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The Pamphlet Collection of Sir Robert Stout: Volume 65

Grouping of the Rocks

Grouping of the Rocks.

The geology of a district can be studied quite irrespective of any other part of the world. We can group its rocks by means of unconformities (stratigraphical and palæontological) into systems and series, and after having made out its geological history, we can compare it with that of other parts of the world by endeavouring to refer the systems and series to their probable equivalents in Europe. On the other hand, we may commence by trying to refer the rocks of the district to their European equivalents, and refrain from giving names to the local systems. The first plan has been adopted page 193 by Dr. von Haast and by myself; but Dr. Hector prefers the second for the larger groups, giving local names only to the series. Of course there is no real difference between the two methods, it is merely a question of nomenclature; but in a district so far from Europe as is New Zealand, the second plan must for many years be more or less uncertain, and constantly liable to change as our palæontological knowledge increases; and different geologists may call the same group of rocks by different names. The first plan is not open to this objection, and is, indeed, the same as that necessarily employed in Europe. As geological investigation advances, other systems and series may have to be added; but those that are once generally accepted remain for all time.

It is on this first plan, therefore, that I propose to group our rocks; but as the method has as yet been applied only to separate districts, many of the names used are synonymous, and it becomes necessary to introduce a modified scheme applicable to the whole of New Zealand. This I have attempted to do, and will state the considerations that have guided me in drawing it up. In the first place the names of the systems and series should be geographical, and taken from the most typical districts, where the rocks are best developed and contain the most fossils; but names already in pretty general use should not be altered, although some other locality might logically furnish a better name. In the second place the names of the systems and of the series should be of Maori origin, in order that they may be characteristic, and may convey to geologists in all parts of the world the idea that they belong to Now Zealand. In the third place, priority in nomenclature should be allowed considerable weight. The following Table shows the arrangement I propose. The right-hand column gives the probable European equivalent, that is the probable age; but it must be understood that this is merely provisional and constantly liable to change. I have introduced among the systems two new names—Hokanúi and Takaka, each of which represents a natural group of rocks to which no collective name has previously been applied; and yet names are necessary, for in many parts of New Zealand we can refer rocks to one or other of these systems, and yet, in the absence of fossils, it is impossible to say to which series they belong. The grouping of the Tertiary rocks is founded on that given in a former communication to the Society*, but it includes modifications subsequently made.

page 194
Systems. Series. Probable age. Recent. Alluvia and Æolian deposits with Moabones and traces of Man. Recent. Pleistocene. Raised-beaches and Shore-deposits. Peat-mosses with Moa-bones. Pleistocene. Wanganúi System. Kéreru Series. Ormond Series. Pétane Series. Pútiki Series. Older Glacial deposits. Lignites of Otágo, Mánukau, &c. Newer Pliocene. Older Pliocene. Pareóra System, Awatére Series. Kaníeri Series. Táwhiti Series. Ahuríri Scries. Waitemáta Series. Brown Coal of Pomaháka, &c. Miocene. Oamarú System. Mt. Brown Series. Aotéa Series. Otótara Series. Turanganúi Series. Goals of Waíkato, Kaitángata, &c. Oligocene. Waípara System. Amúri Series. Awanúi Series (?). Matakéa Series. Coals of Greymouth, Pákawau, &c. Upper Cretaceous. Hokanúi Mataúra Series = Putatáka Series. Flaghill Series. Catlin's River Series. Bastion Series. Lower Jurassic. System. Wairóa Series = Otapíri Series Oréti Series Triassic. Kaihíku Series. Maítai System. Rimutáka Series. Te Anau Series (?). Carboniferous. Tákaka Baton-river Series= Kakanúi Series. Waiháo Series. Silurian. System, Aorere Series ... Mt. Arthur Series = wánaka Series. Ordovician. ManapoúrSystem. Ríwaka Series. Archæan.

Table of Sedimentary Formations in New Zealand.

* "Synopsis of the younger Formations of New Zealand." Quart. Journ. Geol. Soc. vol. xxix. p. 372.