68 HORN EXPEDITION — GENERAL GEOLOGY. 



localities in Victoria, the age of which is considered by McCoy to be Miocene ; 

 but it has, however, been shown that the Victorian occurrences are below 

 marine Eocene, and this accords well with the general fact that wherever the base 

 of the marine Eocene is reached, lacustrine and plant-bearing beds succeed 

 in depth. Beds of this age in New Zealand have been called Cretaceo- 

 Eocene by Hector. 



The Vegetable Creek and Dalton beds do not come in contact or in near 

 location to Cretaceous ; and the marine Tertiaries are absent in New South Wales, 

 as well as in the country occupied by the Desert Sandstone. 



We have, thus, a late Cretaceous deposit and an infra-Eocene one, containing 

 the same type of vegetation, several species being actually common to the two, 

 which, if not coeval, must be coterminous ; it was because of such considerations 

 that one of us* had suggested the probability of a paheontological overlap 

 between Cretaceous and Eocene in Australia. 



The fact that the Desert Sandstone of Queensland has not yeielded this type of 

 vegetation is no argument against the contemporaneity of the phytifei-ous beds of 

 Lakes Eyre, Torrens, etc. The same type of vegetation is common to the Laramie- 

 Cretaceous of North America and the Palreogene of Europe ; and the question of 

 age of the Australian equivalents may be answered in much the same way as was 

 done in respect of their contemporaries in the northern hemisphere. The Desert 

 Sandstone of Central Australia by its attachment to the Upper Cretaceous, and 

 by the occurrence of marine Mollusca of Cretaceous age (at Lake Frome well- 

 sinkings) must be i^egarded as coeval with the Desert Sandstone of Queensland, 

 which, by its intercalated marine sediments is proved to be Cretaceous ; though 

 separated unconformably from the Rolling Downs series (Upper Cretaceous). The 

 phytiferous beds, which underlie marine Eocene in Victoria and South Australia 

 and are conformable with them, may conveniently be considered Pre-Eocene. 



VII. — Post-Cretaceous Phenomena. 



Age of Secondary Silicification. — That the siliciticatioii of the Desert Sandstone 

 was long subsequent to the period of deposition of the original matrix is evident 

 from the following facts : — 



L The uppermost stratum is a breccia, impregnated and cemented by hydrated 

 silica. Every exhibition of this condition is suggestive of crushing or shattering 

 of the rock in situ, without any actual displacement of the fragments. 



* Presidential Address, Aust. Assoc. Adv. Science, 1893, p. 35. 



