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Volume 49, 1916
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Art. XXXVI.—Geology of the Central Kaipara.

[Read before the Otago Institute, 5th December, 1916; received by Editors, 30th December, 1916; issued separately, 30th November, 1917.]

Plates XXXII, XXXIII.

The discussions that have so frequently taken place in regard to the age of the lowest strata of the younger rock series of New Zealand have often involved statements as to the stratigraphy of those outcrops that occur in the north of the Auckland Province. The most recent of these statements have been made by Park,* Morgan, and Marshall. The first of these geologists, in accordance with his later views in regard to the stratigraphy of New Zealand, believes that there are Cretaceous and Tertiary formations. The Cretaceous formation is supposed to terminate at the horizon of the top of the so-called hydraulic limestone, the southern equivalent of which is the Amuri limestone. Morgan appears to adopt a similar view, though he does not make any precise statement. Marshall describes some points in the palaeontology of the limestones of this district. He shows that the lowest limestone (Whangarei type), generally admitted to be near the base of the formation, contains a large amount of Amphistegina, and that its characters in general are those of the so-called Miocene limestones of New Zealand. On the other hand, the formation known as the hydraulic limestone, a large part of which is not really calcareous, is shown to be a Globigerina ooze when it has a calcareous nature.

Since it appears that no collection of mollusca has been made in this locality for nearly twenty-five years, it was considered advisable to visit it and to study the stratigraphy so far as time would permit, and to collect all the mollusca that could be found. The author has now visited the locality on three occasions with those objects in view, and this paper embodies the results of his work.

The shore of the Kaipara Harbour between Port Albert and Matakohe is the portion of the district on which the observations have been made, for it is on this portion that earlier workers have found those sections on which their conclusions have been based. The general physiography of Kaipara Harbour is well known. The inlet penetrates deeply into the land and ramifies far into the ranges of hills along several drowned valleys. Several of these drowned valleys have deep-water channels, and in places the depth is as much as 20 fathoms. The arms of the harbour are generally bordered by cliffs, which rise in places to 100 ft.; but in many localities there are extensive mangrove flats, and the lines of cliff are much interrupted by the full development of mature stream-valleys which are tributary to the drowned valleys now forming the main arms. The whole topography is thus that of a maturely dissected lowland much depressed and drowned but the depression took place at a time sufficiently remote to allow of considerable cliff-erosion on the sides of the inlets that were formed by it.

[Footnote] * J Park, Geol Mag, dec. v, vol. 8, 1911, p. 546; also vol. 9, 1912, p. 493.

[Footnote] † P. G. Morgan, 10th Ann. Rep N.Z. Geol. Surv., 1916, p. 11.

[Footnote] ‡ P. Marshall, The Younger Limestones of New Zealand, Trans. N.Z. Inst., vol. 48, 1916, pp 87–99 (see p. 91)

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The rock structure is at once seen to be dominated by the development of white sediments that appear to be limestones, though it is found on a closer examination that many of these rocks are highly siliceous and that they are associated with marls, mudstones, and sandstones. There are also volcanic tuffs and lavas to a more restricted extent. The distinct has been greatly disturbed by earth-movements, and the rock outcrops show much folding, and probably faulting has taken place. There is also much and rapid change in the direction of the strike of the rocks, which necessarily greatly increases the difficulty of the stratigraphical problems.

The only parts of the district that were closely examined were the following: (1) Otamatea Arm from Komıti to one mile and a half above Batley; (2) Arapaoa Arm to one mile above Pahi; (3) Pahi Arm; (4) Oruawharo Arm from Port Albert to Oneriri. (See fig. 1.) The information gained from observations within this area cannot be regarded as in any way complete, though some general conclusions were arrived at. It appears that the lowest rock in the district examined is the limestone of the Gibraltar Rocks, in the Pahi Arm. This was also Park's conclusion. This limestone has often been correlated with the Whangarei limestone and with the Waiomio limestone. In the last locality, near the Kawakawa coal-mine, in the Bay of Islands, a bore showed that this type of limestone occurred very nearly at the base of this younger series of rocks and certainly below the hydraulic limestone.* Above this Whangarei limestone there is a series of marls and mudstones which is perhaps 500 ft. thick, at any rate in the Pahi Arm. Interstratified with the marls there are some bands of limestone not very different from that of the Gibraltar Rocks, and, like it, containing some glauconite. In places the glauconite forms thick beds of greensand, especially in the Pahi neighbourhood. Locally this greensand appears to give place to some very soft marly mudstones, which are of special importance in the Otamatea Arm half a mile to the north-east of Batley, and on the Arapaoa Arm two miles to the north-west of Batley. In the Pahi Arm it appears that some Globigerina limestone, called generally “hydraulic limestone,” occurs beneath the greensand, for it is in this material that the bands of Whangarei limestone already mentioned are found. This Globigerina limestone is highly arenaceous and contains a good deal of glauconite, but in places it is siliceous. Occasionally this siliceous character is shown in the presence of flinty bands, though typical rounded flints are seldom found.

The main mass of the “hydraulic” or Globigerina limestone is found above the greensands. This relationship is particularly clear near Pahi, on both the Arapaoa and the Pahi Arms. The greater part of this limestone is composed of broken tests of Globigerina (Plate XXXII, fig 3), but in places it contains a great number of sponge spicules and marine diatoms and radiolaria (Plate XXXII, figs. 1, 2). This is markedly the case at the main bluff at Batley and at Kaiwaka. In the upper part of this formation extremely fine sediment makes its appearance and the organic contents dwindle. The fine-grained sediment consists almost entirely of very minute grains of quartz, well rounded, and seeming therefore to owe their transport to aeolian influences rather than to those of water. This material forms the top of the Batley Cliff, Paukıhi, and also the whole of the cliff on the opposite side of the Arapaoa Arm. On the foreshore of this cliff and farther to the

[Footnote] * J. Hector, Progress Report, N.Z Geol Surv., 1892–93, 1894, p. xv, section A B, opp. p. xii.

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Fig. 1.—Siliceous organisms of ooze, Paukıhi × 22
Fig. 2.—Siliceous organisms of ooze, Paukıhi. × 110.
Fig. 3.—Microsection of Globigerina ooze, Batley Wharf × 22.

