404 ME. W. GIBSON O'N THE GEOLOGY OF THE GOLD-BEAEING 



27. The GEOLOGr of the Gold-beaeing and Associated Eocks of the 

 SoTJTHEEN Teansvaal. By Walcot Gibson, Esq., F.G.S. 

 (Eead April 6tli, 1892. Abridged.) 



[Plates X. & XI.] 



Contents. 



Page 

 I. INTEODUCTION. 



(1) General Sketch of the Geology of the Southern Transvaal ... 405 



(2) Summary of previous Geological Work bearing on the District. 406 



II. GEOLOGY OF THE WITWATERSEANDT. 



A. The Gold-bearing Conglomerates and Associated Rocks op 



THE Johannesburg Area 409 



1. The District in General. 



2. The Main Eeef Series : — 



(o) The type-sections of the Main Reef Series in the 

 Salisbury and Henry Nourse Mines. 



(b) The Main Reef Series west of the Salisbury Mine. 



(c) The Main Reef Series east of the Salisbury Mine. 



3. The Gold-bearing Conglomerates south of Johannesburg: — 



{a) Second Reef Series, south of the Main Reef. 

 (h) Third Reef Series, still farther south, 

 (c) Beds near Germiston. 



4. The Conglomerates north of the Main Beef Series. 



5. TJie Lower Quartzite-and- Shale Group north of Johannes- 



burg, and its Belation to the Main Reef Series. 



B. Physical Relationships of the Witwatersrandt Rocks 423 



1. Belation of the Quartzite-and- Shale Group to the under- 



lying Bocks. 



2. Belation of the Quartzite and Conglomerate Series to the 



overlying Strata, 



3. The Faults, Dykes, and Igneous Bock-masses of the Wit- 



watersrandt. 



4. Summary of Observations and Conclusions respecting the 



Physical Belationships of the Gold-hearing Conglomerates 

 and Associated Bocks. 



III. GEOLOGY OF DISTRICTS OUTSIDE THE TYPICAL 



WITWATERSRANDT AREA 429 



1. The Chimes Mine and Heidelberg Districts. 



2. The Vredefort and Potchefstroom Districts. 



3. The Klerksdorp and Kroonstad Districts. 



4. The Igneous Bocks of the Southern Transvaal. 



5. Summary of Conclusions respecting the Belation of the Strata 



of the Neighbouring Areas to those of the Witwatersrandt 

 Series. 



