A Waulsortian mudmound is a calcareous geographical feature found in Early Carboniferous strata of Central Europe.
It is a type of fossil-rich bioconstruction, formed by microbial activity in deep tropical waters during the mid-Dinantian (late Tournaisian to early Viséan geological age).
Unlike a true reef, a mud mound is composed almost entirely of uncemented mud-sized matrix grains, and the isolated fossils do not form a significant skeletal framework.
In the mudmound one finds fossils of the crinoids bone structure and the angle of deposit shows the direction and speed of mudflow.
They include accessible geological sites at Clitheroe Castle, Salthill and Bellman quarries, Crow Hill and Worsaw, Gerna and Sykes.