Paleoclimate reconstruction of the Prince Creek Formation, Arctic Alaska, during Maastrichtian global warming

The Upper Cretaceous (Maastrichtian) Prince Creek Formation of Arctic Alaska (~82–85°N paleolatitude) preserves successions of alluvial paleosols that are used to estimate mean annual precipitation (MAP), mean annual temperature (MAT) and meteoric water oxygen isotope composition. For the Prince Creek Formation, the highest MAP estimates range between 1000 and 3900 mm/yr and the lowest range between 350 and 1200 mm/yr. The precipitation variability, derived from stable carbon isotope analysis, occurs on a time scale of 104 years. MAP values agree with previous interpretations from fossil pollen, pedological features, soil types, vegetation composition, sedimentological indicators and CLAMP estimates that suggest high precipitation amounts and high humidity. Despite the considerable uncertainty with MAT proxies, our values are consistent with warm month mean temperatures obtained previously from paleobotanical data. The δ18O of smectite from bentonite beds clusters around ~+5.0‰ (VSMOW). The δ18O of meteoric water calculated from bentonitic smectite is ~−23‰ (VSMOW), assuming a mean annual temperature of 6.3 °C, which is slightly more 18O-depleted than meteoric water calculated from pedogenic siderite in stratigraphically younger beds closer to the Brooks Range. Chronostratigraphic correlation with the lower Cantwell Formation, Denali National Park, Alaska (~64°N paleolatitude), suggests higher precipitation rates and highly 18O-depleted precipitation in the Late Cretaceous paleo-Arctic compared to central Alaska. These data are consistent with previous studies that suggest a warmer and moister greenhouse Earth and an intensified hydrological cycle that enhanced latent heat transport, resulting in increased rainout effects.