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(A) Zealandia bathymetry (m), new (stars) and existing (circles) drill sites, New Caledonia Trough (NCT), Norfolk Ridge (NR), D'Entrecasteaux Ridge (DER), Reinga Basin (RB), and outline of Zealandia (dotted). B.-Basin. (B) Timing of events inferred from integrated analysis (see the Data Repository [see footnote 1]). Plio.-Pliocene; Pleist.-Pleistocene; DSDP-Deep Sea Drilling Project.

(A) Zealandia bathymetry (m), new (stars) and existing (circles) drill sites, New Caledonia Trough (NCT), Norfolk Ridge (NR), D'Entrecasteaux Ridge (DER), Reinga Basin (RB), and outline of Zealandia (dotted). B.-Basin. (B) Timing of events inferred from integrated analysis (see the Data Repository [see footnote 1]). Plio.-Pliocene; Pleist.-Pleistocene; DSDP-Deep Sea Drilling Project.

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Data from International Ocean Discovery Program (IODP) Expedition 371 reveal vertical movements of 1–3 km in northern Zealandia during early Cenozoic subduction initiation in the western Pacific Ocean. Lord Howe Rise rose from deep (~1 km) water to sea level and subsided back, with peak uplift at 50 Ma in the north and between 41 and 32 Ma in the s...

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... and 79 Ma, Zealandia separated from Gondwana ( Gaina et al., 1998;Sutherland, 1999), and much of the continent has been below sea level since, as documented by now-uplifted marine stratigraphic records in New Zealand and New Caledonia (Paris, 1981;Laird and Bradshaw, 2004) and submarine sections recovered by the Deep Sea Drilling Program (DSDP; Fig. 2; ...
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... northern Zealandia ( Bache et al., 2012;Browne et al., 2016). This has been coined the "Tectonic Event of the Cenozoic in the Tasman Area" (TECTA; Suther- land et al., 2017), and it appears to have begun about the same time as cessation of spreading in the Tasman Sea ( Gaina et al., 1998) and subduction initiation near or east of Norfolk Ridge ( Fig. 2; Gurnis et al., 2004;Cluzel et al., 2006;Sutherland et al., 2010;Bache et al., 2012;Mat- thews et al., ...
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... IODP Expedition 371, only three boreholes, DSDP Sites 206-208, each with limited core recovery, penetrated strata in northern Zealandia beneath the TECTA unconformity. We drilled six sites in the context of seismic reflection surveys ( Fig. 2; Figs. DR1 and DR2 in the GSA Data Repository 1 ). We classified paleodepth (meters below modern sea level [mbsl]) into the following categories (Van Morkhoven et al., 1986): neritic (<200 mbsl), upper bathyal (200-600 mbsl), middle bathyal (600-1000 mbsl), lower bathyal (1000-2000 mbsl), and abyssal (>2000 mbsl). We discovered ...
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... of northern Zealandia were transiently uplifted and then subsided. IODP Site U1506 on northern Lord Howe Rise rose close to sea level with a shallow carbonate platform at ca. 50 Ma, and subsided to a bathyal environment (∼600 mbsl) by 45 Ma. Neritic fossils of Eocene (ca. 50 Ma) age at Site U1506 are now ∼1770 mbsl. At DSDP Site 208 ( Fig. 2), middle Eocene (45-43 Ma) cores contain benthic foraminifers indicative of middle bathyal conditions, but planktic-benthic ratios in Paleocene (65-56 Ma) cores indicate shallower conditions, and unconformities separate Paleocene from older and younger strata ( ...
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... lower Miocene (23-19 Ma) chalk from lower Oligocene (33-32 Ma) ooze (Kennett et al., 1986). Fossils indicate a lower or middle bathyal environment since the late Eocene at Site 592, but lower Oligocene strata contain layers of coarse (1-4 cm) mollusk (Ostrea) fragments (Kennett et al., 1986), consistent with nearby shallow water. DSDP Site 207 ( Fig. 2) subsided from upper bathyal to middle bathyal depths during the Paleocene to middle Eocene, but an unconformity separates Eocene (43-38 Ma) from middle Miocene (15-13 Ma) strata, and inclusion of slumped upper Eocene (38-36 Ma) material along the unconformity is consistent with peak regional uplift in the latest Eocene and early ...
