Art. 9.—Early Tertiary Molluscan Faunas of New Zealand.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 54, 1923, Page 115

Art. 9.—Early Tertiary Molluscan Faunas of New Zealand. By P. Marshall, M.A., D.Sc., F.G.S., F.N.Z.Inst., Hector and Hutton Medallist. [Read before the Wanganui Philosophical Institute, 27th October, 1921; received by Editor, 3rd December, 1921; issued separately, 8th February, 1923.] On several occasions I have published articles on the fauna of the Hampden beds, as season after season of careful collecting has enabled me to record more and more of the species that occur in that singular collecting-ground. I have ventured to do this because the Mollusca found there are so markedly different from the species that are found in the numerous Tertiary collecting localities in New Zealand. As mentioned in earlier publications, I have compared the Hampden fauna with that found at Wangaloa mainly because of the distinct Cretaceous facies of some of the fossils found in these two localities. So marked is this Cretaceous facies in the case of the Wangaloa area that nearly all authorities agree in the opinion that the formation is of an Upper Cretaceous age, but not older than the Danian. This opinion is based mainly on the occurrence of Gilbertia, Pugnellus,* Wilckens, in two bulletins (1921) on the Cretaceous gasteropods of New Zealand, states that the Pugnellus from Wangaloa is a young form of Conchothyra parasitica. The author does not agree with this. Perissolax, and Heteroterma, though together with species of these genera there are a number of others that occur widely in the various Tertiary fossiliferous localities of New Zealand. When a comparison of this Wangaloa fauna is made with that of the Hampden beds it is found that there is a greater similarity with this than with any other Tertiary fauna that has yet been described in New Zealand. Although, however, the resemblances are considerable, the differences remain great, and it is with much hesitation that I have suggested that the two formations are contemporaneous. So great, however, are the differences between these faunas that I have thought it necessary to offer an explanation of them, and to justify the inclusion of the two formations in one and the same geological series. The explanation that I have suggested is based upon the nature of the lithological differences of the materials in which the fossils are embedded in the two localities. At Wangaloa the matrix is a fine sandstone which contains a few grains of glauconite, while at Hampden the rock is an extremely unctuous mudstone which contains abundance of glauconite, and frequent small concretions of pyrite. It is therefore obvious that the Wangaloa deposit was formed in relatively shallow water, and that of Hampden in water of far greater depth. This difference in station necessarily implies also a considerable difference in the nature of the fauna in the two localities, though it is probable that each of them would contain much the same percentage of Recent species. This suggestion, though apparently simple and evident, has been entirely misunderstood, for Morgan says that Marshall's “view still seems to be that Cretaceous and Tertiary faunas flourished at the same time, the former in deep water, the latter in shallow water, close to the early

Tertiary coast-line.” It is hard to imagine how such an interpretation could have been given to anything that I have written. Soon after I had begun an investigation of the geology of the Upper Cretaceous and Tertiary formations of New Zealand, more than ten years ago, I was forced to adopt the view that there had been continuous sedimentation in the New Zealand area from the Upper Cretaceous (Senonian) to the Pliocene. In all districts where there has been a close examination of the stratification it is agreed that no hiatus of any importance can be discovered, and in nearly every case it is admitted that the series of younger rocks is not interrupted by any period of discontinuity. From the palaeontological standpoint, however, there have been great difficulties in showing that the faunas run on from one to the other without any sudden change. This results mainly from the fact that the lower beds of this younger series of rocks are generally quite without fossils, or where any fossils are found they are in a state that makes it very difficult to collect and identify them. At the base of the formation there are occasionally a series of fossils that point definitely to a Senonian age, and there is a great deal of difference between this fauna and the one that is next in age, usually in much higher beds. It is only at Wangaloa that a fauna generally recognized as of Danian age has yet been found, though, as is now generally admitted, that of Hampden has close affinities with it. It is to be hoped that future work will discover additional collecting-grounds from these lower members of the series, and thus enable us to find out definitely if faunas with intermediate features have existed, as one would naturally be led to believe from the nature of the stratification. The Hampden fauna, of which a revised list is given below, now contains almost one hundred species of Mollusca, and, as is admitted by Thomson (Trans. N.Z. Inst., vol. 52, p. 390, 1920), it shows much more affinity with the Wangaloa fauna than does any other Tertiary fauna of New Zealand. The chief elements of the fauna that show its antiquity are species of the genera Trigonia, Gilbertia, and Dicroloma (Alaria). Morgan, in his recent notes and review of Suter's lists of New Zealand Tertiary Mollusca, admits that the Wangaloa fauna is of Cretaceous age (N.Z. Geol. Sur. Pal. Bull. No. 8, p. 98, footnote), but he also says later that no part of the Oamaru formation contains Cretaceous fossils. This statement certainly requires some qualification when applied to the Hampden fauna. Morgan classes the Hampden beds as of Eocene age (l.c., p. 101), and correlates them with strata in various New Zealand localities. There is, however, no palaeontological basis for this correlation, and it really remains a matter of personal opinion, based on a belief that the beds that are correlated together occur in the same position in the series in the different localities. The Kaiatan stage is said by Morgan to include all of these. In a paper published in 1920 (Trans. N.Z. Inst., vol. 52, p. 112) I drew attention to the relationship between the Hampden and the Waihao faunas, but stated that up to that time only very small collections had been made from the Waihao beds. During the past summer a collection was made by Mr. Murdoch and myself at McCullogh's Bridge. Some sixty-two species were found, and this collection, combined with those made by previous collectors, gives us a much more accurate knowledge of the fauna of those greensands which lie directly beneath the Waihao limestone, which is admitted by all to be the same horizon as that of the Oamaru limestone itself.

