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Volume 51, 1919
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Art. XIII.—A Fossiliferous Bed at Kawa Creek, West Coast, South of Waikato River, New Zealand.

[Read before the Auckland Institute, 20th December, 1918; received by Editor, 30th December, 1918; issued separately, 26th May, 1919.]

Whilst on a hurried trip from Port Waikato to Raglan early in 1917 the writer observed at the coast near Kawa Creek, about fourteen miles south of the Waikato River, a very interesting section in the Tertiary succession, and discovered a fossiliferous bed that had escaped the notice of earlier geologists examining the coast section. He was able later to spend about a day and a half collecting from this bed, in which he found molluscan fossils in great numbers, but very fragile and without great variety. No doubt, however, further collecting will add greatly to the present list of fauna. Even though incomplete, this list shows many points of interest, and the object of this note is to illustrate these, and to publish some facts in connection with the more recent geological history of the Kawa Creek district that may have more than local interest, and help to throw light upon the mutual relationships of the later Notocene beds of a wide diastrophic district.*

Résumé of the Geology of Kawa CheekPort Waikato District.

The oldest rocks exposed in the area studied are Mesozoic shales, sandstones, and local conglomerates, best exposed in the vicinity of Port Waikato. They are disposed in a somewhat irregular asymmetrical anticline of which the axis is situated about half a mile east of the coast-line, to which its strike approximates. The western limb is the steeper, the dips there varying from 20° to 50°, whilst the strikes, unless where local complications occur, range approximately from north-west to N. 5° E. In the core of the anticline appear dark-grey to black marine shales with locally abundant belemnites, moderately frequent pelecypods and brachiopods, and occasional gasteropods. Above these are well-bedded alternating sandstones and shales, with minor conglomerate, in which plant-remains are ubiquitous, and which furnish one of the best collecting-grounds for Mesozoic plants in New Zealand. The late Dr. E. A. Newell Arber has recently described the flora as Neocomian in age.

Resting discordantly upon the eroded edges of the Neocomian are limestones of the Notocene, usually fairly pure, but sometimes very marly. Near their base they are strongly algal, and contain abundant fragments of the Mesozoic shales, a fact well shown near the mouth of the Huruwai Stream on the coast section. What fossils have been collected from these limestones have their analogues in the Oamaruian of other parts of New Zealand. Warping, minor folding, and some faulting have caused the

[Footnote] * J. A. Thomson, Diastrophic and other Considerations in Classification and Correlation, and the Existence of Minor Diastrophic Districts in the Notocene, Trans. N.Z. Inst., vol. 49, pp. 397–417, 1917.

[Footnote] † E. A. Newell Arber, The Earlier Mesozoic Floras of New Zealand, Palaeontological Bulletin No. 6, N.Z. Geological Survey, 1917.

[Footnote] ‡ Dr. J. A. Thomson very kindly examined the brachiopods for the writer.

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corresponding basal portions of these Oamaruian limestones to appear at very unequal heights above sea-level, whilst from many areas they have been removed by erosion, leaving the Mesozoic rocks exposed. The pre-Oamaruian surface of these last can only be surmised, for the evidence obtained is inconclusive, but it certainly appears to have possessed the broadness and simplicity so noticeable in the pre-Notocene surfaces of other parts of New Zealand.*

Whatever may have been this surface, upon it was deposited the basal limestone, and then a sequence of marls, blue sandstones, and impure finegrained limestones. Then came the gentle folding, or warping, with the accompanying minor faulting that has already been noted—movements that probably accompanied a period of relative land-elevation, evidenced near the Kawa Creek by the sharp planation of the edges of the upper beds of the Notocene sequence either by marine or subaerial erosion. The reverse swing of the oscillation now caused this surface of planation to be covered up by the fossiliferous marine sands that furnish one of the main objects of this article. Their fossils show that they are practically the uppermost Notocene, and it is probable that they are comparable with certain massive sandstones, discovered recently by Dr. Henderson in the Te Kuiti district, which unconformably overlie the upper beds of the Tertiary sequence in that area.

The closing members of the succession at the Kawa are not without interest, and may now be given. Unconformably above the fossiliferous sands is a local basaltic accumulation (both lava and agglomerate), followed by about 30 ft. of fresh-water silts, in which are intercalated a few thin, impure lignite-seams. Above these is a similar thickness of sands which appear to be wind-bedded; then a bed of pumice silt—itself a most interesting discovery—which is followed by ancient dune sands rising to a height of nearly 400 ft. above sea-level, and more or less continuous north-west to Port Waikato.