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... limestone dredged from ∼1750 mbsl in southwest Reinga Basin (Fig. 2) [mbsf]) indicate lower bathyal depths at 41 Ma ( Sutherland et al., 2019). Sedimentation rates increase downhole from 10 m/m.y. to 40 m/m.y. (Fig. DR2), and extrapolation to the base of the unit, determined from seismic reflection data to be ∼1300 mbsf, indicates a Paleogene age for the ...
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... limestone dredged from ∼1750 mbsl in southwest Reinga Basin (Fig. 2) [mbsf]) indicate lower bathyal depths at 41 Ma ( Sutherland et al., 2019). Sedimentation rates increase downhole from 10 m/m.y. to 40 m/m.y. (Fig. DR2), and extrapolation to the base of the unit, determined from seismic reflection data to be ∼1300 mbsf, indicates a Paleogene age for the ...
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... during the Paleogene. Lord Howe Rise uplifted by at least 1 km, with a southeast migration in this motion from 50 to 35 Ma. New Caledonia Trough subsided 1-3 km, starting at ca. 55-45 Ma, with no resolvable difference in timing between north and south. The East Reinga Basin records deformation at ca. 39 Ma with peak uplift at ca. 26-23 Ma ( Fig. 2; details of fossil evidence are given in the "Paleogeography" section of the Data ...
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... and volcanic activity associated with IBM subduction started at 53-52 Ma (Ar- culus et al., 2015), and the onset of metamorphism in New Caledonia was at 55-50 Ma (Pi- rard and Spandler, 2017;Vitale-Brovarone et al., 2018; Fig. 2; see the Data Repository). In the Tonga forearc, the oldest plagiogranites have ages ca. 51-50 Ma, and arc activity is evident after ca. 48 Ma ( Meffre et al., 2012). Seafloor spreading in the Tasman Sea also ended at ca. 52 Ma ( Gaina et al., 1998). The Emperor-Hawaii bend records onset of Pacific plate-motion change at ca. 50 Ma, ...
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... and 79 Ma, Zealandia separated from Gondwana ( Gaina et al., 1998;Sutherland, 1999), and much of the continent has been below sea level since, as documented by now-uplifted marine stratigraphic records in New Zealand and New Caledonia (Paris, 1981;Laird and Bradshaw, 2004) and submarine sections recovered by the Deep Sea Drilling Program (DSDP; Fig. 2; ...
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... northern Zealandia ( Bache et al., 2012;Browne et al., 2016). This has been coined the "Tectonic Event of the Cenozoic in the Tasman Area" (TECTA; Suther- land et al., 2017), and it appears to have begun about the same time as cessation of spreading in the Tasman Sea ( Gaina et al., 1998) and subduction initiation near or east of Norfolk Ridge ( Fig. 2; Gurnis et al., 2004;Cluzel et al., 2006;Sutherland et al., 2010;Bache et al., 2012;Mat- thews et al., ...
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... IODP Expedition 371, only three boreholes, DSDP Sites 206-208, each with limited core recovery, penetrated strata in northern Zealandia beneath the TECTA unconformity. We drilled six sites in the context of seismic reflection surveys ( Fig. 2; Figs. DR1 and DR2 in the GSA Data Repository 1 ). We classified paleodepth (meters below modern sea level [mbsl]) into the following categories (Van Morkhoven et al., 1986): neritic (<200 mbsl), upper bathyal (200-600 mbsl), middle bathyal (600-1000 mbsl), lower bathyal (1000-2000 mbsl), and abyssal (>2000 mbsl). We discovered ...
