrology and Palaeoclimate of Lake Megafezzan: A Giant Palaeolake in the Fezzan Basin, Libyan Sahara- Dr Nick Drake,Department of Geography, Kings College, London; Dr. Simon Armitage, University of Oxford et al; Thiedig et al., (2000), White et al., (2001), Brooks et al., (2003).