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Transactions. 



section from east to west passing through the highest point of the hill it 

 again exhibits an anticlinal structure, flanked on the east by a syncline 

 (fig. 5), which probably passes into a fault in a north-and-south direction, 

 so that the extreme north-eastern end of the hill is separated somewhat 



Cast/e Hill 





Fig 4. —Section along eastern face of Castle Hill from Whitewater Creek to Thomas 

 River. Distance, about 2 miles. Direction, S.-N. 1 , grey wacke ; 2a, sands, 

 greensands ; 26, marls, &c. ; 3, tuff beds ; 4, limestone ; 5, sands, sandy 

 clays, shales, and conglomerates — Pareora beds. 



from the rocks on the northern flank. This faulting is apparently attended 

 with a thinning-out of the beds, perhaps as a result of folding movements 

 which have resulted in either a pronounced distortion of the limestones 

 as suggested by McKay, or as an actual fault running almost parallel to 

 the line of the Thomas River towards the upper limestone gorge of the 

 Porter as suggested by Hutton. It is probable that both suggestions may 

 be partly correct, the undoubted fold grading into a fault. 



Hi If 



W. N.W. 



E.S.E. 



Fig. 5. — Section across Castle Hill. Distance, about 1 mile. Direction, W.N.W.-E.S.E. 

 1, greywacke ; 2a, sands, greensands; 26, marls, &c. ; 3, tuff beds ; 4, lime- 

 stone ; 5, sands, sandy clays, shales, and conglomerate; — -Pareora beds. 



In a small slip about half-way up the north-eastern face there is an 

 exposure of typical lower limestone exactly similar in lithological features 

 to that in the Porter River, and this is succeeded by tuff beds (25 ft.), which 

 pass up into a fossiliferous calcareous tuff with brachiopods, corals, and 

 fragments of molluscs, and overlying this is the upper bed of limestone 

 150 ft. thick. This is typically developed in the splendid monolithic blocks 

 which crown the hill, and in the fine eastern face. The stone was quarried 

 at one time for building purposes, and was in good repute throughout the 

 whole of Canterbury ; in fact, it was looked on as the best building-stone 

 that the province could produce. At the quarry itself it has a free, even- 

 grained texture, nearly white, and admirably suited for general building 

 purposes, its place being now taken by Oamaru and Mount Somers stone, 

 which are inferior in quality ; but the remoteness of the locality and the 

 difficulty of transport will always militate against its general use. 



On tracing the limestone south to the vicinity of the Whitewater Creek 

 it thins out considerably, so that the total thickness diminishes to about 

 40 ft. In the bed of the stream there occurs a mass of limestone, but it is 



