EVALUATING ORGANIC MATTER SULFURIZATION AS A MECHANISM OF ENHANCED BURIAL OF REDUCED CARBON AND SULFUR ACROSS THE TOARCIAN OCEANIC ANOXIC EVENT

Mudrocks with high organic carbon contents have been the focus of intensive study since they are key economic resources as well as frequently reflecting past intervals of extreme environmental change. In particular, the Mesozoic is known to contain multiple instances of the widespread deposition of organic-rich mudrocks that are associated with the expansion of oceanic anoxia called Oceanic Anoxic Events or OAEs. A fundamental debate exists as to what mechanism exerts dominant control on the formation of organic-rich mudrocks: enhanced organic matter production or preservation. However, organic matter preservation is not governed solely by anoxia and may be controlled by other factors. Organic matter sulfurization (OMS) is one such preservation mechanism that operates rapidly within euxinic environments (e.g. anoxic with free hydrogen sulfide). Therefore, it may act as a significant mechanism for organic matter preservation in anoxic environments.

Here we investigate OMS as a potential pathway of enhanced preservation of organic matter during an OAE. Specifically, we investigated this process across the Toarcian Oceanic Anoxic Event (T-OAE, ~183 Ma) of the Early Jurassic. We will present δ³⁴S_org and organic matter S:C ratio data from the event as recorded within three basins of the European epicontinental seaway: the Cleveland Basin (UK), the Paris Basin (Luxembourg), and the Southern German Basin (Switzerland). The data generated within these basins are used to evaluate the influence of OMS on organic matter burial across the T-OAE. The broader goal of this work is to determine whether sulfurization acts as a significant preservation mechanism of organic matter when widespread anoxia or euxinia develops in the oceans and if so, then how this may influence our understanding of carbon and sulfur cycling across oceanic anoxic events.