■ . ! 
1918.] The N.Z. Journal of Science and Technology. 285 
Kaikoura and Seaward Kaikoura Mountains, though in the latter cast, 
tilted-block origin is still apparent in the broad outlines of the mountain 
masses (fig. 2). 
The covering strata on the low-1 ying blocks have been maturely dis¬ 
sected, and over large areas almost completely planed, by erosion since 
I the deformation, and, as a rule, much of the present relief in the district 
still covered by these rocks is due to rejuvenation brought about by 
recent movements of uplift, generally regular and affecting considerable 
areas, so that, as far as a particular district is concerned, they may be 
classed as regional. 
The fault-scarp boundaries between the high- and low-lying blocks are, 
as a rule, dissected to the mature stage. Rejuvenation of the dissected 
scarps by renewal of movement, with the formation of new and continuous 
scarps at the base or the production of sharp facets on spur-ends, has 
taken place very rarely. 
It is known from the occurrence of isolated remnants and even of 
scattered residual boulders (sarsen stones) of the harder beds that the 
covering strata were widespread, and eroded portions of them occur now 
along the bases of many scarps, while it is clear that they were formerly 
present along others. Clearly, therefore, the basal parts of the scarps as 
now exposed were not parts of the initial forms : or, in other words, the 
basal parts, having been exposed by erosion, are fault-line scarps, though the 
higher parts are true fault-scarps. Though the scarps are thus composite, 
when maturely dissected they resemble true fault-scarps very closely. 
It is perhaps in Central Otago that the structure and the history of the 
earth-movements are best displayed by the topography. The landscape 
is a mosaic of blocks. A group of the lower-lying blocks determines a 
chain of basins, which have been known in the past as “ old lake-basins, ” 
though it is not clear that they have ever been occupied by lakes. This is the 
chain of lowlands followed by the Otago Central Railway. The depressions 
occupied by large lakes farther west— e.g., Wakatipu and Te Anau—were 
perhaps initially of the same nature, but they have been profoundly modi-* 
fied by glacial erosion. In Central Otago the covering strata are largely 
of terrestrial origin, and have been preserved over considerable areas on the 
low-lying blocks in the depressions, though only a few remnants survive on 
the higher blocks. The configuration of the higher blocks shows very clearly 
the nature of the deformation, as extensive areas of the fossil plain that formed 
the floor on which the cover lay are preserved. The manner in which the fossil 
plain is warped and dislocated is clearly seen. The majority of the Central 
Otago blocks are elongated, trending north-east and south-west, and are more 
or less tilted towards the north-west. These blocks slope down gently to their 
north-eastern ends to merge with the chain of depressions previously referred 
to, which occupies a complex fault-angle depression at the base of the fault- 
scarps bounding a complex of high blocks forming the northern highland of 
Otago. 
In the North Island the mountain blocks from which the covering strata 
have been stripped occupy a much smaller proportion of the area than 
in the South Island, and the individual blocks seem to be larger. The 
most prominent highland block, or series of blocks, is that forming the 
Rimutaka, Tararua, Ruahine, and Kaimanawa Ranges. Along the eastern 
base of the Rimutaka Range there is a prominent scarp, and a broad 
fault-angle depression—the Wairarapa Valley—lies between this scarp and 
the back slope of a block forming the east-coast ranges. 
