Cover Photo: Thin-section view of a 0.7 mm impact spherule pseudomorph among mainly quartz sand grains from the K–T boundary section at Shell Creek, Alabama. The spherule pseudomorph shows smectite wall structure and an internal crystalline calcite filling. The laminated wall structure consists of alternating light and dark layers, which is likely the result of diagenetic alteration of the original glass as it devitrified. The exterior surfaces of these impact spherules commonly show numerous small indentations (seen here in cross-sectional view), which have been interpreted as primary features such as vesicle eruptions and impact pits resulting from plastic deformation among colliding particles in the vapor cloud. Green color is from epoxy in open spaces. See Ferrell et al., this issue.