--> --> Dynamic anoxia and organic enrichment in the Western Interior Seaway during the Cenomanian-Turonian

AAPG Foundation 2019 Grants-in-Aid Projects

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Dynamic anoxia and organic enrichment in the Western Interior Seaway during the Cenomanian-Turonian

Abstract

The Cretaceous Western Interior Seaway is a highly productive hydrocarbon basin situated in the United States, Canada, and Mexico. Despite decades of research, however, the mechanisms that drive organic enrichment, and hence source rock presence, are not fully understood. The interplay of climate, eustasy and tectonics within this shallow epicontinental basin significantly affected ocean dynamics, intermittently allowing the mix of cold, oxygen-rich Boreal waters from the north and the warm, oxygen-poor, saline Tethyan waters from the south. Levels of anoxia fluctuated accordingly, and therefore some organic-rich layers reflect regional events rather than global Oceanic Anoxic Events (OAEs). This project will focus on Cenomanian-Turonian age sediments deposited during OAE-2, located along an E-W transect from Arizona to Kansas. Lipid biomarkers and their isotopic composition will be used to study the physical and biogeochemical evolution during the mid-Cretaceous by reconstructing variations in water column oxygenation, stratification, sea surface temperatures and organic matter provenance. In addition, analyses of neodymium isotopes will play a critical role in ascertaining the influence of differing water masses, informing our interpretations as to what is driving the changes observed in biomarker data. This study of the Cretaceous Western Interior Seaway not only allows more accurate prediction of organic-rich facies within the basin itself, but also facilitates greater understanding of organic matter deposition in epicontinental settings during both regional and global OAEs.