Maítai System.

This system is found in the South Island, flanking the Takaka System on both sides of the main anticlinal (a, fig. 1), except in Westland, where it has been almost entirely removed. In the North Island it forms the chief part of the main range from Wellington to East Cape (Rimutáka Series), as well as most of the outcrops of old sedimentary rocks in the Province of Auckland. The rocks are chiefly argillites, red and black slates, and grey and green sandstones, with occasional beds of limestone in the South Island. Thick masses of greenstone-ash are found interbedded with the slates and sandstones in many places in New Zealand, but these rocks appear to be local.

The thickness is estimated by Dr. Hector at from 7,000 to 10,000 feet; but it is very difficult to form an opinion, as the stratification is often obscure.

That an unconformity exists between this and the Tákaka System page 201 is evident. In Nelson it has been shown to rest indifferently on the Aorerc and the Mt. Arthur Series ^*, the Baton-river Series being absent (fig. 2, d). In Westland, Mr. Cox describes these rocks as quite unconformable to the schists ^†; and at Reefton they have been shown to be unconformable to the Baton-river Series (= Reefton Scries) by Dr. Hector, Mr. Cox, and Mr. McKay. At the Tapanúi Mts. in Otágo, the system rests partly on the Wánaka, and partly on the Kakanúi Series, while in the West-coast Sounds it appears to rest upon the Manapoúri System. But notwithstanding this unconformity, it is by no means easy to draw the line between this and the Tákaka System in Otágo; for the metamorphic action has passed upwards through both, assimilating to some extent along the boundary the rocks of each system.

In consequence of the rocks being generally unfossiliferous, it has not yet been found possible to break up this system into distinct scries. According to Dr. Hector, the following fossils occur in limestone at the Dun Mountain, near the base of the system:—Spirifera bisulcati, Spirifera glabra, Productus brachythœrus, Cyathophyllum and Cyathocrinus. In the upper part of the system the only fossils known are the tubes of two or more species of Tubicolous Annelides, perhaps Cornulites^‡

The Rimutáka Series of the North Island no doubt belongs to the Maítai System. The Te Anau Series of Dr. Hector is now considered by the Geological Survey as forming the base of the Maítai System, but formerly it was placed at the base of the Hokanúi System^§. It is said to consist of "an enormous thickness of greenstone breccias, aphanite slates, and diorite sandstones, with great contemporaneous floes and dykes of diorite, serpentine, syenites, and felsite"^‖; and it appears to me to be merely the igneous rocks belonging to the system, and not to represent any particular horizon. I say this, however, with much hesitation, because Mr. S. H. Cox, to whose opinion I attach great weight, differs from me on this point and agrees with Dr. Hector.

Remarkable beds of manganese ore, generally associated with red jasperoid slates, are found in several places in the Auckland Province and also near Wellington. In many respects these rocks remind one of the deposits now being formed in the deeper parts of the Atlantic and Pacific Oceans, and the absence of fossils strengthens the impresssion.

This system is the same as my "Kaikoura formation." The "Westland formation," and the lower part of the "Mount Torlesse formation" of Dr. von Haast also belong to it. The rocks called "Maítai slates" by Dr. von Hochstetter are seen in the neighbourhood of Nelson to overlie rocks containing Monotis belonging to the Wairóa Series; and in addition to this, Dr. Hector collected from

^* Cox, Reports Geological Survey, 1881, p. 47. Up. Devonian, a.

^† Reports Geological Survey, 1874-76, p. 68, and sections,

^‡ See McKay, Rep. Geol. Surv. 1879-80, p. 90.

^§ Reports of Geological Survey, 1876-7, p. v.

^‖ 'Handbook of New Zealand,' 1883, p. 36.

page 202 them, in 1866, fossils which were said to be Inoceramus^*. For these reasons I have, in my report on the Geology of Otágo (1875), associated Dr. Hochstetter's Maítai slates with the Wairoa Series; and Dr. Hector in 1877 considered them to be the same as the Kaihíku Series of the Nuggets and Mt. Potts ^†. But on the other hand these slates resemble in lithological character those found in other parts of New Zealand underlying the Hokanúi System; and there is therefore some doubt as to the true position of the Maítai slates. Consequently I should have preferred to retain my namo of " Kaikoura " for this system; but the term Maítai has been largely used by the Officers of the Survey for the present group of rocks, and I do not wish to destroy this approach to uniformity by insisting on the desirability of employing some other name. I am the more ready to do so, as I think it probable that the superior position of the Maítai slates to the Wairóa Series near Nelson may be due to inversion,^‡ and that the supposed Inoceromus may belong to some other genus of the same family.