WATERWAYS FORMATION: THE DEGREE OF BIOTIC INFLUENCE ON SEDIMENT PROPERTIES AND ITS IMPORTANCE IN OIL SANDS MINING

The Waterways Formation (Devonian; Givetian-Frasnian, Beaverhill Lake Group) forms the “underburden” of oil sands mining operations in northeastern Alberta. In the last few decades, this carbonate, shale, and evaporite succession has become critical to understanding potential environmental impacts of mining operations, not from the mining itself, but from geohazards below, in terms of faults, karst, and open joint systems. Thus, a thorough understanding of Waterways Formation properties – lithology, paleontology, and structure – are critical to mitigating and preventing environmental crises related to mining operations. Here, in a series of talks, we present the initial results of the lithological and paleontological aspects of the study.

The Waterways Formation outcrops in the lower four of its five members: the basal, shale-dominated Firebag Member (Givetian), the argillaceous carbonate Calumet Member (Frasnian), the Christina Member shale, and the lower portion of the Moberly Member argillaceous to “clean” carbonate. Of these, only the Christina Member is unfossiliferous.

Several distinct patterns can be traced through the Waterways Formation: 1. cyclicity in shale-carbonate successions, reflecting the interplay of sea level and the influx of terrigenous mud; 2. the general increase through time in skeletal allochems in the rock matrix, with a distinct increase in the upper Calumet and lower Moberly members; 3. the complexity of bioturbation fabric through time, which includes a general increase upsection in bioturbator diversity and the strong development of Thalassinoides burrow networks in the Moberly Member; and 4. the intermittent development of stromatoporoid biostromes in the Moberly Member.

These stratigraphic and rock properties not only influence fracture and karst patterns in the Waterways Formation, but also produced a feedback into the carbonate factory, as the following talks will reveal. The high-resolution investigation of rock and paleontological data through the Waterways Formation not only provides insight into the development of a carbonate factory through time, but also provides data useful to industry in understanding the oil sands “underburden.”