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

• Hg anomalies of the end-CS 2 sediments were caused by eruptions of the ca. 510 Ma LIP. • Volcanic eruptions led to a high terrestrial SO 4 2 − input into the end-CS 2 ocean. • Upwelling of euxinic waters was the direct cause for the ca. 506 MA trilobite crisis. The first major mass extinction of trilobites occurred at the transition from Cambrian Series 2 (CS 2) to Miaolingian (M) and coincided with a large marine transgression and volcanic eruptions of a large igneous province (LIP). Understanding the causal links between these events is important in deciphering environmental changes and life evolution at that time. This paper presents S-Hg-C isotopic and Fe speciation data for calcareous shales from the CS 2 -M Yangliugang Formation in the Dongjin section, South China. In the lower part of this section (Interval I), calcareous shales have limited S isotopic differences between carbonate-associated sulfates (δ 34 S CAS) and pyrites (δ 34 S Py) with Δ 34 S values from –4.2‰ to +8.3‰; they also have high Fe HR /Fe T ratios from 0.5 to 0.66, that are indicative of a low SO 4 2 − content in anoxic seawater. Calcareous shales from Interval I display at least two Hg/TOC peaks (up to 207 ppb/wt%), coincident with volcanic eruptions associated with the ca. 510 Ma Kalkarindji LIP in Australia. In the middle part of the Dongjin section (Interval II), calcareous shales display negative excursions of Δ 199 Hg values, δ 34 S Py values and Fe HR /Fe T ratios, which were likely led by a large terrestrial input into a marginal basin from where Interval II deposited. Calcareous shales in the upper part of the section (Interval III) contain pyrite framboids with a mean diameter of <4 μm and high ratios of Fe HR /Fe T (>0.82) and Fe Py /Fe HR (>0.78), indicating an euxinic depositional environment. They also record negative excursions in δ 13 C and δ 202 Hg (with low values down to –3.05‰ and –1.68‰, respectively), providing evidence for ocean upwelling. The negative shift of δ 13 C values in the Dongjin section was temporally comparable to the C isotope excursions that coincided with the Redlichiid-Olenellid Extinction Carbon Isotope Excursion (ROECE). We conclude that volcanic eruptions of the ca. 510 Ma Kalkarindji LIP enhanced the continental erosion rate, leading to a high terrestrial SO 4 2 − input and an accumulation of H 2 S in deep marginal basins at the end of CS 2. The subsequent ocean upwelling (>506 Ma) brought anoxic/euxinic seawaters into the continental shelf, contributing to the mass extinction of Redlichiid and Olenellid. [ABSTRACT FROM AUTHOR]