718 SUBANT ARCTIC ISLANDS OF NEW ZEALAND. [Physiography, Geology. 



Captain Hutton accepted the " elevation hypothesis " when accounting for the 

 glacier period in New Zealand, and when explaining the biological relationships of 

 the New Zealand fauna and flora,* but he was unaware of the former glaciation 

 of the subantarctic islands. If this hypothesis is correct, his case is greatly 

 strengthened, since, while he used the biological conditions of the off islands to 

 explain the glaciation of New Zealand, we may now use the fact of the extension of 

 the glacial conditions to explain their biological relations. If an elevation of the 

 Auckland Island group by at least 5,000 ft. is thus demanded, and this elevation 

 extended over the whole area south of New Zealand, it would be sufficient to connect 

 the Snares, Auckland Islands, Antipodes, the Bounty Islands, and perhaps Campbell 

 Island, with New Zealand. If it extended further south it would join on Macquarie 

 Island, and thus go far to explain the connection of New Zealand with a former 

 antarctic continent, 



STRATIGEAPHY AND PETROLOGY. 



The oldest rocks found in the Auckland Islands consist of masses of granite 

 and gabbro, which are overlaid by flows of trachyte and penetrated by dykes of 

 similar character, as well as by dykes of diabase and porphyrite. Then follows 

 a conglomerate containing fragments of these granites, gabbros, and trachytes, 

 and also of gneisses and granites of different type. A series of porphyrites 

 and diabases form the next group in order of time, although they may occur 

 before the conglomerate ; and the whole sequence is closed by vast outpourings 

 of basalt, of which the main mass of the group has been constructed. These 

 basalts are penetrated by a series of dykes of diabase and basic porphyrites which 

 sometimes approach augite - camptonites in composition and general character. 

 Disappointment Island is apparently composed of melaphyres and diabases, which 

 no doubt form part of the fourth series of the main group. The general sequence 

 may be expressed thus in tabular form : — 



(1.) Granites and gabbros, whose actual and relative age is undetermined. 



(2.) Trachytes — flows and dykes. 



(3.) Camp Cove conglomerate. 



(4.) Older basic series, with dykes of dolerite, diabase, and porphyrite. 



(5.) Younger basic series, with dykes of diabase and basic porphyrites. 



It is impossible in the present state of our knowledge to assign a definite age 

 to any of these series, but (2), (3), and (4) are almost certainly pre-Tertiary, and 

 (5) is almost certainly of middle or late Tertiary age. 



(1.) Plutonic Eocks. 



Granite. 



The exposure of granite on the Auckland Islands is of very limited extent, but 

 its existence in the group has been previously reported in Musgrave's account of his 

 adventures in this island, and also by Armstrong and Sir James Hector. The out- 

 crop occurs near the isthmus of Musgrave Peninsula, on the east side of Carnley 



* " Origin of the Flora and Fauna of New Zealand," Ann. & Mag. Nat. Hist., series v, vol. xv. 



