﻿Yol. 66.'] GEOLOGICAL STETTCTTJEE OF SOUTHEEN EHODESIA. 369 



(c) The Forest Sandstones. 



The predominantly arenaceous beds to which the name Forest 

 Sandstone is here applied are much more extensively developed 

 than the other Rhodesian sediments, and they are the only ones that 

 occur on the high plateau which forms the backbone of Southern 

 Rhodesia. The map indicates their distribution with considerable 

 accuracy, although it has been impossible to distinguish the over- 

 lying Somabula gravels and sands over part of the area. It is also 

 probable that the inliers of granite and schist are more numerous 

 and extensive than is represented. At the same time there is little 

 hope of the coal-bearing beds being exposed underneath the Forest 

 Sandstone in any of the inliers, as the overlap of the latter on the 

 scbists and granites appears to commence very close to the known 

 coalfields, as for instance at Mbanji, south of Wankies, and at 

 Mafungabusi. It seems highly probable that there is an uncon- 

 formity at the base of the series, but its true base has never been 

 defined. All the exposures known to me which show its relation 

 to older rocks are junctions with the metamorphic schists or with the 

 granites. North of Bulawayo there are a number of such sections 

 within 20 miles of the town. 



Like the other sediments, the Forest Sandstones appear to be 

 absent or but feebly developed to the north of Mashonaland. So 

 soon as the Sanyati River is crossed, however, and one enters 

 Matabeleland, they appear in force, and cover much of the country 

 in the Mafungabusi and Sengwe districts. There, is an outlier 

 between the Jombi and Ifafe Rivers, consisting of red flaggy sand- 

 stones overlying pale gritty beds with bands of conglomerate near 

 the base, the actual base being a bed of coarse felspathic grit resting 

 upon granite. The main southern boundary runs along the Ifafe 

 River, and then westward towards the Shangani junction. A long 

 tongue, of which the tip is composed of Somabula gravels, etc., 

 stretches out south - eastwards for many miles towards Gwelo, 

 approaching within 10 miles of that town. About 5 miles north of 

 Gwelo there appears to be an outlier 4 or 5 miles wide, trending in 

 the direction of Enkeldoorn, between which town and Charter 

 occurs the only outlier that is close to the axis of the plateau on its 

 south side. Turning again to the main body, its boundary appears 

 to run south-westwards after leaving the Shangani towards the 

 Bubi, after crossing which it turns due eastwards again, until it 

 meets the Bembezi nearly due north of Bulawayo. It then runs 

 back south-eastwards again towards the Queen's Mine, about 3 

 miles west of which a long narrow tongue stretches to within a few 

 miles of the Zambezi-Limpopo watershed, terminating in the 

 Amanxele Hills, which consist of white sandstone capped by basalt. 

 A very irregular course is then taken across the Koce and Umguza 

 Rivers to within a few miles of the Khami at Pasipas, where the 

 beds dip northwards at about 30° and consist of white massive sand- 

 stone, overlain by red flaggy beds. Outliers occur on the south at 

 Umfazumiti Hill (white sandstone resting upon schists) ; near the 