Details of the Coastal Section near Kawa Creek.

Without entering upon a discussion of the relative merits of different lines of evidence in the correlation of the New Zealand Notocene beds, or of the vexed question of the substantial conformity or otherwise of these strata, the writer considers that in the instance he is describing the mutual stratigraphic relations of the beds have a very real importance. The physical unconformity is very marked, and if it is coeval with that described by Dr. Henderson in the Te Kuiti district it will no doubt serve a useful purpose in the classification of the latest Notocene strata of a wide district, if not of New Zealand. It seems desirable, therefore, to set forth in greater detail the observed section near the mouth of the Kawa Creek in which this unconformity is evident.

It may be remarked, further, that there is a very definite disconformity evident in the sea-cliffs immediately south of the Waikawau Stream, which is several miles north of the Kawa Creek, but this is in beds much below those at the latter locality.

[Footnote] * See, for example, C. A. Cotton, The Structure and Later Geological History of New Zealand, Geol. Mag., dec. 6, vol. 3, pp. 243–49, 314–20, 1916.

[Footnote] † J. Henderson, The Geology of the Te Kuiti District, with Special Reference to Coal Prospects, N.Z. Journ. Sci. Tech., vol. 1, p. 114, 1918.

[Footnote] ‡ J. Henderson, loc. cit.

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Amongst the lower beds of the observed section at the Kawa Creek locality are a series of thin greensand bands alternating with strong flaggy glauconitic limestone layers up to 1 ft. in thickness, the whole comprising a stratum about 15 ft. in depth, which strikes north and south and dips westward at approximately 15°. A normal strike fault traverses the section, accompanied by two lesser faults, and somewhat complicates its interpretation. This fault has a throw varying up to about 40 ft., and dips steeply eastward.

Above the flaggy bands are bluish-white calcareous mudstones exposed for approximately 50 ft. of height in the sea-cliffs; they strike nearly north and south, and dip gently (at approximately 8°) westward. They are poorly fossiliferous, showing macroscopically merely a few sporadic Foraminifera and molluscs: Crepidula monoxyla (Less.) was the only specifically determinate mollusc collected. The greensand and flaggy calcareous bands just beneath contain very abundant Foraminifera and occasional distorted brachiopods. The former have been forwarded to Mr. F. Chapman, of Melbourne Museum, but his report upon them is not yet available.

If one may judge from a rather limited number of fossils, mainly pelecypods, brachiopods, and echinoids, in beds of the same sequence but at a lower horizon, both sets of beds so far described—the flaggy bands and overlying mudstone—are probably Middle or Upper Oamaruian in age.*

The gently upturned edges of these beds are now most regularly truncated by an erosion-plane, rising from approximately 50 ft. above sea-level at the coastal section south of the Kawa Creek to about 80 ft. just north of the mouth of the Kawa, about half a mile distant. From its extreme regularity it would appear to be a result of marine planation, and it is clearly to be noted that this followed the gentle folding or warping and faulting which have just been described as apparent in the coast section.

On the erosion surface rest yellow to bluish sands crowded with casts or actual shells of molluscs, a few bryozoans, corals, and other organisms. Near the base the remains are moderately well preserved, and have furnished the collection made by the author and listed in this paper. In depth these sands reach about 40 ft. They cannot be followed northward from the section now described, but what appears to be the same bed can be seen near where the coastal route regains the coast a mile or so southwards after deviating inland to avoid some impassable basalt sea-cliffs, and again still farther south.

Here they have been disrupted by this basalt and overlain by columnar lava. At the more northerly locality, similarly, other lava or agglomerate rests on a locally irregular erosion surface of the fossiliferous sands, the agglomerate showing considerable variation in thickness, in places thinning to 1 ft. or so, in others thickening to as much as 20 ft. Close by is exposed part of the somewhat complex vent of the volcano, whence came this material, and whence poured forth a flood of basaltic lava reaching probably several miles westward, for a small islet more than a mile from the shore appears to be basaltic. The columnar jointing of the flow renders it an easy prey to the great waves characteristic of this exposed coast.

[Footnote] * Dr. J. A. Thomson, who examined the brachiopods, reports that they are certainly Oamaruian.

