Kerguelen plateau

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Topography of the Kerguelen plateau. On either side, Elan Bank extends west and William Ridge extends east.
Location of the Kerguelen Plateau in the Indian Ocean, marked by a white ellipse

The Kerguelen Plateau is an oceanic plateau and a Large Igneous Province (LIP) in the southern Indian Ocean . It is located about 3000 km southwest of Australia and roughly forms a rectangle that is more than 2300 km long and up to 600 km wide from northwest to southeast. The plateau is on average 2000 m higher than the surrounding sea floor and breaks through the water surface in two places with the Kerguelen Archipelago and the Heard and McDonald Islands .

Geographical expansion

The Kerguelen Plateau is one of the largest LIPs in the world with an area of ​​approximately 1,250,000 km² . It lies on the Antarctic Plate and is separated from Australia by the Southeast Indian Ridge , from Africa by the Southwest Indian Ridge and from the actual Antarctic land mass by two deep-sea basins . The Broken Ridge Plateau and the Ninety-degree East Ridge lie north of the oceanic ridges of the Indian Ocean, but share the history of its origins with the Kerguelen Plateau .

Geological evolution

Subdivision of the plateau
N: northern part with the Kerguelen Islands;
C: central part with the Heard Islands;
S: south part; E: Elan Bank;
Surrounding deep-sea basins: (En) derby-, (Cr) ozet-,
(AA) = Australian-Antarctic and (La) buan basins

Below the plateau in the earth's mantle is a so-called hotspot , which is believed to be the cause of the formation of the Kerguelen Archipelago and of today's volcanism on the Heard and McDonald Islands. The formation of the plateau began shortly after the breakup of Gondwana approximately 130 million years ago ( mya ). Since the first opening of what is now the Indian Ocean, the almost fixed and very extensive Kerguelen hotspot has created some striking structures that are now far apart. In chronological order of origin these are:

  • 132 to 123 mya: the Bunbury basalts in Western Australia
  • 118 mya: the Rajmahal Trapps in northeast India
  • 119 to 110 mya: the southern Kerguelen plateau (SKP)
  • 115 mya: various lamprophyres in India and in Antarctica
  • 108 mya: the Elan Bank
  • around 100 mya: the central Kerguelen plateau (CKP)
  • 95 mya: the Broken Ridge
  • 68 mya: the Skiff Bank
  • 82 mya to 38 mya: the ninety-degree east ridge
  • 35 mya: the northern Kerguelen plateau (NKP)

Today's favored model of the time course explains the structures found with a long and complex interaction of the Kerguelen hotspot with the separation of the three continental plates of India , Australia and Antarctica . The Kerguelen Plateau itself essentially marks the position of the hotspot under the oceanic crust in today's Indian Ocean and shows the movement of the Antarctic plate. Other rocks were transported away from the location of the hotspot by the movement of the Indian and Australian plates. Since it is the separation of three plates , there are three different directions of migration of the rocks. Today you can find rocks from the Kerguelen hotspot on the Antarctic plate in the Kerguelen plateau, on the Australian plate west of Australia and on the Indian plate south of India. The rocks of the plateau itself differ significantly from those from mid-ocean ridges and contain parts of continental crust.

Separation of India and Australia

The oldest volcanic events associated with the Kerguelen hotspot are the formation of the basalts of Bunbury in southwestern Australia and the Rajmahal Trapps in eastern India. These continental basalts were formed together with the southern and oldest part of the Kerguelen Plateau during the first opening of today's Indian Ocean. No special properties of the magma from the hotspot can yet be derived from the nature of the basalts .

Separation of India and Antarctica

The magma production of the Kerguelen hotspot reached its maximum between 120 million years ago and 95 million years ago and reached up to 0.9 km³ per year. However, no traces of the plate movement such as oceanic ridges or submarine mountain ranges can be found from this time . This large magma production coincides with the emergence of microcontinental fragments like the Elan Bank. Since the Indian Ocean began to open 130 million years ago, the hotspot has shifted approximately 3 to 10 degrees of latitude south, constantly moving away from the boundary between the Indian and Antarctic plates. The Elan Bank and the southern Kerguelen Plateau were originally connected to the Indian continent and still show a large proportion of the continental lithosphere to this day .

Cenozoic volcanism

The Kerguelen hotspot created the approximately 5000 km long ninety-degree east ridge between 82 and 38 mya, the rock composition of which indicates that it was formed near a spreading zone . However, a counterpart of this structure on the Antarctic plate is missing. The northern Kerguelen Plateau, formed a little later, was deposited over relatively old oceanic crust and essentially consists of flood basalts . At the end of this phase, the expansion zone shifted to the north, after which the hotspot could only influence the Antarctic plate. Until about a million years ago, volcanic activity can be detected on the Kerguelen Islands. Over the past 21 million years, various volcanic structures have emerged in the central Kerguelen Plateau, including the Heard and McDonald Islands, on which active volcanoes still exist today.

