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The Campbell Plateau is a large
oceanic plateau An oceanic or submarine plateau is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides. There are 184 oceanic plateaus in the world, covering an area of or about 5.11% of the ...
south of
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...
and the
Chatham Rise The Chatham Rise is an area of ocean floor to the east of New Zealand, forming part of the Zealandia continent. It stretches for some from near the South Island in the west, to the Chatham Islands in the east. It is New Zealand's most productiv ...
. It originated in the
Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final sta ...
n breakup and is part of
Zealandia Zealandia (pronounced ), also known as (Māori) or Tasmantis, is an almost entirely submerged mass of continental crust that subsided after breaking away from Gondwanaland 83–79 million years ago.Gurnis, M., Hall, C.E., and Lavier, L.L., ...
, a largely submerged
continent A continent is any of several large landmasses. Generally identified by convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. Ordered from largest in area to smallest, these seven ...
. The above sea level parts of the plateau — the
Bounty Islands The Bounty Islands ( mi, Moutere Hauriri; "Island of angry wind") are a small group of 13 uninhabited granite islets and numerous rocks, with a combined area of , in the South Pacific Ocean. Territorially part of New Zealand, they lie about e ...
,
Antipodes Islands The Antipodes Islands ( Maōri: Moutere Mahue; "Abandoned island") are inhospitable and uninhabited volcanic islands in subantarctic waters to the south of – and territorially part of – New Zealand. The 21 km2 archipelago lies 860  ...
,
Auckland Islands The Auckland Islands (Māori: ''Motu Maha'' "Many islands" or ''Maungahuka'' "Snowy mountains") are an archipelago of New Zealand, lying south of the South Island. The main Auckland Island, occupying , is surrounded by smaller Adams Islan ...
and Campbell Island — form part of the
New Zealand Subantarctic Islands The New Zealand Subantarctic Islands comprise the five southernmost groups of the New Zealand outlying islands. They are collectively designated as a UNESCO World Heritage Site. Most of the islands lie near the southeast edge of the largel ...
which were declared a
World Heritage Site A World Heritage Site is a landmark or area with legal protection by an international convention administered by the United Nations Educational, Scientific and Cultural Organization (UNESCO). World Heritage Sites are designated by UNESCO for ...
in 1998. Large parts of the Campbell Plateau lie less than 1000 m below sea level. It rises to 500 m at the Pukaki Rise and emerges above sea level at the Auckland and Campbell Islands. Covering an area of , the Campbell Plateau has a gently undulating bathymetry with major rises trending east-west: Campbell Island Rise, Pukaki Rise, and Bounty Island Ridge. There are two near-parallel rises on the western margin: Stewart Island–Snare Island Rise and Auckland Island platform. The continental slopes are steep on western and southern margins while the northern margin slowly falls into the Bounty Trough.


Geology

The Campbell Plateau is a roughly triangular,
craton A craton (, , or ; from grc-gre, κράτος "strength") is an old and stable part of the continental lithosphere, which consists of Earth's two topmost layers, the crust and the uppermost mantle. Having often survived cycles of merging and ...
ic
microcontinent Continental crustal fragments, partly synonymous with microcontinents, are pieces of continents that have broken off from main continental masses to form distinct islands that are often several hundred kilometers from their place of origin. Caus ...
which formed during the break-up of Gondwana around 80 Ma. Large parts of the plateau are made of
Palaeozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and '' ...
or older
granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies un ...
s overlain by much younger
shield volcano A shield volcano is a type of volcano named for its low profile, resembling a warrior's shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more vi ...
es who form the Auckland and Campbell Islands. The Campbell Plateau is made of continental crust, but, as such, is unusually thin. The reason for this is debated, but there are two likely candidates: either an Early Cretaceous extensional event or the Late Cretaceous break-up between New Zealand and Antarctica. Cretaceous
extension Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (predicate logic), the set of tuples of values that satisfy the predicate * Ext ...
between the South Island and the Campbell Plateau created the
Great South Basin The Great South Basin is an area of mainly sea to the south of the South Island of New Zealand. Starting in the 1960s, the area was explored and drilled for oil deposits by various, mostly international minerals companies — including Hunt Oil ...
in which 8 km of sediments have since accumulated. The Bounty Trough was created during the same process. The Campbell Plateau can have been affected by this extension or an earlier event. The islands are composed of continental rocks. The western islands, Auckland, Snares, and Stewart, have a 100–120 Ma-old Middle Cretaceous basement made of granites. On Snares and Stewart islands schists of similar age suggest metamorphism ceased about this time. The basement of Campbell Island and Fiordland are both made of Palaeozoic schists. Bounty Islands are made of 189 Ma-old
granodiorite Granodiorite () is a coarse-grained ( phaneritic) intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar. The term banatite is sometimes used informally for various rocks ranging from gr ...
and Precambrian-Cambrian
greywacke Greywacke or graywacke (German ''grauwacke'', signifying a grey, earthy rock) is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lit ...
s have been dredge near the island. The Antipodes Islands, in contrast, are composed of Quaternary alkaline olivine basalts. Most plate-tectonic reconstructions place the Campbell Plateau together with the Lord Howe Rise, the Challenger Plateau, and the Ross Sea before the break-up of Gondwana. These four structures have similar crustal thickness and underwent the same pre-break-up process of crustal thinning and underplating during the Early Cretaceous or Jurassic. The southern margin of the plateau was located next to the continental shelves of the eastern Ross Sea and Marie Byrd Land. There are two systems of magnetic anomalies on the Campbell Plateau: the Stokes Magnetic Anomaly System (SMAS) and the Campbell Magnetic Anomaly System (CMAS). The origin and relationship of these anomalies remain unclear.


