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

Sunday, 15 October 2023
8:00 AM - 12:00 PM
301 / 302

CONTINENTAL CLIMATE AND HYDROLOGY IN THE CAMPANIAN WESTERN INTERIOR BASIN INFERRED FROM CLUMPED ISOTOPE PALEOTHERMOMETRY

Paper number: T8-8
Program: Technical Sessions
Time: 9:35 AM – 9:50 AM

Authors

Abstract

Vast epicontinental seaways are one of the defining features of Cretaceous paleogeography. The North American Western Interior Seaway (WIS) received inputs of water from the proto-Gulf of Mexico, Arctic Ocean, and continental freshwater in the Campanian (~83-72 Ma). The temperature and isotopic composition of freshwater responded to overall climate, overland precipitation patterns, and diachronous uplift during the Sevier and Laramide orogenies. We measure Δ47 in unionid bivalve shells to constrain temperature and δ18Owater of river and pond environments along the western shore of the WIS (~36.7°N-48.7°N) in the late Campanian (~75 Ma). Supplemental 87Sr/86Sr measurements provide additional context about depositional environment. We report surface water temperatures ranging from 23°C to 37°C and a reduced latitudinal temperature gradient in this hothouse world compared to modern. We use these new Δ47 temperatures, which indicate shell growth outside the optimal temperature range observed for modern unionids, to recalculate previously published δ18Owater values for Campanian freshwater environments (n = 244). The Δ47 temperatures shift δ18Owater values higher than previous estimates, resulting in a bimodal distribution of values centered around -14‰ and -7‰. More radiogenic 87Sr/86Sr values are associated with lower δ18Owater values and vice versa, broadly corroborating the hypothesis that major trunk rivers include the extreme highlands in their catchments and the catchments of smaller streams are limited to the foreland basin. The lowest δ18Owater values we observe in trunk rivers bolster previous estimates of >3500m elevation in the Campanian Proto-Cordillera. This high elevation in the Campanian is consistent with previous paleoelevation estimates for the Nevadaplano in the Maastrichtian and early Cenozoic. Taken together it appears the Nevadaplano was a long-standing topographic feature, consistent with other structural and sedimentological data.

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

doi: 10.1130/abs/2023AM-395161

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