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Paleomagnetism of Siluro-Devonian sequences, NE Spain

Tait, J. A., V. Bachtadse, and J. Dinares-Turell (2000), Paleomagnetism of Siluro-Devonian sequences, NE Spain, Journal of Geophysical Research-Solid Earth, 105(B10), 23595-23603, doi:10.1029/2000JB900111.

The paleogeography of northeastern Spain is addressed in a detailed paleomagnetic study of Siluro-Devonian boundary sediments from the Catalan Coastal Ranges (CCR) at Santa Creu d'Olorda, Barcelona, and the eastern Pyrenees at Baen. The sequences studied are all well dated biostratigraphically and have undergone only very minor deformation, mainly during the late Carboniferous, and extremely lour grades of metamorphism (anchizone or less). After stepwise thermal demagnetisation of samples and principal component analysis of the data, up to two paleomagnetic directions can be clearly identified after removal of a present-day magnetic overprint. The first component (labeled B) is identified only in samples from the CCR with intermediate unblocking temperature spectra (300 degrees-400 degrees C). An overall mean direction of 187 degrees/-03 degrees, semi angle of cone of 95% confidence alpha(95)=9.0 degrees, and precision parameter k= 43.1 in situ, and 195 degrees/03 degrees alpha(95)=24.4 degrees, and k= 7.1 (51 samples at seven sites) after bedding correction is obtained for B. The exact age of this secondary component is uncertain, but when compared to published paleomagnetic data, a late Carboniferous to Early Triassic age could be inferred. A stable endpoint direction (labeled C) can be identified between 400 degrees and 600 degrees C in samples from both regions. For the CCR it is southwesterly directed with intermediate inclination values in situ, and yields a mean direction of 208 degrees/48 degrees, alpha(95)=12.8 degrees and k=28.4 (six sites) after bedding correction. It passes the fold test, is considered to be primary in origin, and is thus indicative of the Siluro-Devonian paleofield direction in the CCR. In the Pyrenean samples the C direction is northwesterly directed in situ, with a mean direction of 240 degrees/51 degrees, alpha(95)=6.5 degrees and k=86.5 (seven sites) after bedding correction. Although there is a clear improvement in grouping of these site mean directions, this is not significant at the 95% level of confidence. Combining the site mean directions obtained for component C from both regions yields an overall mean direction of 224 degrees/51 degrees, alpha(95)=8.5 degrees and k=24.6 (13 sites) after bedding correction. The improvement in grouping is significant at the 99% level of confidence at 90% unfolding, reinforcing the interpretation that this is a primary magnetisation. Adopting the reversed polarity option, the inclination value obtained translates into paleolatitudes of 30 degrees S, placing NE Spain in the same latitudinal belt as the Armorican Massif and the Barrandian terrane of the Bohemian Massif(i.e., the Armorican Terrane Assemblage) in latest Silurian/earliest Devonian times.
  author = {J. A. Tait and V. Bachtadse and J. Dinares-Turell},
  journal = {Journal of Geophysical Research-Solid Earth},
  number = {B10},
  pages = {23595-23603},
  title = {{Paleomagnetism of Siluro-Devonian sequences, NE Spain}},
  volume = {105},
  year = {2000},
  language = {en},
  doi = {10.1029/2000JB900111},
%0 Journal Article
%A Tait, J. A.
%A Bachtadse, V.
%A Dinares-Turell, J.
%D 2000
%N B10
%V 105
%J Journal of Geophysical Research-Solid Earth
%P 23595-23603
%T Paleomagnetism of Siluro-Devonian sequences, NE Spain
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