Biogeology

The islands are important breeding centres for both endemic and circumpolar species, including the royal albatross, crested penguin, and
Hooker's sea lion The New Zealand sea lion (''Phocarctos hookeri''), once known as Hooker's sea lion, and as or (male) and (female) in Māori, is a species of sea lion that is endemic to New Zealand and primarily breeds on New Zealand's subantarctic Auckland a ...
. The southern part of
South Island The South Island, also officially named , is the larger of the two major islands of New Zealand in surface area, the other being the smaller but more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman ...
(
Fiordland Fiordland is a geographical region of New Zealand in the south-western corner of the South Island, comprising the westernmost third of Southland. Most of Fiordland is dominated by the steep sides of the snow-capped Southern Alps, deep lake ...
, Southland and
Otago Otago (, ; mi, Ōtākou ) is a region of New Zealand located in the southern half of the South Island administered by the Otago Regional Council. It has an area of approximately , making it the country's second largest local government reg ...
) can be considered part of the Campbell Plateau, both biologically and geologically. Endemic taxa include the spider genus ''
Gohia ''Gohia'' is a genus of South Pacific araneomorph spiders in the family Toxopidae, and was first described by R. de Dalmas in 1917. Species it contains four species, all from New Zealand New Zealand ( mi, Aotearoa ) is an island coun ...
'', the frog species '' Puhuruhuru patersoni'', and nine genera of beetles. The order
Lepidoptera Lepidoptera ( ) is an order of insects that includes butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 families and 46 superfamilies, 10 percent of the total described speci ...
(moths and butterflies) also link the southern South Island to the New Zealand Subantarctic Islands.
Macquarie Island Macquarie Island is an island in the southwestern Pacific Ocean, about halfway between New Zealand and Antarctica. Regionally part of Oceania and politically a part of Tasmania, Australia, since 1900, it became a Tasmanian State Reserve in 197 ...
is biologically but not geologically related to the Campbell Plateau. The island is made of
oceanic crust Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic ...
that formed at the Macquarie Triple Junction. This
triple junction A triple junction is the point where the boundaries of three tectonic plates meet. At the triple junction each of the three boundaries will be one of three types – a ridge (R), trench (T) or transform fault (F) – and triple junctions can b ...
was originally located adjacent to the Campbell Plateau but is now isolated south of it due to sea floor spreading. The plateau and the island share several endemic taxa, including six beetle species, a fly genus ('' Schoenophilus'') and a vascular plant genus ('' Pleurophyllum''). Further support for this connection comes from the aralia genus ''
Stilbocarpa ''Stilbocarpa'' is a genus of flowering plant most often placed in the family Araliaceae; it might be closer to the Apiaceae however. It comprises 3 species, two of which are endemic to New Zealand, while one is also found on Australia's subant ...
'' and possibly the
cormorant Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the IOC adopted a consensus taxonomy of seven ge ...
.


Oceanography

South of the Campbell Plateau, the eastward-flowing
Antarctic Circumpolar Current The Antarctic Circumpolar Current (ACC) is an ocean current that flows clockwise (as seen from the South Pole) from west to east around Antarctica. An alternative name for the ACC is the West Wind Drift. The ACC is the dominant circulation feat ...
(ACC) is bounded by the Antarctic Polar Front (APF) and the Subantarctic Front (SAF). It reaches New Zealand with an average volume of c. 130×106 m3/s. South of New Zealand it is partly deflected in the
Tasman Sea The Tasman Sea (Māori: ''Te Tai-o-Rēhua'', ) is a marginal sea of the South Pacific Ocean, situated between Australia and New Zealand. It measures about across and about from north to south. The sea was named after the Dutch explorer ...
as a broad, weak flow. The main part of the ACC, however, passes around the Macquarie Ridge together with the SAF and then flows north along the eastern margin of the Campbell Plateau. At 55°S and 50°S the ACC turns eastward again. There is, however, a wind-driven
Ekman transport Ekman transport is part of Ekman motion theory, first investigated in 1902 by Vagn Walfrid Ekman. Winds are the main source of energy for ocean circulation, and Ekman Transport is a component of wind-driven ocean current. Ekman transport occurs w ...
of surface water across the Campbell Plateau. At the Subtropical Convergence the Southland Current rounds the South Island and flows north-east along the island's east coast. From there it entrains Subantarctic and subtropical waters across the north-western Campbell Plateau before branching over the Chatman Rise north of the plateau.


References


Notes


Sources

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External links


Encyclopaedia of New Zealand entry on the Campbell Plateau
{{Oceanic features of Zealandia, state=collapsed Geography of the New Zealand seabed Plateaus of the Pacific Ocean Zealandia