--> Sequence Stratigraphy and Controls of Barrier-Strandplain Systems in Falher Members A and B of the Lower Cretaceous Spirit River Formation, Northwestern Alberta, Canada, by R. G. Rouble and R. G. Walker; #90986 (1994).

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Abstract: Sequence Stratigraphy and Controls of Barrier-Strandplain Systems in Falher Members A and B of the Lower Cretaceous Spirit River Formation, Northwestern Alberta, Canada

Richard G. Rouble, R. G. Walker

Falher Members A and B of the Lower Cretaceous Spirit River Formation are major gas producers in northwestern Alberta with established gas reserves of 27.5 billion cu m. Previous work has interpreted each member as a prograding shoreface bounded by marine flooding surfaces. However, each member is split by a mudstone tongue at the seaward end. The mudstone tongues can be correlated with a sharp grain size change within each shoreface and with a flooding surface overlying a regional coal landward of the shoreface. This suggests that two shoreface sequences occur within each member, each deposited as a barrier-strandplain system.

The transgressive system tract is preserved as barrier sands, lagoonal and transgressive lag deposits partially preserved seaward of the barrier during shoreface retreat, and onlapping transgressive offshore storm deposits. The highstand system tract comprises a prograding strandplain formed of sandy and conglomeratic beach ridges, Backspit lagoons are locally encased in the shoreface sands. In most sequences, the beach conglomerate trends parallel to the barrier, on the seaward side.

The deposition of the Falher sequences was controlled by combined allocyclic and autocyclic processes. Each member was deposited in response to relative sea-level fluctuations superimposed on a tectonically subsiding Peace River Arch. However, the depositional characteristics of the transgressive system tract within the upper sequence in each member suggests that deposition was partly controlled by autocyclic processes involving river avulsion and delta lobe switching.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994