Depending on their areal extent and thickness, the accumulation of encrinites can be subdivided into either "regional encrinites" A regional encrinite is an extensive accumulation of limestone that is at least 50%
pelmatozoan ossicles at least thick and has an areal extent of at least . By definition, crinoid ossicles are the predominate component of encrinites. However, the ossicles of other pelmatozoans, e.g., rhombiferans or diploporans during the
Ordovician and
Silurian or
[blastoids during the Lower
Mississippian, can locally be the predominate
bioclast. The classic example of an encrinite is the
Burlington and
Keokuk limestones of
Iowa,
Missouri, and
Illinois. Additional examples of
geologic formations that contain regional encrinites are the Lower
Muschelkalk,
Switzerland (
Triassic);
Redwall Limestone,
Arizona (
Mississippian);
Coeymans, Keyser, and
New Creek limestones,
Pennsylvania (
Devonian);
Edgecliff Limestone,
New York (Devonian);
Brassfield Formation,
Ohio (
Silurian); and
Chicotte Formation,
Anticosti Island,
Quebec (Silurian). Regional encrinites are only found in the stratigraphic record from the Ordovician through the Jurassic. They are most abundant in Lower Mississippian strata. Encrinites which do not meet the criteria of regional encrinites are termed local encrinites. They typically occur as individual lenses or beds thick of very limited lateral extent. Regional encrinites accumulated where the offshore continental shelf was nearly completely dominated by crinoids (and in some cases other stalked echinoderms) for extensive periods of time. At the time of the accumulation of encrinites, the seafloor of the shallow continental sea consisted entirely of a coarse, poorly sorted pelmatozoans bioclasts lying within the storm-wave base. Because of the low-density and coarse nature of these bioclasts, the sea floor was episodically mobile during periodic storms. This made the sea floor an unfavorable habitat for most non-pelmatozoan benthic organisms. However, this type of seafloor was it was well suited for pelmatozoans to anchor their rhizoid holdfasts. This created a positive taphonomic feedback in which the disarticulation of pelmatozoans provided abundant bioclastic debris that created a seafloor that encouraged the establishment and growth of pelmatozoans, but discouraged the establishment and growth of other benthic organisms. ==Distribution==