808 / 2024-09-19 14:47:12

Mercury enrichments as a paleo-volcanism proxy: Sedimentary bias and a critical analysis across the end-Triassic

paleo-volcanism,Hg anomaly,end-Triassic mass extinction

Session 42 - Deep-time ocean and climate changes: insights from models and proxies

Mercury (Hg) anomalies in sedimentary rocks have been increasingly used in paleoclimatology studies for tracing volcanic signals, because Hg emissions from volcanic activity could cause contemporaneous sedimentary Hg enrichment. However, non-volcanic controls on Hg, such as host phase variability, facies changes and post-depositional preservation effects, can be significant. These factors can limit the efficacy of Hg as a volcanism proxy. In this study, the sedimentary effects on Hg concentration within a complex depositional system in southwest England have been analyzed. The studied section spans the end Triassic mass extinction (ETME) – a time of major volcanic activity owing to the contemporaneous emplacement of the Central Atlantic Magmatic Province (CAMP). Our statistical analysis of data through the section highlights significant fluctuations in sedimentary Hg due to relative supply differences in Hg and host phases, as well as the changing types and preservation conditions of host phases. Analysis of Hg data from other globally-distributed end-Triassic sections suggests a consistent undersupply of Hg relative to organic matter across the ETME. To better assess the magnitude and significance of possible Hg enrichments in sedimentary rocks, we present a novel statistical method for quantifying Hg anomalies to robustly distinguish Hg variations linked to host phase/depositional changes from paleo-volcanism. Our method supports the existence of transient but asynchronous Hg anomalies linked to volcanism from the CAMP across the end-Triassic in most global sections, albeit not in the St. Audrie’s Bay section.