Táhaka System.

This system covers a large extent of country in Collingwood County, and can be traced south, continuously through Mt. Arthur, page 199 Merino Mts., Lyell Mts., Brunner Mts., Victoria Mts., Werner Mts., and along the westerly base of the New Zealand Alps into Otágo, where it again expands considerably, and turning eastward with the anticlinal axis, covers the greater part of the interior of that province, reaching the sea in the neighbourhood of Dunedin. The centre of the secondary anticlinal fold in S. Canterbury (fig. 1, e) and the one in Marlborough (k) are also occupied by these rocks.

Fossils of the Baton-river Series have been found as far south as Reefton, and in addition Spirifera vespertilio and Homalonotus ex-pansus, Hector ^†; but beyond that the metamorphism gets more pronounced, and the rocks of the system pass altogether at the base into chlorite-schist and quartzose mica-schist, with occasional beds of graphite (Wánaka Series), and in the upper parts into phyllites with clay-slate and quartzite (Kakanúi Series). No calcareous rocks are known in the south.

The thickness of this system in Otágo cannot, I think, be less than 100,000 feet; but in the Nelson Province Dr. Hector estimates it at from 15,000 to 18,000 feet only.

The junction of the Tákaka with the underlying Manapoúri System can be studied in the Ríwaka Mountains, west of Tasman's Bay, and here Mr. S. H. Cox has shown a complete unconformity between the two ^‡ (fig. 2, b and c).

Fig. 2.—Digagrammatic Section from the West Coast of New Zealand to Tasman' Bay.

a. Granite.

b. Manapúori System (Ríwaka Series).

c. Tákaka System (c1 Mt. Arthur Series; c2 Aorere Series).

d. Maítai System.

f. Waípapa System.

g. Oamarú System

It is very remarkable that in the Province of Nelson, where there are several exposures of granite in connection with this system, and where the rocks are, in places, violently disturbed, metamorphic action has been much less than in Otágo, where the rocks lie nearly flat and no granitic areas occur. This militates much against Mr. Mallet's idea that the heat of metamorphism is due to crushing. On the other hand, the enormous thickness of the system in Otago and the gradual decrease of metamorphic action upward make it probable that, in this case, the metamorphism is due to the internal heat of the earth.