Extinction and recovery patterns in benthic foraminiferal paleocommunities across the Cretaceous/Paleogene and Paleocene/Eocene boundaries

Abstract

In this thesis Late Cretaceous to Early Paleogene (66-54 Ma) benthic foraminiferal distribution patterns in the southern Tethys (northern margin of Africa) are discussed. We focus in particular on extinction and recovery patterns in middle neritic (50-100 m) to upper bathyal (200-600 m) benthic foraminiferal paleocommunities across the Cretaceous/Paleogene (KIP; 65 Ma) and PaleocenelEocene (PIE; 55 Ma) boundaries. The studied material is largely derived from the more or less well-known profiles of EI Kef (Tunisia), Gebel Duwi, Gebel Oweina, Wadi Nukhl (all Egypt), and Nahal Avdat (Israel). As in the recent situation, also Late Cretaceous to Early Paleogene communities were distinctly arranged along a depth gradient. Related gradients in nutrient supply (decreasing with depth), sea-floor oxygenation, and environmental stability (both generally increasing with depth) determined the major differences between the various neritic and bathyal habitats. Shallow water communities were often oligotypic and strongly dominated by only a few species, whereas upper bathyal communities consisted of a highly diverse mixture of deep and shallow water species. This study documents two major reorganizations of foraminiferal distribution patterns and paleocommunity composition, associated with important paleoceanographic and paleoclimatic events that coincided with the KIP and PIE transitions. During both "mass" extinctions all studied bathymetric compartments were affected, although to a variable extent: at the KIP boundary mainly the shallower domain was affected, whereas the deeper water assemblage was changing most across the PIE boundary. During both events the intermediate (upper bathyal) domain of the southern Tethys was severely perturbed; consequently, Late Cretaceous and early Eocene upper bathyal assemblages are very dissimilar, having few species in common.