55 Sequence Stratigraphic, Geochemical, and Geochronologic Correlation of the Cenomanian-Turonian Ocean Anoxic Event 2 (OAE2) in the Cretaceous Western Interior Seaway (KWIS) and the Gulf Coast

The Cenomanian-Turonian Ocean Anoxic Event 2 (OAE2) is a global event, however its stratigraphic, geochemical, and geochronologic records are locally quite variable. This session will correlate the OAE2 records in the Cretaceous Western Interior Seaway (KWIS) and the Gulf Coast.

Sunday, 19 October 2025
1:30 PM - 5:30 PM
HBGCC, 303C

Before, during, and after OAE2 at approximately 53- and 54-degrees north latitude in the Western Canadian Sedimentary Basin, Alberta, Canada

Paper number: 55-3
Program: Technical Sessions
Time: 2:05 PM – 2:25 PM

Authors

Abstract

We report new wavelength-dispersive X-ray fluorescence, total and inorganic carbon, stable 13C and 15N isotopes, and proxy records at a 0.5 m sample interval from a virtuously continuous, slabbed whole core (~ 190 m long) at ~54 degrees north latitude near the Cold Lake area of eastern Alberta, Canada which approximately spans from the Late Albian to the Middle Campanian – age estimates via litho- and chemostratigraphic correlations. These records are correlated to a stable 13C record and other proxy records from a ~ 270 m long core in the foredeep area of the Western Canadian Sedimentary Basin of Alberta (WCSB), Canada at ~53 degrees north latitude as well as temporally well constrained 13C records elsewhere in the more southernly portions of the Cretaceous Western Interior Seaway (KWIS). Both Canadian records in this study capture the paleoceanographic conditions of the KWIS before, during, and after OAE2 wherein several understudied oceanic anoxic events (OAEs) are also documented. OAEs in this study are statistically defined using the inflection and segmented methods. Leading up to OAE2 at ~54 degrees north latitude, the KWIS was highly euxinic as revealed by an enrichment of Mo relative to the Average Shale and Corg/P values beyond modern euxinia thresholds. The onset of OAE2 records more oxygenated bottom water conditions after which a punctuated period of euxinia occurred followed by more oxic bottom water conditions until the termination of OAE2 when euxinia was again persistent. Syngenetic pyrite formation is common during euxinia with decreases occurring during more oxygenated bottom water conditions. Following the punctuated period of euxinia during OAE2, syngenetic pyrite formation is absent suggesting water column conditions at ~54 degree north latitude was oxygenated until the termination of OAE2. This trend is also observed in the WCSB at ~53 degrees north latitude except for syngenetic pyrite formation was occurring during OAE2. The highest observed TOC concentrations occur during periods of enhanced euxinia and the lowest occurring during more oxygenated bottom water conditions. The highest concentrations of bioessential nutrients are observed during periods of euxinia. Finally, we argue that the regional transgressive X Surface demarcates the onset of the Greenhorn Cyclothem and re-established connection of the northern KWIS to the southern KWIS due to increases in elemental concentrations at both Canadian study sites.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412693

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