Abstract A study group of the Alberta Society of Petroleum Geologists proposed the following classification of Lower Cretaceous strata in the Peace River area of west-central Alberta: Fort St. John group Shaftesbury formation Peace River formation Paddy sandstone member Cadotte sandstone member Harmon shale member Spirit River formation Notikewin sandstone member Falher member Wilrich member Bluesky formation Bullhead group The Shaftesbury formation is a dark marine shale. The Peace River formation contains fairly distinct units consisting of the Paddy continental sandstone containing some coaly beds, the Cadotte glauconitic marine sandstone, and the Harmon dark marine shale. The Spirit River formation is a variable succession of sandstones and shales grouped into the Notikewin sandstone, the Falher sandstones, shales, siltstones, and thin coals, some beds suggesting deltaic origin, and the Wilrich dark shales with interbedded sandstones. The Bluesky formation consists of glauconitic sandstone grading down to dark shale. The Bullhead group is a variable succession of conglomerates, sandstones, shales, and coals.

Abstract Bluesky sandstones and shales occupy a transitional stratigraphic position between coastal plain sediments of the underlying Gething Formation and open marine shales of the Wilrich Member. The sedimentology and ichnology indicate that the Bluesky Formation in the Karr area consists of three subdivisions. The lower Bluesky preserves a disconformable ravinement surface formed by the initial transgression of the Moosebar sea over Gething coastal plain sediments. The middle Bluesky preserves shoreface to backshore facies within a high energy, northwest trending strand-plain that prograded into the Karr area from the west due to increased sediment supply. The upper Bluesky consists of a second disconformable ravinement surface, formed by renewed transgression as sediment supply diminished, overlain by shallow shelf sandstones and shales. A third transgressive ravinement surface occurs at the contact between upper Bluesky shallow shelf deposits and the Wilrich Member marine shale.