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Volume 52, 1920
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Art. XX.—The Tertiary Rocks near Wanganui.

[Read before the Wanganui Philosophical Society, 3rd December, 1919; received by Editor, 31st December, 1919; issued separately, 10th June, 1920.]

The marine strata that occur in the neighbourhood of Wanganui have long been the subject of geological inquiry and research. As developed along the coast-line they are richly fossiliferous almost throughout their extent, and the fossils that they contain are so closely related to the Recent molluscan fauna that the rocks have always been referred to the higher divisions of the Tertiary era. A résumé of the earlier work that had been published on these sediments was given by Hutton (1886, p. 338), and it is in general unnecessary to refer to it here. In that paper also Hutton gave for the first time a fairly complete list of the mollusca that had been collected from the Wanganui system up to that date. The list, however, contains also a number of species that had been found in the strata at Matapiro and Petane, in Hawke's Bay, which were considered by Hutton to be of equivalent geological age.

In his Wanganui system Hutton included the blue clays at Castlecliff and the blue clays at Patea, but he makes no reference to the rocks that outcrop on the coast between those places—the mouth of the Wanganui River and that of the Patea River.

A fuller list, but based upon the same principles and containing descriptions of a number of additional species, was published by Hutton subsequently (1893, p. 35 et seq.).

In these papers Hutton rarely makes any statement as to the actual Wanganui locality at which the various species were found. For that reason none of his lists can be utilized in any statement of the species that occur in the beds at Castlecliff and elsewhere along the coast. This is the more regrettable because many of the new species that were described in the Macleay Memorial Volume were found by Drew in the marine cliffs somewhere to the north of Castlecliff.

Hutton (1886, p. 337) took this course deliberately, for he says, “In order to save space I have not thought it necessary to give separate lists of the fossils from each locality, but have contented myself with one list of all the species that have been found in the Wanganui system,” but the work that has been done “will enable local geologists to fill in the details.” This additional work has not been done up to the present time, and the details that have to be filled in are so numerous that much time must elapse before anything approaching a complete result is achieved.

Park (1887) examined all the Wanganui and west-coast district for the Geological Survey, and in his report there are lists of fossils that he collected from the various strata that crop out on the coast-line and on the banks of the Wanganui River, as well as a number of other adjacent localities. The lists that he gives are, however, far from complete, though they reveal the occurrence of a large number of extinct species, such as Pecten triphooki, Pecten semiplicatus, Ostrea ingens, Cardium spatiosum, and Perna sp., several of which were regarded by Hutton as characteristic of his Pareora system, of Upper Miocene age.

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In 1916 Thomson proposed to divide the rocks exposed on the Wanganui coast-line into the Castlecliffian and Waitotaran series. This proposal, however, was not based on any further work, but merely on a consideration of Park's work and of the lists of fossils that he had recorded.

Murdoch (1900, p. 216) described further species that had been collected by himself and others from the blue clays in the Castlecliff area.

All of the strata on the coast-line north of Wanganui, as far at least as Patea, were placed by Hutton (1885, p. 211) in the Pliocene system. Hector (1886, p. 48) placed the strata partly in the Upper Miocene. Park (1887, p. 57) placed the beds near Wanganui in the Upper Pliocene, those at Nukumaru in the Lower Pliocene, and those between Waitotara and Patea in the Upper Miocene.

The present work was undertaken partly to discover the thickness of the strata exposed on the coast-line, and partly to find out as accurately as possible the extent to which the fauna changed as the depth in the strata, and therefore the geological age, increased. At first the intention was to collect the fossils in every stratum in which they could be found, and to make a separate list of the fauna in every case. The great number of fossil-bearing strata soon showed that such a project was impracticable, and that for the present purpose it was also undesirable, for each single stratum contains a small fauna only. If the fauna of each stratum were taken separately there would result a very large number of lists, and the comparison of these would lead to much confusion. For these reasons four different collecting localities have been chosen, and in each instance a thickness of about 500 ft. of sediment has been searched carefully, and as complete a collection as possible has been made from it. The lists that have been made cannot in general be regarded as in any way exhaustive, but in nearly every instance several visits have been made by two collectors in company. The Castlecliff locality has probably been almost completely collected, for much time has been spent in the study of the strata there, because it is most accessible. The late S. H. Drew obtained a large number of fossils there, and one of us has collected in these strata for a number of years, and of late times it is only rarely that any additions have been made to previous lists.

The localities that have been chosen as suitable for the comparison of faunas are as follows:—

(1.) Castlecliff.—A thickness of about 500 ft. of strata, commencing at the southernmost end of the sea-cliffs and ending about a mile and a half from the mouth of the Wanganui River. Nearly every stratum in this thickness is fossil-bearing. Almost all of the strata consist of a fine but hard blue clay—the so-called “papa.” The fineness and general nature of this material, as well as the mollusca that it contains, give the impression that the material was deposited on the floor of a sea that was not less than 50 fathoms in depth in this locality. As the strata are followed to the north and rise in the cliffs the material becomes a little coarser, and often changes to a micaceous sand before it works out at the top of the cliff. This apparently indicates that the water became shallower in the northern part of the district. This conclusion is supported by the nature of the fossil mollusca which have been found in the sandy facies of the strata.

(2.) Kai Iwi.—This locality is five miles to the north of the previous one. The rocks which extend about a mile to the south of the Kai Iwi Stream form the source of the collections classified under this name. The material is almost entirely blue clay of a fine unctuous nature. The collection that has been made is less complete than those made in the other localities.

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(3.) Nukumaru Beach.—This locality is six miles to the north of Kai Iwi, and extends over a distance of one mile to the south of the boat-landing. The strata here are of a much coarser grain and are highly micaceous. In some of the strata there are pebbly bands. The pebbles are formed of extremely hard submetamorphic sandstones, or greywackes, often penetrated by quartz veins. Many of them are of a green tint. Much of the fossiliferous material in this locality is of a concretionary nature.

