A model for the palaeoenvironmental distribution of larger foraminifera based on late Middle Eocene deposits on the margin of the South Pyrenean basin (NE Spain)

On the margin of the South Pyrenean basin, the late Middle Eocene sediments represent a well preserved regressive system permitting determination of the distribution of larger foraminifera along the depth gradient. Eocene deposits are compared with distribution patterns of Recent larger foraminifera based on taxa occupying comparable positions along similar ecological gradients. Eocene taxa reveal by their test morphology a similar response to specific ecological conditions to that recorded for Recent foraminifera. Four assemblages characterise an open marine shelf; they range from the lower limit of the photic zone to the lower part of the upper photic zone. Two assemblages characterise the upper part of the upper photic zone, and indicate, respectively, two different substrates, firm or soft. Below the photic zone, no larger foraminifera exist and the foraminiferal assemblages are dominated by smaller benthic foraminifera.