The following is the corrected list of the Hampden fauna, including the species that have been collected during the last four years. Admete anomala Marshall and Murdoch. Admete n. sp. Alectrion sp. Ampullina suturalis (Hutton). Ampullina waihaoensis Suter. Ancilla novae-zelandiae (Sowerby). Architectonica n. sp. Atrina sp. Aturia sp. Bathytoma sulcata (Hutton). Belophos incertus Marshall. Bonellitia aff. ovalis (Marshall). Borsonia zealandica (Marshall). Bullinela enysi (Hutton). Cardium sp. Cerithidea minuta Marshall. Cerithiella tricincta Marshall. Circulus inornatus Marshall. Clio aff. urenuiensis Suter. Cucullaea alta Sowerby. Cymatium minimum (Hutton). Dentalium mantelli Zittel. Dentalium pareorense Pilsbry and Sharp. Dicroloma zelandica Marshall. Epitonium gracillimum Suter. Epitonium parvicostatum Marshall. Epitonium rugulosum lyratum (Zittel) Epitonium tenuispiralis Marshall. Erato antiqua Marshall. Euthriofusus spinosus Suter. Exilia waihaoensis Suter. Fusinus altus Marshall. Fusinus aff. bicarinatus Suter. Fusinus aff. morgani Suter. Fusinus solidus Suter. Galeodea senex (Hutton). Gilbertia tertiaria (Marshall). Latirus dubius Marshall. Leptoconus pseudoarmoricus (Marshall and Murdoch). Lima angulata Sowerby. Limopsis aurita (Brocchi). Limopsis catenata Suter. Limopsis hampdenensis Marshall. Limopsis zitteli Ihering. Marginella aveniformis Marshall. Natica zelandica Q. & G. Nucula n. sp. Nuculana semiteres (Hutton). Ostrea wuellerstorfi Zittel. Ostrea sp. Pecten aff. fischeri Zittel. Pecten huttoni (Park). Polinices planispirus Suter. Protocardia pulchella (Gray). Rissoina obliquecostata Marshall and Murdoch. Sarepta obolella (Tate). Sarepta solenelloides Marshall. Sarepta tenuis Marshall. Seila attenuissima Marshall and Murdoch. Sinum carinatum (Hutton). Sinum elegans Suter. Soletellina sp. Struthiolaria cincta Hutton. Struthiolaria minor Marshall. Submargarita tricincta Marshall. Surcula aequispiralis Marshall. Surcula gravida Marshall. Surcula hamiltoni (Hutton). Surcula hampdenensis Marshall and Murdoch. Surcula marginalis Marshall. Surcula serotina Suter. Surcula torticostata Marshall. Surcula sp. Surcula sp. Terebra costata Hutton. Terebra sulcata Marshall. Trigonia areolata Marshall. Triphora aoteaensis Marshall and Murdoch. Turbonilla antiqua Marshall. Turris complicatus Suter. Turris curialis Marshall and Murduch. Turris duplex Suter. Turris margaritatus Marshall. Turris nexilis bicarinatus Suter. Turris politus Marshall. Turris regius Suter. Turris reticulatus Marshall. Turris sp. Turritella ornata Hutton. Turritella rudis Marshall. Turritella symmetrica Hutton. Verconella nodosa acuticostata (Suter). Verconella senilis (Marshall and Murdoch). Verconella turrita (Suter). Verticordia densicostata (Marshall). Voluta corrugata Hutton.

