BENTHIC FORAMINIFERAL BIOFACIES IN TEMPERATE CARBONATE SEDIMENT IN THE WESTERN PONTINE ARCHIPELAGO (TYRRHENIAN SEA, ITALY)

Recent foraminiferal assemblages are identified in 70 grab samples from 20-380 m depth in the Pontine Archipelago (Tyrrhenian Sea, Italy). All broken and relict tests of benthic foraminifera and other bioclastic sediments were counted for each sample, in order to provide a more complete description of the benthic community. Hierarchical cluster analysis (HCA) was performed on the relative abundances (live + dead) of 53 taxa of benthic foraminifera that were common in the samples. Q-mode HCA recognizes three distinct foraminiferal biofacies, each associated with a particular bioclastic lithofacies: 1) the Asterigerinata-Lobatula-Rosalina biofacies occurs at 20-150 m and is dominated by benthic foraminifera, most notably epiphytic species such as Asterigerinata mantilla, Lobatula lobatula, and Rosalina brad vi; other bioclasts include rhodoliths, bryozoans, and echinoid spines, which constitute the rhodalgal lithofacies; 2) the Cassidulina carinata biofacies at intermediate depths of 100-250 m includes benthic and planktonic foraminifera among branches of bryozoans that constitute the bryomol lithofacies; also present are high percentages of reworked glauconitic tests of shallow-water taxa (e.g., Elphidium, Lobatula, and Asterigerinata), possibly related to Late Quaternary sea-level stillstands; 3) the Uvigerina-Bulimina biofacies at 200-380 m, that is characterized by Uvigerina mediterranea and Bulimina marginata; in addition to benthic and planktonic foraminifera, it has a molechfor lithofacies of bivalves and gastropods.