PALEOPRODUCTIVITY FOLLOWING THE PERMIAN-TRIASSIC MASS EXTINCTION IN THE WESTERN CANADA SEDIMENTARY BASIN: RAPID RECOVERY OR PROLONGED SLUMP?

Examination of the period following the Permian-Triassic mass extinction has revealed a complex and stressed post-extinction interval. Many studies have documented the recovery of individual taxa, however, little work has focused on the reestablishment of primary productivity, an important step along the path to recovery. Productivity estimates following the Permian-Triassic mass extinction are currently limited to d13Corg records near the P/T boundary, which suggest that productivity recovered rapidly (within 50-100 ka), and low-resolution, stage-level comparisons of chert and phosphorite abundances, which are thought to document an extended Early Triassic productivity slump. Overall, this dichotomy implies that while productivity recovered rapidly, it did not stabilize. In order to gain a clearer picture of temporal and spatial trends in productivity following the Permian-Triassic crisis, samples were collected from multiple stratigraphic sections from the laterally-extensive Western Canada Sedimentary Basin, which stretches nearly 1000 km along the BC – AB border. Geochemical proxies in the form of major, minor, and trace element data have been collected from two localities within the WCSB: from Cadomin, west-central AB and Opal Creek, southwestern AB. This data was combined with outcrop and petrographic observations in order to determine paleoproductivity, paleoenvironmental conditions, and sedimentologic characteristics. Results from both localities indicate that paleoproductivity was decimated at the P/T boundary, but returned quickly in the early Griesbachian. Paleoproductivity remained robust at the Opal Creek locality through the top of the section, while anoxic conditions disappeared near the Dienerian-Smithian boundary. Paleoproductivity covaries positively with paleoxygenation at the Cadomin locality following the early Griesbachian, suggesting that paleoxygenation was related to regional productivity and organic input. Differences in paleoproductivity and paleoxygenation between the two localities is likely due to local paleobathymetric or paleoceanographic variability; future analyses from additional localities across the WCSB should provide a more precise picture of when, how, and where productivity returned following the Permian-Triassic crisis.