president's address — SECTION c. 57 



Geological Survey. Henderson has shown that the Silurian I'ocks 

 are everywhere bounded by great faults, and in some instances 

 have been dragged down into fault-breccias which traverse the 

 Aorere (Ordovician ?) rocks. There is here, also, no means of 

 ascertaining the conformity or otherwise of Silunan upon older 

 rocks, or the relation of the Silurian to th© plutonic rocks. 



A great series oif epidotised basic lavas and agglomerates asso- 

 ciated with a conglomei-ate lying unconfoonably upon the Aorere 

 rocks, and containing pebbles of the same, form the Haupiri series 

 of north-west Nelson. Marshall suggests it is of Silurian age, but 

 the correlation with the later Te Anau series is here tentatively 

 adopted. 



Jjatt Paheozoic ( ?) and Mcsozoic ( 1) Plutonic Iiifriisions. 

 There is much uncertainty concerning the age to be assigned 

 to the granites and associated dyke rocks occurring abundantly 

 in Neleon and Westland. The presence of numerous pebbles of 

 porphyry in the Triassic conglomerates near Nelson has been urged 

 by Marshall (1912) in support of a late Palseozcic age for these 

 intrusive rocks. Hutton (1899), holding them to be contem- 

 poraneous with the "syenite" of Mackay's Bluff near Nelson, 

 which he believed to invade the "Maitai" rocks, considered them 

 to be approximately Permian in age. Henderson (1917) and 

 Speight (1910) are inclined to refer some at least of these intrusive 

 masses to the period of late Mesozoic orogeny. These rocks have 

 produced marked contact-metamorphism described by Marshall 

 (1909) and Morgan (1908). 



The Permian ( ?) " Maitai " and Tiias.-Jtira. " Holonui " Si/atem. 



The determination of the rocks that should be comprised within 

 this system, and their relationship to one another^ has long been 

 a debated point in New Zealand geology. Hochstetter (1864) ap- 

 plied the name "red and green Maitai slates," to a series of rocks 

 in which no fossils had been seen, occurring between Nelson and 

 the peridctite of Dun Mountain and consisting of steeply dipping 

 and shattered argillites and greywacke in which doubtful traces 

 of fucoid markings were noted. These were associated with lime- 

 stone, basic volcanic rocks, and the fossiliferous Triassic Richmond 

 sandstones. Hochstetter grouped all these together as of Mesozoic 

 age. The name Maitai slates soon received a greatly extended 

 application, and comprised the unfossiliferous argillites, jaspil- 

 lites. and greywackes, which formed the main ranges throughout 

 New Zealand. Hector separated out from these a great group 

 of basic agglomerates, &c., which he termed the Te Anau Series, 

 and recognised at many places, and considered to be of Upper De- 

 vonian age, and to underlie conformably the "Maitai" rocks. 

 Mackay discovered in the latter* a few brachiopods considered by 



* At the Wairoa Gorgfe, near Nelson. 



