Norfolk Ridge Research Articles

Dichichthyidae, a New Family of Deepwater Sharks (Carcharhiniformes) from the Indo–West Pacific, with Description of a New Species

The genus Dichichthys was resurrected for five species previously allocated to the genus Parmaturus in the family Pentanchidae. Supraorbital crests on the chondrocranium distinguish Dichichthys from Parmaturus and other members of the family Pentanchidae. A new family, Dichichthyidae, has been proposed to contain Dichichthys. The sequence of the NADH2 mitochondrial gene confirms the placement of Dichichthys outside of the Pentanchidae family, as well as separate from the Atelomycteridae and Scyliorhinidae families. Dichichthys albimarginatus was described using a holotype collected off the coast of New Caledonia. A second juvenile specimen collected off the coast of Papua New Guinea was tentatively assigned as D. cf. albimarginatus. Dichichthys bigus is known from the holotype collected in the Coral Sea off the coast of Queensland, Australia. A new, parasite-afflicted underwater observation was reported further north of Queensland. The type species Dichichthys melanobranchus, previously only known from juvenile specimens, was redescribed based on adult specimens. Dichichthys nigripalatum is known from the holotype collected off Sumbawa, Indonesia, and a tentatively identified photo record from West Java. Dichichthys satoi n. sp. is described from the West Norfolk Ridge and off the North Island of New Zealand. Members of the genus Dichichthys have unique curved egg cases which have pliable ridges made up of numerous fibres and long coiled tendrils on the posterior end.

Beyond zircon fingerprinting: Zircon and TiO2 polymorphs constrain genealogy and evolution of the New Caledonian ophiolite

Ophiolitic mantle rocks play a crucial role in understanding deep geochemical cycling and the transfer of components associated with slab-mantle interactions. Geochemical and geochronological and geochemical analysis of zircon and TiO2 polymorphs (e.g., rutile) present within mantle rocks of the Eocene New Caledonian ophiolite reveal discrete magmatic and xenocrystic populations amongst harzburgite from Me Maoya and chromitite from Tiébaghi massifs. Most mineral grains examined have a xenocrystic origin and are concentrated particularly in the harzburgite. Source tracking involved the use of UPb dating and trace element analysis. They are inferred to have been recycled from the northern end of the Norfolk Ridge that formed the leading edge of a thin continental slab of Gondwana affinity which had previously rifted from eastern Australia together with other elements of Zealandia. The slab was drawn into an intra-oceanic subduction zone beneath the proto-Loyalty arc immediately before the emplacement of the forearc ophiolite today represented by the New Caledonian Peridotite Nappe. Geochemical and geochronological data of these xenocrystic grains support a scenario in which these minerals were recycled into the mantle wedge at moderate mantle depths (above 60–80 km depth) within the subduction channel. In contrast, Eocene UPb ages of zircon and rutile grains, mostly found within the Tiébaghi chromitite, imply their formation through magmatic processes. These minerals' distinctive geochemical characteristics (e.g., HFSE enrichment in rutile) likely indicate an association with late-stage percolation of relatively enriched fluids and melt. Overlapping ages of the Eocene zircon and rutile grains, ArAr pargasite ages, and Zircon UPb ages of cross-cutting dikes in the Tiébaghi chromitite provide evidence that it cooled at ca. 47–46 Ma. This study demonstrates that mineral geochemistry of mantle rocks, when combined with data from geochronology, mineralogy, and petrology, is critical to enhance our comprehension of forearc mantle wedge evolution. It also highlights the potential for studying recycled solid mineral phases, tracing their thermal evolution, and characterizing potential subducted source terranes.