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... of northern Zealandia were transiently uplifted and then subsided. IODP Site U1506 on northern Lord Howe Rise rose close to sea level with a shallow carbonate platform at ca. 50 Ma, and subsided to a bathyal environment (∼600 mbsl) by 45 Ma. Neritic fossils of Eocene (ca. 50 Ma) age at Site U1506 are now ∼1770 mbsl. At DSDP Site 208 ( Fig. 2), middle Eocene (45-43 Ma) cores contain benthic foraminifers indicative of middle bathyal conditions, but planktic-benthic ratios in Paleocene (65-56 Ma) cores indicate shallower conditions, and unconformities separate Paleocene from older and younger strata ( ...
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... lower Miocene (23-19 Ma) chalk from lower Oligocene (33-32 Ma) ooze (Kennett et al., 1986). Fossils indicate a lower or middle bathyal environment since the late Eocene at Site 592, but lower Oligocene strata contain layers of coarse (1-4 cm) mollusk (Ostrea) fragments (Kennett et al., 1986), consistent with nearby shallow water. DSDP Site 207 ( Fig. 2) subsided from upper bathyal to middle bathyal depths during the Paleocene to middle Eocene, but an unconformity separates Eocene (43-38 Ma) from middle Miocene (15-13 Ma) strata, and inclusion of slumped upper Eocene (38-36 Ma) material along the unconformity is consistent with peak regional uplift in the latest Eocene and early ...
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... limestone dredged from ∼1750 mbsl in southwest Reinga Basin (Fig. 2) [mbsf]) indicate lower bathyal depths at 41 Ma ( Sutherland et al., 2019). Sedimentation rates increase downhole from 10 m/m.y. to 40 m/m.y. (Fig. DR2), and extrapolation to the base of the unit, determined from seismic reflection data to be ∼1300 mbsf, indicates a Paleogene age for the ...
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... limestone dredged from ∼1750 mbsl in southwest Reinga Basin (Fig. 2) [mbsf]) indicate lower bathyal depths at 41 Ma ( Sutherland et al., 2019). Sedimentation rates increase downhole from 10 m/m.y. to 40 m/m.y. (Fig. DR2), and extrapolation to the base of the unit, determined from seismic reflection data to be ∼1300 mbsf, indicates a Paleogene age for the ...
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... during the Paleogene. Lord Howe Rise uplifted by at least 1 km, with a southeast migration in this motion from 50 to 35 Ma. New Caledonia Trough subsided 1-3 km, starting at ca. 55-45 Ma, with no resolvable difference in timing between north and south. The East Reinga Basin records deformation at ca. 39 Ma with peak uplift at ca. 26-23 Ma ( Fig. 2; details of fossil evidence are given in the "Paleogeography" section of the Data ...
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... and volcanic activity associated with IBM subduction started at 53-52 Ma (Ar- culus et al., 2015), and the onset of metamorphism in New Caledonia was at 55-50 Ma (Pi- rard and Spandler, 2017;Vitale-Brovarone et al., 2018; Fig. 2; see the Data Repository). In the Tonga forearc, the oldest plagiogranites have ages ca. 51-50 Ma, and arc activity is evident after ca. 48 Ma ( Meffre et al., 2012). Seafloor spreading in the Tasman Sea also ended at ca. 52 Ma ( Gaina et al., 1998). The Emperor-Hawaii bend records onset of Pacific plate-motion change at ca. 50 Ma, ...

Citations

... Zealandia, the now largely submerged continental fragment of which the New Zealand archipelago forms part (Mortimer et al. 2017), began separating from Gondwana 83-79 Ma with the opening up of the Tasman Sea. By 55 Ma sea floor spreading had ceased and the New Zealand archipelago was, and remains, surrounded by oceanic gaps of at least 1500 km separation from neighbouring continents (Sutherland et al. 2020). Intermittent island arc and marine ridge connections to the north have persisted down to the present. ...
