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A nice example of transgression referring to the passage lower Oligocene-middle Oligocene (around 28 millions years) can be found in Maddalena-Ponte Prina site; its earliest marine sediments are generally made up of coral bio constructions lying down directly on the serpentinites of the substratum clearly shaped by the sea action. Silicoclastic coarse deposits subsequently suffocated these bio constructions. The subsequent levels represent a phase of gradual deepening as evidenced by both the coral fauna and the macroforaminifers and molluscs.
The site is very interesting for the evident presence of coral colonies in good state of preservation, often in living position and of big dimensions; these characteristics, coupled with the excellent exposition and the positive action of the superficial outwash, make it one of the most significant deposits of oligocenic coral fauna in northwestern Italy. They are mainly massive forms (Michelottiphyllia, Stylocoenia, Hexastrea, Favia, Actinacis, Antiguastrea, Astreopora, Diploria e Cyatoseris) and more rarely (always fragmented) branchy forms (Stylophora).
In the middle-higher part of the sequence there are many easily detectable macroforaminifers (Nummulites and lepidocyclinidic) and red calcareous algae (Corallinales) both encrusting and as oncolithes, besides the more rare remains of bivalves, gastropods, echinoids, serpulides and bryozoae.
