Online guide to the continental Cretaceous-Tertiary boundary in the Raton basin, Colorado and New Mexico

Figure 7. Diagram showing the lithology of the K-T boundary sequence at the Long Canyon K-T boundary site in the Watchable Wildlife area of Trinidad Lake State Park. The inset shows the detail of the boundary interval and the variation in iridium concentration. (Iridium analyses courtesy of F. Asaro, Lawrence Berkley Laboratory, written comm. 1999). Palynologic analyses of samples collected across the boundary at the Madrid site (fig. 1) show that more that 80 percent of the assemblage in the coal bed directly above the boundary claystone bed consists of fern spores (R. H. Tschudy of the USGS, written comm. 1982).