GEOLOGY OF NEW ZEALAND. A47 
dykes of trachyte. The first and second of these periods are quite 
evident, the proofs of the third are not so clear. 
In the North Island the trachytes of Hicks Bay, near Hast Cape, 
are distinctly overlaid by beds of the Tawhiti series, and they may, 
therefore, belong to the Oamaru system. 
Pareora system.—In the South Island, basalts and tuffs are inter- 
bedded with rocks of this system at’ Mount Cookson, north of, the 
Hurunui Plains, and the basalts of Moeraki Peninsula are clearly seen 
to overlie a ‘clay belonging to the system. The ,volcanic rocks of 
Timaru may also probably be placed here. No trace ofa scoria cone, 
nor of a well-defined crater exists anywhere in the South Island, but 
fine examples of calderas and barrancos are seen in Banks Peninsula. 
All the volcanic rocks—even the highest, 3,000 feet—appear to have 
suffered from marine denudation. In the North Island, volcanic ashes 
and andesite breccias are found associated with the Waitamata series, 
near Auckland, and the trachytes of Whangarei Heads, Great Barrier 
Island, and Coromandel are probably of the same age. From the 
trachyte tuffs of the two latter localities, Dr. Hochstetter obtained fossil 
wood of Podocarpium dacrydioides (Unger). And from the much- 
decomposed basaltic rocks behind Drury he also obtained wood of Nicolia 
zealandica (Unger), which was also found in the Pareora gravels of 
Moutere Hills, near Nelson. On the Great Barrier the trachyte cone 
of Ahumaira, 1,500 feet high, still retains a well-marked crater. The 
andesites and propylites of the Thames goldfields may be of the same 
age, or they may perhaps date back to the Oamaru system. A piece of 
carbonized wood impregnated with iron pyrites, but shewing plainly 
annual rings of growth, was found in the gold-bearing propylites in the 
Maid of England claim. 
There is no trace of volcanic action having taken place in the 
Wanganui system or later, in the South Island. But in the North 
Island, on the western side of the main range, volcanic eruptions on a 
large scale occurred from the commencement of the Pareora system, and 
are even now not quite extinct. At Mount Egmont the first eruptions, 
perhaps of Pareora date, were trachytic, containing both sanidine and 
oligoclase, and these were succeeded by dolerites and basalts. The base 
of Ruapehu and of Tongariro appear to be trachyte, but here the later 
eruptions have been rhyolites and pumice. These appear to have 
commenced during the formation of the upper parts of the Wanganui 
system (Kereru and Petane series) for no pumice occurs in the lower 
beds. These rhyolites are extensively developed round Lake Taupo, 
and in the Hot Lake district. From fragments washed down the 
River Thames, it appears that these are later than the dolerites of the 
Cape Colville peninsula. Around Auckland, and at the Bay of Islands, 
basalts were the only lavas erupted. Obsidian occurs in many places, 
and is particularly plentiful on Mayor Island, in the Bay of Plenty. 
In the neighbourhood of Auckland many scoria cones occur, with well- 
marked craters, some of them at very slight elevations. These are 
younger than the plastic clays round Manukau Harbour, and have of 
course never undergone marine denudation. A _ finely-laminated 
rhyolite is found at Totara, on the east shore of Lake Taupo. We have 
no glassy basaltic lava streams as in the Sandwich and Friendly Islands. 
Numerous other interesting minerals of volconic origin have been 
