The Zama Lake (NTS 84L) bedrock topography and drift thickness maps were completed as an Alberta Geological Survey and Geological Survey of Canada collaborative contribution to Northern Resources Development Project 4450, Shallow Gas and Diamond Opportunities in Northern Alberta and British Columbia 2003-2007, with funding support from the second phase of the Targeted Geoscience Initiative program. Petrophysical logs from oil and gas wells were the primary source of information used for constructing the bedrock topography. A suite of the common well logs (gamma, resistivity, spontaneous potential, density, neutron, sonic and caliper) were useful in making the pick for top of bedrock; however, the gamma and resistivity logs proved to be the most useful. In this region the drift typically displays a lower gamma response and higher resistivity response than the underlying bedrock. Other sources of data were drill cuttings, water well lithologs and surficial geological mapping that provided information on bedrock outcrop locations and till veneers over shallow bedrock (EUB/AGS Maps 315 and 316, GSC Open Files 4637 and 4754).
Mapping the bedrock surface was difficult in some areas where data were sparse. In many of the wells, log traces are not available for the upper part of the hole. The depth of surface casing set in bedrock provides a limit on the maximum possible drift thickness. Conversely, water wells and gas wells that did not intersect bedrock provide minimum drift thickness values. The bedrock topography contours were initially generated from bedrock surface picks using a computer-contouring program with subsequent modifications to better reflect the geological model.