(4.) Waipipi Beach.—This is nine miles north of Nukumaru. The strata here consist of a stiff and fine blue clay, with occasional bands of fine micaceous sandy matter. It is mainly in these bands that the fossils are found. The best localities are directly north of the mouth of the Waipipi Stream and on a projecting headland three-quarters of a mile farther to the north. Sometimes as the sand drifts with changing winds and tides very fine fossils are exposed above low-tide level between these two localities.

It may be said definitely that lithologically the strata are of the same general nature throughout. A bluish-grey fine-grained sediment is the ordinary material. This in places becomes sandy, especially between Kai Iwi and Nukumaru, where there is much false bedding, due apparently to rough-weather and tidal scouring, for there does not appear to be any actual beach formation. Sometimes the fossiliferous bands have an extremely marked concretionary nature, and then the rock becomes a hard arenaceous limestone; but this is always a shoal-water rock, and it generally contains a number of small pebbles. This is the nature of the Nukumaru limestone, which is really a shell conglomerate. This hard rock fronts the coast for a distance of some three miles north of Nukumaru Beach.

The strata always strike to the east of north. The most northerly strike is N. 27° E., at the mouth of the Waipipi Stream, and the most easterly N. 85° E., near the mouth of the Kai Iwi Stream. The average throughout the whole distance is considered to be N. 70° E. The dip is always to the south-east, and its amount is small throughout—never more than 6° and never less than 2½°. The average is considered to be a little over 4°.

No dislocations of any importance have been seen in the strata, though the sea-cliffs, which are continuous from Castlecliff to three miles north of Nukumaru, have been closely inspected throughout the whole distance. There are some small faults, but they always have a slight throw only. Nothing of the nature of an important unconformity can be seen. Three miles to the north of Kai Iwi an old land-surface can be seen distinctly in the stratification. The evidence of this is found in a stratum of beach-worn pebbles, a carbonaceous stratum with roots penetrating the blue clay beneath, and a number of molluscan bores penetrating it. There is, however, no discordance in the stratification, and no species of mollusca were found in the strata lying just above the old land-surface different from those that were found beneath it. It is, however, noticeable that Crepidula gregaria was far more abundant in the rocks below than in those above this old surface. The structure is certainly due to a purely temporary emergence of what was probably a small portion of the area of deposition.

There is another instance of interbedded carbonaceous matter and of penetrating roots near the south end of the Nukumaru Beach, a quarter of a mile to the south of the place where the fossil moa-bones were found. This is a far less marked instance than the former one. These

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two instances emphasize the shallow-water nature of the strata in the Nukumaru — Kai Iwi section, and they show also that there were temporary oscillations in the level of the land whilst the deposition of these rocks was in progress.

The continuity of the stratigraphical succession is, however, well shown by the nature of the fossil mollusca which are contained in the rocks, for they display a nearly uniform gradual change as one proceeds northward along the coast-line, and therefore into lower strata. It has already been suggested that the small pebbles in some of the strata came from the northwest of Nelson, but no suggestion has yet been made as to the source of the great mass of the blue clay, which constitutes by far the greater part of these younger Tertiary sediments. One of the most notable features of the mineralogical composition of this blue clay is its highly micaceous nature. The mica is muscovite, and whenever a coarser stratum than usual occurs the mica flakes in particular are of such a large size that the only origin that can reasonably be assigned to them is a granitic rock. There is at the present time no such rock known to occur in the North Island, and unless some large pre-existing mass has been submerged, or covered up by sediments, we must look to the South Island for the rock-mass from which all this sediment was derived. There is no reason to think that any previously existing granite mass in the North Island is now concealed from view, and it is to the South Island that our attention is at once directed.

In the north-west of Nelson there is now a large area of country which is composed of a granite. It is suggested that it is from this rock that the younger Tertiary sediments of the Wanganui district were derived. It is true that so far as that granite is known there is not a great deal of muscovite in its composition; but up to the present time little petrographical work has been done on the rock, and it is quite possible that a portion of the granite, which crops out over an area of some 800 square miles, is more micaceous than the few specimens that have been closely examined. It is true also that on its seaward margin the granite has a superficial covering of Tertiary rocks of a greater age than the Wanganui series of sediments. The granite mountains rise, however, to a height of 6,000 ft., and no Tertiary sediments are exposed at a greater height than 2,000 ft. It is a fact also that no granite pebbles have been found in the coarser strata that often occur in the Wanganui sediments. This objection, however, is not a strong one, because the granite is notoriously friable, and no pebbles are found on the long beach of Farewell Spit, which is mainly composed of detritus from the granite.

At the present time there is no material on the beaches of the Wanganui coast that could have a granite origin assigned to it, and the depth of the north-west entrance of Cook Strait is too great to allow of the drift of any such material from the South Island, especially when the strong inflow and outflow of tides through the strait is considered. If the origin of the sediment is to be traced to the Karamea granite, as is here suggested, Cook Strait must at that time have been closed, and a continuous beach must have extended from Kahurangi Point to the Wanganui area.

The thickness of the sediments is a matter of great importance in the subject of this paper. The direction of the strike is, on the whole, so constant, and makes such a considerable angle with the coast-line, that it is at once evident that in a distance of twenty miles along the coast a great thickness of sediment must be passed through. Taking the average of the dip and strike mentioned above (strike 70° and dip 4½°), it is found that the thickness of rocks between Castlecliff and Kai Iwi is 950 ft., the

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thickness between Kai Iwi and Nukumaru is 1,050 ft., and that between Nukumaru and Waipipi is 1,450 ft. If the rate at which these sediments were deposited can be approximately estimated, it should be possible to calculate the time at which various species of mollusca made their last appearance. It is generally estimated that the average rate of deposition of sediment amounts to about 1 ft. in 100 years (Sollas, 1905, p. 24). This estimate, of course, cannot have a precise application in all actual cases, if in any one, because in every case the true rate must depend upon the size of the country that is being denuded and is supplying the sediment, upon the hardness of the rock of which this country is mainly composed, and, of course, upon the distance from the coast-line of the area in which deposition is taking place.

