344 Transactions. 



margin of the area, in close proximity to the Trias-Jura rocks, and 

 isolated this remnant from the main mass of limestone which forms 

 the crest of Castle Hill. This line of fault can be traced up Coleridge 

 Creek to the extreme south-west corner of the area, as is evidenced by 

 the blocks of limestone with westerly dip left in isolated positions high 

 up on the western side of the valley of this stream. The straight align- 

 ment of its walls is strongly suggestive of glacier action, but there is no 

 doubt its original form was determined largely by the fault-line. 



The centre of the basin is masked by an overburden of Recent shingle 

 and other river deposit, and on the eastern side the dip of the beds is in- 

 wards as a general rule, but in one or two cases, as at the gorge of the Porter 

 River, it is almost vertical ; on the whole, however, the folding is less pro- 

 nounced on the eastern margin of the basin than on the west. 



Farther east, in the lower part of the Broken River Valley, are outliers 

 of the coal-measures belonging to the lower part of the Tertiary or the 

 Upper Cretaceous series, as is clear from the presence of Conchothyra and 

 other fossil molluscs. These have evidently been folded on axes running 

 in a general north-and-south direction, and the surface on which they were 

 laid down shows evidence of considerable warping. The coal-measures 

 usually occupy the lower levels of deep valleys, where they have been pro- 

 tected from denuding agents. There is some evidence of faulting, and in 

 one case at least, in the bed of Sloven's Creek, the Trias-Jura rocks have been 

 bodily pushed over the Tertiaries from the eastward. It is extremely 

 probable that both of the parallel valleys of Sloven's and Winding Creek 

 have been determined by faulting. In one or two places there occur, inter- 

 calated in the greensands which overlie the coal, irregular beds of angular 

 greywacke pebbles up to 3 in. in diameter which cannot have travelled far 

 from some exposed rock-surface; but, judging from the lie of the coal-lx'ds. 

 the surface did not resemble that which now exists. 



The remaining portion of the Waimakariri basin, with whose features 

 I am not at present as well acquainted as I should like, is no doubt of similar 

 origin to the Castle Hill area. Fragments of coal-measures are found in 

 various portions of it, and there is a great mass of limestone in the valley 

 of the Esk River near Mount White, and, judging from its presence, as well 

 as that of occasional small remnants of sedimentaries similar in character 

 to the Pareora beds of the Broken River basin, it seems clear that these 

 Tertiaries once covered the floor of this Waimakariri basin more or less 

 completely, but have been removed almost entirely by erosive agents which 

 were especially active in that locality in Pleistocene times and later. The 

 Esk River limestone owes its preservation to being out of the sphere which 

 was especially subject to glaciation, since there are everywhere signs that 

 the intensity of ice-action fell off on the eastern side of the great mountain 

 valleys, especially where their heads do not reach as far back as the main 

 divide, but belong rather to the drier mountain region to the east. The 

 boundary of this area on the eastern .side is the great ridge of the Puketeraki 

 Mountains, whose steep western faces and even alignment suggest an origin 

 dependent on some great structural feature such as faulting. This would 

 be quite in keeping with the features exhibited by other basins, where the 

 eastern margin is determined by fault-lines while their western side exhibits 

 folding. 



The general results of this statement of the conditions governing the 

 formation of the Broken River and its associated basins are, — 



