PRESIDENTIAL ADDRESS. 7 



mentary to the inthrow of the parallel and adjacent 

 structure of (4) Bass Strait. The boundary of the Darling- 

 Murray Basin on the west reveals element (5), the great 

 fork of the Mount Lofty and Flinders Ranges thrust far 

 north into the great basin. The deep indents of St. Vincent 

 and Spencers Gulfs and the basins of Lakes Torrens and 

 Eyre, suggest strong tectonic disturbances extending from 

 here towards the Gulf of Carpentaria. 



The main western boundary of the Great Basin is (6) the 

 plateau of Oeutral Australia, Northern Territory and West 

 Australia, accentuated at its eastern edge by the strong 

 east and west trend lines of the MaeDonnell and Musgrave 

 Ranges, and terminating south-westwards in the Darling 

 Range peneplain, interrupted by the bold bluffs of the 

 Stirling Range. The western boundary of the Darling 

 Range is followed further west by what Mr. Gibb Maitland 

 has shown to be one of the most remarkable tectonic 

 features of Australia, a deep, long and narrow rift valley. 

 Oape Leeuwin and Cape Naturaliste lie on the west side of 

 this valley, the deep indent between Cape Naturaliste arid 

 Bunbury being due to this tectonic feature. I cannot do 

 better than here quote Mr. A. Gibb Maitland's account of 

 this feature as well as on other fault lines in West Australia: 

 " In the short time available it has been found quite im- 

 possible to wade through the forty-one bulletins and fifteen 

 annual reports of the Geological Survey. The following 

 however, are the more important main fault lines, so far 

 as is known : — 1. The face of the Darling Range from the 

 South Coast to somewhere about Minginew (S. Lat.29 — 34°) 

 appears to be marked by a major fault, which there is some 

 reason for believing marks the eastern wall of a long "rift 

 valley," of which probably part of the western wall is to 

 be found in that narrow ridge of ancient crystalline rocks 

 from Flinders to Geographe Bay. The fundamental rocks 



