Murihiku Terrane Research Articles

Revised systematics and palaeobiogeography of some Late Triassic colonial invertebrates from the Pacific region

Revision of type and additional material of Upper Triassic colonial organisms from New Zealand, New Caledonia, Timor, Siberia, Canada and Chile, previously interpreted as Bryozoa or Cnidaria, provides new insights into their palaeobiology, systematic affinity and palaeobiogeography. Heterastridium conglobatum Reuss remains of uncertain hydrozoan affinity, and could be spheractinoidean, hydroidean, or even milleporine. H. conglobatum disciforme n. subsp. (=“forma” disciforme sensu Gerth) is described from New Zealand. The distribution of Heterastridium in the Murihiku and Torlesse terranes of New Zealand-New Caledonia is documented, and it is recorded as ranging through the Middle and Late Norian (Rutherfordi, Columbianus, and Cordilleranus Zones). Its extreme rarity in the Torlesse terrane is thought to be the result of unsuitable facies. “Monotrypella” timorica Vinassa de Regny, described as a bryozoan, is a calcareous demosponge of uncertain family and genus. “M” maorica Wilckens is shown to be the senior synonym of Eoheteropora katzi Morozova. Eoheteropora is considered to be a tabulate coral, and is shown to be of circum-Pacific distribution from Late Triassic to Early Jurassic time. The genus includes the Norian E. maorica (New Zealand-New Caledonian Murihiku terrane, and Kolymskij massif, Siberia), Rhaetian E. caledonica n.sp. (New Caledonia), Toarcian E. tipperi (Henderson & Perry) (British Columbia, Canada), and possibly also an undescribed form from the Early Jurassic of Chile.

Basement geology of Taranaki and Wanganui Basins, New Zealand

We present a revised interpretation of the basement geology beneath Late Cretaceous to Cenozoic Taranaki and Wanganui Basins of central New Zealand, based on new petrographic, geochemical, and geo‐chronological data from 30 oil exploration wells. Recently published structural and magnetic interpretations of the area assist in the interpolation and extrapolation of geological boundaries. Torlesse and Waipapa Terranes have been identified in Wanganui Basin, and Murihiku Terrane in eastern Taranaki Basin, but Maitai and Brook Street Terrane rocks have not been recognised. Separation Point Suite, Karamea Suite, and Median Tectonic Zone igneous rocks are all identified on the basis of characteristic petrography, geochemistry, and/or age. SHRIMP U‐Pb zircon measurements on igneous samples from western Taranaki wells do not give precise ages but do provide useful constraints: Motueka‐1 granite is latest Devonian — earliest Carboniferous; Tangaroa‐1 and Toropuihi‐1 are Carboniferous; and Surville‐1 is Cretaceous (cf. Separation Point Suite). Our interpretation of sub‐basin geology is compatible with previously observed onland relationships in the North and South Islands.

Park Volcanics, Murihiku Terrane, New Zealand: Petrology, petrochemistry, and tectonic significance

Abstract The Late Triassic to Early Jurassic Park Volcanics Group comprises minor shallow intrusive and extrusive bodies emplaced during mainly marine sedimentation of the Murihiku Terrane, southern New Zealand. Gowan Andesite in western Southland and Glenham Porphyry andesites in eastern Southland are high‐K andesites. Glassy examples have commonly lost K during alteration. Orthoclase contents of Or3.6–3.7 in plagioclase phenocrysts at An50 confirm the high‐K nature of the melts at the time of phenocryst crystallisation. The Gowan andesites have higher Fe/Mg than the Glenham and related differences in minor element chemistry suggesting lower fO 2during fractionation of the parent magma. Pinney Volcanics in western Southland are mostly high‐K trachydacites but, like Glenham Porphyry, include minor rhyolite. Barnicoat Andesite in the Nelson area is medium‐K olivine andesite, marginally tholeiitic in terms of its FeO∗/MgO versus SiO2behaviour, but otherwise is typically calc‐alkaline, as are the Gowan, Glen...

New information on the age and thermal history of a probable Early Triassic siltstone near Kaka Point, South Island, New Zealand

Abstract The conodont Neospathodus homeri s.l. supports a late Early Triassic, Malakovian, age for an ammonoid‐rich horizon in the Potiki Siltstone, 0.9 km south of Kaka Point, southeast Otago, rather than an alternative designation of Early to Middle Anisian. The conodont colour alteration index suggests a thermal history with temperature not exceeding c. 80°C. The Kaka Point structural belt appears to have had a tectonic and thermal history different from that of the adjacent Murihiku Terrane.

