Vol. 70.] LAVAS AT THE -NORTH HEAD, OTAGO HABBOUB. :>^7 



21. Trachydolerite 1 

 20. Basalt 



Thickness in feet, 



• wn 400 yards west . 30 

 6 





Tuff 



10 



19. Basalt . . 





18. Basalt .. 



Tuft- 



8 



4 





Tuff 



9 



17. Basalt . . 



7 





Tuff 



8 



16. Basalt .. 





15. Basalt .. 



Tuft- 



12 



25 



14. : Logan's 

 13. Kaiweki 

 12. Basalt .. 



Tuff 

 Point 

 Tuff 

 te 

 Tuft- 

 Tuff 



50 



: Phonolite 120 



10 



30 



20 



8 



20 



11. Basalt .. 



6 



10. Basalt .. 

 9. Basalt .. 

 8. Basalt .. 

 7. Basalt .. 



Tuft- 

 Tuff 



Tuff 

 Tuff 



13 



.10 



4 



10 



10 



2') 



15 



14 





Tuff 



6 



6. Basalt .. 



9 



5. Basalt .. 

 4. Basalt .. 



Tuft- 

 Tuff 



15 



5 



10 



3 





Tuft- 



10 



3. Basalt .. 



10 





Tuff 



3 



8 



2. Phonoliti 



20 





Tuff 



60 



1. Trachyte 30 



In this series the lavas have a total thickness of 422 feet, and of 

 this the basalts are represented by 192 feet, the phonolites by ISO 

 feet, and the porphyritic rock (which is of the same nature as the 

 kaiwekite of my former paper) accounts for a thickness of 50 feet 

 of rock only. As already stated, the amount of the rocks in the 

 section cannot reasonably be taken as an indication of the relative 

 quantity of the different types of lava that actually issued from 

 the crater of the volcano, for the section is merely composed of 

 those lavas that happened to How down one of the sides of the cone. 

 It does, however, appear that the basic lavas are in this instance 

 much thinner than those that have a more acid and alkaline 

 character. In all cases the great thickness of the tuff's and scorias 

 clearly indicates that the orifice from which the lavas issued was; 

 comparatively close to the locality where the section is exposed. 



