Reef knoll

A reef knoll is a landform that comprises an immense pile of calcareous material that had previously accumulated on an ancient sea floor.

Reef knolls are often fossil-rich, with prehistoric corals, sponges, calcareous algae, and other reef-builders contributing to a large portion of the structure's volume.

This density of skeletal material allows the structure to withstand sea currents and stand freely.

[3] Krumbein additionally used these terms to distinguish different shapes of stromatolites: "Distinctly bedded, widely extensive, blanketlike build-ups are biostromes.

Examples in the Yorkshire Dales[5] lie on the downthrow side (north) of the Mid Craven Fault.