The NSS Bulletin
- ISSN 1090-6924
Volume 41 Number 3: 53-65 - July 1979
A publication of the National Speleological Society
A Review of Alpine Karst
in the Southern Rocky Mountains of Canada
There is extensive karst development in Paleozoic carbonate and sulphate strata of the Front and Main ranges; southern Rocky Mountains of Canada. Its characteristics are summarized under six headings:
1) Lithology and structure. Karst is best developed in massively bedded middle Cambrian, upper Devonian, and Mississippian limestones. Parakarst occurs in thinner or more mixed limestone and dolomite units. Gypsum is karsted wherever it crops out. Because of high hydraulic gradient, aquicludes of shale, etc., may be breached at farourable locations.
2) Spatial and typological patterns of carbonate solution. Waters are of the bicarbonate type; measured CaCO3 hardness ranges from 10 to 275 mgl. Six classes are differentiated by hardness and by saturation characteristics-tundra and glacial meltwater, surface water below the treeline, karst springs, seepage waters in caves, regional rivers, and "depleted" waters, which are the only uniquely "alpine" type.
3) Groundwater systems and caves. Holokarst, fluviokarst, and nokarst drainage are found in similar lithologic and topographic settings. Topographic divides (including the Continental Divide) are frequently breached by groundwater drainage. Groundwater systems have no consistent relationship to geologic structure. The most common type of spring is young and hangs above the adjacent valley floor. Mature (cave) springs at base level are rare. Many spring sites have been aggraded by drift. Caves are prodominatly either of the deep-phreatic type (due to steep rock dip) or of the invasion vadose type. Shafts are common but are usually obstructed.
4) Karst groundwater systems and glacial hydrology. Karstic circulation may be suppressed or accelerated beneath temperate glaciers. Features indicating suppression (full-glacial conditions) are minor phreatic sollution of host rock, major re-solution of speleothems, and partial to complete filling with clastic debris. Features of acceleration (early- and late-glacial conditions) are rapid re-excavations, re-routing (via new invasion caves), and/or abandonment of caves.
5) Types of surface karst landforms. There are six ideal categories of alpine karst forms: a) prostglacial forms show no inherited glacial morphology, although their distribution may be determined by glacial factors; b) subglacial karst forms may be erosional (shafts) or depositional (precipitates); c) karstiglacial forms are karstic adaptations of glacial closed depressions in bedrock or in drift, d) glaciokarstic forms are karst features modified by glacial scour or deprosition; e) mixed forms display mingled glacial and karstic action from several different times; and f) preglacial forms are limited to abandoned and fragmented caves. In practice, it is difficult to discriminate categories 2 through 5, but Canadian examples are illustrated.
6) Altitudinal zonation of surface karst. Successively higher doline, karren, and frost shatter (periglacial) zones have been described from the Alps and other mountains. in the Canadian Rockies, a boreal zone, a tundra zone subjected to Wisconsinan glaciation, and a trundra zone that escaped Wisconsinan glaciation are recognized. Karst forms are limited in the boreal zone because of the depth of soil required to support forest. The glaciated tundra displays the greatest frequency and variety of karst; there is no sub-zonation of dolines and karren. Frost shatter dominates the unglaciated tundra. Solutional weathering seems often to be a necessary prerequisite to frost action on glacially scoured rock; therefore, care must be taken in attributing frost degradation of karst to climatic deterioration.
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17 June, 2002 11:54
Web Author: Jim Pisarowicz