65 million years ago, the central Kerguelen Plateau and Broken Ridge were connected and were near the plate boundaries in the Indian Ocean. The Broken Ridge rocks were formed during 25 million years of high volcanic activity, followed by 40 million years of low activity.

In this most recent phase of extensive volcanism, there were frequent explosive eruptions that released large amounts of gas and dust into the atmosphere and thus may well have led to global environmental changes .

Other structures in the southern Indian Ocean

In the southern Indian Ocean there are other submarine structures such as plateaus and ridges, the formation of which is associated with the separation of the continents Antarctica, India and Australia, but which have different origins than the Kerguelen Plateau. No connection to a hotspot could be found for the Wallaby Plateau off northwest Australia , which was formed around 136 to 158 mya. The Naturaliste Plateau and the Exmouth Plateau also largely do not consist of volcanic rocks.

Microcontinent

As early as the early 1970s, sediments containing lignite and other continental rocks, such as B. Gneiss , discovered. The mixture of volcanic and continental rocks makes the Kerguelen Plateau very different from other LIPs. Investigations of the non-volcanic rocks suggest that at least parts of the plateau were above sea level for extended periods three times during the period between 100 million and 20 million years ago. This applies above all to the southern and central part of the plateau, the southern part probably formed an island with an area of ​​approx. 500,000 km² and mountains that reached up to 2000 m above sea level. During the Middle Cretaceous , large parts of the areas above sea level were probably covered with coniferous forests.

Marine fauna

On the southern edge of the plateau, there are above-average concentrations of minke , sperm and humpback whales . The whales find very good feeding opportunities here thanks to a combination of several special features. The plateau forms an obstacle to the Antarctic Circumpolar Current , deflecting it northwards and bringing nutrient-rich cold deep water close to the surface. The same effect also shifts the mean drift ice boundary to the north. This creates a zone with increased production of small organisms such as plankton and krill, which serve as a food source for the whales.

See also

Individual evidence

  1. ↑ a b University of Texas at Austin (ed.): UT Austin scientist plays major role in study of underwater "micro-continent" . May 28, 1999 ( cc.utexas.edu [accessed July 21, 2016]). www1.cc.utexas.edu ( Memento of the original from September 18, 2007 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www1.cc.utexas.edu
  2. ↑ a b c Bénard et al .: The Kerguelen plateau: Records… In: Marine and Petroleum Geology . tape 27 , no. 3 , 2010, p. 634 , doi : 10.1016 / j.marpetgeo.2009.08.011 ( researchgate.net [PDF; accessed on July 15, 2016]).
  3. ^ JM Whittaker, SE Williams, RD Müller: Revised tectonic evolution of the Eastern Indian Ocean . In: Geochemistry, Geophysics, Geosystems . tape 14 , no. 6 , 2013, p. 1898 . determines a probable diameter of the active zone of the hotspot of 400 km.
  4. ↑ Frey et. Al .: Leg 183 Summary ... In: Proceedings of the Ocean Drilling Program . tape 183 , 2003, p. 4 .
  5. ^ A b c d e F. A. Frey, MF Coffin, PJ Wallace: LIP Reading: Understanding the Kerguelen Plateau and Broken Ridge . In: Scientific results of the Ocean Drilling Program . 2003 ( odplegacy.org [PDF; accessed July 22, 2016]).
  6. ^ JM Whittaker, SE Williams, RD Müller: Revised tectonic evolution of the Eastern Indian Ocean . In: Geochemistry, Geophysics, Geosystems . tape 14 , no. 6 , 2013, p. 1906 f .
  7. ↑ Ingle, Scoates, Weis, Kent: Origin of Cretaceous continental tholeiites in southwestern ... In: Chemical Geology . tape 209 , 2004, pp. 84, 102 .
  8. ↑ Frey, Coffin, Wallace, Weis: Leg 183 Synthesis ... In: Proceedings of the Ocean Drilling Program . tape 183 , 2003, p. 1, 4 .
  9. ^ A b J. M. Whittaker, SE Williams, RD Müller: Revised tectonic evolution of the Eastern Indian Ocean . In: Geochemistry, Geophysics, Geosystems . tape 14 , no. 6 , 2013, p. 1905 .
  10. ↑ a b c d Frey et al .: Leg 183 Summary… In: Proceedings of the Ocean Drilling Program . tape 183 , 2003, p. 5 f .
  11. ↑ Frey, Coffin, Wallace, Weis: Leg 183 Synthesis ... In: Proceedings of the Ocean Drilling Program . tape 183 , 2003, p. 5 .
  12. ↑ Kerguelen Plateau - Broken Ridge , D. Weis and F. Frey at the "Seventh Annual VM Goldschmidt Conference" of the USRA . Retrieved August 2, 2016.
  13. ↑ Frey, Coffin, Wallace, Weis, Zhao et.al .: Origin and evolution of a submarine large igneous province ... In: Earth and Planetary Science Letters . tape 176 , 2000, pp. 77 .
  14. ^ JM Whittaker, SE Williams, RD Müller: Revised tectonic evolution of the Eastern Indian Ocean . In: Geochemistry, Geophysics, Geosystems . tape 14 , no. 6 , 2013, p. 1891 .
  15. ↑ Leg 183 Summary: Kerguelen Plateau-Broken Ridge — A Large Igneous Province . In: Proceedings of the Ocean Drilling Program . tape 183 , p. 5 ff . ( odp.tamu.edu ).
  16. ↑ Description of the Wallaby Plateau on Geoscience Australia . Retrieved July 25, 2016.
  17. ↑ Description of the Naturaliste Plateau on Geoscience Australia . Retrieved July 29, 2016.
  18. ^ Alan Nairn (ed.): The Ocean Basins and Margins: The Indian Ocean . Springer, 2013, ISBN 978-1-4615-8038-6 , pp. 80 ff . ( books.google.com [accessed July 29, 2016]).
  19. ↑ R. Schlic, JR Delteil, J. Moulin, P. Patriat, R. Guillaume: Mise en évidence d'une sédimentation de marge continentale sur le plateau de Kerguelen-Heard . In: Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences, Série D: Sciences Naturelles . tape 272 , no. 16 , 1971, p. 2060–2063 (French, gallica.bnf.fr [accessed July 21, 2016]).
  20. ↑ Leg 183 Summary: Kerguelen Plateau-Broken Ridge — A Large Igneous Province . In: Proceedings of the Ocean Drilling Program . tape 183 ( odp.tamu.edu ).
  21. ↑ Leg 183 Summary: Kerguelen Plateau-Broken Ridge — A Large Igneous Province . In: Proceedings of the Ocean Drilling Program . tape 183 , p. 16 f . ( odp.tamu.edu ).
  22. ↑ Mohr, Wähnert, Lazarus: Mid-Cretaceous paleobotany and ... In: Proc. ODP, Sci. Results . tape 183 , 2002, p. 10 f .

