Speight and Wild. — Weka Pass Stone and Amuri Limestone. 67 



typically developed in the southern part of the area. The beds involved 

 in this discussion are as follows, commencing from the bottom of the 

 series : — 



(1.) Greenland. 



(2.) The Amuri limestone, an argillaceous limestone, named from its 

 great development in the neighbourhood of Amuri Bluff, but 

 also occurring, outside the area under consideration, in the valleys 

 of the Clarence and Awatere, and perhaps in the south of the 

 North Island. 

 (3.) A nodular band, less than 1 ft. thick, composed of phosphatic 



material of two kinds in a matrix of greensand or marl. 

 (4.) The Weka Pass stone, a glauconitic arenaceous limestone as it occurs 

 in the typical locality at Weka Pass, but probably ecmivalent to 

 the higher parts of the Amuri limestone elsewhere, and perhaps 

 to the lower part of the next succeeding higher bed in localities 

 near Kaikoura and Amuri Bluff. 

 (5.) The Grey marl, in its lower portions a glauconitic, arenaceous marl, 

 which in its higher parts in some localities becomes distinctly 

 argillaceous and takes on a true marly facies, and at times 

 becomes decidedly sandy as it passes up into the next higher 

 member of the series. 

 There follows a more detailed description of the second, third, and fourth 

 of these beds, which are the most important as far as this discussion is 

 concerned. 



Detailed Description of the Limestones. 



Amuri Limestone. 



Although the macroscopic properties of the Amuri limestone have been 

 fully described previously by various observers and its microscopic charac- 

 ters have been dealt with by Marshall (1916, p. 95), it may be as well to 

 restate its salient features in this connection. 



As typically developed south of Kaikoura it is an argillaceous limestone, 

 breaking up freely into quadrangular blocks owing to the presence of a 

 well-defined system of cross-joints, a property which is eminently charac- 

 teristic of it wherever it occurs. Owing to some of these blocks being thin 

 and flaky, its surface takes on a tile-like appearance, especially where inclined 

 beds are exposed on a shore-platform. This character is shown throughout 

 the whole thickness of the limestone at Kaikoura and at Amuri Bluff, but 

 farther south, as at Weka Pass, the so-called Weka Pass stone (the higher 

 part of the Amuri limestone as maintained by the authors) does not exhibit 

 to a marked degree this jointed structure, though echoes of it are un- 

 doubtedly present. 



The rock is at times chalky in texture, but is usually hard and occasion- 

 ally crystalline, especially where it has been subjected to pressures result- 

 ing from earth-movements. Notably is this the case at Kaikoura, where 

 it sometimes takes on a subschistose character. Mention should be made 

 here of the chalk deposit at Oxford, which represents this rock in the 

 Waimakariri basin, judging from stratigraphical and lithological evidence. 



The microscope shows the presence of numerous grains of glauconite 

 even in the white-coloured rock, but distinct layers and lenticules of green- 

 sand occur at times, as can be seen in localities like Weka Pass, though it 

 occurs more freely farther north. At Kaikoura it occurs right through the 

 stone, but more especially at the higher levels, where it is organized into 



3* 



