A carbonate mud mound is a sediment body consisting of structureless or crudely bedded fine crystalline carbonate. Modern examples of carbonate mud mounds are rare.
Many mounds are made of the remains of microbes that had calcareous structures and these microbes grew in place to build up the body of sediment.
Others have a large component of detrital material, again mainly the remains of algae and bacteria, which have been piled up into a mound of loose material.
It is also possible that some skeletal organisms such as calcareous sponges and bryozoans are responsible for building carbonate mud mounds.