AGGLUTINATED FORAMINIFERA FROM THE EPILIGURIAN SUCCESSION (MIDDLE EOCENE/LOWER MIOCENE, NORTHERN APENNINES, ITALY): SCANNING ELECTRON MICROSCOPIC CHARACTERIZATION AND PALEOENVIRONMENTAL IMPLICATIONS

Abstract

Two sections of Epiligurian sediments (Northern Apennines, Italy) covering the chronostratigraphic interval from the Middle Eocene to the Lower Miocene were analyzed for their foraminiferal content. Several specimens belonging to 25 selected species of agglutinated foraminifera were analyzed using the energy-dispersive x-ray spectrometry (EDS) method. The collected data show how these species are selective in composition, size, and shape of the agglutinated grains and cement composition. Test microstructures can be subdivided into four groups: A relationship between test microstructure and paleobathymetric conditions for the Monte Piano Marl, Ranzano Sandstone, and Antognola Marl Formations was observed. An almost exclusive presence of agglutinated taxa showing microstructures I and II characterized the “facies varicolori” of the Monte Piano Marls (lower-middle bathyal depths, from 2000 m to 1000 m). A sharp increase in species showing microstructures III and, subordinately, IV characterized the overlying lithostratigraphic units (“facies grigia” of the Monte Piano Marls, Ranzano Sandstones and Antognola Marls) whose paleobathymetry decreases upwards (middle-upper bathyal up to slope/shelf break from 1000 to 200 m).