Tufa

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Tufa columns at Mono Lake, California Mono lake tufa.JPG
Tufa columns at Mono Lake, California

Tufa is a variety of limestone formed when carbonate minerals precipitate out of water in unheated rivers or lakes. 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. [1] It should not be confused with hot spring (thermogene) travertine. Tufa, which is calcareous, should also not be confused with tuff, a porous volcanic rock with a similar etymology that is sometimes also called "tufa".

Contents

Classification and features

Modern and fossil tufa deposits abound with wetland plants; [2] 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) [3] provide a review of tufa systems worldwide.

Barrage Tufa at Cwm Nash, South Wales Cwm Nash Barrage Tufa.jpg
Barrage Tufa at Cwm Nash, South Wales

Fluvial deposits

Deposits can be classified by their depositional environment (or otherwise by vegetation or petrographically). Pedley (1990) [4] provides an extensive classification system, which includes the following classes of fluvial tufa:

Rubaksa tufa plug, after drying of the river, in Ethiopia Rubaksa tufa plug.jpg
Rubaksa tufa plug, after drying of the river, in Ethiopia

Lacustrine deposits

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.

Calcareous sinter

Although sometimes regarded as a distinct carbonate deposit, calcareous sinter formed from ambient temperature water can be considered a sub-type of tufa.

Tufa deposits at Huanglong, Sichuan, China Huang Long Zheng Yan Chi (Huanglong Park).jpg
Tufa deposits at Huanglong, Sichuan, China

Speleothems

Calcareous speleothems may be regarded as a form of calcareous sinter. They lack any significant macrophyte component due to the absence of light, and for this reason they are often morphologically closer to travertine or calcareous sinter.

Tufa at Trona Pinnacles, California Trona Pinnacles - California.jpg
Tufa at Trona Pinnacles, California

Columns

Tufa columns are an unusual form of tufa typically associated with saline lakes. They are distinct from most tufa deposits in that they lack any significant macrophyte component, due to the salinity excluding mesophilic organisms. [3] Some tufa columns may actually form from hot-springs, and may therefore constitute a form of travertine. It is generally thought that such features form from CaCO3 precipitated when carbonate rich source waters emerge into alkaline soda lakes. They have also been found in marine settings in the Ikka fjord of Greenland where the Ikaite columns can reach up to 18 m (59 ft) in height. [5]

Biology

Tufa deposits form an important habitat for a diverse flora. Bryophytes (mosses, liverworts etc.) and diatoms are well represented. The porosity of the deposits creates a wet habitat ideal for these plants.

The Pyramid and Domes tufa rock structures, Pyramid Lake, Nevada Timothy O'Sullivan, The Pyramid and Domes, Pyramid Lake, Nevada, 1867.jpg
The Pyramid and Domes tufa rock structures, Pyramid Lake, Nevada

Geochemistry

Modern tufa is formed from alkaline waters, supersaturated with calcite. On emergence, waters degas CO2 due to the lower atmospheric pCO2 (see partial pressure), resulting in an increase in pH. Since carbonate solubility decreases with increased pH, [6] precipitation is induced. Supersaturation may be enhanced by factors leading to a reduction in pCO2, for example increased air-water interactions at waterfalls may be important, [7] as may photosynthesis. [8]

Recently it has been demonstrated that microbially induced precipitation may be more important than physico-chemical precipitation. Pedley et al. (2009) [9] showed with flume experiments that precipitation does not occur unless a biofilm is present, despite supersaturation.

Calcite is the dominant mineral precipitate, followed by the polymorph aragonite.[ citation needed ]

Tufa dam in Chelekwot, Ethiopia Tufa dam in Chelekwot.jpg
Tufa dam in Chelekwot, Ethiopia

Occurrence

Tufa is common in many parts of the world including:

National Park Krka Nacionalni park Krka, Roski slap (2023).jpg
National Park Krka

Some sources suggest that "tufa" was used as the primary building material for most of the châteaux of the Loire Valley, France. This results from a mis-translation of the terms "tuffeau jaune" and "tuffeau blanc", which are porous varieties of the Late Cretaceous marine limestone known as chalk. [11] [ need quotation to verify ] [12] [ failed verification ]

Dinaric karst watercourses

Uses

Tufa is occasionally shaped into a planter. Its porous consistency makes it ideal for alpine gardens. A concrete mixture called hypertufa is used for similar purposes.

