page_title: Tufa
section_title: Fluvial deposits
hierarchical_section_title: Tufa / Classification and features / Fluvial deposits
caption_attribution_description: English: Rubaksa tufa plug in Ethiopia.
context_page_description: Tufa is a variety of limestone formed when carbonate minerals precipitate out of ambient temperature water. Geothermally heated hot springs sometimes produce similar carbonate deposits, which are known as travertine. Tufa is sometimes referred to as travertine. It should not be confused with hot spring travertine. Tufa, which is calcareous, should not be confused with tuff, a porous volcanic rock with a similar etymology that is sometimes also called "tufa".
context_section_description: Deposits can be classified by their depositional environment (or otherwise by vegetation or petrographically). Pedley (1990) provides an extensive classification system, which includes the following classes of fluvial tufa:
  Spring – Deposits form on emergence from a spring/seep. Morphology can vary from mineratrophic wetlands to spring aprons (see calcareous sinter)
  Braided channel – Deposits form within a fluvial channel, dominated by oncoids (see oncolite)
  Cascade – Deposits form at waterfalls, deposition is focused here due to accelerated flow (see Geochemistry)
  Barrage – Deposits form as a series of phytoherm barrages across a channel, which may grow up to several metres in height. Barrages often contain a significant detrital component, composed of organic material (leaf litter, branches etc.).
caption: Rubaksa tufa plug, after drying of the river, in Ethiopia
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