Norfolk Ridge Research Articles

Composition and distribution of deep-sea benthic invertebrate megafauna on the Lord Howe Rise and Norfolk Ridge, southwest Pacific Ocean

The deep-sea biodiversity of the Lord Howe Rise and Norfolk Ridge – two complex submarine features that extend in a north-south direction either side of a deep basin within the northern Tasman Sea and southern Coral Sea – was sampled in 2003 for the first time on a broad regional scale. The total of 1313 megabenthic invertebrate species from 17 higher order taxa collected between 100 and 1800 m depths showed faunal diversity and novelty was high. Only 256 of these species were named, and 10% of these were described as a result of this survey; 78% are un-named and believed to be mostly new species. Of the 1253 species included in quantitative analyses, most appeared to be rare – 85% were only found once. This indicates intra-regional endemism may be high, but undersampling is also likely. Species accumulation curves confirm that many additional species remain to be collected. There was high regional-scale spatial heterogeneity in species distribution patterns which appeared to be influenced by hydrographic patterns and feature-scale topography, and to a lesser extent by seabed type. Depth and oxygen concentration (correlated with depth) had most influence on distribution patterns of fauna, with assemblages identified from three depth-zones: 100–400 m (deep continental shelf and shelf edge), 400–700 m (upper continental slope) and >700 m (mid-continental slope). In the shallowest depth zone, there were north-south (latitudinal) patterns in invertebrate assemblages that appeared to be influenced by water mass distribution. Species overlap was higher in the south than the north, probably due to the Tasman Front forming a hydrographic connection between the southern parts of the Rise and the Ridge at shallower depths. At depths >700 m, the absence of a latitudinal pattern in assemblage structure was attributed to the continuity of Antarctic Intermediate Water in the study area. Differentiation of two assemblages in sled samples from the >700 m depth zone, as well as some patterns of diversity of large sessile fauna between sub-regions within the study area, suggested a relationship with bottom type but this was not fully analysed. While providing a major increase in scientific knowledge of marine biodiversity in deep waters of the Coral and Tasman Seas, these results also highlighted the paucity of biogeographical knowledge that exists for the area. Some science advances needed to inform national and international conservation plans currently under development are identified. They include taxonomic standardisation at a regional-scale (Australia, New Zealand and New Caledonia) for informative higher level taxa, and some additional surveys of selected areas and seabed features, including off northeastern Australia.

Composition, distribution and regional affinities of the deepwater ichthyofauna of the Lord Howe Rise and Norfolk Ridge, south-west Pacific Ocean

Fishes were collected from seamounts and insular slopes of the northern Tasman and southern Coral Seas in the environs of the Reinga Ridge, Norfolk Ridge and Lord Howe Rise, at depths ranging from 49 to 1927 m. A total of 348 demersal fish species in 99 families, which were collected from 135 samples taken with a variety of sampling gear, greatly improved taxonomic knowledge of this poorly known area. Twenty five percent of the fish sampled are considered to be potentially new species. Relatively high levels of regional endemicity and diversity are attributed to geological history, and the complexity of contemporary climatology, hydrography and habitat diversity of the region. Fish assemblages were highly structured by depth, but across regions, deep-water fish faunas showed stronger taxonomic affinities than shallower faunas. Although less pronounced, spatial differences pointed towards distinct faunas between the southern and northern parts of the area. The distribution patterns and affinities to regions adjacent to the survey area indicate that (1) the fish fauna on the Lord Howe Rise near Lord Howe Island and further north is distinct from the rest of the survey regions, and exhibits eastern Australian and northern (Coral Sea) affinities, (2) the Northern Norfolk Ridge fauna is distinct from the other regions and has strong affinities with New Caledonia, (3) fishes on the Southern Norfolk Ridge, Western Norfolk Ridge and Lord Howe Plateau have more shared species compared to the other regions indicating a high level of connectedness and affinities with New Zealand fauna, and (4) some species have a wide distribution along the Norfolk Ridge providing a possible deepwater pathway between New Caledonia and New Zealand. Survey data is also useful for assessing the regions' conservation values by identifying rare or unusual components of the fauna, those with very limited distributions, those with low productivity that may be vulnerable to human disturbance (fishing, mining), and for defining bioregions.

