DO SEDIMENTARY MERCURY ANOMALIES REFLECT MASSIVE VOLCANISM? A GLOBAL COMPILATION OF MERCURY CONTENTS ACROSS THE PLIENSBACHIAN-TOARCIAN (EARLY JURASSIC)

The most common interpretation of ancient sedimentary mercury (Hg) anomalies is volcanogenic outgassing as a primary source. Thus, many studies have associated ancient Hg enrichments, normalized to total organic carbon, with volcanic activity, environmental change, and subsequent biological turnover and mass extinctions. The Hg proxy has been applied to the “Big 5” mass extinction events and Mesozoic oceanic anoxic events (OAEs), all of which have shown enrichments. Recently, however, a compilation of Early Jurassic Toarcian OAE Hg data has suggested a relationship between Hg anomalies and proximity to land and local changes in redox. These locations, however, only represent a small portion of the Early Jurassic global oceans. Therefore, we will extend these datasets to other locations around the world in order to improve our understanding of the Toarcian Hg record.

We will present Hg data from sites in northern Africa and Japan, representing the southern extent of the European epeiric seaway and western Panthalassa, respectively. The Moroccan samples come from the Talghemt succession, which spans the Pliensbachian/Toarcian boundary. It represents a sedimentary basin with relatively high accumulation rates and siliciclastic dilution. The Japanese samples come from the Sakuraguchi-dani succession, which spans the Pliensbachian/Toarcian boundary and includes the Toarcian OAE interval. Sedimentological and geochemical evidence from this site suggests significant variations in the contribution of detrital materials, as well as redox variations, during the classic T-OAE interval. This Early Jurassic Hg compilation will consist of 14 sites that span five continents, which will greatly improve our understanding of Hg cycling across an ancient interval of major environmental and biological disturbances.