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Niagara
Issues - Artesian Systems http://www.mobot.org/plantscience/ResBot/niag/ |
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Niagara
Issues - Artesian Systems These pictures indicate
the soaking river bank beyond or downstream of the northern boundary of
Artpark. The green is predominantly the moss Didymodon tophaceus,
which covers the bank surface in year round moisture. During the course of
photosynthesis, carbon dioxide in solution is removed from groundwater
containing calcium bicarbonate ions. Insoluble calcium carbonate is
precipitated out and coats the lower portions of the plant stems, indurating
them. Through time the base of these plant populations resembles stone (tufa)
in which the original leaf stance and stem may be seen, as though fossilized.
When seepage turns to ice in winter, the ice may "pluck" the
soaking substrate from its place on the banks and in spring, during thaws,
the tufa mass tumbles down onto the shoreline below, or onto the talus
slopes. This moss is characteristic also of seepage on both sides of the
gorge, along its entire seven mile length where it develops primarily in
ledges and at the bases of the calcareous strata. Since the bedrock strata at
Artpark seem to be composed of shale, one may speculate that the calcareous
water originated from above the lake plain. Two other mosses also create tufa
in this way, Hymenostylium recurvirostrum, found mostly in the caprock
upstream, and Eucladium verticillatum, only one isolated station of
which was discovered at Niagara Glen, Ontario, in areas of late snow melt
near Niagara Glen.
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