The drift thickness map shows the variation in thickness of unconsolidated sediment lying between the bedrock surface and the present-day land surface, and complements the Drift Thickness of Alberta map (Pawlowicz and Fenton, 1995). Throughout the map area drift covers the bedrock, with the exception of a few outcrops. The drift tends to be thin in the uplands, which generally correspond to elevated bedrock topography, and thick in areas where buried valleys are present. The bedrock topography map of the Zama Lake area shows the location of the major buried valleys (Figure 2; Pawlowicz et al., 2005). Drift is thinnest on the uplands of Rainbow Ridge, Bassett Hill, the Chinchaga Plain and the Rainbow Plain. In the buried valleys the drift thickens markedly. In Township 110, Range 3, west of the 6th Meridian drift thickness exceeds 300 m, filling a township-sized depression in the Zama Valley. The thickest drift in the map area, however, is found in the buried Rainbow Valley south of Bassett Hill in Township 105, Range 4, west of the 6th Meridian. The thick drift clearly shows the course of the Rainbow Valley from southeast to northwest. The land surface shows little evidence of these large drift-filled paleovalleys.
Pawlowicz, J.G., Fenton, M.M., Hickin, A.S., Nicoll, T.J., Paulen, R.C., Plouffe, A. and Smith, I.R. (2005): Drift thickness of Zama Lake area, Alberta (NTS 84L); Alberta Energy and Utilities Board, EUB/AGS Map 329