J. A. Grant-Mackie

Hokonui Stratigraphy of the Awakino-Mahoenui area, South West Auckland

Summary Trias-Jura rocks of the Awakino-Mahoenui area constitute part of the western limb of the Kawhia Syncline in its southern-most exposure. The syncline is approximately meridional in alignment and pitches northwards at a low angle. Strata have dips varying from nearly vertical in the west of the area to about 15° east at the top of the succession in the east. The strata form the Herangi Range which originated as a north-south fold or the peneplained surface resulting from the post-Hokonui orogeny. This fold is believed to be faulted on its western edge, but while this is also the case on the eastern limb farther north, in the Awakino-Mahoenui area faulting seems not to have occurred at the surface. The oldest beds exposed are 7,000 ft of Oretian (lower Carnian) which are believed to be the equivalent of 2,100 ft of strata above the Moeatoa conglomerate at Marakopa. These are followed conformably by 2,200 ft of Otamitan strata (Carnian), 1,800 ft to 2,300 ft of Warepan (Norian), 2,800 ft of Otapirian ...

Geology of the Whangaparaoa area, eastern bay of plenty

Abstract Sedimentary rocks within the Whangaparaoa area are divided into two groups. Of these, one group and three formations are newly established and one formation is redefined; another previously accepted formation is discarded. Poorly exposed, unfossiliferous Haumurian-Teurian sediments are included within the Mangatu Group which is not further subdivided. Coarse lithologies which grade up the stratigraphic sequence into interbedded thin sandstones and grey mudstones containing basal Miocene microfaunas are included within the Whakai Formation. The Wharekahika Formation, which was erected by Ongley and MacPherson in 1928 and regarded as of probable Pliocene age, is discarded because it cannot now be readily identified and the fauna listed for it is likely to be a mixed one. Strata of the Runaway Group which crop out over large portions of the Whangaparaoa area comprise two formations—the Te Kahika Formation of Opoitian age and the Whangaparaoa Pumiceous Sandstone of Opoitian to ? Waipipian age. Fossil...

Upper jurassic fossils from the Waipapa group of Tawharanui Peninsula, North Auckland, New Zealand

Abstract Malayomaorica malayomaorica (Krumbeck) (s.s.) and Inoceramus cf. haasti Hochstetter are recorded in situ from the northern shore of Tawharanui Peninsula. They indicate an Ohauan (Middle Kimmeridgian) age for the Waipapa Group at this locality. The bivalves are associated with the ichnofossil Rhizocorallium, which possibly indicates a shallow infra littoral environment of deposition.

Jurassic Coleoidea of New Caledonia

Coleoids are more diverse in the Jurassic of New Caledonia than previously reported. They are widespread and sometimes abundant in the shallow-water West Coast facies Lower and Middle Jurassic and rare in the more off-shore Central Chain facies Upper Jurassic. The fauna consists of a rare Sinemurian aulacocerid, Ausseites sp. nov., and seven taxa of Belemnitida, most of which are rare and poorly preserved, and are presented in open nomenclature only. Belemnopsis kuntkotensis var. puenensis Avias 1953 is synonymised with B. compressa Avias 1953, which is the most widespread New Caledonian belemnite and is about Bathonian-Callovian in age. Dicoelites aviasi sp. nov. immediately predates it. Other taxa include Belemnopsis, Dicoelites, Hibolithes and a new genus of Belemnitidae. The New Caledonian Jurassic fauna, coleoids excepted, is generally present also in New Zealand rocks, but not a single coleoid taxon is yet known to be common to the two. The absence of the New Caledonian taxa from New Zealand collect...

