-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 60 million year period of widespread tectonic quiescence, thermal subsidence and marine transgression. 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 Zealand's 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 OligoceneEarly 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.

A 4.9 Mkm 2 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

U-Pb detrital zircon ages (LAM-ICPMS)

New mapping on the Chatham Islands, coupled with many new fossil determinations, has significantly refined our understanding of stratigraphic relationships of the Cretaceous-Cenozoic rocks exposed there. The following units are recognisable: Waihere Bay Group (emended), Tupuangi Formation (redefined; 240-400 m; Late Albian-Santonian), Pitt Island Group (emended), Kahuitara Tuff « 225 m; Campanian-Maastrichtian), Southern Volcanics (>300 m; Campanian-Maastrichtian), unnamed Cretaceous sandstone (>0.3 m; Late (?) Cretaceous), unnamed Haumurian limestone (fissure fills; Late Maastrichtian), Tioriori Group (emended), Takatika Grit (c. 6 m;

Sr 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.