Brantford Tufa Mounds Earth Science ANSI
Another distinctive landscape feature in this area is the Tufa Mounds Provincially Significant Earth Science Area of Natural and Scientific Interest [ANSI], located in northwest Brantford.
Tufa is a variety of limestone formed when calcium carbonate minerals from ground water springs precipitate out of ambient temperature water. Geothermally heated hot springs sometimes produce similar (but less porous) carbonate deposits known as travertine. Tufa is sometimes referred to as travertine. Tufa from cold water springs are considered rare in Canada.
The Brantford ANSI received its designation as a result of a peer review done in January 2005. The site is on private land and is adjacent to a provincially significant wetland (PSW) located within a former channel of the Grand River. The ‘tufa mounds’ at Brantford are fossil forms, having been deposited in early postglacial times, and not presently active. They are not bedrock features as the bedrock surface lies up to 50 m below the surface at this location. They are probably not of pre- or inter-glacial origin as the tufa is very weak and would have been removed by subsequent glaciations. Hence, they must have formed after the Wisconsin glacier retreated eastward from the Moffat Moraine position. The tufa mounds indicate that at the time of formation, groundwaters rich in CaCO3, were under artesian conditions that raised at least up to about 2 m above the river level at this location, hence the “mounds”.
The local area was a site of gypsum mining done for land plaster (fertilizer) by local farmers. Residents have known and have studied these abandoned shafts that occur in the valley walls of the Grand River near Paris. The book ‘Herons and Cobblestones’ was published by the Grand River Heritage Mines Society and records the history of the mines in the area. Northwest Brantford is also associated with karst topography which is formed from the dissolution of soluble rocks such as gypsum, limestone and dolomite and may be characterized by underground drainage, sinkholes, disappearing streams and reappearing springs.
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