This Fairmont deposit is unusual compared to most of the fossil dominated spring deposits in the Canadian Rocky Mountains because of the abundance of abiotic facies. It also differs from Mammoth with the lack of massive bacterial shrubs, except in one small area. Abiotic conditions include light, temperature, water, soil. Biotic describes a once living component such as plants and animals.
The triangle apron shaped carbonate deposit covers an area of 1/2 square kilometer and is up to 16 m thick, over an elevation change of 150 m. It is approximately 700 m by 700 m. The exposed deposit in Nahanni National Park was previously thought to be the largest but it is only a diameter of 79 m. Most of the Fairmont deposit is covered by fluvial deposits, soil, vegetation and the Fairmont Resort development.
Although the creek was active at the time of the deposit the Fairmont Creek Valley was not yet incised. The diagram below illustrates the changes and time periods involved. The Fairmont Springs are sandwiched between two thrust faults, namely the Purcell and the Redwall which are about 20 K apart. The spring water emerges at the intersection of two unnamed faults. .
The vents responsible for this deposit are no longer exposed although this zone of thermal springs starts around the top of the apron with the main vent outside the apron and two other vents are also noted in the diagram. Note that the calcium deposits seen near the vents are recent modern deposits that were formed after the apron's relict deposit was formed. Nearby Lussier Hot Springs do not contain carbonate deposits, possibly as the vent is too close to the river.
This calcium carbonate apron is composed of Travertine (abiotic) and Tufa (biotic) which are almost in equal proportions from the same parent spring water which had the same chemistry and temperature. They formed differently due to different conditions. Tufa has generally been described as being formed from cold water; whereas travertine has been described as from hot water deposits. There is little evidence indicating that water temperature exerted any control for this deposit. It appears that the interaction between hydrodynamics, calcite precipitation rates and biotic growth rates determined the resulting carbonate form.
Tufa, because of its soft porous nature has been used in landscaping projects and can be seen at some garden markets and some Tufa from BC has been shipped to Arizona! The Romans used it extensively for buildings and bridges. The Servian Wall built in the 4th century to protect Rome was built almost entirely of Tufa. This calcium carbonate is formed from low to moderately saturated spring water on the flatter sections during high flow rates and on hillier areas during low flow water rates.
Travertine derives its name from an old Roman town Tibor and was used to build the colonnades at St Peters, because of its non porous nature although it is pitted. This calcium carbonate was formed from highly supersaturated solutions usually close to source of the spring. It has formed huge natural dams and waterfalls.
Photographs of deposits at N 50 19.700 W 115 50.905. A visit to this little canyon is well worth the drive or hike.
Despite the crucial role of the interactions between abiotic and biotic controls in forming carbonate spring deposit formations, much remains unknown over these formations and exactly how they interacted in their delicate balance of conditions..
To really appreciate this deposit take a stroll around the area and do not miss out on the Fairmont Creek pathway which was the scene of the massive earth slide on July 15, 2012 and also illustrates the depth of this deposit.
Acknowledgements and thank you for data and drawings to: Dustin K. Rainey, University of Alberta;
To log this Earthcache, please email the owner with the following: a) the height of the modern deposit at the Emanation Hill, which is to the east of ground zero b) compare the appearance of relic deposits to the modern deposit coming down the hill c) how important a role did the cyclical nature of the weather play in the formation of this deposit? d) Comment on the differences between abiotic and biotic controls over the development of this carbonate deposit.
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