The Microfaunas of the Oxford Chalk and Eyre River Beds.
[Read before Wellington Branch, April 24, 1946; received by the Editor, May 7, 1946.]
Apparently the first mention of foraminifera in the Oxford Chalk was a statement by Hutton in 1885 (N.Z. Journ. Sci., vol. 2, p. 565), but no species were recorded until 1926, when J. B. Mayne sent some washings to Chapman. These were reported on in his “Cretaceous and Tertiary Foraminifera of New Zealand” (N.Z.G.S. Pal. Bull. No. 11, p. 12), and the age given as “Upper Cretaceous (Danian)”.
The Geological Survey still possesses the slides mounted for this bulletin by Chapman, and returned with lists of his identifications. These slides and identifications are in such a state that in most cases it would not be worth the time and trouble to make out a corrected list of the identifications in the bulletin; it is enough to state that over 90 per cent, are specifically erroneous, and far more than half generically so. In this particular case, however, it is of interest to quote the identifications made by Chapman, and also in each case what the material on his slide really is, since it represents a typical example of the evidence on which various chalks and marls from New Zealand were placed by Chapman as Cretaceous. The unchecked acceptance of this age for deposits such as the Amuri Limestone led to controversy by Marshall, Thomson, Speight, and others that has been needlessly prominent in our geological literature. I have referred briefly to the Oxford Chalk slide elsewhere (Trans. Roy. Soc. N.Z., vol. 69, pt. 1, p. 100; 1939), but the full details are as follows:—
“Haplophragmium aequale”—indeterminable tiny fragment.
“Bulimina rimosa”—(a) Anomalina aotea Fin., (b) broken fragment, probably of Sphaeroidina bulloides d'Orb.
“Bulimina brevis”—Sphaeroidina bulloides d'Orb.
“Pleurostomella subnodosa”—P. alternans Schwager.
“Nodosaria (D.) annulata”—Nodogenerina n.sp. A.
“Cristellaria cultrata”—Robulus glaucinus (Stache).
“Uvigerina maynei”—Uvigerina maynei Chap.
“Sagraina monile”—Nodogenerina n.sp. B.
“Sagraina striata”—Siphogenerina striatissima (Stache).
“Truncatulina lobatula”—fragment, probably of Cassidulina subglobosa Brady.
“Anomalina ammonoides”—(a) Nonion maoricum (Stache), smooth var. (b) Anomalinoides orbiculus. (Stache).
“Pulvinulina pauperata”—Laticarinina halophora (Stache).
“Pulvinulina elegans”—(a) Cibicides n.sp. aff. novozelandicus (Karr). (b) Cibicides n.sp. A.
“Rotalia soldanii var. nitida”—(a) Rotaliatina sulcigera (Stache). (b) Gyroidinoides allani (Fin.).
“Cassidulina subglobosa”—Rotaliatina, sulcigera (Stache).
Square 27 (not listed)—(a) Eponides ecuadorensis G. and M. (b) Cibicides n.sp. B.
Square 16 (not listed)—(a) Rotaliatina sulcigera (Stache). (b) Cassidulina subglobosa Brady.
Most of the squares on this and his other slides are occupied by single specimens, many with adherent easily removable matrix, heavily coated with gum, and frequently so fragmentary as to be indeterminable. The type specimens of Uvigerina maynei and Bulimina globocapitata have been noted by me elsewhere (Trans. Roy. Soc. N.Z., vol. 69, pt. 1, pp. 101, 112; 1939) to have adherent matrix which was described as part of the species; the type and all other specimens of Haplophragmium speighti Chap. (l.c., p. 28) are simply pieces of flinty matrix. The facts have to be faced that the scientific value of Pal. Bull. No. 11 is almost nil, and that no records taken from it are to be trusted, nor any of the ages allotted to the faunas. The revised identifications given above are sufficient in themselves to indicate that the age of the Oxford Chalk is Whaingaroan, i.e., Lower Oligocene, but, of course, a much larger fauna can and has been obtained from it, and will be listed later.
