152 president's address. — section c. 



have penetrated the older marine series, inchiding the head of the 

 Great Bight, Kent Town, Croydon, Noarlunga, and the Murray Plains. 

 A good section of the beds is exposed in the sea clifis, a little north of 

 Port Willunga (Aldinga). No fossils, other than obscure carbonaceous 

 remains, have been observed in the beds, but they have hitherto received 

 but scant attention. Their wide-spread occurrence, and the frequent 

 presence of carbonaceous muds in the series, are suggestive of a country 

 of low relief, probably reduced in great measure to base level, a country 

 of sluggish streams and swampy flats, that was finally submerged by 

 the inroads of the Eocene sea. 



First Marine Series. — The Eocene sea, which transgressed this 

 low-lying country, encroached much beyond the present limits of the 

 ■continent, and formed a new continental shelf. The littoral and 

 shallow- water deposits of this old shore line were of no great thickness, 

 and have long since been, for the most part, removed by denudation, 

 while only the thicker deposits have resisted the hand of time. It is 

 therefore difficult to draw the line that would show the full extent of 

 this submergence, but we can certainly include within the area the 

 southern parts of Western Australia, carrying the line in a northerly 

 <lirection not less than 150 miles inland from the head of the Great 

 Australian Bight, across Eyre's Peninsula, and from thence eastwards — 

 for there were at that time no Spencer's Gulf, or Gulf St. Vincent, or 

 Mount Lofty Ranges — it was all open sea. There is no doubt that, 

 ■originally, the lower Cainozoic marine deposits formed a continuous 

 sheet covering the present maritime districts from Western Australia 

 to the eastern side of Victoria. The sites of Perth, Adelaide, and 

 Melbourne were at that period covered with deep water, and a bay of 

 the Eocene sea extended inland along the present course of the Rivei 

 Murray as far as the south-western portions of New South Wales. 



These conclusions are based on the occurrence of numerous outliers 

 of this rock, scattered over the districts just mentioned. The great 

 €rustal changes that transpired in late Cainozoic times broke up the 

 continuity of these marine deposits, and, by elevating some of the 

 fragments into a zone of rapid waste, led to their complete removal 

 from large areas especially in the uplands. On the other hand the 

 •development of a graben, in the area of the present Gulf St. Vincent, 

 helped to preserve these old Cainozoic deposits from subaerial waste, 

 and supplies the maximum record of their thicloiess within the limits 

 ■of South Australia, 



We have reason to think that no complete section of the loAver 

 Cainozoic marine beds have come down to the present day. The lower 

 marine series is commonly covered with a second marine series of more 

 recent date, with a plane of unconformity and erosion between the two. 

 We have no means of estimating the time value of this interval of erosion, 

 ■or to what extent the lower series has been reduced therebv, but the 



