Page:1902 Encyclopædia Britannica - Volume 25 - A-AUS.pdf/846

 790

AUSTRALIA [geology discovery of pastoral country : a new zest had been added to the able areas a "slaty” structure, a high angle of dip, and a meridional cause of exploration, and most of the smaller expeditions concerned strike. themselves with the search for gold. Amongst the more important Against these facts may be placed others showing strong reexplorations may be ranked those of Tietkins in 1889, of W. semblance between Australian and European geology. The physical Lindsay in 1891, of Wells in 1896, of Hiibbe in 1896, and of the geography and the life of the Paheozoic and Mesozoic periods are in Hon. David Carnegie in 1896-97. Lindsay’s expedition, which wonderful accord with those of other continents. The great developwas fitted out by Sir Thomas Elder, the generous patron of ment of coal in the Upper Palieozoic conforms to the northern conAustralian exploration, entered West Australia about the 26th ditions. The general types that characterize Cretaceous rocks are parallel south lat., on the line of route taken by Forrest in 1874. also present, plesiosaurs and chambered shells, such as ammonites, From this point the explorer worked in a south-westerly direction being as characteristic of the Australian Cretaceous as they are of to Queen Victoria Springs, where he struck the track of Giles’s the European. The forms of life, too, that occur in the Triassic expedition of 1875. From the Springs the expedition went north- of Europe, and even North America, find their counterpart here. west and made a useful examination of the country lying between In the shales round Sydney, which are admittedly of Triassic age, 119° and 115° meridians and between 26° and 28° south lat. the remains of a giant labyrinthodon have been unearthed, and, Wells’s expedition started from a base about 122° 20' east and 25° associated with it, fishes and plants quite in keeping with forms 54' south, aud worked northward to the Joanna Springs, situated familiar in the European Triassic. on the tropic of Capricorn and near the 124th meridian. From the In using such terms as (1 Permian ” or “ Eocene ” there is reason springs the journey was continued along the same meridian to the to suppose that these periods in Australia might not have been Fitzroy river. The country passed through was mostly of a for- quite synchronous with the European equivalents. Indeed it is bidding character, except where the Kimberley district was entered, not desirable to correlate too minutely Australian and European and the expedition suffered even more than the usual hardships. The stratified rocks. We may even go further and say that it is imestablishment of the gold-fields, with their large population, caused probable that any single life zone was laid down exactly at the great interest to be taken in the discovery of practicable stock same time that a similar life zone was being built up in northern routes, especially from South Australia in the east, and from Kim- Euiope.. One particular horizon in the Silurian is characterized berley district in the north. Alive to the importance of the trade, by the interesting chain coral (halysites). No one would contend the South Australian Government despatched Hiibbe from Ood- that the chain coral “reefs” in Australia and in Europe were exactly nadatta to Coolgardie. He successfully accomplished his journey, contemporaneous. But the relative position of the halysites zone in but had to report that there was no practicable route for cattle the geological column is the same in Europe and in Australia, and between the two districts. the physical conditions that surround the growing coral are preciselyJ One of the most successful expeditions which traversed West similar. Australia was that led and equipped by the Hon. David Carnegie, reference is made under the heading Fauna to the presence which started in July 1896, and travelled north-easterly until it of Some . living fossils in Australia. Certain characteristic types, long reached Alexander Spring ; then turning northward, it traversed extinct in the northern hemisphere, still linger in the Australasian the country between Wells’s track of 1896 and the South Austra- area. The Trigonia and the Heterodontus, the Marsupials, Myrmelian border. The expedition encountered very many hardships, cobius, Ceratodus, and certain conifers and cycads are examples. but successfully reached Hall Creek in the Kimberley district. One genus of cycad (Zamia) is exceedingly common over all the After a few months’ rest it started on the return journey, following mountain and coastal regions of eastern Australia. It is a near Sturt Creek until its termination in Gregory’s Salt Sea, and then ally of one of the most characteristic forms of the fossil flora of the keeping parallel with the South Australian border as far as Lake Oolitic and Lias. In the well-known "dirt bed ” of the Portland MacDonald. Rounding that lake the expedition moved south- quarries, Dorsetshire, the