BaRgrRUM.— Geology of Riverhead-Kaukapakapa District. 149 
Possible Unconformity in Tertiary Strata. 
same horizon as the so-called Whangarei limestone, which Ferrar and Cropp 
(1921), as a result of their recent detailed survey, relegate to the Tertiary. 
South of Auckland City the crystalline limestones have long been 
regarded as mid-Tertiary. 
Б 
in the Tertiary succession, which would have to be located somewhere 
above the limestone horizon. An alternative suggestion, however, is that 
the fragment of limestone was upthrown with other material from a sub- 
jacent limestone stratum by volcanic eruption, and later became incor- 
porated in the conglomerate. 
3. ANDESITIC CONGLOMERATE FORMATION. 
sufficiently discussed on pages 141 and 145. Where undoubted Waitemata 
ed. 
y 
The petrographic nature of the constituent material of the conglomerates 
and breccias was not examined microscopically. In the Waitakere Hills 
mass pyroxene-andesites are exceedingly common. 
4. PLEISTOCENE AND Recent Deposits. 
A synopsis of the nature and occurrence of these beds sufficient for the 
purpose of this paper has been given on page 141. The origin of the small 
' deposits of iron-ore, which are represented by irregularly nodular masses 
of impure limonite 1 ft. and more in diameter, which are scattered plentifully 
upon the surface in a few localities, is debatable. Such deposits are frequent 
throughout northern Auckland, and have varied relations to topography 
for they occur upon tops of plateaux and on benches high on the walls of 
valleys as well as upon their floors. The limonite has undoubtedly originated 
