ON 
Bartrum.—Geology of Riverhead-Kaukapakapa District. 147 
f 
Papakura and at Waipu and other parts of North Auckland. It must be 
admitted that the fact of the Waitemata beds resting successively upon 
Onerahi series. There is further support of unconformity in the fact that 
Onerahi limestones appear immediately to underlie coarse Waitemata con- 
glomerates in Waitoki Creek and a little east of the junction of Kaukapakapa- 
Parakakau and Kaukapakapa-Silverdale Roads. This abrupt change of 
facies from marine ooze to near-shore conglomerate implies very consider- 
able marine regression, which must have introduced a greater or less degree 
of disconformity. This conception of the existence of unconformity is by 
no means a new one. Unconformity was described many years ago in 
places not far distant from the present district by both Cox (1881) and 
McKay (18844, p. 104), but all fresh evidence is valuable, since some cases 
of such apparent unconformity are explicable by faulting. 
The relations of the Waitemata to the overlying volcanic series have 
been discussed in some detail in earlier pages (see pp. 141, 143-44). It is 
sufficient to state that the evidence available in the area now described is 
inconclusive. 
Origin and Petrography of the Waitemata Conglomerates. 
The conglomerates generally comprise polished and well-rounded pebbles 
and boulders firmly cemented by finer matrix of more angular nature 
The shape and well-polished nature of the boulders, and the occasional 
discovery with them of broken marine molluscan remains, indicate that the 
beds accumulated near the shore-line of the Waitemata seas, but no con- 
clusion has been attained as to the exact location of the latter. Though 
no facts have been disclosed which can throw light upon the possibility of 
the material being a rewash of earlier conglomerates, its general freshness, 
and the rarity of similar conglomerates in older series, are against such a 
supposition. 
In an earlier paper upon the conglomerate at Albany (Bartrum, 1920) 
the writer described many rocks of igneous origin. He has not made 
diorites and quartz-monzonite, which seem to show more intense 
