Lowstand shorefaces, transgressive incised shorefaces, and forced regressions: examples from the Viking Formation, Joarcam area, Alberta

In the Joarcam-Beaverhill Lake area of Alberta, there are three long (40 km), narrow (5 km) sandbodies in the late Albian Viking Formation. All three fields have recently been reinterpreted in the literature as lowstand shoreface deposits, but the order in which they formed remains controversial. Well log cross sections described here suggest that the Lindbrook shoreface was the first to form at a time of maximum lowstand of sea level. It was truncated as sea level began to rise, and the Lindbrook transgressive surface of erosion has been traced into the erosion surface that underlies Joarcam. Joarcam can therefore be interpreted as a shoreface incised during a pause in an overall transgression. Both the Lindbrook and Joarcam shorefaces appear to be truncated by the regressive surface of erosion that underlies Beaverhill Lake. This suggests that Beaverhill Lake is the youngest of the shorefaces and implies a second major fall of relative sea level. -from Authors