Description
The Cretaceous-Palaeogene boundary in Denmark is world famous for its completeness and represents one of the biostratigraphically most important successions of this time interval. The succession of limestones and chalk was deposited in a narrow northwest - southeast running strait named the Danish Basin. This basin contained a fully marine environment with a largely muddy sea floor inhabited by a rich shelly macrofauna of especially bryozoans, but also of bivalves, gastropods, cephalopods, polychaetes and brachiopods in addition to anthozoans and sponges.
The gastropods represents one of the most abundant and diverse faunal groups in the K-T boundary interval, making them ideal for ecological studies. Preliminary results reveal that though the diversity is stable across the boundary with over 50 species on both sides, only up to seven species actually crossed over from the Cretaceous. Even so the K-T event may not have influenced the gastropods as severely as many other fossil groups as the faunal changes among the gastropods were mainly on the species level. The turnover in the gastropod fauna can to a large degree be explained by a changing food supply as deduced by their feeding strategies. Thus the late Cretaceous fauna was characterized by a high diversity of detrital herbivores and suspension feeders, while the maximum diversity shifted towards hunting and grazing carnivores in the immediate Post-Cretaceous fauna. Surprisingly only small changes are observed with regard to the relative abundance of each of the different groups of feeding strategies. A possible explanation is that although the main food source for many detritivores/herbivores and suspension feeders, namely the primary producers, was severely hit by the K-T event, the total amount of food for these groups did not drop dramatically due to continued bacterial production at the sea floor. The diversity of the non-carnivores was furthermore strongly influenced by the disappearance of bryozoans, the main producers of hard substrates in the mud dominated environment preceding the boundary event in the Danish Basin. In contrast, this disappearance would make little difference to carnivorous gastropods. The increase in the diversity of carnivores is likely related to a relative increase in the main groups of prey such as echinoderms, sponges, gastropods and bivalves; although a delayed effect of the Late Cretaceous diversification of the carnivorous Neogastropods may have played in.| Period | 12 Jan 2010 |
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| Event title | Nordic Geological Winter Meeting |
| Event type | Conference |
| Conference number | 29 |
| Organiser | Norsk Geologisk Forening |
| Location | Oslo, NorwayShow on map |