SEDIMENTARY MERCURY AS A PROXY FOR REDOX OSCILLATIONS DURING THE CAMBRIAN SPICE EVENT IN WESTERN NEWFOUNDLAND

The later Cambrian Steptoean Positive Isotopic Carbon Excursion (SPICE) event was a global shift in carbon isotope values associated with trilobite mass extinctions and Laurentian sea level change. Despite extensive research on SPICE sections around the world, a consensus on the cause of the excursion and its associated events has not yet been achieved. Here, we present a geochemical and mineralogical data set from an outcrop of the SPICE event exposed on the Port au Port Peninsula of western Newfoundland to investigate a possible connection between redox conditions and sedimentary mercury. We have detected small mercury enrichments before and after the SPICE peak which remain significant after normalization to both TOC and clay mineral abundance. XRD examination of insoluble residues has shown how mineral abundances of glauconite change throughout the section. Mercury enrichments prior to the SPICE peak are not accompanied by any changes in glauconite. During the SPICE peak, mercury and glauconite are both low. Elevated glauconite abundance accompanies mercury enrichments after the SPICE peak, suggesting that this interval experienced oscillating redox conditions. Our data from the Newfoundland sections demonstrate that mercury enrichments may indicate local redox changes, but caution must be used when enrichments are small overall (< 10 ppb).