Tufa

Tufa is a variety of limestone formed when carbonate minerals precipitate out of ambient temperature water. Geothermally heated hot springs sometimes produce similar (but less porous) carbonate deposits, which are known as travertine. Tufa is sometimes referred to as (meteogene) travertine. It should not be confused with hot spring (thermogene) 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'. Tufa is a variety of limestone formed when carbonate minerals precipitate out of ambient temperature water. Geothermally heated hot springs sometimes produce similar (but less porous) carbonate deposits, which are known as travertine. Tufa is sometimes referred to as (meteogene) travertine. It should not be confused with hot spring (thermogene) 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'. Modern and fossil tufa deposits abound with wetland plants; as such, many tufa deposits are characterised by their large macrobiological component, and are highly porous. Tufa forms either in fluvial channels or in lacustrine environments. Ford and Pedley (1996) provide a review of tufa systems worldwide. 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: Lacustrine tufas are generally formed at the periphery of lakes and built-up phytoherms (freshwater reefs), and on stromatolites. Oncoids are also common in these environments.