geröllbank

A geröllbank is a geological formation consisting of a deposit of coarse-grained sediment, typically gravel and cobbles, accumulated in a river channel or along its banks. These deposits are a direct result of fluvial processes, where the energy of flowing water is sufficient to transport and deposit larger sediment particles. Geröllbanken are often found in braided river systems, where the channel frequently shifts and creates numerous depositional areas. They can also occur in more stable river systems as point bars or along the outer bends of meanders.

The composition and size of the clasts within a geröllbank are indicative of the source material and the transport history. The individual stones are usually rounded due to the abrasion that occurs during transport by water. The sorting of sediments within a geröllbank can vary, but they are generally characterized by a lack of fine-grained material like sand or silt, although some finer material may be interbedded.

Geröllbanken serve as important indicators of past hydrological conditions, reflecting the flow regime, sediment load, and geomorphic evolution of a river system. They can also play a role in local hydrology by influencing groundwater flow and providing habitat for certain plant and animal species. In some regions, geröllbank material has been historically used as aggregate for construction and road building. Their presence and characteristics are studied by geologists and geomorphologists to understand landscape development and river dynamics.