Before the actual fauna from this Chalk is recorded, the associated beds may be briefly dealt with. The Chalk appears to be an isolated deposit, for several samples from the plastic clay above it yielded no fauna, and the only fauna known below it is far down in the Eocene. Some six miles away is a Tertiary inlier known as Burnt Hill, which has yielded a fairly good fauna of both molluses and foraminifera; the macrofossils were originally thought to be Awamoan (Marwick, Rec. Cant. Mus., vol. 3, no. 7, p. 495; 1932), though several affinities with Tutamoe forms were noted; the microfauna conclusively points to correlation with the Upper Tutamoe, now known to be much younger than Awamoan, and referred to Upper Middle Miocene.
The Eocene fauna was first mentioned by Speight (Trans. N.Z. Inst., vol. 58, p. 419; 1928): “The discovery of Orthophragmina at a lower stratigraphical horizon than the chalk bed—approximately 600 feet below it—in a position where faulting on a major scale appears impossible, adds a new interest to the problem. Wherever Orthophragmina occurs in Europe or America it is regarded as an Eocene form, so a revision of the age of the chalk appears necessary.” Chapman examined material forwarded by Speight, and in conceding that “my former view of an Upper Cretaceous foraminiferal facies for the Oxford Chalk may have to be modified or abandoned” (Rec. Cant. Mus., vol. 3, no. 7, p. 483) recorded a fauna of seven species of Nummulites and Orbitoids: Assilina leymeriei (d'A. and H.), Heterostegina reticulata Rutim., Discocyclina speighti Chap. nov., D. novaezelandiae Chap. nov., D. dispansa (Sow.), D. archiaci (Schlumb.), and Asterocyclina stellata (d'Arch.).
Actually, it is probable that all these records refer to one or at the most two species. Schenck and Thalmann (Journ. Pal., vol. 16, no. 6, p. 781; 1942), in a review of a monograph on Orbitoids by Bronnimann, have noted that “Twenty years ago H. Douvillé pointed out that for identification of species the external features are of more
value than the inner structure. Recently J. Flandrin said that an exact specific determination based on thin sections alone is impossible.” Chapman's material (some of the original of which has been seen) was so badly decorticated and glauconitised that all surface features were obscured and almost all specimens badly broken; his microphotographs show no significant internal, differences. Miss Crespin has indicated (Proc. Roy. Soc. Vict., vol. 55, pt. 2, p. 159; 1943) that of the eleven species of Lepidocyclina recorded by Chapman and herself from the Victorian beds, only three have been allowed as valid (with two of them new) after a revision of the material by the Dutch Indies expert Dr. Tan Sin Hok. On Chapman's slide of foraminifera from Hokianga South Head, G.S. loc. 753 (see N.Z. Geol. Surv. Pal. Bull. No. 11, pp. 19, 94; 1926) the specimens identified by him as Lepidocyclina dilatata Mich. are identical with the one on which his record of “Miogypsina orakeiensis (Karr.)” rests—this actual specimen has now been sectioned and is very plainly a Nephrolepidina, as are all other specimens of orakeiensis from the type locality or elsewhere. Chapman's specific (and generic!) records of the larger foraminifera are thus no more trustworthy than his others; and, indeed, it has been the experience in New Zealand that the same must be said of all his identifications of macrofossils (molluses, fish remains, etc.). As regards our Orbitoids, the only safe course to pursue at present is to disregard identifications that have not been confirmed by an expert. Glaessner (Proc. Roy. Soc. Viet., vol. 55, pt. 1, p. 70; 1943) has confirmed that Eulepidina and Nephrolepidina occur at Hokianga South Head (a Waitemata bed, Lower Ihungia horizon); a Miogypsina of the irregularis Mich. type certainly also occurs at this horizon (especially at Pakaurangi Point); and Trybliolepidina is known to me from an Upper Tutamoe horizon in Hawke's Bay. Heterostegina and Cycloclypeus (more than one species of each) occur from Lower Ihungia to Upper Tutamoe (Lower to Middle Miocene), and Operculinella