PROBLEM OF THE GREAT AUSTRALIAN ARTESIAN BASIN. 143 



some extension to the west of Oodnadatta; 1 maybe there 

 are one or more limited outlets leading westwards into the 

 Eucla Artesian Basin, following limited channels in the 

 older rocks, and towards which the Mound Springs near 

 Lake Phillipson point. This is, however, only just a possi- 

 bility, but against it there is the extreme contrast in 

 chemical composition shown by the two classes of waters 

 (See II. p. 269) as will be emphasized in Section V. 



On the south the basin is cut off from Spencer's Gulf by 

 a barrier of ancient rocks, and from the Murray Tertiary 

 Basin, both near Lake Frome and between Oobar and 

 Bourke by buried ridges. Pittman, while raising the point 

 whether there might not be an overflow close to Wilcannia 

 below the Cretaceous beds into the younger basin, considers 

 that the evidence in its favour is very slight (I. § 86, 1911). 



III. The Geology of the Basin. 



The recent work done by Saint-Smith (II. p. 19) in the 

 area north of Roma, in definitely proving that the actual 

 intake beds consist of the fresh-water strata underlying 

 the marine Lower Cretaceous Rolling Downs formation, 

 of which the so-called " Blythesdale Braystones" really 

 form the basal portion, at once brings the Queensland 

 succession into line with that in New South Wales, as 

 worked out by Pittman during the last twenty years. 



In view of their stratigraphical and palaeobotanical rela- 

 tionships, the use of the term Trias- Jura — a relic of ancient 

 nomenclature — is cumbersome and not altogether desirable, 

 and for these reasons the name "Jurassic Beds" is to be 

 preferred, as employed by Gregory and David, with the 

 proviso that in certain localities some actual Rhaetic or 

 even Triassic strata may be involved, as perhaps in the 

 south-eastern corner, where there may in places be a con- 

 formable passage downwards into Palaeozoic rocks. 



1 See E. Lockhart Jack, Geo]. Surv. S. Aust., Bull. 5, pt. 2, 1915. 



