We have constrained the age of the Nussbaum Gravel at Baculite Mesa, CO using cosmogenic Al-26/Be-10 isochron burial dating. Two samples, a coarse sand and a fine gravel, were prepared for burial dating at the Reston Cosmogenic Nuclide (RECON) Lab and measured via accelerator mass spectrometry at the Purdue Rare Isotope Measurement (PRIME) Lab. The results of this work are summarized in the file “BaculiteMesa_SiteLocation_Odom.csv”, which contains site data and burial age calculations; measurements of aluminum-26 and beryllium-10, as well as related data, are located in respective .csv files. We calculated respective minimum and maximum burial ages for the sand (1.25 ± 0.08 Ma and 1.66 ± 0.12 Ma) and gravel (1.44 ± 0.26 Ma and 2.17 ± 0.40 Ma). An unconstrained isochron regression of these samples yields a most likely burial age of 1.11 ± 0.69 Ma; however, this isochron features a slightly negative estimate of postburial cosmogenic nuclide production that is not realistic. This may be due to minor reworking of the gravel fraction. Forcing postburial production to zero produces a more likely representation of the data and yields a preferred burial age of 1.30 ± 0.08 Ma. This age is consistent with a glacial advance in Missouri dated by cosmogenic nuclides to 1.31 ± 0.13 Ma (Balco and Rovey, 2010). We are grateful for permission from landowner Darin Smith to access and sample this site.