The Norfolk Ridge: A Proximal Record of the Tonga‐Kermadec Subduction Initiation

AbstractNorfolk Ridge bounds the northeastern edge of the continent of Zealandia and is proximal to where Cenozoic Tonga‐Kermadec subduction initiation occurred. We present and analyze new seismic reflection, bathymetric and rock data from Norfolk Ridge that show it is composed of a thick sedimentary succession and that it was formed and acquired its present‐day ridge physiography and architecture during Eocene to Oligocene uplift, emergence and erosion. Contemporaneous subsidence of the adjacent New Caledonia Trough shaped the western slope of Norfolk Ridge and was accompanied by volcanism. Neogene extension along the eastern slope of Norfolk Ridge led to the opening of the Norfolk Basin. Our observations reveal little or no contractional deformation, in contrast to observations elsewhere in Zealandia, and are hence significant for understanding the mechanics of subduction initiation. We suggest that subduction nucleated north of Norfolk Ridge and propagated rapidly along the ridge during the period 40‐35 Ma, giving it a linear and narrow shape. Slab roll‐back following subduction initiation may have preserved the ridge and created its eastern flank. Our observations suggest that pre‐existing structures, which were likely inherited from Cretaceous Gondwana subduction, were well‐oriented to propagate rupture and create self‐sustaining subduction.

Potential tsunami hazard of the southern Vanuatu subduction zone: tectonics, case study of the Matthew Island tsunami of 10 February 2021 and implication in regional hazard assessment

Abstract. The Vanuatu subduction zone (VSZ) is known to be seismically very active, due to the high convergence rate between the Australian and Pacific tectonic plates for the majority of the margin. However, this is not the case on its southernmost part south of latitude 22.5∘ S and east of longitude 170∘ E, which is neither highly tectonically active nor has it produced large tsunamis over the past 150 years. It has also not been widely studied. On the 11 February 2021 (10 February UTC), a magnitude Mw 7.7 earthquake triggered a tsunami warning in New Caledonia and Vanuatu 20 min after midnight (local time). With an epicentre located close to the volcanic islands of Matthew and Hunter, this shallow reverse-faulting rupture (< 30 km depth) was able to deform the seabed and produce a tsunami. This was confirmed 45 min later by the coastal gauges of the Loyalty and the south Vanuatu islands, which recorded the first tsunami waves. Showing a typical recorded amplitude of less than 1 m, with a maximum of ∼ 1.5 m in Lenakel (Tanna, Vanuatu), it was observed on most coastal gauges and DART stations in the south-west Pacific region as far as Tasmania to the south and Tuvalu to the north at distances of ∼ 3000 and ∼ 1800 km from the epicentre. In this study, the tsunamigenic potential of the southernmost part of the VSZ and the implications in terms of regional hazard assessment are discussed through (1) the presentation of the complex tectonic settings of this “transition zone” between the Solomon–Vanuatu and the Tonga–Kermadec trenches, (2) the case study of the 10 February 2021 tsunami at a south-west Pacific regional scale using three different tsunami generation scenarios computed with the COMCOT modelling code on a set of 48 nested bathymetric grids, and (3) the simulation of a plausible Mw 8.2 scenario encompassing the active part of this “transition zone”. The validation of the Mw 7.7 parameters for tsunami modelling provides the means to further assess the hazard from potential tsunamis triggered by higher magnitude earthquakes in this region. Tsunami records highlight that > 28 cm wave amplitudes were recorded at eight different coastal gauges, including one with an amplitude of more than 1 m (Lenakel, Tanna, Vanuatu). The tsunami threat at that location would be large enough to warrant an onshore evacuation. Finally, it helps to highlight the significant role played by the numerous submarine features in the region, the Norfolk Ridge being the most important, which acts like a waveguide from the north to the south.

First record of genus Phlyctaenopora in South Pacific waters

Four species of Phlyctaenopora Topsent, 1904 (Demospongiae Sollas, Poecilosclerida Topsent, Mycalidae Lundbeck) are recognised today (Van Soest et al. 2021a) (Table 1): two Atlantic Ocean species in subgenus Phlyctaenopora [type species P. (P.) bitorquis Topsent, 1904, from the Azores; P. (P.) halichondrioides van Soest Stentoft, 1988, from Barbados]; and two Southern Hemisphere species in subgenus Barbozia Dendy, 1922: P. (Barbozia) primitiva Dendy, 1922, from the Seychelles, and P. (B.) bocagei Lévi Lévi, 1983, from New Caledonia. Here we describe a new species of Phlyctaenopora from Wanganella North in International Waters on the West Norfolk Ridge, northwest of New Zealand. Phlyctaenopora (B.) spina sp. nov. provides a first record of the genus in the South Pacific, providing further confirmation of the integrity of the subgenus Barbozia.

