

Vol. 67. j THE GEOLOGY OF CYRENAICA. 615 



The Derna Limestone was succeeded by a marly limestone containing 

 Fibularia luciani, followed by the deposition of a rough-weathering 

 massive limestone containing many eehinoid fragments. This rock 

 was succeeded by the deposition of the stratified Slonta Limestones, 

 which are represented near Cyrene by a soft cream-coloured num- 

 mulitic limestone containing iV. gizehensis, var. h/elli. This rock 

 appears to pass southwards into the harder brown-weathering 

 Slonta Limestones, which were formed in shallower water. The 

 Slonta Limestones contain Priabonian mollusca and an Echino- 

 lampas Bed, in which the common species is referred to E. cheriche- 

 rensis Gauth., of the Priabonian of Tunis. The deposition of the 

 Slonta Limestones was brought to an end by a stratigraphical 

 break, and the next series begins with a glauconitic marl containing 

 many rolled limestone-fragments. This bed passes upwards into 

 the yellow Cyrene Limestone, characterized by the abundance of 

 Operculina. That limestone is referred, from the evidence of the 

 molluscs and echinoids, to the Aquitanian. These beds are best 

 developed above the Fountain of Apollo at Ain Sciahat, Cyrene. 



Miocene rocks occur at Gubah, where they have been let down by 

 faults, and along the coastal plain east of Benghazi, where they lie 

 at the foot of the Tokra scarp. The country appears to have been 

 uplifted after the Middle Miocene, and to have become part of a 

 wide land which extended northwards and included Crete and the 

 ^Egean Sea. 



The land was afterwards broken up by great subsidences, which 

 left Cyrenaica as a horst, bounded by the fault-scarps on the 

 north and west, isolated from Crete, and sinking slowly southwards 

 to the Siwa-Aujila depression. 



The river-valleys in Northern Cyrenaica belong to an obsequent 

 system, the formation of which was probably started during a 

 period when the rainfall was heavier than at present ; but there 

 appears to be no evidence of any appreciable change in the climate 

 or water-supply of the country since the date of the Greek coloniza- 

 tion, which began about 620 b.o. 



EXPLANATION OF PLATE XLII. 



Fig. 1. Geological map of Cyrenaica, on the scale of 20 miles to the inch, or 

 1 : 1,267,200. 



2. Section from Benghazi to Derna. 



3. "Section from the Merj fault-scarp to the sea near Ptolemeta. 