In the present instance the area of land which was undergoing denudation was probably small, and therefore supplied sediment at a slow rate. Whether the land was composed of granite rock or was in part formed of sediments that had been derived from granite and raised above the sea-level a little while earlier and again submitted to denudation is by no means certain. On the one hand, the fact that from Karioi to Waiouru, sixty miles inland, rocks of this very young Tertiary age were being deposited points to the conclusion that there was at this time a wide extent of shallow sea in the Wanganui district. On the other hand, the inter-bedded land-surface near the mouth of the Okehu Stream supports the idea that a part at least of the huge Tertiary area to the north was above the sea-level for a portion at least of the period of deposition. If that was the case sediment would have been supplied at a relatively rapid rate. Until the country to the north has been more fully examined with the object of ascertaining how large an area is bare of a covering of these youngest Tertiary rocks it is not safe to offer any opinion on this matter. Much of the sediment was deposited at a considerable distance from the coast-line, and in water of considerable depth. This is proved both by the finegrained texture of the sediment and by the nature of the fossil mollusca embedded in it. The sediment is generally of an extremely fine grain and contains a large proportion of small mica plates, two features which point to deposition in an area which was reached by the finest and lightest sediment only.

The fossil mollusca found over the first five miles north of Castlecliff are of a nature which indicates that the sea-floor was at a depth of between 50 and 100 fathoms. At Kai Iwi the depth of the water was probably nearer the former than the latter figure. If this were the case the rate of deposition must have been a very slow one. Thus the following considerations point to the probability of slow deposition: (1) The small size of the land area from which the sediment was derived; (2) the hard nature of the rocks that were undergoing denudation; (3) the distance of the area of deposition from the area of denudation; (4) the depth of water in which the deposition took place. On the other hand, it is possible that—(1) some of the material was derived from older Tertiary rocks only lately deposited (if that were the case the deposition area may have been quite close to that of denudation); (2) some of the strata were deposited under shallow-water conditions and close to the shore-line. A balancing of these considerations inclines us to the opinion that the material was possibly deposited at the rate of 1 ft. of sediment in 200 years. If this rate of accumulation is applied generally to the thicknesses of sediment that have been already mentioned, we find that the Waipipi beds are 690,000 years older, those at Nukumaru 400,000 years older, and those at Kai Iwi 190,000 years older than the Castlecliff beds.

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Fossils from Castlecliff.

The collections in this locality were made in the marine cliffs over a distance of two miles from the Castlecliff end. The rocks are everywhere blue clay, or “papa,” which, however, has a tendency to become more sandy as the strata rise in the face of the cliff when they are followed to the northward. This probably indicates that the water became rather more shallow in this direction—a conclusion which is supported by the very nature of the mollusca that are found in them as they are followed northwards.

In the following lists extinct species are marked with an asterisk.

  • Acanthochites zelandicus (Q. & G.)

  • Acmaea daedala (Sut.)

  • *Acteon sulcatus (Hutt.)

  • Alcira inconstans (Sut.)

  • Amphidesma gaymardi (Desh.)

  • Amphidesma ventricosa (Gray)

  • Ancilla australis (Sow.)

  • Ancilla australis pyramidalis (Reeve)

  • Ancilla depressa (Sow.)

  • Ancilla mucronata (Sow.)

  • Ancilla novae-zelandiae (Sow.)

  • Arca novae-zelandiae (E.A. Smith)

  • [= decussata Sut., not Sow.]

  • Argobuccinum australasia (Perry)

  • Astraea heliotropium (Mart.)

  • Atrina zelandica (Gray)

  • Barnea similis (Gray)

  • Bathytoma albula (Hutt.)

  • Bathytoma nodilirata (Murd. & Sut.)

  • Bathytoma zealandica (E. A. Smith)

  • [= cheesemani (Hutt.)]

  • *Bezanconia huttoni (Coss.)

  • Caecum digitulum (Hedley)

  • *Calliostoma hodgei (Hutt.)

  • Calliostoma pellucidum (Val.)

  • *Calliostoma ponderosum (Hutt.)

  • Calliostoma punctulatum (Mart.)

  • Calliostoma selectum (Chemn.)

  • Calyptraea alta (Hutt.)

  • Calyptraea novae - zelandiae Lesson [= maculata (Q. & G.)]

  • Calyptraea tenuis (Gray)

  • Cantharidus sanguineus (Gray)

  • Cardita calyculata (L.)

  • Chione mesodesma (Q. & G.)

  • Chione spissa (Desh.)

  • Chione stutchburyi (Gray)

  • Chione yatei (Gray)

  • Cominella lurida (Phil.)

  • Cominella virgata (A. Ad.)

  • Corbula macilenta (Hutt.)

  • Corbula zelandica (Q. & G.)

  • *Couthouyia exilis (Murdoch)

  • Crepidula costata (Sow.)

  • Crepidula monoxyla (Less.)

  • Cylichnella striata (Hutt.)

  • Cymatium spengleri (Chemn.)

  • Cytherea oblonga (Hanley)

  • Daphnella cancellata (Hutt.)

  • Daphnella lacunosa (Hutt.)

  • Daphnella striata (Hutt.)

  • Dentalium ecostatum (T. W. Kirk)

  • Dentalium huttoni (T. W. Kirk)

  • Dentalium zelandicum (Sow.)

  • Diplodonta zelandica (Gray)

  • Divaricella cumingi (Ad. & Ang.)

