This grid dataset is part of the 3D hydrostratigraphic model of the Calgary-Lethbridge Corridor (CLC), southwestern Alberta. The grid is a rendering of the thickness and distribution of sediment overlying the CLC bedrock topography.
The thickness and distribution of sediments overlying the bedrock surface in the CLC is highly varied, ranging from less than 1 m to as much as 160 m. These sediments include Neogene fluvial deposits, glacigenic materials deposited during Quaternary glaciation, as well as postglacial sediments.
This dataset supplements Alberta Geological Survey (AGS) Report 91 and INF 150, which include a full description of the process used to produce the sediment thickness grid.
17252 data points of varying quality and coverage were compiled for the construction of the CLC bedrock topography. The most significant data source was the extensive collection of well records compiled in the AWWID. The AWWID has abundant, relatively low quality data records, which include location inaccuracies resulting in numerous wells with the same location information. In cases of collocated data, where three or more wells with the same location information were encountered in the database, the deepest and shallowest well logs were selected to include wells that were completed in bedrock and to also characterize near surface sediments. The remaining duplicate wells were omitted.
The 17252 data points were used to model the CLC bedrock topography. The CLC sediment thickness grid was created by subtracting the CLC bedrock topography grid from the Sustainable Resource Development (SRD; 25 m cell-size) digital elevation model (DEM) (resampled to a 400 m grid cell size), which represents the present-day land surface.
All borehole data from the AWWID were sampled to the 25 m Provincial Digital Elevation Model (DEM) to provide a borehole top elevation (m asl) to correlate lithological descriptions between boreholes to create the CLC bedrock topography. This process was necessary as the borehole top elevation of AWWID water wells, in many cases, was not available/recorded or verified, and if reported was estimated from a topographic map, field investigation or handheld Global Positional System (GPS) device. Elevation values of moderate- and high-quality data from AGS boreholes and field sites, geophysical logs, and previously published geological and hydrogeological maps were also checked with the DEM to verify elevation accuracy and modified to match the DEM, if necessary.
The vertical accuracy of the 25 m DEM is stated as 5 m @ 90% in the CLC derived from 1:60 000 aerial photographs using photogrammetric methods.
This gridded dataset was derived by subtracting the computer-generated geostatistical model of the CLC Bedrock Topography from the Sustainable Resource Development (SRD; 25 m cell-size) digital elevation model (DEM) (resampled to a 400 m grid cell size), which represents the present-day land surface.
Data used to construct the CLC bedrock topography were derived from a variety of low- to high-quality borehole data, including lithologs submitted by water well contractors and compiled by the Alberta Water Well Information Database (AWWID), downhole geophysical logs collected from water wells, AGS borehole logs and field data; stratigraphic picks made from oil and gas geophysical logs by AGS geologists; contour data from the Bedrock Topography of Alberta; and the DEM, where known bedrock outcrop locations were made equal to the elevation value of the DEM.