456 ME. W. n. PENNING ON THE 



into the Free State ; indeed, it has been the chief clue in following 

 and identifying the " Main Keef " from the Hand, west, east, and 

 south, for some 200 miles. 



There are talcose and chloritic slates, which, if not so persistent 

 as the magnetic beds, maintain their relative positions for great 

 distances, and micaceous sandstones, by which certain " banket '' 

 series can be recognized, — also most of the " reefs" contain pebbles 

 of a distinct character, and one set of conglomerates differs from the 

 others in enclosing numerous angular fragments of shale. 



(b) The Klip-lliver Series. — This series of rocks (e), previously 

 called by me the " Megaliesberg beds," proves to be part of a larger 

 " Megaliesberg formation," which includes the equivalent of the 

 " Klip-Uiver " (or upper) series, and the " Witwatersrand " (or 

 lower) series already described. It consists of " shales and flag- 

 stones, fissile and thin-bedded, which generally are grey, but weather 

 to yellow, or dirty-yellow, or dirtj'-brown. In some localities, as 

 along the valley of the Eland's Spruit, there occurs a series of cherts 

 and quartzites, which appear to replace the lower shales " *. These 

 cherts and quartzites also form the lower part of the series around 

 Pretoria and at the Klip Eiver, the shales being in much greater 

 force (where first observed) in the Lydenburg district ; there occur 

 throughout numerous interstratified traps, sometimes of great thick- 

 ness. This series is at least 18,000 feet thick ; and from its southern 

 edge, by the granite near Pretoria, across the mountains from which 

 the formation derives its name, it is actually seen, and its thickness 

 can be determined, independent of any inference as to the curve 

 formed by underground extension. 



Near its base, this series has a distinctive " banket," called the 

 *' Black Reef," amidst sandstones and quartzites, which again are 

 overlain by a peculiar rock, which I described as chalcedolite t, in 

 connexion with the Lydenburg district, and which confirms my 

 opinion of that area forming part of the Megaliesberg formation. 

 By weathering it often presents most fantastic characters. This 

 chalcedolite, including the "Black-Eeef " banket, comes close to the 

 granite south of Pretoria, the whole of the lower series being 

 absent ; and, as it seems impossible for the latter to have abso- 

 lutely thinned away, and improbable for it to have been entirely 

 overlapped against the mass of granite, I have come to the conclusion 

 that it is faulted down, and must exist below in its relative position. 



The base of this series, generally conformable to that below, is 

 traceable on the south along the valley of the Klip River (whence 

 its name), then across the Yaal, here and there under the Coal- 

 formation, into the Free State, and again into the Transvaal near 

 Klerksdorp ; here it is faulted down against the lower series of 

 rocks which then dip westward. This is perhaps a mere local 

 disturbance, but it may indicate the commencement of another 

 basin, in which, as previously suggested (p. 455), the Megaliesberg 

 formation may be carried in that direction to a great distance, to 

 reappear possibly even so far west as Bechuanaland. 



* Quart. Journ. Geol. Soc. vol. xli^ (1885) p. 576. t Ibid. 



