197 



ment of Miocene, 149 feet of argillaceous and calcareous strata 

 containing a typical Eocene moUuscan fauna, and an infra-Eocene 

 series of more or less carbonaceous beds 142 feet thick. 



Professor David and Mr. Howchin"^ have sought to explain 

 the stratigraphical relationships of these two dissimilar series of 

 beds by the introduction of a north and south fault, ranging 

 along the buried scarped front of the Archaean rocks, on which 

 the Eocene and Miocene of the Adelaide plateau repose. This 

 conjecture disregards the probability that physical conditions of 

 varying character may have been the contributing cause of the 

 lithological and organical disparities. 



If the position of the Eocene in the Croydon-bore be due to a 

 downthrow fault, then it might be reasonably expected that the 

 very distinctive Eocene series of the Kent Town-bore would be 

 repeated in the Croydon-bore ; but as such is not the case, I am 

 of opinion that there is no direct evidence of a fault, and that 

 the Kent Tow^n series belong to a later period, and are more 

 littoral in their organic contents. 



The series of events that these sections teach us may be sum- 

 marised as follows : — The Post-Cretaceous sea laved the base of 

 the now subterranean escarpment of over 2,000 feet in vertical 

 height, and at that measure the land stood relatively higher. 

 Deposition and depression were synchronous over the submerged 

 plain ; coincident therewith, wholly or in part, lacustrine and 

 paludinal accumulations, preserved in the carboncceous beds of 

 the Kent Town-bore, were formed on the higher ground. Finally 

 depression submerged the terrestrial surfaces at Kent Town, and 

 a more littoral life prevailed there in comparison with the earlier 

 Eocene deposits. The Miocene deposition followed, succeeded by 

 the extensive denudation of the Miocene and higher levels of the 

 Eocene, and the removal of about 800 feet of the Eocene series, 

 constituting the Adelaide Plain. Over this plain of marine 

 denudation, Pliocene marine beds were accumulated, these of a 

 more or less shallow-water origin, and over an area of depression; 

 finally to be converted into a vast lacustrine area, in which land- 

 drifts of about 400 feet have been accumulated. 



II. TiNTiNARA Bore. 



Eocene-sands at a depth of 244-253 have yielded on the 

 examination of further material the following list of species, 

 which indicate a correlation to the lower series of the Aldingian 

 beds, those in common marked with an asterisk. 



*Marginella sub-Wentworthi 



^Drillia, sp. 



♦P.L.S., N.S. Wales, xxi., tab. xl., fig. 1. 



