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 b e divided into six facies associations. Facies association 1 contains a stack of regionally extensive, coarsening-upward shelf to lower shor eface mudstones, siltstones and sandstones that form a prograding para sequence set. These rocks are cut by a major incised valley. Facies as sociations 2 through 5 comprise the valley fill sediments at Sundance and Edson, and consist of estuarine sandstones, bioturbated muddy sand stones, fine grained sandstones, and crossbedded medium grained sandst ones. These sediments were deposited during two separate episodes of v alley filling superimposed on one major transgression. Both fills exhi bit the tripartite facies distribution characteristic of many modern w ave-dominated estuaries. Both fills are associated with transgressive shoreface deposits, fill 1 with the Wolf Creek shoreface, and fill 2 w ith the Bickerdike shoreface. The valley fill deposits are bounded by three transgressive surfaces of erosion (TSEs). The first underlies va lley fill 1, the second underlies valley fill 2, and the third truncat es the entire valley fill complex. Transgressive deposits of facies as sociation 6 blanket this third TSE. Each TSE represents a southward mo vement of the Viking shoreline during an overall transgression. The re gionally extensive deposits of facies association 1 are assigned to a Highstand Systems Tract, whereas the valley fill and transgressive fac ies are assigned to a Transgressive Systems Tract. Falling Stage and L owstand Systems Tract deposits are not preserved in this area.