Open File Report 1977-04

Open File Report 1977-04

OFR 1977-04

Surficial Geology of Potential Mining Areas in the Athabasca Oil Sands Region

Author(s) Kathol, C.P. McPherson, R.A. Date 1977-09-01

A surficial geology study of potential mining areas in the Athabasca oil sands region was undertaken by the Alberta Research Council in response to increasing demand for geologic information on deposits overlying the Athabasca Oil Sands.

The near surface bedrock in the study area includes the Devonian Waterways Formation (primarily carbonates), the Cretaceous McMurray Formation (oil impregnated sandstone), the Cretaceous Clearwater Formation (shale), the Grand Rapids Formation (sandstone) and younger undifferentiated Cretaceous units (shales).

The Waterways, McMurray, and Clearwater Formations form the surface bedrock in the Athabasca Lowlands and the Clearwater, Grand Rapids, and undifferentiated shales are found on major bedrock uplands. The basic configuration of the bedrock surface was established during preglacial times when rivers flowing northeastward from the Alberta Plains produced a series of drainage basins separated by major bedrock uplands, namely Birch Mountains, Thickwood Hills and Muskeg Mountain.

These large scale features of the bedrock surface are still reflected by the configuration of the present land surface. The top of the Waterways Formation is highly dissected by erosion and exhibits evidence of well developed karst topography. The surface of the over-lying bedrock units is considerably more uniform except in areas of extensive postglacial erosion.

Surficial deposits composed of preglacial, glacial and postglacial sediments completely cover the study area. They range in thickness from a few feet to over 450 feet on the slopes of Muskeg Mountain. Surface deposits and landforms resulting from glacial and postglacial deposition and erosion include till, glacio-fluvial, glacio-lacustrine, lacustrine, aeolian, alluvial and organic deposits and recent erosional features.

The surficial sediments have been subdivided into several stratigraphic units. These are in ascending order, preglacial gravels and sands, Saskatchewan gravels and sands, undifferentiated till and stratified sediments, unnamed till, Firebag till, lower stratified sediments, Fort Hills till, upper stratified sediments, meltwater channel sediments, and recent sediments.

The unnamed till has been identified on Thickwood Hills and on the Steepbank River. The Firebag till is known to underlie most of the study area and represents the last major glaciation in the region. The Fort Hills till occurs in the northern portion of the study area and is attributed to a local readvance of ice in the Athabasca valley. The till units are not correlated with tills found elsewhere in Western Canada because their age is uncertain. It is postulated that the Firebag and Fort Hills tills are Late Wisconsin in age.