AAPG Foundation 2019 Grants-in-Aid Projects

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Evaluating organic matter sulfurization as a mechanism of enhanced burial of organic matter across an Early Jurassic Oceanic Anoxic Event and implications for source rock deposition and quality

Abstract

Mudrocks with high organic carbon contents have been the focus of intensive study since they are key economic resources as potential hydrocarbon source rocks and unconventional reservoirs. A fundamental debate exists as to what mechanism exerts dominant control on the formation of such deposits: enhanced organic matter production or preservation. The Mesozoic is known to contain multiple instances of the widespread deposition of organic-rich mudrocks associated with the expansion of oceanic anoxia. However, organic matter preservation is not governed solely by anoxia and may be controlled by other factors. Sulfurization of organic matter 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 additional mechanism for organic matter preservation in anoxic environments. I aim to (1) examine the influence of organic matter sulfurization on organic matter burial across a known interval of expanded euxinia (the Toarcian Oceanic Anoxic Event of the Early Jurassic, ~183 Ma) and (2) investigate the influence of depositional setting and organic matter input on the relative importance of sulfurization as a preservation mechanism by examining the S:C ratio of organic matter preserved across a depositional transect in an euxinic Toarcian aged basin. The broader goal of this work is to determine whether sulfurization acts as a significant preservation mechanism of organic matter when widespread euxinia develops in the oceans and if so, then how this may influence source rock deposition and quality across oceanic anoxic events.