Sedimentology, ichnology, and development of a sub-regional depositional and stratigraphic framework for the McMurray-Wabiskaw succession in the MacKay River Area, northeastern Alberta

Abstract

The lower Cretaceous McMurray Formation is a prolific bitumen reservoir in the Athabasca Oil Sands deposit of northeastern Alberta. In the MacKay River area northwest of Fort McMurray, the depositional style, stratigraphy, and reservoir character differ from that of the traditional main valley trend. In this study, strata of the McMurray and overlying Clearwater Formation (Wabiskaw Member) was examined from 100 cored wells, and classified based on the sedimentological and ichnological character. This analysis identified that McMurray-Wabiskaw strata reflect a transition in depositional style from tide-dominated estuarine to shallow marine embayment. A network comprising thirteen cross-sections was also developed across the area, tied to cored intervals and wire-line log data. The complex stratigraphic relationships and stratigraphic surfaces were then examined within the McMurray-Wabiskaw succession. Overall, a third order depositional sequence was identified reflecting a major transgression and a starved sediment supply resulting in overall retrogradation, punctuated with episodes of progradation.