Benthic extinction and recovery patterns at the K/T boundary in shallow water carbonates, Denmark

Benthic extinction at the K/T boundary in the Danish Basin is abrupt and indistinguishable from the termination of Maastrichtian White Chalk deposition. The Danian benthic fauna — already fully established in the earliest Danian nannoplankton zone NP1 — is essentially an impoverished Maastrichtian fauna established through direct survival or limited evolution within well-established clades, already present in the Maastrichtian of the Danish Basin. However, recovery of the early Danian community is initially retarded. The transition is illustrated in some detail for the locality, Nye Kløv. Here the lower 2–3 m of Danian strata (corresponding largely to the lower NP1 subzone) contains an extremely impoverished, highly unusual, `dead zoneʹ community dominated by bourgueticrinid crinoids associated with other presumed soft ground specialists and devoid of such important faunal elements as cyclostome bryozoans, brachiopods, calcitic bivalves, etc. Over the next metres the `dead zoneʹ fauna is gradually replaced by more ordinary faunas, and about 6 m above the boundary the characteristic early Danian bryozoan limestone community is fully established.