AUSTRALIAN GLACIATIONS 201 
much as the old glacial topography and surface features have 
been largely preserved, to the present day, throughout hundreds 
of square miles of country. This remarkable preservation of very 
ancient land forms has followed from a series of fortunate circum- 
stances: first, because the original relief became protected by 
vast accumulations of transported material; and, second, because 
throughout most of the Cainozoic periods the glaciated area was 
below sea level and thereby became further protected by marine 
deposits. No important lateral movements occurred during the 
intervals to disturb the horizontality of the beds. An elevation 
took place in late Cainozoic times, with the result that the marine 
deposits have all but disappeared from exposed situations; and 
now, with the further erosion of the underlying morainic material, 
the old-world hills and valleys, that had been carved into outline 
by an ice-sheet in late Paleozoic times, are slowly being unbur- 
dened and once more make the surface features. The conditions 
that prevailed over this area during Mesozoic times are doubtful. 
No rocks of the latter age are known to exist in the southern 
portions of South Australia, but the preservation of the glacial 
beds, dating from pre-Mesozoic times, would seem to indicate 
that during those periods the beds must have been either at, or 
below, base level. 
It is possible to gather a rough idea of the land features as they 
existed in southern Australia during this ice period. It is clear, 
both from the direction of the striae and the dispersal of the erratics, 
that the ice-sheet came from the south. At that time the main 
axis of elevation was to the south of the present continent, with 
upland valleys that opened out toward the north. Remnants of 
such uplands are preserved in the great granitic zone, the northern 
margin of which is seen in the prominent headlands and coasted 
islands. These southern highlands probably disappeared, in the 
main, when by a great Senkungsfeld along the southern limits of 
the continent, in early Cainozoic times, the land became submerged 
and admitted the sea over a wide belt of country. That this old 
watershed of the south had become greatly reduced—probably to 
an elevated plateau—at the period of glaciation, is suggested by 
the preponderating number of granitic rocks among the erratics. 
