The anisian (middle triassic) carbonate bank of Camorelli (Lombardy, Southern Alps)

Abstract

During the Anisian (?Bithynian to Pelsonian) a large carbonate bank, up to 400 m thick, (the Camorelli Limestone) developed in the Lombardian Alps. Many stratigraphic sections were measured in this unit and three basic microfacies were detected, often arranged in sequence from bottom to top: intrabioclastic packstone, bindstone, and bioclastic packstone rich in Foraminifera. The biofacies is dominated by blue-green algae (Spongiostromata and Porostromata) and microproblematicTubiphytes. Benthic Foraminifera are subordinate even if they become locally the main bioclastic component. Dasycladacean algae are rare. These rather undifferentiated microfacies strongly contrast with time-equivalent mound microfacies, as previously pointed out for mounds versus large carbonate bank in the Illyrian. These features can be connected with substratum competition, not fully suitable for sponges in shallower environment at this stage of the Triassic recovering after the Late Permian crisis.