kkcikkknt orogenic movements. 417 



pally to Tertiary and Quaternary uplifting* but the axes of greatest 

 uplifting of the present range coincide approximately with axes of up- 

 lifting of previous ranges within the same area. In other words, repeated 

 orographic movements have taken place along the same axes, and recur- 

 ring uplifts along these axes have followed recurring erosion. In tins 

 way a pre-Mesozoic range arose, carrying up both crystalline and meta- 

 morphosed sedimentary meks, and partially disappeared through erosion 

 and subsidence; then a Mesozoic range arose and its strata became up- 

 tilted, and it in turn was reduced by erosion and subsidence to very 

 small proportions (in its northern half at least, 'nearly or quite to hase- 

 level of erosion) and then in Tertiary and Quaternary time has arisen 

 the present range, which is now undergoing its erosion; but whether it 

 is now rising or subsiding is not determined. 



Position of Outcrops relative to Axes of Uplift. — The oldest rocks appear 

 along the axes of greatest recurring or habitual uplifting, and as these 

 are on the whole approximately coincident with the axes of the present 

 range, the oldest rocks in a given section across the range outcrop quite 

 generally along and near the crests and peaks of the present range, where 

 they are not capped by Tertiary lavas and sediments, and on the whole 

 the rocks highest in the series appear farthest from the crests. As 

 already stated, the coincidence of axes is not complete, and the relative 

 intensity or shear of uplift along the axes has varied greatly, as shown. 

 for example, by the fact that the area, of exposure of older rocks extends 

 far southward of the crest of the western division of the present range. 

 The succession is, moreover, frequently interrupted by faulting. How- 

 ever, the obscurity from these causes can be cleared away by noting the 

 habitual or prevailing position ol areas of outcrop of either of the groups 

 of rocks relative to the axes or areas of greatest and least uplifting. The 

 two principal axes of uplift are by no means the only axes of orographic 

 movement ; neither are the main or minor axes straight, unbroken lines. 

 Each main uplift is made up of a series of uplifts, and the mountain 

 masses are of very irregular shapes. They have, however, one prevailing 

 characteristic, namely, thai their Longer axes have the trend of the por- 

 tion of the range in which they occur. 



The Tertiary and Quaternary uplifting to which the relative relief of 

 the presenl range is due has been principally, if not entirely, by faulting. 

 The history of the range includes also regional orographic movements, 

 both of elevation and subsidence, the character of which has not been 

 determined. 



•This i- abundantly proven hy dislocation and uplifting of Tertiarj and Quaternary deposits 

 md by the obstructions to drainage which caused them ; bill I must I I >inent of 



I fa i" u I'm in p ipor. 