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Fig. 1—Kossmaticeras tenuicostatum n sp × [ unclear: ] .
Fig 2—Kossmaticeras zelandicum n sp Nat size
Fig 3—Lytoceras sp Nat size
Fig 4—Panopea worthingtoni Hutton Nat si/c.

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south this white material becomes somewhat harder, and then is succeeded rather abruptly, but along an uneroded stratification-plane, by a dark-grey marly bed. Forty yards farther along the foreshore these beds are succeeded along another parallel stratification-plane by a more arenaceous bed with some tufaceous material. These beds form the prominent Pakaurangi Point at the north-west end of the Funnel. In previous reports this point has been generally called Komiti Point, and the beds of which it is formed have been called the Komiti Point beds. This, however, is a misnomer, and it is likely to lead to much confusion, as Komiti is at the other end of the Funnel and is now the location of a considerable settlement of fruitgrowers.

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Fig. 1.—Map of Central Kaipara.

These Pakaurangi Point beds, under the name of the Komiti Point beds, have been correlated with the Waitemata series of Auckland, which is referred to the Miocene period. The stratification of these beds is much disturbed on both sides of the Funnel. The upper members, especially as seen on the south side of the Funnel, have a highly variable strike, and they are composed of coarsely tufaceous material, amongst which are numerous fragments of hydraulic limestone. The presence of these fragments does not, in the opinion of the author, imply erosion of the limestone before the Pakaurangi beds were deposited. Their occurrence in this tufaceous material is rather due to volcanic action, which was extremely

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violent whilst the land was still submerged and sedimentation was still in progress. Evidence of this is found at Mohınui, which is a volcanic neck. It is here clearly seen that water penetrated into the crevices of the volcanic rock and caused its sudden solidification in the vitreous state. It is also noticeable that the scorıaceous volcanic matter round this neck is quite unoxidized. This inclusion of fragments of sedimentary beds in the volcanic material of submarine eruptions is well seen at Cape Horn, on the western shore of the Manukau Harbour. Here large masses of the Waitemata beds are included with the andesitic volcanic matter deposited by contemporaneous volcanic eruption.

There appears to have been a centre of volcanic activity near the western entrance of the Funnel, for a large mass of andesitic lava occurs here. The rock is a typical hypersthene-andesite. On the shore opposite to Pakaurangi Point the rocks have been violently disturbed, hydraulic limestone, “Waitemata beds,” and volcanic lava being closely associated. The only visit paid to this locality took place at high tide, and the details could not be observed. It is probable that the formation would be uncovered at low tide to a sufficient extent to allow of an interpretation of the structure being found.

At this point there is a coarse conglomerate resting apparently with unconformity on the Pakaurangi beds. This conglomerate has an interest beyond the ordinary in that it contains some pebbles of a diorite which is not known to occur in place anywhere in this district. The nearest locality where plutonic rocks are definitely known to occur in place is Ahipara on the west side and Mangonui on the east side of the North Island respectively, but both of these places are some seventy-five miles distant.

In the series of rocks thus arranged no distinct stratigraphical break was observed, though this point is most difficult to decide because of the extent to which the rocks have been disturbed. Even at Pakaurangi Point, where the stratification is clear and the exposures continuous, there are some difficulties, and the strata are here clearly seen to be so disturbed as to change completely in strike and dip within very short distances.

Some previous observers have described several stratigraphical breaks in this rock series. S. H. Cox* in 1879 represented the hydraulic limestone as Cretaceo-Tertiary in age, while the limestone of the Gibraltar Rocks is classed as Eocene, and is represented as folded in a synclinal manner while resting on a highly eroded surface of the hydraulic limestone. However Cox correlates the limestone of the Gibraltar Rocks with the Waiomio limestone at Kawakawa. In that place, as mentioned earlier, a bore has clearly shown that the Waiomio limestone is lower in the series than the hydraulic limestone. Cox also places the fossiliferous beds of Pakaurangi Point (called by him Komiti Point) in the Miocene period, but he does not indicate precisely the stratigraphical relation between the Pakaurangi beds and the limestone of the Gıbra tar Rocks which he calls Eocene.

Park in 1885 classed the beds of Pakaurangi Point in the Eocene, but all the other strata in the district are classed in the Cretaceo-Tertiary. In 1887 Park reported further on the same district. The Pakaurangi (Komiti) Point beds are in this second paper placed in the Miocene. Most of the other strata are placed in the Cretaceo-Tertiary. However, the white clays

[Footnote] * S. H. Cox, Geology of the Rodney and Marsden Counties, Rep Geol Explor. dur 1879–80, 1881, pp 18, 19.

[Footnote] † J. Park, On the Kaipara District, Rep Geol Explor dur 1885, 1886, pp. 164–70.

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on which the Pakaurangi beds rest and the concretionary beds at Batley in which Inoceramus was recorded were classed in the Jurassic. A strong unconformity is indicated in a section showing the stratification of the Pakaurangi Point. This break is represented as occurring between the “chalky marls” (called in the present paper “white mudstones”) and the “Waitemata beds”* or tufaceous beds with fossils. The former of these beds are said to strike north-west and south-east and to dip 60° to the northeast, and the latter strike east and west and dip 20° south. Careful observations failed to support these statements. The white mudstones are traversed by numerous prominent joints which have nearly the bearings stated, and it appears that these have been mistaken for stratification-planes. The true stratification-planes are hard to distinguish, but when found it is seen that they strike 157° and dip 24° north-east. This result was obtained twice in different parts of the exposure at an interval of three years. The first of the observations was made in company with Dr. C. A. Cotton, of Wellington.

Some 150 yards farther south-east as seen on the foreshore close to Pakaurangi Point the mudstones acquire a bluish tint rather abruptly along a well-defined plane. The strike is here 120°, and 40 yards farther on, where the beds become more sandy and tufaceous (Waitemata beds of Park and Cox), the strike becomes 107°, and again the plane of contact shows no sign of erosion. Though this change of strike within the short distance mentioned may appear considerable and important, other variations as great are found in the Pakaurangi, or tufaceous, beds themselves. The strike here changes from 65° to 110° within a distance of 30 yards, and afterwards to 170°, with accompanying great changes in the dip, as shown in the map of the district. In order to see the stratigraphical facts mentioned the district must be visited at low tide.