has been authenticated by Chapman and Parr (Proc. Roy. Soc. Vict., vol. 50, pt. 1, p. 288; 1938) from Kawakawa, a horizon that is probably Whaingaroan or Upper Kaiatan. But Chapman's record of Miogypsinoides (Rec. Cant. Mus., vol. 3, no. 7, p. 491; 1932) from three localities in the Mount Somers District (age, between Waitakian and Hutchinsonian, i.e., Middle Oligocene), based on specimens 0.34 mm. long (one-fifth the size of the Moluccan type) has not yet been confirmed, nor has the occurrence of true Discocyclina. Specimens of Orbitoids from the Eyre River have now been obtained in a much better state of preservation than were available to Chapman, and all of them show more or less clearly the possession of 5–6 starfish-like arms and Discocycline internal chambers, i.e., the generic characteristics of Asterocyclina. Where the arms appear to be missing, equatorial sections show Asterocycline outlines and indicate a broken test. Chapman's figures show only vertical sections and it is possible that all his specimens were broken Asterocyclinas; it is even quite possible that the two specimens he identified as Assilina were also badly preserved Asterocyclina, central fragments of which are also almost certainly his “Heterostegina reticulata”. At all events, many specimens in the original matrix are
broken equatorially, and all those seen are Asterocyclina, with the star shape more and more pronounced as growth proceeds; as it seems likely that there are differences from the European stellata (d'Archiac), it seems to be the safest course in the meantime to regard all the Eyre River Orbitoids as Asterocyclina speighti (Chap.).
The range of Asterocyclina is given by Senn (Eclog. geol. Helvet., vol. 28, no. 1, pl. 9; 1935) as strictly Upper Eocene in Venezuela and elsewhere in America, Upper and Middle Eocene and doubtfully lower in Morocco, Upper and Middle Eocene and extending into the Lower Eocene in Europe.* Gerth (Proc. Konin. Akad. Weten. Amst., vol. 38, no. 4, p. 458; 1935) states that “Discocyclina Gumb. was present in the Eastern part of the Tethys area already in the Palaeocene…. Besides the ordinary… the radially built forms appear… separated as… Asterocyclina… the zenith of evolution of the genus lies in the upper Eocene; it even seems as if the radially built forms here prevail upon the ordinary.” In the latest summary of Indo-Pacific Orbitoid faunas, Glaessner does not discuss Asterocyclina. An occurrence of this genus in New Zealand must indicate an Eocene age, and the probabilities would seem to favour Upper Eocene, unless the distribution resembled North Africa or Europe. The matter is of considerable interest, since I have recently found Asterocyclina at another locality, in a horizon which must be considerably younger than that of the Eyre River. At Fortification Hill, in the Oamaru area, there is a good section through the Oamaru Limestone; microfaunas have been examined throughout, and show that the lower part has a rich assemblage dominated by such forms as Asterigerina, Amphistegina, Carpenteria, Sphaerogypsina, etc., accompanied by fairly abundant Asterocyclina, similar to speighti but smaller, less developed, and less papillose. The presence of Globigerinoides index Fin. and Bolivina pontis Fin. in the accompanying assemblage is sufficient indication of Upper Kaiatan age, i.e., the top of the Eocene, just below the Whaingaroan. This is just where Asterocyclina is to be expected, and it fits in perfectly with the age ideas already developed from the smaller foraminifera. But the small forms accompanying speighti at the Eyre River tell a very different story.
Six samples, from four different collectors, have been examined and the faunas mounted. The localities are:
F.5048. White Creek, one and a-half miles to East of Eyre R.; Orbitoids abundant (collected R. Speight).
F.5049. Eyre River, Discocyclina bed; only weathered Orbitoids; same locality and preservation as given by Chapman (collected R. Speight).
F.5697. White Creek; same as 5048, but a different layer, with Orbitoids rare and a large microfauna (collected A. A. Olsson and J. Marwick).
