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Geological Society, London, Special Publications; 1996; v. 102; p. 343-371;
DOI: 10.1144/GSL.SP.1996.001.01.26
© 1996 Geological Society of London

Cenozoic

Extinction and survivorship of southern Tethyan Benthic foraminifera across the Cretaceous/Palaeogene boundary

R. P. Speijer1,2 & G. J. Van Der Zwaan1

1 Department of Geology, Institute of Earth Sciences, Utrecht University, PO Box 80.021, 3508 TA Utrecht, The Netherlands
2 Department of Marine Geology, Earth Sciences Centre, Göteborg University, S-413 81 Göteborg, Sweden

The benthic foraminiferal record from the Cretaceous/Palaeogene boundary stratotype of El Kef, Tunisia, shows a succession of three distinct assemblages. The late Maastrichtian upper bathyal assemblage is highly diversified and shows no prominent signs of gradual change towards the boundary. The earliest Palaeocene is marked by the disappearance of more than 50% of the taxa, resulting in a strongly impoverished fauna, tolerant to low oxygen conditions and with a shallower water affinity. Sequential (re-) appearance of many taxa in the early Palaeocene signifies the restoration towards normal Palaeocene upper bathyal faunas. The faunal changes reflect major perturbations in redox and trophic conditions at the sea-floor.

At least locally, and perhaps even on a regional Tethyan scale, the extinctions can be related to a sharp decrease in oxygen supply, in combination with strongly reduced nutrient resources. It is suggested that a prolonged reduction in surface fertility and food flux to the sea-floor invoked worldwide (but diachronous) benthic extinctions. In particular endo-benthic deposit feeders and other taxa adapted to high and perhaps heterogeneous nutrient resources suffered extinction.