Chaîne du Thaljah

The line of mountains runs in a roughly east–west direction from Gafsa in Tunisia to Negrine in Algeria, crossing the border not far from the small oasis of Tamerza. The highest point is the Jebel-Bliji. On the north side, at a place called Es Safia 5.5 kilometres (3.4 mi) south-southeast of Tamerza, a rock painting was found on an overhanging rock wall at the entrance of a deep ravine.[2] It depicts animals and men in silhouette, in blood on a yellow-ochre background, all slightly glazed. It was probably made by Berbers between the Stone and Bronze Ages.[3]

In 1885–86 the geologist Philippe Thomas explored the southern area of Tunisia between the meridian of Kairouan and the Saharan chotts, covering a vast area. He also explored the western area, which his colleagues had neglected, particularly the Chaîne du Thaljah or Chaîne du Tseldja mountains that stretch westward from Gafsa into Algeria.[4] He identified the geology of the Gafsa chain with that of the M'fatah massif in Algeria and on 18 April 1885 found phosphates at Jebel Tselja.[5] Thomas observed that at the junction of the Cretaceous limestone axis of the chain with its Eocene foundations there was a dark marl and a brown or greenish-gray limestone with a tricalcium phosphate content that averaged 60%. This was found where the Jebel Tseldja opens into the plain at Fous-Tseldja, near Métlaoui.[4]