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Volume 18, 1885
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Art LV.—On the Geology of Scinde Island.

By Captain F. W. Hutton, F.G.S.

[Read before the Philosophical Institute of Canterbury, 2nd July, 1885.]

Plate XIII., fig. 6.

The first notice of the geology of the isolated, rocky bluff called “Scinde Island,” on which the Town of Napier is partly built, is a section by Mr. Triphook, published by Dr. von Hochstetter in the “Reise der Novara” (Geologishert, Theil I., p. 2), but Dr. von Hochstetter did not himself visit the locality. This section is from Cape Kidnappers to Petane, and shows the Scinde Island rocks as an outlier of the Petane beds, which lie four or five miles to the north. Dr. von Hochstetter called them the “Hawke's Bay Series”—“limestones, sandstones, and claymarls replete with fossils: Pecten triphooki, Zittel; Venus, Mytilus, Pectunculus, Trochita,” etc., and considered them as belonging to the younger of the two systems into which he divided our tertiary rocks.

In 1871 Dr. Hector reported on the district, and agreed with Mr. Triphook, saying that the Scinde Island beds belonged to the upper part of the formation, and occupied the centre of a syncline from Cape Kidnappers to Pohui, which lies on the road from Napier to Lake Taupo.*

Among the tertiary fossils in the Colonial Museum at Wellington, which I examined in 1872, were some from “Napier and Cape Kidnappers,”†† and these I referred to the “Ahuriri Formation” (since called the Ahuriri series of the Pareora system), making them older than the Wanganui Formation, (“Cat. Tert. Moll. and Echin. of N.Z.,” p. 8,) which at that time was only known on the west coast of Wellington. There were no fossils from the Petane beds in the Museum, and, consequently, no opinion was expressed as to the age of that series.

[Footnote] * “Reports Geol. Survey.” 1870–71, p. 159.

[Footnote] † “Catalogue of the Colonial Museum,” 1870, p. 180.—“Limestones and clay-marls exposed in the cliffs around Scinde Island, and along the coast. The same formation is general throughout the east part of Hawke's Bay.”

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On the 27th November, 1876, Mr. S. Percy Smith read a paper to the Auckland Institute called a “Sketch of the Geology of the Northern Portion of Hawke's Bay,” (“Trans. N.Z. Inst.,” vol. ix., p. 565,) in which he makes the sandstone of Scinde Island and the Napier limestone to be the same as the Petane beds. He also gives a list of fossils from the different beds.

In March, 1876, Mr. S. H. Cox examined the country,* and stated that the Napier limestone underlaid the Petane beds at Scinde Island, and that it was the equivalent of the Pohui limestone at Te Waka, on the Taupo Road. He says: “At Scinde Island, Napier, where the typical development of these beds [Napier limestone, etc.,] occur, they are forming a low anticline, dipping on the sea-face, S. 10°, but on the harbour side N. W. 25°” (l.c., p. 100). He considered that all the tertiary beds belonged to one series, without any uncomformity between them.

Dr. Hector, in his Progress Report for the same year, says that the fossils from the Petane series “seem to place them in the same horizon as the Upper Wanganui beds” (l.c., p. viii.), but he considered the Napier limestone to be the same as the Petane limestone.

In the early part of 1877, Mr. A. McKay examined the district and reported that certain marls and pumice sands, which underlie the limestone at Puketapu (Petane limestone) form the lowest beds exposed on the south-west side of Scinde Island: that “they dip to the N.E” bringing the limestones to the sea level at the north end of Shakespeare Road, but are found at a higher level in the Bluff along the sea beach,” (“Rep. Geol. Exp.,” 1856–7, p. 84,) thus forming a syncline. In his Progress Report for the year, Dr. Hector remarks that “the general results of this examination are that the Scinde Island limestone (= Napier limestone) is shown to be the highest marine bed in the district, being separated from the limestones of the Puketoi Range and Manawatu Gorge by a great series of fossiliferous sands and clays, estimated in the district west of Napier to be not less than 2,000 feet thick.” (l.c., p. 11.)

In August, 1878, Mr. A. McKay again visited the district south of Napier, and ascertained that the “pumice sands and lignite series” (i.e. the Petane series) rested unconformably on the Te Aute limestone (i.e. the Ahuriri series) at Mount Vernon, near Waipukurau (“Rep. Geol. Explorations,” 1878–79, p. 72); and Dr. Hector remarks, in his Progress Report, that “as the former series (Petane series) is closed by the Scinde Island beds, the rocks at the town of Napier do not belong to the same horizon as the Te Aute limestone.” (l.c., p. 26.)

