274 Geology of 



Texttjee or Bocks and Position of Steata. 

 I shall now proceed to give a general outline of the beds of which 

 this formation is composed, and of their general features and sequence. 



Speaking more specially of their arrangement, we may describe it as 

 a continuation of anticlinal arches and synclinal troughs : but instead 

 of finding the mountains to be formed by the arches and the valleys 

 by the troughs, careful examination shows convincingly that exactly 

 the reverse has taken place. Thus to give only one instance, whilst 

 the enormous mass of Mount Cook occupies a synclinal trough, the 

 broad valley of the Godley river runs along an anticlinal arch. 

 The occurrence of such enormous changes by which the arches or 

 mountains have been converted into deep valleys, and the troughs into 

 high serrated mountains, will give us a faint idea of the amount of 

 time which has elapsed, and the enormous waste which has taken 

 place, before the Southern Alps assumed their present form. The 

 general strike of these sedimentary beds is south-west to north-east 

 but varying considerably, sometimes even in short distances according 

 to the numerous foldings and bends. The strata dip generally at high 

 angles, and stand sometimes almost vertically, a south-east and north- 

 west dip being the most usual. As the greater portion of the 

 beds consist of sandstones of nearly the same character, we may 

 describe the Southern Alps as sandstone chains. Alternating with 

 the sandstones we find slates, shales, brecciated beds (graywacke)^ 

 and conglomerates in almost endless succession, forming generally 

 sharply defined strata. Here and there we observe inter-stratified 

 with them diabasic beds, sometimes in the form of ashes. The 

 sedimentary beds by contact with these ashes have undergone consi- 

 derable changes, so as to assume all the characteristics of chertose 

 rocks. Small beds of limestone, generally in the form of marble of 

 whitish tints, are sometimes intimately associated with these eruptive 

 rocks, whilst under all other conditions the absence of limestone is 

 very striking, even rocks with a calcareous matrix being generally 

 wanting. 



Thus it is evident that we see before us the deposits of rivers falling 

 into the palaeozoic sea, and judging from the position and succession 

 of the boulders of which the conglomerate beds are composed, we may 

 conclude that a large continent or island existed to the east or south- 

 east of Xew Zealand, of which probably the old sedimentary and 

 semi-metamorphic rocks of the Chatham Islands are still a small 



