RECONSTRUCTING THE LATE CRETACEOUS PALEOENVIRONMENT THROUGH MICROFOSSIL ASSEMBLAGES IN THE SAND ARROYO BADLANDS: HIGHLIGHTING THE IMPORTANCE OF PALEONTOLOGICAL INVENTORIES ON PUBLIC LANDS

Eastern Montana plays host to some of the most famous, well-studied, and diverse paleontological resources in the world, much of which is located on public lands. Keeping these spaces accessible to both researchers and the general public while also prioritizing the preservation of fossilized matter is at the core of the Bureau of Land Management’s (BLM) Paleontological Resources program.

This balance is achieved by designating certain parcels of land as an Area of Critical Environmental Concern (ACEC), which allows the federal government to provide additional oversight designed to suit the lands needs. The Sand Arroyo Badlands, a region that documents the Cretaceous-Tertiary turnover through the Hell Creek and Fort Union Formations, is one such ACEC managed by the Miles City BLM Field Office. By conducting a detailed inventory of the rich microfossil assemblages distributed across the Sand Arroyo Badlands ACEC, the BLM not only gains insight into the land they protect, but also provides additional data into the continued efforts to provide paleoenvironmental reconstructions of the late Cretaceous. This inventory documents a rich semi-aquatic environment, crowded by gar, turtle, and crocodilian remains. These assemblages also document a terrestrial community dominated by large-bodied ceratopsian and hadrosaurian dinosaurs. Tracking the variation in present vertebrate remains at the various microfossil localities indicates directional river flow, the presence of both aquatic and terrestrial ecosystems, and a more complete analysis of life in Sand Arroyo 67 million years ago.