This proposal is for a small grant for exploratory research (SGER): a pilot study of buried soils to attempt to detect mobilization of heavy trace metals, decalcification and podzolization that should have accompanied the nitric acid rain predicted by some scenarios of extraterrestrial impact at the Cretaceous-Tertiary boundary. A suitably complete sequence of buried soils across this geological boundary has been located and sampled in Bug Creek, eastern Montana. Analyses of selected paleosols will be performed by AA (major and trace elements), isotopic dilution mass spectrometry (for Pb) and Walkley-Black (for organic carbon) techniques. Petrographic studies also will be undertaken in order to complete documentation of the subsurface clayey (Bt) horizons and other paleoenvironmentally significant features of the paleosols. Nitric acid rain would be indicated by strong depletion of the paleosol at the boundary in Pb and other heavy metal trace elements, compared to the depth function for these elements in paleosols above and below the boundary that are otherwise similar petrographically, chemically and in burial history. Should this research prove to indicate acid rain, then full scale search of other sequences of paleosols across the Cretaceous-Tertiary boundary would be warranted. Should this research be unsuccessful indicating acid rain, it may nevertheless add paleoenvironmental information for reconstructing events at this place and time in Earth history.
