142 Transactions. 



map (Plate XXXIII, fig. 2). This plain (the Mangaroa Swamp) is so 

 level that it is highly probable it is in part a filled-in lake due to warping, 

 rather than a plain wholly formed by aggradation. 



The Mangaroa River near its junction with the Hutt is now degrading 

 again, and this rejuvenation is shared by the upper part of the Hutt River 

 and its other tributaries. It is due apparently to steepening of the upper 

 course of the Hutt by the latest warping movements. 



Appendix. 

 The Problem of the Turakirae. Coastal Plain. 



As mentioned previously, there is, to the east of the Port Nicholson 

 depression, besides the uplifted and tilted platforms that have been described 

 a less-strongly uplifted coastal plain, which fringes the coast eastward of 

 Baring Head, around Cape Turakirae, and along the western shore of 

 Palliser Bay. This feature has been described by Aston (1912) as " the 

 raised beaches of Cape Turakirae." Though, on account of its roughness, 

 " plain " may not seem an appropriate term to apply to it, the fact that 

 it is a recently-emerged strip of sea-bottom brings it into the class of coastal 

 plains as defined in systematic geomorphology. As the deposit of gravel 

 and boulders on it is merely a thin and discontinuous veneer, and the obvious 

 stacks and many of what are apparently boulders remain attached to bed- 

 rock, it might also be described as a plain of marine erosion. Aston referred 

 to part of it as a " boulder plain." 



Though the seaward slope of the coastal plain is very steep (about 1 

 in 10), the greater part of it is not yet cliff ed at the margin. Unlike the 

 higher benches, the Turakirae coastal plain is not tilted to the westward — 

 or, at any rate, is not tilted to an appreciable extent. Aston found the 

 height of the highest strand-line, at the rear of the plain, to be 95 ft., 

 while the width varies from 250 to 400 yards. 



The great size of the boulders and the general ruggedness of the former 

 sea-bottom correspond with the exceptional steepness of its profile, which 

 allowed the sea to abrade the cut platform and attack the cliffs behind 

 the former shore-line with the energy of the ocean-waves practically 

 undiminished by the friction of the bottom. 



The plain is widest at Cape Turakirae, and it tapers off and ends about 

 five miles north-eastward. 



In addition to that developed prominently in places at the rear of the 

 plain (No. 5 beach of Aston), Aston has recorded the presence of four other 

 storm-beaches at lower levels, built during pauses in uplift. Those which 

 he terms Nos. 4, 3, and 2 are at heights of 80 ft., 60 ft., and 40 ft. above 

 sea-level. The latter two are very prominent and continuous around Cape 

 Turakirae (Plate XXXII, fig. 2). The beach termed No. 1 by Aston he 

 regarded as formed prior to 1855 and uplifted by the movement accompanying 

 the earthquake of that year. Recent observations by the writer show, how- 

 ever, that parts of this beach have now been reworked and incorporated 

 into the modern beach, as has occurred also on some other parts of the 

 coast near Wellington. In some places, no doubt, there was no storm- 

 beach ridge prior to 1855, while in other places the pre-1855 ridge has since 

 been destroyed by marine erosion. 



The continuous raised beach-ridges ought to record any tilting along- 

 shore that has occurred since their formation. Down-tilting following even 

 uplift would cause the raised beaches, when traced laterally, to disappear 

 successively beneath the present sea-margin, while progressive tilting during 



