W. Gibson — Age of the Hand Beds. 549 



The sequence in the Southern Transvaal is as follows, in 

 descending order : — 



1. Gat's Rand Beds, Megaliesberg Beds. 



2. Kand Beds. 



3. Quartzite and shale group (Hospital Hill Series). 



The Gat's Rand series are now considered to be unconformable to 

 the Rand Beds. A dolomite from which Mr. Draper^ has obtained 

 fossils of doubtful Carboniferous species is associated with the Gat's 

 Eand Beds. It is only the age of the Rand Beds that is here 

 considered. 



As investigation is carried on among these rocks, they are found 

 in several areas to be more strongly affected by mechanical move- 

 ments than any of the rocks newer than the Table Mountain 

 Sandstone of Cape Colony.^ In the Cape, the folding of the Table 

 Mountain Sandstone and overlying Paleozoic rocks is of Post-Karoo 

 age, the Karoo beds being involved in the folds.^ Where the Karoo 

 beds exist in the vicinity of the highly inclined and altered Rand 

 Beds, they are nearly horizontal or but slightly inclined. It would 

 therefore seem that the deformation of the Rand Beds is older than 

 the folding of the Pal;eozoic rocks of Cape Colony. 



Another fact in favour of the great age of the Rand Beds is the 

 intrusion into them of basic dykes, which have been converted by 

 pressure into hornblendic and chloritic schists. In the Cape Colony, 

 igneous intrusions, so far as I am aware, are absent from the 

 formations between the base of the Table Mountain and the top of 

 the Zwartebergen Group, while the dykes and sills piercing the 

 Karoo beds are unaltered. Igneous intrusions, in beds older than 

 the Karoo, are confined in Cape Colony to the Malmesbury Schists. 



The rocks in Cape Colony that appear to have the closest litho- 

 logical resemblance to those of the Rand are some slates, grits, and 

 sheared conglomerates found in the Prince Albert Region. These 

 are doubtfully considered by Dr. Corstorphine to overlie the 

 Zwartebergen Quartzites,'' but as a dolomite is associated with 

 these grits and conglomerates, they would appear to represent the 

 Megaliesberg Group. 



Up to the present date the Rand deposits are generally considered 

 to be represented by some portion of the Table Mountain Sandstone 

 series. If so, in the Transvaal there are evidences of a complex 

 series of folds and overthrusts of Pre-Karoo age unrepresented in 

 Cape Colony, except perhaps in the Malmesbury Schists. On the 



1 D. Draper, "The Occurrence of Dolomite in South Africa" : Quart. Journ. 

 Geol. Soc, vol. XV, p. 561, 1894. 



- W. Gibson, " The Geology of the Gold-bearing and Associated Rocks of the 

 Southern Transvaal": Quart. Journ. Geol. Soc, vol. xlviii, pp. 404-37, 1891. 

 W. Gibson, "Geology of the Southern Transvaal": Trans. Fed. Inst., vol. vi, 

 p. 124, 1893. A. E. Sawyer, " Remarks on the Banket Formation at Johannesburg, 

 Transvaal" : Trans. Fed. Inst., vol. ix, p. 360. 



* E. H. L. Schwarz, " First Annual Report of the Geological Commission of the 

 Cape of Good Hope for 1896," p. 28. 



* Dr. G. S. Corstorphine, " First Annual Report of the Geological Commission of 

 the Cape of Good Hope for 1896," p. 31. 



