Cotton. — Notes o?i Wellington Physiography . 295 



The head of the broad subsequent strike valley — -the Karori-Khandallah 

 or " Long " Valley of the paper referred to above — appears to be at Karori. 

 The branch that is now occupied by the Upper Kaiwarra and the Silver 

 Stream, while also probably subsequent, or perhaps resequent, appears to 

 have been guided by a fault-line. It is remarkably straight, and, where 

 the streams in it have been revived, they develop by erosion a scarp on 

 the north-west side, which continues the line of the Wellington fault-scarp, 

 and closely resembles it. This is apparently an example of a fault-line 

 scarp. It will be seen from the map that this valley makes a decided angle 

 with the longitudinal features, which in the southern part of the Wellington 

 Peninsula are nearly meridional. 



It has been shown* that the inbreak along the Wellington fault took 

 place very recently ; but, if there is any significance in the fact that the 

 Silver Stream rises close to the southern coast and flows inland, the Silver 

 Stream - Kaiwarra Valley is more ancient. Further, there is no topo- 

 graphic evidence of downthrow to the south - east along the line of the 

 valley ; the absence of a scarp is particularly noticeable on the divide 

 between the head of the Kaiwarra and the Silver Stream. 



These facts, together with the presence of the zone of faulted and 

 crushed rock beyond the end of the Wellington fault-scarp, seem to indicate 

 that a much earlier fault movement than that which produced the existing 

 scarp had taken place along the same line and its continuation, and that, 

 during the long periods of denudation accelerated by successive uplifts to 

 which the Wellington area has been subjected, topographic evidence of the 

 movement has been obliterated. This may easily have taken place even 

 though the formation of the original fault happened long after the folding 

 of the strata. 



The foregoing explanation of the features continuing the line of the 

 Wellington fault appears much more satisfactory than an alternative view 

 that fracturing took place contemporaneously with the inbreak along the 

 shore of Port Nicholson, but along a much longer line, and that for a great 

 part of the length of the line shattering of the rocks took place without 

 resultant differential movement.f 



It is easy, on the former hypothesis, to account for the coincidence of 

 the Wellington fault with the older-faulted zone. As the Port Nicholson 

 block sank, the fault forming its north-western boundary followed the old 

 line of weakness. 



The descriptions given in my former paper of the captures of the Silver 

 Stream and Kaiwarra are not affected, but the valleys of these streams, 

 while they may still be regarded as subsequent, must be described as fault- 

 line valleys.J 



The Hutt Valley. 



A brief note on the Hutt Valley is here offered, because the Hutt River 

 continues the line of the Wellington fault to the north-east, just as the 

 fault-line valleys already described continue it to the sotith-west. I am 



* hoc. cit, p. 258. 



t Compare the explanation of fault-line valleys in central Sweden given by Davis 

 (W. M. Davis, Bull. "Am. Geogr. Soc., vol. 45 (1913), p. 519; "Die erklarende 

 Beschreibung der Landformen," Leipzig, 1912, p. 170). 



J Davis, loc. cit.; and also "Nomenclature of Surface Forms on Faulted Struc- 

 tures,' , Bull. Geol. Soc. Am., vol. 24 (1913), pp. 187-216. 