F.6423. Five chains up Eyre R. from race intake, dark gritty
[Footnote] * Elsewhere, Senn (Bull. Am. Assoc. Pet. Geol., vol. 24, no. 9, p. 1559; 1940) notes that “In Europe the first appearance of Asterocyclina occurs in the Ypresian,” and both Senn and Vaughan have noted the genus from the Middle Eocene of South America.
glauconitic mudstone overlying basic lava flow and dense glauconitic sandstone; Orbitoids rare (collected E. O. Macpherson).
F.6423A. In water-race close to intake, one chain downstream from tin but; coarse to medium sandstone with glauconite, apparently overlying 6423; Orbitoids fairly abundant (collected E. O. Macpherson).
F.6423B. Same as 6423, the underlying dense glauconitic sandstone; no Orbitoids or other fauna (collected E. O. Macpherson).
The microfaunas from all these are obviously richer or poorer representations of the same assemblage; the more important species in the combined fauna are as follows:
|Bolivinopsis cf. cubensis (C. & B.)||Anomalinoides eosuturalis (Fin.)|
|Textularia n.sp.||Anomalinoides aff. danvillensis (H. & W.)|
|Verneuilina n.sp. aff. limbata Cush.|
|Gaudryina n.sp.||Eponides concentricus (F. & M.)|
|Clavulinoides aff. instar Fin.||Gyroidinoides n.sp.|
|Marssonella aff. indentata C. & J.||Alabamina tenuicarinata (C., P., & C.)|
|Vaginulinopsis marshalli (Fin.)|
|Vaginulina n.sp.||Parrella n.sp.|
|Nodosaria cf. affinis Reuss.||Epistomina elegans d'Orb.|
|Lagena acuticosta Reuss.||Asterigerina n.sp.|
|Lagena hexagona Will.||Calcarina n.sp. aff. mackayi (Karr.)|
|Guttulina probleema d'Orb.||Cibicides parki Fin.|
|Pseudoglandulina erecta (Stache)||Cibicides aff. burlingtonensis Jenn.|
|Bulimina aff. pupula Stache||Vagocibicides n.sp.|
|Bulimina bortonica Fin.||Planorbulina n.sp.|
|Pleurostomella n.sp. (much compressed)||Carpenteria sp.|
|Allomorphina trochoides (Reuss)||Globigerina linaperta Fin.|
|Nonion cf. maoricum (Stache)||Globorotalia n.sp. aff. dehiscens (C., P., & C.)|
|Anomalina aff. visenda Fin.|
This assemblage is plainly very different from those usually seen in the New Zealand Eocene, largely because of facies. The facies, indeed, is very similar to that of the Fortification Hill beds, where Astcrocyclina likewise occurs, though Amphistegina is notably absent, and the Asterigerina is a small primitive species. In spite of the odd ecology, there are numerous species in the list to indicate that while the age is not as old as that of our earliest Tertiary (first zone in Te Uri Stream section above last occurrence of Rzehakina; approximately equals Midway, i.e., Palaeocene), it is older than what we call Bortonian (placed in the Middle Eocene). Vaginulinopsis marshalli and Allomorphina trochoides especially are markers for beds older than Bortonian, at least as old as the Kurinui beds of the Hampden section, and probably slightly older. Two other faunas are known, comparable in general association and index species. One is at Boulder Hill, near Dunedin, lying some distance above the Wangaloan (Danian) shell bed, but below a horizon with the Bortonian Vaginulinopsis hochstetteri (Stache). The other is at Tioriori, Chatham Islands, an isolated calcareous bed with the mollusc Notostrea tarda (Hutt.), a rich micro-fauna with some marked resemblances to the American Wilcox (Lower Eocene) and to either the Kurinui horizon in the Te Uri Stream section or to the zone just below it. In the Mid-Waipara section, faunas with V. marshalli (Fin.) occur above lowest Tertiary faunas with V. waiparaensis (Fin.), and below “Wanstead” (Bortonian) faunas with V. hochstetteri; and the Lower Kaiatan beds still have to come above these before the Bolivina pontis horizon of Fortification Hill is reached.
