SYNONYMS: Sphagnum moss, horticultural peat, peat bog, humus peat, fen peatland, muskeg, organics, non-permafrost bogs.
COMMODITIES (BYPRODUCTS): horticultural peat, pollution control peat, filtration peat, energy (fuel) peat.
EXAMPLES (British Columbia – Canada/International): Burns bog, Pitt River bog, Fort Nelson Lowland peats, Peace River Lowland peats; Alberta, Quebec, New Brunswick, Ireland, Germany, Netherlands, Finland, Russia.
CAPSULE DESCRIPTION: Peatlands are classified into two categories: bogs and fens. Bogs receive their water only from precipitation and have low water flow, whereas fens are affected by mineral-rich ground and/or surface waters. Bogs have shallow water tables (generally about 50 cm below the peat surface). Land surfaces are generally poorly drained, level and may be slightly raised above the surrounding area. They may be treed. Peat bogs are acidic (pH below 4.5) and dominated by species of Sphagnum, feather moss, lichens, and ericaceous shrubs. Fens also have water tables at or just above surface and land surfaces are gently sloping to almost level. The vegetation is dominated by sedges, reeds, brown mosses, Sphagnum moss and ericaceous shrubs.
TECTONIC SETTING: Unimportant. Peat deposit formation is dependent largely on climatic and terrain conditions.
DEPOSITIONAL ENVIRONMENT / GEOLOGICAL SETTING: Peat deposits occur in topographic depressions often caused by melting ice in glacial tills or flat plains, usually overlying relatively impermeable materials, such as glaciolacustrine sediments and clay-rich tills. They are common in areas with poorly organized drainage systems and can occur locally on gentle slopes where precipitation is high and evaporation low. Stable regional water tables, anaerobic conditions and decreased nutrient availability are important for peat development. These factors lead to a substantial decrease in decomposition rates and a net accumulation of peat.
AGE OF MINERALIZATION: In Canada, most peatlands have formed since the end of the last ice age, about 13 000 to 10 000 years BP. Significant peat formation typically occurred after large areas that had been inundated by glacial lakes had drained, or after oceanic and lacustrine areas were uplifted by the postglacial isostatic rebound of the land. In British Columbia, peatland development was slow until after the warm and dry mid-Holocene period terminated around 4000 to 5000 years ago.
HOST/ASSOCIATED ROCK TYPES: Peatland. Associated sediments are marl deposits; organic-rich sediments; gyjatta; diatomaceous earth; overlie a variety of surficial deposits including clay till, glaciolacustrine and glaciofluvial sediments, ice contact deposits, and alluvium.
DEPOSIT FORM: Commonly, surface layers of weakly decomposed Sphagnum moss, up to several metres thick, are underlain by well decomposed sedge and/or Sphagnum peat, typically a few metres thick. In most deposits, the total depth of organic material is less than 10 metres. Some coalescing peat bogs can cover areas of several thousands of hectares in size.
TEXTURE/STRUCTURE: Peat is a soft, fibrous material with moisture content in its natural state of over 90%. Sphagnum moss has a high water-holding capacity (it can hold 15 to 20 times its weight in water), high cation exchange capacity, high pore space, low bulk density and high permeability.
ORE MINERALOGY (Principal and subordinate): Sphagnum peat, sedge peat, shrub and root fragments. There are about 85 species of Sphagnum known in North America.
GANGUE MINERALOGY (Principal and subordinate): Surface vegetation, stumps, sediment or marl interbeds.
ALTERATION MINERALOGY: Well decomposed sedge and/or brown peat moss (suitable as fuel peat).
WEATHERING: Decomposition of the organic matter is required to produce peat; various degrees of decomposition are preferred depending on the final product type.
ORE CONTROLS: The formation and localization of peat is a dynamic, continuous process, influenced by a number of factors, including climate and topography. The best quality Sphagnum peat develops as a slightly elevated dome that is raised above the water table. Boreal regions are the host of most peatlands in Canada.