This list does not convey much actual information to any but those who are quite familiar with the Tertiary fauna of New Zealand. The following summary of the occurrence of the species will make its nature clearer: 45 per cent. are at present restricted to the Hampden fauna; 11 per cent. have been found also in the Waihao beds but nowhere else; 29 per cent. occur among the seventy species that have been found at Waihao; 20 per cent. occur among the 215 species found at Target Gully; 6 per cent. are of Recent occurrence. These figures clearly show the following facts:— (1.) The essential peculiarity of the molluscan fauna of Hampden. (2.) The close relationship with the Waihao fauna, for 44 per cent. of the fossils that have been found at McCullogh's Bridge on the Waihao have also been found at Hampden. (3.) Less than 10 per cent. of the 215 fossils that have been found in the Target Gully beds have also been found at Hampden. Since these Target Gully beds rest directly on the limestone, and the Waihao beds lie immediately below it, the fact at once becomes clear that during the deposition of the limestone a great faunal change took place. (4.) The small percentage of Recent species shows that the Hampden beds are not older than the European Eocene (of which they are in all probability the equivalent); and, as stated elsewhere, the Recent species are represented by very few specimens, and several of them have not been identified with absolute certainty. The following is a list of the Waihao Mollusca, most of which (actually sixty-one species) were collected in January, 1921, by Marshall and Murdoch from the right bank of the river directly below McCullogh's Bridge. The list includes also a few species that were collected by Uttley in 1912 and by Thomson in 1917, but the three species of Verconella given in the list of Suter's identifications of the latter collection are omitted, as the specimens are said to be juvenile, and in our opinion it is not satisfactory to identify species of that genus from juvenile specimens. The lists from which the names of these additional species were taken will be found in the N.Z. Geol. Surv. Paleon. Rep. No. 8, pp. 66 and 67. Ampullina suturalis (Hutton). Ampullina waihaoensis Suter. Ancilla novae-zelandiae (Sowerby). Ancilla waikopiroensis Suter. Architectonica ngaparaensis Suter. Aturia. Bathytoma eximia Suter. Borsonia brachyspira Suter. Borsonia cincta (Hutton). Borsonia rudis (Hutton). Cerithiella fidicula Suter. Corbula canaliculata Hutton. Corbula pumila Hutton. Cucullaea sp. Cylichnella enysi (Hutton). Cymatium minimum (Hutton). Cytherea sp. Daphnella neozelanica Suter. Dentalium mantelh Zittel. Dentalium pareorense Pilsbry and Sharp. Dentalium solidum Hutton. Drillia laevis (Hutton). Epitonium elatum Suter. Epitonium rugulosum lyratum (Zittel) Erato antiqua Marshall. Euthria stirophora Suter. Exilia crassicostata Suter. Exilia waihaoensis Suter. Fusinus climacotus Suter. Fusinus modestus Marshall and Murdoch. Fusinus solidus Suter. Galeodea senex (Hutton). Gilbertia tertiaria (Marshall). Limopsis aurita (Brocchi).

Limopsis zitteli Ihering. Marginella conica Harris. Mitra hectori Hutton. Mitra inconspicua Hutton. Natica australis Hutton. Natica gibbosa Hutton. Natica zelandica Q. & G. Nuculana bellula (A. Ad.). Nuculana semiteres (Hutton). Pecten huttoni (Park). Pecten waihaoensis Suter. Sarepta solenelloides Marshall. Surcula antegypsata Suter. Surcula ordinaria Marshall. Surcula pareoraensis Suter. Surculu serotina Suter. Terebra sulcata Marshall. Trigonia ? sp. Triploca sp. Turbonilla antiqua Marshall. Turris aff. altus (Harris). Turris bimarginatus Suter. Turris complicatus Suter. Turris duplex Suter. Turris regius Suter. Turritella aldingae Tate. Turritella ambulacrum Sowerby. Turritella carlottae Watson. Turritella semiconcava Suter. Venericardia subintermedia Suter. Verconella nodosa (Martyn) var. extinct. Verconella turrita (Suter). Vexillum apicale (Hutton). Vexillum apicicostatum Suter. Vexillum linctum Hutton. Vexillum sp. Voluta corrugata Hutton. An analysis of this list of species is of particular interest from the point of view of a demonstration of the affinities of the Waihao fauna. The following summary gives an idea of these affinities: 17 per cent. of them have been found in the Hampden beds only; 44 per cent. occur in the ninety-six species of the Hampden beds as well as various Tertiary deposits; 43 per cent. occur among the 215 species of the Target Gully species; 10 per cent. are of Recent occurrence. These facts show how much more closely this fauna is related to the fossils of the Hampden strata than to those of Target Gully. In every one hundred species that have been found in the latter locality less than twenty have been found at the Waihao, while double this number of the Waihao species occurs among the one hundred species that have been found at Hampden. On the other hand, the percentage of species that occur at Target Gully is twice as great as the percentage of the Hampden species which occur there. These palaeontological results show clearly that the Waihao beds, though closely related to those at Hampden, are distinctly younger than them—a result that would be anticipated from the stratigraphy, and has already been stated as probable (Marshall, Trans. N.Z. Inst., vol. 52, p. 112, 1920). The number of Recent species is still so small that the beds should probably be considered as of Upper Eocene age. It is now agreed by all geologists who have studied the Oamaru district that there is no stratigraphical break beneath or above the limestone formation in that district. The study that we have made of the Waihao and of the Target Gully fossils strongly supports that conclusion. If the fauna of McCullogh's Bridge is a fair sample of the fauna that lived in the Oamaru area immediately before the deposition of the limestone, and if that of Target Gully is also a fair sample of the fauna that existed directly after that material had been deposited, we may rightly conclude that the deposition of the limestone occupied a long period. The time that elapsed was sufficiently long to allow of a large number of species, and even genera, becoming extinct, and of the development (or at least of the migration) of a large number of other species. We may now state with some probability of correctness that the deposition of the Oamaru