  • Dosinia anus (Phil.)

  • Dosinia greyi (Zittel)

  • Dosinia subrosea (Gray)

  • *Drillia buchanani (Hutt.)

  • Drillia laevis (Hutt.)

  • Drillia novae-zelandiae (Reeve)

  • *Drillia wanganuiensis (Hutt.)

  • Emarginula striatula (Q. & G.)

  • Epitonium zelebori (D [ unclear: ] ker)

  • Erycina parva (Desh.)

  • Ethalia zelandica (H. & J.)

  • Euthria linea (Mart.)

  • Euthria linea traversi (Hutt.)

  • Euthria littorinoides (Reeve)

  • Euthria striata (Hutt.)

  • Fissuridea monilifera (Hutt.)

  • Fusinus spiralis (A. Ad.)

  • Glycymeris laticostata (Q. & G.)

  • Glycymeris modesta (Angas)

  • *Hipponix radiatus (Hutt.)

  • Kellia suborbicularis (Mont.)

  • Leptomya perconfusa (Iredale)

  • Leptothyra fluctuata (Hutt.)

  • Lima angulata (Sow.)

  • Lima bullata (Born)

  • Lima lima (L.)

  • Liotia benhami (Sut.)

  • Lissospira corulum (Hutt.)

  • Lucinida concinna (Hutt.)

  • Macoma edgari (Iredale)

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  • Macrocallista multistriata (Sow.)

  • Mactra discors (Gray)

  • Mactra elongata (Q. & G.)

  • Mactra ovata (Gray)

  • Mactra scalpellum (Reeve)

  • Malletia australis (Q. & G.)

  • Mangilia amoena (E. A. Smith)

  • Mangilia sinclairi (E. A. Smith)

  • Mitrella choava (Reeve)

  • Modiolus australis (Gray)

  • Murex angasi (Crosse)

  • Murex octogonus (Q. & G.)

  • Murex octogonus umbilicatus (T. -Woods)

  • Murex zelandicus (Q. & G.)

  • Musculus impactus (Herm.)

  • Myodora antipodum (E. A. Smith)

  • Myodora striata (Q. & G.)

  • Myodora subrostrata (E. A. Smith)

  • Mytilus canaliculus (Mart.)

  • Mytilus edulis (L.)

  • Mytilus maorianus (Iredale)

  • Natica australis (Hutt.)

  • Natica zelandica (Q. & G.)

  • Nucula hartvigiana (Pfr.)

  • Nucula nitidula (A. Ad.)

  • Nuculana bellula (A. Ad.)

  • Nuculana fastidiosa (A. Ad.)

  • Odostomia bembix (Sut.)

  • Odostomia huttoni (Sut.)

  • Odostomia rugata (Hutt.)

  • Ostrea angasi (Sow.)

  • Ostrea corrugata (Hutt.)

  • Panope zelandica (Q. & G.)

  • Paphia intermedia (Q. & G.)

  • Pecten convexus (Q. & G.)

  • Pecten medius (Lamk.)

  • Pecten radiatus (Hutt.)

  • Pecten zelandiae (Gray)

  • Phalium achatinum pyrum (Lamk.)

  • *Philobrya trigonopsis (Hutt.)

  • Protocardia pulchella (Gray)

  • Psammobia lineolata (Gray)

  • Psammobia stangeri (Gray)

  • Psammobia zelandica (Desh.)

  • Pupa affinis (A. Ad.)

  • Pupa alba (Hutt.)

  • *Rissoa semisulcata (Hutt.) [”Lironoba“]

  • Rissoina chathamensis (Hutt.) [= R. rugulosa (Hutt.)]

  • Rissoina emarginata (Hutt.) [”Nozeba“]

  • Rissoina olivacea (Hutt.) [”Dardanula“]

  • Rochefortia reniformis (Sut.)

  • Saxicava arctica (L.)

  • Seila terebelloides (Mts.)

  • Sinum undulatum (Hutt.)

  • Siphonalia caudata (Q. & G.)

  • Siphonalia dilatata (Q. & G.)

  • Siphonalia mandarina (Duclos)

  • Siphonalia nodosa (Mart.)

  • Siphonalia valedicta (Wats.)

  • Solariella egena (Gould)

  • Soletellina nitida (Gray)

  • Spisula equilateralis (Desh.)

  • Spisula ordinaria (E. A. Smith)

  • Struthiolaria papulosa (Mart.)

  • Struthiolaria vermis (Mart.)

  • *Surcula castlecliffensis (Marshall and Murdoch)

  • Tellina eugonia (Sut.)

  • Tellina huttoni sterrha (Sut.)

  • Tellina liliana (Iredale)

  • Tellina spenceri (Sut.)

  • Terebra tristis (Desh.)

  • *Thracia vegrandis (Marshall and Murdoch)

  • Thracia vitrea (Hutt.)

  • Tornatina pachys (Wats.)

  • Trichotropis clathrata (Sow.)

  • *Trochus conicus (Hutt.)

  • Trochus tiaratus (Q. & G.)

  • Trochus viridis (Gmel.)

  • Trophon ambiguus (Phil.)

  • Trophon cheesemani (Hutt.)

  • Trophon pumila Sut. [= T. bonneti Cossm.]

  • Tugalia intermedia (Reeve)

  • Turbo granosus (Mart.)

  • Turbo smaragdus (Mart.)

  • Turbonilla zealandica (Hutt.)

  • Turritella carlottae (Wats.)

  • Turritella rosea (Q. & G.)

  • Turritella symmetrica (Hutt.)

  • Venericardia lutea (Hutt.)

  • Venericardia purpurata (Desh.)

  • Venericardia unidentata (Basterot)

  • Vexillum marginatum (Hutt.)

  • Vexillum rubiginosum (Hutt.)

