466 Annals of the South African Museum. 



GENERAL CONSIDERATIONS. 

 CAPE-ORANGE FREE STATE-NATAL AREA. 



Molteno Beds. The chief features upon which stress must lie laid 

 in considering the Molteno Beds of this area are as follows: 



The formation dies out to the North, thinning from 2000 feet at 

 its most southerly outcrop to 140 feet along the northern Natal- 

 Basutoland border and disappearing altogether at Harrismith ; so that 

 its greatest North-South extent is just over 200 miles, an average 

 diminution of 10 feet per mile. How much further south it once 

 extended we cannot tell; the supposed occurrence of Molteno beds 

 at the top of the Great Winterberg, on the Fort Beaufort- Tarka 

 Divisional boundary has been disproved by a recent investigation 

 undertaken by the author. But that they extended well south of 

 their present outcrop is shewn by the occurrence on the coast near 

 Port St. John's of a down-faulted patch at least 1600 feet in thickness. 



The beds consist of sandstones, shales and mudstones which are gray, 

 greenish or bluish in colour, and lack any prominent calcareous con- 

 cretions or bands. In the south there is a great preponderance of 

 arenaceous beds, but towards the north the argillaceous deposits play 

 a more important, though still rather subsidiary part; it must be 

 noted that in Natal also the shales are inconspicuous. The sandstones 

 are coarse in grain, loose textured, and contain abundant felspar. 

 In the south they are coarser than in the north. The sandstones 

 occasionally contain nodules formed by the oxidation, and subsequent 

 hydration in the outer layers, of iron pyrites. Occasional conglomerates 

 occur, containing irregular boulders and pebbles which sometimes 

 rest on coal-seams partly imbedded in overlying sandstones. Such 

 pebbles are most abundant to the south-west. 



The workable coal seams all occur in the lower portion. The coals 

 are in thin layers alternating with thin black shales. They occupy 

 detached areas, their absence from some areas being partly explicable 

 by non-deposition and partly by contemporaneous erosion. 



The only fossils are plants, which seem more abundant in the 

 lower half of the formation. Animal remains have not yet been 

 definitely identified, although Dunn has recorded the presence of bones 

 at Molteno. 



These features all point to deposition under deltaic conditions, 

 either those of a true delta or of an aerial delta. 



Barrel 1 has pointed out that the determination of ancient true 



