Page:Cyclopedia of Western Australia, volume 1.pdf/49

importance owing to the fact that it yields an overflowing supply of artesian water at the rate of 520,000 gall. per day drawn from a bed of sandstone 448 ft. in thickness, and forming the lowest bed of the Carboniferous Series penetrated. The basal beds of this formation which constitute the catchment area are well exposed in the headwaters of the Wooramel, Gascoyne, Minilya, and Lyndon River valleys. According to the latest data available there are in all twenty bores in the North-West, reaching an aggregate depth of 32,096 ft. and having a total output of 11,151,620 gal. of water per diem.

The large area of sedimentary rocks sufficiently porous to absorb and transmit water occurring in the Kimberley Division has led to some more or less successful boring operations. The Great Sandy Desert as shown on the maps of Australia is made up of sedimentary rocks disposed in such a way as to form an ideal artesian water-bearing basin. This country extends from Flora Valley to somewhere about the neighbourhood of Lake Disappointment. These sandy beds doubtless continue westward and form the low country J which flanks the Ninety-Mile Beach between La Grange Bay and Poissonier Point. The basal beds of the Carboniferous Series, which form the intake of what may be called the desert artesian area, outcrop along the northern flanks of the valley of the Fitzroy, where the rainfall is greatest. The few bores which have been put down in this perhaps the largest of the Western Australian basins prove that the occurrence of artesian water in the Kimberley Division is no longer a matter of theory.

The following is a summary of the flowing and non-flowing artesian wells in the State, so far as can be gathered from official data:

The natural history of Western Australia cannot be studied apart from that of the Australasian region as a whole. Australia, Tasmania, and New Zealand are islands now, but in far-back times had a more or less direct land connection with Asia and South America. A map of ocean depths to the 1,500-fathom line shows the position of these former connecting lands very clearly. Along these old connections came the first living creatures, which became the ancestors of the present Australasian land fauna. Geologists can tell us something regarding the period when these now sunken lands were above sea-level, for crystalline rocks occur in Fiji and clay slate in the Marquesas group; and such rocks do not appear in islands which have never formed part of a continental mass. During the Palæozoic period there was assuredly a large continent stretching from Asia across the South Pacific Ocean, but at the close of that period a big climatal change occurred over a large part of the Southern Hemisphere. All the southern half of Australia went through a severe glacial epoch, the evidences of which are still to be distinctly seen in the North-West Division of Western Australia and in the Irwin River basin of that State; on Kangaroo Island and the shores of St. Vincent Gulf, in South Australia; and at Bacchus Marsh, in Victoria. During the succeeding Mesozoic period the configuration of land and sea within the Australasian region became greatly changed. There were great dislocations and subsidences; along the coast of New South Wales it is estimated that the downthrow was at least 12,000 ft. Such a subsidence must have involved the ocean bed far out eastward, and it seems probable that New Zealand became dissevered from the continental mass about this period. Western Australia also became a large island, and Eastern Australia and Tasmania a long narrow peninsula. During the Cretaceous age the sea stretched uninterruptedly right across Australia from north to south and was of great depth, for the sediments in the Lake Eyre basin have by artesian-water bores been proved a mile in thickness. At the close of the Cretaceous epoch a great uplifting of the land began which finally established dry land from west to east, and brought Lake Eyre itself within 39 ft. of the present sea-level. With occasional oscillations this uprising is still going on along the south of the continent, but in the north there is a corresponding subsidence taking place and deepening the shallow sea which separates Australia from New Guinea. Toward the close of the Tertiary period this uprising was accompanied by intense volcanic activity along the western side of the former long peninsula, and immense flows of lava occurred over wide areas in Victoria, New South Wales, and Queensland. The old land connection with Asia was now finally broken up, and the configuration