322 



Transactions. 



It is impossible 

 in the valley, but 

 outlined is probably 



to demonstrate the internal structure of tlie deposits 

 a study of their surface indicates that the theory 

 correct. 



At the Elevation (see figs. 2 and 3) the height is 

 250 ft. At about half a mile from the head of 

 the valley, and at a height of about 200 ft., the 

 flood-plain begins, and extends with normal grade to 

 Koromiko (fig. 3), three miles from the head, where 

 i\xQ height is 55 ft. Throughout this distance the 

 plain is well drained and crops are grown. Much 

 gravel is present in streams and in the soil. Plate XV, 

 fig. 1, is a view of the valley-floor at Mount Pleasant, 

 one niile from the head of the valley, and Plate XV, 

 fig. 2, is a view of the valley-floor at Koromiko. 



Below Koromiko the valley-floor becomes swampy 

 in places. It has, however, still a little fall. Near 

 Para, five miles from the head, may be placed the 

 extreme edge of the fluviatile plain which has de- 

 scended to within a few feet (certainly less than 20 ft.) 

 of sea-level. 



Five miles of valley still remain before the mouth 

 is reached, and this portion of the valley is a con- 

 tinuous swamp, composed entirely of fine silt, and but 

 little above sea-level. There is only an occasional 

 patch of dry flat in a bay, the alluvial fan of a 

 tributary stream. Plate XVI, fig. 1, is a view of the 

 swamp one mile above the mouth. 



Clearly the swamp marks that portion of the valley 

 occupied by lacustrine deposits over which the fluviatile 

 plains of aggrading streams have not yet advanced. 

 For the greater part of the length of the swamp the 

 Tuamarina Kiver traverses it in a channel with banka 

 only 2 ft. or 3 ft. high. Towards the mouth, at Tua- 

 marina, the swampy flat gives place to cultivated land 

 as the level of the surface rises to that of the com- 

 paratively well-drained Wairau Plain. This portion 

 of the valley-floor is illustrated in Plate XVI, fig. 2. 

 It should be regarded rather as an offshoot of the 

 Wairau Plain than as a part of the Tuamarina Valley 

 floor. The actual rise towards the mouth is well shown 

 in the banks of the lower reaches of the Tuamarina 

 River, which increase in height in about half a mile 

 from 2 ft. or 3 ft. to about 15 ft. The stream is ex- 

 tremely sluggish, and its surface must mark an almost 

 true level. The difference in the height of the banks 

 must therefore mark the rise of the ground from the 

 swamp within to the Wairau Plain without. 



