Thomson. — The Gem Gravels of Kakanui. 



485 



of Kakanui Township. On the North Head it is found for 

 about half a mile on the sea-shore, forming low cliffs capped 

 with gravel, and generally forming a beach of marine denu- 

 dation for many feet seawards from the cliffs. Proceeding 

 northwards on the beach it is seen to be underlaid unconform- 

 ably by another volcanic breccia carrying no large crystals, 

 for convenience called " barren breccia." The latter forms 

 the cliffs for about three-quarters of a mile, and then gives way 

 to a conformably overlying very fine tuff, full of cleavage flakes 

 of biotite. The " barren breccia " in its uppermost layer is 

 fossiliferous, having apparently been covered with a coral reef. 

 The fine tuff is only 15 ft. thick, and is overlaid conformably 

 by a limestone which forms the cliffs on the beach for the next 

 half-mile. It is overlaid conformably by a glauconitic green- 

 sand, and the whole is covered unconformably by thick beds 

 of gravel and clay. 



Further north the limestone gives place, on the cliffs, to 

 the " mineral breccia," which underlies it conformably, and 

 this forms the cliffs for half a mile and then dips under the 

 more recent beds of clay and gravel which form the Awamoa 

 beach and stretch to Oamaru Cape. 



o Qzaxrry tvcJc. 



JTiRsid& 



I. Diagrammatic Section and Sketch, North Head, Kakanui. 



a. Mineral breccia, b. Barren breccia, c. Fine micaceous tuff. d. Lime- 

 stone, e. Greensand. /. Gravel, g. Quarry limestone. 



The " mineral breccia " is also exposed on the west side 

 of the hill forming the North Head, on cliffs near the Waiareka 

 River. Here its relations are not clearly seen, as there is a 

 slide between it and the " barren breccia " on the south, and 

 it is lost under clay to the north. There is also an exposure 

 of the " mineral breccia " about two miles north of Kakanui 

 in a road-cutting (not shown in map) ; it is overlaid conformably 

 by limestone. 



On the South Head there are two exposures of breccia 

 bearing the minerals, but their occurrence is somewhat dif- 

 ferent. On the cliffs exposed on the river-bank on the south 

 shore the following section occurs :— 