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We present data on sexual systems and associated traits in the New Zealand angiosperm flora and discuss reasons for the anomalously high levels of gender dimorphism in the flora, and the low levels of monoecy in woody species. Along with Hawai'i and New Caledonia, New Zealand has exceptionally high levels of gender dimorphism (19.5% of angiosperm species). The plant traits associated with gender dimorphism (woody growth, small, unspecialised white to yellow-green flowers, abiotic pollination, fleshy fruit) are the same as those in other regions and most gender dimorphic species belong to lineages that were already gender dimorphic on arrival in New Zealand. We attribute the high levels of gender dimorphism to several distinct factors. New Zealand’s evergreen forests have many small trees and understorey shrubs with fleshy fruit and small, open, inconspicuous flowers, a combination characterised by high levels of gender dimorphism elsewhere. Many of these species belong to lineages that migrated from the tropical north, a region with high levels of gender dimorphism. In comparison with many other regions, the New Zealand angiosperm flora has few annuals, and few plants with large, specialised flowers or pollinated by birds, traits elsewhere associated with exceedingly low levels of gender dimorphism. Finally, chance may have played a role through the association of gender dimorphism with rapidly radiating lineages. While the New Zealand angiosperm flora has similar levels of monoecy (14.2%) to other comparable regions, monoecy is exceptionally uncommon in the tree flora (3.4% for strictly monoecious species). However, the endemic Nothofagaceae and introduced woody monoecious species thrive in New Zealand. We suggest it is the lack of temperate sources for monoecious tree species, combined with the difficulty large-fruited monoecious tropical species have in crossing ocean gaps that may be ultimate reason for their failure to establish in greater numbers.
... The reorganization of Pacific Plate motion at ≈50 Ma inferred from the Hawaiian-Emperor seamount Bend (HEB), and global plate circuits (Muller et al. 2016;Torsvik et al. 2017), serves as an example of changing plate kinematics that could be influenced by subduction initiation. The initiation of subduction zones in the western and southwest Pacific at around 50 Ma, including Izu-Bonin-Mariana (Reagan et al. 2019) and Tonga-Kermadec (Sutherland et al. 2020), is the potential cause for the rearrangement of Pacific Plate motion. The hypothesis that IBM initiation causes a change in Pacific Plate motion is widely discussed and is based on the view that IBM initiated spontaneously (Stern & Bloomer 1992;Reagan et al. 2019). ...
Article
The initiation and development of subduction zones are associated with substantial stress changes both within plates and at plate boundaries. We formulate a simple analytical model based on the force balance equation of a subduction zone, and validate it with numerical calculations of highly non-linear, coupled thermomechanical system. With two kinds of boundary conditions with either fixed velocity or fixed force in the far-field, we quantitatively analyse the role of each component in the force balance equation, including slab pull, interplate friction, plate bending and basal traction, on the kinematics and stress state of a subducting plate. Based on the numerical and analytical models, we discuss the evolution of plate curvature, the role of plastic yielding and elasticity, and how different factors affect the timing of subduction initiation. We demonstrate with the presence of plastic yielding for a plate of thickness, H, that the bending force is proportional to H2, instead of H3 as previously thought. Although elasticity increases the force required to start nucleating subduction it does not substantially change the total work required to initiate a subduction zone when the yielding stress is small. The analytical model provides an excellent fit to the total work and time to initiate subduction and the force and velocity as a function of convergence and time. Plate convergence and weakening rate during nucleation are the dominant factors influencing the force balance of the plate, and 200 km of plate convergence is typically required to bring a nascent subduction zone into a self-sustaining state. The closed-form solution now provides a framework to better interpret even more complex, time-dependent systems in three dimensions.
... Fourth, the south Pacific contains large expanses of submerged continental area (e.g., Sutherland et al. (2020)). These regions have likely undergone significant horizontal extension at some time in their history. ...
... The change in direction of spreading of the Pacific plate relative to the Vancouver and Farallon plates began at 51.8 Ma (and was completed at 45.7 Ma) (Figure 7) (Barckhausen et al., 2013;Menard & Atwater, 1968). Evidence documenting early New Caledonia trough formation and subsidence between 55 and 45 Ma combined with radiometric dates from the Tonga forearc showing arc activity starting between 52 and 48 Ma suggest the formation of a collisional margin between the Pacific and Australian plates (Meffre et al., 2012;Sutherland et al., 2020). Uplift of New Caledonia and New Zealand doesn't occur until 46-44 Ma (Dallanave et al., 2020), however, and plate motion changes between Australia and Antarctica do not occur until ≈43 Ma, during anomaly C20 (Whittaker et al., 2007). ...
