Quaternary stratigraphy and till geochemistry of the southern Buffalo Head Hills: results of an auger coring program

The Buffalo Head Hills are located in north-central Alberta, Canada. Since 1997, 38 kimberlite pipes have been discovered within the region. These kimberlites are in a region with highly variable drift thickness in which the Quaternary stratigraphy was poorly understood. In 2002, the Alberta Geological Survey cored nine holes near the K4 kimberlite to intersect the near-surface dispersion of kimberlitic material in the till and to document the glacial stratigraphy and drift thickness. Two additional auger holes were cored in the thicker drift to the west.

Two till units and intertill stratified sediments were identified while logging the core in the field. Samples of till, intertill stratified sediment and bedrock were analyzed for multi-element geochemistry (<0.063 mm fraction), matrix (<2 mm) texture and carbonate content (<0.063 mm). Results from these samples confirm the initial core logging observations that two distinct till units occur in the southern Buffalo Head Hills.

The upper till contains higher concentrations of CaO, MgO, fine matrix carbonate (both dolomite and calcite) and low TiO2 relative to the lower till. The upper till is thin in places (<3 m) and perhaps absent in BH02-10. This observation is similar to areas in the southern portion of the Buffalo Head Hills where an oxidized till exposed in a number of pits is within three to five metres of the surface.

The uppermost till was deposited by the Laurentide Ice Sheet during the Late Wisconsin glacial event. The lower till must have been deposited prior to a major nonglacial interval to have enough time to produce the weathering profile observed near the top of the lower till in hole BH02-11. Therefore, the lower till was likely deposited during the Early Wisconsin glaciation, or perhaps even earlier.