Abstract

Stacked, steep-sided algal mounds are well exposed within the Upper Paleozoic Auernig Group and Lower Pseudoschwagerina Limestone of the Carnic Alps on the Italian-Austrian border. Individual mounds are up to 22 m thick and 60 m long. They are composed of a nearly monospecific association of the dasycladalean Anthracoporella, typically in growth position. Anthracoporella built a delicate framework as indicated by dense, often erect, and unbroken thalli and cavities between algal thalli that are filled by lime mud, synsedimentary cements, micritic crusts, and/or peloids. Microfacies contrasts between mound and inter-mound are striking. The mound core is composed of Anthracoporella boundstone. The intermound areas are composed of bioclastic wackestone-packstone with rare Anthracoporella. Mound development occurred below storm wave base in a quiet environment. Anthracoporella mounds differ from contemporaneous phylloidalgal mounds in their unique delicate skeletal framework and in the very low export of algal thalli to the surrounding sediments.

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