The Sedimentary Deposits of Southern Rhodesia

Abstract

I. Introduction. Southern Rhodesia lies between the Rivers Zambesi and Limpopo where they approach nearest to each other, a distance of 400 miles. Its greatest breadth is from the Victoria Falls on the west to the 33rd degree of longitude on the east, a distance of 450 miles, and it has an area of 192,000 square miles. The major portion of this extent is occupied by grey granite and gneiss, and by the metamorphic schists and slates that contain the numerous quartz-veins extensively worked by an ancient people, and now being again opened up for the extraction of gold and copper. The area over which these rocks occur measures 140,000 square miles, the remaining portion being taken up by sandstones and volcanic rocks. Whatever may have been the original condition of the slates and schists of the gold-belts, igneous or sedimentary, they are now so indurated and cleaved by lateral pressure that their present state only is recognized in this paper, and they are referred to as schists or metamorphic rocks, or when associated with the granites and gneisses, are included in the term Archæan rocks. The slates lie at an almost vertical angle, and the lapse of time and vast amount of erosion that took place before they were covered by the deposition of the sedimentary beds now to be described (which, in striking contrast, lie at low angles or horizontally) give rise to the ‘great unconformity’ of Rhodesian geology. The Archæan rocks of Rhodesia have frequently formed the