181 



the facts on the uncertain chance of the resumption of boring 

 operations. 



The main stratigraphical features, summarised from the boring 

 account (kindly furnished by the Conservator for Water, and 

 herewith appended), are introduced in the accompanying section, 

 Plate IV., which represents in the fullest manner the strati- 

 graphical relationships of the various formations of the Tertiary 

 Period in South Australia ; the eastern part of the section has 

 already been published. Trans. Roy. Soc, S. Aust., vol. V., pi. 1, 

 p. 40, 1882, and is here added for the sake of completeness. The 

 section shows that the Old Tertiaries (Eocene and Miocene), 

 underlying the City of Adelaide, crown a steep escarpment of 

 Archaean rocks, against which have been deposited in succession 

 the marine beds of the Older Pliocene and the Mammaliferous 

 Drift ; whilst at Port Adelaide, recent marine deposits margined 

 by sand-dunes, resting unconformably on the Mammaliferous 

 Drift, mark a post-tertiary shore-line ; and finally modern sand- 

 dunes line the present shore. 



The Section affords clear evidence of a time-interval between 

 the Miocene and Older Pliocene ; and induces me to remark that 

 a closer study of "erosive surfaces" among our Tertiary beds will 

 prove of high value in determining their relative ages and check 

 the conclusions drawn from palteontologic;.! data alone. The 

 remarkable diversity of sedimental conditions and concurrent 

 faunal changes within the same geologic basin may lead us to 

 incorrect conclusions if we do not admit that palaeontology is 

 based wholly on stratigraphy. 



The superposition of the dissimilar Miocene-fauna on tlie 

 Eocene is in most localities unaccompanied by any visible strati- 

 graphical break ; feebly so, however, at Muddy Creek, but in 

 this case the palaeontological conclusions led up to the recogni- 

 tion of an interruption in the succession of deposits. However, 

 the stratigraphical break is most pronounced in the maritime 

 tract in mid-southern Gippsland, where the Miocene-beds are 

 laterally in juxtaposition with Eocene-strata, which rise to much 

 greater altitudes— a relationship analogous with that of the 

 Newer and Older Tertiaries at Adelaide as exhibited in the 

 present Section. 



Thus all the grander groups. Eocene, Miocene, Older Pliocene, 

 and Pleistocene, are separable on stratigraphical data ; and when 

 these are obscured or not determinable, then our knowledge of 

 the fauna of each, when sufficiently varied and well-developed, 

 will enable us to identify geological horizons within the same 

 geological basin or probably in contiguous ones. 



