334 Transactions. 



only ia the Middle Waipara and the Weka Pass, but also in numerous other 

 localities in the region between Mount Grey and the Puhipuhi Valley. 

 They distinguished between the two rocks a transitional layer, generally 

 termed the " nodular " band or layer, which was uniformly about 1 ft. 

 thick over an area of 100 miles by 15 miles, and was composed of phosphatic 

 concretions and nodular masses of phosphatized Amuri limestone in a 

 matrix of greensand or marl, with very 6ccasionally some well-rounded 

 pebbles of quartz and greywacke. The remarkable uniformity in the thick- 

 ness of this layer over such an area was inconsistent with its being a 

 shore-line deposit, and the character of the phosphatic pebbles pointed to 

 their formation in a depth of over 100 fathoms. The upper surface of 

 the Amuri limestone was not, they considered, an erosion surface, but one 

 honeycombed by the borings and burrowings of marine organisms operat- 

 ing on. the sea-floor at a considerable depth, with possibly some solution 

 of calcareous matter by the solvent action of sea-water during a period of 

 halt in the deposition. The borings were filled with the materials of the 

 overlying bed and not by beach deposits. The rigorous parallelism of the 

 Amuri limestone, the nodular layer, and the Weka Pass stone over such 

 an area were inconsistent with a theory of unconformity by emergence and 

 erosion. They therefore concluded that there was no unconformity, but 

 that some alteration in depth or in the conditions of deposition no doubt 

 occurred, which was of no greater amount than that which takes place 

 when a bed of different lithological character is laid down in a perfectly 

 conformable sequence. _^ In describing the Middle Waipara occurrences the 

 authors indicated the existence of a well-defined fault-scarp along the east 

 face of Mount Grey, limiting the extension of the Notocene beds in this 

 direction. In 1919 the same authors discussed the nodular layer as a 

 commercial source of phosphate. 



Thomson (1919) discussed once more the age and origin of the Amuri 

 limestone in Marlborough and Canterbury, arguing that it was in large part 

 a chemical deposit on the outer slopes of the continental shelf. He accepted 

 the view of Speight and Wild as to the conformity of the Amuri limestone 

 and Weka Pass stone, and considered the contact as a plane of non-deposi- 

 tion, which he suggested might be due to a change of conditions putting 

 a stop to chemical deposition, while the formation of purely organic ooze 

 might be so slow as to allow time for the^ boring of the last-formed bed and 

 the phosphatization of its upper surface before the deposition of the foreset 

 greensand began. Dealing with Park's suggestion for an unconformity 

 between the '' saurian beds " and the Waipara greensands, he reaffirmed 

 the Senonian age of the latter beds, rejecting Haast's determination of the 

 brachiopod as Recent, and considered that if any disconformily existed it 

 should be looked for above the Waipara greensands in the dark carbonaceous 

 mudstone down into which the Amuri limestone passes. 



Speight in 1919 gave a description of the tilted gravels of the Kowhai, 

 Grey, and lower Waipara Rivers, and proposed for them the name of 

 Kowhai* series. He concluded that the age was most probably Pleistocene. 



Morgan (1919) gave a general description of the limestones of the area, 

 summarizing previous knowledge. He reaffirmed his belief that there is a 

 true disconformity between the Amuri limestone and Weka Pass stone, and 

 that it denotes a considerable time-interval. 



* Speight spells the name " Kowai." The Lands Department maps give " Kowhai " 

 for the river draining from Mount Grey and Mount BroMii, and " Kowai " for the 

 tributary of the Waimakariri River, and the distinction appears a convenient one. If 

 J^laori orthography is to be strictly followed, " Kowhai " should be used in both cases. 



