A potential control on oil quality in the vicinity of the Athabasca oilsands is the introduction of freshwater and bacteria causing bio-degradation. Increased inputs of freshwater should lead to increased bio-degradation. The strength or weakness of aquitards along the flow path from surface to depth will be a controlling factor on how much freshwater and hence bio-degradation occurs. Hydrogeologic maps for nine Cretaceous and Devonian formations were created to assist in defining these degradation trends.