270 



taken place in recent times. Tliis deposit extends for soni(> 

 distance through Sections 44 and 46, and evidently belongs 

 to an older series than the raised beaches already described. 

 In the raised beaches of Yorke Peninsula we have repre- 

 sented, therefore, two distinct geological horizons, correspond- 

 ing exactly with the upper amd lower series described by Mr. 

 W. Howchin in connection with the raised beaches' of Port 

 Adelaide with which they may be correlated. 



The height of Peesey Swamp above sea level, as shown by^ 

 the aneroid, ,proved to be 25 ft., and the heights of all the 

 other raised beaches being taken, it was found that they all 

 lay between 25 ft. and 40 ft., the greater number having an 

 elevation of about 25 ft. 



Professor Tate, in the paper already referred to, suggests two 

 possible origins of the raised beach extending across the Penin- 

 sula from Sturt Bay to Hardwicke Bay, now known as Peesey 

 Swamp — 1. A general elevation of the land. 2. Tbe blockings 

 up of the mouths of a shallow strait by blown sand. Now, 

 as pointed out, there is a series of raised beaches occurring 

 at short intervals round the southern and south-western coast 

 of Yorke Peninsula, all having about the same elevation 

 above sea level. This, taken in »con junction with the fact 

 that the characteristic shells of nearly all these are the same, 

 would seem to suggest that the whole area was simultaneously 

 subject to a general upheaval in recent times converting all 

 the shallow bays and straits into raised beaches and swamps, 

 and leads to the conclusion that Peesey Swamp has probably 

 been produced by elevation. 



The chain of salt lagoons lying between Marion and Ponda- 

 lowie Bays, unlike those in the neighborhood of Yorketown, 

 is evidently of marine origin, and, like Peesey Swamp, is pro- 

 bablv the remains of a shallow strait which stretched rigfht 

 across the Peninsula. The silt forming the floor of these 

 lagoons directly overlies calciferous sandstone, which no doubt 

 was denuded away by tidal action, which must have been at 

 times very considerable. 



Professor Tate has suggested that the beds of natural whit- 

 ing which occur in this neighborhood have been produced by 

 "the exfoliation of incoherent shell banks.'' That this is the 

 case is shown by the fact that the silt also consists largely of 

 natural whiting, which has evidently been derived from the dis^ 

 integrating shell banks which form the most characteristic 

 feature of these lag-oons. 



