Park. — On the Geology of North Head, Waikouaiti. 427 



It is not assumed that the ejecta of each era was the result 

 of one stupendous outburst. On the contrary, the alternation 

 of fragmental matter and solid lava so often seen in the district 

 around Dunedin seems to justify the conclusion that in each 

 era there were alternating periods of quiescence and more or 

 less paroxysmal activity, each distinguished by some pecu- 

 liarity in the composition of its lavas and fragmental material. 



The conclusion that a cessation of volcanic activity occurred 

 after the earlier outbursts does not depend alone upon the 

 evidence furnished by the section at Waikouaiti North Head. 

 At several places within the Dunedin area there is seen a 

 series of aqueous deposits both underlain and overlain by 

 volcanic rocks. 



This sedimentary series consists of well-rounded gravels, 

 sands, and silts containing in places leaf-impressions, and in 

 others such an excess of carbonaceous matter as to pass mto 

 impure coal and oil-shale. 



At the oil-shale outcrops between Burns's and Williams's 

 Streams, at the source of the Waitati, the succession of rocks 

 in descending order is as follows : — 



1. Basic lava-How of great thickness. 

 /2. Oil-shale graduating into carbona- 



Ft. 



Probably 

 lacustrine 



ceous sandstone ... .. 18 



3. Volcanic tuff partially stratified ... 12 



4. Impure brown coal ... ... 3 



5. Volcanic tuff ... ... ... 12-15 



Marine ... 6. Caversham sandstone. 



The tuff underlying the oil-shale contains numerous frag- 

 ments of grey vesicular material resembling the pumice in the 

 leaf bed at Mount Cronin. 



In the Kaikorai Valley the Caversham sandstone is over- 

 lain by a series of beds of lacustrine origin, consisting of fine 

 grey silts, sands, clays, and gravels composed principally of 

 volcanic material. The lacustrine beds are overlain by a great 

 pile of volcanic rocks. 



The grey silts contain a large number of finely preserved 

 leaf-impressions, and in a collection of these made in 1901 

 Dr. Marshall identified species of oak, elm, birch or beech, 

 Magnolia, Piper, and Metrosiderosr' 



The Kaikorai section has a striking resemblance to that at 

 Waikouaiti North Head, and there seems to be no reason to 

 doubt that the leaf-bed series at Mount Cronin is the hori- 

 zontal equivalent of the Kaikorai leaf beds. 



In all that has been written about the geology of Dunedin 

 it is singular that the significance of the section exposed at Te 



* Trans. N.Z. Inst., vol. xxxiv., 1901, p. 586. 



