68 



Transactions. 



well-defined layers, this being especially the case above the zone of phos- 

 phatic nodules. Similar well-defined interstratified greensand bands are 

 noted by McKay and by Thomson as occurring in the development of 

 Amuri limestone in the valley of the Clarence. This is important, seeing 

 that this higher portion, notably at Kaikoura, has been definitely recog- 

 nized by various authorities as belonging to the Amuri limestone and not 

 separated from it by any unconformity. 



Another notable constituent of the limestone is flint, which occurs in 

 lenticules and in irregular masses, as has been fully described by Thomson 

 (1916, pp. 52-58). In Marlborough flint is specially important, but the 

 amount progressively diminishes on being traced south. It is a well-marked 

 constituent at Amuri Bluff and at Gore Bay, and it also occurs in the 

 chalk deposits at Oxford, thus having a somewhat wider distribution than 

 might be inferred from Thomson's paper. The flint is found both above 

 and below the layer of nodules in the Kaikoura and Amuri Bluff districts, 

 so that its presence or absence cannot be regarded as a criterion of age. 

 Thomson has regarded the flint as formed by chemical precipitation (1916. 

 p. 56). If that is so it must have been precipitated subsequently to the 

 boring of the limestone, unless the boring animals have been able to pene- 

 trate flint itself, as the flint occurring in situ occasionally shows burrows 

 filled with glauconitic material. 



The lower portions of this limestone are decidedly more argillaceous, 

 and merge into a true marl. 



Table I. — Analyses of Amuri Limestone from Weka Pass. 



Si0 2 



A1 2 3 



Fe 2 3 



CaO 



MgO 



P 2 6 



co 2 



Moisture and organic matter 

 Alkalis, &c. 



100-00 100-00 100-00 100-00 100-00 



(1.) Amuri limestone at contact, near railway viaduct. 

 (2.) Amuri limestone, upper layer, same locality. 

 (3.) Amuri limestone, 35 ft. below upper surface. 

 (4.) Average sample, thickness of 40 ft. 

 (5.) Sample 2 ft. below upper surface. 



Table II. — Partial Analyses of Amuri Limestone from Kaikoura. 



Insoluble in acid 

 Fe 2 3 and A1 2 3 



p o 



x 2 w 5 



(1.) Sample 2 ft. to 4ft. below contact. 

 (2.) Sample at the contact. 



