MULTI-TAXON OXYGEN ISOTOPE ANALYSIS OF BIOAPATITES FROM THE CLOVERLY FORMATION, WYOMING

Understanding of climate parameters and hydrology during past greenhouse conditions is important to forecasting future climate conditions. Oxygen isotopes of vertebrate bioapatites offer an opportunity to sample conditions across ancient landscapes. 112 samples from a variety of ecological niches were sampled from Cloverly Formation (Lower Cretaceous) micro-vertebrate site V1075 reposited at the Sam Nobel Museum at the University of Oklahoma. These samples were analyzed at the Keck Paleoenvironmental and Environmental Stable Isotope lab at the University of Kansas. Phosphate δ¹⁸O values range from between 9‰ to 23‰ vs. SMOW and show significant variability based on interpreted ecological niche of the taxa. Utilizing crocodilian and turtle d18Op values, environmental water oxygen isotope values are interpreted to be approximately -8‰ SMOW. These values are about 2-4‰ enriched relative to past estimates based on latitudinal gradients from penecontemporaneous formations from other latitudes. Based on water isotope estimates, fish δ¹⁸O values were used to calculate water temperature values of ~26°C which is consistent with estimated temperatures based on latitudinal gradients for the Cretaceous. In addition, preliminary carbonate clumped isotope paleothermometry suggest similar temperatures. These results along with emerging data from similar age deposits are beginning to build an emerging view of climate on the western side of the Western Interior Seaway during the late Early Cretaceous.