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:

  • – microstructure I: silica cement and dominant quartz and feldspar grains,

  • – microstructure II: indistinct siliceous mass without agglutinated grains,

  • – microstructure III: abundant calcite cement, fine-grained texture, and grains selected for size and composition,

  • – microstructure IV: scarce calcite cement, a coarse-grained texture and non-selected grains.

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).

You do not currently have access to this article.