The South Attitralian K^aturalist. 75 



MALLEE GEOLOGY. 



The Mallee countr}^ comprises a large and important area of 

 three States : Victoria, New South Wales, and South Australia. 

 The development of portions of this area for wheat-growing 

 has added a new province to Victoria and one to South Aus- 

 tralia ; north of the river a lower rainfall prevails, and the 

 country has not been similarly developed. A good introduc- 

 tion to the underlying geological structure may be gained on a 

 trip up the Murray River. About the mouth of the river we 

 find vast accumulations of sands and muds of recent age, car- 

 ried down by flood waters and there deposited. As we go up 

 the river we find the valley narrow and limited by limestone 

 cliffs, which abound in marine fossils, pointing back to the 

 times when a great inland sea — the ''Murray Gulf" — extended 

 over the area. At and below Murray Bridge we have a 

 glimpse of the underlying bedrock, which is here of granite. 

 Over the greater part of the area the ancient bedrock is found 

 at depths of from one to two thousand feet, but in the southern 

 portion it occasionally projects on the present surface. 



Above Murray Bridge, and onward as far as Overland 

 Corner, the river is bounded on either side by high limestone 

 clijPs, whose varied forms and aspects, with their glorious 

 browns and yellows, await the brush and canvas of another 

 Hilder. These cliffs contain abundant oyster-shell beds, whales' 

 teeth, sharks' teeth, and shells in numberless variety. Beyond 

 Overland Corner the cliffs consist of river-borne sands, gravels, 

 and muds, and the colouring is even more beautiful and the 

 forms more varied. From Mildura to Swan Hill and onward, 

 the river has more the appearance of a canal, with low banks, 

 allowing a view of the wide enclosing plains from the 

 steamer's deck. Apart from the geological aspect of the sur- 

 face, the chief point of interest lies in the water-bearing beds, 

 in places artesian, which lie at depths varying mainly between 

 150 and 700 feet. Another feature, that is at present occupy- 

 ing the attention of the irrigationists of Mildura, is the ques- 

 tion of the possibility of utilising some of the underlying 

 porous beds as reservoirs into w^hich settlers might drain their 

 surplus surface waters when necessary. 



In 1916 there was published a record of an important 

 series of bores put down by the Victorian Government in the 

 Mallee, under the direction of Mr. A. S. Kenyon, C.E. This 

 record was a monument of diligent and painstaking investiga- 

 tion of the bore materials, carried on during eight years by 

 Mr. Frederick Chapman, of the Melbourne National Museum. 



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