Geological Horizon. 



The siliceous limestones of Reynella are about 2,500 ft., 

 possibly more, below the base of the Cambrian limestones con- 

 taining Archaeocyathinae at Sellick Hill, 35 miles southerly 

 from Adelaide. The siliceous limestones of Reynella and the 

 Brighton limestones, together with those of Burra (on the 

 horizon of the Brighton limestones north of Adelaide) are 

 singularly like those of the Nullagine series in Western Aus- 

 tralia, and called by the Government Geologist (Mr. A. 

 Gibb Maitland) the Carawine limestones. The thick reddish- 

 purple slate beds of the Adelaide region immediately above the 

 Brighton limestone have a close analogy in the reddish- 

 purple slates and shales of the Hamersley Range of the 

 Fortescue River area of Western Australia and the reddish- 

 purple slate series underlying the Irwin River coal measures 

 (Greta coal measures), both occurring in the Nullagine series 

 of Western Australia. 



The black shales, at least 1,500 ft. thick, which at Sellick 

 Hill underlie the Archaeocyathinae limestones, and there con- 

 tain small chalcedonic nodules, appear to correspond closely 

 with the black shales with chalcedonic nodules at the top of 

 the Nullagine series of Western Australia, as seen in the 

 hills about 16 miles northerly from Roy Hill Station, on the 

 Fortescue River. No fossils have, as yet, been found in the 

 Nullagine series, and Mr. A. Gibb Maitland classifies them now 

 as Proterozoic. 



With the exception of some doubtful radiolaria, figured 

 by Professor Howchin and myself from the horizon of 

 these siliceous limestones near Hallett Cove,(i) and a 

 problematical calcareous fossil found by Professor Howchin 

 apparently weathered out of the purple slate beds near Hallett 

 Cove, no organic remains have previously been recorded from 

 these beds in South Australia. Mr. A. Gibb Maitland, as 

 already stated, classes the Nullagine series as Proterozoic, 

 while Professor Howchin classes these equivalents (in my 

 opinion) of the Nullagine series of Western Australia as 

 Lower Cambrian. I would tentatively suggest that all the 

 strata from the base of the Archaeocyathinae limestones 

 to the basal conglomerates overlying the Archaean (?) 

 schistose rocks of Aldgate, in the Adelaide region, be 

 given some local name such as "the Adelaide series," and, 



(i)PrcM3. Linn. Soc. N.S. Wales, 1896, pt. 4. pp. 571-583, 

 y)h. xxxix.-xl. 



