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A New Atlantis? Lost Land Beneath the Waves. A Precambrian microcontinent in the Indian Ocean

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Geological detectives are piecing together an intriguing seafloor puzzle. The Indian Ocean and some of its islands, scientists say, may lie on top of the remains of an ancient continent pulled apart by plate tectonics between 50 million and 100 million years ago. CEED researchers are among the detectives. The article; A Precambrian microcontinent in the Indian Ocean in Nature Geoscience got several comments in international press in February 2013. In the Nature article researchers from CEED/Department of Geosciences, UiO, Norway, and researchers from Germany and Britain, suggest that the Indian Ocean has fragments of an ancient continental crust. – The Laccadive–Chagos Ridge

and Southern Mascarene Plateau in the north-central and western Indian Ocean, respectively, are thought to be volcanic chains formed above the Réunion mantle plume over the past 65.5 million years. Here we use U–Pb dating to analyse the ages of zircon xenocrysts found within young lavas on the island of Mauritius, part of the Southern Mascarene Plateau. We find that the zircons are either Palaeoproterozoic (more than 1,971 million years old) or Neoproterozoic (between 660 and 840 million years old). We propose that the zircons were assimilated from ancient fragments of continental lithosphere beneath Mauritius, and were brought to the surface by plume-related lavas. We use gravity data inversion to map crustal thickness and find that Mauritius forms part of a contiguous block of anomalously thick crust that extends in an arc northwards to the Seychelles. Using plate tectonic reconstructions, we show that Mauritius and the adjacent Mascarene Plateau may overlie a Precambrian microcontinent that we call Mauritia. On the basis of reinterpretation of marine geophysical data, we propose that Mauritia was separated from Madagascar and fragmented into a ribbon-like configuration by a series of mid-ocean ridge jumps during the opening of the Mascarene ocean basin between 83.5 and 61 million years ago. We suggest that the plume-related magmatic deposits have since covered Mauritia and potentially other continental fragments. Authors: Trond H. Torsvik, Hans Amundsen, Ebbe H. Hartz, Fernando Corfu, Nick Kusznir, Carmen Gaina, Pavel V. Doubrovine, Bernhard Steinberger, Lewis D. Ashwal & Bjørn Jamtveit. Source:  Nature Geoscience


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