The Cretaceous-Tertiary (K-T) mass extinction in planktic foraminifera at Elles I and El Melah, Tunisia

Planktic foraminiferal faunas across the K-T transition at Elles and El Melah in northwestern and northeastern Tunisia, respectively, reveal patterns of species extinctions and species survivorship similar to those found at the El Kef stratotype and the Ain Settara sections. Slightly more than 2/3 of the species disappeared at or before the K-T boundary event and slightly less than 1/3 survived into the Danian where most disappeared sequentially within zone Pla (Parvularugoglobigerina eugubina). Relative species abundance patterns reveal that the 13-16 K-T survivors dominated (80%) the assemblages in the latest Maastrichtian, whereas the K-T extinct species were rare and totaled less than 20% of the total assemblages. The K-T survivors are generally small with little surface ornamentation and geographically widespread from low to high latitudes. In contrast, K-T extinct species are large, highly ornamented and geographically restricted to low latitudes. This indicates that the K-T mass extinction was selective, rather than random, and predominantly affected the less robust tropical species. With the exception of the opportunistic Guembelitria species which dominate the early Danian, most K-T survivor species suffered severely as is evident by the decreased species populations after the K-T event. Their eventual demise appears to have been related to post-K-T environmental changes and competition from evolving Tertiary species. These results reveal a complex mass extinction pattern that in addition to the K-T impact event is keyed to long-term environmental changes preceding and following this event.