Boynes Islands and Elan Bank

Left Behind When India Moved North

I. Map boundaries: 50 to 60 degrees South; 56 to 70 degrees East

II. Country: France (French Southern and Antarctic Lands overseas territory)

III. Overview

This map area includes a small group of islands, Isles de Boynes, on the western edge of the Kerguelen Plateau, the second largest volcanic plateau in the world (the largest is called Ontong Java, and is northeast of New Guinea and the Solomon Islands along the equator). Volcanic activity has extended over the area for the last 130 million years, but most of the plateau is believed to have initially formed during two bursts of volcanic activity—one in the southern area between 109 and 115 million years ago and one in the central plateau about 85 to 88 million years ago. This was during the Cretaceous Period. During that burst, at least part of the plateau formed islands. Most of the plateau is now under water and has been so for millions of years, but at one time (Cretaceous Period), it was emergent or under shallow water. During the Cretacenous, Kerguelen was part of a land bridge between Antarctica and India-Madagascar. Wood fragments, charcoal, spores, and seeds found in late Cretaceous sediments now under more than 1,000 m of water indicate that the plateau was covered with forests.

Shortly after the Kerguelen hotspot formed, the Indian plate drifted across it as India and Antarctica separated. An area between Antarctica and India, the Elan Bank, was left behind. Now a western extension of the Kerguelen Plateau, the Elan Bank contains rocks with an affinity to those of the Eastern Ghats of India. Elan Bank originated adjacent to the Eastern Ghats and is a fragment of the continental crust now isolated in the southern Ocean to the north of Antarctica. Other rocks related to the Kerguelen hot spot are in western Australia, underwater along the Ninetyeast Ridge, and near the Amery Ice Shelf of Antarctica.

To the north of Elan Bank is Skiff Bank, which is believed to be the current location of the Kerguelen hot spot. To the west of Elan Bank is the Enderby Plain, noted as one of the least fertile areas in the Southern Ocean due to a lack of atmospheric dust deposition. There are no prevailing winds to bring atmospheric dust to this area. Winds in the Southern Ocean circle the South Pole and do not pass over any source of dust.

IV. Terrestrial Ecoregions

Tundra

AN 1104, Southern Indian Ocean Islands tundra. The Kerguelen Islands, of which the Boynes Islands are a part, harbor grasses, penguins, seabirds, and marine mammals.

V. Marine Ecoregions

Southern Ocean Realm, Subantarctic Islands Province

213. Heard and Macdonald Islands. Includes Elan Bank.

214. Kerguelen Islands. Includes Boynes Islands

VI. References

Bercovici, David and John Mahoney. 1994. Double Flood Basalts and Plume Head Separation at the 660-Kilometer Discontinuity. Science 266:1367-1369 (25 November).

Borissova, Irina et al. 2003. Structure and Development of a Microcontinent: Elan Bank in the southern Indian Ocean. Geochemistry, Geophysics, Geosystems 4:1071. http://www.agu.org/pubs/crossref/2003/2003GC000535.shtml (Accessed 1/2/2010).

Cassar, Nicholas et al. 2007. The Southern Ocean Biological Response to Aeolian Iron Deposition. Science 317:1067-1070 (24 August).

Coffin, Millard F., Fred A. Frey, Paul Wallace, and ODP Leg 183 Scientific Party. Large Igneous Province Reading: Understanding the Kerguelen Plateau and Broken Ridge. Consortium for Ocean Leadership, Ocean Drilling Program Legacy. www.odplegacy.org/PDF/Outreach/Brochures/GreatestHits2/hotspots.pdf

(Accessed 1/30/2010).

Coffin, Millard F., Fred A. Frey, Paul Wallace, and ODP Leg 183 Scientific Party. 2004. The Lost World: Environmental Effects During the Formation of a Giant Volcanic Province. Page 22 In ODP Highlights. International Scientific Contributions from the Ocean Drilling Program. Joint Oceanographic Institutions, Washington. www.odplegacy.org/PDF/Outreach/Brochures/ODP_Greatest_Hits2.pdf

Duncan, Robert A. and Martin R. Risk. 1997. The Life Cycle of Mantle Plumes. P. 31 In ODP’s Greatest Hits. Joint Oceanographic Institutions, Washington. www.odplegacy.org/PDF/Outreach/Brochures/ODP_Greatest_Hits.pdf

Geoscience Australia. 2008. Kerguelen Plateau. Regional Petroleum Geology of Australia. http://www.ga.gov.au/oceans/sa_Kergln.jsp (Accessed January 30, 2010)

Hassler, Deborah R. and Nobumichi Shimizu. Osmium Isotopic Evidence for Ancient Subcontinental Lithospheric Mantle Beneath the Kerguelen Islands, Southern Indian Ocean. Science 280:418-421 (17 April).

Ingle, Stephanie. 2007. The Kerguelen Large Igneous Province. http://www.largeigneousprovinces.org/07apr.html (accessed January 1, 2010).

Ingle, S., D. Weis, and F.A. Frey. 2002. Indian Continental Crust Recovered from Elan Bank, Kerguelen Plateau (ODP Leg 183, Site 1137). Journal of Petrology 43:1241-1257.

Kerr, Richard A. 1978. Plate Tectonics: Hot Spot Implicated in Ridge Formation. Science 202:503-505 (3 November).

Olson, David M., et al., 2001. Terrestrial Ecoregions of the World: A New Map of Life on Earth. BioScience 51:933-938. Ecoregion map at http://www.nationgeographic.com/wildworld/terrestrial.html

Sampson, Scott D. et al. 1998. Predatory Dinosaur Remains from Madagascar: Implications for the Cretaceous Biogeography of Gondwana. Science 280:1048-1051 (15 May).

Spalding, Mark D. et al. 2007. Marine Ecoregions of the World: A Bioregionalization of Coastal and Shelf Areas. BioScience 57:573-583.