  • Voluta arabica (Mart.)

  • Voluta arabica elongata (Swains.)

  • Voluta gracilis (Swains.)

  • Xymene plebejus (Hutt.)

  • Zenatia acinaces (Q. & G.)

The total number of species is 181, of which 92.8 per cent. are Recent.

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Fossils from Kai Iwi.

In this locality collections were made for a distance of three-quarters of a mile south of the mouth of the Kai Iwi Stream. The collection was made by one of us (Marshall) in a single day's excursion, and it is probable that the list will have a large number of additions made to it in the future.

  • Acteon sulcatus (Hutt.)

  • Alcira inconstans (Sut.)

  • Ancilla australis (Sow.)

  • Arca reticulata (Gmel.)

  • Atrina zelandiae (Gray)

  • Barnea similis (Gray)

  • *Bezanconia huttoni (Cossm.)

  • *Calliostoma hodgei (Hutt.)

  • Calliostoma punctulatum (Mart.)

  • Calliostoma selectum (Chemn.)

  • Calyptraea novae-zelandiae (Lesson)

  • Calyptraea tenuis (Gray)

  • Cantharidus sanguineus (Gray)

  • Cardita calyculata (L.)

  • Chione mesodesma (Q. & G.)

  • Cominella virgata (A. Ad.)

  • Corbula macilenta (Hutt.)

  • Cytherea oblonga (Hanley)

  • Daphnella cancellata (Hutt.)

  • Dentalium ecostatum (T. W. Kirk)

  • Dentalium nanum (Hutt.)

  • Divaricella cumingi (Ad. & Ang.)

  • *Drillia buchanani (Hutt.)

  • Drillia novae-zelandiae (Reeve)

  • *Drillia wanganuiensis (Hutt.)

  • Emarginula striatula (Q. & G.)

  • Epitonium zelebori (Dkr.)

  • Erycina parva (Desh.)

  • Euthria littorinoides (Reeve)

  • Glycymeris modesta (Angas)

  • Leptomyia perconfusa (Iredale)

  • Lucinida concinna (Hutt.)

  • Macoma edgari (Iredale)

  • Macrocallista multistriata (Sow.)

  • Mactra scalpellum (Reeve)

  • Malletia australis (Q. & G.)

  • Mangilia amoena (E. A. Smith)

  • Murex angasi (Crosse)

  • Murex zelandicus (Q. & G.)

  • Myodora antipodum (E. A. Smith)

  • Natica australis (Hutt.)

  • Natica zelandica (Q. &. G.)

  • Nucula nitidula (A. Ad.)

  • Nuculana bellula (A. Ad.)

  • Odostomia bembix (Sut.)

  • Ostrea corrugata (Hutt.)

  • Panope zelandica (Q. & G.)

  • Pecten zelandiae (Gray)

  • *Philobrya trigonopsis (Hutt.)

  • Poroleda lanceolata (Hutt.)

  • Protocardia pulchella (Gray)

  • Psammobia lineolata (Gray)

  • Saxicava arctica (L.)

  • *Serpulorbis sipho (Lamk.)

  • Sinum undulatum (Hutt.)

  • Siphonalia caudata (Q. & G.)

  • Siphonalia mandarina (Duclos)

  • Siphonalia nodosa (Mart.)

  • Spisula ordinaria (E. A. Smith)

  • Struthiolaria papulosa (Mart.)

  • Struthiolaria vermis (Mart.)

  • *Surcula castlecliffensis (Marshall and Murdoch)

  • Tellina eugonia (Sut.)

  • Terebra tristis (Desh.)

  • Trichotropis clathrata (Sow.)

  • *Trochus conicus (Hutt.)

  • Trochus tiaratus (Q. &. G.)

  • Trophon ambiguus (Phil.)

  • Trophon cheesemani (Hutt.)

  • Trophon corticatus (Hutt.)

  • Trophon pumila (Sut.)

  • Tugalia intermedia (Reeve)

  • Turritella rosea (Q. & G.)

  • Turritella symmetrica (Hutt.)

  • Venericardia lutea (Hutt.)

  • Venericardia purpurata (Desh.)

  • Venericardia unidentata (Bast.)

  • Vexillum planatum (Hutt.)

  • Vexillum rubiginosum (Hutt.)

  • Voluta gracilis (Swains.)

  • *Xymene expansus (Hutt.)

  • Xymene plebejus (Hutt.)

This list contains eighty-two species, of which eight are extinct. The percentage of Recent species is therefore 90.25.

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Fossils from Nukumaru.

Collections were made over a distance of one mile south from the Nukumaru boat-landing. One of us (Marshall) spent four days in collecting in this locality, and the other (Murdoch) spent two days. These are the Rotella beds of Park (1887, p. 63).

  • Acanthochites zelandicus (Q. & G.)

  • Alcira inconstans (Sut.)

  • *Amphidesma crassiformis n. sp.

  • Amphidesma gaymardi (Desh.)

  • *Anachis pisaniopsis (Hutt.)

  • Ancilla australis (Sow.)

  • Ancilla depressa (Sow.)

  • Ancilla novae-zelandiae (Sow.)

  • Anomia huttoni (Sut.)

  • *Ataxocerithium perplexum (Marshall and Murdoch)

  • Barnea similis (Gray)

  • *Calliostoma hodgei (Hutt.)

  • Calliostoma pellucidum (Val.)

  • Calliostoma punctulatum (Mart.)

  • Calyptraea alta (Hutt.)

  • Calyptraea tenuis (Gray)

  • Cantharidus sanguineus (Gray)

  • Cardita calyculata (L.)

  • Chione mesodesma (Q. & G.)

  • Chione spissa (Desh.)

  • Chione yatei (Gray)

  • Cochlodesma angasi (C. & F.)

  • Cominella lurida (Phil.)

  • Cominella virgata (A. Ad.)

