INVESTIGATIONS OF LATE CRETACEOUS ARCTIC PALEOHYDROLOGY BY INTEGRATION OF TERRESTRIAL STABLE ISOTOPE PROXIES

Given the sensitivity to climate change in the Arctic seen today, investigations of global warming events in the Arctic during earth history offer the potential to improve estimates of the earth system’s range of future climate changes. A multi-proxy investigation of the Prince Creek Formation (Campanian-early Maastrichtian) was undertaken to constrain Cretaceous paleohydrology, which is directly linked to climate via atmosphere-hydrosphere interactions. These proxies include the oxygen isotopic composition (relative to V-SMOW) of pedogenic siderites and dinosaur tooth enamel. Based on a zonal mean annual temperature (MAT) of 5ºC (Parrish & Spicer, 1988, Geology 16:22-25), meteoric water (MW) compositions estimated from siderites from two horizons range from -21.80 ‰ to -22.00, ± 0.43‰, respectively. Assuming a body temperature of 37ºC and an estimated relative humidity of 77.5%, dinosaur tooth enamel suggest that their consumed water values ranged from -25.6 ± 0.2‰ for hadrosaurs at Pediomys Point to -20.6 ± 0.5‰ for Edmontosaurus at the Liscomb Quarry. Terrestrial vertebrates record a range of water reservoirs from local MW to river water. Based on these data, dinosaurs consumed water that was both influenced by local MW as estimated from siderites, and a more depleted water probably draining from the Brooks Range >100 km to the south. Dinosaur data confirm the existence of extremely light δ¹⁸O values for Cretaceous high-latitude MW. These lower values are likely due to an intensified Cretaceous hydrologic cycle and higher rainout of ¹⁸O from atmospheric moisture during poleward transport from the tropics. This insight has also led to arguments for increased poleward latent heat transport in the generally warm Cretaceous climate system. Further analysis of δ¹⁸O from fossil clam and snail shell carbonate, along with the dinosaur enamel and siderite from a wider Cretaceous Arctic sampling network, may help to construct detailed “isoscapes” from several time slices to constrain the isotopic compositions of Cretaceous paleoprecipitation in the high-latitudes, and may help to elucidate discrepancies between reconstructed MW δ¹⁸O values from high-latitude environments of the Arctic generated by earth system models versus empirically derived data.