At the extreme end of Pakaurangi Point there is considerable irregularity in the stratification. This is represented by Park as a fault. It might almost as well be represented as a disconformity. The beds here consist of tufaceous material and fine brecciated matter, and at the extreme point contain a large number of fossils of Miogypsina, which is also found below the disconformity. There are also some mollusca, such as Pecten aldingensis Tate, which are also common in the rest of the sandy beds between the sandy white mudstones and the point. The structure at the end of the point is therefore of very little importance.

McKay subsequently visited the district and reported a complete conformity from the Inoceramus beds to the top of the hydraulic limestone. He did not, however, visit the region of Pakaurangi Point.

The sequence of the younger rocks of New Zealand, so far as it is developed in the Central Kaipara district, appears to give no indication of such a break as is required to mark the dividing-line between two periods of sedimentation—that is, between two geological systems. Since the hydraulic limestone has always been correlated with the Amuri limestone of North Canterbury, it is natural in this place to review the additional observations that have been made in regard to the stratigraphical relation between this rock and the Weka Pass limestone which rests on it. It must again be stated that this is the dividing plane between Hutton's Cretaceous and

[Footnote] * J. Park, Kaipara and Wade Districts, Auckland, Rep. Geol. Explor. dur. 1886–87, 1887, pp. 219–29 (see esp p. 221, and section repeated, Geol. Mag., 1911, p. 546).

[Footnote] † A. McKAy, On the Geology of the Northern District of Auckland, Rep. Geol. Explor. dur 1887–88, 1888, pp. 37–57 (see p 54).

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Miocene, and within late years between Park's Cretaceous and Miocene also. Morgan, however, suggests that the rocks are of Eocene and Miocene age respectively. Additional evidence consists very largely in the rediscovery by Morgan* of a number of phosphatic nodules between the two rocks. Wherever the two rocks occur the one rests on the other without any change in dip or strike, and both are mainly foraminiferal. The phosphatic nodules are apparently regarded as rolled pebbles derived from some phosphatic stratum, which, however, has never been located. It would be much more reasonable to regard them as nodules formed on the sea-floor in situ. It is well known that such nodules are of relatively common occurrence in dredgings from water of moderate depth. From the Agulhas Bank several phosphatic nodules were dredged by the “Challenger” from depths of 98 and 150 fathoms. The form is capricious—generally rounded, but also angular. The concretions from the shallower depths were the larger (6 cm in diameter) and contained much more glauconite, and therefore possessed a green external appearance. The concretions are said to be more abundant along coasts where there are great and rapid changes of current, which cause frequent deaths of organisms. Merrill states that it seems probable that Cretaceous and Tertiary deposits have been formed under similar conditions in all parts of the world Stutzer also accepts the “Challenger” results as accounting for many phosphate deposits.§ F. W. Clarke, in the Data of Geochemistry, p. 104, describes the methods of formation of such nodules.

It thus appears that the phosphatic nodules are probably original marine deposits. Their occurrence implies rapid current changes, which are also implied by the replacement of the Globigerina ooze of the Amuri limestone by the arenaceous glauconitic limestone called the “Weka Pass stone” that rests on it. The phosphatic nodules occur just where they would be expected in a conformable rock succession deposited on a rising sea-floor.

The gritty limestone of the Gibraltar Rocks is similar in most respects to the hard bands in the hydraulic limestone in the Pahi Arm. As stated by Marshall in the paper previously referred to, the limestone of the Gibraltar Rocks consists mainly of Polyzoa, echinoderm fragments, and Foraminifera belonging to the following genera: Carpenteria, Globigerina, Rotalia, and Amphistegina. At Colbeck's Landing the rock is mainly mudstone, but on the west side there is a band of gritty limestone which contains many joints of stems of Pentacrinus. Some distance to the south-east of the landing, at the point B (fig 1), there is a thick mass of white limestone with a highly crystalline appearance. This appearance is due to the abundance of echinoderm fragments, and with these there are a few Foraminifera, mainly Globigerina. Some distance farther south, at C, there is some more limestone much silicified and apparently brecciated. Close to it there is a

[Footnote] * P. G. Morgan, 10th Ann Rep N Z Geol. Surv, Parl. Paper C-2B, 1916, pp 25, 26.

[Footnote] † J. Murray and A. Renard, Deep-sea Deposits, “Challenger” Reports, 1891, p. 391.

[Footnote] ‡ G. P Merrill, Non-metallic Minerals, New York, 1904, p. 264.

[Footnote] § O. Stutzer, Über Phosphatlagerstatten, Zeitschr. fur prakt. Geol., vol. 19, 1911. p. 7.

[Footnote] ∥ This has been stated definitely by Collet and Lee: “La glauconie et les concrétions phosphatées se forment actuellement sur le fond des mers…. Les concrétions phosphatées sont pour ainsi dire l'image du fond dans lequel on les rencontre ce qui prouve bien leur formation in situ” (Recherches sur la Glaucome, Proc Roy. Soc Edin., vol. 26, pt. 4, 1906, p. 266.)

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small outcrop of compact limestone. This rock consists almost solely of Globigerina. In the large bluff of hydraulic limestone at D there are three distinct hard bands of polyzoal limestone. The most northerly of these bands is mainly polyzoal, but there are numerous Foraminifera, including Amphistegina, Rotalia, Cristellaria, and Textularia, with some Globigerina. There are a few echinoderm fragments and much Lithothamnium. Of inorganic material there is a good deal of glauconite and a little quartz. The middle hard band 120 yards distant consists mainly of small Foraminifera, especially Globigerina, and a small Rotalia. There are only a few echinoid and polyzoan remains. Glauconite and quartz are in relatively large quantity. The southern band of this limestone consists mainly of Polyzoa. There are many echinoid plates and Forammınifera, amongst them Amphistegina, Globigerina, Textularia, Rotalia, and Carpenteria. There is a good deal of glauconite and of brown micaceous matter and small grains of quartz. There are also round grains of brown volcanic glass. The hydraulic limestone in which these bands are stratified consists mainly of Globigerina. Calcified sponge spicules are numerous. There are no other organic remains, but much glauconite, brown mica, and quartz.

Ammonite Beds.

These are mainly formed of a fine muddy substance of a peculiarly unctuous nature. It has a dark-brown colour, and its incoherence allows it to slip easily, and it therefore presents extremely poor exposures. Thus near Batley and to the south-east of Pahi, where these beds outcrop, the hillside is gradually slipping into the harbour, and well-developed outcrops are exceedingly hard to find. At a third locality on the north side of the Arapaoa Arm, about two miles from Batley, the material is more stable, though even here the hillside is gradually slipping downwards.

