Оңтүстік Мұхиттың Кергелен Платосы

Oceanic plateau in the southern Indian Ocean

The Kerguelen Plateau (/pron/'/k//ɜr//ɡ//əl//ən/, /k//ər/'/ɡ//eɪ//l//ən/), also known as the Kerguelen–Heard Plateau, is an oceanic plateau and large igneous province (LIP) located on the Antarctic Plate, in the southern Indian Ocean. It is about to the southwest of Australia and is nearly three times the size of California. The plateau extends for more than in a northwest–southeast direction and lies in deep water. The plateau was produced by the Kerguelen hotspot, starting with or following the breakup of Gondwana about 130 million years ago. A small portion of the plateau breaks sea level, forming the Kerguelen Islands (a French overseas territory) plus the Heard and McDonald Islands (an Australian external territory). Intermittent volcanism continues on the Heard and McDonald Islands.

Symmetrically across the Indian Ocean ridge and due west of Australia is the Broken Ridge underwater volcanic plateau, which at one time was contiguous with the Kerguelen Plateau before rifting by the mid ocean ridge. To the north of Broken Ridge is the linear Ninety East Ridge which continues almost due north into the Bay of Bengal and is considered to be a hotspot track. One of the largest igneous provinces (LIPs) in the world, the Kerguelen Plateau covers an area of and rises above the surrounding oceanic basins. Most of the plateau is less than below sea level. Located on the Antarctic Plate, the Kerguelen Plateau is separated from Australia by the Southeast Indian Ridge (SEIR) and from Africa by the Southwest Indian Ridge (SWIR). These two ridges meet at the Rodriguez Triple Junction. It is separated from Antarctica by Princess Elizabeth Trough and the Cooperation Sea. The eastern margin north of the William Ridge is steep and formed during the breakup between the Kerguelen Plateau and the Broken Ridge. The southern part of the margin is separated from the Australian–Antarctic Basin by the deep Labuan Basin.

From the initial opening of the Indian Ocean until present, the Kerguelen hotspot has produced several, now widely dispersed, large scale structures. These are now known to cover a time range from (Ma) with the oldest assigned structure being the Comei large igneous province in south eastern Tibet. Historic work had believed that the hotspot became active more recently in what is now south east Australia. the Naturaliste Plateau (offshore Western Australia) formed 132–128 Ma (million years ago); the Rajmahal Traps in Northeast India 118–117 Ma (million years ago); and finally lamprophyres in India and Antarctica 115–114 Ma (million years ago).

The oldest Australian volcanism that can be attributed to the Kerguelen plume are the Bunbury Basalt (137–130.5 Ma (million years ago) The Bunbury Basalt is not of flood basalt dimensions which suggests that the mantle underlying the Kerguelen hotspot was neither significantly hot, wet, or voluminous. In contrast, the magmatism that produced the Australia–India breakup 136–158 Ma (million years ago) created the Wallaby Plateau, but no known hotspot has been linked to this event.

The output from the Kerguelen hotspot peaked 120–95 Ma (million years ago), 12–70 Ma (million years ago) after the India–Antarctica breakup. No ridges or hotspot tracks such as Walvis–Rio Grande, Chagos–Laccadive, Greenland–Scotland have been found in the Princess Elizabeth Trough between SKP and Antarctica or along India's conjugate eastern continental margin. The relation between the Kerguelen hotspot and these continental breakup and volcanic margins is instead similar to that between the Réunion hotspot and the Deccan Traps and the breakup between western India and the Seychelles. Around 83.5 Ma (million years ago) sea floor spreading between India and Antarctica was asymmetric in the Kerguelen Plateau region with two thirds of the sea floor created being added to the Antarctic Plate. A ridge jump eventually transferred parts of the Kerguelen Plateau from the Indian Plate to the Antarctic Plate.

The Kerguelen hotspot produced the long Ninety East Ridge 82–38 Ma (million years ago), and geochemical evidence suggests that this occurred at or near a spreading ridge. The lack of a conjugate structure on the Antarctic Plate, however, makes it unlikely that the hotspot was located at a spreading ridge during this long period. As the Antarctic Plate then moved over the Kerguelen hotspot the NKP formed over relatively old oceanic crust. Flood basalts in the Kerguelen archipelago formed 30–24 Ma (million years ago) and less voluminous and more recent volcanism occurred until 1 Ma (million years ago). During the last 21 Ma (million years ago) volcanic structures have formed on the CKP, including Heard Island, and both Heard and McDonald Islands have had recent eruptions.

described tilted basement blocks near the Kerguelen Archipelago and were the first to identify the Kerguelen Plateau as of continental origin, in contrast to other LIPs. The presence of soil layers in the basalt which included charcoal and conglomerate fragments of gneiss indicate that much of the plateau was above sea level as what is termed a microcontinent for three periods between 100 million years ago and 20 million years ago (the charcoal was made by wildfires started by lightning or lava flows). Large parts of the now submarine Southern Kerguelen Plateaus (SKP) and Central Kerguelen Plateaus (CKP) were subaerial during the formation of the LIP. The SKP probably formed an island of with major peaks reaching above sea level. The Kerguelen Microcontinent may have been covered by dense conifer forest in the mid Cretaceous. as well as the early Cenozoic. Fossil wood fragments recovered from the Kerguelen Islands were identified as Araucarians and Cypresses, demonstrating that Kerguelen's flora may have been similar to that of the Antarctic flora found across the Southern Hemisphere. The plateau had been proposed as forming a land bridge between India and Antarctica during the Late Cretaceous, though this is now considered unsupported, with the plateau situated at a considerable distance from the nearest continents. It finally sank 20 million years ago and is now below sea level.

During the austral summer there is a high density of migratory whales including sperm, minke, and humpback whales along the southern end of the Kerguelen Plateau and the northern part of the adjacent Princess Elizabeth Trough. These whales choose this location for foraging because the Southern Front of the Antarctic Circumpolar Current is steered off by the Plateau—resulting in a poleward extent for the Southern Front only found near the Kerguelen Plateau. This brings shoaled, nutrient rich Upper Circumpolar Deep Water to the surface which brings macronutrients to the surface. Ice is additionally advected north along the eastern side of the plateau.