Tim White, Luis González, Greg Ludvigson, Chris Poulsen; Middle Cretaceous greenhouse hydrologic cycle of North America. Geology ; 29 (4): 363–366. doi: https://doi.org/10.1130/0091-7613(2001)029<0363:MCGHCO>2.0.CO;2
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We present a paleolatitudinal precipitation reconstruction for the greenhouse setting of mid-latitude North America based on the oxygen isotopic composition of sphaerosiderites found in middle Cretaceous wetland paleosols. Our reconstructed middle Cretaceous δ18O values of precipitation are ∼4‰ less than values from comparable modern low-elevation coastal settings free of monsoons. The data fit a conceptual model in which the precipitation source for the eastern margin of the Cretaceous Western Interior Seaway of North America is an 18O-enriched oceanic coastal jet. In this subtropical-tropical setting, mid- Cretaceous precipitation rates are interpreted to range from ∼2500 to ∼4100 mm/yr.