IV.—Geology.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 2, 1869, Unnumbered Page

IV.—Geology.

List Referred to. (The extinct species are marked in italics.) Muricidæ (14)—Murex, Murex sp. (?), Typhis, Triton 2 sp., Fusus 7 sp., Trophon, Pyrula. Buccindiæ (6)—Buccinum, Buccinum 2 sp., Cassidaria, Nassa, Ancillaria. Conidæ (3)—Conus, Pleurotoma, Mangelia. Volutidæ (5)—Voluta 2 sp., Marginella, Marginella 2 sp. (?) Cypræidæ (1)—Cyproea. Naticidæ (4)—Natica 2 sp., Polinices, Globulus, Sigaretus. Pyramidellidæ (1)—Chemnitzia. Cerithiadæ (2)—Cerithium, Struthiolaria 2 sp. Turritellidæ (2)—Turritella 2 sp. Litorinidæ (1)—Solarium. Turbinidæ (1)—Trochus. Calyptræidæ (1)—Calyptræa, Crepidula. Dentaliadæ (3)—Dentalium, Dentalium 2 sp. Tornatellidæ (1)—Tornatella. Bullidæ (2)—Cylichna 2 sp. Rhynchonellidæ (1)—Rhynchonella. Ostreidæ (5)—Placunomia, Lima, Limatula, Pecten 2 sp. Aviculidæ (3) Pinna, Avicula, Perna. Mytilidæ (1)—Modiola. Arcadæ (5)—Arca, Cucullæa, Pectunculus, Solenella, Limopsis 2 sp. Cardiadæ (1)—Cardium. Lucinidæ (1)—Lucina. Cyprinidæ (2)— Crassatella, Venericardia. Veneridæ (3)—Venus 2 sp., Artemis. Mactridæ (1)—Lutraria. Tellinidæ (1)—Tellina. Myacidæ (2)—Mya, Corbula.

I presume this formation has been generally considered to overlie immediately the Oamaru building stone. At one point near the south side of the Oamaru Cape Cliffs, just below where the hill slopes away southwardly, may be seen the “with clay” with its underlying rocks. At first sight it seems to be a horizontal bed, capped by a seam of yellow clay; but a closer inspection shows that there are hard seams, several inches thick, running through it, dipping to the south; and that these show the original planes of stratification, is evident, because the imbedded fragments of flat shells, and thin seams of shells, lie in parallel planes. Also, the same rocks form, at this place, outlying reefs, dipping in the same direction, having the soft parts eaten away by the action of the waves, so that the upper part of the clay and adjoining rocks (on which lies a single layer of hard water-worn limestone, say six inches to a foot in thickness), must have been worn to a level, and the upper portion of the clay altered in colour, after being tilted by the force of the volcanic outbursts which formed the Cape hills. Interposed between the “Blue clay” and Oamaru stone, is a layer of sand like that in Hutchinson's lime kiln, containing numbers of Terebratulæ, Pecten, Hutchinsonia, etc., and irregular masses of dislocated rock, altered, I suppose, by heat. On looking over the foregoing I think you may add to the previous list of fossils, one new species of Limopsis, and one new Struthiolaria. (List amended.) The Struthiolaria (of a genus you may remember peculiar to our shell province) is interesting, as showing a marked approach to the genus Aporrhais. Comparing it with S. strminea, the body is more slender, the mouth more expanded, and the outer lip, instead of having two slight rounded projections, has one claw-like expansion. A fine Turritella, of which you have at least one specimen from the Waitaki, attaining a circumference of about four and a half inches, is not uncommon, and I have one Scalaria (which seems common to this and the Oamaru stone) about four inches in circum-ference. It is singular that the only shell retaining any colour is a large Lima, of which genus I believe all the recent species are destitute of colour. Possibly, however, the colour has been induced by chemical action, during its long sojurn in the clay; and this shell was, perhaps, in its day and generation, of as pure a white as its descendants of our times. I have one valve of this Lima, measuring five inches in length. The list I sent you contained seventy-five genera, with the two now mentioned, seventy-seven, of which I believe fifty-one to be extinct, and twenty-six perhaps alive; but I have more confidence in the dissimilarity of the fifty-one, than in the similarity of the twenty-six; and I have a number of imperfect shells and fragments, evidently different from any we have found recent, but of which I have not yet been able to determine even the family; so I think it not unreasonable to suppose, that the proportion of extinct is understated above. Without presuming, of course, to speak positively, I cannot help a strong impression that these results indicate a much higher antiquity to this formation than has been hitherto assigned to it. As far as I have seen it noticed, it is put down as Pliocene, or Pleistocene* A series of fossils from this formation, now in the Dunedin Museum, was exhibited in the Geological Survey Collection, in the N. Z. Exhibition, 1865, as Eocene. See “Catalogue of N. Z. Exhibition,” p. 58; and “Juror's Reports,” p. 263.—ED.—a time I suppose when nearly the present disposition of land and water obtained; while if it has to be referred back to the Miocene, or possibly the Eocene, we must imagine a period when these islands bore only a rude general resemblance to our New Zealand of to-day.(?) Even on this spot, I think it can be shown, that when these

shells flourished, there was no “Oamaru Cape,” which now gives a friendly shelter to our coasting fleet; as it is also tolerably plain that a spacious harbour or inlet then existed, where the waters of the Waitangi now traverse an extensive agricultural district. The following, I think, to a common mind—perhaps not to a trained geological one—seems to bear further testimony to the age of these shells:— In various parts of this coast the face of an old sea-beach is seen, often elevated considerably above the present one, and supplying the shingle from which the present coast is formed. This is covered by many feet of silt. The inference surely is, that since this old beach was formed, we have had at least one considerable depression (to allow of the uniform deposition of such a depth of clay over many miles of surface) and one subsequent elevation. If, in our day, there is little or no sensible movement going on in this part of New Zealand, we may surely conclude that the two movements, referred to, represent a very lengthened period. Yet the fossil shells in this old beach seem precisely similar to those now living; then, how immensely old, by comparison, must this group of shells be, in which only a few bear any close resemblance to those we now find. As bearing on this, and because we often hear it assumed that the coast is rising, the following may be worthy of note:— At the mouth of the Awamoa, and, I believe, at various creeks on the coast, we find evidence of old Maori repasts, where moa bones (many of them broken, and the fractures still sharp, not waterworn) are associated with those of the seal, marine shells, such as Maoris still collect for food, chert flakes, etc., in a black soil, apparently a mixture of sand and charcoal. I believe those who have studied the matter consider that it is a long time since Maoris feasted on moa flesh, and that these particular deposits are amongst the earliest records of human life in these islands. Yet while exploring at this place with spade and pick, I was on two occasions “washed out of my diggings” by the sea at spring tide, showing that the deposit is now only slightly above high-water mark, while we may safely assume, that, if lower by only a foot or two, such a friable soil could not long withstand the violence of the sea on an exposed coast. While taking out some egg shells (moa) at this place, I found, at about twelve inches below the surface, a small bit of ivory resembling one half of a long squarish bead, split down the centre longitudinally. I am not aware of any hollow ivory tusk it could be made of, and it is difficult to conceive how the hole could be bored without the use of an iron tool. I shall enclose wax impressions, which may interest Mr. Mantell,—like showing him a nugget from his old diggings.* See Mantell, loc. cit. sup. Also “Trans. N. Z. Inst.,” Vol. i., p. 18.—ED.