It thus seems clear that Asterocyclina occurs at two quite different levels in New Zealand, the upper being topmost Eocene, while the Eyre River lower level can hardly be any higher than Lower Eocene, and is probably well down in that. It is of considerable additional interest and value that the American Eocene genus Coleites Plummer shows a similar range in New Zealand; in the Tioriori bed occur specimens very like the Lower Wilcox laevigatus Toulmin and one as strongly reticulate as the Midway genotype reticulosus (Plummer); while in the lowest Maheno marls (a horizon equivalent to Fortification Hill, with Bolivina pontis) are larger and still smoother specimens of a new species of Coleites, reinforcing the conclusion that this horizon is still of Eocene age.
From the Oxford Chalk itself, a number of samples have been seen, but until the present collecting by E. O. Macpherson there was no information as to whether more than one zone was present. The localities from which samples were examined and mounted are as follows:
F.5047. Original sample from R. Speight, same as material sent to Chapman, but from an unspecified position in the 50 ft. deposit.
F.6465. Near base of Chalk (collected E. O. Macpherson).
F.6464. Ibid., White Valley, Chalk Hill, Stn. 22 (Macpherson).
F.6463. At eroded top of Chalk, Quarry at Stn. 22 (Macpherson).
F.6462. Ibid., old Quarry, White Road, Stn. 16 (Macpherson). Since considerable time had been expended on 5047 in the past, and it has the largest fauna, quite representative of the other samples, only Nos. 6465 and 6463 were fully mounted, so that the smaller number of records from 6464 and 6462 does not indicate smaller faunas. A check-list of the five faunas may be presented in tabular form:
|Bolivinopsis cf. cubensis (C. & B.)||X||X||X||X||X|
|Vulvulina pennatula (Batsch)||X||X||X||X||X|
|Arenobulimina ? n.sp.||X||X||X||X|
|Karreriella bradyi Cush.||X||X||X||X|
|" " chilostoma (Reuss)||X|
|" " novozealandica Cush.||X||X||X||X||X|
|Martinottiella aff. communis (d'Orb.)||X||X||X|
|Arenodosaria antipoda (Stache)||X||X||X||X|
|Pseudogaudryina reussi (Stache)||X||X||X||X|
|Robulus whaingaroicus (Stache)||X||X||X||X||X|
|" " antipodus (Stache)||X||X||X|
|" " foliatus (Stache)||X||X|
|" " cf. duracinus (Stache)||X|
|" " glaucinus (Stache)||X||X|
|Saracenaria arcuatula (Stache)||X||X||X||X|
|Astacolus aff. orepidulus (F. & M.)||X|
|" " ? compressus (Stache)||X|
|Vaginulina vagina (Stache)||X||X|
|Vaginulinopsis hochstetteri (Stache)||X||X||X||X||X|
|" " interruptus (Stache)||X|
|" " n.sp.||X||X||X|
|Marginulinopsis spinulosa (Stache)||X||X||X|
|" " pseudohirsuta (Nutt.)||X||X|
|" " allani (Fin.)||X|
|Marginulina glabra d'Orb.||X|
|Marginulina subbullata Hantken||X||X|
|" " duracina Stache||X|
|Dentalina cf. advena Cush.||X||X||X||X|
|" " obliquesuturata (Stache)||X||X||X|
|" " subcostata Chap.||X||X|
|" " soluta Reuss.||X||X||X||X|
|Nodosaria callosa Stache||X||X||X||X|
|" " ? longiscata d'Orb.||X||X||X||X|
|" " ? aff. fistuca Schwag.||X||X||X||X||X|
|Chrysalogonium striatissimum (Stache)||X||X||X||X||X|
|" " n.sp.||X||X|
|" " verticalis (Stache)||X||X||X||X||X|
|Nodogenerina pomuligera (Stache)||X||X||X||X||X|
|" " n.sp.||X||X||X||X||X|
|" " antipoda (Stache)||X||X||X||X|
|" " ? rotundata (Stache)||X||X||X|
|Lagena distoma P. & J.||X||X|
|" " tenuistriata Stache||X|
|" " acuticosta, Reuss.||X||X|
