Rare Earth Element Concentrations as a Novel Proxy for Lateral Continuity: An Initial Case Study in the Cretaceous Lance Formation of Wyoming

Identifying stratigraphic continuity across outcrops can sometimes be difficult, especially if they are dominated by discontinuous strata. Therefore, stratigraphers continue to seek new proxies for testing stratigraphic continuity, including fossiliferous horizons. We present a case study examining the potential of fossil bone trace element signatures as a novel proxy for lateral continuity. Specifically, we performed trace element analyses of Edmontosaurus bones from the Neufeld Quarry at Hanson Ranch (HR) in Wyoming, a stratigraphically verified lateral equivalent of the famous HR Bonebed exposed nearby in five “Main Quarries”, to evaluate if these chemical data would independently lead a researcher to the same conclusion of lateral equivalency. Bones from the “Main Quarries” and Neufeld were found to exhibit similar patterns of trace element alteration, including comparable magnitudes of enrichment, spatial patterns of rare earth element uptake, and proportions of specimens exhibiting various styles of diagenetic alteration. Many bones from both sites also exhibit redox signatures indicative of trace element uptake under reducing conditions. These numerous similarities in geochemical alteration patterns independently indicate that the fossil horizon at Neufeld is a lateral continuation of the nearby HR Bonebed. Our findings thus demonstrate the power of trace elements toward identifying laterally equivalent fossil assemblages.