Abstract

Sedimentary facies analysis of Lower Triassic deltaic deposits tests a hypothesis that the Latest Permian Mass Extinction influenced sedimentation in the Sverdrup Basin. The pre-existing stratigraphic framework subdivides the Blind Fiord and Bjorne formations into three T-R sequences and component braid-deltaic successions. As described here, river-dominated deltaic facies of the first sequence are indicative of high-magnitude flood flows resulting in a predominance of upper flow regime sedimentary structures. River-dominated deltaic facies of the second sequence contain fewer upper flow regime structures recording lower energy flows that generated mostly 3D and 2D dunes. The third sequence marks the furthest progradation of the braid-delta into the basin.Beyond the gross braided stream characteristics of the three river-dominated deltaic successions, the lower two provide a compelling comparison of depositional environments because they formed in the same basin within only a few millions years and thereby were probably subject to similar boundary conditions. The Latest Permian Mass Extinction occurred near the base of the lower sequence containing flood-dominated deltaic facies. We propose that the lower, Induan, sequence is dominated by upper-flow regime plane beds due to the effect of the Latest Permian Mass Extinction on vegetative cover, whereas the middle sequence is dominated by dune-scale cross-stratification formed by lower magnitude, less flood-type flows during the Olenekian.

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