These beds contain a large number of concretions. Usually the concretions are merely portions of the country that contain a higher percentage of carbonate of lime. Microscopical examination shows that they consist mainly of fine quartz sand cemented with calcareous matter. There is a little glauconite, and much brown matter, apparently of vegetable origin. Some of these concretions are composed wholly of pisolitic spherules 2.5 mm. in diameter. The pisolites are composed of radiating crystals of calcite. The concretions are of very different shapes and of varying size, though few of them are more than 1 ft. in diameter. Cone-in-cone structure is often associated with them in all the localities where the beds outcrop. Near Batley the beds contain concretions which are far more glauconitic than elsewhere. I am at present wholly unable to give a satisfactory explanation of the origin and formation of these concretions.

Greensands.

These are best developed at Pahi and to the north-west of that township along the shore of the Arapaoa Arm. The sands are in places almost pure glauconite, but they appear to have been deposited in relatively shallow water, for at places they are finely conglomeratic. They contain many concretions the exterior of which has been largely converted into limonite. Several of these concretions near Pahi enclose a large variety of molluscan fossils, and in one of them Mr. J. A. Bartrum found a reptilian bone. The concretionary matter that contains fossils is particularly abundant at three localities—(1) Arapaoa Arm, on the north-east shore near Pahi; (2) Arapaoa

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Arm, south-west shore, opposite Pahi, at Coates's Landing, (3) Pahi Aim, opposite Pahi Township, near Jackman's. The greensand at these three places is clearly seen to lie below the main mass of the hydraulic limestone. Farther south the glauconitic nature of these sandstones seems to decrease and the brown sandstone next described takes its place.

These brown sandstones are of considerable thickness on the north side of the Arapaoa Arm at a prominent point two miles below Pahi. These sands contain very little glauconite, but, like the greensands, they are strongly concretionary. Amongst the concretions there are a few small ones of siderite. No fossils were found in any of the concretions in this brown sand. Near Batley this brown sand is exposed near the Maori settlement of Mateanui. It certainly lies below the ammonite beds in this locality, and appears to be separated from them by a bed of very siliceous hydraulic limestone.

Barite occurs from time to time in this rock series at various horizons Near Kaiwaka it has been found lying on the surface of the hydraulic limestone. A large concretion was found at the point B near Colbeck's Landing, and another was found in the ammonite beds on the north side of the Arapaoa Arm close to Pahi. It is, of course, a fact that concretions of barite have been found in some ocean dredgings. It is thought that the greensands, brown sand, and ammonite beds are practically the same horizon. It is certainly true that the ammonite beds are not older than the greensands, for near Batley there is a large angular boulder of greensand embedded in the ammonite beds. The angular nature of this boulder shows that it has been transported a very short distance, a consideration that is emphasized by the incoherent nature of the greensand, which does not bear transport. The boulder almost gives the impression of being merely a local phase of the ammonite marls. In the same ammonite beds there are many concretions that have the appearance of those that are so common in the greensands. Thus the impression is formed that the ammonite beds and the greensands are different local phases of the same formation.

Hydraulic Limestone

This name has been used for a number of strata that have a general similarity in appearance, though in composition they prove to be widely different. The name “hydraulic limestone” has apparently been applied to them under the impression that they are so constituted that they can readily be converted into hydraulic cement. This may actually be true with reference to a small portion of the strata known under this name, but it is wholly misleading with reference to the greater part of the formation. In the Pahi section, for instance, hydraulic limestones are represented by Park over the greater part of the distance between McMurdo's and Colbeck's Landing (loc. cit, 1887, p 222, and section). The Batley Heads are also said to be composed of hydraulic limestone (loc cit, p 229). A microscopic examination of these materials shows that the external similarity of the rocks actually conceals great differences in composition and structure.

In the Pahi Arm the beds near Colbeck's Landing are mudstones and sandstones almost destitute of calcareous matter. At Awakıno the material is a Globigerina limestone, but it contains a large amount of glauconite, quartz, and other impurities At Batley the small bluff near the wharf is a glauconitic limestone, but the material of the main bluff, Paukıhı, is almost wholly siliceous. Near the base it is very white and compact, but shows no organisms when examined under the microscope. In many places

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the hydraulic limestone is highly siliceous, and in places it is distinctly flinty. No organisms have been recognized in these flinty types. It cannot at present be definitely stated whether the flinty type occurs only at one definite horizon or whether there are several different flinty strata. A little higher up the cliff the rock consists mainly of Globigerina tests, but it also contains a great variety of diatom* and radiolarian remains, with an abundance of sponge spicules. In the rock from the upper part of the cliff no organic remains could be distinguished, and the rock is merely a white mudstone that consists almost entirely of very minute rounded particles of quartz.

On the north-west side of the Arapaoa Arm, near Pakaurangi Point, this series of rocks is continued. The continuation has already been described in demonstration of the fact that the unconformity described by Park between his chalk marls (actually white mudstones above the hydraulic limestone) and his Komiti Point beds (here called “Pakaurangi Point beds”) does not in reality exist. It is only necessary to repeat here that the white mudstones become dark-coloured and are finally succeeded by the tufaceous Pakaurangi Point beds without any sign of erosion.

Pakaurangi (Komiti) Point Beds.

These are moderately coarse sandy beds mainly composed of material of volcanic origin, and are therefore rightly described by Hector as tufaceous. As the beds are followed farther westward and southward the material becomes coarser and the sediments are in places breccia or conglomerate beds. The upper beds at the apex of Pakaurangi Point still have a species of Amphistegina and a great abundance of Miogypsina aff. irregularis (Orbitoides of Park), and is probably of Lower Miocene age.

It is well known that flint-beds are associated with the fine-grained Globigerina limestone—the so-called Amuri limestone of North Canterbury and Marlborough. An account of these has just been published by Thomson. In his article he states that “The absence of such skeletons [Radiolaria, sponges, and diatoms] in any of the numerous microscopic sections examined removes any ground for accepting such an explanation [organic source] for the origin of the silica in the present case…. In view of the widespread occurrence of the flint-beds, apparently at a definite horizon, the theory of original deposition [chemical precipitate] seems most acceptable.”

