We report new U-Pb zircon ages, geochemical and isotopic data for Mesozoic igneous rocks, and new seismic interpretations of mostly submerged South Zealandia (1.5 Mkm 2 ). We use these data, along with existing geological and geophysical data sets, to refine the extent and nature of geological units. Our new 1:25 M geological map of South Zealandia provides a regional framework to investigate the rifting and breakup that formed Zealandia, Earth's most submerged continent. Samples of prerift (pre-100 Ma) plutonic rocks can be matched with on-land New Zealand igneous suites and indicate an east-west strike for the subduction-related 260 to 105-Ma Median Batholith across the Campbell Plateau. The plutonic chronology of formerly contiguous plutonic rocks in West Antarctica reveals similar pulses and lulls to the Median Batholith. Contrary to previous interpretations, the Median Batholith does not coincide with the 1,600-km-long Campbell Magnetic Anomaly System. Instead we interpret the continental magnetic anomalies to represent a mainly mafic igneous unit, whose shape and extent is controlled by synrift structures related to Gondwana breakup. Correlatives of some of these unsampled igneous rocks may be exposed as circa 85 Ma alkalic volcanic rocks on the Chatham Islands. Extension directions varied by up to 65°from 100 to 80 Ma, and we suggest this allowed this large area to thin considerably before final rupture to form new oceanic crust. Synrift (90-80 Ma) structures cut the oroclinal bend in southern South Island and support a pre-early Late Cretaceous age of orocline formation.

We formally introduce 14 new high-level stratigraphic names to augment existing names and to hierarchically organise all of New Zealand's 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 country's 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.Keywords: igneous rocks; metamorphic rocks; New Zealand; Zealandia; sedimentary rocks; stratigraphy; tectonics Introduction It has been 40 years since Carter et al. (1974) proposed a tripartite high-level stratigraphic nomenclature for New Zealand rocks. Their Kaikoura, Rangitata and Tuhua sequences were broad, unconformity-bounded stratigraphic units, with the Rangitata Sequence being subdivided into formal assemblages and zones. Following revisions to the International Stratigraphic Guide, Carter (1988) amended the sequences to synthems.The high-level nomenclature of Carter et al. (1974) and Carter (1988) has not been widely adopted. The orogenies, assemblages, zones, sequences and synthems proposed for New Zealand's Cambrian-Early Cretaceous basement rocks were supplanted by a different, stable and well-used classification based on provinces, terranes and batholiths ( Fig. 1; e.g. Coombs et al. 1976;Tulloch 1988). Carter (1988 defined the Kaikoura Synthem to encompass Late Cretaceous-Holocene cover strata in eastern South Island which he divided into five formal groups onshore, four of which he correlated to informal seismic sequences offshore. While Carter's (1988) use of offshore seismic stratigraphy and his concepts for developing a 'lumping rather than splitting' approach were...

Volcanism of Late Cretaceous–Miocene age is more widespread across the Zealandia continent than previously recognized. New age and geochemical information from widely spaced northern Zealandia seafloor samples can be related to three volcanotectonic regimes: (1) age-progressive, hotspot-style, low-K, alkali-basalt-dominated volcanism in the Lord Howe Seamount Chain. The northern end of the chain (c. 28 Ma) is spatially and temporally linked to the 40–28 Ma South Rennell Trough spreading centre. (2) Subalkaline, intermediate to silicic, medium-K to shoshonitic lavas of >78–42 Ma age within and near to the New Caledonia Basin. These lavas indicate that the basin and the adjacent Fairway Ridge are underlain by continental rather than oceanic crust, and are a record of Late Cretaceous–Eocene intracontinental rifting or, in some cases, speculatively subduction. (3) Spatially scattered, non-hotspot, alkali basalts of 30–18 Ma age from Loyalty Ridge, Lord Howe Rise, Aotea Basin and Reinga Basin. These lavas are part of a more extensive suite of Zealandia-wide, 97–0 Ma intraplate volcanics. Ages of northern Zealandia alkali basalts confirm that a late Cenozoic pulse of intraplate volcanism erupted across both northern and southern Zealandia. Collectively, the three groups of volcanic rocks emphasize the important role of magmatism in the geology of northern Zealandia, both during and after Gondwana break-up. There is no compelling evidence in our dataset for Late Cretaceous–Paleocene subduction beneath northern Zealandia.

A new multidisciplinary project in southwest New Zealand that combines geological and geophysical data shows how and why deep lithospheric displacements were transferred vertically through the upper plate of an incipient ocean-continent subduction zone. A key discovery includes two zones of steep, downward-curving reverse faults that uplifted and imbricated large slices of Cretaceous lower, middle, and upper crust in the Late Miocene. Geochemical and structural analyses combined with 40 Ar/ 39 Ar geochronology and published images from seismic tomography suggest that the reverse faults formed at 8-7 Ma as a consequence of a deep (~100 km) collision between subducting oceanic lithosphere and previously subducted material. This collision localized shortening and reactivated two crustalscale shear zones from the upper mantle to Earth's surface. The event, which is summarized in a new lithosphericscale profile, is helping us answer some long-standing questions about the origin of Fiordland's unique lower-crustal exposures and what they tell us about how inherited structures can transfer motion vertically through the lithosphere as subduction initiates.

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