AUTHIGENIC MINERALOGY AND ELEMENT DISTRIBUTIONS OF VERTEBRATE MICROFOSSILS FROM THE HELL CREEK (LATEST CRETACEOUS) AND TULLOCK (PALEOCENE) FORMATIONS OF EASTERN MONTANA
Primary voids in bones from both formations were usually empty, although many exhibited detrital infills consisting of clay and silt-sized grains of quartz and feldspar. Authigenic minerals appear to be limited to pyrite and iron oxide framboids, which vary in abundance both within and between localities, and occur as globular clusters along the edge of bone pores. These framboids, particularly those which have altered to iron oxide, often occur in close association with clay minerals. Neither authigenic mineralogy nor bulk geochemistry show a noticeable change across the K-Pg boundary, which may suggest that fossil vertebrates from both the Hell Creek and Tullock formations experienced similar diagenetic conditions on the path to fossilization. Though these results are preliminary, they represent the first attempt to characterize the diagenetic history of vertebrate fossils across the K-Pg boundary from the Hell Creek region of eastern Montana, and they set the stage for future research into post-depositional changes that influence our understanding of the K-Pg mass extinction.