UNDERSTANDING BIOGEOCHEMICAL LINKAGES ACROSS A CRETACEOUS TERRESTRIAL-MARINE INTERFACE

Understanding how paleoenvironments and biogeochemical cycles operate in response to local sea-level fluctuations at a time when climatic conditions were warmer and CO₂ was higher than today can help contextualize how the Earth will respond to future warming and sea-level rise.

The Cretaceous Western Interior Basin of North America is characterized by extensive carbon burial in both terrestrial and marine realms as well as large fluctuations in sea level. Studying the Western Interior Basin can provide insight about the long-term impact that sea-level driven perturbations have on carbon and nutrient cycles and potentially help resolve why carbon accumulations within the basin are spatially and temporally variable throughout the basin.

The Turonian-Coniacian Straight Cliffs Formation of Utah is an ideal study site to investigate the relationship between sea-level and carbon cycling, as it provides an opportunity to observe the transport and delivery of organic matter (OM) across a terrestrial-marine margin. Samples were collected from two drill-cores that span the paleo-shoreline of the Western Interior Seaway (WIS) and record locations that oscillate between terrestrial (floodplain, fluvial, peat mires), transitional (estuarine), and marine (near-shore and offshore) depositional environments. These core locations allow us to observe changes in carbon and nutrient cycling and investigate controls within a pre-existing sequence stratigraphic framework that includes identified transgressive and highstand system tracts.

We will present bulk carbon and elemental geochemistry results from rocks originally deposited in all of these sedimentary facies to test the hypothesis that transgressive sequences led to more labile organic compounds and associated nutrients being lost from the terrestrial environments and leading to higher marine primary productivity in marginal marine settings.