548 Professor Sc/iicarz — Earth-iDOvements, S. Africa. 



Red Sea, wliicli is a rift-valley belonging to the great ludo-African 

 frajiraentation, has sunk in Pleistocene times, at least the noi'therii 

 portion ; in this case, however, the rift had already formed long 

 previously, and the fact that the sea invaded the trough only in 

 Pleistocene times merely indicates its depression below an arbitrary 

 datum depending on the amount of sea-water upon the globe. The 

 bottoms of other rift-vulleys, such as those in Central Africa, are 

 much above sea-level, as others, for instance that off the coast of 

 South Africa, are much below. That movements should happen in 

 Pleistocene times in these troughs is a natural consequence of the 

 strained equilibrium resulting in large movements in the earth's 

 crust, and may be regarded as 'posthumous' movements along lines 

 of weakness formed long anteriorly, just as the fold of the Weald in 

 the South of England is a posthumous fold which followed lines of 

 folding that was brought to a close in Carboniferous times. What 

 I wish to establish is that the general fragmentation of the Iiido- 

 African continent took place in pre-Miocene times and was finished 

 in pre-Pleistocene. 



The next event in South Africa of which we have any evidence is 

 a peneplane now elevated 4,000 feet above sea-level. Only river 

 gravels are found upon it, and these quite barren of organic remains. 

 It is extensively developed on the inside of the coast ranges, and 

 extends along the escarpment of the Karroo Beds in Fort Beaufort 

 and King Williamstown ; from Grahamstown it may be seen as 

 a sharp line below the 6,000 feet level of the Great Winterburg and 

 Amatolas. The 4,000 feet peneplane is thus a level of general 

 denudation, and implies that the land stood at this level above the 

 sea ; it is quite different from the 4,000 feet level on which the Lower 

 Cretaceous beds, the Enon conglomerate, was deposited, for this new 

 4,000 feet level cuts off the tops of the tilted Enon conglomerate and 

 covers them with remanie gravels lying perfectly horizontally. We 

 do not know the date of this plain because there are no organic 

 remains in the gravels and sands with which it is covered, btit tlie 

 land was now again rising, and after cutting a very widespread 

 peneplane at 2,500 feet above present sea-level, it rose to 15,000 feet 

 above sea-level, whtn for the first time the Alexandria Beds, Mio- 

 Pliocene, were deposited. The second 4,000 feet peneplane is thus 

 about Oligocene or early Miocene. 



Erom the 1,500 feet plain or coast shelf — for now the plains are 

 no longer extensive peneplanes but narrow shelves fringing the 

 coast — there are a succession of ledges cut at intervals of 50-100 feet 

 downwards, extending like the steps of a flight of stairs to below 

 sea-level. As our coast surveys show the sea-floor carved into 

 narrow river gorges down to 400 fathoms, one may perhaps be justified 

 in concluding that this level was at that time exposed as dry land. 

 The submarine contours show that at 400 fathoms the old Mada- 

 gascar ridge was connected to the Cape Peninsula, and that river 

 coui'ses ran both to the east and west from the narrow connecting 

 ridge. Erom a general view of these contours one may infer that 

 the river system at the time of maximum elevation was somewhat 

 different from what it is now : only two rivers, the Gouritz and 



