Cotton. — The Uplifted East Coast of Marlborough. 293 



In fig. 8, A is the present position of high-water mark, and AA' is 

 present high-water level. If the former position of high-water mark was 

 seaward of its present position, as at B, the amount of uplift that has taken 

 place (A'B') is less than 6 ft. If, on the other hand, it was shoreward, 

 as at C, the amount of uplift (A'C) is greater than 6 ft. 



In this case it is. improbable that the former position of high-water mark 

 was shoreward of its present position, for there is not a well-defined raised 

 beach. It may, however, have been some little distance seaward. 



These residuals, therefore, afford proof of uplift of 6 ft., or somewhat 

 less. 



4. The Strand-plain of the Marlborough Coast. 



From Cape Campbell south-westward to and a little beyond the mouth 

 of the Clarence River the shore is bordered by an almost continuous strand- 

 plain, broken only at one or two points where outcrops of resistant rocks 

 project slightly seaward as rocky bluffs. This coastal strip will be referred 

 to as the Marlborough Strand-plain. Geographically it is of great im- 

 portance, as it affords the only practicable route between northern and 

 southern Marlborough, and is followed for many miles by the surveyed 

 route of the South Island Main Trunk Railway. Its width varies from 

 a few yards to several hundred yards. Sandhills and dunes form its sur- 

 face at the wider parts, and the material of the beach varies from coarse 

 sand at the north-eastern end to coarse gravel at the mouth of the Clarence. 

 The bulk of the material is, without doubt, supplied by the Clarence, 

 though smaller streams also contribute a share. The waste supplied is 

 swept north-eastward along the coast by a constant along-shore current, 

 and, the supply being very abundant owing to the mountainous and 

 recently uplifted character of the land, it is not surprising that pro gradation 

 of the coast has taken place ; but it is more difficult to account for the fact 

 that progradation has begun very recently. Proof that this is the case 

 is to be seen in the presence of a line of perfectly fresh-looking wave-cut 

 cliffs at the rear of the strand-plain, and it is clear that the sea reached 

 the base of the cliffs very recently. 



Some radical change in conditions must have taken place to bring about 

 this sudden change from retrogradation to progradation throughout the 

 length of forty miles of coast. Two possibilities suggest themselves — 

 (1) increase in the supply of waste, and (2) uplift. 



(1.) Increase in the supply of waste without uplift of the coast is 

 regarded as a sufficient cause in the case of a strand-plain at Ancona, in 

 Italy.* In that case the increase is accounted for by rejuvenation fol- 

 lowing a differential uplift inland. In the case of the Marlborough coast, 

 however, while, as already stated, dissection is now in a very young stage 

 as a result of the recent general uplift, the writer has seen no evidence of 

 more recent differential uplift or warping of the surface that might bring 

 about the change. f Further, the change has taken place so late in 

 Quaternary time that it is difficult to believe that a climatic change of 



* W. M. Davis, Geogr. Journ., vol. 34 (1909), p. 303. 



f At only one place in Marlborough was an indication noted of strong tilting or 

 warping of the surface. This was in the case of the small streams flowing north-west- 

 ward into Lake Grassmere, the uplifted mature floors of which slope down-stream more 

 steeply than the grade of the revived streams. This tilt is probably in sympathy with, 

 or forms one boundary of, a kind of cauldron subsidence, forming a bay, which has later 

 been cut off from the sea by a bar, and has become Lake Grassmere. 



