Original paper

The response of benthic foraminifera to palaeoenvironmental disturbance: A quantitative approach in turbidite-like successions

Drinia, Hara; Dermitzakis, Michael D.

Abstract

Benthic foraminifera were collected from a number of samples of a turbidite-like succession, and quantitatively investigated with the aim to describe and interpret their distributional pattern prior, during and after the turbidite events. The foraminiferal assemblages contain indigenous benthic taxa that represent combined bottom-water and bottom-sediment controlled benthic environments and allochthonous benthic shelf taxa that are transported downslope into deeper-water biotopes. Considerable differences in diversity, community organization, feeding and habitat preferences are detected among benthic foraminiferal assemblages below, across and above the turbiditic episodes. Prior to the deposition of the turbiditic sands, the benthic foraminiferal assemblage is indicative of a strong preference of environments with highly elevated food supply, but sheltered from direct disturbance. This stability was disrupted by the recurrent deposition of turbiditic sands. In the lower part of the turbiditic sequence, some specialized endobenthic forms, such as Valvulineria complanata and Nonion spp. could keep pace with high sedimentation reflecting enhanced supply of organic matter by transport. In the upper part of the turbiditic sequence, an opportunistic fauna (Bolivina spathulata assemblage), entirely composed of infaunal elements, is observed, indicating a nutrient-rich substrate. The reduction in the dominance of Bolivina spp. and the reappearance of both infaunal and epifaunal taxa reflects the recovery of the benthic ecosystem.

Keywords

early tortonianbenthic foraminiferaturbiditesecosystem disturbancerepopulation