Stable Isotope Tracers of Cretaceous Arctic Paleoprecipitation

We report estimated stable isotope compositions of depositional waters and paleoprecipitation from the Cretaceous Arctic to further elucidate the role of the global hydrologic cycle in sustaining polar warmth during that period. Estimates are based on new hydrogen isotopic analyses of n -alkane biom...

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Bibliographic Details
Published in:Geosciences
Main Authors: Greg A. Ludvigson, Aaron F. Diefendorf, Marina B. Suarez, Luis A. González, Megan C. Corcoran, Kristen Schlanser, Peter P. Flaig, Paul J. McCarthy, Dolores van der Kolk, David Houseknecht, Margaret Sanders
Format: Article in Journal/Newspaper
Language:English
Published: MDPI AG 2022
Subjects:
Cretaceous
hydrologic cycle
hydrogen and oxygen isotopes
polar warmth
Geology
QE1-996.5
Arctic
Alaska
Online Access:https://doi.org/10.3390/geosciences12040143
https://doaj.org/article/f7b3cffbb4724ae580c89817729e35a7
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Summary:We report estimated stable isotope compositions of depositional waters and paleoprecipitation from the Cretaceous Arctic to further elucidate the role of the global hydrologic cycle in sustaining polar warmth during that period. Estimates are based on new hydrogen isotopic analyses of n -alkane biomarkers extracted from Late Cretaceous and mid-Cretaceous terrestrial deposits in northern Alaska and the Canadian High Arctic. We integrate these new results with earlier published work on oxygen isotopic analyses of pedogenic siderites, dinosaurian tooth enamel phosphates, and pedogenic clay minerals from the same field areas. Average Late Cretaceous δD values of −143‰ VSMOW corresponded with average δ 18 O values of −24.1‰ VSMOW, and average mid-Cretaceous δD values of −106‰ VSMOW corresponded with average δ 18 O values of −22.1‰ VSMOW. The distributions of water isotope δD and δ 18 O values from Cretaceous Arctic deposits do not intersect with the Global Meteoric Water Line, suggesting an apparent deuterium excess ranging from about 40 to 60 per mil. We considered several possible explanations for these Cretaceous results including (1) mass-balance changes in zonal patterns of evaporation and precipitation at lower latitudes, (2) concentration of 2 H in leaf tissue waters from continuous transpiration by coniferous paleofloras during the Arctic growing season, and (3) concentration of 2 H in the groundwaters of methane-emitting Arctic soils.

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