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The motion of the Pacific plate relative to Pacific hotspots produces age‐progressive chains of volcanoes. Methods of analysis of volcano locations and age dates using a small number of adjustable parameters (10 per chain) are presented. Simple fits to age progressions along Pacific hotspot chains indicate 1σ dispersions of age dates of ≈±1.0–±3.0 Ma. Motion between the Hawaii and Louisville hotspots differs insignificantly from zero with rates of 2 ± 4 mm/a (=±2σ) for 0–48 Ma and 26 ± 34 mm/a (=±2σ) for 48–80 Ma. Relative to a mean Pacific hotspot reference frame, motions of the Hawaii, Louisville, and Rurutu hotspots are also insignificant. Therefore plumes underlying these Pacific hotspots may be more stable in a convecting mantle than previously inferred. We find no significant difference in age between the Eocene bends of the Pacific hotspot chains. The best‐fitting assumed‐coeval age for the bends is 47.4 ± 1.0 Ma (=±2σ), coincident with the initiation of the doubling of the spreading rate of the Pacific plate relative to the Farallon and Vancouver plates. The initiation of the Eocene collision of India with Eurasia preceded the formation of the bends and was completed after their formation. Initiation of subduction of the Pacific plate in the west and southwest Pacific Ocean Basin likely preceded the formation of the bends, consistent with subduction initiation changing the torque on the Pacific plate such that it started moving in a more westward direction thus creating the Hawaiian‐Emperor Bend.
... Zealandia is a continent that rifted from Australia and Antarctica during the Cretaceous and has subsequently been modified by Australia-Pacific plate boundary deformation since the Eocene (Mortimer et al. 2017;Sutherland et al. 2020). Magnetic anomalies in the Tasman Sea show that a spreading ridge separated northern Zealandia from Australia during the interval 83-53 Ma (Gaina et al. 1998;Sutherland 1999). ...
... Burns et al. 1973;King 2000). However, geophysical surveys leading up to Expedition 371, along with subsequent drilling results, have revealed a complex series of tectonic and physiographic Eocene-Oligocene events that modified northern Zealandia Sutherland et al. 2020). It is, therefore, not possible to look at the modern physiography and assume that it was similar (but just shallower) in the latest Cretaceous and Paleocene. ...
... Seismic interpretation reveals significant deformation of West Norfolk, Wanganella, and Reinga Ridges (Figure 1) after the Paleocene, which indicates these physiographic ridges did not exist in their current form in the latest Cretaceous or Paleocene (Bache et al. 2012;Orr et al. 2020). In addition, benthic foraminiferal assemblages from Site U1509 and seismic-reflection interpretations suggest Aotea Basin started to rapidly subside in the early to middle Eocene (>2 km total subsidence since the Paleocene) (Sutherland et al. 2010b;Baur et al. 2014;Sutherland et al. 2020). The New Caledonia ridge-trough morphology, which has c. 3 km of relief today, was much more subdued in the latest Cretaceous and Paleocene. ...
Article
IODP Site U1509 (Expedition 371), New Caledonia Trough, provides a rare latest Cretaceous–Paleocene record from offshore northern Zealandia. We present new palynomorph and benthic foraminiferal assemblage data that show a transition from a latest Cretaceous vegetated sediment source region to a fully oceanic environment in the Paleocene. Latest Cretaceous (c. 68–66 Ma) non-calcareous claystone was deposited in upper bathyal paleodepths, with abundant plant microfossils that were likely transported in a northwest direction through the Aotea Basin region. A 2–3 Myr unconformity is identified at the Cretaceous/Paleogene boundary. Middle early–late Paleocene (c. 63.5–56 Ma) calcareous claystone shows evidence of deepening, deposited in middle bathyal or deeper paleodepths, and terrestrial input is minor. This latest Cretaceous to Paleocene deepening trend is consistent with inferred evolution of the Aotea and Northland basins further to the east, and other sparse northern Zealandia records, which show a common pattern of post-rift transgression consistent with long-term subsidence. Site U1509 allows for biogeographic extension and modification of the New Zealand Paleocene dinoflagellate zonation, description of a new dinoflagellate and pollen species, better inference of regional paleogeography, and may provide insights into the onset of western Pacific subduction initiation.
