314 SECTIONAL TRANSACTIONS.— C. 



The fluids, hot and chemically active, converted the more argillaceous slates into 

 tourmaline rocks, while more calcareous types became calc-silicate hornfels with the 

 development of axinite, epidotes and garnets. The granites and porphyries were also 

 attacked and gave rise to tourmaline-bearing rocks, greisens or china-clay. 



The mineral lodes also belong to this period of activaty, and their contents vary 

 with their position relative to the granite surface. Certain zones can be established : — 

 i. iron-manganese zone, 

 ii. lead-zinc-silver zone, 

 iii. copper arsenic -wolfram tin zone. 

 i and ii are found above the granite surface, whilst iii, which can be further subdivided, 

 passes from just above the surface to well below it. Two types of veinstone are 

 . common ' Peach,' a chlorite-quartz veinstone, rich in cassiterite, and ' Capel,' a 

 brecciated tourmaline-quartz rock. 



Dr. G. Slater. — The Glaciated Rock-surfaces of Nooitgedacht, and the Upper 

 Dwyka Boulder- shales of Griqualand West. 



I. Nooitgedacht is the name of a farm situated on the left bank of the River Vaal, 

 a dozen miles north-west of Kimberley. A small area of the farm is occupied by a 

 subsidiary valley a mile in length, which exhibits striking evidence of a ' fossil Glacial 

 Landscape ' of Carboniferous age. The valley is a rock basin with a glaciated floor, 

 subsequently converted into a glacial lake with deposition of varve-shales. The 

 surface of the floor is now a limonitic pseudomorph, which has preserved all the 

 evidence of abrasion and polishing by land ice such as : — Striations, chatter-marks, 

 differential abrasions, grooves, and glacial shelves. Isolated bosses of rock exhibit 

 examples of crag and tail associated with roches moutonnees. 



This area has now been protected, thanks to the public spirit of the De Beers 

 Corporation, Kimberley. 



II. The Upper Dwyka Boulder -shales. The line marked by the Harts- Vaal-Orange 

 Rivers from Vryburg to Prieska marks the drainage system of the pre-glacial Kaap 

 Valley which guided the Transvaal Ice Lobe south-west. Retreat of the ice was 

 followed by invasion of the sea or lake, resulting in the deposition of the Upper 

 Dwyka Boulder-shales to a maximum depth of about 200 feet. 



These bedded shales are interspersed with numerous erratics of all sizes dropped 

 from floating ice. Near the base of the shales are lenticles of tillite-like material, 

 microscopic examination of which throws new light on glacial sedimentation. 



At Douglas the shales contain ' boulders ' of tillite-like material, and these beds 

 are overlain by varve-shales with cone-in-cone structure in the calcareous layers. 



Infra-formational Folding. At De Kalk on the Riet River a fine section of the 

 Upper Dwyka Boulder-shales exhibits infra-formational folding in the lower part of 

 the exposure, apparently due to the stranding of ice-floes or pack-ice possibly associated 

 with pressure-ridges. 



The author expresses his thanks to the British Association and the Royal Society 

 for grants in aid of this investigation in the summer of 1929. 



Prof. J. W. Gregory, F.R.S. — The recent Cable Fractures in the Western 

 Atlantic. 



Mr. S. H. Straw.— On the Fauna of the Palceozoic Rocks of the Little 

 Missenden Boring. 



The boring put down at Little Missenden (Bucks.) reached Palaeozoic rocks at a 

 depth of 1,200 feet, and remained in them until it was discontinued at 1,264 feet. 



The fauna of these rocks, though resembling that of the Upper Ludlow, has few 

 species identical with those of the latter formation. On the other hand, the fish 

 remains as well as certain of the invertebrate species possess undoubted Lower 

 Devonian affinities. 



Up to the present, however, it has not been found possible to make a direct cor- 

 relation with any of the known Downtonian or marine Lower Devonian faunas of 

 Western Europe. The Missenden fauna does not appear to have been recognised in 

 situ elsewhere in Europe. It may be present in certain East Prussian drift blocks 



