Paper No. 173-4
Presentation Time: 9:00 AM-6:30 PM
PALEOCEANOGRAPHIC CHANGES ACROSS THE PERMIAN-TRIASSIC INTERVAL ALONG THE NORTHWESTERN MARGIN OF PANGEA: A CASE STUDY FROM OPAL CREEK, ALBERTA, CANADA
Permian and Triassic rocks deposited along the northwestern margin of Pangea record long-term shifts in the paleoceaonography of eastern Panthalassa. Persistent upwelling occurred during the Permian that collapsed just prior to the Permian – Triassic mass extinction ~251 Ma (Beauchamp and Baud, 2002). Recovery was not immediate after the extinction, but was strongly influenced by environmental conditions. To understand the long-term paleoceanographic history of northwestern Pangea and its relationship to Permian upwelling, the mass extinction, and recovery, it is helpful to examine proxies related to productivity and oxygenation across the period. Located within the southern Canadian Rockies, the Opal Creek, AB section contains a nearly complete stratigraphic section of Lower Permian to Lower Triassic deep-water sediments deposited along the northwestern continental margin of Pangea, and is composed of three distinct formations, including the Lower Permian Johnston Canyon Formation, the Middle Permian Ranger Canyon Formation, and the Lower Triassic Sulphur Mountain Formation. To better understand the relationship between recovery and environmental conditions related to the extinction, productivity and marine oxygenation levels were reconstructed via major, minor, and trace element analysis of 137 previously collected samples. Preliminary productivity proxy data (Ba, Cu, Ni and Zn) show an increase in values across the Permian (Johnson Canyon) and are indicative of high primary productivity, followed by a rapid decline across the P/Tr boundary. Early Triassic productivity is weaker than that of the Permian, but shows modest recovery during deposition of the Griesbachian – Dienerian Phroso Siltstone Member and more robust productivity during deposition of the Smithian - Spathian Vega Siltstone Member (although values are still below that of the Permian). Paleoxygenation proxies (Mo and V) demonstrate oxic to suboxic conditions during the Permian; values peak just above the P/Tr boundary due to a euxinic event, followed by persistent suboxic to anoxic conditions for the remainder of the study section. The results of this study agree with those of Schoepfer et al. (2013) from the same section, and demonstrate continued weak productivity and reduced benthic oxygenation well into the Early Triassic.