limestone commenced in the Upper Eocene and continued until after the commencement of the Miocene period, though correlation with European equivalents may be misleading. A comparison with the North Canterbury fauna is again suggested by these conclusions. In the typical Amuri limestone no molluscan fossils have yet been found, but in the Trelissick Basin the local representative formation contains a molluscan fauna that appears to be little older than that of Target Gully. Lately some Foraminifera have been found in the typical outcrop of the Amuri limestone, and Thomson states that Chapman, after examining these, has classed the Amuri limestone as of Danian age (Thomson, Trans. N.Z. Inst., vol. 52, p. 350, 1920). It is more than questionable whether the Foraminifera give a more reliable indication of the age of this formation than the Mollusca that were found in the Trelissick Basin. In the overlying Weka Pass stone eight species of Mollusca have been found; all of them are well-known species in the beds that lie above the Oamaru limestone, and most of them have a wide range, though Euthria media, Struthiolaria spinosa, Turris altus, and Dentalium solidum occur but rarely below the Oamaru stone. The following list gives the approximate occurrence of the eight species:— Euthria media: Pareora, Waikare, White Rock. Struthiolaria spinosa: Trelissick Basin, Kakahu (?), Pareora. Pecten huttoni: Hampden–Awamoa. Epitonium lyratum: Hampden–Target Gully. Turris altus: Otiake–Pukeuri. Dentalium solidum: Waihao–Pukeuri. Teredo heaphyi: Waihao–Target Gully. Limopsis aurita: Hampden–Pukeuri. Hutton mentions an additional nine species from the Weka Pass stone, and they too have an occurrence in strata that lie over the Oamaru stone and in some cases beneath it as well. They are as follows:— Scaphella elongata: Mount Brown and Awamoa. Epitonium rotundum: Brighton. Galeodea senex: Hampden–Awamoa. Pleurotomaria tertiaria: Oamaru stone. Aturia ziczag: Wharekuri–Oamaru stone. Identification doubtful. Lima laevigata: Waihola, Cobden, All Day Bay. Pecten williamsoni: Mount Brown beds, Tata Islands, Kawa. Pecten fischeri: Awamoa. Pecten beethami: Wharekuri–Awamoa. Thomson (Trans. N.Z. Inst., vol. 52, p. 355) mentions in addition three species of Brachiopods from the Weka Pass stone. They are as follows:— Aetheia gualteri: Curiosity Shop, Broken River, Waiareka. Pachymagas cottoni: Main and Upper Mount Brown limestone, Hutchinson's Quarry. Pachymagas huttoni: Maerewhenua limestone. An inspection of this list shows that the molluscan and brachiopod faunas of the Weka Pass stone point to an horizon that is certainly not lower than the upper part of the Oamaru stone, and it should therefore be correlated with that horizon. This opinion is based on long experience and many years' collecting in the Tertiary formations of New Zealand, during which time there has been abundant opportunity of gauging the stratigraphical position of various associations of fossils. Knowledge and evidence of this kind must surely be given greater importance than that

which is ascribed to the three species of Foraminifera which Thomson says have been identified by Chapman and are considered by him to indicate an Eocene age. Up to the present time Foraminifera have been collected but little in New Zealand, and unless the particular species referred to by Thomson have a most distinct Eocene occurrence and are absent in all other deposits in New Zealand little importance can be attached to them; and even if these conditions are fulfilled it is doubtful whether the indication of age given by them can stand against that given by the Mollusca and brachiopods, until at least far more extensive collections of Foraminifera have been made in New Zealand. In the face of such definite indication that the Weka Pass stone and the upper part of the Oamaru stone are of the same geological horizon, Morgan still classes the Weka Pass stone as Eocene and the Oamaru stone as Miocene (N.Z. Geol. Surv. Pal. Bull. No. 8, p. 101, 1921). Speight and Wild have conclusively shown that the Amuri limestone and the Weka Pass stone have a conformable contact (Trans. N.Z. Inst., vol. 52, pp. 87, 88, 1918), and this makes it necessary to correlate part of the Amuri stone with the Oamaru stone.