[Footnote] † Hutton observed these beds and noted their unconformable relations to the underlying beds, but failed to obtain any marine fossils in them. He tentatively correlated them with the Waitemata sandstones, but suspected that they might be much younger. (F. W. Hutton, On the Relative Ages of the Waitemata Series and the Brown Coal Series of Drury and Waikato, Trans. N.Z. Inst., vol. 3, pp. 244–49, 1871.)

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Above the volcanic material come grey and white silts with impure lignite bands, all apparently of fluviatile origin, for they show good current-bedding in places. There is a depth of 30 ft. of these silts, which are then succeeded by an equal thickness of consolidated iron-stained sands, probably of dune origin; and again above these there is a most interesting bed, 10 ft. to 20 ft. in depth, of pumice silts, also evidently of fluviatile origin.

A succession of dune-sands, rising to approximately 350 ft. above sea-level, and deeply stained and cemented by concretionary limonite, completes the section.

All these beds above the fossiliferous sands are undoubtedly Noto-pleistocene in age, and, though of considerable interest, are beyond the scope of this paper, which is chiefly concerned with the fossiliferous sands.

List of Mollusca from the Fossiliferous Sands.

The Mollusca listed below come from near the base of the fossiliferous sands, and within a few feet, therefore, of the unconformity duly noted in the Kawa section. The identifications in nearly all cases were made or checked by the late Mr. H. Suter. For convenience of reference the genera are arranged in alphabetical order in the list. Recent species are preceded by an asterisk.

  • Ancilla hebera (Hutt.).

  • *

    Ancilla novae-zelandiae (Sow.).

  • *

    Anomia cf. huttoni Sut.

  • *

    Arca novae-zelandiae Smith.

  • Arca subvelata Sut.

  • *

    Barnea similis (Gray).

  • *

    Calyptraea maculata (Q. & G.).

  • *

    Cardita calyculata (L.).

  • *

    Chione mesodesma (Q. & G.).

  • Chione meridionalis (Sow.).

  • *

    Chione spissa (Desh.).

  • Circulus cingulatus Bartrum.§

  • Crepidula gregaria Sow.

  • *

    Crepidula monoxyla (Less.).

  • Crepidula striata (Hutt.).

  • *

    Dentalium ? huttoni T. W. Kirk.

  • *

    Dentalium pareorense Pilsbry and Sharp.

  • *

    Dentalium solidum Hutt.

  • *

    Diplodonta zelandica (Gray).

  • *

    Divaricella cumingi (Ad. & Ang.).

  • *

    Dosinia anus (Phil.).

  • *

    Dosinia caerulea (Reeve).

  • *

    Dosinia magna Hutt.

  • Drillia aequistriata Hutt.

  • *

    Drillia laevis (Hutt.).

  • *

    Emarginula striatula Q. & G.

  • Fulgoraria sp.

  • Glycymeris globosa (Hutt.).

  • *

    Glycymeris striatularis (Lamk.).

  • *

    Gomphina maorum Smith.

  • *

    Hipponix antiquatus (L.).**

  • *

    Leda bellula A. Ad.

  • Lima colorata Hutt.

  • *

    Loripes concinna Hutt.

  • *

    Mactra discors Gray.

  • *

    Mactra scalpellum Reeve.

  • Marginella ? harrisi Cossm.

  • *

    Marginella pygmaea Sow.

  • *

    Murex zelandicus Q. & G.

  • *

    Myodora antipodum Smith.

  • *

    Natica australis (Hutt.).

  • *

    Natica zelandica Q. & G.

  • *

    Nucula hartvigiana Pfr.

  • *

    Nucula nitidula A. Ad.

  • Olivella neozelanica (Hutt.).

  • Ostrea, several sp.

[Footnote] † J. A. Thomson, loc. cit.

[Footnote] ‡ It is perhaps permissible to point out that the pumice silts offer strong evidence that the Waikato or some such river flowed westward to this portion of the coast in early Notopleistocene times, bringing the pumice from the central rhyohtio country. Pumice terraces of corresponding height above sea-level are described by Henderson on the banks of the Waikato River near Cambridge (J. Henderson, N.Z. Journ. Sci. & Tech., vol. 1, pp. 112–15, 1918).

[Footnote] § Described in this volume (p. 97).

[Footnote] ∥ Two specimens, small, incomplete at anterior end, come near D. huttoni, but ornamentation shows more numerous longitudinal ribs than in the type

[Footnote] ¶Not before recorded fossil

[Footnote] ** New to fauna.

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  • Paphia curta (Hutt.).

