Lunulite bryozoans from Early Pleistocene deposits of SW Umbria (Italy): sedimentological and paleoecological inferences

Abstract

The occurrence of lunulite bryozoan assemblages in the Early Pleistocene of western Umbria, central Italy, is documented for the first time. Six species within the genera Reussirella, Cupuladria, and Discoporella were recovered. Study sections encompass a wide range of marine coastal deposits varying from beachface to offshore, which developed in the area during the Early Pleistocene (Gelasian to Calabrian) and were locally influenced by river supply. Lunulite bryozoans mainly occur in infra- to circalittoral, bioclastic-rich sand to mud sediments deposited in locally vegetated paleoenvironments, characterized by moderate to low energy and ranging from lower shoreface to offshore. Based on grain-size analysis, coupled with evidence from benthic foraminiferan and mollusc associations, a main bathymetric range of 10–60 m can be inferred for lunulite distribution in the area, with a prevalence in the 30–50-m interval and a subordinate presence down to about 120 m. Lunulite growth was here also conditioned by a warm climate and a temporarily high sedimentation rate.