|" " striata d'Orb.||X|
|" " feildeniana Brady||X||X|
|" " orbignyana Brady||X||X||X|
|Lagenoglandlina annulata (Stache)||X||X|
|Pseudoglandulina n.sp. aff. gallowayi Cush.||X|
|Glandulina aperta Stache||X|
|Polymorphina lingulata Stache||X||X||X|
|Sigmomorphina pernula (Stache)||X||X||X||X||X|
|Pseudopolymorphina incavata (Stache)||X||X||X||X|
|Guttulina probleema (d'Orb.)||X||X||X||X|
|" " aff. seguenzana (Brady)||X||X|
|Pyrulina several spp.||X|
|Gumbelina ototara Fin.||X||X||X|
|Bolivina pontis Fin.||X||X||X||X||X|
|Uvigerina maynei Chap.||X||X||X||X|
|" " aff. gracilis Reuss.||X||X||X||X|
|Siphogenerina striatissima (Stache)||X||X||X|
|Angulogerina cf. oligocaenica (Andreae)||X||X||X|
|Trifarina bradyi Cush.||X||X||X||X|
|" " n.sp. A. (ornate)||X||X||X|
|" " n.sp. B. (elongate)||X||X||X||X||X|
|Bulimina pupula Stache||X||X||X|
|" " truncanella Fin.||X||X|
|Neobulimina ? n.sp.||X||X|
|Pleurostomella subnodosa Reuss.||X|
|" " alternans Schwag.||X||X||X||X|
|" " alazanensis Cush.||X|
|" " brevis Schwag.||X||X||X|
|Nodosarella subnodosa (Guppy)||X||X||X||X|
|" " salmojraghi (Mart.)||X||X||X|
|Ellipsoglandulina subconica (Kreuz.)||X||X||X|
|" " sp. (smooth)||X|
|Cassidulina laevigata d'Orb.||X||X||X||X|
|" " subglobosa, Brady||X||X||X||X||X|
|Pullenia bulloides (d'Orb.)||X||X||X||X||X|
|" " quinqueloba (Reuss)||X||X||X||X||X|
|Nonion maoricum (Stache)||X||X|
|" " " " smooth var.||X||X||X||X||X|
|" " simplex (Karr.)||X||X|
|Astrononion n.sp. A. (small, stout)||X||X||X|
|" " n.sp. B. (small, thin)||X||X|
|Nonionella zenitens Fin.||X||X|
|" " ? n.sp.||X||X||X|
|Anomalina aotea Fin.||X||X||X||X|
|Anomalinoides fasciatus (Stache)||X||X||X||X||X|
|" " orbiculus (Stache)||X||X||X||X||X|
|" " eoglabra (Fin.)||X||X||X||X||X|
|Eponides eouadorensis G. & M.||X||X||X||X||X|
|Gyroidinoides allani (Fin.)||X||X||X||X|
|" " prominula (Stache)||X||X||X||X||X|
|" " n.sp. A aff. nitidula (Schw.)||X||X||X|
|" " n.sp. B (6 chambers)||X|
|" " n.sp. C (small, flat)||X|
|Rotaliatina sulcigera (Stache)||X||X||X||X||X|
|Alabamina tenuimarginata (C., P., & C.)||X||X|
|Notorotalia stachei Fin.||X|
|Cibicides verrucosus Fin.||X||X||X||X|
|" " collinsi Fin.||X||X|
|" " thiara (Stache)||X||X||X||X||X|
|" " elatior (Stache)||X||X||X||X|
|" " aff. robertsonianus (Brady||X||X||X||X|
|" " n.sp. aff. novozelandicus (Karr.)||X||X||X||X||X|
|" " n.sp. A (large, coarse pores)||X||X||X||X|
|" " n.sp. B (smaller, coarse pores)||X||X||X|
|" " n.sp. C (small, smooth base)||X||X||X||X||X|
|" " n.sp. D (conic, very involute)||X||X||X|
|Planulina cf. sinuosa (Sideb.)||X||X|
|Laticarinina halophora (Stache)||X||X||X||X||X|
|Parvicarinina altocamerata (H-A. & E.)||X||X||X||X|
|Globigerina angipora Stache||X||X|
|" " reticulata Stache||X||X||X||X||X|
|" " suboretacea Lornnicki||X|
|Sphaeroidina bulloides d'Orb.||X||X||X||X||X|
It is probable that 5047 was a mixed sample, from various horizons in the chalk, so it is possible that some of the above species occur only in the upper part and some only in the lower, but the only important species that were definitely restricted to the upper samples are Notorotalia stachei and Vaginulinopsis interruptus, and even this is probably due to some slight difference in ecology. There is not the slightest evidence to show that the chalk is not a single homogeneous unit, palaeontologically as well as physically. The occurrence