[Footnote] * “Rep. Geol. Exp.,” 1874–76, p. 96. This report was not published until 1877, after Mr. Percy Smith's paper had been read; so that each is independent of the other.

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It thus appears that all the observers, except Mr. Cox, place the Napier or Scinde Island limestone in the upper part of the Wanganui system, which is directly opposed to the conclusion drawn from the published lists of fossils. The stratigraphical and palæontological evidence seemed therefore to clash, and I gladly availed myself of an opportunity that occurred last January of visiting Scinde Island to try to clear up the difficulty. This, with the able assistance of Mr. A. Hamilton, of Petane, and Mr. H. T. Hill, of Napier, I think I have accomplished.

The result of my examination is to show that the northern end of the island is formed by the Petane series. This series rests unconformably on the Scinde Island limestone, which forms, with the underlying sandstone, all the southern part of the island, as shown in the accompanying section. (Pl. XIII., fig. 6.)

Collections of fossils from here, and from Petane, prove the accuracy of Dr. Hector's opinion that the Petane beds are the equivalents of the Wanganui beds. The fossils from the Scinde Island limestone, however, show that it is the equivalent of the Te Aute limestone, which is the same as the Pohue limestone of Te Waka.

Ahuriri Series.

This series forms the main part of the island, from the southern end to beyond Curling's Gully on the eastern, and as far as the Taradale Bridge on the western side. It consists of the following rocks, in descending order:—

3.

White earthy limestone, with bands of bluish-grey compact limestone with shells.
2.

Yellowish sandstone, with irregular layers of compact limestone, passing downwards into—
1.

Yellowish sandstone, glauconitic in places. The lowest bed seen.

All three pass gradually into each other.

On the south-east side of the island this series dips about S.E. 5°. To the northward, it gets horizontal, and then dips to the north-west. On the east side, at Curling's Gully, the dip is N.W. 20°; and on the west side, at Taradale Bridge, it is N.N.W. 10°. The limestone is quarried in many places. Fossils are generally in the form of casts, and are most abundant in the upper parts, especially in Curling's Gully and Milton Road. They are not, however, altogether absent in the lower sandstones. I noticed the following:—

1.

Siphonalia mandarina, Duclos. (?)

* 2. Trochita neozelanica, Lesson.
3.

Crepidula monoxyla, Lesson.

[Footnote] *Abundant.

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* 4. Crepidula incurva, Zittel.
5.

Panopæa neozelanica, Quoy. (?)
6.

Mactra discors, Gray. (?)
7.

Hemimactra notata, Hutton. (?)
8.

Hemimactra elongata, Quoy. (?)
9.

Lutraria solida, Hutton.
10.

Paphia neozelanica, Chemnitz.
11.

Venus strutchburyi, Gray.
12.

Venus sulcata, Hutton.
13.

Dosinia subrosea, Gray.

* 14. Cardita australis, Lamarck.

* 15. Pectunculus laticostatus, Quoy.

* 16. Mytilus magellanicus, Lamarck.
17.

Modiola australis, Gray.

* 18. Pecten triphooki, Zittel.
19.

Pecten accrementus, Hutton.
20.

Pecten chathamensis, Hutton.
21.

Pecten neozelanica, Gray.

* 22. Pecten burnetti, Zittel.

* 23. Ostrea nelsoniana, Zittel.
24.

Waldheimia patagonica, Sowb.

All these species are found in rocks belonging to the Pareora system in other parts of New Zealand, except Hemimactra notata and Mytilus magellanicus, and the first of these is doubtfully identified from casts only. The following are characteristic Pareora fossils:—Crepidula incurva, Pecten triphooki, Pecten accrementus, Pecten chathamensis, Pecten burnetti, and Waldheimia patagonica. The last species ranges into the Oamaru system, but the other five are confined to the Pareora system. Of the 24 species enumerated, no less than 15, or 61 per cent., are recent. But this percentage of species is probably too large, as several of the fossils have been doubtfully referred to living species from casts alone, and they are mostly Lamellibranchiata, which have a longer specific life than Gastropoda. Future research will, no doubt, reduce the proportion of living species.

Petane Series.

This series occupies the north-east corner of the island. The unconformity between it and the underlying Scinde Island limestone is very apparent on the eastern shore, opposite the Spit. The unconformity is not so clear on the western side, owing to the large accumulations of the overlying brick-earth, or loam.

The series consists of the following:—

2.

Shelly limestone, formed by comminuted shells, resting on—
1.

Soft sandstone of a yellow, grey, or brown colour.

[Footnote] *Abundant.