Petrology of the Topfer Formation: First Triassic Gondwana sequence from New Zealand

The 2 km2 outcrop of Topfer Formation is the only known sedimentary formation of Triassic age in New Zealand's Western Province. It consists mainly of uniform medium‐grained massive, well sorted felsic volcaniclastic sandstone with minor mudstone, conglomerate and coal. Two distinct petrofacies (litharenite and feldspathic litharenite) are distinguishable on both detrital and diagenetic composition. On the basis of common framework modes, heavy‐mineral assemblages, depositional environment, intrusion by Jurassic dolerite and association with Palaeozoic quartzose sandstone, we relate the Topfer Formation to the Middle to Late Triassic Gondwana sequences of the Sydney Basin, Tasmania and Antarctica. Some similarities in composition of sandstones and igneous conglomerate clasts of the Topfer Formation and those of the coeval Murihiku Terrane of New Zealand's Eastern Province suggest a common continental magmatic‐arc source area (possibly the intervening Median Tectonic Zone). The tiny area of Topfer Formatio...

Preliminary report on Lower Jurassic radiolaria of Gondwana origin from the Kawhia coast, New Zealand

Abstract Well‐preserved radiolarians from the Newcastle Group in southwest Kawhia, New Zealand, constitute the first record of Lower Jurassic radiolarians from in situ deposits in high latitudes of the Southern Hemisphere on the margin of Gondwana. The radiolarians were extracted from carbonate nodules from five horizons in the Rewarewa Formation and the lower part of the Arawhero Formation, in the Murihiku Terrane. The radiolarian‐bearing sequence, which lies within the upper part of the type section of the local Aratauran Stage, is roughly datable as Hettangian‐Sinemurian from rare ammonite occurrences. The radiolarian assemblages consist, on average, of 80–90% spumellarians and 10–20% nassellarians. Spumellarians include species of the following genera: Archaeotriastrum, Crucella, Emiluvia (?) Homeoparo‐riaella, Orbictilifomaa, Pantanellium, Paronaella (?), Pseudocrucella, PseIIdoheliodiscus, Spon‐gostaurus and Spongotrochus. Nassellarians are composed of species of Ragotum, Bipedis, Droltus, Jams (?) Perispyridium (?) Raoultius, Riedelius, Saitoum and Thetis. From data of Lower Jurassic radiolarian faunas of Europe, North America and Japan, the New Zealand fauna shows stronger affinity with those of the European Tethys such as Turkey (e.g. De Wever 1982) and the Northern Alps (Kozur & Mostler 1990) than with faunas from other areas of the circum‐Pacific. This connection between the European Tethyan and New Zealand faunas is not well explained by presently accepted continental reconstructions (Smith et al. 1994) for the Early Jurassic.

Brook street and Murihiku terranes of New Zealand in the context of a mobile South Pacific Gondwana margin

Data from geochemistry, isotope studies and paleomagnetism suggest that both the Permian arc-dominated Brook Street terrane and Triassic-Jurassic Murihiku forearc basin terrane are unrelated to each other and that both are allochthonous with respect to the Gondwana margin. The Murihiku terrane lies farther from the Gondwana margin but its fauna and flora have strong Gondwana affinities and closely resemble those of autochthonous epi-Gondwana basins in Australia and Argentina. All terranes within New Zealand are elongate parallel to the Gondwana margin but very few can be clearly identified in the Australian and Antarctic continental crust that abuts New Zealand in Cretaceous Gondwana reconstructions. Similarly, some Australia terranes do not appear to continue into New Zealand or Antarctica. This suggests that breakup was influenced significantly by old terrane boundaries and also that there was considerable terrane mobility in the active Gondwana margin before the Cretaceous. A systematic comparison of arc chemistry, geochronology, biota, and paleomagnetism is desirable to constrain the development of the South Pacific margin between Australia and South America in the Mesozoic.

Diagenesis and very low‐grade metamorphism of volcaniclastic sandstones from contrasting geodynamic environments, North Island, New Zealand: the Murihiku and Waipapa terranes

Abstract The Mesozoic Murihiku and Waipapa terranes are two accretionary wedges of linked forearc and trench sediments, respectively, that were juxtaposed in the early Cretaceous.Late Triassic to late Jurassic Murihiku terrane volcaniclastic sediments are folded into a regional syncline and have been diagenetically altered. There is a general relationship between zeolite occurrence, clay mineralogy, vitrinite reflectance and stratigraphic position. Youngest Jurassic sediments contain heulandite, analcime and stilbite, whereas late Triassic to mid‐Jurassic sediments have laumontite and heulandite (in detail the zeolite distribution is complicated). Tuffaceous horizons on the eastern limb of the syncline are calcitized rather than zeolitized. Post‐diagenetic fractures associated with uplift are laumontite‐filled. The inferred geothermal gradient is c. 15° C km−1.The Waipapa terrane is an accretionary complex dominated by imbricated terrigenous sediments of Triassic and Jurassic age with enclosed Permian to Jurassic pelagic sediments and basalts. Late Jurassic sediments are massive volaniclastic sandstones. The sediments are non‐foliated, and metamorphic minerals in the massive sandstones have crystallized in specific domains. The observed metamorphic succession of prehnite‐pumpellyite and pumpellyite‐actinolite facies assemblages was overprinted in the imbricated rocks during a thermal event that was late in the deformation sequence and broadly coincident with hydraulic fracturing and veining.The metamorphic successions in the two terranes and their relationships to structural features are in excellent accord with accretionary complex models.