Notoraja hesperindica sp. nov., a new colorful deep-sea softnose skate (Elasmobranchii, Rajiformes, Arhynchobatidae) and first generic record from the western Indian Ocean

A new deep-sea softnose skate, Notoraja hesperindica, is described based on six specimens caught in 1230–1600 m depths off southern Mozambique and northwestern Madagascar in the western Indian Ocean. The new species is a medium-sized species of Notoraja Ishiyama, 1958 reaching a total length of at least 539 mm. It is the only Notoraja species known from the western Indian Ocean and differs from most congeners in the intense dark blue-grayish coloration. The only congeners with similarly vibrant coloration are Notoraja azurea McEachran & Last, 2008 from off southern Australia and Notoraja sapphira Seret & Last, 2009 from the Norfolk Ridge (Coral Sea and Tasman Sea), which differ from the new species in a shorter and more obtusely angled snout, a shorter head, a shorter disc, and smaller dorsolateral tail thorns, as well as more predorsal tail and total predorsal vertebrae and more pectoral-fin radials. The large dorsolateral tail thorns also distinguish the new species from most congeners except for the eastern Pacific Notoraja martinezi Concha, Ebert & Long, 2016, which has even larger, randomly patterned dorsolateral tail thorns that give the tail a barbedwire-like appearance. This congener further differs from N. hesperindica sp. nov. in the absence (vs. presence) of malar thornlets, fewer median tail thorns, a shorter snout, more tooth rows in upper and lower jaws, and more pectoral radials. A key to the species of Notoraja in the Indian Ocean is provided.

Apprehending novel biodiversity redux – thirteen new genera and three new families of Zealandian Bryozoa, with the first living species of the Eocene‒Miocene genus Vincularia (Vinculariidae)

AbstractThirteen new genera and three new families of cheilostome Bryozoa are described from the New Zealand biogeographic region, centred on Zealandia, between 26.42° (northern Norfolk Ridge) and 54.02°S latitude (south-east Campbell Plateau) from coastal waters to bathyal depths (46‒1676 m). The new genera, comprising 15 new and one previously described Zealandian species, are: Elementella (Elementellidae n. fam.), Niwapora, Quasicallopora, Quitocallopora, Judyella (Calloporidae), Ellisantropora (Antroporidae), Rhizellisina (Ellisinidae), Radixenia (Calloporoidea incertae sedis), Granomurus (Granomuridae n. fam.), Carolanna (Bugulidae), Borioplebs (Borioplebidae n. fam.), Seabournea (Cribrilinidae) and Waeschenbachia (Romancheinidae). A new Recent species of the otherwise Eocene‒Miocene genus Vincularia is also described from deep water on the Three Kings Ridge. Two new combinations are created – Judyella precocialis (Gordon, 1984) and Ellisantropora aggregata (Gordon, 1984). Ellisantropora tilbrooki sp. nov. is also introduced for a species from Torres Strait. Four of the deep-sea genera (three from one station on the northern Norfolk Ridge, one from a station on the Three Kings Ridge) have species with plesiomorphies or distinctive skeletal characters that suggest they are relict. Almost half of the new species form spot-like colonies on hard substrata.

