@article{fdi:010053693,
  title = {{T}he similar to 270 {M}a palaeolatitude of {B}altica and its significance for {P}angea models},
  author = {{D}ominguez, {A}. {R}. and {V}an der {V}oo, {R}. and {T}orsvik, {T}. {H}. and {H}endriks, {B}. {W}. {H}. and {A}brajevitch, {A}. and {D}omeier, {M}. and {L}arsen, {B}. {T}. and {R}ousse, {S}onia},
  editor = {},
  language = {{ENG}},
  abstract = {{T}o better constrain {B}altica's position within {P}angea, we conducted a palaeomagnetic study of {P}ermo-{T}riassic dykes from the {O}slo {G}raben, as a follow-up to an initial, but rather limited, study by {T}orsvik and colleagues in 1998. {T}he age of these so-called {L}unner dykes had previously been determined as similar to 240 {M}a in that study, but details in their analyses and new {A}r-40/{A}r-39 ages reveal that there may have been some argon loss in the initially dated dyke minerals and that a combined (weighted mean) age of 271 +/- 2.7 (2 sigma) {M}yr for the dykes is preferable. {W}e find two major components of magnetization in our samples: one carried by an {F}e-sulphide (likely pyrrhotite) and the other carried by low-{T}i magnetite; these magnetization components may be found together (superposed) in a given sample or they may occur apart. {M}icronmetre-sized crystals of {T}i-{F}e oxides, observed with a scanning electron microscope ({SEM}) show exsolution lamellae, formed upon cooling from intrusion temperatures. {A}ssuming that the submicronmetre-sized ({T}i)-magnetite grains that carry a stable remanence are of the same generation as the observed larger grains, we interpret the magnetite remanence in the dykes as of primary, thermoremanent origin. {T}he sulphide remanence appears to be slightly younger, as seen by the {SEM} observations of pyrite framboids and a {F}e-sulphide grain invading a {T}i-magnetite grain. {M}oreover, the sulphide mineralization is likely of region-wide hydrothermal origin. {T}he magnetizations carried by the pyrrhotite and magnetite have nearly identical directions and so, must be nearly of the same age. {F}or this study, we sampled 56 sites including 39 dykes, 10 baked-contact rocks and 7 host rocks removed from the immediate dyke contacts. {T}he dykes and the contact rocks have the same {SW} and up directions of magnetization, and contain the {F}e-sulphide or the magnetite magnetization or both, as diagnosed by their relative unblocking temperatures. {H}owever, all the sampled carbonate and igneous host rocks far away from the dykes also have the same directions. {T}hus, all of the 10 originally planned contact tests are inconclusive. {T}he new palaeopoles of this study are a few degrees apart; the magnetite pole (from dykes only, {N} = 25) is located at 51 degrees {N}, 164 degrees {E}, {K} = 69, {A}(95) = 3.5 degrees, whereas the pole calculated from iron sulphide magnetic directions (all rock types, {N} = 20) is at 54 degrees {N}, 166 degrees {E}, {K} = 112, {A}(95) = 3.1 degrees. {A}ll directions are of reversed polarity, suggesting that the magnetization was acquired during the {K}iaman {R}eversed {S}uperchron. {T}he palaeomagnetic mean result from the magnetite-bearing sites implies a palaeolatitude of {O}slo of 23 degrees {N}, whereas the palaeolatitude calculated from the pyrrhotite magnetizations is 25-27 degrees {N}, depending on choice of host lithologies. {A}s noted in many previous publications, the palaeomagnetic poles for the late {P}alaeozoic and {E}arly-{M}iddle {T}riassic are in conflict with classical {P}angea reconstructions. {T}he poles with ages of 250 +/- 10 {M}a, in particular, previously showed a discrepancy of some 25 degrees or more, when the {G}ondwana and {L}aurussia continents are restored to their juxtapositions in the {P}angea-{A} fit, before the opening of the {A}tlantic {O}cean. {P}roposed solutions to this conundrum have been controversial, involving doubts about (1) the geocentric coaxial dipole field model, (2) the reliability of the palaeomagnetic results or their ages, or (3) the validity of the {P}angea-{A} reconstruction, leading to proposals of a {P}angea {B} reconstruction in which {G}ondwana is displaced some 3500 km to the east with respect to {L}aurussia. {T}he significance of our new result for this {P}angea controversy resides in its improved age within an early {G}uadelupian (mid to late {P}ermian) time interval where few results exist from well-dated igneous rocks in either {B}altica or {L}aurentia. {T}here are quite a few results from sedimentary rocks, but these may be suspected to suffer inclination shallowing, and are therefore less suitable to settle a palaeolatitudinal argument. {O}ur new result of the magnetite magnetization, granted it is primary and acquired at about 270 {M}a, combined with a new similar to 265 {M}a result from {A}rgentina and selected other poles from igneous rocks, leaves enough room for the north-south configuration of {P}angea {A} at 270 {M}a and avoids the overlap between {B}altica and {G}ondwana that necessitated {P}angea {B}, at least for the {L}ate {P}ermian.},
  keywords = {{P}alaeomagnetism applied to tectonics},
  booktitle = {},
  journal = {{G}eophysical {J}ournal {I}nternational},
  volume = {186},
  numero = {2},
  pages = {529--550},
  ISSN = {0956-540{X}},
  year = {2011},
  DOI = {10.1111/j.1365-246{X}.2011.05061.x},
  URL = {https://www.documentation.ird.fr/hor/fdi:010053693},
}