GENETIC MODEL: Peatland formation is largely dependent on climatic and hydrogeologic factors. Peat accumulates in areas where water remains standing throughout the year due to a positive water balance. Organic material derived from vegetation builds up when the rate of accumulation is greater than the rate of decomposition. This balance is usually achieved in areas of temperate climate. Under higher temperatures, such as those in the tropics, vegetation growth is favoured but the rate of decomposition is rapid so that the accumulation of organic matter is low. Stabilized water levels, anaerobic conditions and decreased nutrient availability lead to a substantial decrease in decomposition rates, which results in the development of peat accumulating ecosystems. The rate of accumulation can be as much as 1-2 mm/year, but generally may average from 0.6-0.7 mm/ year in many Canadian peatlands.
ASSOCIATED DEPOSIT TYPES: Marl (B11), gyjatta, lacustrine diatomite (F06), glacial, glaciolacustrine and glaciofluvial sand and gravel deposits.
GEOCHEMICAL SIGNATURE: not applicable.
GEOPHYSICAL SIGNATURE: Ground penetrating radar has been used successfully in Sweden and Alaska to obtain three-dimensional pictures of peat bogs.
OTHER EXPLORATION GUIDES: Organic deposits occur in topographic depressions, along drainage ways, particularly on nearly level areas with poor drainage, and also on some slopes where precipitation is high and evaporation is low, such as northern coastal areas in BC. Air photo interpretation and remote sensing can identify peat landforms on the surface but ground truthing is needed to establish the subsurface nature of the deposit. Ground investigations include evaluations of surface vegetation, depth of the peat, Von Post degree of decomposition, size of the deposit, pH of the peat, botanical composition and identification of moss species present.
TYPICAL GRADE AND TONNAGE: Published data on individual deposits are rare, but according to Canadian Sphagnum Peat Moss Association, peat quality must meet market requirements regarding composition – the preferred composition is a weakly decomposed Sphagnum peat with a minimum content of shrubs and roots. The majority of producing sites have Sphagnum layers 1 to 4 metres thick. An aerial extent of 50 hectares is usually required, but some bogs may cover several thousands of hectares.
ECONOMIC LIMITATIONS: In North America, a thickness of 2 metres and an area of 50 hectares is generally considered the minimum for economic viability. The site must have good potential to build an enhanced drainage system, be close to infrastructure (particularly road access), and have a low-density tree cover. Local climate should have dry periods without much rain during the main harvest period.
END USES: Most of the peat is sold as compressed bales for use in the horticultural and nursery industries; some is used in soil mixes and other greenhouse and gardening products. Peat is important in environmental clean-up operations as absorbent and filtration media. Globally, about 13% is used as a fuel (e.g., in Russia, Finland, Ireland and Germany).
IMPORTANCE: In Canada, peatlands comprise over 12% of the land surface area, although much of this area is not viable for peat production. Less than 0.02% of the surface area of Canada has been used for peat production. Canadian peat production averages 700 000 to 800 000 tonnes annually with a value over $90 million/year. The main producing provinces are New Brunswick and Quebec, with Alberta ranked third. British Columbia’s peat production was from the Fraser delta, which was mined out in the 1970s. Peat in Canada is produced from 45 deposit areas in 8 provinces; most of the production is exported to the USA and overseas, particularly Japan. Because of a steady growth of peat in Canada's boreal regions, over 50 million tonnes of peat accumulates every year in Canada compared to 700 000 to 800 000 tonnes annually produced. Reclamation and restoration of mined-out areas can be accomplished by impeding the drainage. Experience from eastern Canada indicates that in 5 to 20 years (depending on local circumstances) the mined-out areas can be restored into ecologically balanced systems.
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Hood, G. (2001): The Canadian Peat Moss Industry; in Dunlop. S. and Simandl, G., Editors, Industrial Minerals in Canada, Canadian Institute of Mining, Metallurgy and Petroleum, Special Volume 53, pages 285–290.
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