The generation of benthic foraminiferal fossil assemblages from living communities: Preservation potential of different microhabitats

Benthic foraminiferal fossil assemblages within upper sediment layers on the ocean floor (the thanatocoenosis) often differ from the living community (the biocoenisis). This distinction is due to differences in species production and preservation among microhabitats occupied by the foraminifera. I investigated foraminiferal production and preservation using a transect of sites on the western European margin of Fram Strait in the North Atlantic. The primary variable on this transect was changing organic carbon flux to seabed. The foraminiferal living community was documented using Rose Bengal and Cell Tracker Green staining. Pore-water geochemical profiles (oxygen and carbon isotopes) were measured to quantify seabed geochemical conditions.;Results presented here include both surficial and infaunal microhabitats across a range of organic carbon fluxes to the seabed. Individual species often live over a range of sediment depths within the habitation zone, and distribution is linked to biostructures in the sediments. By using abundance profiles of empty shells of individual species through the sediment taphonomic zone what the most preservable material for each taxon was determined for each microenvironment. The abundance profiles show both the sediment intervals where each species adds shells to seabed sediments, and also the degree to which shells undergo taphonomic elimination. Importantly, the transformation of a living community into a fossil assemblage was determined.;In none of the settings were taxa observed with constant profiles in the upper five centimeters of the sediment column. In Kongsfjord, total shell abundances had a strong gradient in the surficial oxic layer, but stable abundances below that. On the continental slope, taxa show high abundances in the near subsurface, and decreasing abundances downcore. In Fram Strait, the abundance profiles show abundance increases deeper in the sediment mixing-zone. The conclusions are that the generation of the fossil assemblage is a balance between shell production and destruction.