In a paper published last year I recorded the occurrence of Radiolaria in the Amuri limestone at Kaikoura and at the Amuri Bluff, in both of which localities there are some flints in the limestone. In addition, further instances of the occurrence of sponge spicules were recorded in the North of Auckland in the hydraulic limestone at Kaiwaka and at Port Albert. In the last locality the spicules were calcified. Also at Kaiwaka there is a diatomaceous and radiolarian ooze associated with the limestone. In addition, the present paper records the presence of Globigerina ooze with abundant Radiolaria and diatoms at Batley. The Globigerina limestone

[Footnote] * Mr J. H Grenfell, of Oamaru, has kindly mounted some slides of these diatoms. He says, “The following are the diatoms in these slides which appear similar to those from Oamaru: Actinoptycus, Coscinodiscus, and Triceratium.”

[Footnote] † J. A. Thomson, The Flint-beds associated with the Amuri Limestone of Marl-borough, Trans. N.Z. Inst., vol. 48, 1916, pp. 48–58 (see p. 56).

[Footnote] ‡ P. Marshall, The Younger Limestones of New Zealand, Trans. N.Z. Inst., vol. 48, 1916, pp. 87–99 (see p. 94).

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one mile north of Pahi also contains an abundance of calcified sponge spicules, and a re-examination of the limestone from Wellsford, and from Limestone Island, in Whangarei Harbour, shows that calcified sponge spicules are frequent in those rocks also.

Thus in this group of rocks, Amuri limestone and hydraulic limestone, which have always been correlated together, we have the following records of the occurrence of the skeletons of siliceous organisms:—

  • (1.) Diatomaceous and radiolarian ooze: (a) Kaiwaka, (b) Batley, (c) Oamaru (immediately beneath the polyzoal limestone).

  • (2.) Globigerina ooze with Radiolaria: (a) Kaikoura, (b) Amuri Bluff.

  • (3.) Globigerina ooze with sponge spicules usually calcified: (a) Pahi, (b) Kaiwaka, (c) Port Albert, (d) Wellsford, (e) Limestone Island, Whangarei.

It is thus evident that siliceous organisms have contributed to some extent in many localities to the material of the Amuri limestone and hydraulic limestone, and that at times the siliceous remains occur to the exclusion of all other material. It is certainly true that at Ward and in many other localities where the limestones have the hard siliceous character the remains of siliceous organisms have not yet been distinctly recognized. A further examination of the specimen from Ward seen after a study of the specimens from Batley makes it appear probable to me that diatoms and Radiolaria are present, though much calcified and much destroyed by solution. In all the localities of the hydraulic limestone that have been mentioned there are also pronounced siliceous and flinty horizons. In view of the very general occurrence of the remains of organisms with siliceous skeletons, and of the fact that in many of the occurrences much of the siliceous matter is calcified, it is natural to come to the conclusion that the silica of these flinty rocks has been derived from the solution of the skeletons of siliceous organisms.

The Auckland rocks called collectively hydraulic limestone appear to have the same stratigraphical position as the Amuri limestone — that is, there are Cretaceous fossils below and Tertiary fossils in the strata that rest on them. The presence of radiolarian remains in some of these South Island deep-sea rocks, and their similar stratigraphical position to the hydraulic limestone, which almost certainly owes its frequent siliceous character to organic skeletons, renders it probable that these South Island flinty rocks also owe their siliceous contents to organic remains. In the light of our present knowledge this explanation seems more in accord with those facts that we know than any hypothetical explanation based upon the precipitation of silica from oceanic water.

As thus described it will be seen that the whole series of younger rocks in this district has near the base a limestone which is largely composed of Foraminifera and is of relatively deep-sea orgin. For some time the sea in which this limestone was deposited remained of considerable depth, but the coast-line was sufficiently close to this locality to allow of the accumulation of much terrigenous matter. The amount of sediment varied, and from time to time it was reduced to such an extent and oceanic currents changed so far as to allow of the deposition of greensands. At times tests of Globigerina constituted the main portion of the deposit. During this time ammonites with the affinities of species belonging to the Senonian fauna were in existence, though the mollusca had something of a Cainozoic aspect. There are also hard bands of limestone at various horizons which contain species of Amphistegina and give to the formation more than ever a Tertiary aspect.

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After a great thickness of sediment had been accumulated on this sea-floor a further movement of depress on of an important nature took place, and a bed of Globigerina ooze of great thickness was formed. The depth of the water increased to such an extent that over the calcareous matter there was formed a stratum of diatomaceous and radiolarian ooze. When elevation took place again it appears that conditions were unfavourable to the life of Globigerina, and the diatomaceous ooze is succeeded directly by a fine white mudstone composed almost entirely of minute rounded particles of quartz. It is extremely difficult to suggest the exact origin of this material. The well-rounded form of the quartz certainly leads to the belief that the deposit was of aeolian origin. It may be of the same nature as the white clay, or white clay with ooze, now covering the sea-floor fifty miles distant from Cape Maria van Diemen on the western side of the North Island. There appears to have been very little life on the sea-floor at this time.

The elevation of the sea-floor continued gradually, and the deposit became marly. A varied molluscan fauna then appeared, and at the same time simple flabelloid corals and an abundant Miogypsina life. Volcanic action took place on many occasions. Volcanic glass is found in the hard limestone near Pahi. Marahemu Hill is formed of volcanic rock due to submarine activity, and, lastly, there are the great beds of tuff and the lava rocks at Komiti and on the south-east side of the Funnel. Further evidence of submarine volcanic activity is found in the large beds of tuff and breccia at Wayby and near Kaiwaka, where in the rock used for the railway ballast specimens of Amphistegina were found in microscopical preparations. Lastly, there is a small cone near Port Albert. The volcanic rock here is quite glassy, and though distinct proof was not found it seems that this material also was formed by submarine eruption.

Palaeontology.

The following rocks were found to contain fossils: (1) The gritty limestone at Gibraltar Rocks, and bands of similar material between that point and Pahi; (2) the hydraulic limestones; (3) the greensands near Pahi, (4) the mudstones with concretions near Batley, or ammonite beds; (5) the sandy and tufaceous beds near Pakaurangi Point. The gritty limestones of the Gibraltar Rocks have been described previously. The following genera of Foraminifera are represented: Carpenteria, Globigerina, Rotalia, and Amphistegina. No specific determinations were possible. In the absence of specific identifications it is not possible to state the exact horizon to which the limestone belongs, though the presence of abundant Amphistegina appears to point to the Miocene age. The same remarks apply to all the other bands of gritty limestone between the Gibraltar Rocks and Pahi.

