SALIENT POINTS IN THE GEOLOGY OF QUEENSLAND. 205 



however, turned up till the opening of the Croydon Goldfield, 

 when the Desei't Sandstone resting on auriferous reefs in granite 

 and quartzite country, were found to be charged with marine 

 fossils. 



In spite of the undeniable and highly important break repre- 

 sented by the unconformability of the Desert Sandstone on the 

 Rolling Downs beds, Mr. R. Etheridge, jun., informs me that 

 his study of the Croydon fossils leaves him unable to separate 

 the Rolling Downs from the Desert Sandstone in the sense that 

 the one has an older fauna than the other. This is the second 

 time that groups of strata separated by an unconformability have 

 actually been found to contain the same assemblage of fossils. 

 The other instance, it may be remembered, was the case of the 

 Dotswood and Star beds. 



The unconformability between the Rolling Downs formation 

 and the Desert Sandstone, both of which are Cretaceous, renders 

 it at least easy to believe that in spite of the similarity of the 

 organic remains the former represents the Lower Cretaceous, 

 during which period, according to Professor Hutton, Eastern 

 and Western Australia formed two islands, while a continental 

 land extended from New Guinea to South America, with a 

 peninsula extending from Fiji to New Zealand. But between 

 the Lower and Upper Cretaceous Periods (if we call the Desert 

 Sandstone Upper Cretaceous — andit is olderthan Tertiary ) insular 

 land surfaces existed all over the area lately occupied by the 

 Lower Cretaceous sea. A second depression took place when the 

 Desei't Sandstone was deposited, and this depression was even 

 greater than the former. In other words, the Upper Cretaceous 

 sea of Australia was of greater extent than the Lower Cretaceous. 



Exceedingly like the Desert Sandstone lithologically, and with 

 an assemblage of fossils which Mr. Etheridge assures me are not 

 generally separable from its fauna, are the Maryborough beds, but 

 their position on the eastern side of the coast range — the island 

 of Lower, and again of Upper Ci'etaceous times — differs widely 

 from that of the Desert Sandstone. The latter abuts at 

 high levels against the palpeozoic range, while the Maiy- 

 borough beds merely occupy the flat which fringes the coast! 

 No trace of the Rolling Downs (Lower Cretaceous) formation 

 is found underlying the Maryborough beds, which rest on the 

 Burruin Coal-field. I can only suppose that the sea-bottom on 

 the eastern side of the range was much deeper than that on the 

 western, and that the deposition of the Upper Cretaceous (?) 

 sediments did not continue long enough to heap the latter up to 

 the level of the coeval deposits in the shallower mediterranean to 

 the west. I infer, also, from the way in which all tlie formations 

 from Carbonifero-Permian times onward abut against the range, 

 the gi'eat antiquity of the escapement on the eastern side of the 

 Cordillera — and by consequence the great antiquity of the Pacific 

 Ocean. 



