ABSTRACT

Field observations, combined with extensive core data and geophysical log signatures indicate that most of the McMurray Formation at the Syncrude open pit mine, in northeastern Alberta, consists of channel-fill deposits.

Body and trace fossils, clay mineralogy, and sedimentary textures and structures indicate an upward increase in marine influence within vertically stacked channel sequences of the McMurray Formation.

The lithologies of these channel fills are quite variable. Sand, an alternation of sand and mud, and mud-filled channels are equally abundant. However, there is growing evidence, indicative of the overall transgressive nature of the McMurray Formation, that the sand-filled and mud-filled channels are more common in the lower and upper sequences of the formation, respectively.

The cross-sectional geometry, geometry of the component beds, and grain size trends within the channel fills indicate that there were two types of channels: migrating (active), and stationary (passive). Published literature on the McMurray Formation has discussed the sedimentology of active-type channel deposits. This paper will share with the reader observations on the nature and sedimentation styles of both types of channel fill. Recognition of each channel type has a great impact on reservoir modelling of the McMurray Formation.

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