Speleogens

Speleogens are natural rock formations that protrude into the void of a cave. They are created by the dissolution and differential erosion of soluble bedrock during cave development, such that harder or less-dissolved rock remains as the surrounding material is removed by groundwater flow. The resulting features include ridges, fins, spires, and grooves that project into the cave space on walls, floors, or ceilings. Speleogens form as dissolution follows fractures, bedding planes, and the walls of conduits, producing a relief pattern that records the geometry of the rock fabric and the flow paths of the dissolving water.

Speleogens are most common in karst landscapes developed in limestone, dolostone, gypsum, or other soluble rocks. They can reflect epigenic speleogenesis (water entering from the surface) or hypogenic processes (water rising from the subsurface) and are often used to infer the paleohydrology and fracture architecture of a cave system. Their preservation or destruction can indicate subsequent changes in drainage or cave enlargement.

In contrast, speleothems are mineral deposits formed by secondary precipitation, such as stalactites and stalagmites, and they occupy the void after the rock has been dissolved away. Speleogens, by defining the bedrock framework of a cave, are fundamental to understanding cave morphology and development.