Global Effects of the Chicxulub Impact on Terrestrial Vegetation — Review of the Palynological Record from New Zealand Cretaceous/Tertiary Boundary

Abstract

Analysis of pollen and spore assemblages from both terrestrial and near-shore marine sediments in New Zealand reveal an instant and dramatic mass-kill of the land plants in close association with the Cretaceous-Tertiary boundary (KTB) event. The turnover in the palynoflora is followed by a recovery succession, the most prominent feature of which is an interval dominated by fern spores (fern spike) starting at the boundary in the three sections studied. The duration of the period of fern-dominance is here calculated to have lasted for ca. 8000-20,000 years, based on sedimentation rates calculated from foramineral data. This time span is orders of magnitude greater than seen in normal seral successions following deforestation. We suggest that, whereas low ambient light levels initially favoured communities dominated by pioneering free-sporing plants (ferns and bryophytes), other environmental variables relating to the suppression of seed stocks or seedling growth were probably responsible for the long interval required for re-establishment of gymnosperm- and angiosperm- dominated vegetation. In New Zealand, the devastated vegetation recovered slowly, many of the latest Cretaceous taxa reappearing higher in the succession following their absence in the lowermost Paleocene. One hundred and five miospore taxa were identified in the three sections. Species-level extinction rate at the KTB is below 15%, although more extensive biostratigraphic studies are needed to confirm this. Based on the miospore assemblages and leaf fossil physiognomic studies' the Early Paleocene climate was cooler than prior to the K/T event, perhaps reflecting long-term consequences of the impact.