i8 95 . 



NOTES AND COMMENTS, 



3 6 5 



and the preliminary results of their researches form Bulletin No. i of 

 the Geological Survey of Queensland. 



Somewhat remarkable explanations have been given to account 

 for the occurrence of artesian water in Queensland. The populace 

 imagines underground rivers, or reservoirs under great pressure in the 

 bowels of the earth. The geological speculator pictures permeable 

 beds passing beneath Queensland, and rising to the surface in the 

 mountains of New Guinea. More profound philosophers have gone 

 so far afield as the Himalayas or the Andes to find a collecting- 

 ground for the Queensland water. The facts, for once, are not so 

 strange as the fictions, and may readily be gathered from the 

 accompanying diagram. On the right are seen the shales (b) of the 

 Rolling Downs Formation, Lower Cretaceous in age ; these stretch 

 away to the east till they meet the sea, or are covered by the alluvial 

 and other deposits near the coast. The lower part of the Rolling 

 Downs Formation (b i) is that which is of chief importance; it is 

 called the Blythesdale Braystone, and consists of a series of soft, gray, 

 very friable sandstones, grits and conglomerates, which absorb water 

 with avidity. The outcrop of this rock forms a belt with an average 

 width of five miles, and is estimated to present a gathering-ground for 

 water of 5,000 square miles. These beds rest unconformably against 

 a series of Triassic and Jurassic rocks, viz., the Darling Downs 

 Basalt (c) ; Slates, Sandstones, and Coal-seams (d) ; Toowoomba 

 Basalt (e) ; Murphy's Creek Sandstone (f) ; Ipswich Shales, Sand- 

 stones, and Coals (f 1). Below all come the folded Palaeozoic 

 Rocks (g). Above the Rolling Downs Formation lie patches of an 

 Upper Cretaceous Rock, the Desert Sandstone, which once extended 

 as a sheet over all the rocks just mentioned, but which is now found 

 only in isolated patches, some of which obscure the outcrop of the 

 Blythesdale Braystone. 



Geological Section, Western Queensland. — R. L. Jack. 



There are a few water-bearing beds in the higher part of the 

 Rolling Downs Formation ; but for effective supplies the bores have to 

 penetrate to the Blythesdale Braystone. This derives its water 

 mainly from the annual rainfall of twenty-seven inches over its 

 intake area. Much, also, is absorbed from numerous large streams 



