INVESTIGATING THE FORMATION OF VERTEBRATE MICROFOSSIL BONEBEDS FROM THE LATE CRETACEOUS HELL CREEK FORMATION IN GARFIELD COUNTY, MONTANA
We collected 20 kg bulk samples from five fluvial and lacustrine VMBs identified in the Late Cretaceous Hell Creek Formation in Garfield County, MT. After screening, identifying, and sorting the samples, we measured taphonomic characteristics of the fossils, such as wear, size, and shape. The taphonomic data were statistically analyzed to see whether preservation differed significantly according to paleoenvironment. Additionally, we quantified and compared species abundance, richness, and evenness among VMBs to assess paleoecological differences between sites deposited in lacustrine versus fluvial environments.
Preliminary results from all sites indicate a high abundance of osteichthyans (particularly representatives of Lepisosteidae) with successively rarer occurrences of reptiles, amphibians, and mammals. The majority of the fossils possess aquatic or semiaquatic affinities. Lastly, the samples derived from lacustrine deposits appear to have greater species richness than those samples from fluvial deposits. Together these data provide support for a common depositional source across multiple sites.