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)
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
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
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