XCvi PEOCEEDINGS OF THE GEOLOGICAL SOCIETY, [vol. Ixxvii, 



June 8th, 1921. 



Mr. E. D. Oldham, F.R.S., President, 

 in the Chair. 



The List of Donations to the Library" was read. 



Dr. William Fraser Hume opened a discussion on the 

 Relations of the Northern Red Sea and its Associated 

 Grulf- Areas to the 'Rift' Theorj^, in the following words: — 



(1) The areas specially considered are the northern portion of 

 the Red Sea and a region to which the name of ' Ch'smic Gulf ' 

 has been given. The Clysmic Grulf (from Clysma, the Roman 

 name for Suez) is defined as the district bordering the Grulf, and 

 lying between the (largely) fault-bounded ranges of Egypt and 

 Sinai on the west and the east respectively which dominate this 

 depressed area. Within its borders Miocene deposits are of wide 

 distribution ; beyond them, these are notably absent. The folds 

 within this region are from north-west to south-east, outside it 

 their trend is frequently almost at right angles. 



(2) A line prolonging the direction of the western coast of the 

 Grulf of Akaba to the shores of Egypt divides the Clysmic Gulf 

 from the Red Sea, the former being occupied hj the shallow Gulf 

 of Suez and disturbed lowlands, Avhile south-east of the dividing- 

 line is the Red Sea, with its great depths and its narrow coast- 

 line. 



(3) The Clysmic-Gulf area is one of complicated fold-and- 

 f racture effects, while in that of the Red Sea only fold effects have 

 been observed. 



From a study of the facts known, it is concluded that : — 



(4) The whole region under consideration underwent extremely 

 slow submergence, the negative movements continuing from 

 early Jurassic to late Cretaceous times. 



(5) This was succeeded by one of a positive nature, the actual 

 emergence of the new land taking place near the close of the 

 Eocene Period. It is suggested that the area was occupied by an 

 anticline or anticlinorium plunging northwards in the Cl^^smic- 

 Gu]f region, and that it was subject first to marine and then to 

 subaerial erosion. This formed part of the continent on which 

 grew the trees of the Petrified Forest, and on which wandered 

 animals such as the Arsinoitlieriicm and the earliest elephants. 

 This continental period was most marked during late Eocene and 

 early Miocene times, and the area dealt with here appears to have 

 become one of ver}" varied ridge and depression. 



(6) The whole region thus dissected was invaded by the ancient 

 Mediterranean ; the slow advance southwards occupied the main 

 jDortion of the Miocene Period, and probably extended well into 

 the Pliocene. The pre-existing ridges became coral-reef centres : 

 the intervening depressions were filled up, first by land-derived 