... The presence of rare small intraclasts (dropstones) from both a mafic volcanic source and older (Lachlan Orogen) metamorphic source areas suggests that both regions contributed detritus and may therefore represent either storm-redeposited distal shelf turbidite or more proximal tempestite beds derived from the west or southwest, with the inclusion of volcanic material, including reworked tuffs from the flanks of island volcanoes to the south or southeast. Older material may also be sourced from the Currorong Orogen to the southeast, or further afield such as Zealandia (Adams et al., 2021;Sutherland et al., 2020). The abundant bioturbation (Cruizana ichnofacies) and carbonaceous material within both siltstone and sandstone beds suggests marine shelf sedimentation with an abundant supply of organic material provided into the ecosystem. ...
Article
A mid-Permian (late Kungurian) micro-dolerite dyke/sill complex located at Kinghorn Point intruded into the then unconsolidated upper Wandrawandian Siltstone of the lower Shoalhaven Group, southeastern Sydney Basin. The dark grey siltstone was deposited in the deeper part of a coastal seaway characterised by northward-directed paleocurrents, with a Cruziana ichnofacies, crinoid stem fossils and abundant glendonites indicating a cold climate. Thin periodic storm deposits, or tempestites, of fine-grained sandstone of volcanogenic origin are scattered through the siltstone. These paler sandy beds were probably derived from island volcanoes to the south or southeast, indicating that regional volcanism was pervasive during this glacial episode. Evidence for penecontemporaneous igneous emplacement into mid-Permian wet unconsolidated shallow marine sediments includes: destruction of primary sedimentary structures caused by extensive interaction and intermingling between the sedimentary and igneous materials, the presence of brecciated contacts and peperite, angular and rounded dolerite fragments in the siltstone, fluidisation and entrainment of the sediments into cooling and flow fractures in the magma, and the presence of tube-like flow features. There are also hyaloclastite and baked sediments along the contact margins, fumaroles and vesicles within both the sediment and magma. High vesiculation is characteristic of intrusion near the surface, and possibly extrusion at the sediment–water interface. The geochemistry of the intrusion, especially key element ratios of the high-field-strength, major and trace elements, is very different from that of the shoshonites of the nearby Permian (mid Wordian to Capitanian) Gerringong Volcanics, having much lower Zr/TiO2, Nb/Y, Nb/Zr, K2O, P2O5, Rb, Th, U, Y, Zr and Nb, and higher MgO, suggesting they are unrelated. This indicates that the Kinghorn Point intrusion was associated with an earlier intermediate pre-Gerringong Volcanics phase, or it may be distinctive and unrelated. Magmatic geochemical comparisons further afield along the northern Sydney Basin and Tamworth Fold Belt boundary coasts show that volcanism was pervasive during the Wandrawandian glacial episode and that regional mid-Permian mafic volcanism was well evolved in the southern Sydney Basin during sedimentation. • KEY POINTS • A mid-Permian syndepositional dolerite intrusion at Kinghorn Point shows classical peperite and soft-sediment deformation features. • Previously unreported mafic tuffaceous sandstone beds within the Wandrawandian Siltstone were probably derived from island volcanoes to the south or southeast. • Geochemistry of the intrusion shows that it is not related to the mid Wordian to Capitanian Gerringong Volcanics. • Regional volcanism was pervasive during the Wandrawandian glacial episode along the southeast Panthalassan margin of Gondwana.
... Moreover, in contrast to the IBM trench, IODP Expedition 371 reveals that the Lord Howe Rise, northern Zealandia, was uplifted from depths of ~1 km underwater to above sea level and subsided back later on, which was attributed to crustal delamination and mantle fl ow that led to slab formation and subduction initiation (Sutherland et al., 2020). ...
... In contrast, the Zealandian subduction zone is associated with a young oceanic plate. Major uplift has been observed (Sutherland et al., 2020). ...
