High mercury enrichments in sediments from the Baltic continent across the late Cambrian: Controls and implications

Abstract

The late Cambrian witnessed significant biological and environmental changes. However, the main triggers responsible for that formidable turnover remain largely unknown. This study investigates mercury (Hg) enrichments from the late Miaolingian to Furongian section in a unique Alum Shale drilled core obtained from southeast Sweden. Our results show that the background level of Hg is relatively high because of the presence of reducing conditions and continuous Hg supply from water mass. However, our most spectacular findings are the presence of four Hg anomalies. The most pronounced Hg anomalies are characterized by the high values in total Hg (~900 ppb) and Hg/TOC ratio (~80), as well as specific signatures of mass independent fractionation of Hg (MIFs; Δ199Hg, Δ201Hg, and Δ200Hg) that we attribute to volcanic-derived Hg. This Hg loading event occurred immediately after the globally recognized Steptoean Positive Carbon Isotope Excursion (SPICE) event and could be attributed to volcanic activities during that period.