The Ammonite Beds.

These marly beds contain relatively few fossils, though those that have been found have a peculiar interest. Up to the present time only five species have been discovered, and three of these are ammonites.

Kossmaticeras de Groussouvre, 1901.

This genus was established to include species derived from Pusozia and Uhligella which show a close similarity to Holcodiscus, though these types are supposed to owe their resemblance to phylogenetic convergence.

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Kossmaticeras zelandicum n. sp. (Plate XXXIII, fig. 2.)

Diameter, 75 mm.; thickness, 27 mm.

Last whorl only seen in the specimen for about half its extent. Ribs large and distinct, some 36 being developed in the half-circle. The ribs for the most part take their origin in tubercles situated on the border of the umbilical wall. The tubercles are 10 in number in the half-circle. There are a few ribs situated in the intervals between the tubercles. A few additional ribs arise half-way between the umbilicus and the siphon. These additional ribs are intercalated between those that arise on the umbilical wall. The ribs are crenulated some twelve times between the tubercles and the siphuncle. The suture-line is comparatively simple, and closely resembles that of K. karpadense, and loss closely that of K. bhawani Stoliczka.*

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Fig. 2.—Suture-line of Kossmaticeras zelandicum. × 3.

This species is closely related to K. antarcticum, described by Kilian and Reboul from Seymour Island, and to K. kalika Stohezka from the Arrialoor of India. From the former its ornamentation differs in its ribs and tubieles being more numerous. On the other hand, the ribs and tubeicles are both less numerous than in the Indian species. These two species are included by Kihan and Reboul in the subgenus Gunnarites. There appears to be no doubt that the present species should be placed in the same group, though it is sufficiently distinct to be regarded as a separate species.

In regard to the age that is indicated by the fossil the following statement of Kilian and Reboul (loc. cit., p. 64) may be quoted. “Les faunes etudiées qui appartionnent [ unclear: ] contestablement an type indopacifique du cretacé superieur (Neocrotacé) sont caracterisées par les Kossmaticeras” “Lesassises crétacées à Kossmaticeras antarcticum et Koss. bhavani de la terre de Graham, des îles de Snow Hill et de Seymom so placent sensiblement au même niveau que des couches de Quiriquina (Chili), les couches d'Algarobo, celles de Tejon group en Californie, les couches supérieures de Chico, les Phoenix and Henly Beds dans l'Oregon, l'assise de Nanaimo dans la Colombie britannique, les

[Footnote] * F. Stoliozka, Palaeontologia Indica, Cretacous Fauna of Southern India, vol. 1, pl. [ unclear: ] xix, fig. 7; also Kilian and Reboul, Les Cephalophodes [ unclear: ] , Wiss Erg [ unclear: ] . der swed. sudp. Exped. 1901–3, Bd. 3, Liof. 6, p 22, 1909

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Trichinopoly et Aryaloor Beds de l'Inde, les couches à Pachydiscus de Patagonie (Hauthal), correspondant à la grande transgression sénonienne qui parait avoir atteint également Bornéo et la Nouvelle Zélande.”

Kossmaticeras tenuicostatum n. sp. (Plate XXXIII, fig. 1.)

The only specimen is large, measuring 142 mm. in diameter and 45 mm. in thickness. Aperture oval. Shell extremely thin, ornamented with a large number of very fine ribs which are not bent in the siphonal region but they have a slight bond forward at the region about half-way between the siphuncle and the umbilicus. There are no umbilical tubercles. The

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Fig. 2.—Suture-line of Kossmaticeras tenuicostatum. × 1½.

suturo-line is complicated. It is but little different from that of Ammonites beudanti Brogniart from the Trichinopoly beds of India. (Pal. Ind., Cret. Ceph., pl lxxii). The suture-line shows a distinct resemblance to that of Kossmaticeras gemmatum Huppé, though there are considerable differences in detail. The ornamentation is, however, completely different from that of K gemmatum. (Kilian and Reboul, loc. cit., p. 22; Steinmann, Neues Jahrb. fur Min., &c., Bd. 10, 1895.)

Lytoceras sp. (Plate XXXIII, fig. 3.)

The only specimen of this genus is a fragment. The specimen measured 46 mm. in diameter and 18 mm. in thickness. Cross-section nearly circular. The specimen has been silicified, and that appears to have destroyed the external ornamentation, though in one portion it is still visible as a series of extremely fine ribs. The specimen consists of the body-chamber, but part of the next whorl remains, and on this a suture-line is distinct which has the typical character of Lytoceras. The species appears to be closely related to Am. (Lytoceras) cola Forbes from the Ootatoor of India. (Pal. Ind., loc. cit., pl. lxxv, fig. 5.)

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Fig. 4.—Suture-line of Lytoceras sp. × 7.

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Lamellibranchia.

Panopea worthingtoni Hutton. (Plate XXXIII, fig. 4.)

This specimen was identified for me by Mr. Suter. The species comes very near P. orbita Hutton. It is not uncommon in the Caınozoic rocks of New Zealand. It is recorded by Hutton from Lake Wakatipu and the Broken River.

Phacoides (Here) sp.

This specimen occurs as a cast only, and it has been classed for me by Mr. Suter. No other specimen of this genus has yet been recorded from New Zealand. In regard to the subgenus Here Cossmann remarks, “Ilest douteuse que ce sous-genre ait veçu dans l'Eocene.” (Cossmann et Peyrot, Conchologie de l'Aquitaine, 1911, livraison 2, p 687)

Inoceramus fragments (Park, Geol. Rep N.Z., 1886–87): I have found no remains of this genus.

