Thallium isotopes reveal protracted anoxia during the Toarcian (Early Jurassic) associated with volcanism, carbon burial, and mass extinction

• DOI: 10.1073/pnas.1803478115
• Publication Date: 2018-06-11T19:22:36Z
• Authors: Theodore R. Them; Benjamin C. Gill; Andrew H. Caruthers; Angela M. Gerhardt; Darren R. Gröcke; Timothy W. Lyons; Selva M. Marroquín; Sune G. Nielsen; João P. Trabucho ...; Jeremy D. Owens
• Keywords: Extinction (optical mineralogy); Carbon fibers; Thallium

For this study, we generated thallium (Tl) isotope records from two anoxic basins to track the earliest changes in global bottom water oxygen contents over Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma) of Early Jurassic. The T-OAE, like other Mesozoic OAEs, has been interpreted as an expansion marine depletion based on indirect methods such organic-rich facies, carbon excursions, and biological turnover. Our Tl data, however, reveal explicit evidence for earlier deoxygenation ocean water, some 600 ka before classically defined T-OAE. This antecedent occurs at Pliensbachian/Toarcian boundary is coeval with onset initial large igneous province (LIP) volcanism initiation a mass extinction. Thallium isotopes are also perturbed during T-OAE interval, by isotopes, reflecting second event that coincides acme elevated extinctions main phase LIP volcanism. suggests duration widespread waters was least 1 million years spanned early middle time. Thus, data more nuanced record its links change period climatic warming Earth's past highlight role evolution.