614 PROF. J. W. GREGORY ON [Nov. I 911, 



VIII. Summary of Conclusions. 



Cyrenaica is a plateau of Eocene limestones ranging from the 

 Lower to the Upper Eocene, and capped by limestones referred to 

 the Aquitanian and the Miocene. The predominant dip is to the 

 east, so that the Miocene limestones found on the plateau in 

 Eastern Cyrenaica occur close to sea-level on the western coasts 

 of Egypt. The Cyrenaican plateau may, therefore, be regarded as 

 part of the western limb of the great syncline of Western Egypt. 



The plateau has been isolated and fractured by a series of faults 

 of late Kainozoic date. The position of the northern coast of Cyre- 

 naica is determined by these faults, and the Tokra scarp separates 

 the main plateau from the coastal plain east of Benghazi. The 

 Tokra Eault is on the same line as an apparent fault in Western 

 Crete. 



The faults may be divided into three groups : — (1) those ranging 

 east and west along the northern coast ; (2) those trending from 

 south-west to north-east, including the Tokra scarp and the 

 parallel scarp which bounds the plain of Merj ; and (3) the north- 

 and-south faults which have determined some of the chief bends in 

 the northern coast of Cyrenaica and Western Egypt. The three 

 series are connected with the faults which have broken up the land 

 of iEgea and formed the rift-valleys that have separated Eubcea 

 from the mainland of Greece. 



The rocks of Cyrenaica are limestones composed almost entirely 

 of organic material. They contain occasional quartz-grains and 

 some very fine clay. The limestones have been deposited in a clear 

 sea, and usually in moderately deep water, though at the top of the 

 Slonta Limestones there is a bank of coral-reef limestone. The 

 limestones range from shallow-water deposits, down to those formed 

 at a depth approaching 1000 fathoms. 



The rocks may be classified as follows : — 



Pleistocene Alluvial deposits, etc. 



Miocene Grubah Limestones. 



Oligocene Cyrene Limestones. 



(Slonta Limestones. 

 Perna Limestones. 

 L Apollonia Limestones. 



The geological history of the country begins with the deposition 

 of the chert-bearing Apollonia Limestones, which may be cor- 

 related with the Libyan or Lower Eocene Series of Egypt. The 

 sea probably deepened to nearly 1000 fathoms, at which depth 

 were deposited some chalky limestones with Globigerina. A re- 

 elevation of the sea-bed led to the formation of limestone-breccias 

 and conglomerates. Then followed another subsidence, during 

 which were formed the cream-coloured limestones of Derna. This 

 horizon is characterized by the typical form of Nummulites gizehensis. 