literature

  • F. Bénard, JP Callot, R. Vially, J. Schmitz, W. Roest, M. Patriat, B. Loubrieu: The Kerguelen plateau: Records from a long-living / composite microcontinent . In: Marine and Petroleum Geology . tape 27 , no. 3 , 2010, p. 633–649 , doi : 10.1016 / j.marpetgeo.2009.08.011 ( researchgate.net [PDF; accessed July 15, 2016]).
  • FA Frey, MF Coffin, PJ Wallace, D. Weis: Leg 183 Synthesis: Kerguelen Plateau-Broken Ridge — A Large Igneous Province . In: Proceedings of the Ocean Drilling Program . tape 183 , 2003, p. 1–48 ( www-odp.tamu.edu [PDF; accessed on July 21, 2016]).
  • S. Ingle, JS Scoates, D. Weis, RW Kent: Origin of Cretaceous continental tholeiites in southwestern Australia and eastern India: insights from Hf and Os isotopes . In: Chemical Geology . tape 209 , 2004, pp. 83-106 , doi : 10.1016 / j.chemgeo.2004.04.023 ( researchgate.net [PDF; accessed on July 21, 2016]).
  • BAR Mohr, V. Wähnert, D. Lazarus: Mid-Cretaceous paleobotany and palynology of the central Kerguelen Plateau, southern Indian Ocean (ODP Leg 183, Site 1138) . In: Proc. ODP, Sci. Results . tape 183 , 2002, doi : 10.2973 / odp.proc.sr.183.008.2002 ( odp.tamu.edu [accessed July 21, 2016]).
  • JM Whittaker, SE Williams, RD Müller: Revised tectonic evolution of the Eastern Indian Ocean . In: Geochemistry, Geophysics, Geosystems . tape 14 , no. 6 , 2013, p. 1891–1909 , doi : 10.1002 / ggge.20120 ( onlinelibrary.wiley.com [accessed July 21, 2016]).
  • CT Tynan: Cetacean distributions and oceanographic features near the Kerguelen Plateau . In: Geophysical Research Letters . tape 24 , no. 22 , 1997, pp. 2793–2796 , doi : 10.1029 / 97GL02860 ( onlinelibrary.wiley.com [PDF; accessed July 22, 2016]).
  • FA Frey, MF Coffin, PJ Wallace, D. Weis, X. Zhao,…: Origin and evolution of a submarine large igneous province: the Kerguelen Plateau and Broken Ridge, southern Indian Ocean . In: Earth and Planetary Science Letters . tape 176 , 2000, pp. 73–89 ( nd.edu [PDF; accessed August 12, 2016]).

Web links

Commons : Kerguelen Plateau  - Collection of images, videos and audio files

Coordinates: 55 °  S , 76 °  E