stems of these cycads are to be found in west and reached the settled districts in August 1897. The great abundance. distance travelled was 5000 miles, and the actual time employed The last feature of general import is the distribution of metawas eight months. This expedition put an end to the hope, so morphosed rocks. The lower series of the Palaeozoic show a certain long entertained, that it was possible to obtain a direct and of metamorphism in conjunction with their highly inclined practicable route for stock between Kimberley and Coolgardie amount The Mesozoic rocks are much less altered from their gold-fields ; and it also proved that, with the possible exception of position. plane of deposition, and any metamorphism notable is of small isolated patches, the desert traversed contained no auriferous aoriginal limited and entirely local character. Certain sandstone beds of country. Cretaceous age have been much altered by the deposition of secondary silica. No great alteration approaching to metamorphism is known Geology. to have taken place amongst Tertiary rocks. Schistose structure is All the great formations familiar in the northern hemisphere are represented in the geology of Australia, which is in no way confined altogether to the lower Palaeozoic. exceptional, either in the character of the rocks or in the zones Principal Australian Sedimentary Formations, with some of life that characterize them. The oldest rocks are of preCHARACTERISTIC FOSSILS. Cambrian age, but little of their life-history is known. If differC Human bones and implements ; reences, rather than resemblances, be dwelt on, there are many points J mains of plants and animals of living _ ^ I Recent concerning Australian geology in strong contrast to much that j species ; Dinornis, Aptornis, OrnithoEuropean geologists have been accustomed to. As has already been frhynchus. said, there are no volcanoes on the continent, and all over the vast {Diprotodon, Macropus, Thylacoleo, Thylacinus, Nothosaurus, Megalania, interior there is a general absence of igneous rocks other than Eh ^Pleistocene. Dromomis, Echidna, Meiolania, granites. Basalt is almost unknown except on an outside belt of o Palorchestes, Dromseus, Mytilus, the country roughly parallel to the coast. There are no solfataras, oN Siphonalia. r Phascolomys, Procoptodon, Maelumeroles, or geysers, and very few hot springs. There is no such O A >5 O I ropus, Thylacinus, Thylacoleo, Dithing as perpetual snow, even on the highest mountain, no glaciers ! protodon. fPL or glacier lakes, and not a single mountain range with an Alpine O< j Spondylostrobus, WilMnsonia, Penstructure. There is a notable absence of magnesian limestones, teune, and other fossil fruits, in old « V “ leads.” and phosphate-bearing rocks are unknown. There is an equivalent 3 f Nassa, Marginella, Ancilla, CancelM of the red sandstones, but no salt beds and no gypsum. There is HP3 Miocene •j laria, Natica, Leispyraga, Nucula, evidence of glacial action in Permo-Carboniferous times, during ( Trigonia, Chione, Meroe, Tellina. which period a great ice-sheet extended over a considerable {Flabellum, Placotrochus, TerebratuV EHW lina, Cuculaea, Corbula, Nassa, Voluta, portion of Australia, and evidences of recent glaciation at Mount ^Eocene . Marginella, Aturia, Murex (upwards Kosciusko are most pronounced. In the matter of folding we 30 sp.), Triton, Mitra, Fusus, Natica, find the ^Australian, Cambrian, Silurian, and Devonian all Cerithium. giving evidence of earth movements. The Silurian rocks in f Ichthyosaurus, Plesiosaurus, Amparticular have been so folded and so intensely compressed that I monites, Belemnites, Cidaris, AvicCretaceous we usually find them over wide areas, vertical or highly inclined J ula, Trigonia, Baculites, Otodus, I Cimliosaurus, Mactra, Inoceramus, and almost invariably with a meridional strike. All over the - A l Maccoyella. 2 H continent other formations laid down subsequent to those ( Taxites, Tseniopteris, Thinnfeldia, named are spread out in vast sheets, never showing a high angle OH O° -H f Jurassic 1 Podozamites, Sphenopteris, Lepto(lepis, Coccolepis, Aphnelepis. or dip, and nowhere resting at any great height above sea- pq w f Tseniopteris, Sagenopteris, Cycadlevel. ihe Carboniferous rocks are also folded, but to a lesser &A opteris, Alethopteris, Macrotenidegree than the Devonian, and of course in a degree not to be opteris, Sphenopteris, Pecopteris, Jeanpaulia, Podozamites, Equisetum, compared with the Silurian. The intense folding of the Silurian Ottelia, Schizoneura, taken together with the lithological character of its sediments’ Triassic or Trias-Jura Oleandridium, Gingko, Zamites, Thinnfeldia, Phylseparates it at once from every other “ formation ” in the Australian lotheca, Platyceps, Unionella, Esgeological column. So marked is this that throughout Australia theria, Tremanotus, Palseoniscus, Myriolepis, Mastodonsaurus, Unio, rocks may be safely classed as Silurian if they show over consider^Pristisomus, Cleithrolepis.