  • Crepidula crepidula (L.)

  • *Crepidula gregaria (Sow.)

  • Cylichnella striata (Hutt.)

  • Cytherea oblonga (Hanley)

  • *Diplodonta ampla (Hutt.)

  • Diplodonta zelandica (Gray)

  • Dosinia anus (Phil.)

  • Dosinia subrosea (Gray)

  • Epitonium zelebori (Dkr.)

  • Ethalia zelandica (H. & J.)

  • *Eulimella media (Hutt.)

  • Euthria striata (Hutt.)

  • Fissuridea monilifera (Hutt.)

  • Glycymeris modesta (Angas)

  • Leptomya perconfusa (Iredale)

  • *Lucinida levifoliata (Marshall and Murdoch)

  • *Lutraria solida (Hutt.)

  • Macoma edgari (Iredale)

  • Mactra ordinaria (E. A. Smith)

  • Mactra rudis (Hutt.)

  • Mactra scalpellum (Reeve)

  • Mangilia amoena (E. A. Smith)

  • *Melina zealandica (Sut.)

  • Myodora antipodium (E. A. Smith)

  • Myodora subrostrata (E. A. Smith)

  • Mytilus maorianus (Iredale)

  • *Neolepton sp.

  • Nucula nitidula (A. Ad.)

  • Odostomia huttoni (Sut.)

  • Ostrea angasi (Sow.)

  • *Ostrea ingens (Zittel).

  • *Paphia curta (Hutt.)

  • Paphia intermedia (Q. & G.)

  • Pecten zelandiae (Gray)

  • *Philobrya trigonopsis (Hutt.)

  • Rissoina olivacea (Hutt.) [”Dardanula“].

  • *Rissoa semisulcata (Hutt.) [”Lironoba“]

  • Seila chathamensis (Sut.)

  • Sinum undulatum (Hutt.)

  • Siphonalia caudata (Q. & G.)

  • Siphonalia dilatata (Q. & G.)

  • Siphonalia mandarina (Duclos)

  • Soletellina nitida (Gray)

  • *Struthiolaria frazeri (Hutt.)

  • Struthiolaria vermis (Mart.)

  • Terebra tristis (Desh.)

  • *Trochus conicus (Hutt.)

  • Trochus tiaratus (Q. & G.)

  • Trophon ambiguus (Phil.)

  • Trophon cheesemani (Hutt.)

  • Turbonilla zealandica (Hutt.)

  • Turritella rosea (Q. & G.)

  • Turritella symmetrica (Hutt.)

  • Venericardia difficilis (Desh.)

  • Venericardia lutea (Hutt.)

  • Venericardia purpurata (Desh.)

  • *Voluta turrita (Sut.)

  • *Voluta turrita nukumaruensis (Marshall and Murdoch)

  • *Xymene expansus (Hutt.)

  • Xymene plebejus (Hutt.)

There are eighty-four species in this list, of which 76.2 per cent. are Recent.

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One of the main features of the fauna in this locality is the large size of many of the extinct species that are found. Not only this, but the large species are represented by a great number of individuals, and at the first glance it is apparent that the fauna is essentially different from that of Kai Iwi and of Castlecliff. In addition to this, several of the species that occur in the strata at Castlecliff and are also of Recent occurrence have unusual dimensions at Nukumaru. Of these, Chione yatei, Cytherea oblonga, and Paphia intermedia are noticeable. Of the extinct species, Melina zealandica, Cytherea enysi, Lutraria solida, Lucinida levifoliata, Struthiolaria frazeri, and Amphidesma crassiformis are all of large size. This large size of the shells in itself suggests that climatic conditions at the time that these strata were deposited were more genial than those that now prevail, and this suggestion, due to the mere size of the shells, is strengthened by the occurrence of such a genus as Melina, which is now, of course, extinct in New Zealand waters.

The bone of Dinornis robusta which was described in a previous paper came from the stratum that lies immediately below the bed in which the occurrence of the large shells is first especially conspicuous. Another moa-bone has since been found, and it is identified by Professor Benham as part of the right tibia of Mesopteryx casuarina Owen. The medullary cavity of this bone is partly filled with pyrite, a sufficient proof that the bone has been preserved in strata that lie beneath the level to which oxidizing waters can percolate.

Fossils from Waipipi.

This locality is about five miles north of Nukumaru along the coastline. The collection was made from the outcrops of the cliffs over a distance of one mile to the north of the mouth of the Waipipi Stream and a quarter of a mile to the south of it. The rocks are for the main part tough blue papa, or blue clay, with a few distinctly sandy or micaceous strata. It is in the latter that the majority of the fossils were found.

  • Ancilla australis (Sow.)

  • Ancilla novae-zelandiae (Sow.)

  • *Ancilla pseud-australis (Tate)

  • Astraea heliotropium (Mart.)

  • Atrina zelandica (Gray)

  • Bathytoma albula (Hutt.)

  • Bathytoma zealandica (E. A. Smith)

  • Calliostoma pellucidum (Val.)

  • Calyptraea alta (Hutt.)

  • Calyptraea tenuis (Gray)

  • *Cardium spatiosum (Hutt.)

  • Chione mesodesma (Q. & G.)

  • Chione spissa (Desh.)

  • Chione yatei (Gray)

  • Corbula macilenta (Hutt.)

  • *Crassatellites obesus (A. Ad.)

  • Crepidula crepidula (L.)

  • *Crepidula gregaria (Sow.)

  • *Cymbiola (Miomelon) corrugata (Hutt.)

  • *Cytherea enysi (Hutt.)

  • Cytherea oblonga (Hanley)

  • *Dentalium solidum (Hutt.)

  • *Diplodonta ampla (Hutt.)

  • Divaricella cumingi (Ad. & Ang.)

