154 president's address. — section c. 



they make no great spread, and are often masked by more recent 

 deposits. They have had, however, a very important effect on the 

 economic aspects of the country where they occur. Their decomposi- 

 tion, makes a rather poor soil, which is generally either sandy or a hard 

 travertine crust, produced by a chemical solution of the calcareous 

 contents in the wet season and the reprecipitation of the same in the 

 dry months, which slowly builds up a limestone at or near the surface. 

 In this process of solution and reconstruction there is always a tendency 

 to produce a certain proportion of salinity in the soil and circulating 

 waters, which in areas of defective drainage makes the soil unfruitful. 

 The vegetation covering these areas is of a very characteristic type, 

 being the natural home of the mallee, with a thick undergrowth of a 

 sub-arid flora. 



In southern York Peninsula these beds have given rise to peculiar 

 surface features. The Eocene limestones (which rest on Permo- 

 carboniferous boulder clay) have been removed from extensive areas 

 by solution, leaving many saucer-shaped depressions varying in size 

 up to 12 miles in circumference. The dissolved material has been 

 carried by rain water and precipitated in the form of travertine lime- 

 stone, gypsum, and salt. As no drainage from this country reaches 

 the sea, the soakage finds its way into these sunken areas, and, as the 

 floor is retentive, the water becomes evaporated, and the salt and 

 gypsum are deposited as a crust in the drier months, which has given 

 rise to an important industry. Similar conditions, on a smaller scale, 

 occur in Kangaroo Island.* 



As a rule, the lower Cainozoic beds preserve an almost horizontal 

 pasition, with an occasional dip (rarely exceeding 5°), and when it 

 does occur generally persists over long distances. They have, however, 

 been subjected to much faulting, and, in one instance, to be referred 

 to later, they are highly inclined and overfolded. 



MIDDLE CAINOZOIC ((?) MIOCENE). 

 Second, Marine Series. — An important break in the continuity of 

 deposits occurred in southern Australia at the close of the Eocene 

 period. That period was determined, and a new cycle inaugurated, by 

 earth movements which produced an elevation of the land and the 

 consequent retreat of the sea to latitudes further south. The only 

 data by which we can judge the length of this interval of erosion is 

 in the stratigraphical and palseontological discordance that exists 

 between the first and second series of the Cainozoic marine sediments. 



* For further particulars, see Howchin, " On the Origin of the Salt Lagoons of Southern 

 Yorko Peninsula." Trans. Roy. Soc. S. Aus., Vol. XXV, p. 1. 