The Norfolk Ridge seamounts: Eocene–Miocene volcanoes near Zealandia’s rifted continental margin

New age and geochemical data are used to investigate the origin of a ∼670 km-long line of eight seamount volcanoes along the western side of the Norfolk Ridge between New Caledonia and New Zealand. Altered lavas and limestones were dredged from three volcanoes during the 2015 Volcanic Evolution of South Pacific Arcs cruise of N/O l’Atalante, so a total of four, including the northernmost and southernmost, have now been directly sampled and analysed. Dating of lava and volcanic breccia clasts by Ar–Ar methods gives north-to-south ages from these sites of 31.3 ± 0.6, 33 ± 5, 21.5 ± 1.0 and 26.3 ± 0.1 Ma. These ages, along with supporting stratigraphic data on a fifth seamount from IODP borehole U1507, provisionally refute the hypotheses that the seamounts represent a southward-younging, age-progressive, intraplate volcanic chain on the Australian Plate or a subduction-related chain of restricted age range. Geochemically, the upper Eocene to lower Miocene lavas have alkaline and subalkaline basaltic compositions, and some could be shoshonitic. The location of the volcanoes along the western side of the Norfolk Ridge suggests an origin related to late Eocene and early Miocene melting near an intracontinental lithosphere–asthenosphere step. Involvement of a deep slab in petrogenesis is also possible. KEY POINTS Eight seamounts form a line along the Norfolk Ridge. Dating and geochemistry indicate the seamount line is not a hotspot track. A rift-related origin, possibly with influence by subduction, is proposed.

Eocene (46–44 Ma) Onset of Australia‐Pacific Plate Motion in the Southwest Pacific Inferred From Stratigraphy in New Caledonia and New Zealand

AbstractThe Pacific plate circuit went through a complex reorganization during the early to middle Eocene, approximately coinciding with the onset of subduction along the western Pacific margin. However, the timing and dynamics of this change in the southwest Pacific and evolution of subduction beneath the Tonga‐Kermadec Arc are not fully resolved. We present magneto‐biostratigraphic data from an early to middle Eocene sedimentary section exposed in the Koumac‐Gomen area, New Caledonia, which is an emerged portion of the Norfolk Ridge. The 260 m‐thick succession contains a transition from pelagic micrite to terrigenous‐rich calciturbidite that is observed regionally in New Caledonia and which is interpreted to represent a shift from sedimentation on a stable submarine plateau to slope formation developed under a convergent tectonic regime. The stratigraphic contact between pelagic micrite and overlying calciturbidite is not exposed, but our magnetic polarity‐based chronology constrains the age of transition to 46–44 Ma, in agreement with the 45.3 Ma age recently obtained from the Noumea area in southern New Caledonia. We integrate records from New Caledonia with recent magnetostratigraphic data from South Island, New Zealand, where marked variations in terrigenous input occurred during the early and middle Eocene. Synchronous sedimentary changes in the southwest Pacific occurred at the same time as onset of rapid seafloor spreading south of Australia and New Zealand. We infer that the underlying cause of stratigraphic change was inception of slip at a new configuration of the Australia‐Pacific plate boundary, which evolved into the Tonga‐Kermadec subduction system.

Eocene to Miocene Subduction Initiation Recorded in Stratigraphy of Reinga Basin, Northwest New Zealand

AbstractReinga Basin, northwest of New Zealand, contains deformed Cretaceous and Cenozoic strata, flat unconformities interpreted as sea level‐modulated erosion surfaces, and volcanics. Marine conditions since the Late Cretaceous resulted in deposition of thick sequences of fossil‐rich sediments. We present a seismic stratigraphic analysis that is tied to dredged rock samples and International Ocean Discovery Program Site U1508. The Cenozoic tectonic evolution of Reinga Basin comprises four phases. (1) Folding was accompanied by uplift from lower bathyal water depths at 56–43 Ma along West Norfolk Ridge, where wave ravinement surfaces were cut. (2) Basin‐wide compression and reverse faulting at 39–34 Ma exposed Eocene and older strata along the northeastern basin margin and farther south in western New Zealand. (3) Emplacement of South Maria Allochthon at 34–28 Ma along the northeast margin postdated thick‐skinned reverse faulting and folding, was broadly synchronous with the onset of basin volcanism, and immediately predated wave ravinement of nearby ridges. Normal faulting disrupted the western basin margin at this time. (4) During the final phase of the Reinga Basin deformation, South Maria Ridge subsided ∼1,000–2,000 m from the middle shelf to bathyal depths after 23–19 Ma, and the deformation migrated southeastwards. The Northland Allochthon was emplaced at 23–20 Ma, and Northland volcanism with confirmed arc character occurred at 23–12 Ma. The early Eocene onset of tectonic activity recorded by deformation in Reinga Basin is shown to be older than previously recognized and broadly synchronous with other events related to subduction initiation and plate motion change elsewhere in the western Pacific.

