president's address — SECTION c. 143 



■Carboniferous and Devonian strata or the same strata contain a Devono- 

 darboniferous fauna. It is possible that this apparent admixture of 

 Devonian and Carboniferous fossils may have been brought about by 

 Post-Carboniferous orogenic movements, of which there is abundant 

 evidence in different portions of the State. 



Three field seasons spent by myself in the Pilbarra Goldfield 

 {situated in latitude 29° south) afforded an excellent opportunity for 

 examining a formation consisting of sandstones, grits, conglomerates, 

 and limestones, some of which are magnesian, together with a series 

 of lavas, ashes, and agglomerates of as yet unascertained thickness. 

 In its lithological characters, its behaviour, and general physical aspect 

 it bears a very strong resemblance to the quartzites, &c., of the King 

 Leopold Plateau, to which reference has just been made. 



This formation, which has been designated the Nullagine Series, 

 has a very wide distribution in the north-west, and the associated 

 volcanic beds occupy a large area of country in the southern portion 

 of the district. The series, which presents a plateau-like appearance, 

 certain of the harder beds standing out in bold relief, presenting mural 

 faces at different levels, plays a very important j)art in the geology of 

 the north-west, in addition to being of some economic value by reason 

 of the fact that the basal conglomerate of the series has been worked 

 for the gold it contains in two widely separated localities, viz., Nullagine 

 and Just-in-Time. 



The Nullagine beds have been followed from the Oakover River, 

 across the upper reaches of the Nullagine, Coongan, and Shaw rivers, 

 as far as the western boundary of the Pilbarra Goldfields on the Yule 

 River near Cangan Pool, from which locality they can be followed 

 without a break to the vicinity of Roebourne. The same series con- 

 stitutes the Hammersley Range, which contains Mount Bruce, the 

 highest summit in the State. The Nullagine beds are probably con- 

 tinuous as far south as the Ashburton River, where both flanks of the 

 valley are formed by extensive beds of magnesian limestone, which 

 may be continuous with those which I observed in 1905, in the recesses 

 of the Hammersley Range. 



Regarding the southern extension of the Nullagine Series it may 

 be noted that in a deep bore put down by the Government at Onslow, 

 near the mouth of the Ashburton River, volcanic rocks identical with 

 those in the type district were met with. It may thus be that these 

 strata were pierced in the lower portion of the Onslow bore. 



Undoubted Permo-Carboniferous rocks are known to occupy a 

 large area of country in the watersheds of the Gascoyne, the Minilya, 

 and the Lyndon rivers, hence the examination at present being under- 

 taken of the country lying between Onslow and L^nidon should afford 

 some valuable information as to the mutual relations of the Permo- 

 Carboniferous and the Nullagine beds. So far as observations have 

 at present been carried, there seems to be a gradually ascending geo- 

 logical series as we proceed southwards. What I am inclined to regard 

 as outliers of the Nullagine Series occur in the Murchison Goldfield, 

 near south latitude 27°. In 1904 Mr. Gibson mapped a considerable 