Increasing variation in taxonomic distinctness reveals clusters of specialists in the deep sea

Changes in biodiversity with latitude or along a given environmental gradient have been described in many studies, including for marine ecosystems. Currently there is no scientific consensus, however, regarding macroecological patterns of diversity vs depth. Here, we describe variation in the biodiversity of fishes along a depth gradient from 0 to 2000 m in the region of the Norfolk Ridge and Lord Howe Rise (Western Pacific), using data obtained during the NORFANZ voyage. We modelled α diversity (richness), β diversiry (using Jaccard's coefficient), evenness, taxonomic distinctness and taxonomic resemblances among fish communities. Although α diversity did not change appreciably with depth, β diversity decreased significantly in deeper strata. Both taxonomic resemblances and Jaccard similarities diminished with depth, indicating convergence in community structure. In addition, average taxonomic distinctness showed no clear pattern with depth, but taxonomic trees constructed among species within deeper samples had more variable path-lengths than those in shallower samples. The presence of taxonomically distinct clusters of highly related species at depth indicates specialised niches that have developed in a relatively extreme (dark, pressurized) yet stable environment. We propose that reduced β diversity and increased variation in taxonomic distinctness might serve as indicators of ecological communities living in harsh environments ― α hypothesis that should be tested in other systems, such as deserts, high altitudes or latitudes.

Polyplacapros tyleri, a New Genus and Species ofOstraciid Trunkfish from off Eastern Australia and Norfolk Ridge

Polyplacapros tyleri, a New Genus and Species ofOstraciid Trunkfish from off Eastern Australia and Norfolk Ridge

Geochemistry and tectonic setting of Matakaoa Volcanics, East Coast Allochthon, New Zealand: Suprasubduction zone affinity, regional correlations, and origin

In north-eastern New Zealand, the Late Cretaceous to Eocene submarine volcanic rocks of the East Coast Allochthon referred to as Matakaoa Volcanics formed a dominantly mafic melange with minor abyssal sediments during the subduction of oceanic crust. Accreted and melanged pillow lavas and dolerites display the geochemical and isotopic features of tholeiites with some diversity referred to as midocean ridge basalts, island-arc tholeiites and back-arc basin basalts. The association of supra-subduction tholeiitic magmas, abyssal sediments and polymetallic volcanogenic sulphide deposits is typical of many back-arc basins; therefore, a correlation with the alkaline and transitional basalts of the Hikurangi-Manihiki- Ontong Java Plateau may be ruled out. These petrological features and the fossil ages as well, are closely similar to those of the Tangihua Complex (Northland Allochthon) and allow Matakaoa and Tangihua mafic volcanic rocks, now separated by the modern Havre Trough, to be correlated within one single Late Cretaceous to Eocene 2 basin. The consideration of possible younger ages (Oligocene) is also discussed. The occurrence of Late Cretaceous-Eocene oceanic crust with supra-subduction zone affinities to the east of the Norfolk Ridge poses the problem of the intervening southwest-dipping subduction, the missing Late Cretaceous-Eocene arc and their relationship with Southeast Gondwana marginal break-up.

Lithosphere delamination with foundering of lower crust and mantle caused permanent subsidence of New Caledonia Trough and transient uplift of Lord Howe Rise during Eocene and Oligocene initiation of Tonga-Kermadec subduction, western Pacific