Chapter 5 The Eocene Subduction–Obduction Complex of New Caledonia

Abstract Convergence and subduction started in the Late Paleocene, to the east of New Caledonia in the South Loyalty Basin/Loyalty Basin, leading to the formation of the Subduction–Obduction Complex of Grande Terre. Convergence during the Eocene consumed the oceanic South Loyalty Basin and the northeasternmost margin of Zealandia (the Norfolk Ridge). The attempted subduction of the Norfolk Ridge eventually led to the end-Eocene obduction. Intra-oceanic subduction started in the South Loyalty Basin, as indicated by high-temperature amphibolite (56 Ma), boninite and adakite series dykes (55–50 Ma) and changes in the sedimentation regime (55 Ma). The South Loyalty Basin and its margin were dragged to a maximum depth of 70 km, forming the high-pressure–low-temperature Pouébo Terrane and the Diahot–Panié Metamorphic Complex, before being exhumed at 38–34 Ma. The obduction complex was formed by the stacking from NE to SW of several allochthonous units over autochthonous Zealandia, including the Montagnes Blanches Nappe (Norfolk Ridge crust), the Poya Terrane (the crust of the South Loyalty Basin) and the Peridotite Nappe (the mantle lithosphere of the Loyalty Basin). A model of continental subduction accepted by most researchers is proposed and discussed. Offshore continuations and comparable units in Papua New Guinea and New Zealand are presented.

Chapter 6 The Loyalty Islands and Ridge, New Caledonia

Abstract The Loyalty Ridge lies to the east and NE of the Norfolk Ridge. The three main Loyalty Islands (Maré, Lifou and Ouvéa) emerge from the ridge at the same latitude as Grande Terre. The islands are uniformly composed of carbonate deposits, except for Maré, where Middle Miocene intra-plate basalts and associated volcaniclastic rocks form restricted outcrops. Miocene rhodolith limestones constitute the bulk of the carbonate cover of the three islands. On Maré, these platform accumulations are locally topped by a dolomitic hardground, which, in turn, is covered by Pliocene–Pleistocene coral-bearing formations. These coral reef constructions are preserved as elevated rims over all three islands and define an atoll stage in their development. The Pleistocene–Holocene palaeoshoreline indicators include fringing bioconstructions and marine notches and record both eustatic sea-level changes and tectonic deformation. The ridge has been in the forebulge region in front of the active Vanuatu subduction zone since the Pliocene and each of the three islands has been uplifted and tilted to varying degrees. Offshore, the Loyalty Ridge continues northwards to the d'Entrecasteaux Zone and southwards to the Three Kings Ridge. Although typically volcanic, the nature of the deep Loyalty Ridge remains unknown.

Chapter 1 Introduction to New Caledonia: geology, geodynamic evolution and mineral resources

