182 The N.Z. Journal of Science and Technology. [May 
(4.) From the Conway River to the Oaro, the beds being specially well 
developed in proximity to Amuri Bluff. A detached area also 
occurs in the Upper Conway valley. 
(5.) At Kaikoura Peninsula. 
(6.) In the Hapuku district, specially in the basin of the Puhipuhi 
River. 
The characteristic limestone of this region is known as the Amuri 
limestone, from its special development at Amuri Bluff. It is very white, 
slightly argillaceous, thoroughly jointed, and from the special number of 
the Foraminifera it contains must be regarded as a deep-sea deposit. 
In places it is glauconitic, the glauconite being either distributed through 
the rock in the form of sporadic grains or forming distinct layers of 
glauconitic limestone. It also contains irregular lenses, layers, or masses 
of flint, usually a small proportion of the rock, but north of Kaikoura 
forming in places its chief constituent. The proportion of CaC0 3 present 
usually varies between 80 and 90 per cent. ; its average content 
of phosphate is low—certainly below 1 per cent.—but near its upper 
surface it rises till the amount approaches 5 per cent. A deposit of 
chalky limestone, probably contemporaneous with the Amuri limestone, 
and resembling it in some respects, occurs near Oxford, at the base of the 
foothills. 
Above the Amuri limestone lies the Weka Pass stone, a limestone of 
different texture, with a more decidedly glauconitic character, and con¬ 
taining also more siliceous material and as a consequence a lower- 
percentage of CaC0 3 . At times this bed becomes a true calcareous green¬ 
sand. In our opinion it represents a slightly different facies of the Amuri 
limestone, a difference attributable to slight changes in the condition of 
deposit; but by other authorities it is regarded as an entirely different 
stratum, separated from the underlying limestone by a complete geological 
break, during which the upper surface of the Amuri limestone was raised 
above sea-level and deeply eroded. The percentage of phosphate in the 
Weka Pass stone does not differ materiallv from that of the Amuri 
< «/ 
limestone, with the exception of a layer immediately at its base, which 
from its peculiar features will be separately mentioned and will be called 
hereinafter the “ nodular layer/ ’ This layer and the limestone immediately 
associated with it is the most promising horizon in these rocks for phos- 
phatic material. 
The line of junction between the two facies of Amuri limestone is 
marked throughout the whole region of North Canterbury by the occur¬ 
rence of a well-defined layer of glauconitic limestone in which are nodular 
fragments of material which show a relatively high percentage of P 2 0 5 , 
at times as much as 23 per cent. This layer varies in thickness and in the 
number of nodules it contains, and in general the latter are scattered 
through the lower 3 ft. or so of the overlying limestone, but they always 
increase in number near the junction. The layer is best defined and most 
concentrated on the shore platforms to the east of Kaikoura Peninsula,, 
to the south of Amuri Bluff, at Port Robinson, and in the bed of the 
Motunau River. At Kaikoura and at Amuri Bluff the bed has a maximum 
thickness of from 10 in. to 12 in., and the nodules form up to 50 per cent, 
of the material of the layer, the remaining portion being glauconitic 
limestone. The nodules are composed very largely of this material, but 
they always show the presence of phosphate. The original source of this 
has not been definitely determined, but in numerous cases fragments of 
