Jurassic location of the Yukon-Tanana terrane from palaeomagnetism of the folded Mississippian Tatlmain batholith and Ragged stock

SUMMARY The extensive Yukon-Tanana terrane (YTT) of the northern Canadian Cordillera has been considered controversially to be part of the allochthonous ‘Baja BC’ microcontinent or of the para-autochthonous North American cratonic margin during the Mesozoic. Palaeomagnetic methods have isolated a ve...

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Veröffentlicht in:Geophysical journal international 2019-12, Vol.219 (3), p.1660-1678
Hauptverfasser: Symons, D T A, Kawasaki, K
Format: Artikel
Sprache:eng
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Zusammenfassung:SUMMARY The extensive Yukon-Tanana terrane (YTT) of the northern Canadian Cordillera has been considered controversially to be part of the allochthonous ‘Baja BC’ microcontinent or of the para-autochthonous North American cratonic margin during the Mesozoic. Palaeomagnetic methods have isolated a very-stable Early Jurassic thermochemical remanent remagnetization in the terrane's felsic Tatlmain batholith and mafic Ragged stock after correction for: (1) rotation from northeast-plunging anticlinal deformation, (2) northerly dipping tectonic tilt of the host rocks and (3) northwestward regional translation on the adjacent Tintina transcurrent fault zone. The resulting 196 ± 6 Ma Tatlmain and Ragged palaeopoles are 64.9°N, 44.8°E (A95 = 5.9°) and 64.2°N, 58.5°E (A95 = 7.7°), respectively. The YTT palaeopoles support para-autochthonous tectonic models that have the YTT: (1) accreting to North America by the Early Jurassic, (2) undergoing non-significant orogen-perpendicular shortening by mid-Early Cretaceous from thrust-faulting, and, then (3) undergoing significant orogen-parallel northward translation of ∼500 km from mid-Early Cretaceous to the Eocene. In contrast, the palaeopoles for Stikinia and Quesnellia of the Intermontane Belt show progressive northwestward translation relative to North America by ∼1000 km and a rotation of ∼55° cw since mid-Early Cretaceous. We speculate that ∼500 km of the northward translation is related to dextral motion on the Tintina and Northern Rocky Mountain Trench fault in British Columbia, and that the clockwise rotation is related to upper crustal tectonics in both Yukon and southern British Columbia.
ISSN:0956-540X
1365-246X
DOI:10.1093/gji/ggz318