Tectonic and eustatic control on Albian shallowing (Viking and Paddy Formations) in the Western Canada Foreland Basin

Abstract

Late Albian shallowing in the Viking and Paddy Formations is investigated using a dynamic forward model on two cross sections through the Western Canada Foreland Basin. The model incorporates flexural loading of the evolving Cordilleran fold-and-thrust belt, sea-level changes, cratonic tilt, and in-plane stress fluctuations. The stratigraphic observations are explained either by a rapid eustatic sea-level drop or by eastward tilting of the North American craton during late Albian times. In both cases, southward increases in the vertical growth rates of the adjacent accretionary wedge are implied. Differences between the predicted stratigraphic patterns in the upper Albian formations of the western and southern parts of the Western Canada Foreland Basin demonstrate the complications arising from local tectonics in determining eustatic sea-level fluctuations from sequence stratigraphy. The models also show that changes both in the magnitudes of intraplate stress and in continental tilt forces can produce intrabasinal highs like those underlying the upper Albian formations in the basin. Furthermore, sediment loading is demonstrated to affect the stratigraphic patterns in relation to the sedimentation rate and the rate of change of accumulation space.