PROCEEDINGS OF SECTION C. 435 
been the scene of the most violent and intense volcanic activity. 
From stratigraphical reasons I am inclined to think that this 
great series is probably of Upper Eocene age, and contemporary 
with the great volcanic outbursts which took place around 
Oamaru during the deposition of the Mount Brown or Hutchison 
quarry beds. 
2.—Lower Eocene, Auriferous Series. 
This formation, as we have seen, consists principally of fine- 
grained sandstones, generally pyritous and highly decomposed, 
alternating with subordinate bands of harder and coarser sand- 
stone, which sometimes pass imperceptibly into breccia beds. It 
is exposed in the denuded core of an anticline, both sides of which 
are overlain by the great volcanic breccia and tuff series just 
described. 
In his report on the Thames Goldfield in 1882, Mr. 8. H. Cox, 
F.G.8., late Assistant-Geologist, makes the dip of the auriferous 
series north-west along the whole line of exposure from Kurunui 
Creek to Hape Creek. (Geological Reports, 1882, pp. 10-12). 
The effect of this is to place the coarse breccias and tuffs as the 
lowest member of the auriferous series. At the Tararu end of 
the section these breccias are found overlying the auriferous 
rocks, but Mr. Cox gets rid of this difficulty by calling in the 
aid of a hypothetical fault, the throw of which, he says, would not 
be less than 2000 feet ; (/.c., A. 12), but it is evident that 5000 feet 
would be nearer the amount, as the two outcrops are separated 
by over a mile and a half. The hard sandstone and breccia band 
forming the apex of the anticline, which follows the trend of 
Waiotahi Hill (see D on Section), is shown by Mr. Cox on his 
map and section as lying on the highly denuded edges of the 
auriferous series. An important result of my survey of this 
line of section has been to place these rocks in their natural 
position. 
It is usual among most writers to speak of the reefs at the 
Thames as occurring in volcanic rocks. This, however, is not 
the case. The gold-bearing rocks are closely hemmed on both 
sides of the field by coarse volcanic breccias, tuffs and agglo- 
merates, frequently intruded and interbedded with solid dykes 
and lavas, and this has probably led to the error. The whole 
of the auriferous series is of undoubted sub-aqueous origin. No 
doubt much of the material composing some of the members of 
this series has been derived from the destruction of volcanic 
rocks, more especially the coarser breccia bands, which, however, 
are distinctly stratified and sometimes contain large fragments 
of partially-carbonised wood, showing that the conditions of 
deposition were probably estuarine. 
In his paper “ On the Rocks of the Hauraki Goldfields,” read 
before the Geological Section of this Association at last year’s 
*B2 
