91 



I have no doubt that the claypans and salt-lakes in the country 

 described in this section originated in this way, but I have not 

 the slightest intention of pronouncing all the salt-lakes as being of 

 terrestrial origin. 



By far the greatest number of them, and especially those met 

 on the granitic high plateaux in Western Australia, are un- 

 doubtedly of oceanic origin. 



Travertine Limestone. — The crust limestone was found in this 

 region as well as in parts of the country already traversed. It 

 was found invariably as a kind of a substratum of the sand 

 deposits, and was always, if outcropping, an indication of the 

 vicinity of sedimentary rocks. In the more arid parts of the 

 great desert, that is to say, north of Queen Victoria Spring, the 

 travertine was found compact, showing however, on breaking it a 

 globular structure. In the country south of this spring the 

 limestone nodules are found lying about loose, sometimes in big 

 heaps, They vary in size from a pea to a lien's egg, are 

 frequently perfectly spherical, and contain very often a nucleus 

 of the underlying bed rocks. These nodules are the result of 

 the disintegration of tlie compact travertine mentioned above. 



Gravel Plains. — Gravel plains are herealxjut of moderate 

 extent only. The gravel consists of the derivative material of 

 the chief component of the Mesozoic formation, namely, ferru- 

 ginous sandstone. The abundance of drift-sand would not permit 

 of anything like a widespread plain. 



II.— MESOZOIC. 



Tlie formation which has been pronounced as Mesozoic consists 

 in the following descending order, as observed on the outcropping 

 terraces, of — 



(1) Clay (indurated). 



(2) Jasper rock. 

 (•3) Conglomerate. 



(4) Quartzite (desert quartzite). 



(5) Sandstone. 



The SnnchtonGH and Quartzites are the main feature of the 

 formation. They have been already referred to as escarpment- 

 forming wherever they have been found. Lithologically they are 

 in great variety, though they are generally close-grained and 

 contain occasionally minute laminte of mica. They are very 

 tough before decomposition sets in, on account of the felspathic 

 cement they contain, but when found somewhat advanced in 

 decomposition the cement is more argillaceous. 



Jasper and Porcellanised Sandstones are the next prominent 

 feature in this formation. The gravel and gravel-conglomerate 



