EVALUATING REDOX CONDITIONS DURING THE CAMBRIAN SPICE EVENT, WESTERN NEWFOUNDLAND, CANADA

The Steptoean Positive Isotopic Carbon Excursion, or SPICE event, involved a global shift in carbon isotope values that corresponded to an extinction of trilobites in later Cambrian oceans. While this excursion has been found globally, the mechanism(s) that drove this excursion remain unconfirmed. In the Port au Port Group of western Newfoundland, the SPICE event is preserved in a series of fault blocks along the south facing shore of the Port au Port Peninsula. Recent analysis of the SPICE event in western Newfoundland shows that the carbon isotope excursion is accompanied by small mercury enrichments. In both the initial mercury measurements and in mercury normalized to total organic carbon, our data show elevated mercury concentrations before and after the SPICE but a return to baseline during the excursion. We coupled the carbon isotope and mercury data with XRD analyses of insoluble residues and show that the presence of glauconite and berthierine/chamosite corresponds to intervals of mercury enrichments. The presence of these redox sensitive minerals with mercury enrichments suggest that the SPICE in Newfoundland preserves a record of changing oxygen conditions during its onset and in its aftermath. This study contributes to a larger, global effort to identify and analyze SPICE sections while considering the hypothesis that mercury may act as a local redox indicator.