Multiphase transgressive filling of an incised valley and shoreface complex, Viking Formation, Sundance-Edson area, Alberta

The Lower Cretaceous Viking Formation in the Sundance-Edson area can be divided into six facies associations. Facies association 1 contains a stack of regionally extensive, coarsening-upward shelf to lower shoreface mudstones, siltstones and sandstones that form a prograding parasequence set. These rocks are cut by a major incised valley. Facies associations 2 through 5 comprise the valley fill sediments at Sundance and Edson, and consist of estuarine sandstones, bioturbated muddy sandstones, fine grained sandstones, and crossbedded medium grained sandstones. These sediments were deposited during two separate episodes of valley filling superimposed on one major transgression. Both fills exhibit the tripartite facies distribution characteristic of many modern wave-dominated estuaries. Both fills are associated with transgressive shoreface deposits, fill 1 with the Wolf Creek shoreface, and fill 2 with the Bickerdike shoreface. The valley fill deposits are bounded by three transgressive surfaces of erosion (TSEs). The first underlies valley fill 1, the second underlies valley fill 2, and the third truncates the entire valley fill complex. Transgressive deposits of facies association 6 blanket this third TSE. Each TSE represents a southward movement of the Viking shoreline during an overall transgression. The regionally extensive deposits of facies association 1 are assigned to a Highstand Systems Tract, whereas the valley fill and transgressive facies are assigned to a Transgressive Systems Tract. Falling Stage and Lowstand Systems Tract deposits are not preserved in this area.