110 president's address — SECTION C, 



Evolution of the Modern Topocp-aphy."^ 



This description forms a fitting introduction to the next stage 

 in the evolution of the present topography. This we must discuss 

 briefly in regard to several aspects as follows: — (I.) Sediments 

 deposited during the erogenic movement; (II.) The initial form of 

 the upliftc^d land mass; (HI.) The effects of subaerial denudation ; 

 (IV.) Sediments deposited subsequent to the main Kiakoura 

 orogeny; (V.) The effects of more recent crust-movement on the 

 features of the coasts and valleys. 



(I.) Spsight (1919) has described under the term Kowhai 

 Series, a group of fold'd or tilted gravels in North Canterbury, 

 wh'ch he has since traced into South Marlborough, f They lie un- 

 conformably on the uppermost Notocene beds, and frequently 

 contain fragments from them as well as from thei lower Notocene 

 and basement rocks. They may be considered as forming a type 

 of molasse in front of the rising range of the Southern Alps, 

 though they have not been overthrust like their Swiss prototypes. 

 A point needing further elucidation is the relationship between 

 the Kowhai gravels and the Great Marlborough conglomerate, 

 which also has been derived from the Nocotene and underlying 

 rocks of the Kaikoura Ranges during a portion of their elevation, 

 though, according to Cotton and Thcmscn, it was a movemefit lO'Ug 

 prior to the main Kiakoura orogeny. If McKay's observation 

 is supported that the conglomerate contains fragments ot 

 " Plio'Cene " beds and transgress from these on to the Amuri lime- 

 stone, their apparent unconforrnitv^ on the* Notocene rocks mieht 

 lead us to place them with the Kowhai gravels. Thomson (1919), 

 hov^ever, questions the^ accuracy of the above record cf observa- 

 tions, and accepts Cotton's (1914) conclusion that the Marlborough 

 conglomerate is conformable on the underlying rocks, and are 

 " fanglomerates " re.^lly interstratified with their uppermost sub- 

 division, being overlain in some parts by fossiliferous "Pliocene" 

 beds. The acceptance of this view would lead us to infer the 

 occurrence of very localised faulting to the extent of, perhaps, 

 3,000 to 6,000 feet in the " Plioceuo " times. Park's view (1910) 

 that the beds are glacial would necessitate nearly as great move- 

 ment in post-glacial times. 



We inay also class with the Kowhai gravels the slightly folded 

 Moutere gravels of the Nelson district (Marshall, 1911). In the 

 North Island, Thomson (1917) has recogrnised an extensive series of 

 marine sands, &c., lying unconformably on the " Pliocene " (and 

 earlier?) rocks of Southern Taranaki. This he terms the Hawera 

 Series. 



(II.) From what has been stated, it is cle^r that the surface of 

 New Zealand at the commencement of " Pleistocene" time was 

 that of a group of differentiallv elevated earth-blocks composed of 



* Dr. Cotton's ceneral discussion of this topic is being published in book-form by 

 the New Zealand Government Printer, 

 t Private communication. 



