Vol. 59.] SEDIMENTARY DEPOSITS OF SOUTHERN RHODESIA. 269 



Prom the extensive views that can be gained from any part 

 of the Great Escarpment it can be seen that across the Matobola 

 Yalley rises another line of broken hills, generally sloping, and 

 only occasionally showing a precipitous outline when viewed from 

 the south. This is the Mlambo and Sijarira range, and its axis 

 follows the same north-easterly direction, hence the escarpment, 

 plains, and hills are all parallel. 



Descending from the escarpment, and turning towards these hills, 

 the section crosses the plains, which are black in the winter season, 

 not only because of the natural darkness of the soil, but from the 

 ashes of grass and weeds burnt by the tires which yearly sweep 

 across their huge expanse. The plains undulate gently, with a 

 general northerly slope, and thus the deep erosion of the river and 

 the general upward tilt of the rocks being in the same direction, the 

 underlying strata are one by one brought to view. 



The traverse thus comes to the lower series (Lower Matobola 

 Beds) of black shales and clays, with workable seams of coal, which 

 are of great extent and are referred to later (p. 281). The two series 

 of fine carbonaceous beds are separated by a deposit of micaceous 

 ferruginous sandstone, with grits and conglomerates, forming a con- 

 tinuous and low ridge for many miles : this group (Busse Series) 

 yields the fish-remains described in Appendix I, p. 285. 



The coal-bearing beds lie upon a group of derived rocks, generally 

 of a coarse sandy composition, showing much current-bedding, but 

 with occasional patches of shales and sandy clays, altered sometimes 

 into quartzites. 



In continuation of the section north from the coalfields the 

 strata become more highly tilted, until they break off at the 

 summit of Gongoriba and Chongola Mountains. Quartzites then 

 come in, and form the southern and northern slopes of the Sijarira 

 Plateau or Range. The centre of that tableland resumes the normal 

 condition of loosely-coherent sandstones, with horizontal strati- 

 fication, but the north-western edge shows the rocks to have again 

 become indurated. Here they are also folded and fissured, and 

 seem to be near the axis of an anticline, but only a few folds now 

 remain visible at the top of the precipitous mountain. 



Prom this point there is a quick descent of 1400 feet in a 

 few miles, and the steep northern slope of this mountain-range, 

 extending from the Lubu Gorge (see PI. XIX, fig. 3) to the Sengwe 

 Ptiver, about 60 miles, is a prominent feature of this district, for 

 only low broken country now intervenes between it and the Zambesi 

 Ptiver, which it overlooks 35 miles away. On descending the 

 mountain the loose, irregularly-bedded sandstones are seen to be 

 horizontal, and there is no sign of the disturbance which folded the 

 rocks at the apex of the range. 



Prom the base of the range the coarse current-bedded sandstones 

 continue until the Zambesi is reached, with local and intermittent 

 zones of quartzites or indurated finer sediments. The thickness of 

 the series, measured downward from the base of the coal-bearing beds 

 to the level of the Zambesi Yalley, must be at least 2000 feet. 



