108 Transactions. 



erroneous assumption that the hard limestone bands in that locality had 

 been metamorphosed during deposition by a lava-flow. 



Hutton (1875, p. 54) said, " No eruptive rocks are found associated 

 with the older or Ototara group of strata .... but at Oamaru Heads 

 we have clear evidence that during the deposition of the Upper or Trelissic 

 group of beds volcanic action was going on." 



In 1876 McKay placed the Waiareka tuft's below the Ototara stone, 

 and asserted that a younger series of volcanic rocks occurred at Oamaru. 



In 1886 Hutton verified McKay's observations as to the position of the 

 Waiareka tuffs, but repudiated his own former statement that volcanic 

 rocks were associated with the upper beds of the series. He recognized 

 but one horizon of volcanic rocks, the Waiarekan, and considered that the 

 volcanic matter in the upper part of the limestone was detrital only. 



In 1905 Park asserted that volcanic activity commenced at the end 

 of the Waihao greensand period and culminated during the deposition of 

 the Hutchinson Quarry beds. 



Summarily, according to McKay there were two distinct periods of 

 eruption, the pre-Ototaran and the pre-Hutchinsonian ; according to Hutton 

 but one, the pre-Ototaran ; while according to Park activity continued 

 during the Waiarekan, Ototaran, and Hutchinsonian periods. 



IV. Effects of these Opinions on the Classification of the Oamaru 



Series. 



The fact that the volcanic rocks are always followed by limestone 

 has undoubtedly caused confusion in classification, and in the absence of 

 distinctive fossils in the limestone the igneous rocks near the coast have 

 been assumed to be Waiarekan. McKay, although recognizing the Tertiary 

 volcanics at Oamaru as distinct from his Cretaceo-Tertiary Waiarekan tuffs, 

 erroneously supposed the breccias at Kakanui to be Waiarekan (1877, p. 56), 

 whereas they are middle Ototaran. Hutton in ascribing the volcanic rocks 

 at Oamaru to the Waiarekan was necessarily compelled to introduce an 

 unconformity above them to account for the non-existence of the Ototara 

 stone. Park's contention that volcanic activity culminated during the 

 Hutchinson Quarry period may be true or not true ; it depends entirely on 

 the connotation of the term " Hutchinson Quarry beds." McKay seems 

 to have been the first geologist to use the term in classification (1882, p. 58). 

 Later in the same report (p. 76) he seems to restrict the term to the green- 

 sands alone, correlating the calcareous beds with the Otekaika limestone, 

 and the volcanic rocks below with the Kekenodon beds. In other words, 

 in the typical locality he excludes the limestone bands. This is in sub- 

 stantial agreement with Thomson's use of the term 'Hutchinsonian" 

 (1916, p. 34). 



Hutton was probably correct in considering much of the volcanic matter 

 detrital only, as will be demonstrated in the sequel. Further, McKay con- 

 sidered the volcanic rocks of Oamaru Creek as evidence of a land surface, 

 and he supposed the overlying rocks to be markedly unconformable to 

 them (1877, p. 58). My own opinion, based on the evidence furnished below 

 and on further observations in other parts of the Oamaru district, is 

 that deposition was continuous from the base of the Ototaran to the top 

 of the Awamoan, but interrupted locally by submarine eruptions resulting 

 in the formation of volcanic banks or islands, which, however, suffered rapid 

 denudation, and this minor phase is recorded in the slight unconformities 

 now to be seen in the tnfaceous beds. 



