GLOBAL DISRUPTION OF VEGETATION AT THE CRETACEOUS-TERTIARY BOUNDARY – A COMPARISON BETWEEN THE NORTHERN AND SOUTHERN HEMISPHERE PALYNOLOGICAL SIGNALS

The devastation of ecosystems as a consequence of the Chicxulub meteorite impact 65 million years ago is clearly detectable in the geological records globally. A high-resolution investigation of Southern Hemisphere Cretaceous-Tertiary boundary (KTB) sediments reveals that, just as at North American KTB sites, a diverse, Late Cretaceous vegetation was abruptly replaced by an impoverished flora dominated by a few species of ferns in the earliest Paleocene. This so-called fern-spike which is often associated with iridium enrichment in the sediments is well-documented in the southern and central United States (Nichols & Johnson 2002). New palynological data is presented here from five New Zealand Cretaceous-Tertiary boundary sections, all of them characterized by massive vegetation disruption. These data strengthen the evidence for a global disruption of vegetation at the Cretaceous-Tertiary boundary (KTB) especially as the palynological signal through the New Zealand KT sections is very similar to those of the southern and central United States. However, there are important regional differences in the signature of vegetation turnover. The data suggest both massive devastation and mass extinction of plants at many sites in North America but mainly mass-dieback of vegetation in New Zealand resulting in dramatic but short-term changes in the relative abundance of plant groups (Vajda et al. 2001). New Zealand, located in high south latitudes at the time of impact and far from the Chixculub crater site, provides an invaluable opportunity to test the global effects of the bolide impact on ecosystem biodiversity.

Nichols, D.J. & Johnson, K.R., 2003: Palynology and microstratigraphy of Cretaceous-Tertiary boundary sections in southwestern North Dakota. In: J.H. Hartman, K.R. Johnson, D.J. Nichols (eds). Geol. Soc. Am. Spec. Paper 361: 95-144.

Vajda, V., Raine J.I. & Hollis C.J. 2001: Indication of global deforestation at the Cretaceous-Tertiary boundary by New Zealand fern spike. Science 294: 1700-1702.