264 Transactions. 



General Geology. 



It is beyond the scope of this paper to deal with the general geology 

 of the district, and a brief sketch will suffice to establish the geological 

 relations of the rocks described. 



The oldest rocks exposed are argillites and greywackes. classed by 

 McKay* in the Maitai series of Carboniferous age, which are equivalent to 

 the Greenland formation described by Morganf in the Blackball district and 

 in Westland. These sediments have been intruded by the immense mass 

 of granite that has such an important development along the western flanks 

 of the Southern Alps in Nelson and Westland. 



The coal-measures and succeeding Tertiary beds were deposited upon a 

 more or less irregular erosion surface of the argillites and greywackes and 

 upon the granite which had been laid bare by denudation. Since the de- 

 position of these Tertiary beds, major uplift, various oscillatory movements 

 of uplift and depression, prolonged denudation, and profound and complex 

 fault-fracturing have all contributed towards the present configuration of 

 the district. 



At some period following the deposition of the basal beds of the coal- 

 measures lamprophyres were injected in dykes that transect both the granite 

 and the basal breccias of the bituminous-coal series. The upward limit 

 of these dykes has not yet been determined with certainty, but they have 

 not as yet been found to pass above the horizon of the basal coal breccias. 



It has not been ascertained to what extent the intrusion of the granite 

 has metamorphosed the older sediments ; the prevailing feature of the 

 contact alteration immediately adjacent to the granite is the development 



aornfels, but widespread gneisses outcrop in some parts of the district, 

 and these probably owe their structure to the pressure and other circum- 

 stances attendant on the granitic intrusion. 



Petrography. 



The rocks to which attention has been directed in this paper are — ■ 

 (1) biotite-hornblende granite; (2) granitic gneiss with abundant epidote ; 

 (3) syenite-porphyry ; (4) diorite ; (5) lamprophyres ; (6) dolerite. 



Besides the above, many other more widely distributed types occur, 

 but, as these are in most cases not of special interest, they have not been 

 described. 



Literature. 



So far as the writer is aware, the only petrographical papers dealing 

 with the igneous rocks of the Westport district are the following : — 



1889 : Hutton, F. W. — " Description of some Eruptive Rocks from the 



Neighbourhood of Westport, New Zealand," Trans. Geol. Soc. of 



Australia, vol. 1, 1889 (?), pp. 106-10. 

 1889 : Hutton, F. W.— " The Eruptive Rocks of New Zealand," Trans. 



Roy. Soc. N.S.W., vol. 23, 1889, pp. 102-56. 

 1889 : Hutton, F. W.— " Note on the Geology of the Country about 



Lyell," Trans. N.Z. Inst., vol. 22, 1889, pp. 387-90. 

 1906: Sollas, W. J., and McKay, A.—" The Rocks of Cape Colville 



Peninsula," vol. 2, p. 159. (Sollas describes a section cut from the 



gneissoid granite of Cape Foulwind.) 



* "Papers and Reports relating to Minerals and Mining," Parliamentary paper 

 C.-13, p. 27, 1895. 



t Bull. No. 13 (n.s.), N.Z. Geol. Surv., and Bull. No. 6 (n.s.), N.Z. Geol. Surv. 



