Paleomagnetic reconnaissance of early Mesozoic carbonates from Williston Lake, northeastern British Columbia, Canada: evidence for late Mesozoic remagnetization

Abstract

Three classic sections of Middle and Late Triassic fossiliferous limestones cropping out around Williston Lake in British Columbia, Canada, were sampled for paleomagnetic study. The objective was to test the suitability of these units for detailed magnetobiostratigraphic study with the aim of improving the reference Triassic geomagnetic polarity time scale. The Williston Lake characteristic magnetizations differ, however, from any Triassic North America cratonic reference directions. A satisfactory agreement is found instead with Cretaceous -early Cenozoic North America cratonic reference directions. The exclusive occurrence of normal polarity suggests that remagnetization likely occurred during the Cretaceous long normal superchron. Remagnetizations may have been triggered by connate brines, which moved along aquifers of porous sandstones and carbonates in the early stages of Laramide folding.Résumé : Trois sections fossilifères classiques de calcaires (Trias moyen et tardif), affleurant autour du lac Williston en Colombie Britannique, ont été échantillonnées pour une étude paléomagnétique. L'objectif était de s'assurer de la pertinence de ces unités pour une étude magnéto-bio-stratigraphique détaillée visant à améliorer l'échelle référentielle de temps de la polarité géomagnétique au Trias. Les magnétisations caractéristiques du lac Williston diffèrent toutefois de toute direction cratonique référentielle au Trias en Amérique du Nord. Toutefois, une corrélation satisfaisante est établie avec les directions cratoniques référentielles du Crétacé-Cénozoïque précoce en Amérique du Nord. L'occurrence exclusive d'une polarité normale suggère qu'il y eut probablement une remagnétisation au cours du long superchron normal du Crétacé. Les remagnétisations peuvent avoir été déclenchées par des saumures connées qui se sont déplacées le long d'aquifères de grès et de carbonates poreux dans les premières phases du plissement Laramide. [Traduit par la Rédaction] 1168Muttoni et al. Geological settingTriassic rocks in the Rocky Mountains and Foothills of western Canada form a relatively thick, eastward-thinning Can.

Constraining the travels of a "suspect" terrane: Paleomagnetism and geobarometry of two Early Cretaceous igneous complexes in the Peninsular Ranges Batholith, California

“…Postdepositional remagnetization may be an even more important cause of discordant paleopoles because it is endemic to virtually all sedimentary rocks. This process utilizes connate or hydrothermal fl uids during burial to facilitate redox chemical reactions that remove existing magnetic minerals and/or generate new magnetic minerals in sedimentary rocks to reset their remanence directions (Muttoni et al, 2001;Moreau et al, 2005). In Baja California since the Late Jurassic, because of its location relative to stable North American paleopoles, remagnetization causes polewarddisplaced and clockwise-rotated paleopoles.…”

Eocene rotation of the Coast Plutonic Complex and Intermontane Belt: paleomagnetism of Eocene plutons along the Klondike Highway

“…Firstly, geologic evidence, such as known fault displacements, can only account for *1000 km of northward displacement (e.g., Gabrielse et al 2006), which is far less than the *2000 to *4000 km of post-mid-Cretaceous northward displacements often postulated (e.g., Beck 1980;Irving et al 1985Irving et al , 1996Wynne et al 1995;Johnston 2001;Housen et al 2003;Enkin 2006). Secondly, much of the paleomagnetic evidence for northward displacements of >2000 km comes from sedimentary strata that, unlike igneous rocks, are subject to inclination shallowing by compaction (Kodama 1997;Kodama and Ward 2001) and to easy remagnetization by interstitial meteoric and hydrothermal fluids (Oliver 1992;Symons et al 1999;Enkin et al 2000;Muttoni et al 2001). Both mechanisms, because of the orientation of the APWP relative to the Cordillera, lead to an overestimation of the amount of northward translation (Symons et al 2005).…”