Pairing geochemistry and sedimentology: an evaluation of Alberta’s earliest Triassic deposits and the proxies used to study them

Abstract

The end-Permian mass extinction, 250 million years ago, was the largest in Earth’s history, with estimates of faunal species loss up to ~90%. Western Canada plays host to deposits spanning the Permian-Triassic boundary (the Belloy and Montney Formations) allowing for the paleoenvironmental conditions surrounding post-extinction recovery to be evaluated. Utilizing both geochemical methods, such as trace element proxies and carbon isotopes, as well as sedimentology, this thesis has four aims: 1) evaluate the main mechanism facilitating the existence of marine refugia post-extinction, 2) determine if Siberian Trap volcanism was a factor in the delayed faunal recovery in the Early Triassic, 3) ascertain if the geochemical signatures of events within the Early Triassic can be used to correlate deposits across the basin and 4) examine the reliability of the geochemical proxies used to ascertain paleoenvironmental conditions. This thesis demonstrates that, following the end-Permian mass extinction, biotic recovery was facilitated by the monsoon cycle which produced coastal upwelling via Ekman transport and nutrient-rich runoff from increased rainfall. Additionally demonstrated, through the detailed evaluation of trace element proxies, is the subsequent eruption of the Siberian Traps at the end of the Smithian, which resulted in a temperature increase of 10°C, enhanced continental weathering, and a 0.55 unit decrease in seawater pH which resulted in ocean acidification and anoxia. These signatures are correlated, using chemostratigraphy, across the Western Canada Sedimentary Basin, dividing Early Triassic deposits into 13 chemostratigraphic packages. Lastly, by examining the interaction of cyanobacteria and clay during flocculation, this thesis suggests that the geochemical signatures of fine-grained deposits, such as the Triassic Montney Formation, can be altered by biological activity within the water column, in addition to seawater composition and redox state.