The Azawagh refers to the dry
structural basin, which once carried a northern tributary of the
Niger River, the Azawagh river, known as
Dallol Bosso further south. The river, which ran some in prehistoric times, dried up after the
Neolithic Subpluvial and created a basin of some . Its valley, which geologists call the
Iullemmeden Basin, is bordered by the
Hoggar Mountains and their foothills in the north, the
Aïr Mountains in the east, and the
Adrar des Ifoghas in the west. The
bedrock of the region is
Cretaceous/
Paleocene limestone and
clay, which was cut by erosion and covered by
aeolian sand in the
Upper Pleistocene. In ecological terms, the Azawagh basin is divided into, from north to south, a Saharian, a Sahelian and a northern
Sudanese (referring to the geographic region) zone. In Niger, Azawagh generally includes the towns of
Abalagh (Abalak), In Tibaraden (
Tchin-Tabaraden), Tiliya,
In Gal and
Tabalaq, a village where the sole lake of the region is located. ==History==