108 



(Mote Descriptive of a Stereogram of the: 

 Mount Lofty Ranges, south Australia. 



By W. N. Benson, B.Sc. 

 [Read August 10, 1911.] 

 Plates XX. and XXI. 



In a previous paper a short outline was given of the 

 physiography of the Mount Lofty Ranges as it appeared to 

 the writer from observations made during 1908. W 



Recently a stereogram has been constructed for the 

 Sydney University to illustrate the features on which his con- 

 clusions were based. A brief description of this model may 

 not be out of place here. The information on which it was 

 modelled was obtained from the official map of south-eastern 

 South Australia and the topographic map of the vicinity of 

 Adelaide. Trigonometrically-determined heights are sadly 

 few in number. The general relief of the area between Noar- 

 lunga, Angaston, and Murray Bridge, and in the Inman 

 Valley is based on the writer's own sketches and aneroid 

 readings. A topographic map of Mount Barker district 

 published in the daily Press during the military manoeuvres 

 of 1908 was also of service. The modelling of the area about 

 Mount Compass is based on Mr. Howchin's map and descrip- 

 tions (2) and additional information kindly supplied by him. 



Owing to the writer's non-acquaintance with areas out- 

 side these limits the model may be subject to some modifica- 

 tion in those parts, and indeed owing to the smallness of 

 scale no more than a very rough accuracy has been attempted 

 throughout. 



The small inset model illustrates the main tectonic 

 features. As these are being investigated in detail by Mr. 

 Howchin a very brief description will here suffice. 



The main portion of the Mount Lofty Ranges, stretch- 

 ing from beyond Angaston to Cape Jervis and extending 

 into Kangaroo Island, is a peneplain. The main drainage, 

 before uplift, was in mature valleys running in an approxi- 

 mately meridional direction. < 3 ) On the peneplain surface 

 were residuals of a higher level, monadnocks, such as Mounts 



(i) Trans. Roy. Soc, S.A., 1909, p. 107. 



(2) Trans. Roy. Soc, S.A., 1910, pp. 231-47 and pis. xxxi. to 

 xlv. 



(3)W. Howchin, Geography of South Australia, p. 124. 