[1] We use seismic reflection and rock sample data to propose that the first-order physiography of New Caledonia Trough and Norfolk Ridge formed in Eocene and Oligocene time and was associated with the onset of subduction and back-arc spreading at the Australia-Pacific plate boundary. Our tectonic model involves an initial Cretaceous rift that is strongly modified by Cenozoic subduction initiation. Hence, we are able to explain (1) complex sedimentary basins of inferred Mesozoic age; (2) a prominent unconformity and onlap surface of middle Eocene to early Miocene age at the base of flat-lying sediments beneath the axis of New Caledonia Trough; (3) gently dipping, variable thickness, and locally deformed Late Cretaceous strata along the margins of the trough; (4) platform morphology and unconformities on either side of the trough that indicate a phase of late Eocene to early Miocene uplift to near sea level, followed by rapid Oligocene and Miocene subsidence of ∼1100–1800 m; and (5) seismic reflection facies tied to boreholes that suggest absolute tectonic subsidence at the southern end of New Caledonia Trough by 1800–2200 m since Eocene time. The Cenozoic part of the model involves delamination and subduction initiation followed by rapid foundering and rollback of the slab. This created a deep (>2 km) enclosed oceanic trough, ∼2000 km long and 200–300 km across, in Eocene and Oligocene time as the lower crust detached, with simultaneous uplift and local land development along basin flanks. Disruption of Late Cretaceous and Paleogene strata was minimal during this Cenozoic phase and involved only subtle tilting and local reverse faulting or folding. Basin formation was possible through the action of at least one detachment fault that allowed the lower crust to either be subducted into the mantle or exhumed eastward into Norfolk Basin. We suggest that delamination of the lithosphere, with possible mixing of the lower crust back into the mantle, is more widespread than previously thought and may be commonly associated with subduction initiation, such as Cenozoic events in the Mediterranean and western Pacific.

Recent Brachiopoda from the Norfolk Ridge, New Caledonia, with description of four new species

Recent Brachiopoda from the Norfolk Ridge, New Caledonia, with description of four new species

Recent Brachiopoda from the Norfolk Ridge, New Caledonia, with description of four new species

Twenty-two brachiopod species belonging to 19 genera have been recognized in the material collected during two cruises, Norfolk 1 and Norfolk 2, to the Norfolk Ridge south of New Caledonia, at depths of 180 to 1150 m. Thirteen species are reported for the first time from this locality, while four genera, Aulites, Septicollarina, Annuloplatidia and Campages, are noted for the first time from the New Caledonian region. Thecidellina minuta is recorded for the first time from the Pacific. Four new species are described ― Cryptopora norfolkensis sp. nov., Aulites crosnieri sp. nov., Septicollarina zezinae sp. nov. and Annuloplatidia richeri sp. nov. The distribution of the particular species and their abundance vary considerably between the 15 sampled seamounts, with Stenosarina crosnieri and Fallax neocaledonensis being most widely distributed, and the seamount Crypthelia having the highest biodiversity. The seamount brachiopods show considerable affinity to the brachiopods of adjacent regions, and only three species ― C. norfolkensis, A. crosnieri and A. richeri ― can be regarded as potential endemics. The brachiopod fauna is more similar to that in the area around Fiji than to that around Australasia.

Testing biodiversity hypotheses in New Caledonia using phylogenetics

Testing biodiversity hypotheses in New Caledonia using phylogenetics

Notoraja sapphira sp. nov. (Rajoidei: Arhynchobatidae), a new deepwater skate from the slopes of the Norfolk Ridge (South-West Pacific)

A new arhynchobatid skate of the genus Notoraja is described from five specimens collected on the slopes of the Norfolk Ridge between 1195 and 1313 m depth. The new species is distinct from its sibling species from southern Australian waters, the Blue Skate (N. azurea), by its smaller size, several morphometric and meristic characters, thorn pattern and dorsal and ventral coloration.

Origin, diversification, and systematics of the New Zealand skink fauna (Reptilia: Scincidae)

The diverse scincid lizard fauna of the largely submerged subcontinent of Zealandia (which incorporates New Zealand, New Caledonia, Lord Howe Island, Norfolk Island, and the Chatham Islands) forms a monophyletic lineage within the Eugongylus group of skinks. We use 4062 bp of mitochondrial (ND2, ND4, Cytochrome b, 12SrRNA, 16SrRNA) and nuclear (Rag-1) DNA sequence data to recover a molecular phylogeny for the New Zealand skink fauna, and investigate the origin and diversification of skinks in New Zealand. Our phylogeny includes 32 of the 33 extant described New Zealand skink species ( Cyclodina and Oligosoma), the Lord Howe Island skink ( C. lichenigera), and representatives from several New Caledonian genera. Neighbour-joining, Maximum Parsimony, Maximum Likelihood, and Bayesian phylogenetic analyses are used to demonstrate that the New Zealand skink species form a single monophyletic lineage, with C. lichenigera representing a closely related sister lineage to the New Zealand radiation. Our relaxed molecular clock analyses indicate that skinks colonised New Zealand in the early Miocene (16–22.6 mya), shortly after the ‘Oligocene drowning’ event (∼25 mya). We propose that skinks reached New Zealand from New Caledonia via long-distance overwater dispersal, with C. lichenigera persisting on volcanic islands along the Lord Howe Rise and Norfolk Ridge. Eight major genetic clades are evident within the New Zealand skink fauna, with the divergences among these clades during the early to mid-Miocene resulting in distinct open habitat, forest, and coastal radiations. Subsequent diversification in the late Miocene–Pliocene appears to coincide with tectonic activity along the Alpine Fault and the uplift of the Southern Alps. We were unable to resolve the phylogenetic affinities of O. suteri, New Zealand’s only native oviparous skink. We use the phylogeny and topology tests to resolve several taxonomic issues and assess the taxonomic status of several suspected undescribed taxa. We complete a generic revision for the New Zealand skink fauna, placing C. lichenigera and all native New Zealand species into a single genus.

