president's address. — SECTION c. 155 



The difEerentiation of the two sets of beds, in both these respects, is 

 strongly marked. In places where the two series are brought into 

 juxtaposition, as in the Aldinga clifis, and the banks of the River 

 Murray at Nor'-West Bend, a slight stratigraphical unconformity can 

 be recognised, the newer series resting on the eroded edges and slightly 

 more tilted beds of the older.* At Jemmy's Point, Gippsland Lakes 

 (Victoria), the Miocene beds flank an Eocene escarpment. 



In lithological contrasts the newer series is mostly of a sandy 

 nature, often incoherent, and seldom takes the form of a limestone, f 

 as is frequently the case in the older series. The palseontological 

 contrasts are equally marked. The material available in South Australia 

 for such a comparison is limited, but Tate estimated that at Spring 

 Creek (Victoria) only 10 per cent, of the moUusca are common to both 

 series ; and at Muddy Creek, only 7 per cent. ; while the same authority J 

 estimates that, of existing species, the Eocene of southern Australia 

 carries an average of less than 2 per cent., and the Miocene about 

 10 per cent., a difference sufficiently great to demand an extended 

 interval of time to bring about the modification of the molluscan fauna 

 to this degree. 



So far as I am aware, no intermediate beds, either fresh-water or 

 marine, are known to occur in any part of the region concerned ; there is, 

 therefore, an important hiatus in the geological records at this stage; 

 but we may conclude with certainty that, between the time of the 

 retreat of the Eocene sea and its return in the second Cainozoic 

 submergence, there was a lengthy period during which the land stood 

 at a greater elevation and was undergoing waste, constituting what may 

 have been a complete geographical cycle. 



In most cases the Miocene beds rest immediately on the Eocene ; 

 but at Marino, near Brighton, and some other places, they rest on a 

 Cambrian floor ; at Hallett's Cove, on Permo-carboniferous glacial 

 beds. The Miocene beds have a more restricted distribution than those 

 of the Eocene, they do not occur at so high a level as some of the Eocene 

 fragments (seldom, if ever, exceeding 60 feet above present sea-level), 

 they are also much inferior in thickness and more terrigenous in the 

 nature of their sediments, all suggestive that the Miocene subsidence 

 was of less extent than the Eocene, of shorter duration, and laid down 

 in shallower waters. It must, however, be allowed that their absence 

 from the higher levels, where the Eocene beds are sometimes found, 

 may arise from their ha\'ing been removed by erosion. As they are 

 superior to the Eocene, they would be the first to suffer from the 

 destructive forces of sub-aerial waste, and, as relatively thin and 

 imperfectly consolidated beds, would weather rapidly. In the rare 



* Tate, " Miocea^ and its Relation to Eocene." Loc. cit., p. 119. 

 t The oaly exception I know is at the head of the Great Bight. 

 { Loc. eit., pp. 136-148. 