Supplementary material: List and content of the GIS files (ESRI format) corresponding to the geological map (Fig. 1.2) and the database structure of Figure 1.3 are available at https://doi.org/10.6084/m9.figshare.c.4984385 New Caledonia is a French overseas territory in the SW Pacific, located in the southern tropical zone between 19 and 24° S. The country consists of several islands that are the emergent parts of two parallel submarine ridges: the Norfolk Ridge to the SW and the Loyalty Ridge to the NE (Fig. 1.1). The total area of the country is 18 350 km2. Grande Terre, the largest and main island, is mountainous, c. 400 km long and c. 50 km wide. The highest points are Mont Panie (1628 m) in the north and Mont Humboldt (1618 m) in the south. Grande Terre is surrounded by a 1500 km long barrier reef complex, the second longest in the world, with parts listed as a UNESCO World Heritage site. By contrast, the Loyalty Islands have a low elevation (127 m maximum height on Mare). As well as Grand Terre and the Loyalty Islands, the New Caledonia archipelago includes the isolated and uninhabited Matthew and Hunter islands to the east and the sandy Chesterfield islets to the west. The New Caledonia Exclusive Economic Zone covers an area of 1 360 000 km2. Fig. 1.1. ( a ) New Caledonia in the SW Pacific. ( b ) New Caledonia archipelago. ( c ) Map of New Caledonia with 1:50 000 scale geological map series (grey rectangle) and index numbers. 1, Iles Belep; 2, Poum–Yande; 3, Paagoumene; 4, Pam-Ouegoa; 5, Pouebo; 6, Koumac, 7, Paimboas; 8, Hienghene; 9, Ouaco-Voh; 10, Goyeta-Pana; 11, 12, Touho-Poindimie; 13, Pouembout; 14, Paeoua; 15, Ponerihouen; 16, Baie Lebris; 17, Poya-Plaine des Gayacs; 18, Me Maoya; 19, Houailou; 20, Kouaoua; 21, Bourail; 22, Moindou; 23, Canala-La …

Chapter 2 Geodynamics of the SW Pacific: a brief review and relations with New Caledonian geology

Abstract The SW Pacific region consists of a succession of ridges and basins that were created by the fragmentation of Gondwana and the evolution of subduction zones since Mesozoic times. This complex geodynamic evolution shaped the geology of New Caledonia, which lies in the northern part of the Zealandia continent. Alternative tectonic models have been postulated. Most models agree that New Caledonia was situated on an active plate margin of eastern Gondwana during the Mesozoic. Extension affected the region from the Late Cretaceous to the Paleocene and models for this period vary in the location and nature of the plate boundary between the Pacific and Australian plates. Eocene regional tectonic contraction included the obduction of a mantle-derived Peridotite Nappe in New Caledonia. In one class of model, this contractional phase was controlled by an east-dipping subduction zone into which the Norfolk Ridge jammed, whereas and in a second class of model this phase corresponds to the initiation of the west-dipping Tonga–Kermadec subduction zone. Neogene tectonics of the region near New Caledonia was dominated by the eastwards retreat of Tonga–Kermadec subduction, leading to the opening of a back-arc basin east of New Caledonia, and the initiation and southwestwards advance of the New Hebrides–Vanuatu subduction zone towards New Caledonia.

A Reappraisal of the Poya Terrane (New Caledonia): Accreted Late Cretaceous‐Paleocene Marginal Basin Upper Crust, Passive Margin Sediments, and Early Eocene E‐MORB Sill Complex

AbstractThe Poya Terrane of New Caledonia is a composite lithotectonic unit made of (i) Campanian‐Paleocene enriched mid‐ocean ridge basalt (E‐MORB) and BABB‐type (back‐arc basin basalt) basalts and abyssal argillite (Poya Terrane basalts) and (ii) Coniacian‐Santonian sandstone, turbidites, and abyssal argillite (Kone Facies) intruded by early Eocene E‐MORB sills. Remapping reveals that the Kone Facies is more extensive than previously thought. Field data, petrography, and U‐Pb geochronology of detrital zircons show that Kone Facies sediments have the same provenance as coeval autochthonous sediments (Formation a Charbon), albeit with more abundant contemporaneous zircons. They accumulated on the eastern continental slope of the Norfolk Ridge and eventually mixed with abyssal argillite. Temporally, sill emplacement is related to subduction inception at circa 56 Ma, thus suggesting a possible genetic link. We postulate that either (i) E‐MORB intrusion was related to oblique extension and thinning of the down going plate or, alternatively, (ii) the “enriched” (off axis?) partial melt zone of the ancient ridge swept the lower plate continentward, generating E‐MORB dikes in the upper marginal basin crust, and sills in passive margin sediments before it became extinct. Thereafter, sliced marginal basin upper crust, passive margin sediments, and associated dolerite sills were obliquely accreted to the fore‐arc region, and in the NE part of the terrane, subducted and recrystallized into the blueschist facies. The Poya Terrane was eventually thrust onto the Norfolk Ridge when the latter reached the subduction zone and debris from the thrust sheet fed middle to late Eocene syntectonic basins. At the same time, mafic portions of the Poya Terrane were subducted at depth where they recrystallized into the eclogite facies, mixed with serpentinite to form the Pouebo mélange, and, finally, were exhumed in the fore‐arc region. Finally, late Oligocene faulting and hydrothermal events overprinted the NE part of the terrane in probable connection with postobduction granitoid emplacement.

