Broadgate.— 27;r ''lied Eocks'' and Associated Beds. 79 



In the argiUites of the Maitai Series of Wellington Peninsula are found 

 a few obscure animal-remains of small size not yet identified and some 

 indistinct plant-remains. The only fossil so far determined is the annelid 

 Torlessta Lckayi Bather ; this fossil has as yet no definite stratigraphic 



value. , 



Petrography. 



Microscopic study of the greywacke shows the presence of quartz, feld- 

 spar, hornblende, augite, biotite, muscovite, and epidote. 



The quartz which makes up most of the recognizable material is always 

 angular, with no appearance of secondary growth. Many of the pieces 

 show undulose extinction. Feldspars are both orthoclase and plagioclase. 

 The orthoclase is always considerably altered The plagioclase feldspars 

 identified range from albite to medium labradonte. Hornblende and 

 auaite are in very small amount. The biotite, muscovite, and epidote are 

 probablv secondary in some cases. Needles of rutile are sometimes seen 

 in the quartz, and rods of apatite in the hornblende. The greywacke 

 cement is siliceous ; much of the groundmass is of indeterminable brown 



"^""The^ material of the argiUites is too fine to reveal much under the micro- 

 scope. Feldspar and quartz are recognizable under high power. Small 

 veinlets are generally present, these being probably of secondary silica 

 The common argillite is dark-coloured ; prolonged heating leaves a dull 

 red-coloured product. The dark colouring-matter of the rock is most 

 likely carbonaceous material (9, p. 44). 



Conditions of Deposition. 



The criteria for recognition of estuarine deposits as given by Hatch 

 and Rastall (10, p. 13) apply well to the rocks of Wellington Peninsula. 

 The rapid alternation of different types of sediments, often m thin layers, 

 is very marked. The greywackes vary in texture from fine conglomerates 

 to fine-grained sandstones, though the change is not gradual m any one 

 band • layers of different degrees of fineness are separated by bands of 

 argillite, the argillite itself being probably only an extreme case of a fine- 

 grained greywacke. . , •. j- .lt, i 



The presence of feldspar and the persistent angularity of even the large 

 quartz grains both point to deposition not far from the source of supply. 

 The facies is, indeed, that common to deposition m shallow water of the 

 waste resulting from denudation of an igneous mass— the greywacke oemg 

 a quartz product from the siliceous content, and the argillite representing 

 the product of decay of the more aluminous constituents. 



A peculiar type of greywacke is that from Makara Valley (Plate VI, 

 fig 1 and Plate VII fig 1). Besides the ordinary constituents, this has 

 numerous pieces of argillite up to half an inch in length. These argillite 

 inclusions have an irregular outline, and appear to be invaded by the 

 quartz as though thev were still unhardened at the time of inclusion. 

 This type has been nJted in Westland (11, p. 45 ; 12, p. 85). Such a rock 

 could originate only in shallow water. 



Faults. 

 The chief fault-zones are indicated on the map. Most likely this repre- 

 sents only a proportion of the total number, but it probably includes the 

 more important lines of dislocation. 