This collection is of special interest. From a stratigraphical standpoint there hardly seems any room for doubt that this bed is of a higher horizon than the limestone of the Gibraltar Rocks. As stated earlier, this limestone contains a considerable amount of Amphistegina, and has other characteristics that cause Chapman to regard it as of Miocene age. A similar limestone almost at the base of the younger series of rocks at Waiomio is also stated by Chapman to be of the typical Miocene character. On the other hand, this ammonite bed lies distinctly below the hydraulic limestone. From a palaeontological standpoint the determination of the age of the beds offers much difficulty. It is clear that the ammonite fauna, poor as it is, clearly indicates a Senonian age. On the other hand, Panopea worthingtoni occurs widely in New Zealand in beds that are always classed as Tertiary, and generally as Miocene. This suggestion is apparently emphasized by the occurrence of Here. (A further collection has now been made, and many more species of ammonites, lamelıbranchs, and some gastropods have been found. These will be described subsequently) Hector placed these beds in the Cretaceo-Tertiary, Cox in the Lower Greensand, and Park agrees with Hector (?) that they are Jurassic.

The Pahi Greensands.

The fossils in these beds are in a bad state of preservation, and identification of the species has proved so difficult that no list can be given at present.

Pakaurangi Point Beds.

The beds at Pakaurangi Point have been long known to contain fossils. Hector collected some from here in 1876. Cox added to the collections in 1879. Park gave a list of some seventy forms in 1879, though in most cases the generic position only of the species was given. The following list contains the species collected in 1912 and in 1916 by myself, assisted by Mr. J. A. Bartrum. The material in which the fossils are embedded is a soft gray mudstone, and the specimens are for the most part in an excellent state of preservation. Fossils are most plentiful in the low cliffs on the western (or Funnel) side of the Pakaurangi Point. I am much indebted to Mr. H. Suter for identifying the species. Those marked * are Recent species.

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  • Vaginella n. sp.

  • *Emarginula striatula Q. & G.

  • Solariella stoliczkai Zittel.

  • Calliostoma n. sp.

  • Astraea subfimbriata Suter.

  • Turritella semiconcava Suter.

  • Turritella sp.

  • Cerithiopsis sp.

  • Struthiolaria cincta Hutton.

  • Crepidula gregaria Sowerby.

  • *Calyptraea maculata L.

  • *Natica zelandica Q. & G.

  • Polinices gibbosus Hutton.

  • Ampullina suturalis Hutton.

  • Epitonium browni Zittel.

  • *Epitonium zelebori Hutton.

  • *Trivia avellanoides McCoy.

  • Cymatium minimum Hutton.

  • *Phalium achatinum pyrum Lamarck

  • Galeodea senex Hutton.

  • Architectonica n. sp.

  • Helicus n. sp.

  • Fusinus kaiparaensis Suter.

  • Fusinus morgani Suter.

  • Dolicholatirus (Pseudolatirus) n. sp

  • Ptychatractus pukeuriensis Suter.

  • *Siphonalia dilatata Q. & G.

  • Siphonalia n. sp

  • Coptochetus n. sp.

  • Cominella carinata Hutton.

  • Phos n. sp.

  • Phos n. sp.

  • Alectrion socialis Hutton.

  • *Murex angasi Crosse.

  • Murex zelandicus Q. & G.

  • *Murex zelandicus komiticus Suter.

  • Cymbiola corrugata Hutton.

  • Cymbiola n. sp.

  • Cymbiola n. sp.

  • Cymbiola n. sp.

  • *Ancilla australis Sowerby.

  • Ancilla papillata Tate.

  • Ancilla n sp.

  • Ancilla n. sp.

  • Marginella conica Harris.

  • Marginella harrisi Cossmann.

  • Surcula climacota Suter.

  • Surcula fusiformis Hutton.

  • Surcula n. sp.

  • Surcula n. sp.

  • Surcula n. sp.

  • Surcula n. sp.

  • Leucosyrinx alta transenna Suter.

  • Turris n. sp.

  • Turris n. sp.

  • Drillia awamoaensis Suter.

  • Drillia imperfecta Suter.

  • Drillia n. sp.

  • Borsonia (Cordieria) n. sp.

  • Bathytoma haasti Hutton.

  • Bathytoma sulcata excavata Suter.

  • *Mangilia dictyota Hutton.

  • Conus armoricus Suter.

  • Conus (Leptoconus) n. sp.

  • Conus (Lithoconus) n. sp.

  • Terebra orycta Suter.

  • Acteon ovalis Hutton.

  • *Acteon craticulatus Muıdoch & Suter.

  • Crenilabium n. sp.

  • Cylichnella enysi Hutton.

  • *Dentalium ecostatum T. W. Kirk.

  • Dentalium pareoraense Suter.

  • Dentalium solidum Hutton.

  • *Cadulus delicatulus Suter.

  • Leda semiteres Hutton.

  • *Leda fastidiosa A. Adams.

  • Sarepta n. sp.

  • Anomia n. sp.

  • *Arca novae-zelandiae Smith.

  • Arca subvelata Suter.

  • Glycymeris subglobosa Suter.

  • Cucullaea alta Sowerby.

  • Cucullaea australis Hutton.

  • Mytilus n. sp.

  • Pecten aldingensis Tate.

  • Pecten burnetti Zittel.

  • Pecten huttoni Park.

  • Pecten n. sp.

  • Pecten n. sp.

  • Spondylus n. sp.

  • Lima colorata Hutton.

  • Ostraea wuellerstorfi Zittel.

  • Ostraea nelsoniana Zittel.

  • *Cardita calyculata Linné.

  • Venericardia subintermedia Suter.

  • *Thyasira flexuosa Mont.

  • *Tellina eugonia Suter.

  • *Tellina glabrella Deshayes.

  • Crossatellites attenuatus Hutton.

  • *Dosinia greyi Zittel.

  • Dosinia n. sp.

  • Macrocallista assimilis Hutton.

  • Macrocallista pareoraensis Suter.

  • Cytherea chariessa Suter.

  • Chione meridionalis Sowerby.

  • Paphia curta Hutton.

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  • Cardita (Glans) n. sp.

  • Chama huttoni Hector.

  • Corbula canaliculata Hutton.

  • Corbula kaiparaensis Suter.

  • *Corbula macilenta Hutton.

  • Corbula n. sp.

  • *Panopea zelandica Q. & G.

Of these 113 species only twenty-three are Recent, a percentage of 19.9. The genera Dolicholatirus, Coptochetus, Crenilabium, and Spondylus have not previously been found in the New Zealand fauna, fossil or Recent. The species Acteon craticulatus, Cadulus delicatulus, and Thyasira flexuosa have not previously been found fossil.

