Clastic rocks, largely non-marine, of Upper Cretaceous age and some of Tertiary age underlie the plains in the Lethbridge-Fernie map area. The regional dip is westward, ranging from 20 to 200 feet per mile. Closely spaced, high-angle thrust faulting has deformed the Upper and Lower Cretaceous clastics of the foothills belt. Mesozoic clastics, Paleozoic carbonates, and Precambrian clastic and carbonate rocks in the mountain areas have been affected by low to moderate angle thrusting.
The interpretation of the hydrogeology has certain limitations due to the low reliability of data over large areas, thus yield values are based on a number of assumptions related to geology and topography. The highest expected well yields are to be found in present-day alluvial gravels and in sands and gravels of buried river valleys. Bedrock formations are expected to give generally very low to moderate yields, although there are some major exceptions.
Groundwater of over 1 000 ppm in total dissolved solids of either sodium sulfate or mixed cation sulfate-bicarbonate type is common over much of the plains part of the area, while better quality potable water of the calcium-magnesium bicarbonate type predominates in the foothills and mountain areas.
Tokarsky, O. (1974): Hydrogeology of the Lethbridge-Fernie area, Alberta; Alberta Research Council, ARC/AGS Earth Sciences Report 1974-01, 22 p.