  • Dosinia lambata (Gould)

  • *Dosinia magna (Hutt.)

  • Dosinia subrosea (Gray)

  • *Erycina cf. bifurca (Webster)

  • Glycymeris laticostata (Q. & G.)

  • *Glycymeris subglobosa (Sut.)

  • Lima angulata (Sow.)

  • Lima bullata (Born.)

  • *Lima waipipiensis (Marshall and Murdoch)

  • *Lucinida levifoliata (Marshall and Murdoch)

  • *Lutraria solida (Hutt.)

  • Macoma edgari (Iredale)

  • Macrocallista multistriata (Sow.)

  • Mactra scalpellum (Reeve)

  • Marginella pygmaea (Sow.) (?)

– 125 –
  • *Melina zealandica (Sut.)

  • Musculus impacta (Herm.)

  • Mytilus maorianus (Iredale)

  • Natica australis (Hutt.)

  • *Natica ovata (Hutt.)

  • *Natica sagena (Sut.)

  • Natica zelandica (Q. & G.)

  • Nuculana fastidiosa (A. Ad.)

  • Odostomia aff. bembix (Sut.)

  • *Olivella neozelanica (Hutt.)

  • Ostrea angasi (Sow.)

  • *Ostrea ingens (Zittel)

  • Panope zelandica (Q. & G.)

  • *Paphia curta (Hutt.)

  • Pecten convexus (Q. & G.)

  • *Pecten semiplicatus (Hutt.)

  • *Pecten triphooki (Zittel)

  • Pecten zelandiae (Gray)

  • *Phalium fibratum (Marshall and Murdoch)

  • Protocardia pulchella (Gray)

  • Psammobia lineolata (Gray)

  • Siphonalia mandarina (Duclos)

  • *Siphonalia subnodosa (Hutt.)

  • Soletellina nitida (Gray)

  • *Struthiolaria canaliculata (Zittel)

  • *Struthiolaria zelandica (Marshall and Murdoch)

  • Turritella rosea (Q. & G.)

  • Turritella symmetrica (Hutt.)

  • Venericardia difficilis (Desh.)

  • Venericardia lutea (Hutt.)

  • *Voluta turrita (Sut.)

  • *Voluta morgani (Marshall and Murdoch)

  • Zenatia acinaces (Q. & G.)

This list contains seventy-two species, of which 61 per cent, are Recent.

The remarks that have been made about the occurrence of large shells in the strata at Nukumaru apply with even greater force to these beds, for there are these additional extinct species of large dimensions: Cardium spatiosum, Paphia curta, Ostrea ingens, Pecten triphooki, Dentalium solidum, Natica sagena, Natica ovata, and Crassatellites obesus. The appearance of the large Phalium fibratum adds to the effect. It is hard to resist the opinion that either the climate of the country as a whole was more genial or that the region was a sea-floor that was washed by a warmer current when the sediment was deposited. The latter alternative, however, is an improbable explanation, because the nature of the sediment is essentially the same at Waipipi as it is in the highest of the Castlecliff beds. It thus becomes probable that there was a reduction in the temperature of the New Zealand area which extended over a considerable interval of time. This gradual cooling of the climate continued throughout the lapse of time between the deposition of the Waipipi beds and of the upper beds at Nukumaru. In an earlier portion of this paper this interval of time is stated as possibly as much as 300,000 years.

The general results of this examination of the fossils on the coast-line between Castlecliff and Waipipi thus show clearly that as lower and lower strata are inspected the percentage of extinct species of mollusca becomes greater and greater. This increase of extinct species could be due mainly to three different conditions.

(1.) The mere increase in age as the lower beds are reached might in itself account for it, because as time proceeds various species become outclassed in the struggle for existence that is always in progress. The many slight changes in food-supply, ocean currents, and accompanying variations of temperature may be as potent in this direction as the mere lapse of time and the consequent change of vital energy of the different species.

(2.) The migration of additional species to the district or to the region would, of course, have a similar effect; but in our opinion our collections of the mollusca afford no evidence of this. On the contrary, as one of us (Marshall) has frequently pointed out before, the present molluscan fauna of New Zealand seems rather to be a remnant of a more extensive fauna

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of early or Middle Tertiary age. There is certainly a striking poverty of mollusca in the Wanganui beds when they are compared with that of the very small exposure of fossiliferous strata at Target Gully, near Oamaru, and elsewhere in the Middle Tertiary strata. This relative poverty in species is certainly not due to less careful collecting at Wanganui, for a greater amount of time has been spent in the latter locality and a much greater variety of strata has been scrutinized than at Oamaru. There are no additional genera of any importance in the Castlecliff strata, and there is no sudden inrush of new species, so far as our investigations go, at any horizon of the beds exposed on the coast-line between Wanganui and Waipipi.

(3.) A considerable and general change of climate must naturally have a great effect upon the molluscan life on the coast-line. It is, of course, well established that towards the close of Tertiary time in Europe and in America and elsewhere there was a great change in climate, especially during the Pliocene period. The high percentage of Recent species of mollusca in all the strata with which this paper deals shows clearly enough that they are of Upper Tertiary age. Those at Waipipi perhaps correspond to the early Pliocene of Europe, or perhaps to the later Miocene, while the Castlecliff beds probably represent the highest Pliocene. The change in molluscan fauna may therefore be mainly due to the gradual reduction of temperature that was a feature of all climates during the Pliocene period. The faunal change in this district seems to have been much less rapid in the upper portion of the strata examined than in the lower ones. In the 960 ft. of strata between Castlecliff and Kai Iwi only 2.5 per cent. of extinct species appear, while in the 1,050 ft. between Kai Iwi and Nukumaru an additional 14 per cent. appear, and between Nukumaru and Waipipi, in a thickness of 1,450 ft. of sediment, 15 per cent. more of extinct species are found. In other words, between Waipipi and Nukumaru 1 per cent of the species becomes extinct in every 97 ft. of sediment. Between Nukumaru and Kai Iwi the rate is 1 per cent. of extinction for every 75 ft. of sediment, and between Kai Iwi and Castlecliff the rate is much slower and amounts to no more than 1 per cent. in a thickness of 384 ft. of sediment. The general average of extinction for a total thickness of 3,560 ft. is almost exactly 1 per cent. of the species in every 100 ft. If, as suggested before, this sediment has been deposited at an average rate of 1 ft. in 200 years, it follows that on the average during the greater part of the Pliocene period in New Zealand 1 per cent of the species of marine mollusca has become extinct in every 20,000 years. It is not intended to assert any accuracy for this result, though it is thought that it is of the same order of magnitude as the actual result would be if all the various factors could be ascertained with certainty.