The rather low percentage of Recent species may be due to the northern locality, for it is probable that many species would tend to recede northwards as the climate became somewhat colder in the Pleistocene. The absence of littoral waters any considerable distance farther north would have caused some of these species to become extinct. This also may account for the presence of four genera which are now absent from the New Zealand fauna. The age of the Pakaurangi Point beds is probably about that of Target Gully if the suggestion made is regarded as valid so far as the extinct species are concerned.

Rocks of Igneous Origin.

Igneous rocks have been found in the following localities. The Otamatea Funnel, Mohinui (or Marahemu), Port Albert, Pukekaroro.

Conglomerates of the Otamatea Funnel.

A considerable outcrop of volcanic rocks is found on the south-eastern side of the Funnel. It appears to be in situ in this locality, though it was seen in the form of large boulders only.

This rock is moderately coarse, and shows feldspar crystals of considerable size in the hand-specimens. In section these crystals are found to be irregular, often zoned, and always twinned, showing in sections at right angles to the brachypinacoid an extinction angle of 30°, thus indicating a type of labradorıte. Many of the crystals enclose a great number of minute particles of glassy matter and of augite. Hypersthene is abundant in small well-formed crystals showing the usual pleochroism. In one case a crystal of hypersthene is mantled with a thin coating of augite. Augite is infrequent as compared with the hypersthene. The groundmass consists mainly of minute microlites of feldspar, but there are also many granules of augite and crystals of magnetite, which mineral is also often found enclosed in the crystals of hypersthene.

Mohinui, or Marahemu.

Mohinui is the name given on the Admiralty chart, but Marahemu is used on the Survey maps. The rock of which it is composed is black in colour, and it shows conspicuous crystals of feldspar, augite, and olivine.

In section the feldspar crystals are seen to be irregular, and they are occasionally in aggregates and show zonal structure. The species is labradorite, for the extinction angle in sections at right angles to the brachypinacoid is 32°. The augite is often in well-formed crystals, and is frequently twinned. It may reach 2.5 cm in diameter, and is of a greenish colour. Olivine is common, and the crystals are sometimes well formed. Most of them show serpentinization along crevices and along the borders. The groundmass is mainly feldspar in microlites. There is also much augite and magnetite.

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Port Albert.

A black rock, dense, and with an irregular fracture. The only mineral visible in section is feldspar in small sharp crystals. These are so fragmentary that it is impossible to identify them. The index of refraction is higher than that of Canada balsam. The feldspar crystals are bordered with dark margins of amorphous matter, as are the crystals in the glassy basalts of Savaii and similar vitreous basic rocks. The rest of the rock is brown glassy matter showing feathery crystallitic growths and incipient spherulitic structure. The rock has all the appearance of a basic glass, but the absence of olivine crystals suggests that it has the composition of an andesite rather than a basalt.

Conglomerates on the South Side of the Otamatea Funnel.

A large number of these boulders have in hand-specimens distinctly the appearance of plutonic rocks. The specimens vary somewhat in coarseness and in relative abundance of the ferro-magnesian constituent. The feldspar has no regular outlines, and the arrangement of the grains suggests a gneissic structure. There are many minute inclusions, and lamellar albite twinning is general. The extinction angle is 20°, and the refractive index 1–560. It is therefore a basic variety of andesine. Hornblende is very abundant in irregular ragged crystals. It includes much dusty ferruginous matter, and sometimes distinct crystals of magnetite. Pleochroism, green to straw-colour. The appearance of this hornblende suggests that it is of secondary origin. There is much magnetite and apatite.

No rock that closely resembles this has yet been found in situ in the North Island. It is quite different from the diorite of Mangonui and from the other plutonic rocks near Ahipara and Hokianga.

Pukekaroro.

This rock is light grey in colour, and is without any conspicuous crystals in hand-specimens. In section it is largely composed of short small crystals of feldspar with idiomorphic outline. The crystals are often polysynthetically twinned, and the angle indicates that they are andesine. In many cases they are zoned. The finer matter of the rock consists of colourless material which in some specimens has a most irregular form but in other slices is regularly quadrilateral. In all cases it has small inclusions of dark matter which could not be identified. I am indebted to Professor J. P. Iddings for pointing out to me that this mineral is quartz. When it has the irregular form its arrangement suggests the micropoecilitic structure described by Sollas in the dacites of the Coromandel Peninsula. The ferromagnesian mineral in this rock is completely chloritized, and the chlorite has much dusty magnetite associated with it. So far as the shape of the chloritic pseudomorph can be recognized, the original mineral appears to have been biotite. The rock must therefore be classed as a dacite.

The age of these igneous rocks cannot be very distinctly stated, and it is even unlikely that all the volcanic rocks are of the same age. The diorite is evidently derived from some relatively ancient rock-mass which has not yet been discovered in situ.

The Marahemu basalt constitutes a neck that traverses the hydraulic limestone in one of its flinty horizons. As the rock is glassy on the selvages and along the crevices, and at the same time the associated tuffs are not oxidized, it becomes probable that the eruption was of a submarine nature.

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Its intrusion was evidently subsequent to the deposition of the siliceous hydraulic limestone. The same remarks apply to the Port Albert rock, which forms a small neck about two miles to the east of Port Albert. The dacite of Pukekaroro forms a hill of considerable height which is a prominent point over the greater part of the central Kaipara, is surrounded by hydraulic limestone, and is certainly of later origin than that rock.

The hypersthene andesite of the Funnel was evidently emitted at the time of the deposition of the Pakaurangi beds or immediately afterwards. Small fragments of basic glass were found in the bands of polyzoal and Amphistegina limestone on the Pahi Arm. It is thus evident that volcanic activity was in progress whilst the deposition of the hydraulic limestone was taking place. There are also quarries for railway ballast on the line two miles south of Kaiwaka Station and near Wayby. The rock that is quarried is a volcanic breccia. It is black in colour, and at once gives the impression of formation under submarine conditions. This opinion is confirmed by microscopical examination, which reveals Foraminifera amongst the volcanic fragments. Amongst the Foraminifera is a specimen of Amphistegina. The tufaceous matter includes small greenish grains of augite similar to the augite of the Marahemu basalt It is thus evident that volcanic activity of an extensive nature took place in this district during and after the deposition of the limestone, for the breccia appears to rest conformably on a phase of the hydraulic limestone.