Abstract

Contrary to a long-held belief, Upper Permian strata are present in the Sverdrup Basin of Arctic Canada, and a nearly continuous conformable record with the overlying Blind Fiord Formation occurs in the basin central area. Upper Permian strata are dominated by spiculitic chert, the bulk of which is part of a Wuchiapingian unconformity-bounded transgressive-regressive sequence, one of four sequences that encompass the Middle Permian to Lower Triassic interval. Two new stratigraphic units are here formally erected to better account for Upper Permian strata in the Sverdrup Basin. The Lindström Formation is a unit of white to pale grey spiculitic chert that represents sedimentation on a shallow, open marine, wave- and storm-dominated ramp. The Black Stripe Formation, which is in part correlative with the Lindström Formation, comprises black to dark grey spiculitic chert associated with siliceous shale and siltstone of slope to basinal origin. The upper part of the Black Stripe Formation comprises a deepening-upward succession of black cherty siltstone and siliceous shale that recorded Changhsingian sedimentation. The basal Blind Fiord contact which coincides with the Latest Permian Extinction event in the Sverdrup Basin is marked by an unusual abundance of pyrite, a hallmark of the extinction horizon around the world. A hiatus associated with maximum flooding and condensation exist across the Black Stripe-Blind Fiord contact in distal settings. However, a seemingly rapid, yet progressive carbon isotopic shift suggests minimal stratigraphic interruption. The Late Permian age of the Lindström and Black Stripe formations is substantiated by conodont biostratigraphy and carbon isotope chemostratigraphy. Late Changhsingian conodonts were recovered from the base of the Blind Fiord Formation, while Hindeodus parvus, the species that marks the base of the Triassic at the GSSP in China, and associated conodont assemblages, occurs a few tens of metres above the base of the Blind Fiord Formation. Black shale in the Lindström and correlative Black Stripe Formation may have a source potential as shown by high TOC values and preliminary RockEval analysis.

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