Hollowed out portions of these tufa cliffs once formed back walls of rooms in a large prehistoric pueblo that stood here in Bandelier National Monument. Note outlines of masonry that were the outer portions of structure, and small holes in cliff that once supported ends of floor beams. Hollowed out portions of these tufa cliffs once formed back walls of rooms in a large prehistoric pueblo that stood here in (ac32d820d53b41ea98359a402b9fead5).jpg
Hollowed out portions of these tufa cliffs once formed back walls of rooms in a large prehistoric pueblo that stood here in Bandelier National Monument. Note outlines of masonry that were the outer portions of structure, and small holes in cliff that once supported ends of floor beams.

In the 4th century BC, tufa was used to build Roman walls up to 10m high and 3.5m thick. [13] The soft stone allows for easy sculpting. Tufa masonry was used in cemeteries, such as the one in Cerveteri. [14]

See also

Related Research Articles

<span class="mw-page-title-main">Limestone</span> Type of sedimentary rock

Limestone is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of CaCO3. Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place through both biological and nonbiological processes, though biological processes, such as the accumulation of corals and shells in the sea, have likely been more important for the last 540 million years. Limestone often contains fossils which provide scientists with information on ancient environments and on the evolution of life.

<span class="mw-page-title-main">Calcium carbonate</span> Chemical compound

Calcium carbonate is a chemical compound with the chemical formula CaCO3. It is a common substance found in rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skeletons and pearls. Materials containing much calcium carbonate or resembling it are described as calcareous. Calcium carbonate is the active ingredient in agricultural lime and is produced when calcium ions in hard water react with carbonate ions to form limescale. It has medical use as a calcium supplement or as an antacid, but excessive consumption can be hazardous and cause hypercalcemia and digestive issues.

<span class="mw-page-title-main">Mono Lake</span> Endorheic lake in California

Mono Lake is a saline soda lake in Mono County, California, formed at least 760,000 years ago as a terminal lake in an endorheic basin. The lack of an outlet causes high levels of salts to accumulate in the lake which make its water alkaline.

<span class="mw-page-title-main">Travertine</span> Form of limestone deposited by mineral springs

Travertine is a form of terrestrial limestone deposited around mineral springs, especially hot springs. It often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and rusty varieties. It is formed by a process of rapid precipitation of calcium carbonate, often at the mouth of a hot spring or in a limestone cave. In the latter, it can form stalactites, stalagmites, and other speleothems. It is frequently used in Italy and elsewhere as a building material. Similar deposits formed from ambient-temperature water are known as tufa.

<span class="mw-page-title-main">Plitvice Lakes National Park</span> National park in Croatia

Plitvice Lakes National Park is one of the oldest and largest national parks in Croatia. In 1979, Plitvice Lakes National Park was inscribed on the UNESCO World Heritage list, for its outstanding and picturesque series of tufa lakes, caves, and connected waterfalls.

<span class="mw-page-title-main">Speleothem</span> Structure formed in a cave by the deposition of minerals from water

A speleothem is a geological formation by mineral deposits that accumulate over time in natural caves. Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depending on their depositional history and environment. Their chemical composition, gradual growth, and preservation in caves make them useful paleoclimatic proxies.

<span class="mw-page-title-main">Portneuf River (Idaho)</span> River in Idaho, United States

The Portneuf River is a 124-mile-long (200 km) tributary of the Snake River in southeastern Idaho, United States. It drains a ranching and farming valley in the mountains southeast of the Snake River Plain. The city of Pocatello sits along the river near its emergence from the mountains onto the Snake River Plain.

<span class="mw-page-title-main">Dolomite (rock)</span> Sedimentary carbonate rock that contains a high percentage of the mineral dolomite

Dolomite (also known as dolomite rock, dolostone or dolomitic rock) is a sedimentary carbonate rock that contains a high percentage of the mineral dolomite, CaMg(CO3)2. It occurs widely, often in association with limestone and evaporites, though it is less abundant than limestone and rare in Cenozoic rock beds (beds less than about 66 million years in age). The first geologist to distinguish dolomite from limestone was Déodat Gratet de Dolomieu; a French mineralogist and geologist whom it is named after. He recognized and described the distinct characteristics of dolomite in the late 18th century, differentiating it from limestone.

