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A palaeomagnetic an...
A palaeomagnetic and Ar-40/Ar-39 study of late precambrian sills in the SW part of the Amazonian craton: Amazonia in the Rodinia reconstruction
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- Elming, Sten-åke (author)
- Luleå tekniska universitet,Geovetenskap och miljöteknik
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- D'Agrella-Filho, M. S. (author)
- Universidade de São Paulo
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- Page, Laurence (author)
- Lund University,Lunds universitet,Berggrundsgeologi,Geologiska institutionen,Naturvetenskapliga fakulteten,Lithosphere and Biosphere Science,Department of Geology,Faculty of Science,University of Lund
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- Tohver, E. (author)
- School of Earth and Geographical Sciences, University of Western Australia, Crawley
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- Trindade, R. I. F. (author)
- Universidade de São Paulo
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- Pacca, I. I. G. (author)
- Universidade de São Paulo
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- Geraldes, M. C. (author)
- Faculdade de Geologia, Universidade do Estado do Rio de Janeiro
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- Teixeira, W. (author)
- Instituto de Geociências, Universidade de São Paulo
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(creator_code:org_t)
- 2009
- 2009
- English.
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In: Geophysical Journal International. - 0956-540X .- 1365-246X. ; 178:1, s. 106-122
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http://dx.doi.org/10...
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https://doi.org/10.1...
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Abstract
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- A new key palaeomagnetic pole (Plat. = 64.3 degrees S, Plon. = 271.0 degrees E, N = 14, A(95) = 9.2 degrees; Q = 5) is calculated from a primary magnetization isolated in early Neoproterozoic Aguapei basic sills and dykes hosted by 1.3-1.0 Ga sedimentary rocks from the southwestern part of the Amazon craton. The characteristic remanence carried by stable, pseudo-single domain titanomagnetite shows two antipodal polarities that pass a reversals test. Magnetic anisotropy for most sites shows fabric orientations that are typical of sills, with horizontal magnetic foliations concordant to the flat-lying bedding of the host sedimentary rocks. Ar-40/Ar-39 analyses for one of the sills reveal a well-defined plateau age at 981 +/- 2 Myr. A tectonic reconstruction for Amazonia relative Laurentia based on this new pole 'is consistent with' a position of the present northwestern part of Amazonia attached with eastern Laurentia close to Greenland at ca. 981 Ma. On basis of palaeomagnetic and geological data, we propose a scenario where Amazonia moved northeastwards along the present southeast coast of Laurentia from ca. 1200 to 980 Ma. By 980 Ma, Amazonia is placed alongside Laurentia and Baltica, in a position similar to other reconstructions of Rodinia but with a significantly different orientation.
Subject headings
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Geology (hsv//eng)
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Geofysik (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Geophysics (hsv//eng)
Keyword
- Rock and mineral magnetism
- Magnetic fabrics and anisotropy
- Palaeomagnetism applied to tectonics
- Applied Geophysics
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