Speight and Wild. — Weka Pass Stone and Amuri Limestone. 91 



sand. In places, too, these jutting portions have been completely cut off, 

 so that they become detached fragments. Similar occurrences can be 

 seen at times in the estuaries which are filled with calcareous mud and 

 have been completely honeycombed by borrowing molluscs, &c. In this 

 way an apparent erosion surface can be formed ; but the character of the 

 junction under consideration requires a uniformity of conditions over wide 

 areas, and this would be obtained if the bored surface were a sea-bottom 

 and not a shore-line. The increased phosphatization of the fragments of 

 Amuri limestone, and perhaps of the true phosphatic nodules, might be 

 accounted for by the decay of the bodies of the boring organisms, in 

 addition to probable increased phosphatization owing to concentration by 

 the dissolving-out of the more soluble calcium carbonate from the rock. 



The remarkable persistence of the nodules of phosphatic material at a 

 limited level in the limestone renders them extremely useful as a datum- 

 level for comparing the relative age of rocks in the series, and this is all 

 the more valuable owing to the comparative absence of fossils. It may, 

 of course, be suggested that there is more than one layer in the limestone, 

 and that the phosphatic nodules at Kaikoura occupy a different position 

 from those at the Weka Pass ; but the whole of the attendant circumstances 

 of the surrounding beds renders it extremely likely that only one layer 

 exists. If the nodules had been laid down on the bed of a deep sea, then 

 it is likely that the sea extended all over the area in question, and their 

 synchronous formation would be very probable indeed. 



Assuming that this is so, it would clearly indicate that the Weka Pass 

 stone was the equivalent of the upper part of the Amuri limestone in the 

 Kaikoura district and also at Amuri Bluff ; but, seeing that the lower portion 

 of the grey marl at Kaikoura and Amuri Bluff is lithologically a calcareous 

 greensand, it is not at all improbable, that Hutton was partly correct in 

 correlating the Weka Pass stone with the grey marl, only that it is the 

 lower portions of the marl that are equivalent to the upper layers of the 

 Weka Pass stone. However, between the marl and the limestone in the 

 Kaikoura region there is a junction which is analogous to that between 

 the two limestones, in that the limestone immediately below the lowest 

 layer of the grey marl is bored and sporadic phosphatic nodules occur in it. 

 This, of course, indicates some break in time. 



At the Amuri Bluff the thickness of the limestone above the nodular 

 band is reduced to 15 ft. as compared with a thickness of 100 ft. or more 

 at Kaikoura and a great thickness as exposed on the sea-cliffs between 

 the Oaro and Mikonui Creeks. It must be mentioned, however, that as 

 the beds are traced along the coast south of Amuri Bluff towards the 

 Conway River they thin out and the limestones lose their distinctive features. 

 This certainly suggests the vicinity of a shore-line, and therefore there is 

 no improbability that the lower part of the grey marl in that neighbour- 

 hood, especially that part with sandy texture, may be the stratigraphical 

 equivalent of the glauconitic facies of the Amuri limestone farther north, the 

 sea evidently deepening in a northerly direction. It is probable that an 

 easterly extension of the land, either continuous or in the form of islands, 

 divided the Kaikoura part of the sea from that south of the Hurunui. The 

 existence of such a land if it were of low relief would not, of course, negative 

 the contention that a sea extended generally over the site of the present 

 Kaikouras, and that the land had been base-levelled to some extent before 

 being depressed and covered with a veneer of Tertiary sediments. But it 

 must be clearlv understood that the shore-lines of this land must not be con- 