The zircon record of high-pressure metasedimentary rocks of New Caledonia: Implications for regional tectonics of the south-west Pacific

We report the U-Pb age, and trace element and hafnium isotope composition of zircons recovered from clastic metasedimentary rocks that span a range of metamorphic grades (prehnite-pumpellyite to eclogite facies) across the high-pressure metamorphic belt of northern New Caledonia. We use these data to evaluate the sedimentary source and environment of formation of these rocks, as well as their respective metamorphic evolution.Metasediments from the low-grade Koumac and blueschist-facies Diahot sequences contain zircon with age populations of 1800–1500Ma, 700–500Ma, 300–250Ma and 140–80Ma. These grains have highly variable Hf isotope compositions (εHf −36 to +12), and some have thin metamorphic rim zones dated to ~38Ma. Zircon grains from the high-grade metamorphic section (Pouebo Eclogite Mélange) are mostly Upper Cretaceous and lowermost Eocene in age, with ~40Ma metamorphic overgrowth zones. The Upper Cretaceous zircons from across the belt have similar isotopic compositions, whereas the lowermost Eocene zircons have relatively high εHf of +6 to +13. The zircon record of the eclogites often lacks the diverse old detrital signature that is prevalent in the blueschist-facies rocks; rather the age populations of the eclogite grade zircons reflect derivation from nearby volcanic sources.We suggest that the bulk of Koumac and Diahot sequences represent the erosional products of the Norfolk Ridge that were transported eastwards and accumulated into the East New Caledonia Basin. Paleozoic and Precambrian zircon grains were originally sourced from Paleozoic orogenic belts of the eastern margin of Australia, and possibly from now-submerged ridges of continental character. We suggest that the Mesozoic zircon grains derived from volcanic arc activity on the eastern margin of Gondwana. Extension led to a reduced continental sediment input into the East New Caledonia Basin during the Cretaceous, which explains the limited amounts of ancient detritus in the mid-Cretaceous to Eocene sedimentary protoliths of the Pouebo Eclogite Mélange. The combined Hf isotope and age data for our zircon record point to the existence of a west-dipping subduction zone active throughout the Late Triassic to the Late Cretaceous, possibly with some short-lived periods of volcanic hiatus. In the early Eocene, a new east-dipping subduction formed following a major change in plate kinematics, producing younger metavolcanic zircons and eventually leading to the metamorphism of sedimentary units in the middle Eocene.

Studies on Southwest Pacific Hexactinellida 2: two new hexactinosid glass sponges from the Norfolk Ridge (New Caledonia EEZ)

Studies on Southwest Pacific Hexactinellida 2: two new hexactinosid glass sponges from the Norfolk Ridge (New Caledonia EEZ)

A new species of lithistid sponge hiding within the Isabella mirabilis speciescomplex (Porifera: Demospongiae: Tetractinellida) from seamounts of the Norfolk Ridge.

A population level study of the lithistid ('rock') sponge, Isabella mirabilis, revealed a new species, Isabella tanoa sp. nov., living on five seamounts on the Norfolk Ridge, SW Pacific, and representing the third species to be discovered since the genus was first described in 2005. Comparisons between the three species showed significant differences in morphological characters that corresponded to differences in their respective CO1 barcoding sequences. Conversely, three of the four genotypes of Isabella mirabilis remain unresolved using morphological markers.

