PEESIDENT's address — SECTION c. 55 



which the zircons in the biotites are sunounded by very dark 

 pleochroic haloes.* There are, too, numerous xenolithsi of horn 

 blende-schist in dykes invaiding the " Maitai " rocks near Whan- 

 arei. Bartrum cites these and other considerations to show that 

 there " are vestiges of a land-area which probably antedated the 

 period of depcsiticn of Mesozoic sediments," a conclusion fore- 

 shadoivA^ed by Park in 1893. Perhaps, as Marshall suggested 

 (1909), the olivine-uorite of Ahipara (North Auckland) may be 

 one of these pre-Mesozoic intrusions, but the evidence for this is 

 inconclusive, and he lat'ET (1912) classed it as intrusive into Meso- 

 zoic rocks. It appears toi the writer: remarkably like what must 

 have been the parent rock of a more altered rock occurring in the 

 Greenstoinei Saddle, west of Lake Wakatipu. 



The Onlovicmn Ii'ocks. 



The oldest rocke of which the age is definftely known are Ordo- 

 vician, and are now generally tenned the Aorere series. Their age 

 is defined in two fossilifercus localities respectively in the so'uth- 

 west of the South Inland, Preservation Inlet, and in the north-west 

 of the South Island, West Wanganui Inlet, Collingwood. Be- 

 tween these there stretches a narrow western zone of more or less 

 metamorphosed rocks now referred in great part tO' this series. 

 In Preservation Inlet, the slates adjacent to thei granite contain 

 Clonof/rapttis, Bri/oijraptus, and Tet.ra(jraptii$, and are referred 

 by Hall (1915) to the base of the Arenig (Lancefieldian of Vic-, 

 torian Geology). In Collingwood the slates contain Bryograptus, 

 iJichograptus, Didymograptus, Goniograptus, Loganograptus, and 

 Tetragroptus, and aro of Middle Arenig (Castlemanian) age, 

 (Shakespear 1908, Hall 1915). Kecent work of the Geological 

 Survey in the latter region is tending to confirm Dr. Shakespear's 

 suggestion that two fossilifercus zones are recognisable. Some tri- 

 lobites, at present undetermined, are eaid toi have been dis- 

 covered.* The slates of this group are associated with grey- 

 wackes and quartzites, and pass gradually into mica-schist in which 

 are great masses of marble, the "complex carbonates" of Bell 

 (1907), and the Mt. Arthur or Pikikiruna series of earlier classi- 

 fications. 



Southwards from this region in the western footliills and slopes 

 of the Southern Alps, there are wide areas of metamorphic rocks 

 now considered by the Geological Survey to be of early Paljeozoic 

 age, though fcrmerlv assigned to the later Palaeozoic or even 

 Mesozoic age, and classed under various names, Arahura, Kanieri,! 

 Greenland, We?tland, or Maitai series, &c. There form a large 

 part of West Nekon and Westland Provinces, and have been 

 traced south-westwards to beyond Mt. Cock (Bell 1905). They 



* Private commimication. 



t TIi's name was employed by Bell (1906) through oversight. It had been previously given 

 to a portion of the Tertiary series. ^ ^ 



