A major sea-level drop briefly precedes the Toarcian oceanic anoxic event: implication for Early Jurassic climate and carbon cycle

Abstract

Abstract Sea-level change is an important parameter controlling the expansion of oxygen-depleted conditions in neritic settings during oceanic anoxic events (OAEs). Despite this fundamental role, it remains on a short timescale (50 m) and short duration of the forced regression suggests that it was most likely related to the transient waxing and waning of polar ice sheet. We suggest that this short-lived glaciation might have a genetic link with the inception of the Toarcian OAE. Indeed, during the deglaciation and the accompanying sea-level rise, the thawing permafrost may have released important quantities of methane into the atmosphere that would have contributed to the Toarcian OAE rapid warming and its characteristic negative carbon isotope excursion. This study offers a hypothesis on how some hyperthermal events might be rooted in short-lived “cold-snap” episodes.