 A small (but significant) iridium anomaly occurs at the boundary on Seymour Island, as at lower latitudes, thought to be fallout from the Chicxulub impactor in the Gulf of Mexico.Directly above the boundary a layer of disarticulated fish fossils occurs, victims of a disturbed ecosystem immediately following the impact event.Multiple reports have described evidence for climatic changes in Antarctica prior to the mass extinction, but the extent to which these affected marine biodiversity is debated.