Hamish J. Campbell

The Waipounamu Erosion Surface: questioning the antiquity of the New Zealand land surface and terrestrial fauna and flora

The Waipounamu Erosion Surface is a time-transgressive, nearly planar, wave-cut surface. It is not a peneplain. Formation of the Waipounamu Erosion Surface began in Late Cretaceous time following break-up of Gondwanaland, and continued until earliest Miocene time, during a 60millionyearperiodofwidespreadtectonicquiescence,thermalsubsidenceandmarinetransgression. Sedimentary facies and geomorphological evidence suggest that the erosion surface may have eventually covered the New Zealand subcontinent (Zealandia). We can find no geological evidence to indicate that land areas were continuously present throughout the middle Cenozoic. Important implications of this conclusion are: (1) the New Zealand subcontinent was largely, or entirely, submerged and (2) New Zealands present terrestrial fauna and flora evolved largely from fortuitous arrivals during the past 22 million years. Thus the modern terrestrial biota may not be descended from archaic ancestors residing on Zealandia when it broke away from Gondwanaland in the Cretaceous, since the terrestrial biota would have been extinguished if this landmass was submerged in Oligocene- Early Miocene time. We conclude that there is insufficient geological basis for assuming that land was continuously present in the New Zealand region through Oligocene to Early Miocene time, and we therefore contemplate the alternative possibility, complete submergence of Zealandia.

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.

Age and isotopic characterisation of metasedimentary rocks from the Torlesse Supergroup and Waipapa Group in the central North Island, New Zealand

Abstract Detrital zircon U‐Pb ages in grey wackes and initial 87Sr/86Sr ratios are reported for low‐grade metasedimentary rocks from Torlesse Supergroup, Waipapa Group, and Kaimanawa Schist in the central North Island, New Zealand. The data reveal the presence of a hitherto unsuspected, areally extensive, Jurassic part of the Torlesse composite terrane in the Kaimanawa, Kaweka, and Ruahine Ranges, which we name the Kaweka Terrane. Kaweka rocks have initial 87Sr/86Sr ratios (at metamorphism) and detrital zircon patterns that in part are transitional between Rakaia and Pahau Terrane rocks and in part similar to Waipapa Terrane rocks. Combined detrital zircon age data for all Torlesse and Waipapa Terrane data reveal an essential unity, with a long persistence (260–120 Ma) of predominant Permian‐Triassic sources in the form of a major Cordilleran‐style batholith, a decline in major early Paleozoic‐Precambrian sources between 260 and 220 Ma, and presence of minor Early Carboniferous to Late Devonian sources between 180 and 120 Ma. Rb‐Sr and K‐Ar ages indicate latest Triassic to Early Cretaceous metamorphism in an evolving accretionary wedge.

High-level stratigraphic scheme for New Zealand rocks

We formally introduce 14 new high-level stratigraphic names to augment existing names and to hierarchically organise all of New Zealands onland and offshore Cambrian–Holocene rocks and unconsolidated deposits. The two highest-level units are Austral Superprovince (new) and Zealandia Megasequence (new). These encompass all stratigraphic units of the countrys Cambrian–Early Cretaceous basement rocks and Late Cretaceous–Holocene cover rocks and sediments, respectively. Most high-level constituents of the Austral Superprovince are in current and common usage: Eastern and Western Provinces consist of 12 tectonostratigraphic terranes, 10 igneous suites, 5 batholiths and Haast Schist. Ferrar, Tarpaulin and Jaquiery suites (new) have been added to existing plutonic suites to describe all known compositional variation in the Tuhua Intrusives. Zealandia Megasequence consists of five predominantly sedimentary, partly unconformity-bounded units and one igneous unit. Momotu and Haerenga supergroups (new) comprise lowermost rift to passive margin (terrestrial to marine transgressive) rock units. Waka Supergroup (new) includes rocks related to maximum marine flooding linked to passive margin culmination in the east and onset of new tectonic subsidence in the west. Māui and Pākihi supergroups (new) comprise marine to terrestrial regressive rock and sediment units deposited during Neogene plate convergence. Rūaumoko Volcanic Region (new) is introduced to include all igneous rocks of the Zealandia Megasequence and contains the geochemically differentiated Whakaari, Horomaka and Te Raupua supersuites (new). Our new scheme, Litho2014, provides a complete, high-level stratigraphic classification for the continental crust of the New Zealand region.