  • Pecten williamsoni Zittel.

  • Pinna sp.

  • Polinices ambiguus Sut.

  • *

    Polinices amphialus (Watson).

  • Polinices ovatus (Hutt.).

  • Polinices sagenus Sut.

  • *

    Protocardia pulchella (Gray).

  • *

    Psammobia lineolata Gray.

  • *

    Psammobia stangeri Gray.

  • Siphonalia costata (Hutt.).

  • Siphonalia kawaensis Bartrum.

  • Siphonalia propenodosa Bartrum

  • *

    Spisula aequilateralis (Desh.).

  • *

    Spisula aequilateralis gilberti Bartrum.

  • *

    Spisula ordinaria (Smith).

  • Struthiolaria sp.

  • *

    Tellina alba Q. & G.

  • *

    Tellina glabrella Desh.

  • *

    Tellina huttoni sterrha Sut.

  • *

    Tellina spenceri Sut.§

  • *

    Tellina urinatoria Sut.

  • Terebra benesulcata Bartrum.†

  • *

    Tugalia bascauda Hedley.

  • *

    Tugalia intermedia (Reeve).

  • Tugalia kawaensis Bartrum.†

  • Turbo postulatus Bartrum.†

  • Turris duplex Sut.

  • Turritella huttoni Cossm.

  • *

    Tugalia symmetrica Hutt.

  • *

    Venericardia difficilis (Desh.).

  • *

    Venericardia lutea (Hutt.).

  • *

    Venericardia purpurata (Desh.).

A critical examination of this list shows the following facts: Including new ones, seventy-four species have been identified, four of them doubtfully so, and in addition three genera represented, one of which has no living representatives. Forty-six of the species are still living—a percentage of 62; one of these—Hipponix antiquatus (L.)—is new to the New Zealand fauna, whilst three are recorded fossil for the first time. There are six new species and one new variety.

A considerable amount of information about the upper Notocene fossils probably awaits publication by the New Zealand Geological Survey, but, depending upon literature now available, the writer finds that as many as sixteen of the twenty-nine extinct species have not previously been described from beds higher than the Awamoan stage. Eleven species are found fossil only in the Wanganui and Petane beds, or are Recent species now first recorded fossil, and one more—Dosinia anus (Phil.)—is known only from Pliocene beds elsewhere in New Zealand.

Dr. J. A. Thomson, Director of the Dominion Museum, who has available for comparison many unpublished identifications of fossils from North Otago and South Canterbury made by the late Mr. H. Suter, very kindly compared the Kawa faunal lists with those of the various typical Canterbury, North Otago, and other localities, and reported as follows: “I find that forty-seven of your species are known from the Awamoan or lower beds, while twenty-three are not.** These twenty-three include, of course, all the new species, and the remaining seventeen are all Recent species with the exception of Drillia aequistriata Hutt., Olivella neozelanica (Hutt.), and Polinices ambiguus Sut. The last species I cannot trace; the two former are certainly Wanganuian.”††

[Footnote] † Described in this volume (pp. 96–100).

[Footnote] ‡ Not before recorded fossil.

[Footnote] § The late Mr. Suter informed the writer that he obtained a specimen of this shell in a collection from Poverty Bay made prior to 1874 (locality No. 60 of the New Zealand Geological Survey). Otherwise it was formerly unknown fossil.

[Footnote] ∥ Wanganui system (Pliocene) of Marshall (New Zealand and Adjacent Islands, Handbuch der regionalen Geologie, 1911).

[Footnote] ¶ H. Suter, Manual of the New Zealand Mollusca, 1913.

[Footnote] ** Species doubtfully identified are omitted.

[Footnote] †† Personal communication.

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It appears evident from these considerations that the fauna is intermediate between the Awamoan and Wanganuian. It is unfortunate that the beds immediately below the unconformity at the base of the fossiliferous sandstones at the Kawa locality are so poorly fossiliferous, since their exact correlation is a matter of great importance, and in addition a good idea could then be gained of the relative importance of the above-mentioned unconformity.

In conclusion, it is necessary only to point out once more the probability of the wider occurrence of beds of the same age as the above in the district. An example probably even now is furnished by certain sandstones overlying unconformably the upper beds of the Tertiary sequence near Te Kuiti.*

[Footnote] * J. Henderson, The Geology of the Te Kuiti District, with Special Reference to Coal Prospects, N.Z. Journ. Sci. Tech., vol. 1, p. 114, 1918.