Uttley. — VoVc&nic Rocks of Oamaru. 117 



5. The Oamaru pillow-lavas, like similar rocks in other parts of the world, 

 owe their peculiar structure to eruption and solidification under submarine 

 conditions. 



6. These rocks, though similar in some respects to British Palaeozoic 

 pillow lavas, are clearly differentiated from them by their poverty in soda. 



7. The structural and lithological resemblances of the upper pillow-lava 

 at the lighthouse and the pillow-lava in Oamaru Creek are sufficiently strong 

 to justify the assertion that they are at the same horizon. The succession 

 of rocks at the latter place and at Hutchinson Quarry is similar from the 

 lava to the top of the Hutchinson Quarry greensand. At the breakwater 

 we get a clear succession of the beds below the lava down to the tuffs. At 

 the Rifle Butts we get a sequence from the Awamoa mudstone down to 

 the tufaceous rocks. Piecing the evidence together, it would seem that the 

 top of the thicker limestone at the Rifle Butts represents the horizon of the 

 upper pillow-lava, and it is probable that the rocks shown below these in 

 figs. 1 and 2 will be found equivalent. The beds are fossiliferous throughout, 

 and careful and more exhaustive collecting should enable this point to be 

 decided. 



8. The fossiliferous beds below the upper pillow-lava at the lighthouse 

 are not the equivalent of the fossiliferous beds at Hutchinson Quarry, as 

 asserted by former observers, but are separated from the latter by a con- 

 siderable thickness of lava, tufaceous beds, limestone, and " limestone 

 conglomerate." 



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