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Local versus seaway-wide trends in deoxygenation in the Late Cretaceous Western Interior Seaway

Allyson Tessin, Claudia Schroeder-Adams, Khalifa Elderbak, Nathan D. Sheldon and Ingrid Hendy
Local versus seaway-wide trends in deoxygenation in the Late Cretaceous Western Interior Seaway
Geological Society of America Bulletin (November 2018) 131 (5-6): 1017-1030


The sedimentary record of the Late Cretaceous North American Western Interior Seaway (WIS) is characterized by periods of enhanced organic carbon burial, including an interval that has been identified as Oceanic Anoxic Event (OAE) 3. The timing and duration of this event has proved difficult to constrain, calling into question whether a widespread organic carbon burial event actually occurred. In order to evaluate the nature of OAE 3 better, different localities are studied within the WIS to investigate whether a single anoxic, carbon burial event exists within Upper Cretaceous strata above the global OAE 2. New trace metal and Fe speciation records from the Niobrara Formation within the Sweetgrass Arch region in southern Alberta, Canada, highlight that there were several intervals of deoxygenation. Comparison of these new results with similar records from the southern portion of the seaway (Colorado, USA), allows seaway wide versus local changes in biogeochemical cycling to be differentiated. These results suggest that while enhanced organic carbon burial is favored in the WIS during the Niobrara transgression, there is no evidence for a single, discrete, seaway-wide anoxic event during the Coniacian-Santonian. In the Sweetgrass Arch region, enhanced organic carbon accumulation and the development of anoxia is controlled by the incursion of Tethyan waters into the region and may have been influenced by significant nutrient addition from ash deposition. A sea level control on the incursion of southern sourced water masses and, subsequent deoxygenation and enhanced organic carbon burial in the WIS, may explain why "OAE 3" is only identified in shallow and restricted marine environments that would be sensitive to changes in sea level. A combination of local and eustatic controls on sea level may also explain the diachronous timing of enhanced organic carbon burial in different regions.

ISSN: 0016-7606
EISSN: 1943-2674
Serial Title: Geological Society of America Bulletin
Serial Volume: 131
Serial Issue: 5-6
Title: Local versus seaway-wide trends in deoxygenation in the Late Cretaceous Western Interior Seaway
Affiliation: University of Michigan, Department of Earth and Environmental Sciences, Ann Arbor, MI, United States
Pages: 1017-1030
Published: 20181127
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 82
Accession Number: 2019-007055
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. cols., geol. sketch map
N49°00'00" - N60°00'00", W102°00'00" - W89°30'00"
N37°00'00" - N41°00'00", W109°00'00" - W102°00'00"
Secondary Affiliation: Carleton University, CAN, CanadaALS Oil and Gas, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201906
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