Canterbury and Westland. 283 



of the "Waiau river, described in my Report on the Geology of 

 the Amuri district (Eeports of Geological Explorations during 1870-71, 

 Geological Survey of New Zealand) form the northern continuation of 

 this zone. On the West Coast, only basic rocks appear to have been 

 erupted, by which, south of Bruce Bay, a considerable portion of the 

 coast line is now formed. I have already stated that they appear to 

 be of a somewhat younger age than the eruptive rocks on the eastern 

 side, because if the sedimentary beds, consisting of conglomerate, grits, 

 shale, and coal, with which the melaphyres are associated, and which 

 are doubtless of the same age as the Grey Coal Measures, are 

 contemporaneous with the cretaceo-tertiary formation on the eastern 

 side, which is very probable, they ought to be classed with the basic 

 rocks, making their appearance during that period. However, my 

 reason for placing them with the former is, that they possess all the 

 characteristics of true melaphyres, having, moreover, extensive beds of" 

 tufas and amygdaloids associated with them. 



Chaeactee and Sequence op the Eeuptive Rocks. — Melaphyee... 



Seeies. 



Although there are characteristic tufa beds interstratified with the 

 melaphyres, no fossils of any kind have been found in them at present, 

 and thus it is impossible to state when those eruptions, which were on 

 a gigantic scale, took place, by which the melaphyres and their 

 accompanying tufas were deposited upon the sea bottom. I can only 

 repeat what I previously stated concerning them, namely, that they 

 repose on the sedimentary strata, which, previously to the eruption of 

 these basic rocks, had undergone great changes and denudations, and 

 that since then no alteration of importance, except the rising of the 

 land, has taken place. After these basic rocks were deposited, before 

 the next, or acidic beds were formed, they, in their turn, underwent 

 enormous denudations. I may here add, that generally in other 

 countries the acidic formations (quartziferous or felsitic porphyries) 

 constitute the lowest beds, whilst the melaphyres, or basic rocks, 

 repose upon them — our beds thus differing in this respect. Of this 

 denudation the isolated system of the Gawler Downs forms a notable 

 instance, as it is only a remnant of a once continuous series of beds, 

 which all around have been removed, often for many miles. 



