Glacial Beds of Cambrian Age in Australia. 203 
greatest width across the strata between Port Augusta, at the 
head of Spencer's Gulf, in an easterly direction to the Barrier 
Ranges of iS^ew South Wales, is about 250 miles. The beds occur 
as part of a great conformable series, in the upper part of which 
Cambrian fossils have been found. The rocks above the Glacial 
Beds are mainly purple slates and limestones ; below they are 
quartzites, clay-slates, and phyllites, passing into basal grits and 
conglomerates, resting on a pre-Cambrian complex. The beds 
consist of a groundmass of unstratilied indurated mudstone, more 
or less gritty, carrying angular, subangular, and rounded boulders, 
up to 11 feet in diameter. In most sections there are more or less 
regularly-stratified bands. The thickness of the glacial series has 
been proved up to 1500 feet. The commonest rock-type among 
the boulders is a close-grained quartzite; bat gneiss, porphyry, 
granite, schistose quartz, basic rocks, graphic granite, mica-schist, 
and siliceous limestone occur. The discovery of ice-scratched 
boulders has placed the origin of the beds, according to the author, 
beyond doubt. The striae are often as distinct and fresh-looking as 
those occurring in a Pleistocene boulder-clay. Up to the present, 
eighty definitely-glaciated boulders have been secured, besides the 
known occurrence of other erratics too large for removal. Under 
strong pressure and movement in their bed, some of the boulders 
exhibit evidences of abrasion ; but this produces features which 
cannot well be confounded with those due to glaciation. The 
pressure that has induced cleavage has caused the elongated 
boulders to revolve partly in their bed and place their long 
axes parallel to the cleavage-planes. In this movement, some of 
the stones have become slightly distorted, and many show the 
effect of fracture in the form of pseudo-striation on exposed 
surfaces. The lines, however, are of equal size and depth, and 
parallel to each other over wide surfaces ; while the glacial striae 
are generally patchy in their occurrence, of varying intensity, 
and divergent in direction. A series of illustrative sections are 
described. It is considered that Mr. H. P. Woodward's suggestion, 
that the 'boulder-clay' had its origin from 'floating ice/ appears to 
be most in accordance with facts. The interbedded slates and lime- 
stones may possibly indicate the occurrence of interglacial conditions, 
2. 'Ona Formation known as " Glacial Beds of Cambrian Age " 
in South Australia.' By H. Basedow and J. D. Iliffe. 
Some 8 miles south of Adelaide a typical exposure of the con- 
glomerate is bounded to the east by a series of alternating quartzitic 
and argillaceous bands of rock, comprising the central and western 
portions of a fan-fold, partly cut off by a fault. Further evidence of 
stress in this margin is given in the fissility, pseudo-ripple-marks, 
contortion and fracture, and obliteration of bedding in the quartzite- 
bands, and in the pinching-out of them into lenticles and false 
pebbles. On the west side the conglomerate is bounded by the 
' Tapley's Hill Clay-Slates,' and there is evidence from the nature 
of the junction-beds that the conglomerate itself is isoclinally folded. 
