80 president's address — SECTION c. 



without a definite unconformity. Hector (1886) placed a series 

 of rocks representing the lower half of Hutton's Waipara series 

 into' his Lower Greensand group, considered these to te uncon- 

 formably followed by the Cretaceo-Tertiary beds, comprising the 

 Upper Waipara and basal Oamaru beds, and this again was un- 

 conformably followed by the Upper Eocene and Lower Miocene 

 beds, a group of rocks comprising the formations placed by Hutton 

 in his Upper Oamaru and Pareora systems. Unfortunately, these 

 two names were used by Hector toi designate minor stages in his 

 larger group. The uppermost of Hector's major groups included 

 beds assumed to be of Miocene age. Since Professor Park's 

 abandonment (1905) of his acceptance (1888) of the completely 

 conformable character of the se:[uence cf pcst-Hokonuian fcrma- 

 tion, he has held that there exists a major unconformity separating 

 the Cretaceous from the Miocene rocks in the eastern side of the 

 South Island, which represented an uplift here during the Eocene 

 period, while in the West^'cast coa^.-nieasures were torming. The 

 precise classification of beds on this hypothesis has varied from 

 time to time (1910, 1912, 1917), according as the balance of the 

 evidence appeared to favour one horizon or another as the position 

 of the assumed regional unconformity. • At the commencement of 

 the last decade, it was possible to state that the existence of eVe-ry 

 unconformity that had bsen recognised by one field -geologist, had 

 some time been denied either by some other geologist or by himself. 

 Such is still the case, in so far that the hypothesis of Marshall 

 denies the existence of any unconformity. 



Two' new conceptions, however, have since appeared. Thomson 

 (1917) has suggested the existence of " diastrophic provinces," or 

 regions, throughout each of which the tectonic history has been the 

 same, though differing from that of adjacent regions, and he has 

 outlined the characteristics of several of these provinces (1920). 

 On this hypothesis, the differences of age of the basal beds of the 

 post-Hokonui rocks depends, not only on the overlap of formations 

 on a subsiding uneven surface, but also on the independent move- 

 ment of the crust in different regions. The limestones of 

 adjacent provinces are not necessarily coeval, but represent merely 

 the period of maximum submergence for that particular province. 

 In sorre districts more than one horizon of limestone is present. 

 So, too, the regression of the sea has taken place at different limes 

 in different provinces. There is, however, no need to consider that 

 any unconformities of a general nature are present, such as 

 some earlier observeirs had supposed, though they may extend 

 over a single diastrophic province. Thomson also' has suggested 

 the name " Notocene " ([New (rocks) of Southern (regions)] to 

 indicate the whole group of formations of the Cainozoic deposited 

 before the latest (Kaikoura) orogenic movement, to- which must 

 be added the Upper Middle and the Upper Cretaceous (Albian) 



