T8 Evolution of the Western Interior Basin: New Advances and Fresh Perspectives

Sunday, 15 October 2023
8:00 AM - 12:00 PM
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THE TEMPERATURE EVOLUTION OF THE WESTERN INTERIOR SEAWAY: ALBIAN TO MAASTRICHTIAN

Paper number: T8-6
Program: Technical Sessions
Time: 9:05 AM – 9:20 AM

Authors

Abstract

The strata and fauna of the Cretaceous Western Interior Seaway (WIS) have been extensively studied, but paleoclimate and paleoceanographic studies have been a challenge historically. Early paleotemperature reconstructions using oxygen isotope paleothermometry produced implausibly high temperatures, indicating that oxygen isotopic composition for waters (δ18Ow) in the seaway likely deviated from the often assumed “ice-free” ocean end-member composition, thus hindering useful application of this method. The more recently developed clumped isotope paleothermometer distinguishes the contributions of temperature and δ18Ow to the oxygen isotopic composition of carbonate minerals (δ18Ocarb), enabling accurate reconstruction of seaway temperature and δ18Ow conditions. To date, clumped isotope studies of the WIS have generally focused on single time periods. Here, we present paleotemperature and paleo-δ18Ow data from fossil mollusk samples dating from the late Albian to Maastrichtian (~103-69 Ma), with the aim of reconstructing the long-term paleoceanographic evolution of the WIS. Measured samples (n > 110) were selected from fossil collections of the U.S. Geological Survey (now housed at the National Museum of Natural History) and the University of Michigan, spanning a wide geographic range within the WIS from outcrops in the Great Plains, Rocky Mountains, and Gulf Coast regions of the United States. The temperatures measured from marine mollusks were compared to those derived from river-dwelling bivalves, but there were challenges disentangling their variability in space and time. Generally, the temperature evolution of the WIS tracks global temperature reconstructions for the Cretaceous, while δ18Ow values suggest mixing of a saltier Gulf of Mexico water mass with a more brackish Arctic water mass combined with a smaller component of fresh riverine input. This dataset represents a first step towards a broader goal of reconstructing temperature evolution in the Cretaceous WIS through space and time and shows the potential of this method to resolve outstanding issues such as circulation patterns in the WIS.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-390719

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