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- Rehnström, Emma, et al.
(author)
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Cambrian sediments and Proterozoic granites in the Dividalen-Tometrdsk area, northern Scandinavia: Palaeomagnetism and U-Pb geochronology
- 2003
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In: GFF. - 2000-0863. ; 125:3, s. 131-138
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Journal article (peer-reviewed)abstract
- New palaeomagnetic data from the autochthonous Early Cambrian Dividal Group (northern Scandinavia) confirm earlier findings, and a refined palaeomagnetic pole of 58.4degreesN and 122.5degreesE, places Baltica at intermediate southerly latitudes at similar to535 Ma. Palaeomagnetic data from the immediately underlying granitic basement (pole: 9.8degreesN, 226.7degreesE) differ markedly from the Dividal sediments. The result of this fieldtest increases the palaeomagnetic reliability of the Dividal Group results. We dated the granitic basement in the eastern part of the Tornetrask area (corresponding to our palaeomagnetic site) to 1786+/-4 Ma (U-Pb zircon and titanite), whilst deformed allochthonous granites west of lake Tornetrask are slightly older (1800+/-4 Ma; U-Pb zircon). These ages are compatible with autochthonous basement ages to the east of the study area, but also with ages from basement windows to the west. Preliminary palaeomagnetic data from the 1786+/-4 Ma granitic basement are clearly pre-Phanerozoic in origin, and comparable and concordant zircon and titanite ages may hint that the magnetisation could be primary. However, the palaeomagnetic pole does not match contemporaneous poles from Baltica, which suggest a tectonic explanation (no palaeohorizontal control), a problem of secular variation (only one site) or a younger but pre-Phanerozoic remagnetisation event, which did not affect the U-Pb system in zircon and titanite.
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| 3. |
- Roberts, RJ, et al.
(author)
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The Early Carboniferous Mageroy dykes, northern Norway: palaeomagnetism and palaeogeography
- 2003
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In: Geological Magazine. - 0016-7568. ; 140:4, s. 443-451
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Journal article (peer-reviewed)abstract
- Palaeomagnetic data from the 337 Ma Mageroy dykes (northern Norway) are of exceptionally high quality, and a positive contact test along with an existing regional result from the Silurian Honningsvag Igneous Suite attests to a primary Early Carboniferous magnetic signature. The palaeomagnetic pole (S 14.8degrees, E320.1degrees, dp/dm = 4.4/8.6degrees) is the first Early Carboniferous pole from Baltica, and implies that northernmost Norway-Greenland, the Barents Sea and Svalbard were located at tropical to low northerly latitudes at this time. Northward drift during Carboniferous times (5-6 cm/yr) as demonstrated from palaeomagnetic data is also reflected in the sedimentary facies in the Barents Sea realm, that is, a change from tropical (Early Carboniferous) to subtropical (20-30degrees N) carbonates and evaporites in the Late Carboniferous. The Mageroy dykes are continental tholeiites which intruded into a set of NW-SE-trending normal faults parallel to the Trollfjorden-Komagelva Fault Zone and the Mageroysundet Fault immediately to the north and south of Mageroya, respectively. These, and many other NW-SE-trending faults (onshore and offshore), were active during Late Palaeozoic extension, and the dykes were probably contemporaneous with the earliest syn-rift sedimentation in the Barents Sea (for example, the Nordkapp Basin).
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