78 Transactions. 



Outline of the Geology. 



The Maitai rocks of Wellington Peninsula are a series of argillites and 

 greywackes with a general strike N. 12° E., and having an average dip 

 of 70°, the direction of dip varying from east to west. The rocks to be 

 described under the heading of " Eed Eocks " are members of this series. 



In the Makara Valley, four miles west of Port Nicholson, is a small 

 patch of marine conglomerate which is considered by A. McKay (5) to be 

 of Miocene age. From the physiographic evidence it appears that the 

 deposit cannot be younger than Pliocene. The conglomerate is 150 ft. 

 above sea-level, and rests on a fault-zone. Its total areal distribution 

 does not exceed 10 acres, and the deposit has no parallel elsewhere in the 

 peninsula. If, as stated by C. A. Cotton (4, p. 246), the "Wellington block 

 was uniformly uplifted to a height of 800-1,000 ft., this conglomerate owes 

 its position, and probably its preservation, to down-faulting since that time. 



The gravel veneers, relics of former base levels, as described by C. A. 

 Cotton (4, p. 250), are found at varying heights. Save where complications 

 have arisen through faulting, the highest gravels are the oldest. 



The Maitai Series. 

 Stratigra'phy. 



These rocks are recognized throughout the length of New Zealand. 

 The complex foldings they have undergone and their general scarcity of 

 fossils, except at a few widely separated localities, have caused much con- 

 fusion as to their age and correlation. 



The various classifications proposed by A. McKay for the rocks about 

 Wellington were seemingly based not on evidence from the stratigraphy 

 of the Wellington development of the series so much as from their sup- 

 posed relations in other places. In the first scheme proposed (6, p. 132) 

 the rocks were divided into — 



Trias and Permian . . {a.) Sandstones and slaty shales. Magazine 



Point. 

 Carboniferous . . (a.) Red and green slates, Sinclair Head. 



,, . . (&.) Sandstones and earthy slates. 



Devonian . . . . (a.) Sandstones and drossy slates, with 



numerous veinlets of quartz. 

 The Devonian rocks are spoken of by Dr. Hector as Lower Carboniferous 

 (7, p. 30) ; and this age, he says, is assigned them on account of lithological 

 resemblances to the rocks of the Rimutaka Range. These latter, he con- 

 siders, resemble rocks underlying the fossiliferous limestone at the base 

 of the Maitai slate near Nelson (7, pp. 28, 29). 



Omitting the red and green slates, the rocks mentioned in this classifi- 

 cation do not differ beyond the changes induced by weathering and faulting. 

 In fact, the description of Devonian rocks receives significance when con- 

 sidered as applied to a fault-zone ; and a study of the "Devonian" out- 

 crops mentioned — parts of the south coast, Tinakori Valley, and Makara 

 Valley — make it clear that the chief fault-zones of the district were mistaken 

 for an older series of rocks. Thus, in his Progress Report for 1878-79, 

 Dr. Hector says, " Before leaving these rocks [the ' Devonian ' rocks of 

 A. McKay] it may be as well to point out that generally when rocks of this 

 age and character occur in the South Island traces of gold are found." 

 This is easily understood, seeing that the quartz veins of Wellington and 

 Marlborough are silicified fault-zones. 



