REPORT: OF. THE DIRECTOR I92O-2I 1.0,1 



area where the strike is " more frequently NNW-SSE- than from 

 W-E, and a peripheral zone with prevailing WNW-ESE strikes." 

 Tornau (1907, p. 65) designates much of this rock as typical granite, 

 a fact which may explain the varying strike of the peripheral zone. 

 For Rhodesia, in southeastern Africa, Chalmers and Hatch (1895, 

 p. 200) furnish some data.. Wherever the strike of the Precambrian 

 is given, usually in connection with that of the strike of the metalli- 

 ferous veins, it is north-south or northwest-southeast. 1 



In German Southwest Africa, Voit (1905, p. 85) found a vast belt 

 of gneiss and schists, which he refers to the Archean era. . These 

 metamorphic rocks are folded (see plate 23) and the folds and their 

 massive granite injections have a general, northeast-southwest 

 strike, which locally (see p. 97) changes to a north-northeast — 

 south-southwest direction. 



It is to be noted that this territory of German Southwest Africa 

 adjoins South Africa where a younger system of east-west folds has 

 developed but where, as Voit (1906, p. 106) observed, also the 

 " Fundamental gneiss " is exposed in the Limpopo flats and there 

 exhibits a vertical position and east-west strike. The significance of 

 this east- west strike of the fundamental complex in South Africa will 

 be. discussed in an other connection. Suess (1909, p. 322), following 

 Rogers, Schwartz and Voit, describes the syntaxis of the ancient 

 (probably Prepermian) southern and western marginal mountain 

 ranges; the southern range (the Zwarte mountains) is folded from 

 south toward north; the western (Cedar mountains) strikes north- 

 northwest and the folding is from west. The north-northwest 

 strike of the Cedar mountains continues far north, across the Orange 

 river, in the gneiss. 



The geology of Africa may be summed up in the words of Gibson 

 (1910, p. 323): " The crystalline massif presents a solid block which 



1 For the Precambrian terranes in the Egyptian desert region east of the Nile 

 river and the Sinai peninsula, the facts have been assembled by Max Blancken- 

 horn in the " Handbuch der regionalen Geologic " (Aegypten. 9, Abt. 23 

 Heft. Heidelberg 1921).' Blanckenhorn finds that there is no uniform strike 

 of the beds and mountain chains but repeated, abrupt changes, connected with 

 dominant faults. He records, however, a south-southwest strike of the gneisses 

 on the east side of the Sinai (ibid., p. 27), a north-south or north-northwest to 

 south- southwest trend of the mountains west of the Suez canal and a north- 

 south trend of the granite massives west of the Red sea (ibid., p.. 31). There 

 occur also fault blocks with east- west and northeast-southwest strikes of ±he 

 Precambrian rocks. 



To the north of German East Africa, directly south of Abyssinia, J. Parkinson 

 (Geology and Geography of the Northern Part of the East Africa Protectorate, 

 with a note on the Gneisses and Schists of the District. Colonial Reports. 

 Misc. no. 91, East African Protectorate, 1920, p. 20) has lately reported granitoid 

 gneisses and other Precambrian rocks in strong development. The strike of 

 the gneisses is mostly north-south or north-northeast in some districts; the 

 quartzites of the Turoka series, however, strike northeast. 



