3^ PRESIDEXTIAI. ADDRESS SECTION P.. 



Zeiller in 1895 pointed out their identity with members of the 

 same flora in India, and also that 



"there is a remarkable association in Brazil, of such t\pical members 

 of the Glossoptcris flora as Gangainopicris and Ncuroptrridiuiii with a 

 common Upper Carboniferous plant of the Northern Hemisphere Lcpido-. 

 pJioics laricinus" 



the significance of which will he dealt with later. 



In Sontli Africa deposits that are homotaxial with similar 

 beds in India and Australia are widely developed in the Karroo, 

 which gives a name to the system in this part of the world. The 

 maximmn thickness in the Cape Colony is given by Dr. Rogers 

 as 15,000 feet, including the volcanic beds outpoured during 

 tl]e concluding phase of the .Karroo S3'stem. 



Compared witli the periodic arrangement of the Northern 

 Hemisphere, deposits began to accumulate in Upper Car- 

 boniferous times, were gaining in thickness during the whole of 

 the Permian, covered the Rhcetic, and closed in Lower Jurassic 

 times : the Karroo age thus embracing several of the periods of 

 the northern world, and shewing it to be of great duration in 

 time. Professor R. IJroom estimating it at two million years. 



What of the floor upon which the Condwana continent was 

 built up? It varies much in structure from the Cape coast to 

 tlie Zambesi, and \vhile in the former locality there are older 

 formations that have been investigated by Dr. Rogers and the 

 meml)ers of the Cai:)e Survey, in Rhodesia we have not yet 

 worked out the component systems of the great mass of pre- 

 Karroo rocks — a problem that awaits elucidation. Some masses 

 are metamorphic and folded, others shew no sign of alteration, 

 but between their deposition and the oncoming of the lowest 

 Karroo rocks there is a bridge that may span many chapters of 

 the geological record. There is no evidence to show that 

 Rhodesia had been submerged under the ocean since remote 

 geological periods, and even the deposition of the Karroo beds 

 on its surface does not imply a reduction to gea-level, but rather 

 continental conditions. The anti(|uity of this part of the con- 

 tinent is therefore extreme. 



The geology of the Cape Colony afl:'ords some light on this 

 subject*. During the early Palaeozoic times marine conditions 

 prevailed over the southern portion, but the connection wath the 

 ocean became cut ofl:', the water shallowing to receive the sedi- 

 ments of the \\'itteberg and the lowest strata of the Dwyka 

 conformably. (jradually the land rose from the level of the 

 barricaded ocean for the last time after the oscillations of pre- 

 vious ages. 



This emergence was probably due to a spreading elevation of 

 the Antarctic Continent to embrace the area of the South 

 Atlantic Ocean, Australia, the Indian Ocean and the Cape. In 

 the latter area the lanrl. after emergence, formed a great inland 

 l)asin or lake. ]Mountain ranges existed beyond the Orange 



-■'■ .Sl'c ■■ 'riie Gcologv of llie Cape Colonv." Rogers and Du Toit, 

 1909. 



