What may be the value of this “Desert Sandstone” for free gold, is at present unsolved; but the very nature of its deposition seems to preclude the idea that that metal will be found in paying quantities, except where direct local abrasion of a rich auriferous veinstone has furnished the supply.
MESOZOIC.
Cretaceous.—As early as 1866 a suite of fossils was collected by Messrs. Sutherland and Carson, of Marathon station, Flinders River, and forwarded for determination to Professor McCoy, in Melbourne. They were never figured, but his manuscript names are as follows:—
| Reptilia. | |
| Ichthyosaurus Australis. | “M’Coy.” |
| Plesiosaurus Sutherlandi. | |
| Plesiosaurus macrospondylus. | “M’Coy.” |
| Cephalopoda. | |
| Ammonites Sutherlandi. | “M’Coy.” |
| Ammonites Flindersi. | “M’Coy.” |
| Belemnitella diptycha. | “M’Coy.” |
| Ancyloceras Flindersi. | |
| Lamellibranchiata. | |
| Inoceramus Carsoni. | “M’Coy.” |
| Inoceramus Sutherlandi. | “M’Coy” (identical with the English species I. Cuvieri). |
In company with Mr. Sutherland, who supplied McCoy with the before-mentioned materials, Mr. R. Daintree visited the Upper Flinders, and carefully collected the fossils from three localities, viz., Marathon station, Hughenden station, and Hughenden cattle station.
At Marathon, which is some forty miles further down the Flinders than Hughenden, there is, close to the homestead, an outcrop of fine-grained yellow sandstone, which has been quarried for building purposes, and below this, to the edge of the waterhole supplying the house, is a series of sandstones and argillaceous limestones, containing numerous organic remains. These were submitted to Mr. Etheridge for examination and correlation, the result of which appears in the appendix to his work. The Hughenden cattle station is twenty miles further up the Flinders than the Hughenden head station. Here hundreds of Belemnites are strewn over the surface of the two ridges which front the cattle station huts, but they are rarely found in the soft shales which crop out from under an escarpment of “Desert Sandstone.” The lithological character of these cretaceous strata is such that decomposition is rapid; the resulting physical aspect being that of vast plains, which form the principal feature of Queensland scenery west of the Main Dividing Range; but that the “Desert Sandstone” has extended over all this country is evidenced by its existence either in the form of outliers, or as a marked feature “in situ” in all main watersheds, or by its pebbles of quartz and conglomerate, which are strewn everywhere over the surface of the plains. The height of the watershed between the Thomson and Flinders Rivers is locally not more than 1,400 feet above sea level, and as the former river has to travel as many miles before reaching the sea, it is easy to understand why, in a country subject to heavy tropical rains at one period of the year, followed by a long dry season, the river channels are ill-defined, and vast tracts of country covered by alluvial deposits. Down the Thomson and its tributaries, these mesozoic rocks are known to extend, though much obscured by flood drifts. That this portion of the mesozoic system extends throughout the whole of Western Queensland to Western Australia is also more than probable, hidden, however, over large areas by “Desert Sandstone.”
Mineral Springs.—There is one other subject of practical interest connected with the great mesozoic western plains, and that is the occurrence of hot alkaline springs, which suggest the possibility of obtaining supplies of water on the artesian principle over some portion at least of this area.
At Gibson’s cattle station, Taldora, on the Saxby River, a tributary of the Flinders, a spring of hot water rises above the surface of the plain, and its overflow deposits a white encrustation, which on analysis by Dr. Flight, under the direction of Professor Maskelyne, afforded:—
| Water | 27.793 |
| Silica | 0.600 |
| Chlorine | 3.369 |
| Sodium | 2.183 |
| Carbonic Acid | 33.735 |
| Soda | 31.690 |
| 99.370 |