CLIMATES OF GEOLOGIC TIME. 291 



Hatch and Corstorphine state: 



" Fossils are practically unknown, but Griesbach found some small bivalves and a finely striated 

 Patella, both too indistinct for determination, in certain shales, which he considered interbedded 

 in the series at Kranz Kop, near Greytown. Anderson, who visited the locality, during the 

 period covered by his first report, was unsuccessful in his search for additional organic remains" 

 (1909: 77-8). 



From an earlier paper by Rogers and Schwarz the following is gleaned : 



"Not only is the rock similar to some varieties of the Dwyka conglomerate in general litho- 

 logical character, and in being what we may call a conglomeratic mudstone, but glaciated pebbles 

 occur in it. * * * The pebbles scattered at intervals through the conglomeratic mudstone are 

 of all sizes up to 5 inches in length. They consist of quartz, quartzite, grits, slaty rocks, granite, 

 and felsite. The small, whitish, often nearly spherical quartz pebbles found in this rock are 

 also very characteristic of the sandstone above and below, in which they occur isolated and in 

 thin beds of conglomerate. We picked out nine pebbles from IJ/^ to 4 inches in length, which 

 have the characteristic form of glaciated stones, that is, they are flattened on one or more sides, 

 and the flat faces show scratches, often arranged in parallel groups, but the other parts of the 

 surface are also sometimes striated. * * * This evidence, then, irresistibly forces us to the 

 conclusion that in South Africa during the time of the deposition of the Table Mountain sand- 

 stone — that is, in about lower Devonian times — glacial conditions existed somewhere in this 

 neighbourhood. We had no opportunity of examining the shale-band north of this, but to the 

 south, ice-scratched boulders do not occur in it, so that presumably the boulders came from the 

 north, just as the Dwyka boulders did" (1901: 78-9). 



LATEST PROTEROZOIC GLACIATION. 



Australia. — Below the great tillite zone there are over 11,000 feet (in 1912 Howchin states 40,000 

 to 50,000, including the Cambric) of conglomerates, grits, thick feldspathic quartzites, slates and 

 phyllites, and thin and thick zones of hmestone resting upon an ancient complex of highly de- 

 formed and altered rocks. On these strata rests the great zone of tillite, attaining thicknesses 

 ranging from 592 to about 1,500 feet. Throughout this mass of material no recognizable fossils 

 are as yet known and therefore its age cannot be determined other than that it is older than the 

 overlying Lower Cambric strata. 



Upon these older coarse strata rests "conformably" the Lower Cambric series, the lithological 

 features of which " are in strong contrast " to the older series above described. The basal Cambric 

 beds are known as the Tapley's Hill slates, with a thickness of over 2,000 feet. These pass upward 

 into calcareous slates and finally into "a very pure hmestone, oohtic in structure, bluish in its 

 lower portions and reddish in the upper," known as the Brighton limestone. It is here that the 

 Lower Cambric Archsocyathinse make their appearance. Still higher appear purple slates, then 

 quartzites and purple limestones, together some hundreds of feet thick. It is at the top of this 

 series that comes in the great Archseocyathus coral reef and other Cambric fossils, now more or 

 less transformed into marble beds fully 200 feet thick. The two fossihferous horizons are separ- 

 ated from one another by about 1,000 feet of strata. All of the Cambric and lower strata are 

 now deformed into mountain ranges. 



Howchin says further: 



"The beds which give evidence of glacial origin may be described as consisting mainly of 

 a groundmass of unstratified, indurated mudstone, more or less gritty, and carrying angular, 

 subangular, and rounded boulders (up to 11 feet in diameter), which are distributed confusedly 

 through the mass. It is, in every respect, a characteristic till. The included stones sometunes 

 occur in pockets or groups, but the rock never becomes a typical conglomerate. Coarse angular 

 grits and quartzites often occur in the form of irregular deposits, mixed with the finer ground- 

 mass, and these may or may not carry boulders. * * * 



" In most sections there are more or less regularly-stratified beds or bands, which occur at various 

 horizons in the till. These may be of quartzite, finely-laminated slate, or limestone. The last- 

 named seldom exceed 2 or 3 feet in thickness, are often gritty, and contain angular stones. * * * 



"The occurrence of isolated and irregularly-distributed boulders is a constant feature m the 

 exposures of the gritty mudstone, or till; but these stones vary in size, relative numbers, and to 

 some extent in their petrological types, in different localities. A close-grained and very siliceous 

 quartzite usually supplies the commonest variety. * * * 



"Although the general features of the beds supplied a strong -prima-facie probability that 

 they represented an ancient till, their glacial origin was not affirmed until the discovery of ice- 