Shallow genetic and morphological divergence among seaperches in the South Pacific (family Scorpaenidae; genus Helicolenus)

The phylogenetic relationships among populations of seaperch, Helicolenus spp., in the south-west Pacific were examined with mtDNA markers. Parts of the cytochrome b gene [459 base pair (bp)] and the control region (448 bp) were sequenced in 58 specimens from the south-west Pacific and four specimens of Helicolenus lengerichi from Chile. Only one clade was recognized in New Zealand coastal waters, despite a wide range of colour morphs. This clade also occurred in the mid Tasman Sea on the Norfolk Ridge and around Tasmania and Victoria. A second sympatric clade was identified around Tasmania and Victoria and to the west of New Zealand. A third allopatric clade was identified to the north of New Zealand and in deep water on the Chatham Rise and a fourth clade on the Foundation Seamounts and the Louisville Ridge. Helicolenus lengerichi from Chile formed a fifth clade. Assuming a molecular clock, the clades were estimated to have diverged c. 0.7-2.6 million years ago. Only two clades, around Tasmania and Victoria, were separated using morphology, colour (in live) and dorsal-fin soft ray counts and were confirmed as Helicolenus percoides and Helicolenus barathri. Two characters, orbit diameter and colour variation, previously used to identify two species in New Zealand waters were unreliable characters for species discrimination. Principle component analyses of 11 morphological measures from 67 individuals did not delineate the clades. A canonical discriminant analysis was able to separate four of the five clades, but mean discriminate probabilities were low (77.6%), except for the five Chilean specimens of H. lengerichi (100%).

A new species of the flathead genus Onigocia (Teleostei: Platycephalidae) collected from the Coral and Tasman Seas

A new species of platycephalid, Onigocia lacrimalis, is described on the basis of specimens collected from the Chesterfield Islands (Coral Sea) and Norfolk Ridge (Tasman Sea), at depths of 111–330 m. Onigocia lacrimalis differs from the six congeners of the genus in having 12–13 (usually 12) second dorsal-fin rays, 12 anal-fin rays, 21–25 pectoral-fin rays, 8 branched caudal-fin rays, anterior 2–4 scales of the lateral line with a spine, and a single preocular spine, and in lacking gill rakers on the upper arch, ocular and interopercular flaps, and distinct antrorse lachrymal spines.

What we know (and what we don't) about the petroleum prospectivity of the Northland Basin, North Island, New Zealand