<span class="mw-page-title-main">Mineral spring</span> Natural springs that produce water containing minerals

Mineral springs are naturally occurring springs that produce hard water, water that contains dissolved minerals. Salts, sulfur compounds, and gases are among the substances that can be dissolved in the spring water during its passage underground. In this they are unlike sweet springs, which produce soft water with no noticeable dissolved gasses. The dissolved minerals may alter the water's taste. Mineral water obtained from mineral springs, and the precipitated salts such as Epsom salt have long been important commercial products.

<span class="mw-page-title-main">Flowstone</span> Geological phenomenon

Flowstones are sheetlike deposits of calcite or other carbonate minerals, formed where water flows down the walls or along the floors of a cave. They are typically found in "solution caves", in limestone, where they are the most common speleothem. However, they may form in any type of cave where water enters that has picked up dissolved minerals. Flowstones are formed via the degassing of vadose percolation waters.

<span class="mw-page-title-main">Limescale</span> Hard, chalky deposit of calcium carbonate

Limescale is a hard, chalky deposit, consisting mainly of calcium carbonate (CaCO3). It often builds up inside kettles, boilers, and pipework, especially that for hot water. It is also often found as a similar deposit on the inner surfaces of old pipes and other surfaces where hard water has flowed. Limescale also forms as travertine or tufa in hard water springs.

<span class="mw-page-title-main">Calcareous</span> Adjective meaning mostly or partly composed of calcium carbonate

Calcareous is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.

<span class="mw-page-title-main">Ikaite</span> Hexahydrated calcium carbonate mineral

Ikaite is the mineral name for the hexahydrate of calcium carbonate, CaCO3·6H2O. Ikaite tends to form very steep or spiky pyramidal crystals, often radially arranged, of varied sizes from thumbnail size aggregates to gigantic salient spurs. It is only found in a metastable state and decomposes rapidly by losing most of its water content once removed from near-freezing water. This "melting mineral" is more commonly known through its pseudomorphs.

<span class="mw-page-title-main">Micrite</span> Limestone constituent formed of calcareous particles formed by the recrystallization of lime mud

Micrite is a limestone constituent formed of calcareous particles ranging in diameter up to four μm formed by the recrystallization of lime mud.

Calcareous sinter is a freshwater calcium carbonate deposit, also known as calc-sinter. Deposits are characterised by low porosity and well-developed lamination, often forming crusts or sedimentary rock layers. Calcareous sinter should not be confused with siliceous sinter, which the term sinter more frequently refers to. It has been suggested that the term "sinter" should be restricted to siliceous spring deposits and be dropped for calcareous deposits entirely.

<span class="mw-page-title-main">Calcite rafts</span> Cave-crystallized calcite crusts

Calcite crystals form on the surface of quiescent bodies of water, even when the bulk water is not supersaturated with respect to calcium carbonate. The crystals grow, attach to one other and appear to be floating rafts of a white, opaque material. The floating materials have been referred to as calcite rafts or "leopard spots".

<span class="mw-page-title-main">Microbiologically induced calcite precipitation</span> Bio-geochemical process

Microbiologically induced calcium carbonate precipitation (MICP) is a bio-geochemical process that induces calcium carbonate precipitation within the soil matrix. Biomineralization in the form of calcium carbonate precipitation can be traced back to the Precambrian period. Calcium carbonate can be precipitated in three polymorphic forms, which in the order of their usual stabilities are calcite, aragonite and vaterite. The main groups of microorganisms that can induce the carbonate precipitation are photosynthetic microorganisms such as cyanobacteria and microalgae; sulfate-reducing bacteria; and some species of microorganisms involved in nitrogen cycle. Several mechanisms have been identified by which bacteria can induce the calcium carbonate precipitation, including urea hydrolysis, denitrification, sulfate production, and iron reduction. Two different pathways, or autotrophic and heterotrophic pathways, through which calcium carbonate is produced have been identified. There are three autotrophic pathways, which all result in depletion of carbon dioxide and favouring calcium carbonate precipitation. In heterotrophic pathway, two metabolic cycles can be involved: the nitrogen cycle and the sulfur cycle. Several applications of this process have been proposed, such as remediation of cracks and corrosion prevention in concrete, biogrout, sequestration of radionuclides and heavy metals.

