Mercury deposition in Western Tethys during the Carnian Pluvial Episode (Late Triassic)

Abstract

The Late Triassic Carnian Pluvial Episode (CPE) was a time of biological turnover and environmental perturbations. Within the CPE interval, C-isotope and sedimentary records indicate multiple pulses of depleted carbon into the atmosphere–ocean system linked to discrete enhancements of the hydrological cycle. Data suggest a similar cascade of events to other extinctions, including being potentially driven by emplacement of a large igneous province (LIP). The age of the Wrangellia LIP overlaps that of the CPE, but a direct link between volcanism and the pulsed CPE remains elusive. We present sedimentary Hg concentrations from Western Tethys successions to investigate volcanic activity through the previously established CPE global negative C-isotope excursions (NCIEs). Higher Hg concentrations and Hg/TOC are recorded just before and during NCIEs and siliciclastic inputs. The depositional settings suggest volcanic Hg inputs into the basins over the NCIEs rather than increases of Hg drawdown or riverine transport. Differences in Hg and Hg/TOC signals between the basins might be linked to coeval LIP style or the temporal resolution of the sedimentary successions. Overall, our new data provide support for a link between pulses of Wrangellia LIP volcanism, NCIEs, and humid phases that mark the CPE in the Western Tethys.

Background Earth system state amplified Carnian (Late Triassic) environmental changes

“…The NCIEs indicate injections of isotopically light C into the atmosphere-ocean system, and are linked to global warming and biological changes, and are coeval to the emplacement of the Wrangellia LIP (Dal Corso et al, 2020a, 2012Sun et al, 2016;Tomimatsu et al, 2021). In the marine marginal successions of the Western Tethys and lacustrine series of North China (Jiyuan Basin), sedimentary Hg concentrations and Hg/TOC ratios increase in coincidence with the NCIEs that mark the CPE (Figure 2), supporting the hypothesis of four discrete injections of volcanic-related CO2 into the Carnian atmosphere-ocean system (Lu et al, 2021;Mazaheri-Johari et al, 2021).…”

“…Temperature changes that marked the Early-early Late Triassic are inferred from the conodont apatite  18 O record (Trotter et al, 2015). (Dal Corso et al, 2018;Mazaheri-Johari et al, 2021); North China (Lu et al, 2021); Devon, UK (Miller et al, 2017); Guizhou, China (Sun et al, 2016); Japan (Tomimatsu et al, 2021). (Donnadieu et al, 2006;Goddéris et al, 2014) interpolated onto a standard grid of CO2 concentrations (Mills et al, 2021).…”

Global diversity dynamics in the fossil record are regionally heterogeneous

“…This heterogeneity continues through the Carnian and may reflect the role of regionally unique macroecological influences on diversity along with the regionally variable quality of the fossil record. Sedimentological evidence for regionally synchronous environmental upheaval during the CPE is globally pervasive 28 , 39 , 40 and four distinct pulses of volcanism and carbon isotope excursion, linked to the eruption of the Wrangellia Large Igneous Province, can be identified with confidence during the CPE in both East 41 and West Circumtethys 42 . Only West Circumtethys, however, shows the signal of biotic crisis during the CPE, with strongly negative diversification rates and a sharp crash in diversity (Fig.…”

Late Permian to Late Triassic Large Igneous Provinces: Timing, Eruptive Style and Paleoenvironmental Perturbations

“…This is crucial as the Wrangellia has been tentatively linked to a period of significant climate changes and biological turnover during the Late Triassic, known as CPE (Dal Corso et al, 2020). The finding of four negative carbon isotope excursions (NCIEs) correlated with Hg spikes in sedimentary strata across the CPE suggest a volcanic origin for this event (Dal Corso et al, 2018Lu et al, 2021;Mazaheri-Johari et al, 2021). The duration of the CPE was inferred to be of ca.…”