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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

Elming, S. -A.; D'Agrella-Filho, M. S.; Page, Laurence LU ; Tohver, E.; Trindade, R. I. F.; Pacca, I. I. G.; Geraldes, M. C. and Teixeira, W. (2009) In Geophysical Journal International 178(1). p.106-122
Abstract
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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Rock and mineral magnetism, Magnetic fabrics and anisotropy, Palaeomagnetism applied to tectonics
in
Geophysical Journal International
volume
178
issue
1
pages
106 - 122
publisher
Wiley-Blackwell
external identifiers
  • wos:000266979600008
  • scopus:67650230184
ISSN
0956-540X
DOI
10.1111/j.1365-246X.2009.04149.x
language
English
LU publication?
yes
id
1a4adaa2-949e-40e6-9655-51df8ec454a7 (old id 1442105)
date added to LUP
2009-07-27 11:09:37
date last changed
2017-05-07 03:37:04
@article{1a4adaa2-949e-40e6-9655-51df8ec454a7,
  abstract     = {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.},
  author       = {Elming, S. -A. and D'Agrella-Filho, M. S. and Page, Laurence and Tohver, E. and Trindade, R. I. F. and Pacca, I. I. G. and Geraldes, M. C. and Teixeira, W.},
  issn         = {0956-540X},
  keyword      = {Rock and mineral magnetism,Magnetic fabrics and anisotropy,Palaeomagnetism applied to tectonics},
  language     = {eng},
  number       = {1},
  pages        = {106--122},
  publisher    = {Wiley-Blackwell},
  series       = {Geophysical Journal International},
  title        = {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},
  url          = {http://dx.doi.org/10.1111/j.1365-246X.2009.04149.x},
  volume       = {178},
  year         = {2009},
}