56 president's address — section c. 



are geneirally most strongly metaiiiorphic in the' western portions, 

 and consist of morei cr less schistose rocks, sometimes giieissic, 

 associated with the dioritic rocks described above, and passing 

 eastwards into' amphibolite, epidote-schist, mica-schist, phyllites, 

 argillites, arkoses and greywacke. The metamorphism has 

 been studied mostly by Morgan, who recognises that it 

 is for the most part reigional in character, but is especially 

 marked about the bosses of massive granite. As before stated, 

 seme geologists, especially Morgan and Henderscn, consider that 

 there are twO' groups of intrusions, the older gneisses which are 

 considered to antedate the Aorere rocks, and the younger granites 

 and associated dykes which luay be later Palaeozoic or even 

 Mesozoic. It is evident that the detailed study of this region by 

 the methods of modern metamorphic ])etrology will be essential 

 tO' its elucidation. 



T],c Silnrian For/,s. 



The Silurian rocks of the Eaton River in Nelrtn Province have 

 net been investigated during the past decade. Their mode of 

 occurrence is .obscure, and little weight can be placed at present 

 oil the suggested conformity of these rocks with the Ordovician 

 series, though they are both steeply dipping rocks with a north- 

 westerly strike. Hector provisionally determined over fift}^ species 

 of fossils, which Thomson (1913) enumerates. They are largely 

 brachiopods suggesting a comparison with We-nlock faunas. The 

 rocks are argillaceous limestones and clay-ahales. The fossiliferous 

 recks of Reefton cover less than four square miles, and consist of 

 quartzite with some ca.rbo.naceous streaks, greywacke, argillite, 

 and limestone in rapid alteration, and a small amount of tuffa- 

 ceous material. The limestone is coralline or crinoidal, and these 

 with the clastic sediments contain an eixtensive molluscan fauna 

 in which Hector tentatively determined thirteen forms, and as- 

 signed a Lower Devonian age to tlie rocks. Henderson (1917) 

 accepted this, urging in support Wanner' s recognition of 

 riciirodictyum in these rocks, a genus characteristic of the Lower 

 Devonian of the Rhine. This genus, however, is represented in 

 the Silurian rocks of Victoria, and New South Wales, and in the 

 preliminai-y examination of a collection of thirty-four species of 

 fossils from Reef ten, Mr. W. S. Dun, Government Palaeontolo- 

 gist of New South Wales, determined a group of forms comparable 

 with those of the Silui-ian recks of the Yass series of New South 

 Walee, and the Yeringian of Victoria, both considered to be of 

 Wenlock age. He was of the opinion that the Reefton beds are 

 probably coeval with those of the Eaton River, though with such 

 differences as may be explained by the more littoral character 

 of the Reefton rocks. J This determination accords with the 

 views of Hutton, Park, and Marshall, and is now accepte^l by the 



X Private communication ; cited by permission of the Di.'ector of Geological Survey. 



