Yol. 59.] SEDIMENTARY DEPOSITS OF SOUTHERN RHODESIA. 267 



Their extent is so considerable that the close examination of them 

 must prove an arduous undertaking, and necessitate a large staff of 

 observers as well as a great expenditure of time. In traversing the 

 country, however, I have noted, as carefully as possible, such facts 

 as came under my observation, and have obtained sufficient inform- 

 ation to serve as an introduction to the geology of this portion of 

 Southern Ilhodesia, which is especially interesting at this time, as 

 the sedimentary rocks are associated with large areas of workable 

 coal, and also because of the recent discovery of certain fossil 

 remains, which form the subject of appendices to the present paper. 



"While the country along the watershed has been correctly 

 surveyed and mapped, and is thoroughly well known owing to the 

 mining industry now being conducted there, the area of the 

 sedimentary beds is almost unexplored, and the maps of Rhodesia 

 to the north and south of the gold-belts are made up from sketches 

 furnished by hunters, for, with the exception of the coal- outcrops, 

 prospectors and miners find no inducements to visit this region. 



The best method of showing the general order of stratification 

 of these deposits is to draw attention to a series of sections made in 

 travelling over these areas. The main section forms a complete 

 illustration of the country from the Zambesi River on the north, 

 through Bulawayo and the central plateau, to near the Limpopo River 

 on the south, a distance of over 400 miles. Others illustrate the 

 arrangement of strata in the northern districts, parallel to the 

 main section, and also in the south, and illustrate the contact of 

 the sediments with the schists and crystalline rocks, which form the 

 basement-system of this portion of South Africa. 



By these sections the line of the ' great unconformity ' is intersected 

 on the north at places 100 miles apart, and again on the south-west; 

 and it is thus possible to arrive at some definite and important 

 conclusions regarding the general arrangement, order of deposition, 

 and thickness of the sediments lying in the low country which now 

 nearly surrounds the elevated plateau of Southern Rhodesia — the 

 lowlands towards the eastern coast excepted. 



II. The Northern Sediments. (PI. XIX — sections.) 

 [Geological sketch-map on p. 276.] 



ITain Section (PI. XIX, fig. 1). — This is drawn along the main 

 road from Bulawayo through Shiloh to the Sengwe Coalfield, a 

 direction almost due north. The town of Bulawayo lies at an altitude 

 of 4469 feet, on the metamorphic rocks which form the auriferous 

 area known as the Bulawayo gold-belt. On taking the 

 northern road a strip of very fine sandstone is seen to begin about a 

 mile beyond the Umgusa River, 6 miles distant, and occupies a ridge 

 some 4 miles wide. This is a westerly extension of the Thaba 

 'Sinduna Series, which forms the conspicuous flat-topped hill lying 

 about 12 miles to the north-east of the town, overlapping the schists. 



This sandstone constitutes the highest-remaining horizon of the 

 Mesozoic formations in Rhodesia, and east of the road there is 



t2 



