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Cretaceous.
The top of the Raukumara Formation is at present the oldest bed yielding a micro-fauna, and here also is the only horizon with abundant Globigerina cretacea d'Orb.; the accompanying Globigerinella aspera (Ehrenberg) ranges somewhat higher in the section, into Piripauan. The former has been erroneously recorded from numerous higher horizons; in America it is still common in the Texan Navarro (Campanian), but is in New Zealand extremely rare or absent in beds of approximately that age, being replaced by a form close to the Navarro rugosa Plummer. This and the absence of typical Globotruncana, etc., could easily suggest that the New Zealand Upper Cretaceous stages are even younger than considered here. In Mexico Globotruncana is similarly absent in the Velasco, though very characteristic of the Mendez, considered by Thalmann (1935B, p. 371) to be Paleocene and Santonian respectively. There is little in the rest of the Raukumara fauna to throw light on its age at present, though it has some general resemblance to the Albian faunas figured by Eichenberg (1935, p. 389) from the North German oil-fields, and on the whole is remarkably similar to a fauna just lately figured by Tappan (1940, Journ. Pal., vol. 14, no. 2, pp. 93–126), from the Grayson formation of Northern Texas, and placed as Upper Albian. Ornate Epistominas are lacking, but the Frondicularians and allied forms, though not particularly like the illustrated species of the Texan Taylor (Santonian), have much less in common with the Navarro than have the Piripauan species.
The evidence of these latter seems fairly strong, for the Piripauan Rakauroa formation contains species of Palmula very close to reticulata (Reuss), semireticulata (Cushman and Jarvis), and primitiva Cush., a Frondicularia like dimidia Bagg, and a Planularia close to simondsi (Carsey)—all prominent Navarro species. The restricted Cretaceous genus Bolivinoides (as dorreeni Finlay, of the delicatula Cush. group) also occurs at this horizon, while above it in the section occurs Nuttallides alatus (Marsson), also known from high in the Cretaceous of Rügen, Germany, Arkansas, and Trinidad. The allied and older N. micheliniana d'Orb. so common in the Craie Blanche of Europe, Middle Taylor of America, and White Chalk of Antigua (see discussion in Cushman, Contrib. Cush. Lab. Foram. Research, vol. 7, pt. 2, pp. 34 and 45, 1931; and Journ. Pal. vol. 6, No. 4, p. 342, 1932) has not been found here in typical form, but has a representative (tholus Finlay) in the Lower Piripauan showing the same evolutionary differences as the form in the Trinidad Upper Navarro called by Cushman (Proc. U.S. Nat. Mus., vol. 80, p. 48, 1932) “Pulvinulinella alata Marsson.” In the latter fauna and the
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Saratoga Chalk, also of Navarro age (see Cushman, Journ. Pal., vol. 5, No. 4, p. 310, 1931), is the conspicuous species Gyroidina globosa v. Hag.; this is equally conspicuous in almost every Piripauan fauna, but absent above and below, and does not seem to be in the American Taylor or Midway. Rotamorphina cushmani Finlay is known only from our Upper Piripauan and this same Upper Navarro Trinidad horizon. The Trinidad fauna has very much in common with our highest Piripauan, and has been regarded by Cushman as most similar to the Mexican Velasco (Tamesí of Muir) and equivalent to the Texan Navarro, but many micro-palaeontologists, including Thalmann, Plummer, and Dorr, regard it as younger—even Paleocene. The late J. M. Muir stated in a personal letter discussing the problem that “The Tamesí is certainly post-Maestrichtian and definitely pre-Midway (of Texas). The inference is that the beds are probably Danian.”
An important connection is furnished by the extreme similarity of some Piripauan faunas to those of the Burdwood Bank Uppermost Cretaceous described by Macfadyen (1933, p. 4). All the species he figures (except Pseudotextularia) are conspicuous in, and all but one limited to, the Piripauan. of particular interest is the genus Rzehakina Cushman (see Finlay, 1939B p. 534), which is abundant in and highly characteristic of the North Island Piripauan (the Tapuwaeroa and restricted Mangatu formations); the known occurrences of R. epigona (Rzehak) in the Middle and Upper Velasco of Mexico, the Upper Navarro of Trinidad, the Maestrichtian and Danian of French North Morocco, and the “Alttertiar” of Austria (which Glaessner has shown to be really late Cretaceous) support a conclusion that the age of such New Zealand beds must be close to the Tertiary boundary; certainly no older than Santonian (if as old), and no younger than Danian.
Geographically the nearest Cretaceous faunas comparable to those of New Zealand are in the different Gingin horizons in West Australia, which Whitehouse (1926, p. 279) refers to the Lower Santonian, though Crespin (1938, p. 395) thinks that the full range from Cenomanian to Campanian may be present. These faunas in their species of Globotruncana, Gümbelina, Clavulina, Bolivinita, Eouvigerina, and Frondicularia are much more directly comparable with those of the Selma and Annona chalks of the American Taylor, and are more obviously Cretaceous than much of the Piripauan—it is indeed very possible that some of them correlate better with the top of the Clarentian between the Raukumara and Tapuwaeroa. The highest parts of our Cretaceous (Wangaloa beds, Amuri “Teredo Limestone”) have yielded no micro-faunas at their type localities.