Late Cretaceous India–Madagascar fit and timing of break-up related magmatism |
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| Authors: | TH Torsvik RD Tucker LD Ashwal LM Carter B Jamtveit KT Vidyadharan & P Venkataramana |
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| Institution: | VISTA, c/o Geological Survey of Norway, Leif Eirikssons vei 39, N-7491 Trondheim, Norway;Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130, USA;Department of Geology, Rand Afrikaans University, PO Box 524, Auckland Park, 2006 South Africa;Department of Geology, Rand Afrikaans University, PO Box 524, Auckland Park, 2006 South Africa;Department of Geology, University of Oslo, Sem Saelands vei 1, PO Box 1047 Blindern, N-0316 Oslo, Norway;Geological Survey of India, Operations Karnataka and Goa, Vasudha Bharan, Kamaraswamy, Bangalore 560078, India;Geological Survey of India, Marine Wing, PKV Bhandarkars Complex, Mannagudda, Mangalore 575003, India |
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| Abstract: | A U–Pb zircon age of 91.2 ± 0.2 Myr from western India (St. Mary islands) confidently links India with the Late Cretaceous magmatic province in Madagascar (≈ 84–92 Ma), and the U–Pb age is within analytical error of the U–Pb age of the Analalava gabbro pluton (91.6 ± 0.3 Myr) in northeastern Madagascar. Palaeomagnetic data from India and Madagascar allow us to postulate a new India–Madagascar fit (Euler latitude = 14.24°, longitude = 38.8° and rotation angle = –69.2°). This fit is applicable to the Late Cretaceous, directly prior to and during the early phase of Madagascar–India separation. In our Late Cretaceous reconstruction, south-west India runs roughly subparallel with the first known break-up related magnetic anomaly (A34); it maintains a close connection between Mada-gascar and India, but places India slightly rotated compared to the eastern margin of Madagascar and more northerly compared with some reconstructions. St. Mary magmatism is linked to the initial break-up between India and Madagascar, and magmatism probably resulted from rift-related extensional processes initially induced by the Marion hotspot underlying southern Madagascar during the Late Cretaceous. |
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