PRIMARY PRODUCTIVITY DURING THE EARLY TRIASSIC BIOTIC RECOVERY IN THE WESTERN CANADA SEDIMENTARY BASIN AND ITS RELATIONSHIP TO PALEOENVIRONMENTAL CONDITIONS

Biotic recovery following the Permian-Triassic mass extinction and its relationship to environmental conditions has been extensively studied over the past 2 decades, while the recovery of primary producers, which is a critical element in any recovery, has received scant attention. Estimates of primary productivity following the Permian-Triassic mass extinction are contradictory, with d13Corg isotopes suggesting that primary productivity returned within 50-100 ka, while stage-level comparisons of chert and phosphorite abundances imply an extended productivity slump. These differing results suggest that while productivity may have returned quickly, it remained unstable. In order to gain a better perspective of when primary productivity returned from the Permian-Triassic mass extinction, and its relationship to paleoenvironmental conditions (specifically paleoxygenation), major, minor, and trace element data is being collected from multiple outcrops and cores from across the Western Canada Sedimentary Basin (WCSB), which stretches ~1000km along the BC – AB border. Data has been collected from each of the 3 subbasins that make up the WCSB (Opal Creek locality, Spray River Basin, southern AB; Cadomin locality, Peace River Basin, central AB; Pedigree-Ring Border-Kahntah River area cores, Liard Basin, northeastern BC). Results from Opal Creek and Cadomin demonstrate that productivity collapsed at the P/T boundary, but quickly recovered in the early Griesbachian. Paleoproductivity remained robust at the Opal Creek locality through the top of the section, while anoxic conditions receded near the Dienerian-Smithian boundary. Paleoproductivity covaries positively with paleoxygenation at the Cadomin locality following the early Griesbachian, suggesting that paleoxygenation may have been at least partially related to organic input. Analysis of samples from the Liard Basin have concentrated thus far on Smithian-aged rocks, and results indicate that productivity was robust across the interval, with shifts in paleoxygenation related to sea-level variations. Ongoing analyses from additional localities across the WCSB should further clarify productivity and paleoxygenation trends and their relationship to each other as well as macrofaunal trends during the post-extinction recovery interval.