72 



Transactions. 



Weka Pass Stone. 



In the typical locality near Weka Pass this rock consists of an aren- 

 aceous, glauconitic limestone. In its lower portion the rock presents the 

 facies of a calcareous greensand of very fine grain, with a comparatively 

 low percentage of calcium carbonate, but this percentage increases in the 

 higher levels. (See analyses.) Specks of glauconite are, however, distri- 

 buted throughout the rock. It breaks at times into quadrangular blocks, 

 but rarely with the tily arrangement which characterizes Amuri limestone, 

 though at times there is considerable similarity between the two rocks. 

 Under the microscope it appears to be composed largely of Foraminifera, 

 notably Globigerina, with a considerable amount of quartz and occasional 

 shreds of biotite. The glauconite exists as grains, sometimes as a stain on 

 the quartz, and occasionally filling the cavities of Foraminifera. As com- 

 pared with Amuri limestone it is coarser in texture, more glauconitic and 

 arenaceous ; but the Foraminifera appear to be the same, and, as in the 

 former case, have their cavities filled with calcareous material. The depth 

 at which deposition took place would in all probability be slightly shallower 

 than that at which the Amuri limestone was laid down. 



Away from the typical locality the rock exhibits considerable variation. 

 It is sometimes more glauconitic, and in fact passes into a calcareous green- 

 sand ; while in other places it becomes more sandy and friable. The former 

 of these two facies represents in all probability a deposit either in shallower 

 water or nearer a shore-line, but there is no doubt as to its equivalence to 

 the more calcareous rock. It is perhaps not truly synchronous, in that it 

 may mean the gradual extension of the deposit into shallower water as 

 physical conditions in the area changed ; but the stratigraphical position 

 and the relationship of the two facies to the underlying Amuri limestone 

 are practically identical. 



(1.) Weka Pass stone 2 ft. above Amuri* limestone. (Coll. J. Park.) 

 (2.) Weka Pass stone, average sample " from Waikari end of Weka 



Pass, from cliffs N.E. of stream a few chains above the railway 



viaduct." (Coll. J. Park.) 



Historical Summary. 



The following is a summary of the opinions held by the authors cited 

 in the bibliography at the end of the paper, in the order of time in which 

 they are expressed : — 



Hector says (1869, p. xii), " The above (3 and 4) [grey marl] rest uncon- 

 formably on blue and grey marly sandstone, sometimes passing into chalk, 

 the formation resembling, in mineral character, the English chalk marl. 

 In the same formation, farther north, flints occur." There is some doubt 



