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IV.—On the Occurrence and Interpretation of Rock-Cliffs and Rock-Floors on the Western Shores of the “Dry” Lakes in South-Central Western Australia

Published online by Cambridge University Press:  01 May 2009

J. T. Jutson
J. T. Jutson
Affiliation:
Geological Survey of Western Australia, Perth.
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Extract

In South-Central Western Australia, in the physiographic division which the writer has termed the Central or Salt Lake Division, in a large portion of which the average annual rainfall is about 10 inches per annum, numerous “dry” lakes or playas occur. These have been described and the question of their origin has been discussed by various authors. They have been differently regarded as due to glacial, marine, and wind action; also as the remains of old Tertiary rivers now largely obliterated by drifting sands; and also (in part) as deformation basins. Most writers agree that they have been formed under subaerial conditions, and probably most will ultimately agree that deformation is responsible for some at least of the lakes, or has aided in their formation.

Type
Original Articles
Information
Geological Magazine , Volume 5 , Issue 7 , July 1918 , pp. 305 - 313
Copyright
Copyright © Cambridge University Press 1918

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References

page 305 note 1 “An Outline of the Physiographical Geology (Physiography) of Western Australia”: Bull. 61, Geol. Surv. W. Australia, Perth, 1914, p. 52.

page 306 note 1 Salts are precipitated on the lake floors on the evaporation of the transient thin sheets of water, but so far as the writer is aware there is no thickness of salt on any of the lakes. The terms “salt lakes” and “salt lake division” are therefore misnomers. “Dry lakes” or “playas” more suitably indicate the character of the lakes, but as the latter are frequently connected with one another by defined or ill-defined channels, and as many undoubtedly lie along the main drainage lines of the country, the writer has suggested the term “stream-lake system” for this dual capacity of portions of the drainage system. The terms “salt lakes” and “dry lakes” have become so firmly rooted in local usage that they will probably remain. It is difficult to suggest a suitable name for the physiographic division instead of “salt lake division”. “Dry lake or central division” would perhaps be the least objectionable of any.

page 306 note 2 As to various theories, seeGregory, J. W.,“The Lake System of Westralia,” Geog. Journ., 06,1914, pp. 656–64,CrossRefGoogle Scholar map. See alsoGibson, G., Bull. 37,Geol. Surv. W. Austral.,1909, p.12Google Scholar, and Bull, . 42, Geol. Surv. W. Austral., 1912, pp. 11, 12Google Scholar; Jutson, J. T., op. cit., pp. 138–58Google Scholar, and also Geog. Journ., 12, 1917, pp.M 418–37Google Scholar, map, figures; Montgomery, A., Journ. Roy. Soc. W. Austral., vol. ii, pp. 59–96, map, 1915–1916;Google ScholarGregory, J. W., Geog. Journ., 10, 1916, pp. 326–31;CrossRefGoogle Scholar and Honman, C. S., Bull. 71, Geol. Surv. W. Austral., 1917, p. 144,Google Scholar and Bull. 73, Geol. Surv. W. Austral., 1917, p. 17.Google Scholar

page 306 note 3 Geol. Mag.,08, 1897, pp.363–6.Google Scholar

page 308 note 1 Bull. 56, Geol. Surv. W. Austral., 1914, pls. i, ii, fig. 1, pp. 10–12, 34.Google Scholar

page 309 note 1 Op. cit., p. 11, fig. 1.

page 309 note 2 Bull. 66, Geol. Surv. W. Austral., 1916, pl. i, pp. 11, 36.Google Scholar

page 309 note 3 Bull. 73, Geol. Surv. W. Austral., 1917, pp. 17–19.Google Scholar

page 309 note 4 It might here be noted that Honman accepts J. W. Gregory's theory on the lakes as a whole as dismembered river systems. See Bull. 71, 1917, p. 144, and Bull. 71, 1917, p. 17, Geol. Surv. W. Australia. He also notes (Bull. 71, p. 15) that Lakes Carey, Raeside, and Rebecca cross the strike of the rocks, and suggests that these lakes may belong to a different cycle of erosion uninfluenced by geological structure. On the ancient river theory, it could be contended in explanation of this feature that the old streams were superposed. The question cannot be discussed here. It will be dealt with elsewhere.

page 309 note 5 Bull. 71, Geol. Surv. W. Austral., 1917, pp. 23, 24.Google Scholar

page 309 note 6 Bull. 59, Geol. Surv. W. Austral., 1914, p. 195.Google Scholar

page 311 note 1 Bull. 21, Geol. Surv. W. Austral., 1906, p. 21, and plate.Google Scholar

page 311 note 2 Bull. 45, Geol. Surv. W. Austral., 1912, pls. i, ii.Google Scholar

page 311 note 3 Well to the east of Norseman the sea in probably Miocene times was much farther north, but this formerly sea-covered land is outside the area discussed in this paper.

page 312 note 1 It is not contended that larger lakes never existed. They have possibly done so, but there is no available evidence that they formed deep permanent lakes. What evidence there is points, in some instances, to wider areas of shallow ephemeral lakes or playas practically similar to those now in existence, and to the probability that such greater lakes have, owing to local conditions, shrunk. In other instances the migration of a lake may account for an apparently greater former lake of the playa type.

page 313 note 1 Op. cit., p. 365.

page 313 note 2 Bull. 66, Geol. Surv. W. Austral., 1916, p. 36.Google Scholar

page 313 note 3 Principles of Stratigraphy,New York, 1913, p.603Google Scholar.

page 313 note 4 Dust is no doubt also caught by the lake waters when they are in existence, and this is then deposited as an aqueous sediment.