338 REPORTS OF RESEARl H COMMITTEES. 



tectonic units of the Kaikoura orogeny, and the movements have 



been more nearly epeircgenic in character. Cook Strait, which 



separates the main islands of New Zealand, is ascribed to subsi- 

 dence Oif eiarth-blocks. 



Exceptionally, as at Wellington, strong differential movement 

 has taken place very recently, and in this instance strong subsi- 

 dence of a small area bounded in part by a fault has allowed of 

 local drowning, with the formation of the harbour of Port Nichol- 

 son. 



Cotton* has shewn also that the lowlands bordering soir.e parts 

 of the New Zealand coast are largely built by marine prograda- 

 tion, though the possibility of uplift accompanying progradation 

 is not excluded. He has described evidence of alternation of 

 retrogradation and progradation en a considerable scale since the 

 occurrence of the latest appreciable crustal movement. 



J. Hendersonf has pointed out the block-faulted structure of 

 Western Nelson, and regards the existing block-mountains and 

 depressed blocks as the result of rejuvenation of movements which 

 occurred from time to time in the Tertiary period, and were sepa- 

 rated by inter v^als of peneplanation on the higher and sedimenta- 

 tion on the lower blocks. 



In the Aroha district, Auckland, he has described step-faulting, 

 marked by a series of fault-scarps forming the boundary of a block, 

 the uplift and tilting of which are indicated by rejuvenation and 

 diversion of streams. | In the Reefton and Gisborne§ districts he 

 has described marine benches, with associated river terraces, indi- 

 cating uplift. He has explained ccnsiderable changes in the 

 course of the Waikato River as the result of alluviation followed 

 by rejuvenation. II 



In North Auckland Henderson^ has recognised the occurrence 

 of dissected plateaux of soft sandstone, and finds also that the 

 rivers are entrenched below their main valley-floors, as well as 

 being drowned at the mouths. In explanation of this he suggests 

 that after considerable depression of the land a relatively slight 

 elevation took place. 



* (!. A. Cotton, Preliminary Note on the Uplifted Coast of Marlborough, Trans. N.Z. Inst., 

 vol. -16, pp. 286-94, 1914. The Geomorphologv of the (Joastal District of South- Western Wel- 

 lington, Trans. N.Z. Inst., vol. 50. pp. 212-22, 1918. 



t J. Henderson, On the Genesis of the Surface Forms and Present Drainage-systems of West 

 Nelson, Trans. N.Z. Inst., vol. 43, pp. 306-15, 1911. Reefton Subdivision, N.Z. Geol. Surv. 

 Bull. No. 18 {new series), 1917. 



t .T. Henderson, Aroha Subdivision, N.Z. Geol. .'iiirv. Bull. No. 16 (neir .leries), 1913. 



§ .1. Henderson and M. Ongley, Uisborne and Whatatutu Subdivisions, N.Z. Geol. flurr. Bull. 

 No. 21 {new series), 1920. 



11 J. Henderson, Notes on the Geology of the Waikato Valley near Maungatautari. N.Z. 

 Journal of Science and Technolocjii, vol. 1, pp. 56-60, 1918. 



•i J. Henderson, Coal Possibilities of tlie Warkworth District, Eighth Annual Report of the 

 Geological Survey Branch, pp. 157-58, N.Z. Pari. Paper, C. — 2, 1914. 