The offshore Northland Basin is a major sedimentary accumulation lying to the west of the Northland Peninsula of New Zealand. It merges with the Taranaki Basin in the south and its deeper units are separated from Deepwater Taranaki by a buried extension of the West Norfolk Ridge. Sedimentary thicknesses increase to the northwest and the Northland Basin may extend into Reinga. Its total area is at least 65,000 km2 and if the Reinga Basin is included, it may be up to 100,000 km2. As in Taranaki, petroleum systems of the Northland Basin were thought to include Cretaceous to Recent sedimentary rocks. Waka Nui–1 was drilled in 1999 and penetrated no Cretaceous sediments, but instead drilled unmetamorphosed Middle Jurassic coal measures. Economic basement may be older meta-sediments of the Murihiku Supergroup. Thick successions onlap the dipping Jurassic unit and a representative Cretaceous succession is likely to be present in the basin. Potential source rocks known to be present include the Middle Jurassic coal measures of Waka Nui–1 and the Waipawa Formation black shale. Inferred source rocks include Late Jurassic coaly rocks of the Huriwai Beds, the Early Cretaceous Taniwha Formation coaly sediments, possible Late Cretaceous coaly units and lean but thick Late Cretaceous and Paleogene marine shales. Below the voluminous Miocene volcanoes of the Northland arc, the eastern margin of the basin is dominated by a sedimentary wedge that thickens to more than two seconds two-way travel time (TWT), or at least 3,000 m, at its eastern margin and appears to have been thrust to the southwest. This is interpreted to be a Mesozoic equivalent of the Taranaki Fault, a back-thrust to subduction along the Gondwana Margin. The ages of sedimentary units in the wedge are unknown but are thought to include a basal Jurassic succession, which dips generally to the east and is truncated by an erosional unconformity. A southwestwards-prograding succession overlies the unconformity and its top surface forms a paleoslope onlapped by sediments of Late Cretaceous to Neogene ages. The upper succession in the wedge may be of Early Cretaceous age—perhaps the equivalent of the Taniwha Formation or the basal succession in Waimamaku–2. The main part of the basin was rifted to form a series of horst and graben features. The age of initial rifting is poorly constrained, but the structural trend is northwest–southeast or parallel to the Early Cretaceous rifting of Deepwater Taranaki and with the Mesozoic Gondwana margin. Thick successions overlie source units which are likely to be buried deeply enough to expel oil and gas, and more than 70 slicks have been identified on satellite SAR data suggesting an active petroleum system. Numerous structural and stratigraphic traps are present and the potential of the Northland Basin is thought to be high.

The Recent Pectinoidea of the New Zealand region (Mollusca: Bivalvia: Propeamussiidae, Pectinidae and Spondylidae)

The Recent Pectinoidea of the New Zealand region are reviewed. Eight new species are described from the New Zealand Exclusive Economic Zone: Parvamussium cancellorum, Cyclochlamys austrina, Cc. delli, Cc. irregularis, Cc. munida, Cc. pileolus, Cyclopecten fluctuosus, and Catillopecten tasmani. Nine species are new records for New Zealand: Parvamussium retiolum Dijkstra, 1995, Pa. vesiculatum Dijkstra, 1995, Sinepecten segonzaci Schein, 2006, Ciclopecten fluctuatus (Bavay, 1905), Pseudamussium challengeri (E.A. Smith, 1891), Spondylus occidens G.B. Sowerby III, 1903, S. proneri Lamprell Healy, 2001, S. sparsispinosus Dall, Bartsch Rehder, 1938, and S. jamarci Okutani, 1983. Cyclochlamys bacata and Cc. wanganellica are described from Wanganella Bank, West Norfolk Ridge, and Cyclopecten textus from the Lord Howe Rise. We provide new distribution records for Catillopecten murrayi (E.A. Smith, 1885), Spondylus asperrimus G.B. Sowerby II, 1847 and S. proneri in the south-west Pacific. Cyclopecten aupouria Powell, 1937 and Cp. mestayerae Dell, 1956 are newly referred to genus Cyclochlamys Finlay, 1926; Pecten challengeri E.A. Smith, 1891 is referred to Pseudamussium Mörch, 1853. Bathypecten Schein-Fatton, 1985 is newly synonymised with Catillopecten Iredale, 1939; and Chlamys consociata E.A. Smith, 1915 is newly synonymised with Talochlamys dichroa (Suter, 1909). Brooding is recorded for the first time in Cyclochlamys, and is also the first record in Propeamussiidae. Pronounced sculptural change in response to settlement of sponge on the shell is recorded in Talochlamys dichroa and Zygochlamys delicatula.

