Yol. S^.'] GEOLOGY OP THE ZAMBEZI BASIS'. 171 



IV. Geological- Structure. 



The main features in the geology of the region, so far as these 

 are known to me, are broadly outlined, without pretence to 

 accuracy in detail, in the accompanying sketch-map and sections 

 (PI. XVII). On this map the following rock-systems are repre- 

 sented : — 



(5) Kalahari Sand, with Chalcedonic Quartzite, etc. 



(4) Flaggy Sandstone of Boomka— ? Forest Sandstones (Molyneux). 



(3) Batoka Basalts. 



(2) Wankie Sandstones and Coal-measures =Matobola Beds and 



(?) Escarpment-G-rits of Molyneux. 

 (1) Fundamental Complex (granite, schist, etc.). 



From the map and sections it will he seen that the great floor of 

 ancient metamorphic and intrusive rocks, presumably pre- Palaeozoic, 

 which underlies the whole region and emerges around the rim of the 

 interior basin of Central South Africa, is deeply buried under newer 

 rocks in the portion of the Zambezi basin included within my 

 traverses. Except at one point, 3 or 4 miles south of the Wankie 

 coal-mine, at the extreme south-eastern limit of my journey, I gained 

 no opportunity for examining these oldest rocks in situ. The 

 overlying Matobola Beds or Ehodesian coal-measures I examined 

 in some detail, in their outcrop between the Wankie mine and the 

 Deka Eiver ; but elsewhere my routes lay almost entirely over the 

 basic lava-flows which constitute the Batoka Basalts, or over the 

 superficial detritus by which these basalts are partly covered. 



(1) The Fundamental Complex. 



From Livingstone's mention 1 of the presence of granite in the 

 upper part of the Kalomo river-basin, and of gneiss and mica-schist 

 dipping away respectively westward and eastward from this 

 granite-mass, we could surmise with some confidence that the 

 Tijarida Hills, which rose within easy sight to the north-east of us 

 after we crossed the Kalomo on our route north of the Zambezi, are 

 composed of the ancient rocks ; and I was disappointed not to find 

 the southward prolongation of this mass within our traverse. The 

 shape of the ground indicated that the basalts did not extend to 

 these hills (which for a time were not more than 10 or 15 miles 

 distant from us), but that at least in one place the volcanic rocks 

 ended off in a low escarpment fronting the hills. The only positive 

 evidence, however, that I obtained in this quarter respecting the 

 rocks to the northward of the basalts was from the detritus brought 

 down by the Kalomo and two other south-flowing streams farther 

 eastward, the Namaruba and the Grwemanzi. West of the Kalomo 

 Eiver I had found no trace of any rocks other than basalt and the 

 later chalcedonic quartzite in the stream-beds; and it was therefore 



1 'Missionary Travels & Researches in South Africa' 1857, chap, xxvii, 

 pp. 542, 543, & 548. 



AT 9 



