Vol. 59.] SEDIMENTARY DEPOSITS OF SOUTHERN RHODESIA. 275 



accordaDce with their physical features may be classified as 

 follows : — 



Tuli Lavas. 

 Coal-bearing beds 



(Unconformity). 

 Sarnkoto or veined sandstone? 



(Unconformity). 

 Mel amorphic rocks. 

 Gneiss and granite. 



III. The Physical Features and Grouping of the Rocks. 



From the sections described and figured and information acquired 

 by other means, it now becomes possible to sketch in the boundary 

 between the sedimentary rocks and the crystalline series, given in 

 the accompanying map (p. 276). Where that boundary has been 

 ascertained by me in the field, it is shown as an unbroken line ; but 

 these portions are necessarily small, and must be connected by 

 supposititious broken lines, until the accurate survey of the country 

 and subsequent exploration permit of filling them in definitely. 



Whether there is any correlation between the sandstones of 

 Nyasaland (mentioned by Prof. Drummond) or the sedimentary beds 

 found at Tete, some 250 miles down the Zambesi River, and those 

 of Matabeleland, I am not in a position to state ; but Livingstone 

 noted the similarity of some sandstones which he saw at Tete with 

 a deposit existing north of the Zambesi near Binga's Kraal. The 

 northernmost part that can here be given of this boundary-line in 

 Southern Rhodesia begins beyond the Sanyati River, where the 

 unconformity was noticed by Mr. Alford. It then takes a southerly 

 direction as far as the lower end of the Mafungabusi Range, crosses 

 the section shown in fig. 2 (PI. XIX) near the Djombi River, and 

 circles to the west round the Lower Gwelo gold-belt. A tongue 

 of fine sandstones then is found between the Gwelo and Umvungu 

 Rivers, Sonambula Forest ; the same rock occurs on the old Hunters* 

 Road north of Inyati, and it then runs between Shiloh and the 

 Queen's Mine. At Shiloh the contact with the metamorphic rocks 

 is masked by basalt. Another strip of sandstone runs over the 

 schist to form the prominent flat-topped hills near Bulawayo, known 

 as Thaba 'Sinduna, where, owing to the induration of the deposits 

 by igneous rocks, the beds have arrested denudation, and the hill 

 gives a section (to a height of 200 feet) of a formation that would 

 otherwise have been completely swept away. The investigation of 

 this hill with its siliceous secretions, agates, etc., should be one of 

 the first special objects of the local geologist. The contact then 

 runs west of Bulawayo through Helen Yale to Pasipas Mountain, 

 where a hard red siliceous sandstone is being extensively quarried 

 and supplies an excellent building-stone for that town. 



My next acquaintance with the sandstone is at Macloutsie River 

 on the railway-line ; but, before reaching that point, it circles round 

 the western end of the granitic Matoppo Mountains and the schists 

 of the Tati gold-belt, and is met with on the road to the Zambesi 

 Falls, to which it almost extends, forming a dry, sandy, barren 



