Mercury and sulfur isotopic evidence for the linkages between the ca. 510 Ma Kalkarindji large igneous province and trilobite crisis

The first major mass extinction of trilobites occurred at the transition from Cambrian Series 2 (CS2) to Miaolingian (M) and coincided with a large marine transgression volcanic eruptions igneous province (LIP). Understanding causal links between these events is important in deciphering environmental changes life evolution that time. This paper presents S-Hg-C isotopic Fe speciation data for calcareous shales CS2-M Yangliugang Formation Dongjin section, South China. In lower part this section (Interval I), have limited S differences carbonate-associated sulfates (δ34SCAS) pyrites (δ34SPy) Δ34S values –4.2‰ +8.3‰; they also high FeHR/FeT ratios 0.5 0.66, are indicative low SO42− content anoxic seawater. Calcareous Interval I display least two Hg/TOC peaks (up 207 ppb/wt%), coincident associated ca. 510 Ma Kalkarindji LIP Australia. middle II), negative excursions Δ199Hg values, δ34SPy ratios, which were likely led by terrestrial input into marginal basin where II deposited. upper III) contain pyrite framboids mean diameter <4 μm (>0.82) FePy/FeHR (>0.78), indicating an euxinic depositional environment. They record δ13C δ202Hg (with down –3.05‰ –1.68‰, respectively), providing evidence ocean upwelling. shift was temporally comparable C isotope Redlichiid-Olenellid Extinction Carbon Isotope Excursion (ROECE). We conclude enhanced continental erosion rate, leading accumulation H2S deep basins end CS2. subsequent upwelling (>506 Ma) brought anoxic/euxinic seawaters shelf, contributing Redlichiid Olenellid.