Park. — On the Jurassic Age of the Maitai Series. 435 



The Trias formation consists of a great series of clay- 

 stones, coarse and fine sandstones, and granitic conglomerates, 

 containing a number of well-marked fossiliferous horizons, 

 to which reference will be made later when describing tlie 

 section in Eighty-eight Valley. 



A careful examination of the pebbles and boulders forming 

 the conglomerates shows that they consist principally of 

 diontes, granite, and a great variety of acidic, eruptive, and 

 quartzose material, all of which have been apparently derived 

 from the granitic masses in the Mount Arthur district, lying 

 to the north-west of this, where these rocks occur in situ, 

 associated with rocks of Silurian age. 



It is a significant fact, and one quite in harmony with 

 the stratigraphical evidence, that the ultra-basic eruptive 

 rocks which occupy so conspicuous a place in the Maitai 

 formation are quite absent from the Trias conglomerates. 



The Maitai formation and its colossal pile of basic erup- 

 tives form a long chain of broken uplands, on the lower 

 flanks of which the Wairoa beds form a corresponding chain 

 of foot-hills. Hence, if the Maitai rocks were antecedent 

 with the Wairoas resting on their denuded surfaces, as con- 

 tended by Sir James Hector and Mr. McKay, fragments of 

 the basic eruptives should be largely represented among the 

 coarser sediments of the Wairoa beds ; but they are entirely 

 absent, as, indeed, could not be otherwise from tbeir sub- 

 sequent date. 



The Maitai rocks have generally been described as slates 

 of various colours. This is a somewhat loose use of the 

 term " slate." The rocks are not really slates, but bluish-grey 

 claystones, which often occur in thin laminae of different 

 shades of colour. When these thin laminae alternate with 

 each other, as is often the case, the rock gets a slaty or 

 flaggy appearance. In places the claystones are slaty and 

 somewhat fissile, with a silky lustre where they have been 

 much crushed. In the lower part of the formation there 

 are thick beds of grey sandstone and greywacke, generally 

 much shattered and jointed, and often streaked with white 

 veins of a hydrated mineral which was determined by the 

 late Mr. W. Skey to be stilbite. Thin veins of grey and 

 brown flinty quartz occur in the harder sandstones in several 

 places. 



Beds of red and green slaty claystones and breccias occur 

 interbedded in the formation. They are quite subordinate in 

 extent to the claystones and sandstones, but wherever they 

 occur they are very prominent from their conspicuous colour. 



Mr. McKay, referring to the Wairoa section, says, " In the 

 lower part of the Eoding Eiver, near its junction with the 

 Wairoa, the junction between these beds is strictly analagous 



