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

Mina Mazaheri-Johari,Daoliang Chu,Joost Frieling,Piero Gianolla,Jacopo Dal Corso,Tamsin A Mather

doi:10.1038/s41598-021-96890-8

Mina Mazaheri-Johari, Daoliang Chu + Show 4 more

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https://doi.org/10.1038/s41598-021-96890-8

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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.

Highlights

The Carnian Pluvial Episode (CPE, Late Triassic) was an interval of global warming and enhanced hydrological cycle coupled to extinctions and major radiations among terrestrial and marine taxa, giving rise to new modernstyle ecosystems[1,2,3,4,5,6,7,8,9,10,11]
The average Hg concentration (29 ppb) in the Carnian rocks of the Western Tethys is lower than that measured in some modern sediments[33] and in clastic rocks covering other Phanerozoic events linked to major volcanic activity[28], but is closer to the average Hg concentrations found in limestones across the same Phanerozoic e vents[28]
Muted compared to other examples in the geological record, these pulses occur in correspondence to negative C-isotope excursions (NCIEs) and we note that the Hg/total organic carbon (TOC) record is different in different basins

Summary

Introduction

The Carnian Pluvial Episode (CPE, Late Triassic) was an interval of global warming and enhanced hydrological cycle coupled to extinctions and major radiations among terrestrial and marine taxa, giving rise to new modernstyle ecosystems[1,2,3,4,5,6,7,8,9,10,11]. We analysed Hg and total organic carbon (TOC) concentrations in four Carnian marine sedimentary sequences of the Western Tethys to evaluate whether enhanced Hg loading and volcanic activity coincided with the C-cycle and hydrological perturbations across the CPE. The succession encompasses the Predil Limestone, the Rio del Lago Formation, the Conzen Formation, and part of the Tor Formation (Trachyceras–A. austriacum zones = Julian 1–2)[8,32]. In the Northern Calcareous Alps (Austria), we analyzed 62 samples from Steinbach and Polzberg sections[7,19], encompassing the Reifling Formation, the Göstling Member and the Reingraben Formation (Trachyceras–A. austriacum zone = Julian 1–2). A detailed description of the studied successions is in the Supplementary Information

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