12 U.S. NATIONAL MUSEUM BULLETIN 275 



of Cussabat near the western edge of the Gulf of Sirte. The southern 

 portions of the gebel grade imperceptibly into the hamadas and 

 transitional desert north of the Hamada el Hamra. A decreasing 

 gradient in elevation runs from north to south, thus the highest 

 portions of the gebel are on its northern margins where it terminates 

 abruptly in the coastal escarpment. 



The average elevation of the Gebel Nefusa exceeds 2,000 feet and 

 in many areas approaches 3,000 feet. The highest point in the gebel 

 (3,176 feet above sea level) is located between Gharian and Bern* Ulid. 



South of the rugged coastal escarpment the interior of the Gebel 

 Nefusa transforms into gently, undulating tablelands with broad 

 valleys and smooth slopes. Several major and numerous lesser wadis 

 have their origins in the interior of the Tripolitanian Gebel. Chief 

 among these are the Wadi Soffegin, which drains eastward into the 

 Gulf of Sirte; the Wadi Tmasia, which has its origin in the gebel 

 north of the Wadi Soffegin; and the Wadi Caam, which arises in the 

 northeastern portions of the gebel and empties into the Mediterranean 

 Sea east of Tripoli. 



Geology 



Tripolitania and Cyrenaica 



This discussion of the major geological features of Libya is based 

 on information given by Raymond Furon in "Geology of Africa" 

 (1960). 



A succession of Mesozoic and Paleozoic sandstones, ranging from 

 the Permian to the Jurassic, outcrops at El Azizia on the Gefara Plain 

 south of Tripoli. These systems are continuous with those of Tunisia. 



The "Continental Intercalaire," of Triassic, Jurassic, and Cretaceous 

 age, outcrops at the base of the coastal escarpment near Horns, 

 Tripolitania, and extends westward nearly to the Tunisian border. 

 This formation is composed of sandstones and clays with numerous 

 plant remains, including silicified wood. The "Continental Intercalaire" 

 extends south to the Tibesti Mountains, but in southern Tripolitania 

 and the northern Fezzan, it is overlain by the Cretaceous marine 

 limestones of the Hamada el Hamra and the Hamada de Tinrhert. 



Marine transgressions invaded Tripolitania and Cyrenaica during 

 the Cretaceous and at successive periods of the Tertiary. The deposits 

 of the Cretaceous form the Hamada el Hamra and the Hamada de 

 Tinrhert in Libya and the Tademait Plateau of the Algerian Sahara. 

 These marine limestones are highly fossilil'erous, containing a variety 

 of marine organisms (corals, nerineas, and radiolarians), and extend 

 south to the cliffs on the northern margin of the Fezzan Cuvette. 

 To the east they are overlain by Tertiary deposits. 



