ABSTRACT: Geo hydrologic and thermometric observations in the vicinity of the Columbia Icefield, Alberta and British Columbia, Canada.

CGRG Bibliography of Canadian Geomorphology
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Abstract

The Columbia Icefield rests upon limestones containing natural caves that drain waters from the glacier sole. The principal cave is sealed at one end by an extrusion of glacier ice 300 m below the icefield surface. The hydrologic regime of the cave indicates that the modern icefield is temperate in character and that water is present at the glacier sole throughout the year. An interpretation of the air temperature pattern in the cave suggests that the geothermal flux to the glacier is only 10-40% of the expected value because heat is abstracted by melt water circulating through the rock. U, Th and O isotopic analyses of calcite speleothems further indicate that the base of the icefield has probably been during the Classical Wisconsinan - main Würm period. The inundation implies maintenance of a permanent water table at some hundreds of meters above the base in a valley glacier 750-800 m in depth. Specimen 73 010 displays equilibrium fractionation. it is considered that the d 180 variation probably represents a variation of temperature of approximately 5 deg, that is 2 deg warmer to 3 deg cooler than the present value of +3.5°C at the site. An increase of 2 deg in the mean annual external air temperature would not suffice alone to destroy the Columbia Icefield. Probably this persisted at approximately its modern dimensions during the period 155-93 ka. Three warm peaks and one cold trough occur in the 73 010 record. The peaks correlate well with d180 peaks that we have measured in specimens which grew at the same time in caves in Bermuda and Kentucky. There is also good agreement with the two older of the three raised coral reefs in Barbados taken to represent climatic optima during the Last Interglacial (Broecker & van Donk, 1970). This suggests that the deep cave speleothems of Castleguard Cave (and therefore the hydrogeothermal state there at a given time) record climatic events of greater than continental scale.

Bibliography of Canadian Geomorphology