Advanced

The Tomquist Sea and Baltica-Avalonia docking

Torsvik, Trond H LU and Rehnström, Emma LU (2003) In Tectonophysics 362(1-4). p.67-82
Abstract
Early Ordovician (Late Arenig) limestones from the SW margin of Baltica (Scania-Bomholm) have multicomponent magnetic signatures, but high unblocking components predating folding, and the corresponding palaeomagnetic pole (latitude = 19degreesN, longitude = 051degreesE) compares well with Arenig reference poles from Baltica. Collectively, the Arenig poles demonstrate a midsoutherly latitudinal position for Baltica, then separated from Avalonia by the Tomquist Sea. Tornquist Sea closure and the Baltica-Avalonia convergence history are evidenced from faunal mixing and increased resemblance in palaeomagnetically determined palaeolatitudes for Avalonia and Baltica during the Mid-Late Ordovician. By the Caradoc, Avalonia had drifted to... (More)
Early Ordovician (Late Arenig) limestones from the SW margin of Baltica (Scania-Bomholm) have multicomponent magnetic signatures, but high unblocking components predating folding, and the corresponding palaeomagnetic pole (latitude = 19degreesN, longitude = 051degreesE) compares well with Arenig reference poles from Baltica. Collectively, the Arenig poles demonstrate a midsoutherly latitudinal position for Baltica, then separated from Avalonia by the Tomquist Sea. Tornquist Sea closure and the Baltica-Avalonia convergence history are evidenced from faunal mixing and increased resemblance in palaeomagnetically determined palaeolatitudes for Avalonia and Baltica during the Mid-Late Ordovician. By the Caradoc, Avalonia had drifted to palaeolatitudes compatible with those of SW Baltica, and subduction beneath Eastern Avalonia was taking place. We propose that explosive vents associated with this subduction and related to Andean-type magmatism in Avalonia were the source for the gigantic Mid-Caradoc (c. 455 Ma) ash fall in Baltica (i.e. the Kinnekulle bentonite). Avalonia was located south of the subtropical high during most of the Ordovician, and this would have provided an optimum palaeoposition to supply Baltica with large ash falls governed by westerly winds. In Scama, we observe a persistent palaeomagnetic overprint of Late Ordovician (Ashgill) age (pole: latitude-4degreesS, longitude= 012degreesE). The remagnetisation was probably spurred by tectonic-derived fluids since burial alone is inadequate to explain this remagnetisation event. This is the first record of a Late Ordovician event in Scania, but it is comparable with the Shelveian event in Avalonia, low-grade metamorphism in the North Sea basement of NE Germany (440-450 Ma), and sheds new light on the Baltica-Avalonia docking. (C) 2002 Elsevier Science B.V. All rights reserved. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
K-bentonitesl, palaeogeography, Avalonia, Tornquist Sea, Baltica, remagnetisation, collision
in
Tectonophysics
volume
362
issue
1-4
pages
67 - 82
publisher
Elsevier
external identifiers
  • wos:000180919300005
  • scopus:0037421667
ISSN
0040-1951
DOI
language
English
LU publication?
yes
id
58a4c1b5-26e3-4e72-b2d4-6ceb49927c44 (old id 318366)
date added to LUP
2007-09-23 11:56:05
date last changed
2018-06-17 04:49:26
@article{58a4c1b5-26e3-4e72-b2d4-6ceb49927c44,
  abstract     = {Early Ordovician (Late Arenig) limestones from the SW margin of Baltica (Scania-Bomholm) have multicomponent magnetic signatures, but high unblocking components predating folding, and the corresponding palaeomagnetic pole (latitude = 19degreesN, longitude = 051degreesE) compares well with Arenig reference poles from Baltica. Collectively, the Arenig poles demonstrate a midsoutherly latitudinal position for Baltica, then separated from Avalonia by the Tomquist Sea. Tornquist Sea closure and the Baltica-Avalonia convergence history are evidenced from faunal mixing and increased resemblance in palaeomagnetically determined palaeolatitudes for Avalonia and Baltica during the Mid-Late Ordovician. By the Caradoc, Avalonia had drifted to palaeolatitudes compatible with those of SW Baltica, and subduction beneath Eastern Avalonia was taking place. We propose that explosive vents associated with this subduction and related to Andean-type magmatism in Avalonia were the source for the gigantic Mid-Caradoc (c. 455 Ma) ash fall in Baltica (i.e. the Kinnekulle bentonite). Avalonia was located south of the subtropical high during most of the Ordovician, and this would have provided an optimum palaeoposition to supply Baltica with large ash falls governed by westerly winds. In Scama, we observe a persistent palaeomagnetic overprint of Late Ordovician (Ashgill) age (pole: latitude-4degreesS, longitude= 012degreesE). The remagnetisation was probably spurred by tectonic-derived fluids since burial alone is inadequate to explain this remagnetisation event. This is the first record of a Late Ordovician event in Scania, but it is comparable with the Shelveian event in Avalonia, low-grade metamorphism in the North Sea basement of NE Germany (440-450 Ma), and sheds new light on the Baltica-Avalonia docking. (C) 2002 Elsevier Science B.V. All rights reserved.},
  author       = {Torsvik, Trond H and Rehnström, Emma},
  issn         = {0040-1951},
  keyword      = {K-bentonitesl,palaeogeography,Avalonia,Tornquist Sea,Baltica,remagnetisation,collision},
  language     = {eng},
  number       = {1-4},
  pages        = {67--82},
  publisher    = {Elsevier},
  series       = {Tectonophysics},
  title        = {The Tomquist Sea and Baltica-Avalonia docking},
  url          = {http://dx.doi.org/},
  volume       = {362},
  year         = {2003},
}