440 Annals of the South African Museum. 



erosion of the matter deposited, contemporaneous erosion, a pheno- 

 menon which is seen in thousands of cases throughout the Karroo 

 beds. At Indwe the upper layers of coal and shale are in places 

 missing, and the surface thus denuded is overlain by massive sand- 

 stone with pebbles at its base. 



The coals of the Molteno beds are usually laminated and contain 

 verv thin streaks of shale; they are coals which where formed verv 



, *J X 



probably at a considerable distance from the spot where the plants 

 grew, and the alternation of thin layers of coal and silt evidently 

 points to the vegetable matter having been deposited over the floor 

 of the basin in the same manner as the silt." 



In addition, it is well to give a few details with regard to the 

 stratigraphy in the various Divisions in which the beds have been 

 studied. 



Glen Grey, Queenstoicn & Wodehouse Divisions. In this area the 

 Molteno Beds are essentially arenaceous in character more so than in 

 the country to the north. The Indwe Sandstone forms the most 

 important subdivision, and sometimes the second thick sandstone from 

 the base, the Gubenxa Sandstone, can be identiiied. There is a 

 general thickening of the beds towards the south and south-east, as 

 is evidenced bv the fact that the thickness of the strata below the 



i/ 



Indwe Sandstone is 150-250 feet in Aliwal North, 450-500 feet at 

 Sterkstroorn and Indwe, 700 feet at Cala, and 1000 feet at Lady 

 Frere. 



The Indwe coal-seam is composed of a number of bands of coal 

 and shale, which are constant in character throughout the Indwe 

 mining area. The upper layers were in certain spots removed by 

 contemporaneous erosion. The "wash-outs" must have been formed, 

 according to Du Toit, by streams or currents of water flowing over 

 the seam of coal and shale while they were in a soft incoherent state. 

 The sandstone underlying the coal undulates, and thin layers of coal 

 and shale were spread over the surface and perpetuated the irregularities 

 beneath them. Krosion was most vigorous in the original gentle 

 troughs of the seam, and thus the top coals in these troughs are 

 no longer present, their place being taken by sandstone and grits. 



In the Northern portion of Wodehouse near the top of the Beds 

 is a hard fine-grained white sandstone with a few Tliinnfeldia fronds. 

 A similar bed is found at the same horizon in Elliot. 



Alhral North & Net self I. The thickness" of the Molteno Beds in 

 these Divisions is probably about 1000 feet. The Indwe Sandstone 



