In this paper we summarize and reassess a variety of geoscience data sets and show that a substantial part of the southwest Pacific Ocean consists of a continuous expanse of continental crust. NC-New Caledonia WTP-West Torres Plateau CT-Cato Trough Cf-Chesterfield Islands L-Lord Howe Island N-Norfolk Island K-Kermadec Islands Ch-Chatham Islands B-Bounty Islands An-Antipodes Islands Au-Auckland Islands Ca-Campbell Island. Continental basement samples from Suggate et al. Base map from Stagpoole (2002) based on data from Smith and Sandwell (1997). Implicit in Luyendyk’s paper was that this was a large region of continental crust, although this was only mentioned in passing and he did not characterize and define Zealandia as we do here. ![]() The name Zealandia was first proposed by Luyendyk (1995) as a collective name for New Zealand, the Chatham Rise, Campbell Plateau, and Lord Howe Rise (Fig. “New Zealand” was listed as a continent by Cogley (1984), but he noted that its continental limits were very sparsely mapped. The progressive accumulation of bathymetric, geological, and geophysical data since the nineteenth century has led many authors to apply the adjective continental to New Zealand and some of its nearby submarine plateaus and rises (e.g., Hector, 1895 Hayes, 1935 Thomson and Evison, 1962 Shor et al., 1971 Suggate et al., 1978). Perhaps this is because it is assumed that the names of the six geological continents-Eurasia, Africa, North America, South America, Antarctica, and Australia-suffice to describe all major regions of continental crust. To our knowledge, the last point-how “major” a piece of continental crust has to be to be called a continent-is almost never discussed, Cogley (1984) being an exception. The first three points are defining elements of continental crust and are explained in many geoscience textbooks and reviews (e.g., Holmes, 1965 Christensen and Mooney, 1995 Levander et al., 2005 Kearey et al., 2009 Condie, 2015). It is generally agreed that continents have all the following attributes: (1) high elevation relative to regions floored by oceanic crust (2) a broad range of siliceous igneous, metamorphic, and sedimentary rocks (3) thicker crust and lower seismic velocity structure than oceanic crustal regions and (4) well-defined limits around a large enough area to be considered a continent rather than a microcontinent or continental fragment. The Glossary of Geology defines a continent as “one of the Earth’s major land masses, including both dry land and continental shelves” (Neuendorf et al., 2005). Selected microcontinents and continental fragments shown by black dotted lines: Md-Madagascar Mt-Mauritia D-Gulden Draak T-East Tasman G-Gilbert B-Bollons O-South Orkney. Large igneous province (LIP) submarine plateaus shown by blue dashed lines: AP-Agulhas Plateau KP-Kerguelen Plateau OJP-Ontong Java Plateau MP-Manihiki Plateau HP-Hikurangi Plateau. Continental shelf areas shown in pale colors. Simplified map of Earth’s tectonic plates and continents, including Zealandia. 1)? Continents are Earth’s largest surficial solid objects, and it seems unlikely that a new one could ever be proposed. But what about the major continents (Fig. Simultaneously, there have been advances in our understanding of continental rifting, continent-ocean boundaries (COBs), and the discovery of a number of micro-continental fragments that were stranded in the ocean basins during supercontinent breakups (e.g., Buck, 1991 Lister et al., 1991 Gaina et al., 2003 Franke, 2013 Eagles et al., 2015). ![]() In the past 50 years there has been great emphasis and progress in measuring and modeling aspects of plate tectonics at various scales (e.g., Kearey et al., 2009). In combination, these divisions provide a powerful descriptive framework in which to understand and investigate Earth’s history and processes. 2017Įarth’s surface is divided into two types of crust, continental and oceanic, and into 14 major tectonic plates (Fig. ![]() Zealandia provides a fresh context in which to investigate processes of continental rifting, thinning, and breakup. 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. Today it is 94% submerged, mainly as a result of widespread Late Cretaceous crustal thinning preceding supercontinent breakup and consequent isostatic balance. Its isolation from Australia and large area support its definition as a continent-Zealandia. The region has elevated bathymetry relative to surrounding oceanic crust, diverse and silica-rich rocks, and relatively thick and low-velocity crustal structure. A 4.9 Mkm 2 region of the southwest Pacific Ocean is made up of continental crust.
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