It has been stated earlier that, as far as the stratigraphy can be seen in the marine cliffs, there is certainly no sign of any unconformity. The cliffs give an actually continuous section from Castlecliff to Nukumaru. To the north of Nukumaru the continuity is interrupted for a considerable distance, but the close resemblance of the fauna of the Waipipi beds to that of Nukumaru in itself points to the conclusion that deposition was continuous. This idea is strongly supported by the fauna which is found at Wilkie's Bluff, on the left bank of the Waitotara River, two miles and a half below the railway-bridge, a locality intermediate between Nukumaru and Waipipi. Here there is a great abundance of Ostrea ingens, with Pecten triphooki and some Cardium spatiosum and Lutraria solida. Palaeontologically as well as in geographical position the bluff

– 127 –

forms a connecting-link between Waipipi and Nukumaru. The large number of species that is found throughout this thick series of strata is in itself sufficient proof that the series is continuous, and it is interesting to find that so many well-known species of Miocene occurrence rise so high into the Wanganui Tertiaries. In this Wanganui area at least it is possible to determine the upper limits of their occurrence. So far as our collections have given us information the following are the levels at which the specified well-known Miocene species finally disappear. At present it is most convenient to define their position as so-many feet below the highest beds at Castlecliff.

  • Crepidula gregaria, uncommon above 1,200 ft.

  • Lutraria solida, 2,000 ft.

  • Cytherea enysi, 2,100 ft.

  • Melina zelandica, 2,100 ft.

  • Struthiolaria frazeri, 2,100 ft.

  • Ostrea ingens, 2,100 ft.

  • Cardium spatiosum, 2,700 ft.

  • Pecten triphooki, 2,700 ft.

  • Pecten semiplicatus, 3,000 ft.

  • Dentalium solidum, 3,500 ft.

  • Paphia curta, 3,500 ft.

  • Natica ovata, 3,500 ft.

  • Natica sagena, 3,500 ft.

  • Crassatellites, 3,500 ft.

  • Struthiolaria canaliculata, 3,500 ft.

  • Olivella neozelanica, 3,500 ft.

  • Dosinia magna, 3,800 ft.

The highest beds at Castlecliff, the horizon to which these occurrences are referred, are covered unconformably by sands and gravels of volcanic material, which usually have a good deal of included timber, and are referred to the Pleistocene. Thomson has lately called this formation generally the Hawera series.

It is noticeable that many species which have a Recent occurrence and which are common at Castlecliff are quite absent from our collections at Nukumaru and at Waipipi, though from a lithological standpoint there is little change in the rock, and the conditions of deposition seem to have been substantially the same at Waipipi as at Castlecliff.

Struthiolaria papulosa was last found one mile north of Kai Iwi, about 1,200 ft. below the highest beds at Castlecliff. Struthiolaria vermis was last found at Nukamaru, 2,100 ft. down, and it is very scarce there.

Pecten medius has not been found below 500 ft., though a shell-fragment probably belonging to this species was found at the mouth of the Okehu Stream, 1,700 ft. down.

Murex zelandicus has not been found at Nukumaru or at Waipipi, though it has frequently been found in rocks of Miocene age in the Oamaru district, and at Pakaurangi Point in the Kaipara Harbour. Murex angasi and Murex octogonus also have not been found north of Kai Iwi, though they too occur in Middle Tertiary rocks in various parts of New Zealand.

It does not seem to be the case that any importance is to be attached to the absence of these species as an indication of climatic changes on the New Zealand coast-line. The absence of species of Murex and of the Recent species of Struthiolaria might at first suggest a colder climate for the Nukumaru and Waipipi beds, but this idea is at once offset by the fact that Pecten medius and Struthiolaria papulosa both occur at the present day in the most southern of New Zealand waters. As more extensive collections are made and additional localities of this district are examined it may well happen that such small peculiarities will be explained. It is also possible that by careful collecting the development of some of the species that have most recently appeared, such as Pecten medius and Struthiolaria papulosa, may be most definitely traced. On the other hand, it may possibly be found that a few of these species reached these shores from other faunal regions.

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One point often crops up in the examination of various fossil localities in the Tertiary rocks of New Zealand. In some strata there is a great predominance of gasteropods, while in others the lamellibranchs are far more numerous. So far as observations have gone up to the present time, this striking difference does not appear to be due to the depth of the water or to any other of the ordinary conditions that control the deposition of sediment.

List of Papers cited.

Hector, J., 1886. Outline of the Geology of New Zealand.

Hutton, F. W., 1885. Quart. Journ. Geol. Soc., vol. 41.

— 1886. Trans. N.Z. Inst., vol. 18, pp. 336–67.

— 1893. Macleay Memorial Volume, Linn. Soc. N.S.W.

Murdoch, R., 1900. Trans. N.Z. Inst., vol. 32, pp. 216–21.

Park, J., 1887. Rep. Geol. Explor. dur. 1886–87, pp. 24–73, &c.

Sollas, W. J., 1905. Age of the Earth.