throughout of such index forms as Pseudogaudryina reussi, Vaginulinopsis hochstetteri, Polymorphina lingulata, Sigmomorphina pernula, Bolivina, pontis, Uvigerina maynei, Rotaliatina sulcigera, and Cibicides verrucosus must indicate reference of the whole to the Whaingaroan (Lower Oligocene). The fauna as a whole is a close match to several found near the type area at Waitetuna Estuary, Whaingaroa Harbour, and is clearly an offshore facies of this age. The Semivulvulina, Verneuilina, Asterigerina, and Ceratobulimina facies of the Whaingaroan, all well known elsewhere in New Zealand, are not represented at Oxford. An estimation of the environs of deposition on the lines carried out by Hedberg (Journ. Pal., vol. 11, no. 8, p. 684; 1937) for the Carapita formation of Venezuela makes it probable that the Oxford Chalk was laid down in a depth of about 300–500 fathoms, perhaps even more. The scarcity of molluses, and the abundance of such lines as Gyroidinoides, Sphaeroidina, Eponides (umbonatus), Uvigerina (pygmea and canariensis),
Cassidulina (laevigata and subglobosa), etc., as well as the absence of Miliolids and littoral forms could well support a depth of up to 1000 fathoms. There is, however, a tendency amongst workers who describe Tertiary faunas such as this to suggest depths tending toward the shallower limits of the ranges indicated by Recent dredgings; note, for example, the discussion by Palmer and Bermudez (Mem. Soc. Cub. Hist. Nat., vol. 10, no. 4; 1936) of the Finca Adelina fauna from Cuba, which they suggest is nearer the 100 rather than 500 fathom mark, though it bears a striking resemblance ecologically to the Miocene Indo-Pacific fauna of Kar Nicobar (Schwager, Reise d. Novara, Geol. Teil., 2, pp. 187–268; 1866). Such Globigerina-ooze deposits as this and the Fiji Soapstone (Cushman, B.P. Bishop Mus. Bull., 119, pp. 102–142; 1934) have much in common with the Oxford Chalk, except for their more marly nature and the predominance of pelagic forms.
Most of the Oligocene faunas available for comparison (either directly or from literature) differ considerably specifically from the New Zealand ones, in many cases because they seem to indicate a warmer temperature. The Huasteca (Lower Oligocene) of Mexico seems to be more closely allied than either the Meson (Middle Oligocene) or Chapapote (Upper Eocene); the Cojimar (Upper Oligocene) of Cuba has much less resemblance than the Finca Adelina (Lower Oligocene); the Carapita (Upper and ? Middle Oligocene) and other Siphogenerina transversa faunas of South America are not much like ours; and the facies in the Gulf Coast and Californian Oligocene practically rule out comparison. In the deep-water deposits of the Trinidad section, the fauna that is closest to the Whaingaroan, and the Oxford Chalk facies, is from the Lower Cipero Marl, regarded by Senn (Bull. A.A.P.G., vol. 24, no. 9, p. 1580; 1940) as Lower Oligocene; the Mount Moriah (Upper Eocene, with Hantkenina, as in New Zealand) and the Bamboo Clay (Middle Oligocene, with resemblances to our Duntroonian and Waitakian) have much less resemblance. As far as comparisons by means of smaller foraminifera can be carried, everything supports the belief that our Whaingaroan is best correlated with faunas regarded elsewhere as Lower Oligocene; no Orbitoids have been found in any beds of that age as yet in New Zealand.