ABSTRACT Recently, a set of mercury (Hg) anomalies in Valanginian sediments recovered from European sections demonstrated that an important magmatic pulse occurred at the onset of the Weissert episode. In this study, we report the distribution of Hg contents near the onset of the Weissert episode from localities outside of Europe, in the proto–Atlantic Ocean (Blake Bahama and Cap Hatteras Basins, Deep Sea Drilling Project [DSDP] Holes 534A and 603B) and southern Tethys Ocean (Argo Abyssal Plain, Ocean Drilling Program [ODP] Hole 765C), in order to evaluate the global impact of volcanism during the Valanginian. In addition, we also reinvestigated the Orpierre and Angles sections of the Vocontian Basin at a very high time resolution, to examine the potential impact of regional volcanic activity during that time interval. The onset of the Weissert episode in the proto-Atlantic and in the southern Tethyan cores is marked by significant increases in Hg contents. The persistence of the Hg anomaly in Hg/total organic carbon and Hg/Al ratios suggests that Hg enrichments were not primarily controlled by runoff processes and/or redox conditions, but instead indicate an increase in volcanic activity. The Hg enrichments recorded from localities outside of Europe at different latitudes were correlated to those previously observed in European sections, thereby confirming the presence of a global Hg peak at the onset of the Weissert episode. This peak was probably related to the emplacement of the Paraná-Etendeka large igneous province, suggesting a key role for volcanic activity during the Valanginian global environmental perturbations. In coeval intervals in the Vocontian Basin, Hg records show abrupt and short-lived enrichments, which correspond in the sedimentary successions to a goethite-rich ocher-colored layer. Two regional processes could explain Hg deposition and sequestration in this region: increased Hg sequestration by organic matter production in an oxygen-depleted environment, and/or the presence of regional volcanic activity, which is also indicated by the occurrence of a distal volcanic ash layer.

Abstract Name: Eastern Helvetic platform Authors: Hanspeter Funk, Karl B. Föllmi, and Hans Mohr Location: From 46° 40' to 47° 20' north latitude and 8° 40' to 9° 40' east longitude, Helvetic Alps, eastern Switzerland Geologic time interval: Late Tithonian–early Albian Tectonic-sedimentary setting: Northern Tethyan passive margin Basin type: Epeiric Paleoclimate: Mainly subtropical, varying humidity, with some cooler intervals Platform type: Open shelf carbonate platform, homoclinal ramp type Platform geometry: Minimum platform length is about 1500 km; width may surpass 100 km in several parts of the margin. Platform thicknesses are variable, with maximum platform thickness exceeding 1 km. Facies and fossils: Fine- to coarse-grained carbonates, mudstones, claystones, and marlstones; glauconitic, siliciclastic, and phosphatic sediments; calpionellids, orbitolinids, corals, rudists, ammonoids, and echinoderms. Systems tracts: Transitional, tidal flat, lagoonal, open platform, platform margin, slope, basin Stacking patterns: Succession of shallowing and drowning phases with short intervals of subaerial exposure