The Role of Volcanism (North Atlantic Igneous Province) in the PETM Events Revealed by Mercury Anomalies

The Paleocene-Eocene Thermal Maximum (PETM, ≈55.8±0.2 Ma) is marked by a global change in carbon cycle and rapid warming. Climate warming persisted for several tens of thousands of years and resulted in rapid diversification in terrestrial mammals and marine planktic foraminifera.

Deep-water benthic foraminifera suffered a mass extinction (≈40% species) but no significant extinctions occurred shallow shelf environments. Benthic extinctions are commonly explained as the effects of the initial stage of climate warming due to North Atlantic Volcanic Province volcanism (NAVP), which triggered methane release from ocean sediments causing global warming and ocean acidification. But the relationship between NAPV and the PETM events are till now not clearly demonstrated.

Several studies demonstrated the relationship between Hg anomalies in sediments and LIP activity associated with mass extinctions. Mercury (Hg) content of several sections located in different sedimentary environments (deep bathyal: Zumaya, Trabakua, N-Spain and outer shelf: Dababiya GSSP, Duwi, Wadi Nukhul, Egypt, terrestrial: Esplugafreda) were determined. At Zumaya the PETM is marked by a red clayey and marly interval poor in organic matter and coincident with a pronounced δ13C negative shift. A comparable clay interval with low TOC content is also present in the Dababyia section in the lower part of the negative δ13C shift, whereas the upper part of is enriched in TOC, reflecting increased productivity. The Esplugafreda section located in South Central Pyrenees shows an excellent terrestrial record of the early Eocene warm events. High-resolution δ13C and δ18O analyses of two types of calcareous paleosoil nodules reveal two distinct negative excursions a Pre-Onset Excursion (POE) and the Paleocene Eocene Thermal Maximum (PETM), both characterized by significant Hg enrichments.

This Hg enrichment is not linked to clays or total organic carbon contents, and suggests that Hg anomaly resulted from higher atmospheric Hg input into the marine realm, rather than organic matter scavenging and/or increased run-off.

The presence of several peaks of mercury coincident with both POE and PETM intervals supports the role of volcanism (North Atlantic Igneous Province) to initiate the concomitant warming and sea-level rise characterizing the POE and PETM.