The palynofloral changes around the Cretaceous-Paleogene (K-Pg) mass extinction event reveal the fine details of vegetation response to a global environmental crisis – in this case an asteroid impact in Mexico 65.5 million years ago. Due to the extinction of several plant taxa at the K-Pg boundary, palynostratigraphy is a prime tool for localizing the Cretaceous-Paleogene boundary in non-marine successions. The Southern Hemisphere includes the tropical to sub-tropical Palmae Province, the high-latitude Nothofagidites/Proteacidites Province, and a transitional zone of mixed floristic composition. 

Significant proportion of the Southern Hemisphere data has historically accumulated as a by-product of commercial hydrocarbon exploration. Thus, these studies have not targeted the K-Pg boundary to specifically identify the iridium-enriched boundary layer or sample at high-resolution in order to evaluate the detailed floristic changes brought about by the environmental upheaval ensuing from the Chicxulub asteroid impact. The mass-kill in the vegetation at the K-Pg boundary and the subsequent post-impact recovery succession is only recognizable at centimeter resolution in stratigraphic sections due to the rapidity of the vegetation’s re-establishment; hence most of the coarse-scale sampling in the Southern Hemisphere does not detect the extinction and early stages of the recovery succession. Despite the limitations of this data, a large quantity of high quality palynological information is available and has been used for broad-scale biostratigraphic subdivision and reconstruction of floristic provincialism during the Late Cretaceous and Paleogene.

Maastrichtian key-species that go extinct at the Cretaceous-Paleogene boundary within the Palmae Province include Aquilapollenites magnus, Buttinia andreevi, Crassitricolporites brasiliensis, Proteacidites dehaani and Gabonisporis vigourouxii. In the Nothofagidites/Proteacidites Province, taxa such as Tricolporites lilliei, Triporopollenites sectilis, Quadraplanus brossus, Nothofagidites kaitangata, and Grapnelispora evansii have their last appearances at the boundary.More thorough analyses of the palynological signals across the K-Pg boundary in the Southern Hemisphere and in China are required to elucidate the detailed patterns of vegetation response at different latitudes and at varying distances from the impact site in Yucatan, Mexico.