158 president's address. — section c. 



In the three great submergences of the southern portions of 

 Australia that have now been briefly reviewed, we possess geological 

 data of the greatest importance in the elucidation of events that have 

 contributed towards the building of Australia. Two of these sub- 

 mergences were regional in extent, but the third, or newest, was 

 apparently local,* and a concomitant of the earth movements which led 

 to the formation of the graben or trough now occupied by the sea of 

 Gulf St. Vincent. 



So far, our attention has been chiefly directed to the considera- 

 tion of the negative land forms in the evolution of the physiographical 

 outlines of South Australia ; we have now to study its positive features, 

 and, fortunately, here the data, although very complex, are at least 

 more copious than those on which we have had to rely in the earlier 

 part of our inquiries. The existing topographical features of the 

 country have been, in the main, sculptured during the latter half of 

 the Cainozoic era, and, for our purpose, may be classed as the 



SUB-AERIAL NEOGENE. 



Resting on the marine Miocenes, as well as upon the older rocks in 

 the Mount Lofty and other ranges, are mottled clays, sand-rock, and 

 conglomerates, of fresh-water origin, and occupying various altitudes 

 from sea-level to over 1,000 feet in height. Tate, in his Presidential 

 Address before the Adelaide Philosophical Society (Royal Society of 

 South Australia) in 1879, designated these beds, collectively, as " Upland 

 Miocene," f and in the same category included such diverse formations 

 as the Desert Sandstone of Central Australia, as well as the clays and 

 sandstones of Myponga, Yankalilla, Cape Jervis, and Inman Valley, 

 which are now known to be of Permo -carboniferous glacial origin. 

 Thus, Tate's Upland Miocene, as now diagnosed, comprehended various 

 sediments, ranging from Permo-carboniferous to Pleistocene times; 

 but, while there may be a certain superficial resemblance in the litho- 

 logical facies of the beds in question, a careful examination reveals 

 marked differences on which a more discriminating classification can 

 be made. 



Confining our attention to the beds in Tate's classification that are 

 found typically on the flanks and secondary heights of the Mount 

 Lofty and Barossa Ranges, we think that Tate's estimate of their age 

 was, on the whole, too high. These alluvial and lacustrine deposits, 

 represent, in time, no doubt a very extended period, and, while it is 

 possible that some may even go back as far as late Miocene, we think 

 that the bulk of these sub-aerial deposits ought not to be placed further 

 back than Pliocene or even Pleistocene. The evidence for this will be 

 seen in the sequel. 



• The newest of the three marine series that occur on the Glenelg River (Victoria) is 

 evidently much more recent than the beds known as Older Pliocene in South Australia, and are 

 probably of Pleistocene age. See Dennant, Aus. Asso. Ad. Sc, Vol. II, p. 448 ; also Trans. Roy. 

 Soc. S. Aus., Vol. XVII, p. 217. 



t Loc. cit., 1878-9, pp. Iviii-Lsii. See also Scoular. ibid., Vol. Ill, p. 107. 



