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Ulf Söderlund

Ulf Söderlund

Professor

Ulf Söderlund

Return to Rodinia? Moderate to high palaeolatitude of the São Francisco/Congo craton at 920 Ma

Författare

  • D. A D Evans
  • R. I F Trindade
  • E. L. Catelani
  • M. S. D'Agrella-Filho
  • L. M. Heaman
  • E. P. Oliveira
  • U. Söderlund
  • R. E. Ernst
  • A. V. Smirnov
  • J. M. Salminen

Summary, in English

Moderate to high palaeolatitudes recorded in mafic dykes, exposed along the coast of Bahia, Brazil, are partly responsible for some interpretations that the São Francisco/Congo craton was separate from the low-latitude Rodinia supercontinent at about 1050 Ma. We report new palaeomagnetic data that replicate the previous results. However, we obtain substantially younger U-Pb baddeleyite ages from five dykes previously thought to be 1.02-1.01 Ga according to the 40Ar/39Ar method. Specifically, the so-called «A-normal» remanence direction from Salvador is dated at 924.2±3.8 Ma, within error of the age for the «C» remanence direction at 921.5±4.3 Ma. An «A-normal» dyke at Ilh»us is dated at 926.1±4.6 Ma, and two «A-normal» dykes at Olivença have indistinguishable ages with best estimate of emplacement at 918.2±6.7 Ma. We attribute the palaeomagnetic variance of the «A-normal» and «C» directions to lack of averaging of geomagnetic palaeosecular variation in some regions. Our results render previous 40Ar/39Ar ages from the dykes suspect, leaving late Mesoproterozoic palaeolatitudes of the São Francisco/Congo craton unconstrained. The combined «A-normal» palaeomagnetic pole from coastal Bahia places the São Francisco/Congo craton in moderate to high palaeolatitudes at c. 920 Ma, allowing various possible positions of that block within Rodinia.

Avdelning/ar

  • Geologiska institutionen

Publiceringsår

2015-05-28

Språk

Engelska

Sidor

167-190

Publikation/Tidskrift/Serie

Geological Society Special Publication

Volym

424

Issue

1

Dokumenttyp

Del av eller Kapitel i bok

Förlag

Geological Society of London

Ämne

  • Geology

Aktiv

Published

ISBN/ISSN/Övrigt

  • ISSN: 03058719