Now, if you were expecting me to follow up a post on the Belloy with one on the Montney, you will be disappointed. But it is not like there is a shortage of words dissecting the Montney these days, so I have leapfrogged over that part of the Peace River Arch stratigraphic column. This Petro Ninja – Enlighten Geoscience Well of the Week will focus on the Doig, a formation that is fascinating in its own right.
The first example of this allure is how the Doig can be a case study for understanding Sequence Stratigraphy. Aukes and Webb (1986) provide a starting point with their Core Conference paper on the Spirit River Pool. They demonstrate that the pool is better described as being of Doig age and the result of reservoir facies developed through a prograding tidal shoreline complex trapped by a subcrop against impermeable Charlie Lake evaporites rather than a “bar” (see below a cross section from their paper. The graphics are difficult to reproduce at a high resolution so I have included a link to their paper).
Stratigraphic Cross section across Spirit River Halfway Pool. After Aukes and Webb, 1986
Their model postulates that the Doig subcrop is sub-parallel to the shoreline trend. This implies that other pools will exist where the morphology of the subcrop intersects the paleoshoreline in a trapping fashion.
Schematic Map of Doig Formation (Aukes and Webb, 1986)
What is less explicit is the correlatability of the phosphate-rich offshore sections and how these parasequences can be traced to their shoreface equivalents. Updip Doig pools are, generally speaking, older, and downdip pools are younger. (Clarence Campbell and Frank Stoakes also deserve credit for this concept in unpublished course material).
This is where the fun really starts! The correlations can be challenging when traversing the Dawson Creek Graben Complex and the intervals attenuates but return to their previous expression after crossing over the northern flank.
Eventually you are over 175 km northwest at the Peejay “Halfway” Field in NEBC and realize that the Doig there looks very similar to the Spirit River Halfway Pool. Have a go at correlating them yourself and see if you think I’m right.
And that sets up a discussion on what is truly the Halfway in a WotW planned for a few weeks from now.
I would like to thank Peter Aukes for his assistance in the background for this article.
References
Aukes, P.G. and Webb, T.K. 1986. Triassic Spirit River Pool, northwestern Alberta. In: Canadian Society of Petroleum Geologists, 1986 Core Conference, Calgary, Alberta, Canada. N.C. Meijer Drees (ed.). p. 3.1-3.34.