<span class="mw-page-title-main">Jvari Pass Travertine Natural Monument</span> Natural monument in Georgia

Jvari Pass Travertine Natural Monument is calcareous sinter or tufa in Baidara River valley on the left bank of the road tunnel of the Kobi-Gudauri motorway at 2197 meters above the sea level in Kazbegi Municipality, Georgia.

<span class="mw-page-title-main">Truso Travertines Natural Monument</span>

Truso Travertines Natural Monument is calcareous sinter or tufa in Truso valley on the right bank of Terek river at 2093 meters above the sea level in Kazbegi Municipality, Georgia. It is located about 2 km from village Keterisi where local population lives only seasonally.

<span class="mw-page-title-main">Molar tooth structure</span> Ribbon-like veins and nodules of calcite

Molar tooth structures are ribbon-like veins and nodules of calcite that are found widespread in Precambrian carbonate sedimentary rocks between approximately 2600 to 570 million years ago. Their mechanism for formation remains debated, with hypothesis including the generation of methane gas within sediments, pumping of water through sediment by wave action, tsunamis, and bacterial processes.

References

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  2. Koban, C.G.; Schweigert, G. (1993). "Microbial origin of travertine fabrics - two examples from Southern Germany (Pleistocene Stuttgart travertines and Miocene riedöschingen Travertine)". Facies. 29: 251–263. doi:10.1007/BF02536931. S2CID   129353316.
  3. 1 2 Ford, T.D.; Pedley, H.M. (1996). "A review of tufa and travertine deposits of the world". Earth-Science Reviews. 41 (3–4): 117–175. Bibcode:1996ESRv...41..117F. doi:10.1016/S0012-8252(96)00030-X.
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  5. Buchardt, B.; Israelson, C.; Seaman, P.; Stockmann, G. (2001). "Ikaite tufa towers in ikka fjord, southwest Greenland: their formation by mixing of seawater and alkaline spring water". Journal of Sedimentary Research. 71 (1): 176–189. Bibcode:2001JSedR..71..176B. doi:10.1306/042800710176.
  6. Bialkowski, S.E. 2004. "Use of Acid Distributions in Solubility Problems". Archived from the original on 2009-02-28.{{cite web}}: CS1 maint: numeric names: authors list (link)
  7. Zhang, D.; Zhang, Y; Zhu, A.; Cheng, X (2001). "Physical mechanisms of river waterfall tufa (travertine) formation". Journal of Sedimentary Research. 71 (1): 205–216. Bibcode:2001JSedR..71..205Z. doi:10.1306/061600710205.
  8. Riding, R. (2000). "Microbial carbonates: the geological record of calcified bacterial-algal mats and biofilms". Sedimentology. 47: 179–214. doi:10.1046/j.1365-3091.2000.00003.x. S2CID   130272076.
  9. Pedley, M.; Rogerson, M.; Middleton, R. (2009). "Freshwater calcite precipitates from in vitro mesocosm flume experiments: a case for biomediation of tufas". Sedimentology. 56 (2): 511–527. Bibcode:2009Sedim..56..511P. doi:10.1111/j.1365-3091.2008.00983.x. S2CID   129855485.
  10. Ascione, Alessandra; Iannace, Alessandro; Imbriale, Pamela; Santangelo, Nicoletta; Santo, Antonio (February 2014). "Tufa and travertines of southern Italy: deep-seated, fault-related CO 2 as the key control in precipitation". Terra Nova. 26 (1): 1–13. doi:10.1111/ter.12059.
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  13. Devereaux, Bret (2021-11-12). "Collections: Fortification, Part II: Romans Playing Cards". A Collection of Unmitigated Pedantry. Retrieved 2023-09-15.
  14. Marini, Elena (January 2010). "A Study of the Architectonic Development of the Great Funerary Tumuli in the Etruscan Necropolises of Cerveteri". Etruscan Studies. 13 (1). doi:10.1515/etst.2010.13.1.3. ISSN   2163-8217.