EARLY TRIASSIC (DIENERIAN-SMITHIAN) PALEOPRODUCTIVITY AND PALEOENVIRONMENTAL CONDITIONS WITHIN THE NORTHERN WESTERN CANADA SEDIMENTARY BASIN, BRITISH COLUMBIA, CANADA

The biotic recovery from the Permian-Triassic mass extinction was a complex process whose timing and scope were strongly affected by environmental conditions. While multiple studies of macrofaunal trends have been conducted, the recovery of primary producers and their relationship to paleoenvironmental conditions is poorly understood. The Western Canada Sedimentary Basin (WCSB) is an ideal locality to examine temporal and spatial trends in paleoproductivity and paleoenvironmental conditions because it contains a complete sequence of Early Triassic sediments deposited in environments ranging from shoreface to basin. A drill core of the Montney Formation (A8-7-85-18w6) from the Pedigree-Ring Border-Kahntah River area, located in northwestern Alberta and northeastern British Columbia was examined to determine paleoproducitivity and paleoenvironmental conditions, specifically paleoxygenation, across the Dienerian-Smithian boundary. Approximately 75 samples were collected to determine major, minor, and trace element abundances using ICP-AES, while %TOC and %TIC were determined using the Loss on Ignition method.

Ba and Ni enrichment factors, coupled with TOC levels ranging from 2-4% indicate sustained primary productivity during deposition of the entire study interval. Paleoxygenation values, determined from V and Mo enrichment factors as well as V/ (V+Ni), vary with grain size, suggesting that sea level and the stochastic input of coarse-grained sands and oxygen by turbidity currents controlled the relative degree of benthic oxygenation. Overall, the results from the study interval suggest the Early Triassic was a time of sustained productivity in the WCSB. Anoxic conditions persisted in deeper offshore zones, limiting the geographic extent of the recovery from the Permian-Triassic mass extinction to shallower, wave-affected environments (i.e. the habitable zone). Future research from cores and outcrops throughout the WCSB will further establish the timing and shape of the recovery from the Permian-Triassic extinction along the northwestern margin of Pangea, and its relationship to paleoenvironmental conditions.