The Park Volcanics group: Field relations of an igneous suite emplaced in the Triassic‐Jurassic Murihiku Terrane, South Island, New Zealand

Abstract Park Volcanics Group is proposed for igneous rocks, either shallow intrusive or extrusive, emplaced in the Murihiku Terrane during Triassic‐Jurassic times. The term replaces Park Intrusives of Mutch, some members of which are shown to be extrusive rather than intrusive. Formation status within the group is given to Gowan Andesite and Pinney Volcanics (new names) in western Southland, Glenham Porphyry in eastern Southland, and Barnicoat Andesite (new) in the Richmond area, Nelson. Gowan Andesite is a porphyritic feldspar two‐pyroxene andesite with a glassy or microcrystalline groundmass. A suite of low‐grade metavolcanic rocks which forms the main mass of Malakoff Hill and which has formerly been included in the “Park Intrusives” is here excluded and ascribed to the Takitimu Group; representative chemical data are given. Glenham Porphyry is typically a porphyritic feldspar two‐pyroxene andesite texturally similar to the Gowan Andesite but with significant geochemical differences. Two volumetricall...

A comparison of Jurassic marine benthonic faunas from South America and New Zealand

Abstract A direct comparison of Jurassic marine bivalves and brachiopods from the Murihiku terrane of New Zealand and the Argentinian-Chilean basins indicates that faunal links between equivalent facies settings of the two regions were even stronger than previously acknowledged. Some faunal elements usually regarded as Maorian endemics are also present in South America, particularly during the Early Jurassic (Aratauran and Ururoan). Middle Jurassic (Temaikan) inoceramid sequences share key elements, probably forming a latitudinally distinct stock. Two successive Retroceramus lineages that repeat general morphological trends are now recognized in South American and New Zealand Middle and Late Jurassic deposits, providing new data on correlation at the Temaikan —Heterian boundary. Since the New Zealand local stage system was based mostly on bivalves, as ammonite faunas are sparse, information from accurately dated Argentinian faunas will help improve correlation with the International Standard. From a paleogeographical point of view, the remarkable degree of faunal exchange suggests the existence of suitable neritic habitats along the margins of Gondwana and is also relevant to the issue of the provenance of New Zealand terranes.

Uranium-lead ages from the Dun Mountain ophiolite belt and Brook Street terrane, South Island, New Zealand

The Dun Mountain ophiolite and overlying Maitai Group is discontinuously exposed for 480 km in South Island, New Zealand. Zircon U/Pb dates from plagiogranite are presented for relatively intact ophiolite, ophiolitic melanges, and for more silicic volcanic-plutonic assemblages in the southern part of the belt where a typical ophiolite association is lacking. Step-wise dissolution experiments on slightly discordant plagiogranite zircon produce more concordant residues that indicate the zircons have lost from ∼1% to more than 5% of their radiogenic Pb relatively recently. High-precision 207 Pb/ 206 Pb dates establish the age of ophiolite formation for at least 350 km along strike to a narrow interval between about 275 and 285 Ma. The zircon U/Pb data confirm correlation of petrologically distinct segments of the Dun Mountain ophiolite and show that mafic-ultramafic ophiolite assemblages and moderately potassic high-level granitoids developed within a short time interval, probably during the extension of a volcanic-arc marginal basin. Thick lenses of polymictic breccia and bio-clastic limestone of the Maitai Group locally rest in depositional contact on relatively intact ophiolite within the Dun Mountain ophiolite. Comparison of inferred biostratigraphic ages from the limestone with the ∼280 Ma ages from the plagiogranites indicate a gap of ∼20 m.y. following ophiolite formation. A granite clast from conglomerate higher in the Maitai Group yielded a near concordant U/Pb date of 265 Ma and provides a maximum age for this part of the sequence. Attenuation of the Dun Mountain ophiolite by extensional faulting and erosion may have occurred during the interval between ophiolite formation and Maitai Group sedimentation. The Dun Mountain ophiolite and overlying Maitai Group are bounded to the west by Triassic and Jurassic volcanogenic sedimentary rocks of the Murihiku terrane, and in turn by the Brook Street terrane, which is interpreted as remnants of an early Permian oceanic arc. A hornblende gabbronorite associated with a layered mafic-ultramafic intrusion in the Brook Street terrane yielded a date of 265 Ma, significantly younger than Dun Mountain ophiolite. Such intrusions may represent the plutonic roots for ankaramitic volcanic rocks that comprise a conspicuous component of the Brook Street terrane, but which are not represented by detritus in the Maitai Group. Biotite granite occurs locally in the Brook Street terrane and is dated at 260 Ma. The absence of any clear stratigraphic correlation or provenance linkage between the Brook Street terrane and Dun Mountain-Maitai terrane suggests strike-slip displacements on intervening terrane boundary faults.

