Tho-MSO-V. — Geology of Middle Waipara and Weka Pass District. 329 



time, were elaborated by him in later papers on other districts, and, thanks 

 mainl}^ to the physiographical evidence in support brought forward in recent 

 years by Cotton, are now generally accepted by New Zealand geologists. 



In 1885 Hutton once more called attention to the contact between the 

 Amuri limestone and the Weka Pass stohe throughout North Canterbury, 

 and its importance in respect to the classification and correlation of the 

 Notocene sequence. Within the district he examined the contact at only 

 one point — viz., in a small gorge of the Weka Pass Stream just above the 

 railway -viaduct — and stated that he believed this to be the only section 

 in the neighbourhood where it could be studied. Although the contact is 

 carefully described, the latter statement is quite incorrect, and is of interest 

 as typifying Hutton's general neglect of detailed field-work. Not only may 

 the contact be observed in numerous places within the Weka Pass, as 

 McKay in 1887 pointed out, but it is exposed at short intervals throughout 

 the whole length of the district. Hutton noted the common dip of the 

 two rocks, but again stated his conviction that the water- worn surface of 

 the Amuri limestone, and the presence of pebbles in the lower 6 ft. of the 

 Weka Pass stone, were conclusive proof of unconformity. In addition, an 

 overlap of the Weka Pass stone on to the slate rocks of Mount Alexander 

 at Hurunui was adduced as further proof of unconformity. Hutton also 

 gave lists of fossils from the Weka Pass stone and the " grey marls," 

 showing that these two rocks, along with the Mount Brown beds, 

 belonged to the Oamaru system, and pointed out that the Amuri limestone 

 contained no characteristic fossils, but was always associated with under- 

 lying rocks containing remains of marine saurians and Cretaceous MoUusca. 

 Consequently he claimed that the palaeontological break must be between 

 the Amuri limestone and the Weka Pass stone, exactly where the strati- 

 graphical evidence placed it. " If the line between the Waipara and 

 Oamaru systems be taken immediately above the Amuri limestone, hardly 

 any species of Mollusca, perhaps not a single one, will be found on both 

 sides of it ; whereas if it be drawn anywhere above the Weka Pass stone 

 there must always be a large number of species found on both sides of it." 



The attack thus made by Hutton on the classification adopted by Hector 

 and the officers of the Geological Survey opened a period of very keen 

 controversy, mainly between McKay and Hutton. McKay (1887a) reaffirmed 

 the conformity of the Amuri limestone and Weka Pass stone on the grounds 

 of the strict parallelism of the two rocks, and attempted to explain away 

 the appearances of unconformity. The so-called shattering of the Amuri 

 limestone he attributed to the eft'ects of jointing combined with a downward 

 working of the greensand into the joints, and he published analyses of the 

 Amuri limestone and the supposed pebbles of the same rock in the green- 

 sand to prove that the latter were concretionary phosphatic nodules. The 

 Colonial Analyst called the insoluble residue from the Amuri limestone 

 (42-74 per cent.) " almost pure sand (fine-grained)," and McKay suggested 

 that, as the limestone was less than 50 ft. thick in the Weka Pass, " should 

 the percentage of sand be much increased, the equivalent beds three or four . 

 miles distant might very well be mistaken for other than they are, or be 

 absent," and hence overlap of the Weka Pass stone was no necessary proof 

 of unconformity. He further cited a number of species of fossils from the 

 Amuri limestone or lower beds which were also found in higher beds, the 

 majority of his list, however, being from localities outside the district. 

 Hector (1887a), in commenting on McKay's paper, accepted the " definite 

 chemical proof that the supposed fragmental layer at the base of the Weka 

 Pass stone is truly concretionary," and published a map and section of 

 the Weka Pass showing an unconformity between the " grey marls '" and 

 the overlying Mount Brown beds. 