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Compression is required for all kinds of subduction initiations, which may cause either subsidence or uplift, depending on the ages of the oceanic plates. Subduction initiations associated with the old oceanic crust tend to amplify preexisting subsidence by compression, whereas those associated with young oceanic plates may result in uplift.
... It contains approximately 4 km of Cretaceous to Cenozoic sediments that follow a NE-SW trend, approximating the strike of the paleo margin (Figures 1 and 2). Before the breakup of Gondwana, the Australian margin was a convergent plate boundary with the westward subduction of the Phoenix plate, forming an extensive trench system [32][33][34]. Extensional tectonics created the early basin architecture through rapidly subsiding half grabens [35,36]. ...
Article
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Modern marine seismic reflection data have allowed for the study of the morphology of submarine channels in a 3D perspective. This study presents a quantitative analysis of continental slope channel complexes morphology within the Canterbury Basin (New Zealand). It aims to characterize the morphology and seismic facies of submarine channels to better understand their formative sedimentary processes, paleoenvironment, and petroleum prospectivity. Submarine channel morphometric parameters are measured at 150 m intervals perpendicular to the axis of channels complexes. Based on the morphology analysis of erosional surfaces and seismic facies of channel complexes filling deposits, four types of continental slope channel complexes are found in the study area. These are vertical migrating channels, lateral migrating channels, V-shaped channels, and U-shaped channels. Furthermore, our work shows that channel morphometry varies over distances of 0.1 to 14 km in this continental slope system. These changes indicate a combination of submarine gravity flow process and channel wall collapse responsible for the development of continental slope channel complexes. Regionally, the evolution of the channels indicated less significant regional plate movement. This quantitative seismic geomorphology approach of characterizing submarine channels system has broader applications for better interpretation of paleoenvironment and petroleum prospectivity within frontier basins.
... In New Zealand, there are no species on the Chatham Islands or in the Subantarctic region. Although our geographic sampling of Geochus is incomplete, the phylogenetic placement of the Lord Howe species within a group of species indicates a more complex geographic history either involving a potential dispersal to Lord Howe Island or being a result of complex restructuring that led to terranes being lost through Paleogene subduction (Sutherland et al. 2020). The Three Kings Islands in the north of New Zealand have species with ancient connections to New Caledonia and elsewhere, have taxa shared with Pacific clades, or have ancestors present on mainland New Zealand that have dated from the Miocene or later (Buckley and Leschen 2013). ...
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The enigmatic Australo-Pacific genus Geochus Broun includes 26 described species from New Zealand and one from Lord Howe Island. They are abundant in leaf litter, and most species are easily recognized as adults by their odd squat form, lack of tarsal claws and flattened larvae that mine dead leaves. In older classifications, Geochus was placed in Curculioninae or Molytinae, but has been regarded more recently as an aberrant molytine or member of Phrynixini. A phylogeny of weevils that included Geochus from New Zealand and Lord Howe Island, representatives of 32% of the weevil genera in New Zealand, selected Rhamphini and Viticiini, and the South African genus Afrogeochus Rheinheimer, placed Geochus as the sister taxon of Viticis Lea, well outside Molytinae or Curculioninae at the base of a grade consisting of Entiminae, Cyclominae, and Phrynixini. Afrogeochus is transferred from Curculioninae to Cossoninae, based on molecular evidence. The absence of tarsal claws has hitherto been a distinct character of Geochus. However, their retention is reported in Geochus kuscheli Leschen, Davis, Brown, Brav-Cubitt, and Buckley, new species, a species that is sister to the remaining members of the genus. The status of type specimens for all 26 previously described Geochus species is reviewed, and eleven lectotype designations are made to promote a stable taxonomy for: Geochus apicalis Broun, Geochus convexus Broun, Geochus inaequalis (Broun), Geochus lateralis Broun, Geochus marginatus Broun, Geochus pictulus Broun, Geochus plagiatus Broun, Geochus politus (Broun), Geochus puncticollis Broun, Geochus rugulosus Broun, Geochus setiger Broun, Geochus similis Broun, Geochus squamosus Broun, Geochus suffusus Broun, Geochus tibialis Broun, and Geochus variegatus Broun. The 27 known Geochus species are grouped into 13 species groups, and a key to the adults of these species groups is provided.
