REPORT OF THE DIRECTOR I92O-2I 99 



traced to the bend of the Niger by Chadeau, throughout Dahomey 

 by Huber, it is known along the Niger between lats. 15 30' and io° 

 30' and the same structure may be also seen in a great part of Togo 

 (see Suess-Sollas ibid.). 



More recent investigations in other districts of Central Africa 

 fully corroborate this general north-south direction of the Precam- 

 brian trend lines. Thus Williams (1920, p. 436) found in northern 

 Nigeria, in the Ningi hills southwest of Lake Chad, a general north- 

 south foliation and a north-south direction of the longer axes of the 

 granite intrusions. A local foliation in equatorial direction (near 

 Kem Filani) is, according to this author, probably induced by the 

 (Mesozoic) Ningi granite, the longer axis of which is due east-west, 

 along its contact with the Precambrian gneiss. 



There is some doubt as to the age of these meridional Precambrian 

 folds of the western Sahara and Nigeria. They have been found 

 to be overlain by undisturbed Devonian beds and in a few localities 

 also by Upper Silurian graptolite shales. On account of their 

 Predevonian age and meridional direction, they have been compared 

 with the Caledonian system by Haug (see Suess-Sollas, p. 95). 

 Suess, accepting this view, points out that while the Caledonides 

 in Europe are Predevonian in age, the folds of western Africa are 

 Preupper-Silurian. He continues: " In accordance with the prin- 

 ciples of tectonic classification we have hitherto adopted, we may 

 assign them to the submeridional, sublinear system which was 

 completed in Europe before the deposition of the Devonian, and in 

 Africa even before that of the Upper Silurian. It may, however, 

 be objected that the unconformity at the base of the African ranges 

 may be much older than the graptolite shales; we shall therefore 

 term them, following a suggestion in an instructive letter from 

 M. Chadeau, the Caledonides of the Sahara or the Saharides." 



It follows from this statement that the age of these folds 

 is not known. All that is known is that they are Preupper- 

 Silurian in age. We believe to have good reasons for concluding 

 that they actually are of Precambrian age. While Suess refers 

 only to the north-south direction of the Archean belt extending 

 through the western Sahara and Nigeria and Togo to the neighbor- 

 hood of the gulf of Guinea, one should consider in the same con- 

 nection the north-south direction observed in areas outside of this 

 belt, as farther east near Lake Chad (Williams), in southwest 

 Africa and East Africa (see below). In fact, the predominant strike 

 of the foliation is so widely north-south in central Africa that the 

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