Middle Cretaceous greenhouse hydrologic cycle of North America

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 delta (18)O values of precipitation are similar to4 parts per thousand 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 (18)O-enriched oceanic coastal jet. In this subtropical-tropical setting, mid-Cretaceous precipitation rates are interpreted to range from similar to 2500 to similar to 4100 mm/yr.