... Almost all previous models did not consider the rotation of the Pacific Plate. Therefore, it was proposed that the ridge between the Pacific and the Izanagi plates was roughly parallel to the current subduction zone as recorded by the Japanese Lineation (Fig. 4) and was subducted parallelly to the trench at~51 Ma (Seton et al., 2012), which is roughly the time of the Cenozoic subduction initiation in the West Pacific (Li et al., 2021;Maunder et al., 2020;Sun et al., 2020a, b;Sutherland et al., 2020;Reagan et al., 2019;O՚Connor et al., 2015). This geodynamic mechanism is very difficult. ...
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The eruption of large igneous provinces usually has major geodynamic influences on overriding plates. Seamount chains indicate that the drifting direction of the Pacific Plate changed by ∼80° in the Early Cretaceous when the Ontong Java Plateau formed. This, however, is not fully consistent with the magnetic anomalies. Here we show that there is an angle of ∼25° between the magnetic anomaly lines M0 and 34 of both the Japanese and the Hawaiian lineations, suggesting that the orientations of both spreading ridges changed by roughly the same angle towards the same direction. The configurations of the Shatsky Rise, the Papanin Ridge and the Osbourn Trough suggest that the eruption of the Ontong Java plume head uplifted the southeastern corner of the Pacific Plate, and pushed its east part northward by ∼700 km within 2 Ma. Meanwhile, the west part of the Pacific Plate was subducting southwestward underneath the eastern Asian Continent. These two forces together rotated the Pacific Plate anticlockwisely by ca 50°. Consequently, the drifting direction of the Pacific Plate also changed from southwestward to northwestward, which plausibly explains the ca 80° bending of the Shatsky Rise and the Papanin Ridge. The ridge between the Pacific and the Izanagi/Kula plates was pointed towards the ∼300° orientation, whereas the Pacific Plate was subducting towards the ∼250° orientation before ∼125 Ma, and towards ∼280° afterward.
... The hydrogenetic accumulation of Mn oxides and Fe-oxyhydroxides requires stable conditions over long periods of time (million years) to form thick crusts [5]. Their distribution, textures and composition are impacted by several parameters, such as surface bioproductivity, depth of the and is marked by the end of oceanic seafloor spreading in the Tasman Sea and the development of a regional event known as TECTA (Tectonic Event of the Cenozoic in the Tasman Area) lasting until the Oligocene [43][44][45]. It is characterised by contractional deformation, basin formation and volcanism. ...
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Located in the South-West Pacific, at the northern extremity of the mostly submerged Zealandia continent, the New Caledonian Exclusive Economic Zone (EEZ) covers 1,470,000 km² and includes basins, ridges and seamounts where abundant ferromanganese crusts have been observed. Several investigations have been conducted since the 1970s on the nature and composition of ferromanganese crusts from New Caledonia’s seamounts and ridges, but none have covered the entire EEZ. We present data from 104 ferromanganese crusts collected in New Caledonia’s EEZ during twelve oceanographic cruises between 1974 and 2019. Samples were analysed for mineralogy, geochemical compositions, growth rates, and through a statistical approach using correlation coefficients and factor analysis. Crust thicknesses range from 1 mm to 115 mm, with growth rates between 0.45 mm/Ma and 102 mm/Ma. Based on textures, structures, discrimination plots, and growth rates, we distinguish a group of hydrogenetic crusts containing the highest mean contents of Co (0.42 wt%), Ni (0.31 wt%), and high contents of Mo, V, W, Pb, Zn, Nb, from a group of hydrothermal and/or diagenetic deposits showing high mean contents of Mn (38.17 wt%), Ba (0.56 wt%) and low contents of other trace metals. Several samples from this later group have exceptionally high content of Ni (0.7 wt%). The data shows that crusts from the southern part of the EEZ, notably seamounts of the Loyalty Ridge and the Lord Howe Rise, present high mineral potential for prospectivity owing to high contents of valuable metals, and constitute a great target for further investigation.