Permian fusulinid Foraminifera from Wherowhero Point, Orua Bay, Northland, New Zealand

Abstract A new thin‐section study of limestones from Wherowhero Point, Orua Bay, Northland, has produced a fauna of 24 fusuline taxa and 19 smaller foraminifers. The fusulines are much more diverse than earlier records have shown and include genera and species not previously recorded (e.g., Pseudokahlerina compressa Sosnina, Reichelina cf. lamarensis Skinner & Wilde, Rauserella cf. breviscula Sosnina, Chusenella urulungensis Wang et al., Yabeina ampla Skinner & Wilde, Dunbarula, and Pseudo‐fusulina). A species previously recorded as Yabeina parvula Skinner & Wilde is re‐identified as Y. globosa (Yabe), and that identified earlier as Lepidolina multiseptata (Deprat) is determined to be its evolutionary precursor L. shiraiwensis Ozawa. The latter species, together with Kahlerina pachytheca Kochansky‐Devide & Ramovs, Neoschwagerina margaritae Deprat, and Yabeina archaica Dutkevich, are the most widespread species in the eight collections studied from four localities, and these four species and Yabeina ampla ...

Status and identity of the New Zealand Upper Triassic bivalve Monotis salinaria var. richmondiana Zittel 1864

Abstract Monotis salinaria var. richmondiana, described originally from upper Triassic (Norian) strata of the Nelson district of New Zealand, has had a very chequered taxonomic career. Its close relationship with the Siberian M. ochotica (Keyserling) was first noted by Teller, and many authors since 1886 have given it subspecific or varietal rank within M. ochotica, or suppressed it in favour of that species. Others have regarded it as specifically distinct and have even identified infraspecific variations. At no time since its introduction has there been a nomenclature applied uniformly by workers. This nomenclatural instability has resulted from many factors: Zittels figures are inadequate and have been assumed to be all of a single taxon; all or nearly all strongly ribbed neozelanic Monotis have been lumped into M. richmondiana; Ichikawa selected as lectotype a sub-adult specimen not included amongst Zittels figured valves; the stratigraphy of Monotis sequences in New Zealand has not previously been ...

Late Triassic‐Jurassic bivalves from volcanic sediments of the Lhasa block, Tibet

Abstract Mesozoic volcanic sediments known as the Yeba Formation are widespread in the northeastern region of Lhasa. Recent fossil collections in the formation allow the establishment of a biostratigraphic framework for the volcanic sediments; bivalves are assigned to 21 genera and 22 species including a new genus and 5 new species: Lhasanella lhasaensis (gen. et sp. nov.), Trigonodus xiabolangensis (sp. nov.), Isocyprina lhasaensis (sp. nov.), Gervillaria tibetica (sp. nov.), and Jurassicorbula fuersichi (sp. nov.). Three benthic assemblages have been recognised: the Trigonodus‐Isocyprina assemblage (Rhaetian‐Hettangian), the Lhasanella‐Propeamussium assemblage (Toarcian‐Bajocian), and the Jurassicorbula‐Neomiodon assemblage (Middle Jurassic). The Yeba Formation ranges in age from latest Triassic to Middle Jurassic. Volcanism in the Lhasa block occurred frequently during this period, corresponding to the fragmentation episode in eastern Gondwanaland and to the northwards drift of the Lhasa block. A strong faunal affinity between the Lhasa block and southern Qinghai, Japan, and Vietnam suggests that the Lhasa block had been located within the northern marginal region of the East Tethys since Toarcian times. The existence of a deep ocean which might serve as a barrier to fauna dispersal between the Lhasa and Qingtang blocks remains questionable.

Upper Jurassic and Lower Cretaceous Buchia (Bivalvia) from southern Tibet, and some wider considerations

Three different assemblages of Buchia species are recorded from fine elastics in the Nyalam district of southern Tibet. Praebuchia, Buchia spitiensis and B. concentrica (upper Oxfordian-Kimmeridgian) occur in the Menbu Formation; B. rugosa, B. piochii etc. (Tithonian) characterise the Shuomo Formation; B. shuomoensis, B. mankamanensis etc. (Lower Cretaceous) occur in the Guchuochun Formation. These assemblages correspond with a worldwide pattern of initial development, acme and then decline evident in the genus, whose distribution clearly shows a southwards migration pattern, with extinction operating in the opposite direction. Although regarded as of shallow water origin in some areas, in the central Tethys Buchia appears in deeper water strata and this is correlated with preference for cooler temperatures; its extinction could thus have been due to the postulated terminal Jurassic regression.

