Page:Cyclopedia of Western Australia, volume 1.pdf/38
consist of pure crystalline quartzites, indurated grits, and quartzose conglomerates, interbedded with purple slates and soft sandstones. Much detailed fieldwork is, however, required before the occurrence of undoubted Silurian rocks can be considered to have been definitely proved in Western Australia.
Devonian.—The occurrence of Devonian rocks has as yet been definitely proved only in one district of the State—the Kimberley Division, where this formation appears to be largely developed. The beds consist of hard grits, conglomerates, indurated limestones, and shales, associated with which are contemporaneous lava flows, breccias, and ashes. In the Napier Range the Devonian rocks are represented by solid crystalline limestones, with at the base of the formation a calcareous breccia and conglomerate. These beds are seen in the Barker River Gorge to pass beneath a series of sandstones and shales of what are believed to be Carboniferous age.
Junction of Metamorphic and Devonian rocks, Elvire River
Among the fossils found in the Napier Range beds are a Coccostean fish, a new species of Proetus; remains of Loxonema, sp.; Euomphalus, sp.; Rhynchonella, allied to R. Timorensis; Pachypora, sp.; Phillipsastrœa, sp.; and Goniatites, sp., which clearly indicate a Devonian age for the strata.
The following fossils have also been found occurring in the Kimberley Devonian rocks:—
- Anthozoa. Cyathophyllum vergatum, Hinde; Phillipsastrœa, sp.; Favosites Goldfussi, Edw. and Haime.
- Brachiopoda. Productus, sp.; Atrypa reticularis, Linn.; Rhynchonella cuboides, Sow.; R. pugnus, Martin; R. cf. Timorensis, Beyr; Spirifera Musakheylensis, var. Australis, Foord.
- Gastropoda. Goniatites (Brancoceras), cf. rotatorius, De Kon.
- Crustacea. Proetus, sp. nov.
Permo-Carboniferous.—The Permo-Carboniferous rocks cover a wide extent of country and bid fair to become of considerable economic importance. There are four regions in which fossiliferous Permo-Carboniferous rocks are known in the State, viz., Kimberley, Gascoyne, Irwin River, and Collie districts.
The beds as exposed in the Kimberley district are divisible into a lower or limestone series (in which limestones predominate) and an upper or sandstone series (made up largely of sandstones and other sedimentary beds). The two series are seen to succeed each other conformably in the Haughton Range. Both series have yielded a rich assemblage of fossils. The Kimberley Carboniferous beds underlie nearly the whole of the so-called Great Sandy Desert, which extends from the Ninety-Mile Beach westward to the Northern Territory frontier.
The Gascoyne beds cover a very large area between the 22nd and 26th parallels of southern latitude, and excellent sections of them may be seen in the valleys of the Wooramel, Gascoyne, Lyons, Minilya, and Lyndon Rivers. Like their representatives in Kimberley, the strata are divisible into an upper or sandstone and a lower or limestone series. The sandstone series, which is seen resting conformably upon the limestone, is well exposed in the Corandibby, Kennedy, and Moogooloo Ranges. These Permo-Carboniferous rocks have been pierced in the pioneer borehole at Pelican Hill, near Carnarvon, which had been carried down to a depth of 3,011 ft. These strata, which comprised calcareous shales and limestone, were encountered beneath the fossiliferous mesozoic rocks at a depth of 1,406 ft.; and continued to the bottom of the borehole, which, however, was not carried deep enough to reach the floor of more ancient rocks upon which they rest.
Interbedded with these Permo-Carboniferous rocks