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.

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