Characteristics of Limestone Solution in the Southern Rocky Mountains and Selkirk Mountains, Alberta and British Columbia

Abstract

The temperature, pH, and carbonate hardness of 415 water samples were determined in four limestone areas in the southern Rocky Mountains and Selkirk Mountains of Canada. Sampling covered all of the major carbonate rock formations of the region, ranged across the floral lifezones and included surface and sub-surface examples. In the forest zone at Crowsnest Pass, solute concentration in a major karst spring was inversely proportional to discharge; solute concentrations in a nearby creek and lake showed little variation with discharge. In tundra and alpine desert zones at Mt. Castleguard, solute concentrations were lower than in the forest, and marked depletion of PCO2 was indicated in some restricted cases. In the Maligne River basin, limestone forest and tundra waters were again contrasted. Solute concentrations in the trunk river and in lakes and underground channels along its course were determined by the mixing of karst and non-karst waters. At the Nakimu Caves there is a strong contrast between limestone seepage waters and allogenic streams.Karst waters of the region are classified as follows:(A) Above treeline: (i) tundra and some turbid glacial meltwaters—saturating with respect to calcite in the range 50–90 ppm CaCO3; (ii) snowmelt and some clear glacial meltwaters contacting bare limestone only—saturating with respect to calcite with <50 ppm CaCO3.(B) Below treeline: (i) holokarst groundwaters—saturating with 100–265 + ppm CaCO3; (ii) holokarst creek and lake waters—saturating with 100–140 ppm CaCO3; (iii) mixed waters from karst and non-karst terrains—with 35–90 ppm CaCO3.The forest waters compare with those from temperate and tropical forested karsts and indicate CO2 enrichment from soil air sources. The tundra waters are similar to those of the Alps and of an arctic tundra. Certain large cave streams remain very aggressive w.r.t. calcite after lengthy and rough passages through limestone. The ratio CaCO3:MgCO3 in most of the karst waters is close to 2.5:1.