BRINE DISCHARGE FROM THE WESTERN CANADA SEDIMENTARY BASIN-REFLUX OF SUBGLACIAL MELT WATER

Consistent with regional scale flow models, the up-dip edge of the Western Canada Sedimentary Basin is characterized by extensive discharge of brines along the outcrop belts of Paleozoic carbonates. Basin discharge occurs as seepage over broad areas as well as discrete spring outlets with up to 320 g/l total dissolved solids. Discharge is constrained by regional hydrogeological divides created by major river and lake systems. Na-Cl brine springs create large salt flats often characterized by extensive bacteria mats as well as precipitate mounds of halite (> 1m high during dry periods). Conservative ion ratios and stable isotope values are distinctly different from waters deeper in the basin, and suggest that the brine springs originate from dissolution of evaporite deposits by meteoric water. Oxygen and deuterium isotope values are significantly lower than modern precipitation and are interpreted to represent remnant Pleistocene melt water. Thus, rather then basin discharge, the brines are interpreted to be a reflux of subglacial meltwater injected into the basin during the Pleistocene, with salinity derived from dissolution of Devonian evaporite deposits.