[4] 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.

[5] Directly above the boundary a layer of disarticulated fish fossils occurs, victims of a disturbed ecosystem immediately following the impact event.

Based on extensive marine fossil collections from Seymour Island, recent work has confirmed that a single and severe mass extinction event occurred at this time in Antarctica just as at lower latitudes.

[9][10] Alternatively, a study using data acquired from ancient bacterial membrane lipids yielded a slightly warmer temperature of 12 ± 5 °C (54 ± 9 °F) around 66 Ma.

[14] Dinosaur remains are among the fossils that have been recovered from the formation[15] and include at least two and probably as much as six lineages of indisputably modern birds: one related to waterfowl, a primitive shorebird or related form, 1 to 2 species of possible loons, a large and possibly flightless bird belonging to a lineage extinct today as well as a partial skull that might belong to either of the smaller species or represent yet another one.