A first glimpse on the taphonomy and sedimentary environment of the Eocene siliceous sponges from Chiampo, Lessini Mts, NE Italy

A diverse assemblage of bodily preserved sponges has been recovered from a lower Lutetian tuffite horizon in the Chiampo Valley, Lessini Mountains, Italy. The sponge assemblage is dominated by hexactinellids and lithistids. Using uniformitarian criteria, the composition of the assemblage suggests a water depth greater than 200 m. Sponges are often preserved in growth position including sponge clusters. Taphonomic processes facilitating sponge preservation include rapid burial of a living sponge community and early diagenetic calcification. Different modes of attachment suggest heterogeneous substrate conditions. The associated fauna, such as abundant pteropods in the matrix and in-situ preserved crinoids, confirms a rather deep-water environment. However, there are also common benthic elements of shallow-water origin. Although some of these elements show signs of transport, others, such as decapod crustaceans, do not. Moreover, trace fossils indicate high-energy environments. To reconcile these observations, we propose rapid, tectonically triggered sea-level changes.