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The limestone (b in the section) occupies very little of the surface, as it is covered over with the brick-earth. It can, however, be seen at the top of the cliffs at the north end of the island, and again a little north of Curling's Gully, where it is separated from the Scinde Island limestone by the sandstone (c in the section). This latter forms the base of the cliffs all along the north side, from near the Taradale Bridge to beyond Battery Point. Although I looked carefully, I could find no trace of the pumice beds said by Mr. McKay to underlie it.

The following is a list of the fossils we collected from these rocks:—

1.

Amphibola avellana, Chemnitz.
2.

Ancillaria australis, Sowb.
3.

Voluta pacifica, Lamarck.
4.

Siphonalia mandarina, Duclos.
5.

Cerithidea bicarinata, Gray.
6.

Cerithidea tricarinata, Hutton.
7.

Trochita neozelanica, Lesson.
8.

Crepidula monoxyla, Lesson.
9.

Turritella rosea, Quoy.
10.

Turritella tricincta, Hutton.
11.

Scalaria zelebori, Frauenfeld.
12.

Turbo smaragdus, Martyn.
13.

Rotella neozelanica, Hombron.
14.

Dentalium nanum, Hutton.
15.

Corbula erythrodon, Lamarck.
16.

Hemimactra notata, Hutton.
17.

Lutraria solida, Hutton.
18.

Zenatia acinaces, Quoy.
19.

Paphia neozelanica, Chemnitz.
20.

Venus stutchburyi, Gray.
21.

Venus meridionalis, Sowerby.
22.

Venus sulcata, Hutton.
23.

Venus mesodesma, Quoy.
24.

Dosinia grayi, Zittel.
25.

Tapes intermedia, Quoy.
26.

Cardium striatulum, Sowb.
27.

Loripes concinna, Hutton.
28.

Cardita australis, Lamarck.
29.

Pectunculus laticostatus, Quoy.
30.

Pectunculus striatularis, Lamarck.
31.

Mytilus magellanicus, Lamarck.
32.

Mytilus latus, Chemnitz.
33.

Modiola australis, Gray.
34.

Pinna neozelanica, Gray.
35.

Lima bullata, Born.
36.

Pecten neozelanicus, Gray.
37.

Pecten radiatus, Hutton.
– 332 –
38.

Pecten semiplicatus, Hutton.
39.

Pecten convexus, Quoy.
40.

Pecten laticostatus, Gray.
41.

Anomia alectus, Gray.
42.

Ostrea edulis, Linneus.
43.

Waldheimia ovalis, Hutton.
44.

Terebratella rubicunda, Solander.
45.

Rhynchonella nigricans, Sowb.

Of these, Dentalium nanum is at present only known from the Wanganui system; while Amphibola avellana, Cerithidea bicarinata, C. tricincta, Turbo smaragdus, Corbula erythrodon, Pectunculus striatularis, Pecten radiatus, and Mytilus latus have not yet been found in the Pareora system. Of the 45 species enumerated, 38, or 84 per cent., are recent. A small rolled fragment of Pecten triphooki was also found, but it probably came out of the Scinde Island limestone. However, I found a broken and rolled specimen of this species at Moteo, near Puketapu, which possibly had not been derived from any older rocks.

Brick-earth.

This formation forms the top of most of the hills, and lies quite unconformably on both the Ahuriri and the Petane series. It descends to the sea level on the east side of the island, in a valley a little south of Battery Point (see section), and also in two or three other places on the west side. It is a reddish-brown sandy clay, or loam, often showing the “capillary structure” of the so-called Loëss of Banks Peninsula; from which, however, it can be distinguished by its darker colour. I saw pumice in it in two places. One on a hill not far from the Hospital. The other in the valley just mentioned, south of Battery Point. In the latter place a considerable layer of pumice sand is seen on the northern slope of the valley, overlain by the brick-earth. In the other locality, small fragments of pumice are scattered through the brick-earth. At Battery Point a thin bed of shingle lies at the base of the brick-earth, but I saw no shingle at the south end of the island.

This loam bed is used for making bricks in Napier. It is also found in many places north of Napier, and is especially conspicuous on the hills near Puketapu.*

At the south-west end of the Bluff, at the sea level, below the limestone quarry worked by the prisoners, is a bed of clay containing fragments of rock, in which Mr. Hamilton informs me he has found moa bones. This clay may be of the same age as the brick-earth, or it may be younger. Probably the latter is the case, but I could not satisfy myself on this point.

[Footnote] * This is probably the “light-grey sandy marls,” mentioned by Mr. McKay as seen on the road between Puketapu and Taradale (“Geol. Reports,” 1876–77, p. 84); but it does not underlie “the limestone capping the hills to the north,” as Mr. McKay appears to think; and it is not marly.

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