Marshall. — The Younger Liinestunes of Neir Zealand. 95 



(/.) EsTc River, North Canterbury. 



A very fine-grained type, consisting mainly of fine-grained calcite, which 

 does not appear to show any trace of organic origin. One specimen of 

 Rotalia. Many Globigerinae of small size. 



(k.) Amuri Limestone, Weka Pass, North Canterbury. 



The chambers of Globigerina, which are generally isolated, are fairly 

 numerous. By far the greater part of the rock consists of very finely grained 

 calcite. This appears to be the general structure of the Amuri limestone 

 over the whole of North Canterbury and Marlborough, and even in the 

 highly siliceous and flinty varieties of Ward and the Ure River no remains 

 of siliceous organisms can be distinguished, probably because they have 

 been dissolved, for their presence is clearly shown in small number in the 

 limestones of Amuri Blufi and Kaikoura. 



A type of this rock has been found near Oxford, and in this locality it is 

 soft and chalky. Hutton stated that this was the remains of an old coral 

 reef, a most unlikely origin in the light of these descriptions of New Zealand 

 limestones, for in none of them has the remains of any coral been found. 



At the Weka Pass a glauconitic quartzose limestone rests on the Amuri 

 limestone. A number of rock-slices from the immediate vicinity of this 

 junction have been examined. It is found that near the junction the Amuri 

 limestone contains a considerable number of grains of quartz sand and some 

 glauconite, as well as some brown mica. The presence of these minerals is 

 associated with the appearance of different and larger species of Foraminifera, 

 including Cristellaria and Rotalia. These characters emphasized to a greater 

 extent are the features that distinguish the overlying Weka Pass stone from 

 normal Amuri limestone. There are small isolated nodules of the Weka Pass 

 stone embedded in the Amuri stone without a sharp boundary between them, 

 In addition, there are also inclusions of the Amuri limestone embedded in 

 the Weka Pass stone. The microscopic structure and relations of these 

 limestones, therefore, serves to indicate that there is a strong resemblance 

 between these stones near their contact, and that such difierences as there 

 are would be a natural result of the shallowing of the water and of an increase 

 in the velocity of the ocean-currents. There is independent evidence of the 

 shallowing of the water at this time in the nature of the deposits that every- 

 where rest on the limestone. From a geological standpoint it is a most 

 remarkable suggestion that a pure Globigerina ooze should be overlaid 

 uncomformably, though without change of strike or dip, by another rela- 

 tively deep-water deposit containing the same microscopic minerals and 

 organisms as the underlying rock, especially when the one ruck lies directly 

 on the other continuously over a wide area of country. 



Opinions suggested by a Study of these Limestones. 



The examination of the structure of these limestones and the recognition 

 of the general nature of their component organisms would naturally be 

 expected to throw some considerable light upon the conditions under which 

 they were formed, and on their age. 



So far as the conditions under which they were formed are concerned, 

 we gain a decided amount of information. The limestones are, as a rule, 

 remarkably free from contaminating sediment, and this fact alone indicates 

 that they were formed at some distance from land, or that the land area 

 was small and did not support large rivers that coidd supply any important 