Zealandia: Earth’s Hidden Continent

A 4.9 Mkm2 region of the southwest Pacific Ocean is made up of continental crust. The region has elevated bathymetry relative to surrounding oceanic crust, diverse and silica-rich rocks, and relatively thick and low-velocity crustal structure. Its isolation from Australia and large area support its definition as a continent—Zealandia. Zealandia was formerly part of Gondwana. Today it is 94% submerged, mainly as a result of widespread Late Cretaceous crustal thinning preceding supercontinent breakup and consequent isostatic balance. The identification of Zealandia as a geological continent, rather than a collection of continental islands, fragments, and slices, more correctly represents the geology of this part of Earth. Zealandia provides a fresh context Nick Mortimer, GNS Science, Private Bag 1930, Dunedin 9054, New Zealand; Hamish J. Campbell, GNS Science, P.O. Box 30368, Lower Hutt 5040, New Zealand; Andy J. Tulloch, GNS Science, Private Bag 1930, Dunedin 9054, New Zealand; Peter R. King, Vaughan M. Stagpoole, Ray A. Wood, Mark S. Rattenbury, GNS Science, P.O. Box 30368, Lower Hutt 5040, New Zealand; Rupert Sutherland, SGEES, Victoria University of Wellington, P.O. Box 600, Wellington 6140, New Zealand; Chris J. Adams, GNS Science, Private Bag 1930, Dunedin 9054, New Zealand; Julien Collot, Service Géologique de Nouvelle Calédonie, B.P. 465, Nouméa 98845, New Caledonia; and Maria Seton, School of Geosciences, University of Sydney, NSW 2006, Australia in which to investigate processes of continental rifting, thinning, and breakup.

Geology of the Permian Kuriwao Group, Murihiku Terrane, Southland, New Zealand

Abstract Kuriwao Group rocks form a small inlier (5×2 km) of calcareous and volcaniclastic Permian rocks in Southland, surrounded by Triassic and Jurassic Murihiku Supergroup. Previously reported Kuriwao Group field relationships, macrofauna, leaf fossils, and palynoflora have been re‐examined and interpretations are made of these and new data. A Late Permian age for sandstones and limestones of the Kuriwao Group is confirmed and no evidence is found that the limestones are olistoliths. Field relationships and palynological data suggest that Early‐Middle Triassic Wairuna Peak Group (Murihiku Supergroup) strata lie in conformable sedimentary contact on the Kuriwao Group. The petrological composition of Kuriwao Group sandstones closely resembles quartz‐poor sandstones in overlying Wairuna Peak Group and differs from broadly coeval Permian sandstones in the Brook Street and Maitai Terranes. Kuriwao Group should be regarded as part of the Murihiku tectonostratigraphic terrane. With the age of Murihiku Terrane extending back into the Permian, some 120 m.y. of geological history are represented in an aggregate thickness of c. 16 km of little‐deformed strata, although not in any one section. Permian rocks are now known from seven New Zealand terranes.

Geology of the red rocks — turbidite association, Wellington peninsula, New Zealand

Abstract The Wellington peninsula is composed of Torlesse terrane greywacke turbidites with intercalations of red rocks that occur in various combinations of metabasalt, chert, and coloured (red, green, grey) argillite. The red rocks define 2 km-scale folds (the Rimurapa inverted syncline and Evans Bay Syncline) in the Wellington peninsula. The best known example of red rocks crops out at a point called Red Rocks on the coast about 8 km south of Wellington City. Radiolarians in cherts at Red Rocks indicate a Late Permian age, whereas radiolarians from phosphorite and a probable hydrozoan fossil (Heterastridium) in grey argillite of the turbidite sequence indicate a Late Triassic (Carnian-Norian) age. Radiolarians from phosphatic concretions in grey argillite interbedded with turbidites elsewhere in the Wellington peninsula also indicate a Late Triassic age. The fossil ages indicate a 40–50 Ma age difference between the red rocks and the enclosing turbidites. In addition to their older age, the red rocks: ...

