The effects of Oligocene paleoclimatic and paleoenvironmental events at lower latitudes have not been well defined, and the timing and extent of a proposed warming period in the late Oligocene are not clear. The study of benthic foraminifera from the upper bathyal Fuente Caldera section in southern Spain may help reconstruct the Oligocene paleoenvironmental turnover in the western Tethys. Rupelian and Chattian sediments from Fuente Caldera consist of hemipelagic marls intercalated with turbiditic sandstones. Based on a closely spaced sample collection, we present a quantitative analysis of benthic foraminiferal assemblage changes, and a detailed taxonomic study of 19 of the most abundant and paleoenvironmentally important species, belonging to the asterigerinids, rosalinids and bolivinids.
The Fuente Caldera sediments contain abundant reworked neritic foraminifera (asterigerinids, rosalinids, Cibicides spp.), including epiphytes and species that commonly bear symbionts or kleptochloroplasts from the photic zone, that may have been transported downslope by turbidity currents or attached to floating plant material. The high relative abundance of bolivinid taxa in the autochthonous assemblages suggests a high food supply, probably at least in part consisting of refractory organic matter supplied by downslope turbidity currents. The benthic foraminifera indicate that water temperatures were several degrees warmer than today, as inferred from the common occurrence of warm-water taxa such as Nodobolivinella jhingrani, Rectobolivina costifera or Tubulogenerina vicksburgensis. Nevertheless, further paleotemperature studies are needed to test our conclusion that warm conditions prevailed in this part of the western Tethys during the Oligocene, even during colder intervals (Oi-events).