Bell and ChARK^.— Geological Reconnaissance of Northernmost N .Z . 621 



Inconstant beds of higUy carbonised, brown or black peat, apparently- 

 overlying the uppermost layers of the Older Debris, but possibly uncon- 

 formable to them, occur in various places, especially at the north end of 

 Rahia Bay. Trunks of trees and roots in situ are of frequent occurrence 

 in these deposits, which are too small to be of value as fuel. Kauri-gum is, 

 however, found in fair quantity in and immediately under them. 



The firmer scrub-covered comitry which lies to the east of the ever- 

 advancing west-coast sands, the similar minor accumulations in Spirits 

 Bay, the low sandy flat which separates the North Cape headland from the 

 rest of the high land, and the low flats in the south-east part of Parenga- 

 renga Harbour, although doubtless much younger than the stratified beds 

 just described, are also included under this heading. The occurrence of 

 great quantities of kauri-gum and of abundant remains of large trees in the 

 swamps on the land-surface — formed of these beds — points to a protracted 

 period when the land became clothed with a great kauri forest. 



Newer Debris. 



The most important of the recent deposits are the widespread sand-dmies 

 at present drifting in from the east and west coasts, and the alluvial de- 

 posits accumulating in the various swamps and ponds. 



Judging from its present rapid rate of advance, the wind-blown sand 

 can only have begun its inroads since the destruction of the kauri forest 

 by the early Maoris. The peculiar topography produced by these drifting 

 sands has already been described. It only remains here to notice the 

 remarkable difference between the east- and west-coast sands. That of the 

 east coast is almost pure silica, and was in former days used for moulding in 

 the ironworks at Onehunga and in the manufacture of glass at Auckland. 

 That of the west coast is of the more ordinary type of quartz and shell sand. 

 Some of the sands near Cape Maria van Diemen and in Spirits Bay consist 

 entirely of finely comminuted shells of great beauty. 



Older Igneous Rocks.* 



We propose to subdivide the igneous rocks of the Aupouri Peninsula 

 into an older (or pre-Miocene) and a younger (or Miocene) group. The two 

 series have not been found in contact. The only evidence for this division 

 of the igneous rocks consists in the petrological differences between the two 

 series, and in the much greater degree of alteration of the group regarded as 

 older. The younger group has already been described under the Coal Point 

 Series. The older igneous rocks may belong to one or more distant periods. 

 Some, apparently, are associated with Mount Camel rocks. f Some are found 

 associated with the Whangakea Series, though whether contemporaneous 

 or intrusive is not clear. Others are found intruding and altering Eahia 

 rocks. In other cases they occur unassociated with sedimentaries. 



Whether or not, therefore, the whole assemblage is to be regarded as of 

 post-Rahia date must for the present remain uncertain. We propose merely 

 to describe the most important occurrences. Speaking broadly, it may be 

 said that the older igneous rocks are more plutonic in character to the east — 

 i.e., towards North Cape — and more effusive in aspect towards Cape Maria 

 van Diemen and the west coast. 



* In this part we are much indebted to Professor Marshall, who examined the micro- 

 scope sections and gave us valuable notes on them. For the final results we are, of course, 

 solely responsible. 



t Hector, Rep. G.S., 1892, p. Ixxxi. 



