Eocene/oligocene deep-water agglutinated foraminifers (DWAF) assemblages from the Madonie Mountains (Sicily, Southern Italy)

Abstract

Quantitative and qualitative analysis of deep-water agglutinated foraminifer (DWAF) assemblages from Portella Colla (Madonie Mts.) reveal a variation of the trophic continuum in late Eocene and early Oligocene times. Twenty-nine samples were processed obtaining 138 agglutinated species, 59 of which are in open nomenclature, belonging to 46 genera attributed to four functional morphogroups according to their life position and feeding strategies. Faunal density increases upsection, whereas specific diversity fluctuates and reaches its minimum within the E/O transition. In the uppermost Eocene, cyclamminids, Haplophragmoides and Repmanina charoides, epifaunal and lower infaunal forms which prefer well-oxigenated bottom water and a normal food supply, prevail. Within the E/O transition the DWAF abundance broadly decreases and the assemblages are dominated by opportunistic taxa such as Repmanina charoides. In the lower Rupelian, suspension-feeders and assemblages rich in Paratrochamminoides are present, and hyaline taxa disappear. At the end of the lower Rupelian, Nothia, ammodiscids and hyaline foraminifers reappear, and deep infaunal morphogroup becomes dominant marking low-oxygen bottom water conditions. In the upper Rupelian, deep infaunal communities (rheophacids and Caudammina) dominate the assemblages, and epifaunal surface-dwelling foraminifers decrease. The LO of Caudammina gutta coincides with an increase in sand deposition (transition from Caltavuturo Fm. to Portella Colla Clays), a decrease in suspension feeders and surfacedwellers, and the dominance of oligotypic assemblages by Reticulophragmium rotundidorsatum. The oxygenation of bottom waters return to levels similar to those of the upper Eocene, with a medium to high nutrient supply as inferred from the abundance of cyclamminids.