Discovery of Early Cretaceous Rocks in New Caledonia: New Geochemical and U-Pb Zircon Age Constraints on the Transition from Subduction to Marginal Breakup in the Southwest Pacific

New U-Pb dating of detrital zircon and geochemical features of Permian-Mesozoic arc-derived volcanic rocks and volcaniclastic turbidites (graywackes), when compared with those of the volcanic rocks associated with unconformable Late Cretaceous shallow-water sediments, reveal that subduction in New Caledonia, once thought to be extinct in the Late Jurassic (ca. 150 Ma), was still active at least from ca. 130 to 95 Ma. The accumulation of volcanic arc-derived sediments during the late Early Cretaceous suggests that, as in New Zealand, active-margin activity went on for a short time in spite of the assumed subduction jamming by the Hikurangi Plateau at ca. 100 Ma. Meanwhile, the rift-related magmatic activity that preceded the marginal breakup migrated eastward from ca. 130 Ma (130–95 Ma) in eastern Australia, to 110 Ma (110–82 Ma) in New Zealand, and, finally, to ca. 89 Ma (89–83 Ma) in New Caledonia and generated large volumes of silicic magma. In contrast, marginal basins opened synchronously at ca. 83 Ma when the stretched continental crust finally broke out. In general, intraplate and volcanic arc signatures coexisted in Cretaceous syn-rift magmas. Therefore, the Australian marginal breakup appears to be the final effect of continuous southward unzipping of Gondwana that interfered with the subduction-modified mantle wedge of the Mesozoic active margin. The occurrence of lateral flow of the upper asthenospheric mantle due to the rapidly eastward-migrating Australian plate margin possibly prevented the formation of a volcanic arc at the eastern end of the system.

Paracomatula triadica sp. nov. — an early comatulid crinoid from the Otapirian (Late Triassic) of New Caledonia

Paracomatula triadica sp. nov. from the Late Triassic (Otapirian, upper Norian) Bourake Formation of New Caledonia is the earliest known feather star. Its primitive characters (short arms, branching only once isotomously, long cylindrical cirrals and tall brachials) suggest that the paracomatulids are a Late Triassic offshoot of the holocrinids rather than the more specialized pentacrinitids. The paracomatulids appear for the first time after the mid Carnian extinction. Their eleutherozoic life style was to become the most successful strategy among modern articulate crinoids. Paracomatula triadica sp. nov. aus der obertriadischen Bourake Formation (Otapirium, Obernor) von Neukaledonien ist der alteste bekannte Haarstern. Seine ursprunglichen Merkmale (kurze Arme mit einer einzigen, isotomen Teilung, lange zylindrische Zirren- und lange Armglieder) legen nahe, das die Paracomatuliden eher obertriadische Abkommlinge der Holocriniden als der hochspezialisierten Pentacrinitiden sind. Paracomatuliden erscheine...

Tracing the Caples Terrane through New Zealand using detrital zircon age patterns and radiogenic isotope signatures

Abstract Rb‐Sr isochron ages and associated initial 87Sr/86Sr ratios of metasedimentary rocks of Caples Group in Southland and Otago, Pelorus Group in Nelson and Marlborough, and their minor North Island correlates in Northland and King Country, reveal the essential continuity of a long Caples Terrane throughout New Zealand. The Rb‐Sr ages, in the range 251–117 Ma, record post‐metamorphic, Early Triassic to Early Cretaceous uplift and cooling, whilst their associated range of initial 87Sr/86Sr ratios, 0.7039–0.7053, allows a discrimination from analogous datasets of neighbouring Torlesse and Waipapa Terranes. Some petrographically and geochemically anomalous Caples Terrane rocks in East Otago, and Otago Schists of the Aspiring Terrane, all with initial 87Sr/86Sr ratios >0.7055, compare best with dataseis of Waipapa Terrane of the North Island. Detrital zircon U‐Pb ages of greywackes from Caples Terrane metasediments have youngest zircon age components from 251 to 215 Ma, and a comparison of dataset patterns from fossiliferous examples suggests that these probably originate from contemporary volcanic sources. Caples volcanism and associated depocentres thus span much of the Triassic. However, their major zircon component, invariably in the range Early Triassic to latest Permian, is most persistent, and constitutes an enormous and enduring zircon source thought to be in the New England Orogen of eastern Australia. Minor, late Paleozoic (295–340 Ma) zircon components are restricted to (Early‐Middle Triassic) Caples Terrane metasediments with older, minimum zircon age components, perhaps originating in nearby primary sources in the northeasternmost Lachlan Fold Belt and southern part of the New England Orogen. More scattered early Paleozoic‐Precambrian zircons are present throughout the Caples Terrane and reflect reworking of zircons from Paleozoic metasediments and plutonic rocks within the New England Orogen (and its immediate hinterland). Caples Terrane metasediments thus represent an offshore, Triassic component of the accretionary prism terranes (Late Carboniferous to Early Cretaceous) of the Eastern Province of New Zealand. Their depocentres were more isolated from the Gondwanaland continental m argin than Torlesse and Waipapa Terrane counterparts, and more influenced by substantial contemporary volcanic centres, perhaps located along the Lord Howe Rise.