New species of Venustatrochus Powell, 1951 from New Zealand, and new species of Falsimargarita Powell, 1951 and a new genus of the Calliostomatidae from the southwest Pacific, with comments on some other calliostomatid genera (Mollusca: Gastropoda)

ABSTRACTThree new species of Venustatrochus Powell, 1951, V. eclectus n. sp., V. galateae n. sp. and V. youngi n. sp. are described from New Zealand, and Calliostoma (Benthastelena) malaita Vilvens, 2009 from the Solomon Islands and Norfolk Ridge and C. atlantis Clench & Aguayo, 1940 from off Cuba are referred to the genus. The radula of the type species of Otukaia, O. kiheiziebisu (Otuka, 1939), is illustrated, and O. ikukoae Sakurai, 1994 is resurrected from synonymy under O. kiheiziebisu and transferred to Tristichotrochus Ikebe, 1942. Benthastelena Iredale, 1936, Fautor Iredale, 1924 and Maurea Oliver, 1926 are each assigned genus rank in Calliostomatinae, and Alertalex Dell, 1956 is treated as a subgenus of Maurea. The South American species Otukaia chilena (Rehder, 1971) and O. delli (McLean & Andrade, 1982), the western subantarctic species O. eltanini Dell, 1990 and Calliostoma muriellae Vilvens, 2001 from Madagascar are referred to Maurea. Otukaia crustulum Vilvens & Sellanes, 2006 is referred to Calliotropis L. Seguenza, 1903 (Calliotropidae). Six new species of Falsimargarita Powell, 1951 are described—F. callista n. sp., F. challengerica n. sp., F. eximia n. sp. and F. tangaroa n. sp., from New Zealand, F. kapala n. sp. from southeastern Australia, and F. coriolis n. sp. from New Caledonia. Calliostoma atlantoides Quinn, 1992 and C. coronatum Quinn, 1992 from off the Lesser Antilles and Brazil, respectively, are referred to Falsimargarita. Phenacomargarites n. gen. is introduced for P. williamsae n. sp. from the Solomon Islands, and P. incomptus n. sp. and P. titan n. sp. from the New Zealand region. Phenacomargarites, Falsimargarita, Selastele Marshall, 1995 and Fautrix Marshall, 1995 are referred to subfamily Fautricinae Marshall, 1995 (elevated from tribe level).http://zoobank.org/urn:lsid:zoobank.org:pub:09EAD861-3B62-42F9-BCC1-453EBE1347D4

Genus Profundiconus Kuroda, 1956 (Gastropoda, Conoidea): Morphological and molecular studies, with the description of five new species from the Solomon Islands and New Caledonia

The genus Profundiconus Kuroda, 1956 is reviewed. The morphological characters of the shell, radular tooth and internal anatomy of species in Profundiconus are discussed. In particular, we studied Profundiconus material collected by dredging in deep water during different scientific campaigns carried out in the Solomon Islands, Madagascar, Papua New Guinea and New Caledonia. We reconstructed a phylogeny of 55 individuals based on partial mitochondrial cox1 gene sequences. The phylogeny shows several clades containing individuals that do not match any of the known species of Profundiconus based on their shell and radular morphologies, and are introduced here as five new species: Profundiconus maribelae sp. nov. from the Solomon Islands; P. virginiae sp. nov. from Chesterfield Plateau (New Caledonia); P. barazeri sp. nov. from Chesterfield Plateau and the Grand Passage area (New Caledonia); P. puillandrei sp. nov. from Norfolk Ridge (New Caledonia), Kermadec Ridge (New Zealand) and possibly Balut Island (Philippines); and P. neocaledonicus sp. nov. from New Caledonia. Furthermore, Profundiconus teramachii forma neotorquatus (da Motta, 1984) is raised to specific status as P. neotorquatus (da Motta, 1984).