摘要：A crustose coralline algal pavement, identified in Upper Eocene (Priabonian) shallow water, middlerampcarbonates in north-eastern Italy (Colli Berici, Southern Alps), represents a rare example of this facies.The crustose pavement consists of a coralline crust bindstone with a wackestone-packstone matrix, and ischaracterised by the dominance of crustose coralline thalli composed primarily of melobesioids (Lithothamnionand Mesophyllum) and mastophoroids (Spongites, Lithoporella, Neogoniolithon). In places the corallinebindstone can be seen to develop from isolated encrusting-to-foliose thalli which bifurcate and join to forman open framework interbedded with matrix debris from crusts. Various forms of rhodoliths occur commonlywithin this facies. The largest discoidal rhodoliths (up to 12 cm of large diameter) show an inner arrangementconsisting of loosely packed laminar (encrusting-to-foliose) coralline thalli with a high percentage ofconstructional voids (50-63%). Accessory components are represented by larger hyaline perforated foraminiferasuch as nummulitids and orthophragminids. This facies formed in a ramp palaeoenvironment characterised byrelatively low hydrodynamic energy and low rates of sedimentation. Channelised structures present within thefacies were formed by return currents which swept the middle ramp creating such distal structures. Furthertoward the distal middle-ramp the return currents decreased in energy and discharged nutrients allowing themesotrophic crustose coralline algal pavement to develop.
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