The Warepan Stage of the Upper Triassic: Redefinition and subdivision

Abstract Recently published studies show that the current definition of the Warepan Stage of the New Zealand-New Caledonian Upper Triassic, based upon the incoming of Monotis (Entomonotis) richmondiana Zittel, is inadequate. Past practice has relied upon the first appearance of the genus Monotis, and earliest species are not M. richmondiana but members of the subgenus Eomonotis. To avoid the stage boundary being placed within, instead of at the base of, a sequence of short-lived rapidly evolving species of the one genus, it is recommended that M. richmondiana be replaced as the Warepan index fossil by the earliest species in the region, namely, Monotis (Eomonotis) kiritehereensis G-M., M. (E.) rauparaha mokaui G-M., and M. (E.) murihikuensis taringatura G-M. Stratigraphic analysis of New Zealand sequences containing these three taxa indicates that they are likely to have been contemporaries. This redefinition calls into doubt the suitability of the Rocky Dome (South Otago) area as a stratotype, for Eomono...

Paleoecology of an early Miocene, rapidly submerging rocky shore, Motuketekete Island, Hauraki Gulf, New Zealand

Abstract More than 70 macrofossil taxa (including 14 bivalves, 6 gastropods, 8 corals, 4 echinoderms, and 10 barnacles) are recorded from early Miocene (Otaian) Kawau Subgroup strata (Cape Rodney Formation and Motuketekete Limestone, lower Waitemata Group) at Motuketekete Island, Hauraki Gulf, north of Auckland City. Both in situ and transported fossils occur in deposits of greywacke boulder conglomerate, cobble to pebble conglomerate/sandstone, bioclastic calcareous grainstone, and an allochthonous breccia debris event unit, which correspond to lithofacies A, C, D, and E, respectively, of Ricketts et al. Greywacke boulders accumulated at the base of a greywacke paleocliff or sea stack that was planed off at its top to form a shore platform during the Miocene. A >2 m long, 16 cm thick coral colony grew atop a mixed substrate of boulders, pebbles, and sand, and exhibits two successional regrowth phases following debris‐influx events. Boulders and cobbles bored by pholadid bivalves (Parapholas aucklandicum Powell) are common in these basal bouldery talus deposits. A diverse suite of macrofossils, including chaliciform corals, occurs in somewhat finer grained deposits that buried the greywacke basement and boulder talus pile, and indicates either slightly deeper or more turbid conditions in the shallow photic zone. The cross‐bedded, bioclastic Motuketekete Limestone overlies these coarse‐grained Cape Rodney Formation units. Its fauna indicates deepening, with replacement of shallow by offshore taxa (e.g., Crenostrea with Bathylasma), as the Waitemata Basin underwent rapid tectonic subsidence and redeposition of sediments with the onset of subduction along the Hikurangi convergent margin. A newly identified lens of “upper breccia” (lithofacies E) in the Motuketekete Limestone contains rounded blocks of colonial coral and Tertiary siltstone. The Motuketekete occurrence of lithofacies E extends the known geographic range of this geologically instantaneous deposit; it records a regional tectonic event that is interpreted as an avalanche/debris flow triggered by faulting. The breccia appears to be a reliable marker for local lithostratigraphic correlation in lower Waitemata strata exposed north of Auckland. Appendices provide a systematic analysis of the barnacle fauna and the description of a new gastropod species, Bolma (Bolma) ballancei. The overall biotic content of the Kawau Subgroup, especially those taxa associated with hard substrate community development, indicate warm subtropical conditions similar to those found elsewhere in northern New Zealand during the early Miocene.