Figure 4. Correlation of Yaxcopoil-1 (Yax-1) with Pemex cores from Yucatan[25
]. Note that sedimentation, including the impact breccia, is reduced in Yax-1, suggesting that deposition occurred on an uplifted flank of the crater. The presence of late Maastrichtian sediments above the impact breccia has been observed in cores Yax-1, T1, Y6 and C1, as well as from NE Mexico. Stratified lithologies, normal age sequence and several biohorizons can be correlated across the crater (except for Y6 and C1) and onto the Yucatan platform, which indicates normal deposition.
The existence of an impact crater neither proves nor explains the demise of the dinosaurs, or the mass extinction of any other group. The palaeontological database amassed during the last 20 years lends little support to a scenario of sudden mass extinction at the K/T boundary 26
, except for tropical-subtropical planktic foraminifera 27,28.
Moreover, a sudden mass extinction cannot explain its selective nature, (e.g. foraminifera, rudists), its varying effects at different latitudes nor the progressive extinction trend that precedes the K/T boundary 26-29
Can multiple impacts explain this trend? Although Chicxulub may now be considered a late Maastrichtian zone CF1 impact, coinciding with a time of major global greenhouse warming and volcanism, no major extinctions are associated with it. Was the K/T impact much larger, or did it coincide with major volcanism that together led to the final, lethal environmental disturbance? We believe the latter is the case.
A study of the way in which planktic foraminifera responded to late Maastrichtian volcanism on Ninetyeast Ridge (Indian Ocean), has revealed biotic effects virtually identical to the K/T mass extinction 30
. To us, this is further indication that the end-Cretaceous mass extinction was the result not of a single hammer-blow. It was, instead, a progressive multi-event catastrophe - a concerted assault on the whole edifice of life by a combination of massive volcanism, multiple impacts and their associated climatic and environmental changes.
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- Department of Geosciences, Princeton University, Princeton NJ 08540, USA email@example.com
- Institut of Geology, University of Neuchatel, 2007 Neuchatel, Switzerland Thierry.Adatte@unine.ch
- Geolofical Institute, University of Karlsruhe, D-76128 Karlsruhe, Germany Wolfgang.Stinnesbeck@bio-geo.uni-karlsruhe.de