New SW Pacific tectonic model: Cyclical intraoceanic magmatic arc construction and near‐coeval emplacement along the Australia‐Pacific margin in the Cenozoic

Various reconstructions of the SW Pacific for the Late Cretaceous and Cenozoic suggest that northeast dipping subduction began in the South Loyalty Basin (SLB) at 55–50 Ma and that subsequent closure of the SLB resulted in the diachronous emplacement of Cretaceous‐Paleocene ophiolitic nappes onto the Norfolk Ridge in New Caledonia at 40–34 Ma and in Northland, New Zealand, around 24–21 Ma. A fundamental problem with these models is that they do not account for the fact that NE dipping subduction had already been established offshore Papua New Guinea by at least 65–60 Ma which resulted in the emplacement of the Papuan Ultramafic Belt (PUB) ophiolite at 59–58 Ma. A second issue is that the reconstructions are based largely upon unfounded assumptions as to the age and nature of the basement beneath the Loyalty arc and Three Kings Ridge. Finally, reconstructions of the Northland region are based upon the erroneous assumption that the age of the majority of the igneous component comprising the Northland allochthon is Late Cretaceous‐Paleocene, when in fact it is Oligocene. A new model is presented whereby the PUB, New Caledonia, and Northland ophiolites formed and were emplaced in a cyclical fashion above an extensive NE dipping Cenozoic intraoceanic arc system which diachronously propagated (N‐S) along the entire eastern margin of the Australian Plate. These “infant arc” ophiolites represent fragments of suprasubduction zone lithosphere (SSZL) generated in the earliest stages of magmatic arc formation that were emplaced shortly after (<20 m.y.) as a result of forearc‐Australian Plate collision. Subduction inception was the result of subsidence of older MORB‐like lithosphere generated within an extensive “back arc basin” to the east of the Norfolk Ridge during the earliest stages of SLB formation above a southwest dipping Pacific Plate. During emplacement of each ophiolite, a crustal fragment of the older lithosphere was scraped off the NE dipping slab and subsequently back‐thrust beneath each ophiolite during its emplacement.

First record of Centrophorus harrissoni from New Zealand, with observations on squamation in centrophoridae (squaliformes)

Three specimens of Centrophorus from the southern Norfolk Ridge, three Kings Ridge, and Kermadec Ridge are provisionally identified as C. harrissoni, extending the species’ known range east to 178°52.1'W. Although apparently rare, C. harrissoni is widely distributed in southern Australian waters and the southwest Pacific between 17°S and 43°S, occurring on continental and insular slopes and oceanic ridges from 450 to 1048 m depth. Differences in dental morphology between juvenile male and female type specimens, a juvenile male from southern Norfolk Ridge and an adult male from the Kermadec Ridge were tentatively attributed to sexual dimorphism. However, additional specimens and research are required to confirm the identity of nominal C. harrissoni from Norfolk Ridge and northern New Zealand. Eight Centrophorus spp., including C. harrissoni, and three Deania spp. were found to differ from C. squamosus in having an area of transverse dermal folds on the ventral surface of the head between the gills. in C. harrissoni and Deania spp. these are naked except for a row of denticles along the top of each fold. in C. harrissoni these denticles are minute and thorn‐like, whereas in Deania spp. they have tridentate crowns on short, straight pedicles.

Provenance comparisons of Permian to Jurassic tectonostratigraphic terranes in New Zealand: perspectives from detrital zircon age patterns

