Digital Data 2023-0014

This digital data package contains gridded datasets that provide information on the depth to bedrock (or sediment thickness) and the likelihood of coarse-grained deposits occurring within sediments above bedrock across Alberta. The datasets are the result of a three-dimensional machine learning model that uses compiled bedrock depth measurements and >320,000 lithologs and >5,700 field sites whose descriptions were codified into sand/gravel and clay categories.

Modelling was performed using a 500 m horizontal and 2.5 m vertical grid cell spacing. The likelihood of encountering coarse-grained deposits is represented by a raster dataset with 133 layers that are arranged in ascending order of depth beneath the ground surface, starting at 2.5 m beneath the ground surface and ranging to a maximum of the modelled depth to bedrock. Separate raster datasets are also provided to summarize: (a) the probability of encountering basal coarse-grained deposits in sediments at 2.5 m above the bedrock surface (termed basal sand probability); and (b) the average sand probability. The basal sand probability raster dataset can be used to identify the distribution of coarse-grained sediments that directly overlie bedrock units. The average sand probability raster dataset provides an overall estimate of the proportion of coarse-grained units within the Cenozoic succession of Alberta and can be considered as a relative estimate of overall ‘sandiness’. The depth to bedrock prediction and a spatial estimate of uncertainty derived from the width of the p90 to p10 prediction interval are included as additional raster datasets.

Place Keywords

Pawley, S.M., Utting, D.J., Hartman, G., and Liggett, J.E. (2023): Thickness of sediments above bedrock and three-dimensional distribution of coarse-grained deposits in Alberta (gridded data, GeoTIFF format); Alberta Energy Regulator / Alberta Geological Survey, AER/AGS Digital Data 2023-0014.