Regional Stratigraphic Framework of Buffalo Head Hills-Peerless Lake Region, Northern Alberta

The Buffalo Head Hills-Peerless Lake (BHH-PL) region in northern Alberta is well known for its prolific oil and gas production. However, the discovery of kimberlites in the Buffalo Head Hills in early 1997 drew exploration attention to this region for diamonds. To date, 38 kimberlites have been discovered, with about 60% being diamond-bearing.

This study identifies and correlates 34 stratigraphic horizons from the Precambrian top to the ground surface in the BHH-PL region. Three regional cross-sections, four isopach maps of large sedimentary successions, and two structural maps of the Precambrian top contribute to understanding the stratigraphic framework of the region. As well, 15 lineaments have been inferred by this study; in general the lineaments trend north, northeast, northwest and east.

The overall Phanerozoic sedimentary cover is a southwest-thickening wedge. The basin-wide sub-Cretaceous unconformity separates the sedimentary bedrocks into two large intervals: 1) the Middle Devonian to Lower Mississippian succession, and 2) the upper Lower to lower Upper Cretaceous succession. Middle Devonian formations progressively onlap southwest onto the original Peace River Arch (PRA). During the Paleozoic, the BHH-PL region was a shallow shelf to basinal marine setting and dominated by carbonate, shale and evaporite deposits. The uppermost Devonian and Mississippian thicken southwestwardly and were eroded in the uplifted northeast. The Lower Cretaceous strata unconformably overlies Paleozoic formations. During Cretaceous time, the region became part of the Cordilleran foreland basin and was blanketed by marine shales with wedges of sand and silt deposits. Subsequently, the Upper Cretaceous formations were incised and eroded down to the Shaftesbury Formation in the Loon River lowland.

The BHH-PL region is floored by the Early Proterozoic Buffalo Head Domain and traversed by the long-acting PRA. The present PRA consists of a swarm of basement highs and lows with preferred orientations. Oil and gas pools are, in places, spatially distributed over the trend of some of the basement highs. This indicates that basement discontinuities in the region may have been reactivated, at times, during the Phanerozoic. The PRA and associated basement faults had a profound impact on the deposition and erosion of Phanerozoic sedimentary rocks, the distribution of oil and gas and, possibly, the emplacement of kimberlite pipes in the region.