RODENTS OF LIBYA 13 



The Eocene transgression outcrops widely north and east of the 

 Gebel es Soda and also appears near the coast on the Gebel el Akhad 

 east of Benghazi. At El Fogaha, south of the Gebel es Soda, and on 

 the Gebel el Achdar near Derna, the succession is complete, ranging 

 from sediments of lower Eocene to upper Eocene. 



Another transgression advanced to the Tibesti Mountains during 

 the middle Eocene. These sediments, comprising 200 meters of lime- 

 stone overlying the Paleozoic sandstones or resting directly upon 

 the Pre-Cambrian, represent the Sirtica Trough, whose shorelines are 

 found today at a height of 600 meters above sea level on the northern 

 outliers of the Tibesti mountains. 



Oligocene sediments indicate a deep gulf south of the Gulf of Sirte, 

 which did not reach as far south as that of the Eocene. 



The Miocene Sea included parts of Cyrenaica, and some lower 

 Pliocene beds are found at Agedabia near the southeastern margins 

 of the Gulf of Sirte. 



Fezzan 



The geological structure of the Fezzan is relatively simple, being 

 primarily a large cuvette (basin) of Nubian Sandstone (Cretaceous) 

 overlying the Paleozoic. The Fezzanese cuvette is divisible into two 

 large structural components: a southern synclinal zone which is an 

 extension of the covering of the Ahaggar Mountains of southeastern 

 Algeria and the Tibesti Mountains of the northern Chad, and a 

 northern zone consisting of the Cretaceous Hamada de Tinrhert in 

 the west and Eocene sediments in the east. Extensive volcanic ex- 

 trusions rest upon portions of the northern zone. 



The morphology of the western Fezzan is determined by a large 

 east-northeast west-southwest anticline, which is connected in the 

 southwest to another anticlinal zone near Ghat. This anticline extends 

 from north of Serdeles to north of Edri. Farther west, it grades into 

 the Fezzan synclinal cuvette and forms an artesian basin. The northern 

 and southern limits of the anticline outcrop, respectively, as south- 

 facing escarpments near El Hasi north of Edri, and as north-facing 

 escarpments in the southern parts of the Wadi es Sciati. 



In the western Fezzan, geological succession generally runs from 

 Devonian to Lower Cretaceous and includes fossiliferous limestone, 

 sandstones, and marls containing brachiopods, crinoids, and silicified 

 wood. 



The northeastern Fezzan is composed of Cretaceous rocks which 

 disappear beneath Tertiary deposits farther east. Farther south, strata 

 range from Pre-Cambrian to Cretaceous, but Paleozoic sediments 

 are dominant. 



