DIAGENESIS OF VERTEBRATE SKELETAL REMAINS OF THE CRETACEOUS KAIPAROWITS FORMATION AND THEIR USE AS PALEOHYDROLOGIC PROXIES: A COMPLEX HYDROLOGIC SETTING

The Kaiparowits Formation is a rapidly deposited fluvial-coastal plain deposit and preserves one of the most complete fossil records of the Campanian (late Cretaceous) North America. Such a unique deposit provides an opportunity to investigate the interaction between physical environment and paleoecology. As a part of paleoclimatic investigation, stable isotope compositions of vertebrate skeletal remains were analyzed. The oxygen isotope compositions of structural (δ¹⁸O_c) and phosphate (δ¹⁸O_p) do not exhibit the equilibrium relationship observed in modern mammal bone, suggesting potential diagenetic alteration to one or both oxygen components. However, average δ¹⁸O_c from each taxon show the same trend as the δ¹⁸O_p stratigraphic change, suggesting potential use of δ¹⁸O_c as a paleoclimatic proxy. Previous study indicates influence of the Western Interior Seaway at 300m from the base and δ¹⁸O_p of turtle and crocodile are supportive of this trend. Compared to other Campanian formations, fossil δ¹⁸O_p are depleted for their paleolatitude, suggesting the Kaiparowits Plateau had higher input from high-elevation runoff, consistent with other paleoclimatic studies. Estimated δ¹⁸O_w ranged between vadose influenced dry season values of -8.88‰ to high elevation runoff values of -13.76‰ suggesting dynamic hydrologic interactions.