110 Repokt S.A.A. Advancembnt of Sciknck. 



irregular luii-«l claye}' tilins, ressinbling in origin such as I have seen 

 when river-sanl spits are uncovereil, an 1 sh >\v a slimy skin, wliich 

 subsequently becomes sun-cracked. Tlie grits break up rapidly ami 

 are very friable under atmospheric influence. 



No remains have been discovered in these beds. 



Cave Sandstone (Stormberg) f Forest .Sandstone (north), and 

 Bushveld Sandstone Series \ Samkoto Sandstone (soutli). 



This series has its largest development in the slopes towards the 

 Zambesi basin. At the Taba'sinduna the beds liave a northerly dip, 

 and there rest upon the rocks of the complex, and are evidence of an 

 overlap, either due to the filling of the Zambesi depression or the more 

 probable elevation of the Rhodesian axis during the last phase of the 

 Karroo period. The}^ are regarded as due to ieolian agency, and their 

 remarkable fineness and easy disintegration by atmospheric and vege- 

 table acids converts them readily into the fine mould of the forest 

 belts. 



In the Tuli district they occur innnediately over the coal beds. 

 There they are much indurated along definite lines, and thus arrest 

 decay to form ridges, or parallel " whalebacks "' running north-east and 

 south-west across the Limpopo into the Transvaal. These ridges ha\e 

 a very rugged and grotesque outline, and vinequal weathering turns 

 them into caves, swallow holes, towers and monoliths. Near Samkoto 

 bluff a columnar structure has been induced by one of the many in- 

 trusive dykes into the sandstone. 



[Batoka Basalt of tlie Victoria Falls and 

 Volcanic series - those of the Bubi, Gwampa, etc., and 

 I the Tuli Lavas. 



In tl\e northern occurrences geographical distribution serves to 

 join these ett'usive rocks into one category, while their position as 

 i-egards the Forest Sanflstone in the Limpopo and Zambesi basins is 

 the same. They can be seen at places in the north and at Van Wyk's 

 farm in th • Tuli district, to cover up an irregular surface of the sand- 

 stone. At the Victoria Falls their thickness exceeds loOO feet, and 

 the sheet extends as far as the Gonye Falls (200 miles west). 



They are generally characterised by amygdaloids, with cavities 

 filled by beautiful agates and chalcedonic forms and zeolites. Denser 

 slieets of olivine dolerite are intercalated. In the Tuli region the 

 typical pipe amygdaloid occurs, and Mr. Lamplugh mentions the same 

 from the Batoka gorge of the Zambesi, Tlie petrological features of 

 the volcanic rocks from that locality are described by Mr. H. H. 

 Thomas, B.Sc, F.(jr.S., in an appendix to the illuminating paper by 

 Mr. G. VV". Lamplugh, F.K.S. ((JiKo-ffrli/ Joiirtird of thfi deoloijical 

 Societi/, vol. Ixiii, 1907, }>p. K12 21(i). 