Interpretation of Anisian (Middle Triassic) marine invertebrate faunas from the southwest Pacific

Early to Middle Triassic marine successions are remarkably lacking in the Southern Hemisphere. It would seem that the best developed and most fossiliferous sequences are preserved in New Zealand. To a lesser extent, successions of Early to Middle Triassic age are known from New Caledonia, New Guinea, the Gympie Basin of Eastern Australia, offshore Western Australia, and western South America (in particular Chile).Anisian marine faunas were first collected in New Zealand (Etalian local stage) in the 1940s but it was not until 1953 that their age significance was correctly recognised by Marwick. This was later confirmed by Kummel. Since then an unpublished doctoral study has been completed on the paleontology and biostratigraphy of the Anisian succession within the Murihiku terrane of Southland, South Island, New Zealand. A conclusion of this study, based on ammonoid correlations, was that the cosmopolitan halobiid bivalve Daonella appears earlier in New Zealand than it does in North America.Recent investigations post-date the advent of the tectonostratigraphic terrane concept and suggest that an Anisian fossil record is preserved in at least three terranes in New Zealand (Murihiku, Dun Mountain - Maitai and Torlesse terranes), and two terranes in New Caledonia (probably correlatives of the Murihiku and Torlesse terranes of New Zealand). Analysis of the faunal content of these various terranes suggests that although there are some facies differences (litho and bio), there is little obvious basis for recognition of distinct paleobiogeographic provenance.A corollary to this research on Anisian faunas is the recognition that the New Zealand ammonoid faunas previously considered to be Early Triassic (Malakovian local stage; Murihiku terrane) by Kummel are almost certainly Anisian. However, this does not imply that there isn't an Early Triassic sedimentary record. Significant thicknesses of apparently unfossiliferous sequence are present in each of the relevant terranes. Two isolated Early Triassic ammonoid faunas are now known from elsewhere in New Zealand but from tectonically complex settings in Brook Street (?) and Dun Mountain - Maitai terranes.

Paleomagnetism and question of original location of the Permian Brook Street Terrane, New Zealand

Over 400 rock samples from 30 sites were collected for paleomagnetic study from the volcanogenic section in the Brook Street terrane within the Takitimu Mountains in western Southland, New Zealand. The section includes igneous and sedimentary rocks of the Permian Takitimu Group and White Hill Intrusive Suite. Many of the samples show a partial or complete remagnetization in the present field because of a recent acquisition of viscous remanent magnetization. An Early Permian direction (inclination = 46.1°, declination = 257°), isolated from the Heartbreak and Chimney Peaks formations of the Takitimu Group, indicates a low paleolatitude to midpaleolatitude, position (27° ± 5°) for the Brook Street terrane. Directions from the Late Permian (?) White Hill Intrusives (inclination = 64.6°, declination = 173.3°) suggest a slightly higher paleolatitude than the Early Permian Takitimu Group directions and 70°–90° of intervening clockwise rotation. Plate reconstructions and paleomagnetic data predict a high paleolatitude for the New Zealand margin of Gondwana throughout the late Paleozoic and Mesozoic. The low paleolatitude to middle paleolatitude, implied by the Early Permian Brook Street result, together with the oceanic nature of the Brook Street arc, suggest that the Brook Street terrane is allochthonous to the margin of Gondwana. A published Late Triassic/Early Jurassic paleomagnetic pole from the adjacent Murihiku terrane indicates a high paleolatitude. This suggests that the Brook Street and Murihiku terranes are genetically distinct.

Potassium-argon age of the Glenham Porphyry, Murihiku terrane, eastern Southland, New Zealand

Abstract The Glenham Porphyry is a suite of andesitic terrestrial flows and subvolcanic intrusions in an inlier of Murihiku Supergroup sediments in eastern Southland. Potassium-argon dating has been used to determine the age of the volcanics. Plagioclase ages are in the range 182–240 Ma, indicating a probable Late Triassic to Early Jurassic time of extrusion. Discordant younger ages of whole-rock samples indicate argon loss from the glassy matrix, possibly caused by low-grade regional metamorphism during the Rangitata Orogeny.