U–Pb detrital zircon ages (LAM-ICPMS) are reported for 20 greywackes and sandstones from seven major tectono-stratigraphic terranes of the Eastern Province of New Zealand (Cretaceous to Carboniferous) to constrain sediment provenances. Samples are mainly from three time horizons: Late Permian, Late Triassic and Late Jurassic. Age datasets are analysed as percentages in geological intervals, and in histogram and cumulative probability diagrams. The latter discriminate significant zircon age components in terms of terrane, sample stratigraphic age, component age, precision and percentage (of total set). Zircon age distributions from all samples have persistent, large Triassic–Permian, and very few Devonian–Silurian, populations, features which exclude a sediment provenance from the early Palaeozoic, Lachlan Fold Belt of southeast Australia or continuations in New Zealand and Antarctica. In the accretionary terranes, significant Palaeozoic (and Precambrian) zircon age populations are present in Torlesse and Waipapa terranes, and variably in Caples terrane. In the fore-arc and back-arc terranes, a unimodal character persists in Murihiku and Brook Street terranes, while Dun Mountain–Maitai terrane is more variable, and with Caples terrane, displays a hybrid character. Required extensive Triassic–Permian zircon sources can only be found within the New England Fold Belt and Hodgkinson Province of northeast Australia, and southward continuations to Dampier Ridge, Lord Howe Rise and West Norfolk Ridge (Tasman Sea). Small but significant Palaeozoic (and Precambrian) age components in the accretionary terranes (plus Dun Mountain–Maitai terrane), have sources in hinterlands of the New England Fold Belt, in particular to mid-Palaeozoic granite complexes in NE Queensland, and Carboniferous granite complexes in NE New South Wales. Major and minor components place sources (1) for the older Torlesse (Rakaia) terrane, in NE Queensland, and (2) for Waipapa terrane, in NE New South Wales, with Dun Mountain–Maitai and Caples terrane sources more inshore and offshore, respectively. In Early Jurassic–Late Cretaceous, Torlesse (Pahau) and Waipapa terranes, there is less continental influence, and more isolated, offshore volcanic arc sources are suggested. There is local input of plutonic rock detritus into Pahau depocentres from the Median Batholith in New Zealand, or its northward continuation on Lord Howe Rise. Excepting Murihiku and Brook Street terranes, all others are suspect terranes, with depocentres close to the contemporary Gondwanaland margin in NE Australia, and subsequent margin-parallel, tectonic transport to their present New Zealand position. This is highlighted by a slight southeastward migration of terrane depocentres with time. Murihiku and Brook Street terrane sources are more remote from continental influences and represent isolated offshore volcanic depocentres, perhaps in their present New Zealand position.

Oligocene–Miocene tectonic evolution of the South Fiji Basin and Northland Plateau, SW Pacific Ocean: Evidence from petrology and dating of dredged rocks

We present new analytical data from lavas and associated rocks dredged and/or drilled from the South Fiji Basin, Northland Plateau, Colville Ridge and Havre Trough. These results provide much-needed ground truth about the geology, age and tectonic evolution of the Cenozoic submarine ridges and basins between the active intraoceanic Tonga–Kermadec arc, and rifted continental borderlands of New Zealand, the Norfolk Ridge and New Caledonia. Key results from this study include: (1) Ar–Ar dates on Minerva Abyssal Plain oceanic crust suggest that the ages of magnetic anomalies in the South Fiji Basin have been overestimated by earlier workers; (2) subduction-related lavas are widespread across the region, are not presently organised into arc-like chains, and cluster in the age range 22–18 Ma (Early Miocene); (3) the oldest subduction-related lavas occur in the western part of the region (32–26 Ma: Norfolk and Three Kings Ridge); (4) shoshonites, interpreted as rifted arc lavas, were erupted in a narrow 20–21 Ma interval over a wide area. Put together, these results indicate high magmatic flux and large and rapid horizontal tectonic translations and basin opening from 18–23 Ma in the region immediately north of New Zealand. We explain the Miocene tectonomagmatic development of the region by a model of rapid rollback of a single, east-facing Pacific arc–trench system that became established after Northland Allochthon emplacement. Critical testing of this, versus other, tectonic models must await drilling and dating of thus-far unsampled Kupe Abyssal Plain crust.

DNA and meristic evidence for two species of giant stargazer (Teleostei: Uranoscopidae: Kathetostoma) in New Zealand waters

The taxonomic status of the banded giant stargazer in New Zealand waters is uncertain. Mitochondrial DNA partial sequences of the cytochrome b gene and the control region, along with three meristic characters (numbers of dorsal fin rays, anal fin rays, and vertebrae), were compared among six recognised species of Kathetostoma and specimens of the banded giant morph. New Zealand specimens referred to as banded giant stargazer were shown to be a discrete species distinguished from the giant stargazer K. giganteum from New Zealand and the banded K. laeve and K. canaster from Australia, by cytochrome b and control region sequences and meristic counts. This undescribed species occurs over a wide geographic range from the Snares shelf (48°S) to the Norfolk Ridge (32°S) in the Tasman Sea, and is largely sympatric with K. giganteum. The two New Zealand species occupy different depth ranges, with the banded giant stargazer generally occurring in shallower water (<320m) than K. giganteum (12–1000 m).