LATE-GLACIAL ICE-SHEET PALEOHYDROLOGY OF SOUTHERN ALBERTA

Glacial lake sediments, eskers and meltwater channels are important indicators of past ice sheet hydrology. Although surficial geological mapping in southern Alberta has revealed the distribution of glacial landforms and sediments, little is known about their stratigraphic and geomorphic relationships. Eskers may or may not terminate in fans. Regionally, they exhibit a deranged pattern. Eskers are often found adjacent to, or within, meltwater channels interpreted to be subglacial (tunnel channels) and/or proglacial in origin. Lacustrine sediments, associated with eskers and meltwater channels, have also been interpreted as proglacial or subglacial in origin. These conflicting interpretations invoke different hydrological conditions and, therefore, radically different reconstructions of the late-glacial paleohydrology in the southwestern sector of the Laurentide Ice Sheet.

This study integrates empirical field (geomorphology and sedimentology) and digital (surficial and bedrock geology, DEMs) data to address the following questions. First, did the distribution of glacial lakes have an effect on esker distribution and pattern? Second, was esker distribution and pattern controlled by the presence of meltwater channels? Third, what was the relative timing of eskers, channels and lakes? Preliminary research indicates that: (i) long eskers occur in association with lake basins, short eskers occur on uplands, (ii) long eskers are located in broad, linear depressions and meltwater channels, (iii) short eskers contain highly-deformed sediment, long eskers do not, and (iv) extensive fan complexes, located where meltwater channels enter lake basins, are overlain and truncated by eskers. These initial results indicate that at least some meltwater channels and long eskers provided long-lived hydraulic connection between subglacial reservoirs and/or proglacial lakes, dammed by stagnant ice. In contrast, short upland eskers record short-lived R-channel drainage without hydraulic damming.