Roca Formation (United States)

The Roca Formation is a geological formation located in the United States, primarily within southeastern Nebraska and northeastern Kansas. It is part of the Lower Permian Chase Group. The Roca Formation is characterized by its distinctive limestone beds, often exhibiting a mottled appearance due to variations in the composition and fossil content.

Geologically, the Roca Formation represents a shallow marine environment. The limestone is primarily composed of micrite (fine-grained calcite mud) and contains abundant marine fossils, including brachiopods, fusulinids, crinoids, and bryozoans. These fossils provide valuable information about the paleoecology and paleogeography of the region during the Permian Period.

The Roca Formation is significant for its role in understanding regional stratigraphy and correlation of Permian rock units. Its distinct lithology and fossil assemblages allow geologists to trace the unit across a wide geographic area. It is also of interest for its potential as a source of agricultural lime and building stone, although the economic importance is generally limited. The Roca Formation is typically underlain by the Towle Shale and overlain by the Grenola Limestone, both also part of the Chase Group.