PRESIDENT S ADDRESS — SECTION C. 



81 



beds. Though objections hav« been raised toi this convenient 

 term, we may follow here the example of the Director of the 

 Geological Survey in adopting it. 



The work of the officers of the survey has brought to' light a 

 further conception. Block-faulting and tilting of the crust, so 

 marked a feature of Pleistocene times, was not confined thereto, 

 but occurred at intervals from Cretaceous to' recent times. This 

 was suggested to Morgan and Eartrum (1915), and by Henderso'n 

 (1917), as a result of studies in the West Coast Coalfields (South 

 Island), and is confirmed by the study of the Gisborne region by 

 Henderson and Ongley (1920). The movements of the blocks 

 wera chiefly vertical or accompanied by tilting, but along the fault- 

 planes the strata may be much crushed or upturned. Erosion pro- 

 ceeded puri pasxu with eleivation, and the beds laid down after 

 faulting may rest with apparently perfect conformity on the 

 undisturbed areas, but with small or great unconformity where 

 near to the fault-plane, or whem lyincr on a tilted block, or they 

 may cross without disturbance a zone of fault-breccia in the under- 

 lying rock. This view accords well with the hypothesis of pro- 

 vincial diastrcphism. Until more extensive work has been done 



Fig. 5. Diagram to illustrate the occurrence of a general but deceptive uncomtormity 

 obscuring an erosion-interval in the deposition of the " Notocene " roclcs. 



it would be premature to discuss the stratigraphic or palseontolo- 

 gical value of such breaks, or whether any of them may be con- 

 sidered to be universal throughout the Notoceiie System. 



Schemes of subdivision of the Notocene rocks into stages have 

 been advanced by Thomson (1916) and Marshall (1916, 1919). 

 Thanks to the enthusiastic collecting of several workers, the rapid 

 extension of the faunal lists is rendering the use of the Lyellian 

 percentagD-method of increasing value in the determination of 

 relative ages. A new method of calculation suggested by 

 Thomson (1920) promises tO' be very helpful in this respect, in 

 that each collection madei is compared, not with the re.cent fauna 

 only, but also with the fauna which eixisted (so far as is known) 

 in each of the periods represented by the well-ascertained stages, 

 and the affinities of the new collection become thus well established. 

 The present rapid extension of knowledge of these rocks may be 

 expected to continue for some time, and what follows is merely a 

 pr ogress -repo rt . 



