100 NEW YORK STATE MUSEUM 



Encyclopedia Britannica (1910, p. 323) states this fact as a salient 

 feature of the geology of Africa. 



The Precambrian basement complex, overlain unconformably by 

 Mesozoic or younger sediments, but forming the surface rock over 

 vast stretches of land, extends from the region just discussed east- 

 ward to upper Egypt (Khartum) and the shores of the Red sea, 

 southeastward to former German East Africa and southward to 

 South Africa. 



Wherever in these wide areas data on the strike of the Precambrian 

 folds, foliation and major axes of intrusives become available, a 

 dominant north-south direction is apparent. For Nigeria and 

 western Liberia we have the investigations of J. Parkinson (1907, 

 1908). From the Oban hills in southern Nigeria (adjacent to 

 Kamerun), this author gives fifteen measurements of strikes of 

 foliation throughout the large district; all of these strikes have the 

 north direction as their main component, and the average direction 

 is less than one degree west of north. Locally, as in the Kukuruku 

 hills in southern Nigeria where the two measurements of the foliation 

 of the gneiss that were made gave N 45 W, considerable variation 

 may occur, which, it seems, increases as the sea coast is approached, 

 as in western Liberia, where Parkinson found a mean foliation 

 striking N 68° E Gurich (1887, p. 119, 120) reports a north- 

 south strike of gneiss from several localities on the Niger below the 

 mouth of the Benue. A large portion of the Congo Free State 

 has been traversed to the Nile by Preumont (1905, p. 641). He 

 found (ibid., p. 655) that in this northeastern portion of the Congo 

 basin " the granitic and metamorphic primary rocks are present 

 across the whole country from east to west and from north to south, 

 uncovered by any other rocks except the alluvial sands and clays 

 and the nearly related ferruginous rocks." Wherever the strike 

 of the gneisses and other metamorphic rocks is mentioned, it is 

 north-south and it is expressly stated (p. 653) that also in the valleys 

 of the Kidju and the Kaja, western tributaries of the Nile, " whole 

 series of gneisses and metamorphic rocks are met with, striking nearly 

 due north and south." In the Nile valley itself, north of Lake 

 Albert and south of the Sudan, a N 40 W strike was found to be 

 " both regular and persistent." 1 



Dantz (1907, p. 46) found an enormous area of gneiss developed 

 in northern and central German East Africa, consisting of a central 



1 A. Holmes (The Pre-Cambrian and associated rocks of the District _ of 

 Mozambique; Quar. Jour. Geol. Soc. London, 74:33, 1918) has found the strike 

 in Mozambique to be most commonly along, or a little north of a northeast 

 to southwest direction; though in the Ribawa district and near the coast belt, 

 it swings around to a nearly north and south direction. 



