HIGH LATITUDE METEORIC OXYGEN ISOTOPE COMPOSITIONS FROM THE CENOMANIAN LOWER KANGUK FORMATION, AXEL HEIBERG ISLAND, CANADIAN ARCTIC ARCHIPELAGO

Pedogenic carbonates and siderites formed in Cretaceous paleosols from paleoequatorial to paleopolar latitudes in North America have provided useful stable isotopic paleohydrologic data to help constrain the oxygen isotope mass balance of the mid-Cretaceous hydrologic cycle. Data are very sparse in polar locales, and there is a pressing need for more of these data to advance this line of inquiry. Glacier Fiord at Axel Heiberg Island, Nunavut, Canada contains a Cretaceous (Valanginian to Campanian) record of deposition in the Sverdrup basin. At approximately 70°N paleolatitude, Cenomanian sideritic mudstone of the lower Kanguk Formation produce carbon isotopic values of +4.02‰ ± 0.30‰ VPDB and oxygen isotopic values of -18.95‰ ± 0.33‰ VPDB. Based on an estimated zonal mean annual Cretaceous paleotemperature of ~13°C a paleoprecipitation oxygen isotopic value is calculated to be -23.11‰ VSMOW, a value that is consistent with other paleo-Arctic estimates for Cretaceous precipitation produced from the Colville Basin in northern Alaska. Results from Axel Heiberg Island further build the case for low δ¹⁸O values for polar paleoprecipitation during warm periods in Earth History. Empirical datasets from greenhouse periods indicating low δ¹⁸O values (≤ -20‰ VSMOW) for paleopolar precipitation are inconsistent with results from GCM simulations with water isotope modules, suggesting much higher δ¹⁸O values should be expected. Are all high latitude freshwater δ¹⁸O data from greenhouse worlds biased by snowmelt/orographic effects? The positive δ¹³C values from freshwater siderites in the Kanguk Formation are shared in common with all other sampled Cretaceous units from north of 50°N paleolatitude, and are indicative of methane-emitting high latitude paleoenvironments.