PRESIDENTIAL ADDRESS. 23 



section, Pig. 5, after Howchin, shows the probable struc- 

 ture of this senkungsfeld. 



Fig 5. Sketch Section, (suggested by works of Walrer Howchin) 

 Across the Rift Valley of South Australia 



Vertical Scale 10.000 feet to an inch. M-Loftygocr 



fbrt Lincoln S PENCERS GULF Yorkefeninsula STV ^ NT 



TERTIARY, PERMO-CARBONIFEROUS 

 AND CAMBRIAN ROCKS IN TROUGH FAULT 



We may now glance briefly at the trend lines of Northern 

 Territory, as far as they are known. The Rev. J. E. 

 Tenison- Woods 1 figures a highly folded series of crystalline 

 rocks without giving the trends of the folds. Mr. H. Y. L. 

 Brown 2 in several reports has, with his assistants, placed 

 us in possession of our present information as to the 

 dominant structure lines of that region. The following 

 conclusions may be provisionally drawn from Mr. Brown's 

 reports : — 



(1) That the Pre-Oambrian schists and gneisses have 

 been folded on lines whose directions vary from N. and S. 

 to N.N.W. and S.S.E. 



(2) That the lower Cambrian Salterella limestones and 

 associated strata strike about N.W. and S.E. with lines of 

 major faulting and zones of crushing trending in the same 

 direction. 



(3) That the Ordovician quartzites have been somewhat 

 folded and strongly tilted, the chief direction of the tilt 

 being towards a little W. of S. This tilting appears to be 

 connected with the great tectonic lines which extend 

 through New Guinea in an E. by S. and W. by N. direction. 



(4) That the Permo-Oarboniferous rocks have not been 

 folded. 



1 Keport on the Geology and Mineralogy of Northern Territory. By 

 authority, Adelaide, 1886. 



2 Northern Territory Exploration, 1895. Northern Territory of S.A., 

 Eeport by H. Y. L. Brown. By authority Adelaide, 1905. 



